Electrical Principles Jim Jenneson 7e - Test Bank

Electrical Principles Jim Jenneson 7e – Test Bank

 

Instant Download – Complete Test Bank With Answers

 

 

Sample Questions Are Posted Below

 

UEENEEG006A

Testbank

 

Multiple Choice Questions

1.	What is the name of the transformer winding that is connected to the electrical supply? A. The primary   B. The secondary   C. The tertiary   D. The armature

 

2.	What is the name of the transformer winding that is connected to the electrical load? A. The primary   B. The secondary   C. The tertiary   D. The armature

 

3.	Which of the following factors does NOT influence the arrangement of transformer windings? A. Core type   B. Intended use   C. Eddy currents   D. Supply frequency

 

4.	Why are transformer tanks usually painted in low-sheen variations of black, green or grey? A. To match supply authority corporate colours   B. To enable lower oil temperatures   C. To camouflage the transformers   D. To reduce iron losses

 

5.	Which of the following is not a type of transformer core? A. Winding   B. Core   C. Shell   D. Toroidal

 

6.	Which of the following transformer core types results in a shorter, constant cross-section magnetic path with very low flux leakage? A. Winding   B. Core   C. Shell   D. Toroidal

 

7.	What is the main benefit of using a cruciform transformer core? A. It is relatively inexpensive   B. It overcomes the tendency for unequal flux densities   C. Large cross-sectional area windings are wound onto a circular core   D. A number of different-sized laminations are required

 

8.	What is the principle upon which transformer operation is based? A. Lenz’s Law   B. Kirchoff’s Current Law   C. Ohm’s Law   D. Mutual induction

 

9.	What is the phase difference between the magnetising component of no-load current and the primary voltage? A. 0oE   B. 90oE leading   C. 90oE lagging   D. 180oE

 

10.	What is the phase difference between the energy component of no-load current and the primary voltage? A. 0oE   B. 90oE leading   C. 90oE lagging   D. 180oE

 

11.	What is the secondary voltage of a transformer that has 1000 primary turns and 100 secondary turns when it is connected to a 230 V supply? A. 2300 V   B. 230 V   C. 23 V   D. 2.3 V

 

12.	Flux leakage in a transformer core causes: A. increased terminal voltage   B. increased secondary current   C. increased inductive reactance   D. increased primary voltage

 

13.	What type of transformer is limited to a secondary voltage of ±25% of the primary voltage? A. An instrument transformer   B. An isolation transformer   C. An autotransformer   D. A high-reactance transformer

 

14.	What is the primary voltage of a transformer that has 250 primary turns and 50 secondary turns when a voltage of 12 V is measured across the secondary terminals? A. 60 V   B. 2.4 V   C. 24 V   D. 240 V

 

15.	Circulating currents in a transformer core are known as: A. hysteresis   B. reflected currents   C. Kirchoff currents   D. eddy currents

 

16.	Hysteresis and eddy current losses are collectively known as: A. copper losses   B. iron losses   C. variable losses   D. adjustable losses

 

17.	Ambient temperature has an effect on: A. induced magnetic flux   B. the magnetising component of no-load current   C. winding current rating   D. magnetic core selection

 

18.	Which of the following is not a suitable method for cooling transformers? A. Water cooling   B. Oil cooling   C. Air cooling   D. Forced circulation

 

19.	Which of the following methods can be used to circulate coolant around a large transformer tank? A. Induction   B. Radiation   C. Conduction   D. Convection

 

20.	Which of the following is NOT a requirement for connecting two transformers in parallel? A. Equal voltages   B. Same phase sequence   C. Opposite phase angle shift   D. Compatible internal impedance

 

21.	What must be done to reverse the direction of rotation of a three-phase induction motor? A. Swap two phase connections   B. Swap three line connections   C. Swap the rotor connections   D. Swap from star to delta connection

 

22.	What is the name given to the speed of a rotating magnetic field? A. Slip speed   B. Synchronic speed   C. Synchronous speed   D. Rotor speed

 

23.	What is the basis for a rotating magnetic field in a three-phase induction motor? A. Three out-of-balance stator windings   B. Three balanced stator windings   C. Three out-of-phase rotor windings   D. Three out-of-phase stator windings

 

24.	When is the rotor frequency of a three-phase induction motor at its maximum value? A. At rated speed   B. At 58% of rated current   C. At full load current   D. At standstill

 

25.	What is the percentage slip for a 2-pole three-phase induction motor, connected to a 50 Hz supply, when the rotor speed is 2900 RPM? A. 3.00%   B. 3.13%   C. 3.33%   D. 3.45%

 

26.	What is the rotor speed of a 4-pole three-phase induction motor when it is connected to a 50 Hz supply and it is operating at 6% slip? A. 0 RPM   B. 90 RPM   C. 1410 RPM   D. 1500 RPM

 

27.	What is the speed of the rotating magnetic field in a 4-pole machine that is connected to a 50 Hz supply? A. 500 RPM   B. 1000 RPM   C. 1500 RPM   D. 3000 RPM

 

28.

Torque in a three-phase induction motor is produced by: A. the interaction of the rotor field and the rotating magnetic field   B. the interaction of the stator field and the rotating magnetic field   C. the interaction of the separate stator winding magnetic fields   D. the interaction of the permanent field and the rotor magnetic field

 

29.	Which of the following parameters of a three-phase induction motor remains fairly constant from no-load to full-load operation? A. Percentage slip   B. Rotor current   C. Rotor magnetic flux   D. Stator magnetic flux

 

30.	What material is the stator core made from? A. Steel   B. Copper   C. Brass   D. Iron

 

31.	Where is the stator core located? A. On the armature   B. Outside the frame   C. Inside the frame   D. On the rotor

 

32.	Which type of rotor allows connection of external resistance to the rotor circuit during starting? A. Low-torque squirrel cage rotor   B. Double cage rotor   C. Wound rotor   D. High-resistance rotor

 

33.	What device is required to test for motor winding continuity? A. An ohmmeter   B. An insulation resistance tester   C. A voltmeter   D. An ammeter

 

34.	Which of the following tests is a suitable non-electrical test for finding a faulty coil group in a larger motor? A. Continuity test   B. Smell test   C. Rubbing the bindings   D. Tapping the windings with a small hammer

 

35.	Which of the following procedures should be done first when dismantling a three-phase induction motor? A. Re-grease the bearings   B. Add ‘witness marks’ to the end shields   C. Carefully withdraw the rotor   D. Continuity test the rotor

 

36.

What should be done with separate subassemblies when dismantling a three-phase induction motor? A. Store all subassemblies together so that nothing is misplaced   B. Store corresponding subassemblies from different motors together to allow comparison   C. Fully dismantle each subassembly and store all components together   D. Keep subassemblies separate from each other

 

37.

What is done to the added resistance of a wound-rotor induction motor during starting? A. As the slip speed decreases, the rotor resistance is increased   B. As the slip speed increases, the rotor resistance is increased   C. As the rotor speed increases, the rotor resistance is increased   D. As the rotor speed increases, the rotor resistance is decreased

 

38.	Which type of rotor gives a lower starting current but operates at a reduced speed? A. A low-torque squirrel cage rotor   B. A double cage rotor   C. A wound rotor   D. A high-resistance rotor

 

39.	Why are aluminium rotor bars physically larger than comparable copper rotor bars? A. To provide greater physical strength   B. Aluminium is less expensive than copper   C. Aluminium has a higher resistivity than copper   D. Aluminium is lighter than copper

 

40.	Adding resistance to the rotor circuit of a three-phase induction motor during starting: A. increases rotor reactance   B. increases the starting torque   C. increases the rotor frequency   D. increases the slip speed

 

41.

Which of the following factors is NOT a necessity for satisfactory operation of a three-phase induction motor? A. Three line voltages connected to the rotor windings   B. Three equal voltages at the correct phase displacement   C. Correctly connected stator windings   D. Three line voltages connected to the motor windings

 

42.	Which of the following is NOT an indication of motor overloading? A. Slower operating speed than normal   B. Lower operating temperature than normal   C. The varnish used on the windings start to smell   D. Smoke issuing from the windings

 

43.	Which of the following is a possible symptom of single phasing and phase reversal? A. Smoke issuing from the windings   B. Rumbling bearings   C. A low-pitched ‘growling’   D. A high-pitched ‘whine’

 

44.

If one phase winding of a three-phase induction motor is reversed: A. the three windings are at 120°E to each other   B. the motor will reach its breakdown torque too quickly   C. the motor will not draw enough current from the supply   D. the motor loses most of its torque and is often unable to start

 

45.	What is the name of the condition that occurs when one line of a three-phase supply is open circuited? A. Transposition   B. Phase reversal   C. Single phasing   D. Overloading

 

46.	Which of the following is NOT a characteristic of induction motors? A. Long brush life   B. Simplicity   C. Ruggedness   D. Reliability

 

47.	What causes a single-phase motor to draw a comparatively high no-load current? A. Low power factor   B. Negative torque   C. Low winding resistance   D. High slip speed

 

48.	What field pattern is produced by a split-phase motor? A. Circular   B. Cylindrical   C. Spherical   D. Elliptical

 

49.	What is a likely consequence if the centrifugal switch fails to operate? A. The motor will not start   B. The motor will not stop   C. The run winding will burn out   D. The start winding will burn out

 

50.	Why is the rotor field referred to as the cross field? A. It forms the shape of a cross   B. It is at right angles to the stator flux   C. It is due to Lenz’s Law   D. It stops the magnetic field rotation

 

51.	Why will the rotor in a split-phase motor rotate at a lower speed than the synchronous speed? A. Due to internal losses in the rotor   B. Due to design changes   C. Due to the reactance of the stator windings   D. Due to the influence of the cross field

 

52.	What is the major advantage of the capacitor-start motor over the split-phase induction motor? A. It is cheaper to manufacture   B. It is less complex   C. It has fewer components   D. It gives more starting torque

 

53.	Which of the following is a typical application for capacitor-start motors? A. Air compressors   B. Ceiling fans   C. Vacuum cleaners   D. Washing machines

 

54.	What is a primary consideration when selecting a capacitor for a capacitor-start motor? A. Avoiding resonance   B. Minimising reactance   C. Maximising power factor   D. Reducing starting current

 

55.	Which type of single-phase motor typically uses two capacitors? A. A permanently split capacitor motor   B. A capacitor-start, capacitor-run motor   C. A capacitor-start motor   D. A series universal motor

 

56.	Which of the following is a typical application for capacitor-start, capacitor-run motors? A. Washing machines   B. Ceiling fans   C. Vacuum cleaners   D. Air conditioners

 

57.	Which of the following is NOT an advantage of capacitor-start, capacitor-run motors in comparison with capacitor-start motors? A. Increased breakdown torque   B. Increased locked rotor torque   C. Reduced starting current   D. Reduced noise

 

58.	Which of the following is a typical application for permanently split capacitor motors? A. Washing machines   B. Fans   C. Vacuum cleaners   D. Air conditioners

 

59.	What are the names given to the two windings in permanently split capacitor motors? A. Start winding and run winding   B. Field winding and stator winding   C. Main winding and auxiliary winding   D. Auxiliary winding and armature

 

60.	Which type of single-phase motor has copper rings embedded into one side of each of its salient poles? A. Permanently split capacitor motor   B. Shaded pole motor   C. Capacitor-start motor   D. Series universal motor

 

61.	Which of the following is a typical application for shaded pole motors? A. Washing machines   B. Ceiling fans   C. Hair dryers   D. Air conditioners

 

62.	What effect does a shading ring have on the performance of a shaded pole motor? A. It shifts the magnetic axis across the pole face   B. It strengthens the cross field   C. It reduces hysteresis losses   D. It improves the power factor of the rotor current

 

63.	How is the direction of rotation reversed for a series universal motor? A. Reverse the supply connections   B. Reverse one pole winding connection   C. Reverse the armature in the enclosure   D. Reverse the armature connections

 

64.	Where are most motor protection devices designed to operate? A. Within the control circuit of the motor starter   B. At the main switchboard   C. In the motor supply conductors   D. Within the motor terminal box

 

65.	What must all electrical circuits be protected against? A. Mechanical overloads   B. Electrical overloads   C. Fault currents   D. Fault currents and overloads

 

66.	What is the effect of a sustained overload on an electric motor? A. Serious insulation failure   B. Reduced stator voltage   C. Increased running torque   D. Reduced mechanical load

 

67.	Which of the following devices is often included in a lightning protection system? A. A capacitor   B. A bimetal strip   C. A surge suppressor   D. A no-volt coil

 

68.

What effect does repetitive starting have on motor windings? A. Reduced starting torque due to voltage drop across the windings   B. Build-up of heat due to brief duration of starting current   C. Increased starting current due to decreased winding resistance   D. Improved power factor due to decreased winding reactance

 

69.

Why are PTC thermistors inadequate for protection against a locked rotor situation? A. The response time is too short   B. The response time is too long   C. The current-carrying capability of the PTC thermistors is too low   D. The control circuit for the PTC resistors does not respond to over-currents

 

70.

What is the operating mechanism for a typical reverse-phase sequence protection device? A. A bimetal strip that operates contacts in the control circuit   B. A current coil that operates contacts in the control circuit   C. A voltage relay that operates contacts in the control circuit   D. A mechanical vane that operates contacts in the control circuit

 

71.

How does standard motor design allow for short-time overloads? A. By connecting thermal overload protection in the starting circuit   B. By connecting magnetic over-current protection in the starting circuit   C. By having a normal running temperature that is well below the insulation rating   D. By having HRC fuses in series with the supply conductors at the switchboard

 

72.

What is the effect of high humidity on electric motors? A. Condensation inside the motor can deteriorate the motor’s condition   B. Moisture in the air allows the motor to operate at a lower temperature   C. The motor will require a lower starting torque due to reduced windage   D. The motor will operate at higher speed due to reduced air resistance

 

73.	What feature of an HRC fuse will quench any arc that develops? A. Eutectic bead   B. Powdered quartz   C. Restrictions in the silver element   D. Insulating tube

 

74.	What additional feature is required for a motor enclosure to be considered flameproof? A. Sealed gland   B. Weatherproof cable entry gland   C. Ducted cooling   D. Extra low-voltage operation

 

75.	How is cooling provided for a totally enclosed motor? A. Liquid coolant passes through a cooling jacket external to the motor   B. Ducted air flows through the motor case   C. An external fan blows air over cooling fins external to the motor   D. An internal fan circulates hydrogen inside the motor

 

76.

What is the operating characteristic for a PTC resistor? A. An increase in resistance causes an increase in temperature   B. An increase in resistance causes a decrease in temperature   C. An increase in temperature causes an increase in resistance   D. An increase in temperature causes a decrease in resistance

 

77.	What is the typical operating mechanism for an electronic overload device? A. A bimetal strip   B. A current transformer   C. A voltage transformer   D. An NTC thermistor

 

78.	Which device can provide protection if one supply line to a three-phase motor becomes open-circuited? A. A voltage-sensitive relay   B. A current-sensitive relay   C. A voltage transformer   D. A thermal overload

 

79.

What is the purpose of an eutectic bead in a high-rupturing capacity (HRC) fuse? A. To provide a good response to short-duration overload currents   B. To provide a good response to prolonged overload currents   C. To provide a good response to short-duration fault currents   D. To provide a good response to prolonged fault currents

 

80.

What causes a magnetically operated over-current relay to operate? A. The main body of the core is attracted to the armature when the coil current exceeds the preset value   B. The armature is attracted to the main body of the core when the coil current exceeds the preset value   C. The main body of the core is attracted to the armature whenever coil current flows   D. The armature is attracted to the main body of the core whenever coil current flows

 

81.	What is the name given to an electrical machine that is designed to operate at the same speed as the rotating magnetic field? A. A split-phase machine   B. An induction motor   C. A synchronous machine   D. A synchronised motor

 

82.	What are the typical connections for a large alternator? A. Three phase to the rotor and three-phase to the stator   B. d.c. to the rotor and three-phase to the stator   C. Three phase to the rotor and d.c. to the stator   D. Single phase to the rotor and three-phase to the stator

 

83.

Which of the following will occur if the load on a single alternator increases? A. The governor will open to increase the input power   B. The governor will close to increase the input power   C. The governor will open to decrease the input power   D. The governor will close to decrease the input power

 

84.

Which of the following will occur if the load on a single alternator increases? A. The voltage regulator will increase the field current to increase the output voltage   B. The voltage regulator will decrease the field current to increase the output voltage   C. The voltage regulator will increase the field current to maintain the output voltage   D. The voltage regulator will decrease the field current to decrease the output voltage

 

85.	What is the basic operating principle for a synchronous motor? A. Lenz’s Law   B. electromagnetic induction   C. the magnetic attraction between opposite poles   D. Ohm’s Law

 

86.	What is the name given to the positional difference between the rotor and the stator field of a synchronous motor? A. Slip   B. The torque angle   C. The phase angle   D. The armature reaction

 

87.

What is the effect of a change in the field excitation of a synchronous motor with a constant load? A. An increase in the field excitation causes a decrease in the line current at a lagging power factor   B. An increase in the field excitation causes an increase in the line current at a lagging power factor   C. An increase in the field excitation causes an increase in the line current at a leading power factor   D. An increase in the field excitation causes a decrease in the line current at a leading power factor

 

88.	What is a synchronous capacitor? A. An over-excited synchronous motor   B. An over-excited alternator   C. An under-excited synchronous motor   D. A synchronous motor operating at unity power factor

 

89.	What is the purpose of an auxiliary motor? A. It is a prime mover for an alternator   B. It provides the field excitation for a synchronous machine   C. It provides feedback to an automatic voltage regulator   D. It brings a synchronous motor up to speed

 

90.	Which of the following is a single-phase synchronous motor? A. A reticence motor   B. A reluctance motor   C. A hysterics motor   D. A shaded pole motor

 

91.	What causes the rotor of a reluctance motor to continue rotating when the stator flux is low? A. Interference   B. Induction   C. Impetus   D. Inertia

 

92.	What is a typical method for starting a reluctance motor? A. Use an auxiliary motor   B. Start as an induction motor   C. Start as a shaded pole motor   D. Use a different number of rotor poles compared with stator poles

 

93.	What is a typical method for starting a hysteresis motor? A. Use an auxiliary motor   B. Start as an induction motor   C. Start as a shaded pole motor   D. Use a different number of rotor poles compared with stator poles

 

94.	At what speed would the governor of an eight-pole diesel-driven alternator have to be set to enable a frequency of 60 Hz to be generated? A. 750 rpm   B. 900 rpm   C. 1500 rpm   D. 1800 rpm

 

95.	Which of the following is NOT a basic factor upon which alternators are rated? A. Power Factor   B. Frequency   C. Voltage   D. Current

 

96.	Which of the following would NOT be included in an equivalent circuit for a three-phase alternator? A. A resistor   B. An a.c. generating source   C. An inductor   D. A capacitor

 

97.	An increase in which of the following types of loads on a generator will cause the output voltage to increase? A. Lagging power factor   B. Unity power factor   C. Leading power factor   D. d.c. excitation

 

98.	An increase in which of the following types of loads on a generator will cause the rotor field to weaken? A. Lagging power factor   B. Unity power factor   C. Leading power factor   D. d.c. excitation

 

99.	What is the energy source for an uninterruptible power supplies (UPS) when it is supplying current to a load? A. Battery bank   B. Engine-driven alternator   C. Mains supply   D. Inverter

 

100.	Which type of standby power supply would be most suitable for maintaining supply to a computer system in an office environment? A. Diesel-engine-driven alternator   B. Unlimited power supply   C. Surge protection device   D. Uninterruptible power supply

 

UEENEEG006A Testbank Answer Key
 

Multiple Choice Questions

1.	What is the name of the transformer winding that is connected to the electrical supply? A. The primary   B. The secondary   C. The tertiary   D. The armature

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing application of transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

2.	What is the name of the transformer winding that is connected to the electrical load? A. The primary   B. The secondary   C. The tertiary   D. The armature

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing application of transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

3.	Which of the following factors does NOT influence the arrangement of transformer windings? A. Core type   B. Intended use   C. Eddy currents   D. Supply frequency

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing identification of different winding styles/types used in transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

4.	Why are transformer tanks usually painted in low-sheen variations of black, green or grey? A. To match supply authority corporate colours   B. To enable lower oil temperatures   C. To camouflage the transformers   D. To reduce iron losses

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing construction of transformer tanks for distribution transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

5.	Which of the following is not a type of transformer core? A. Winding   B. Core   C. Shell   D. Toroidal

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing types of lamination style and core construction used in single-phase, three-phase, double wound, auto transformers and instrument transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

6.	Which of the following transformer core types results in a shorter, constant cross-section magnetic path with very low flux leakage? A. Winding   B. Core   C. Shell   D. Toroidal

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing types of lamination style and core construction used in single-phase, three-phase, double wound, auto transformers and instrument transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

7.	What is the main benefit of using a cruciform transformer core? A. It is relatively inexpensive   B. It overcomes the tendency for unequal flux densities   C. Large cross-sectional area windings are wound onto a circular core   D. A number of different-sized laminations are required

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T1 Transformer construction, encompassing types of lamination style and core construction used in single-phase, three-phase, double wound, auto transformers and instrument transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

8.	What is the principle upon which transformer operation is based? A. Lenz’s Law   B. Kirchoff’s Current Law   C. Ohm’s Law   D. Mutual induction

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing principles of mutual induction of a transformer Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

9.	What is the phase difference between the magnetising component of no-load current and the primary voltage? A. 0oE   B. 90oE leading   C. 90oE lagging   D. 180oE

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing identification of voltage and current components of a phasor diagram for a transformer on no load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

10.	What is the phase difference between the energy component of no-load current and the primary voltage? A. 0oE   B. 90oE leading   C. 90oE lagging   D. 180oE

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing identification of voltage and current components of a phasor diagram for a transformer on no load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

11.	What is the secondary voltage of a transformer that has 1000 primary turns and 100 secondary turns when it is connected to a 230 V supply? A. 2300 V   B. 230 V   C. 23 V   D. 2.3 V

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing identification of voltage and current components of a phasor diagram for a transformer on no load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

12.	Flux leakage in a transformer core causes: A. increased terminal voltage   B. increased secondary current   C. increased inductive reactance   D. increased primary voltage

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing selecting transformers for specific application/s Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

13.	What type of transformer is limited to a secondary voltage of ±25% of the primary voltage? A. An instrument transformer   B. An isolation transformer   C. An autotransformer   D. A high-reactance transformer

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing selecting transformers for specific application/s Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

14.	What is the primary voltage of a transformer that has 250 primary turns and 50 secondary turns when a voltage of 12 V is measured across the secondary terminals? A. 60 V   B. 2.4 V   C. 24 V   D. 240 V

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T2 Transformer operation, encompassing identification of voltage and current components of a phasor diagram for a transformer on no load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

15.	Circulating currents in a transformer core are known as: A. hysteresis   B. reflected currents   C. Kirchoff currents   D. eddy currents

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T3 Transformer losses, efficiency and cooling, encompassing power losses which occur in a transformer Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

16.	Hysteresis and eddy current losses are collectively known as: A. copper losses   B. iron losses   C. variable losses   D. adjustable losses

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T3 Transformer losses, efficiency and cooling, encompassing power losses which occur in a transformer Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

17.	Ambient temperature has an effect on: A. induced magnetic flux   B. the magnetising component of no-load current   C. winding current rating   D. magnetic core selection

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T3 Transformer losses, efficiency and cooling, encompassing power losses which occur in a transformer Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

18.	Which of the following is not a suitable method for cooling transformers? A. Water cooling   B. Oil cooling   C. Air cooling   D. Forced circulation

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T3 Transformer losses, efficiency and cooling, encompassing methods used for natural and forced cooling of transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

19.	Which of the following methods can be used to circulate coolant around a large transformer tank? A. Induction   B. Radiation   C. Conduction   D. Convection

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T3 Transformer losses, efficiency and cooling, encompassing methods used for natural and forced cooling of transformers Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

20.	Which of the following is NOT a requirement for connecting two transformers in parallel? A. Equal voltages   B. Same phase sequence   C. Opposite phase angle shift   D. Compatible internal impedance

 

Topic: KS01-EG006A Single and three-phase transformers T-point: T5 Parallel operation of transformers and transformer auxiliary equipment, encompassing conditions/restrictions required before two transformers can be connected in parallel Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

21.	What must be done to reverse the direction of rotation of a three-phase induction motor? A. Swap two phase connections   B. Swap three line connections   C. Swap the rotor connections   D. Swap from star to delta connection

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing reversing the direction of rotation of a three-phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

22.	What is the name given to the speed of a rotating magnetic field? A. Slip speed   B. Synchronic speed   C. Synchronous speed   D. Rotor speed

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing speed of rotation of a rotating magnetic field Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

23.	What is the basis for a rotating magnetic field in a three-phase induction motor? A. Three out-of-balance stator windings   B. Three balanced stator windings   C. Three out-of-phase rotor windings   D. Three out-of-phase stator windings

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing characteristics of the magnetic field produced by a single-, two- and three-phase windings Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

24.	When is the rotor frequency of a three-phase induction motor at its maximum value? A. At rated speed   B. At 58% of rated current   C. At full load current   D. At standstill

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing relationship between the rotor speed, slip and rotor frequency Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

25.	What is the percentage slip for a 2-pole three-phase induction motor, connected to a 50 Hz supply, when the rotor speed is 2900 RPM? A. 3.00%   B. 3.13%   C. 3.33%   D. 3.45%

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing relationship between the rotor speed, slip and rotor frequency Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

26.	What is the rotor speed of a 4-pole three-phase induction motor when it is connected to a 50 Hz supply and it is operating at 6% slip? A. 0 RPM   B. 90 RPM   C. 1410 RPM   D. 1500 RPM

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing relationship between the rotor speed, slip and rotor frequency Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

27.	What is the speed of the rotating magnetic field in a 4-pole machine that is connected to a 50 Hz supply? A. 500 RPM   B. 1000 RPM   C. 1500 RPM   D. 3000 RPM

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing speed of rotation of a rotating magnetic field Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

28.

Torque in a three-phase induction motor is produced by: A. the interaction of the rotor field and the rotating magnetic field   B. the interaction of the stator field and the rotating magnetic field   C. the interaction of the separate stator winding magnetic fields   D. the interaction of the permanent field and the rotor magnetic field

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing basic principle of operation of an induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

29.	Which of the following parameters of a three-phase induction motor remains fairly constant from no-load to full-load operation? A. Percentage slip   B. Rotor current   C. Rotor magnetic flux   D. Stator magnetic flux

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T1 Operating principles of three-phase induction motors, encompassing basic principle of operation of an induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

30.	What material is the stator core made from? A. Steel   B. Copper   C. Brass   D. Iron

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing basic component parts of a three-phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

31.	Where is the stator core located? A. On the armature   B. Outside the frame   C. Inside the frame   D. On the rotor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing basic component parts of a three-phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

32.	Which type of rotor allows connection of external resistance to the rotor circuit during starting? A. Low-torque squirrel cage rotor   B. Double cage rotor   C. Wound rotor   D. High-resistance rotor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing types of rotors used in three-phase induction motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

33.	What device is required to test for motor winding continuity? A. An ohmmeter   B. An insulation resistance tester   C. A voltmeter   D. An ammeter

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing testing winding resistance (ohmic value and continuity) of a three-phase induction motor prior to connection to the supply Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

34.	Which of the following tests is a suitable non-electrical test for finding a faulty coil group in a larger motor? A. Continuity test   B. Smell test   C. Rubbing the bindings   D. Tapping the windings with a small hammer

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing testing winding resistance (ohmic value and continuity) of a three-phase induction motor prior to connection to the supply Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

35.	Which of the following procedures should be done first when dismantling a three-phase induction motor? A. Re-grease the bearings   B. Add ‘witness marks’ to the end shields   C. Carefully withdraw the rotor   D. Continuity test the rotor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing dismantling three-phase induction motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

36.

What should be done with separate subassemblies when dismantling a three-phase induction motor? A. Store all subassemblies together so that nothing is misplaced   B. Store corresponding subassemblies from different motors together to allow comparison   C. Fully dismantle each subassembly and store all components together   D. Keep subassemblies separate from each other

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T2 Three-phase induction motor construction, encompassing dismantling three-phase induction motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

37.

What is done to the added resistance of a wound-rotor induction motor during starting? A. As the slip speed decreases, the rotor resistance is increased   B. As the slip speed increases, the rotor resistance is increased   C. As the rotor speed increases, the rotor resistance is increased   D. As the rotor speed increases, the rotor resistance is decreased

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

38.	Which type of rotor gives a lower starting current but operates at a reduced speed? A. A low-torque squirrel cage rotor   B. A double cage rotor   C. A wound rotor   D. A high-resistance rotor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing squirrel cage motor operating characteristics conditions necessary for an induction motor to produce maximum torque Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

39.	Why are aluminium rotor bars physically larger than comparable copper rotor bars? A. To provide greater physical strength   B. Aluminium is less expensive than copper   C. Aluminium has a higher resistivity than copper   D. Aluminium is lighter than copper

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing squirrel cage motor operating characteristics conditions necessary for an induction motor to produce maximum torque Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

40.	Adding resistance to the rotor circuit of a three-phase induction motor during starting: A. increases rotor reactance   B. increases the starting torque   C. increases the rotor frequency   D. increases the slip speed

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing squirrel cage motor operating characteristics conditions necessary for an induction motor to produce maximum torque Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

41.

Which of the following factors is NOT a necessity for satisfactory operation of a three-phase induction motor? A. Three line voltages connected to the rotor windings   B. Three equal voltages at the correct phase displacement   C. Correctly connected stator windings   D. Three line voltages connected to the motor windings

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

42.	Which of the following is NOT an indication of motor overloading? A. Slower operating speed than normal   B. Lower operating temperature than normal   C. The varnish used on the windings start to smell   D. Smoke issuing from the windings

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

43.	Which of the following is a possible symptom of single phasing and phase reversal? A. Smoke issuing from the windings   B. Rumbling bearings   C. A low-pitched ‘growling’   D. A high-pitched ‘whine’

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

44.

If one phase winding of a three-phase induction motor is reversed: A. the three windings are at 120°E to each other   B. the motor will reach its breakdown torque too quickly   C. the motor will not draw enough current from the supply   D. the motor loses most of its torque and is often unable to start

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

45.	What is the name of the condition that occurs when one line of a three-phase supply is open circuited? A. Transposition   B. Phase reversal   C. Single phasing   D. Overloading

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T3 Three-phase induction motor characteristics, encompassing operating characteristics of an induction motor from name plate information and by measurement Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

46.	Which of the following is NOT a characteristic of induction motors? A. Long brush life   B. Simplicity   C. Ruggedness   D. Reliability

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing construction and basic characteristics of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

47.	What causes a single-phase motor to draw a comparatively high no-load current? A. Low power factor   B. Negative torque   C. Low winding resistance   D. High slip speed

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing principles of operation of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

48.	What field pattern is produced by a split-phase motor? A. Circular   B. Cylindrical   C. Spherical   D. Elliptical

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing principles of operation of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

49.	What is a likely consequence if the centrifugal switch fails to operate? A. The motor will not start   B. The motor will not stop   C. The run winding will burn out   D. The start winding will burn out

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing principles of operation of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

50.	Why is the rotor field referred to as the cross field? A. It forms the shape of a cross   B. It is at right angles to the stator flux   C. It is due to Lenz’s Law   D. It stops the magnetic field rotation

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing principles of operation of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

51.	Why will the rotor in a split-phase motor rotate at a lower speed than the synchronous speed? A. Due to internal losses in the rotor   B. Due to design changes   C. Due to the reactance of the stator windings   D. Due to the influence of the cross field

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T4 Single phase motors—split phase, encompassing principles of operation of a split phase induction motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

52.	What is the major advantage of the capacitor-start motor over the split-phase induction motor? A. It is cheaper to manufacture   B. It is less complex   C. It has fewer components   D. It gives more starting torque

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing identification of single phase induction motors including capacitor start, capacitor start/capacitor run, permanent split capacitor (PSC) and shaded pole Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

53.	Which of the following is a typical application for capacitor-start motors? A. Air compressors   B. Ceiling fans   C. Vacuum cleaners   D. Washing machines

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing operating characteristics and typical applications of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

54.	What is a primary consideration when selecting a capacitor for a capacitor-start motor? A. Avoiding resonance   B. Minimising reactance   C. Maximising power factor   D. Reducing starting current

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing principles of operation of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

55.	Which type of single-phase motor typically uses two capacitors? A. A permanently split capacitor motor   B. A capacitor-start, capacitor-run motor   C. A capacitor-start motor   D. A series universal motor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing principles of operation of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

56.	Which of the following is a typical application for capacitor-start, capacitor-run motors? A. Washing machines   B. Ceiling fans   C. Vacuum cleaners   D. Air conditioners

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing operating characteristics and typical applications of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

57.	Which of the following is NOT an advantage of capacitor-start, capacitor-run motors in comparison with capacitor-start motors? A. Increased breakdown torque   B. Increased locked rotor torque   C. Reduced starting current   D. Reduced noise

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing principles of operation of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

58.	Which of the following is a typical application for permanently split capacitor motors? A. Washing machines   B. Fans   C. Vacuum cleaners   D. Air conditioners

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing principles operating characteristics and typical applications of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

59.	What are the names given to the two windings in permanently split capacitor motors? A. Start winding and run winding   B. Field winding and stator winding   C. Main winding and auxiliary winding   D. Auxiliary winding and armature

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing identification of single phase induction motors including capacitor start, capacitor start/capacitor run, permanent split capacitor (PSC) and shaded pole Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

60.	Which type of single-phase motor has copper rings embedded into one side of each of its salient poles? A. Permanently split capacitor motor   B. Shaded pole motor   C. Capacitor-start motor   D. Series universal motor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing identification of single phase induction motors including capacitor start, capacitor start/capacitor run, permanent split capacitor (PSC) and shaded pole Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

61.	Which of the following is a typical application for shaded pole motors? A. Washing machines   B. Ceiling fans   C. Hair dryers   D. Air conditioners

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing operating characteristics and typical applications of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

62.	What effect does a shading ring have on the performance of a shaded pole motor? A. It shifts the magnetic axis across the pole face   B. It strengthens the cross field   C. It reduces hysteresis losses   D. It improves the power factor of the rotor current

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T5 Single phase motors—capacitor and shaded pole types, encompassing principles of operation of each motor type listed above Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

63.	How is the direction of rotation reversed for a series universal motor? A. Reverse the supply connections   B. Reverse one pole winding connection   C. Reverse the armature in the enclosure   D. Reverse the armature connections

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T6 Single phase motors—universal, encompassing principles of operation of a series universal motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

64.	Where are most motor protection devices designed to operate? A. Within the control circuit of the motor starter   B. At the main switchboard   C. In the motor supply conductors   D. Within the motor terminal box

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing reasons why motor protection is required Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

65.	What must all electrical circuits be protected against? A. Mechanical overloads   B. Electrical overloads   C. Fault currents   D. Fault currents and overloads

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing reasons why motor protection is required Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

66.	What is the effect of a sustained overload on an electric motor? A. Serious insulation failure   B. Reduced stator voltage   C. Increased running torque   D. Reduced mechanical load

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing types of motor overload protection Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

67.	Which of the following devices is often included in a lightning protection system? A. A capacitor   B. A bimetal strip   C. A surge suppressor   D. A no-volt coil

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing types of motor overload protection Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

68.

What effect does repetitive starting have on motor windings? A. Reduced starting torque due to voltage drop across the windings   B. Build-up of heat due to brief duration of starting current   C. Increased starting current due to decreased winding resistance   D. Improved power factor due to decreased winding reactance

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing effects of repetitive starting and/or reversing on motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

69.

Why are PTC thermistors inadequate for protection against a locked rotor situation? A. The response time is too short   B. The response time is too long   C. The current-carrying capability of the PTC thermistors is too low   D. The control circuit for the PTC resistors does not respond to over-currents

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing operating principles of microtherm devices, thermal and magnetic motor protection devices Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

70.

What is the operating mechanism for a typical reverse-phase sequence protection device? A. A bimetal strip that operates contacts in the control circuit   B. A current coil that operates contacts in the control circuit   C. A voltage relay that operates contacts in the control circuit   D. A mechanical vane that operates contacts in the control circuit

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing operating principles of phase failure protection Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

71.

How does standard motor design allow for short-time overloads? A. By connecting thermal overload protection in the starting circuit   B. By connecting magnetic over-current protection in the starting circuit   C. By having a normal running temperature that is well below the insulation rating   D. By having HRC fuses in series with the supply conductors at the switchboard

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing types of motor overload protection Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

72.

What is the effect of high humidity on electric motors? A. Condensation inside the motor can deteriorate the motor’s condition   B. Moisture in the air allows the motor to operate at a lower temperature   C. The motor will require a lower starting torque due to reduced windage   D. The motor will operate at higher speed due to reduced air resistance

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing special requirements for motor protection, in high humidity or moist environments, high temperature areas and corrosive atmospheres Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

73.	What feature of an HRC fuse will quench any arc that develops? A. Eutectic bead   B. Powdered quartz   C. Restrictions in the silver element   D. Insulating tube

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing electrical features of motor protection HRC fuses Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

74.	What additional feature is required for a motor enclosure to be considered flameproof? A. Sealed gland   B. Weatherproof cable entry gland   C. Ducted cooling   D. Extra low-voltage operation

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing special requirements for motor protection, in high humidity or moist environments, high temperature areas and corrosive atmospheres Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

75.	How is cooling provided for a totally enclosed motor? A. Liquid coolant passes through a cooling jacket external to the motor   B. Ducted air flows through the motor case   C. An external fan blows air over cooling fins external to the motor   D. An internal fan circulates hydrogen inside the motor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing special requirements for motor protection, in high humidity or moist environments, high temperature areas and corrosive atmospheres Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

76.

What is the operating characteristic for a PTC resistor? A. An increase in resistance causes an increase in temperature   B. An increase in resistance causes a decrease in temperature   C. An increase in temperature causes an increase in resistance   D. An increase in temperature causes a decrease in resistance

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing operating principles of microtherm devices, thermal and magnetic motor protection devices Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

77.	What is the typical operating mechanism for an electronic overload device? A. A bimetal strip   B. A current transformer   C. A voltage transformer   D. An NTC thermistor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing operating principles of microtherm devices, thermal and magnetic motor protection devices Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

78.	Which device can provide protection if one supply line to a three-phase motor becomes open-circuited? A. A voltage-sensitive relay   B. A current-sensitive relay   C. A voltage transformer   D. A thermal overload

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing operating principles of microtherm devices, thermal and magnetic motor protection devices Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

79.

What is the purpose of an eutectic bead in a high-rupturing capacity (HRC) fuse? A. To provide a good response to short-duration overload currents   B. To provide a good response to prolonged overload currents   C. To provide a good response to short-duration fault currents   D. To provide a good response to prolonged fault currents

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing electrical features of motor protection HRC fuses Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

80.

What causes a magnetically operated over-current relay to operate? A. The main body of the core is attracted to the armature when the coil current exceeds the preset value   B. The armature is attracted to the main body of the core when the coil current exceeds the preset value   C. The main body of the core is attracted to the armature whenever coil current flows   D. The armature is attracted to the main body of the core whenever coil current flows

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T7 Motor protection, encompassing selecting suitable protective devices for a given motor and starter combination Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

81.	What is the name given to an electrical machine that is designed to operate at the same speed as the rotating magnetic field? A. A split-phase machine   B. An induction motor   C. A synchronous machine   D. A synchronised motor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing principles of operation of a synchronous alternator Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

82.	What are the typical connections for a large alternator? A. Three phase to the rotor and three-phase to the stator   B. d.c. to the rotor and three-phase to the stator   C. Three phase to the rotor and d.c. to the stator   D. Single phase to the rotor and three-phase to the stator

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing identification of main parts of a synchronous alternator/motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

83.

Which of the following will occur if the load on a single alternator increases? A. The governor will open to increase the input power   B. The governor will close to increase the input power   C. The governor will open to decrease the input power   D. The governor will close to decrease the input power

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing advantages gained by the parallel operation of alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

84.

Which of the following will occur if the load on a single alternator increases? A. The voltage regulator will increase the field current to increase the output voltage   B. The voltage regulator will decrease the field current to increase the output voltage   C. The voltage regulator will increase the field current to maintain the output voltage   D. The voltage regulator will decrease the field current to decrease the output voltage

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing advantages gained by the parallel operation of alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

85.	What is the basic operating principle for a synchronous motor? A. Lenz’s Law   B. electromagnetic induction   C. the magnetic attraction between opposite poles   D. Ohm’s Law

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing principles of operation of a synchronous motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

86.	What is the name given to the positional difference between the rotor and the stator field of a synchronous motor? A. Slip   B. The torque angle   C. The phase angle   D. The armature reaction

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing principles of operation of a synchronous motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

87.

What is the effect of a change in the field excitation of a synchronous motor with a constant load? A. An increase in the field excitation causes a decrease in the line current at a lagging power factor   B. An increase in the field excitation causes an increase in the line current at a lagging power factor   C. An increase in the field excitation causes an increase in the line current at a leading power factor   D. An increase in the field excitation causes a decrease in the line current at a leading power factor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing methods used to provide the excitation of a synchronous alternator/motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

88.	What is a synchronous capacitor? A. An over-excited synchronous motor   B. An over-excited alternator   C. An under-excited synchronous motor   D. A synchronous motor operating at unity power factor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing methods used to provide the excitation of a synchronous alternator/motor Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

89.	What is the purpose of an auxiliary motor? A. It is a prime mover for an alternator   B. It provides the field excitation for a synchronous machine   C. It provides feedback to an automatic voltage regulator   D. It brings a synchronous motor up to speed

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing starting methods of synchronous motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

90.	Which of the following is a single-phase synchronous motor? A. A reticence motor   B. A reluctance motor   C. A hysterics motor   D. A shaded pole motor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing starting methods of synchronous motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

91.	What causes the rotor of a reluctance motor to continue rotating when the stator flux is low? A. Interference   B. Induction   C. Impetus   D. Inertia

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing starting methods of synchronous motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

92.	What is a typical method for starting a reluctance motor? A. Use an auxiliary motor   B. Start as an induction motor   C. Start as a shaded pole motor   D. Use a different number of rotor poles compared with stator poles

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing starting methods of synchronous motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

93.	What is a typical method for starting a hysteresis motor? A. Use an auxiliary motor   B. Start as an induction motor   C. Start as a shaded pole motor   D. Use a different number of rotor poles compared with stator poles

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T8 Three-phase synchronous machines—operation principles and construction, encompassing starting methods of synchronous motors Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

94.	At what speed would the governor of an eight-pole diesel-driven alternator have to be set to enable a frequency of 60 Hz to be generated? A. 750 rpm   B. 900 rpm   C. 1500 rpm   D. 1800 rpm

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing types of prime movers used with single and three-phase portable/standby alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

95.	Which of the following is NOT a basic factor upon which alternators are rated? A. Power Factor   B. Frequency   C. Voltage   D. Current

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing ratings of single and three-phase portable/standby alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

96.	Which of the following would NOT be included in an equivalent circuit for a three-phase alternator? A. A resistor   B. An a.c. generating source   C. An inductor   D. A capacitor

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing effects on generated voltage of variations in load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

97.	An increase in which of the following types of loads on a generator will cause the output voltage to increase? A. Lagging power factor   B. Unity power factor   C. Leading power factor   D. d.c. excitation

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing effects on generated voltage of variations in load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

98.	An increase in which of the following types of loads on a generator will cause the rotor field to weaken? A. Lagging power factor   B. Unity power factor   C. Leading power factor   D. d.c. excitation

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing effects on generated voltage of variations in load Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

99.	What is the energy source for an uninterruptible power supplies (UPS) when it is supplying current to a load? A. Battery bank   B. Engine-driven alternator   C. Mains supply   D. Inverter

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing applications of single and three-phase portable/standby alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines

 

100.	Which type of standby power supply would be most suitable for maintaining supply to a computer system in an office environment? A. Diesel-engine-driven alternator   B. Unlimited power supply   C. Surge protection device   D. Uninterruptible power supply

 

Topic: KS02-EG006A Alternating current rotating machines T-point: T9 Alternators and generators, encompassing applications of single and three-phase portable/standby alternators Unit of competency: UEENEEG006A Solve problems in single and three-phase low voltage machines