The reversal of an AC, three-phase, induction motor is accomplished by ______________. A. changing all three motor leads B. reversing the position of the slip rings C. interchanging any two of the three motor leads D. interchanging any two brushes

The reversal of an AC, three-phase, induction motor is accomplished by ______________. A. changing all three motor leads B. reversing the position of the slip rings C. interchanging any two of the three motor leads D. interchanging any two brushes
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Answer: C
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Which statement is true concerning a split-phase induction motor? A. Motor rotation can be reversed without changing the windings or leads. B. Motor speed can be readily adjusted from zero to full speed. C. The motor will run as a generator with the proper wiring. D. Motor rotation can be reversed by reversing the leads on the starting winding.

Description : Which statement is true concerning a split-phase induction motor? A. Motor rotation can be reversed without changing the windings or leads. B. Motor speed can be readily adjusted from zero to full ... proper wiring. D. Motor rotation can be reversed by reversing the leads on the starting winding.

Last Answer : Answer: D

The rotation of a three-phase induction motor can be reversed by _____________. A. interchanging any two of the three line leads to the stator B. disconnecting one of the three line leads to the stator C. switching the shunt field coil leads D. permanently disconnecting any two of the three line leads to the stator

Description : The rotation of a three-phase induction motor can be reversed by _____________. A. interchanging any two of the three line leads to the stator B. disconnecting one of the three line leads to the ... the shunt field coil leads D. permanently disconnecting any two of the three line leads to the stator

Last Answer : Answer: A

In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Description : In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Last Answer : Answer: C

What are the materials used to manufacture the brushes for slip rings of an induction motor?

Description : What are the materials used to manufacture the brushes for slip rings of an induction motor?

Last Answer : A:The slip rings are made of brass and phosphor bronze. The brushes are made of metal graphite which is an alloy of copper and carbon.

The speed of a synchronous motor is varied by _____________. A. interchanging any two of the three live leads B. changing the voltage of the system C. changing the input frequency D. increasing the field excitation

Description : The speed of a synchronous motor is varied by _____________. A. interchanging any two of the three live leads B. changing the voltage of the system C. changing the input frequency D. increasing the field excitation

Last Answer : Answer: C

In actual applications, electrical connections to 'R1-R2' of figure 'A' and to 'R1-R2- R3' of figure 'B' shown in the illustration are made by ______________. EL-0092 A. soldered contacts B. spliced and taped connections C. slip rings and brushes D. solderless crimp-on connectors

Description : In actual applications, electrical connections to 'R1-R2' of figure 'A' and to 'R1-R2- R3' of figure 'B' shown in the illustration are made by ______________. EL-0092 A. soldered contacts B. spliced and taped connections C. slip rings and brushes D. solderless crimp-on connectors

Last Answer : Answer: C

A three-phase, squirrel cage, induction motor will run hot due to _____________. A. open stator coils B. high power factor C. dirty or corroded slip rings D. reversed commutating poles

Description : A three-phase, squirrel cage, induction motor will run hot due to _____________. A. open stator coils B. high power factor C. dirty or corroded slip rings D. reversed commutating poles

Last Answer : Answer: A

Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one armature winding acted on by three identical but separate systems of rotating magnets. C. All three-phase alternators are designed to operate with a 0.8 leading power factor. D. The three phases always provide power to the load through three sets of slip rings and brushes.

Description : Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one ... The three phases always provide power to the load through three sets of slip rings and brushes.

Last Answer : Answer: A

Reversing any two of the three rotor leads on a wound-rotor induction motor will _____________. A. increase motor performance B. decrease motor performance C. reverse the motor rotation D. have no effect on the direction of rotation or motor performance

Description : Reversing any two of the three rotor leads on a wound-rotor induction motor will _____________. A. increase motor performance B. decrease motor performance C. reverse the motor rotation D. have no effect on the direction of rotation or motor performance

Last Answer : Answer: D

In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Description : In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Last Answer : Answer: A

Voltage generated by most AC generators is fed from the machine to the bus by means of ____________. A. brushes on a commutator B. brushes on slip rings C. slip rings on a commutator D. direct connections from the stator

Description : Voltage generated by most AC generators is fed from the machine to the bus by means of ____________. A. brushes on a commutator B. brushes on slip rings C. slip rings on a commutator D. direct connections from the stator

Last Answer : Answer: D

Routine maintenance of a ship's service alternator should include ______________. A. changing the pedestal bearing insulation yearly B. megger testing of all rectifying diodes C. lubricating excitation slip rings D. periodic cleaning of the air filters or screens

Description : Routine maintenance of a ship's service alternator should include ______________. A. changing the pedestal bearing insulation yearly B. megger testing of all rectifying diodes C. lubricating excitation slip rings D. periodic cleaning of the air filters or screens

Last Answer : Answer: D

A three-phase, squirrel cage, induction motor will run hot due to a/an ______________. A. improper brush position B. reversed commutating pole C. shorted stator D. high power factor

Description : A three-phase, squirrel cage, induction motor will run hot due to a/an ______________. A. improper brush position B. reversed commutating pole C. shorted stator D. high power factor

Last Answer : Answer: C

Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core

Description : Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core

Last Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES

The device in figure 'B' shown in the illustration can be used to control an AC load yet maintain its high gain by ______________. EL-0091 A. connecting the load to the output side of the bridge B. reversing the current flow through the control winding C. connecting the load to the input side of the bridge D. reversing the current flow through the bias winding

Description : The device in figure 'B' shown in the illustration can be used to control an AC load yet maintain its high gain by ______________. EL-0091 A. connecting the load to the output side of the ... connecting the load to the input side of the bridge D. reversing the current flow through the bias winding

Last Answer : Answer: C

Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel cage motor does not? A. Slip rings B. End rings C. A centrifugal switch D. End plates

Description : Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel cage motor does not? A. Slip rings B. End rings C. A centrifugal switch D. End plates

Last Answer : Answer: A

A 3-phase induction motor is running at slip ‘s’. If its two supply leads are interchanged, then the operating

Description : A 3-phase induction motor is running at slip ‘s’. If its two supply leads are interchanged, then the operating slip at that instant will be:

Last Answer : A 3-phase induction motor is running at slip ‘s’. If its two supply leads are interchanged, then the operating slip at that instant will be: (2-s)

An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure

Description : An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure

Last Answer : Answer: D

Which of the following statements represents the FIRST step in seating new brushes on slip rings? A. Wrap sandpaper around the slip rings and slide it back and forth between the brushes and the slip rings. B. Press the brushes against the slip ring with a wood block. C. Increase brush pressure and run at no load for 3 to 4 hours. D. Apply seating compound under the brushes and run at no load for 2 hours.

Description : Which of the following statements represents the FIRST step in seating new brushes on slip rings? A. Wrap sandpaper around the slip rings and slide it back and forth between the brushes and the slip rings. B. ... to 4 hours. D. Apply seating compound under the brushes and run at no load for 2 hours.

Last Answer : Answer: A

To properly seat the brushes on slip rings, you should use ____________. A. sand paper B. crocus cloth C. emery cloth D. all of the above

Description : To properly seat the brushes on slip rings, you should use ____________. A. sand paper B. crocus cloth C. emery cloth D. all of the above

Last Answer : Answer: A

Brushless generators are designed to operate without the use of ___________. A. brushes B. slip rings C. commutators D. all of the above

Description : Brushless generators are designed to operate without the use of ___________. A. brushes B. slip rings C. commutators D. all of the above

Last Answer : Answer: D

The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes.

Description : The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes.

Last Answer : (C) solid connections.

To reverse the direction of rotation of a three-phase AC induction motor, do one of the following: w) reverse any two of the three-phase connections x) change the frequency of the applied AC power y) operate the motor below the stall torque at very high slip z) none of the above

Description : To reverse the direction of rotation of a three-phase AC induction motor, do one of the following: w) reverse any two of the three-phase connections x) change the frequency of the applied AC power y) operate the motor below the stall torque at very high slip z) none of the above

Last Answer : ANSWER: W -- REVERSE ANY TWO OF THE THREE-PHASE CONNECTIONS 

A degree of control over the speed of a slip ring induction motor can be obtained by _____________. A. adjusting governor linkage B. changing the number of phases to the motor C. inserting resistance into the stator circuit D. inserting resistance into the rotor circuit

Description : A degree of control over the speed of a slip ring induction motor can be obtained by _____________. A. adjusting governor linkage B. changing the number of phases to the motor C. inserting resistance into the stator circuit D. inserting resistance into the rotor circuit

Last Answer : Answer: D

The advantage(s) of the method of D.C. motor speed control shown in the illustration is/are ______________. EL-0101 A. elimination of armature starting resistor losses B. elimination of speed instability with variable loads C. the ease of reversing motor direction D. all of the above

Description : The advantage(s) of the method of D.C. motor speed control shown in the illustration is/are ______________. EL-0101 A. elimination of armature starting resistor losses B. elimination of speed instability with variable loads C. the ease of reversing motor direction D. all of the above

Last Answer : Answer: D

As shown in the illustration, operating the reversing switch will change the polarity of the ______________. EL-0101 A. generator field B. generator armature C. motor armature D. all of the above

Description : As shown in the illustration, operating the reversing switch will change the polarity of the ______________. EL-0101 A. generator field B. generator armature C. motor armature D. all of the above

Last Answer : Answer: D

State the function of following parts of slip ring induction motor: (i) Slip ring (ii) Fan (iii) Brushes (iv) Frame

Description : State the function of following parts of slip ring induction motor: (i) Slip ring (ii) Fan (iii) Brushes (iv) Frame

Last Answer : Sr. No. Name of part Function 1 Slip ring 1) The rotor winding terminals are permanently connected to the slip rings. 2) Connects external resistance to rotor circuit through ... It provides mechanical support to the entire internal parts of motor. 2) Protects the inner parts.

A four pole, 60 Hz, three-phase synchronous motor comes up to 1760 RPM when started as an induction motor. What is the percent slip after the rotor field is energized? A. 0 B. 1.1 C. 2.2 D. 3.3

Description : A four pole, 60 Hz, three-phase synchronous motor comes up to 1760 RPM when started as an induction motor. What is the percent slip after the rotor field is energized? A. 0 B. 1.1 C. 2.2 D. 3.3

Last Answer : Answer: A

The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip increases, rotor reactance decreases. B. The pullout point on the torque curve is about seven times the normal full load torque value. C. At stand still, stator current is 150% of normal. D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Description : The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip ... D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Last Answer : Answer: D

A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m.

Description : A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m.

Last Answer : (D) 75 r.p.m.

Seating the brushes on a D.C. motor is first accomplished using ________________. A. a file for cutting the approximate curvature followed by sandpaper for the final fit B. sandpaper with the motor not operating and then a seating stone while running the machine C. emery paper for the initial cut and crocus cloth for the finishing cut D. course lapping compound, followed by a medium and then a fine grade

Description : Seating the brushes on a D.C. motor is first accomplished using ________________. A. a file for cutting the approximate curvature followed by sandpaper for the final fit B. sandpaper with the motor not ... for the finishing cut D. course lapping compound, followed by a medium and then a fine grade

Last Answer : Answer: B

If an AC generator experiences voltage failure, the cause may be _____________. A. an open in the field circuit B. the brushes shifting out of the neutral plane C. excessive locked-rotor current D. a rotating slip ring

Description : If an AC generator experiences voltage failure, the cause may be _____________. A. an open in the field circuit B. the brushes shifting out of the neutral plane C. excessive locked-rotor current D. a rotating slip ring

Last Answer : Answer: A

The speed of a three-phase squirrel-cage induction-type motor operating in a fixed frequency system is varied by changing the _____________. A. number of phases to the motor B. number of stator poles C. locked rotor current D. resistance of the rotor winding

Description : The speed of a three-phase squirrel-cage induction-type motor operating in a fixed frequency system is varied by changing the _____________. A. number of phases to the motor B. number of stator poles C. locked rotor current D. resistance of the rotor winding

Last Answer : Answer: B

A 3 phase 50 Hz induction motor has full load speed of 970 rpm. Calculate no of poles and slip frequency.

Description : A 3 phase 50 Hz induction motor has full load speed of 970 rpm. Calculate no of poles and slip frequency.

Last Answer : The number of poles in an induction motor can be calculated using the following formula: No. of poles = (120 * frequency) / speed In this case, the number of poles would be calculated as follows: No. of poles = ( ... ) - 50 Hz = 8.08 Hz So the motor has 6 poles and a slip frequency of 8.08 Hz.

A 400kW, 3-phase, 440V, 50Hz induction motor has a speed of 950 r.p.m. on fullload. The machine has 6 poles. The slip of the machine will be _______________. (A) 0.06 (B) 0.10 (C) 0.04 (D) 0.05

Description : A 400kW, 3-phase, 440V, 50Hz induction motor has a speed of 950 r.p.m. on fullload. The machine has 6 poles. The slip of the machine will be _______________. (A) 0.06 (B) 0.10 (C) 0.04 (D) 0.05

Last Answer : Ans: D N = Ns (1-S) 950 = 120 x 50 (1-S)/6 S = 0.05

The rotor power output of a 3-phase induction motor is 15 KW and corresponding slip is 4%. The rotor copper loss will be (A) 600 W. (B) 625 W (C) 650 W (D) 700 W

Description : The rotor power output of a 3-phase induction motor is 15 KW and corresponding slip is 4%. The rotor copper loss will be (A) 600 W. (B) 625 W (C) 650 W (D) 700 W

Last Answer : Ans: B Rotor copper losses = rotor input- rotor output and output = (1-s) input ∴ Input = output/(1-s) = 15000 /1-0.04 = 15625 ∴ loss = 15625 -1500 = 625 watt

A 3-phase, 400 votts, 50 Hz, 100 KW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of (A) 1500 rpm (B) 1470 rpm (C) 1530 rpm (D) 1570 rpm

Description : A 3-phase, 400 votts, 50 Hz, 100 KW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of (A) 1500 rpm (B) 1470 rpm (C) 1530 rpm (D) 1570 rpm

Last Answer : Ans: B N = NS (1-S) and NS =120 f / p =120 x 50 /4 = 1500 rpm ∴N= 1500 (1-0.02) =1470 rpm

The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be _________. (A) 1690 rpm (B) 1750 rpm (C) 1500 rpm (D) 1710 rpm

Description : The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be _________. (A) 1690 rpm (B) 1750 rpm (C) 1500 rpm (D) 1710 rpm

Last Answer : (D) 1710 rpm

The rotor frequency for a 3 phase 1000 RPM 6 pole induction motor with a slip of 0.04 is________Hz (A) 8 (B) 4 (C) 6 (D) 2

Description : The rotor frequency for a 3 phase 1000 RPM 6 pole induction motor with a slip of 0.04 is________Hz (A) 8 (B) 4 (C) 6 (D) 2

Last Answer : Ans: D Given: N=1000 rpm ; P= 6; s= 0.04; and f = NP/ 120 = 10006/120 = 50 Hz Rotor frequency fr=sf = 0.0450 = 2.0 Hz

State the function of following parts in Induction motor. (i) Stator (ii) Slip rings

Description : State the function of following parts in Induction motor. (i) Stator (ii) Slip rings

Last Answer : Name of part Function Stator 1) Stator frame supports the core, terminal box and protects the inner parts. 2) Stator core houses stator winding. 3) Stator winding ... ) Provides facility to connect external resistance to rotor circuit through brushes for starting and control.

The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open

Description : The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open circuited. The rotor is made to rotate at a speed of 600 rpm in the opposite direction to the ... frequency of induced voltage across slip ring is A) 30 Hz B) 70 Hz C) 20 Hz D) 35 Hz

Last Answer : The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open circuited. The rotor is made to rotate at a speed of 600 rpm in the opposite direction to the normal direction, The frequency of induced voltage across slip ring is 70 Hz

To check the three line fuses of a three-phase system consisting of a three-phase motor, you must _____________. A. place the starter in the 'stop' position B. make sure the motor is operating at full load to guard against a false reading C. place the leads across the 'hot' ends of the fuses D. place the leads across the bottom ends of the fuses

Description : To check the three line fuses of a three-phase system consisting of a three-phase motor, you must _____________. A. place the starter in the 'stop' position B. make sure the motor is operating at full ... leads across the 'hot' ends of the fuses D. place the leads across the bottom ends of the fuses

Last Answer : Answer: A

Erratic operation of the devices represented in the diagrams shown in the illustration could be traced to ____________. EL-0092 A. improper contact at 'R' slip rings or 'S' connections B. a low three-phase voltage supply C. improper contact at 'S' slip rings or 'R' connections D. a high three-phase voltage supply

Description : Erratic operation of the devices represented in the diagrams shown in the illustration could be traced to ____________. EL-0092 A. improper contact at 'R' slip rings or 'S' connections B. a low three- ... . improper contact at 'S' slip rings or 'R' connections D. a high three-phase voltage supply

Last Answer : Answer: A

In the illustrated ground detection system with a ground on phase A, if the switch is opened __________. EL-0009 A. lamp A will dim or go out depending on the severity of the ground B. all three lamps will return to their normal brightness indicating that the bulbs are not burnt out C. lamps B and C will dim lamp A will be brighter D. lamp A will start flickering if the ground is in an AC induction motor

Description : In the illustrated ground detection system with a ground on phase A, if the switch is opened __________. EL-0009 A. lamp A will dim or go out depending on the severity of the ground B. all three ... lamp A will be brighter D. lamp A will start flickering if the ground is in an AC induction motor

Last Answer : Answer: B

The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the windings when the machine is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Description : The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the ... is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Last Answer : Answer: B

An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. cause the slip rings to melt C. cause a low voltage differential to develop between the armature and the bus D. cause high currents to be induced in the field windings

Description : An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. ... between the armature and the bus D. cause high currents to be induced in the field windings

Last Answer : Answer: D

The main purpose of an electric space heater installed in a large AC generator is to _____________. A. prevent the windings from becoming brittle B. prevent moisture from condensing in the windings during shutdown C. prevent acidic pitting of the slip rings D. keep the lube oil warm for quick starting

Description : The main purpose of an electric space heater installed in a large AC generator is to _____________. A. prevent the windings from becoming brittle B. prevent moisture from condensing in the windings during ... C. prevent acidic pitting of the slip rings D. keep the lube oil warm for quick starting

Last Answer : Answer: B

The direction of rotation of a DC propulsion motor can be changed by reversing the _____________. A. brush holder position B. polarity of the field poles C. brush staggered order D. motor interpole connections

Description : The direction of rotation of a DC propulsion motor can be changed by reversing the _____________. A. brush holder position B. polarity of the field poles C. brush staggered order D. motor interpole connections

Last Answer : Answer: B