An unsaturated dc shunt motor runs at its rated speed when rated voltage is applied to it. If the

An unsaturated dc shunt motor runs at its rated speed when rated voltage is applied to it. If the supply voltage to the motor is reduced by 25%, the speed of the motor 

(a) Increases by 25% (b) Remains the same (c) Decreases by 25% (d) Decrease only slightly by an amount less than 25% 
by

1 Answer

Answer :

An unsaturated dc shunt motor runs at its rated speed when rated voltage is applied to it. If the supply voltage to the motor is reduced by 25%, the speed of the motor Remains the same

by

Related questions

One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for polarity using a/an ____________. A. iron bar across each field B. magnetic compass placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections

Description : One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for ... placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections

Last Answer : Answer: B

A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s.

Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Last Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load, armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full load speed in r.p.m. is (A) 1080 (B) 1203 (C) 1000 (D) 1200

Description : A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load, armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full load speed in r.p.m. is (A) 1080 (B) 1203 (C) 1000 (D) 1200

Last Answer : (A) 1080

When 220V dc shunt alternator generating the voltage at rated value. If direction of rotation is reversed, then alternator will a) Build up its voltage with same polarity b) Build up its voltage with opposite polarity c) No build up of voltage d) None

Description : When 220V dc shunt alternator generating the voltage at rated value. If direction of rotation is reversed, then alternator will a) Build up its voltage with same polarity b) Build up its voltage with opposite polarity c) No build up of voltage d) None

Last Answer : Ans: No build up of voltage

A DC shunt motor has rated rpm of 480. Certain industrial application requires this motor to run at 540 rpm

Description : A DC shunt motor has rated rpm of 480. Certain industrial application requires this motor to run at 540 rpm for some time. Which speed control will be desirable? A) Ward Leonard control B) Armature ... ) Field resistance control D) It is not possible to run the motor at more than the rated rpm 

Last Answer : A DC shunt motor has rated rpm of 480. Certain industrial application requires this motor to run at 540 rpm for some time. Which speed control will be desirable? A) Ward Leonard control B) Armature ... Field resistance control D) It is not possible to run the motor at more than the rated rpm 

If a DC motor runs hot, the cause may be _____________. A. high mica condition B. low ambient temperature C. clogged ventilation ducts D. an open in the shunt field

Description : If a DC motor runs hot, the cause may be _____________. A. high mica condition B. low ambient temperature C. clogged ventilation ducts D. an open in the shunt field

Last Answer : Answer: C

If a DC motor runs faster than designed, with all other conditions being normal, the possible cause could be a/an ______________. A. shorted shunt field coil B. open armature coil C. reversed commutating pole D. overload

Description : If a DC motor runs faster than designed, with all other conditions being normal, the possible cause could be a/an ______________. A. shorted shunt field coil B. open armature coil C. reversed commutating pole D. overload

Last Answer : Answer: A

A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be (A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm.

Description : A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of ... . (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm.

Last Answer : (C) less than 800 rpm.

A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven

Description : A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven  (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control, the respective output powers ... kW in (i) and 75 kW in (ii) (D) 50 kW in (i) and 50 kW in (ii)

Last Answer : A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven  (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control, the respective output ... kW in (i) and 75 kW in (ii) (D) 50 kW in (i) and 50 kW in (ii)

A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Description : A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

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.

Regenerative braking (A) Can be used for stopping a motor. (B) Cannot be easily applied to DC series motors. (C) Can be easily applied to DC shunt motors (D) Cannot be used when motor load has overhauling characteristics.

Description : Regenerative braking (A) Can be used for stopping a motor. (B) Cannot be easily applied to DC series motors. (C) Can be easily applied to DC shunt motors (D) Cannot be used when motor load has overhauling characteristics.

Last Answer : Ans: B Because reversal of Ia would also mean reversal of field and hence of Eb

The speed of a d.c. shunt motor at no-load is (A) 5 to 10% (B) 15 to 20% (C) 25 to 30% (D) 35 to 40% higher than its speed at rated load.

Description : The speed of a d.c. shunt motor at no-load is (A) 5 to 10% (B) 15 to 20% (C) 25 to 30% (D) 35 to 40% higher than its speed at rated load.

Last Answer : (A) 5 to 10%

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is?

Last Answer : The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across each field coil C. using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter

Description : A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across ... using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter

Last Answer : Answer: B

The torque produced by a motor when its shaft will not turn, even though rated voltage is applied to the stator, is known as _____________. A. locked-rotor torque B. pullout torque C. breakdown torque D. torque margin

Description : The torque produced by a motor when its shaft will not turn, even though rated voltage is applied to the stator, is known as _____________. A. locked-rotor torque B. pullout torque C. breakdown torque D. torque margin

Last Answer : Answer: A

Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Description : Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Last Answer : Answer: Speed Control of DC shunt motor can be possible by providing resistance in the armature and field circuits and varying the resistors speed changes can be carried out over a wide range. ... employed. Care should be taken that in the process efficiency and power factor should be maintained.

Give two basic speed control scheme of DC shunt motor?

Description : Give two basic speed control scheme of DC shunt motor?

Last Answer : Answer: 1. By using flux control method: in this method a rheostat is connected across the field wdg to control the field current. So by changing the current the flux produced by the field wdg can ... ) can be varied, and since speed is directly proportional to Eb-IaRa the speed can be controlled.

The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. (A) universal (B) synchronous (C) DC shunt (D) two-phase

Description : The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. (A) universal (B) synchronous (C) DC shunt (D) two-phase

Last Answer : Ans: A Universal motor has same characteristics as DC series motor and also known as an a.c series motor.

A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? (A) 100 Volts. (B) 0.1 Volts. (C) 1 Volts. (D) 10 Volts.

Description : A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? (A) 100 Volts. (B) 0.1 Volts. (C) 1 Volts. (D) 10 Volts.

Last Answer : Ans: D Given N = 1500 rpm, Φ = 0.4 mWb, Z = 1000, P = 4, & A= 4 Therefore, Eb = NΦPZ / 60 A = 1500 x 0.4 x 4 x 1000 x 10^-3 / 60 x 4 = 60/6 = 10 volts

If field current is decreased in shunt dc motor, the speed of the motor

Description : If field current is decreased in shunt dc motor, the speed of the motor (a) remains same. (b) increases. (c) decreases. (d) none of the above.

Last Answer : increases

Why does the speed of a DC shunt motor decrease as the load increases?

Description : Why does the speed of a DC shunt motor decrease as the load increases?

Last Answer : Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.

Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method...

Description : Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method due to:  (1) Better speed regulation (2) Less loss in external resistance (3) Simplicity in control circuit (4) Reduced cost of controller

Last Answer : Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method due to: Better speed regulation.

The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Description : The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Last Answer : Answer: A

The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Description : The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Last Answer : Answer: B

A dc cumulatively compounded motor delivers rated load torque at rated speed. If series field is short circuited, then the armature current and speed will a) Both increases b) Both decreases c) Increases and decreases d) Decreases and increases

Description : A dc cumulatively compounded motor delivers rated load torque at rated speed. If series field is short circuited, then the armature current and speed will a) Both increases b) Both decreases c) Increases and decreases d) Decreases and increases

Last Answer : Ans: Both increases

A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated

Description : A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to  (A) 0.75 p.u (B) 0.5 p.u (C) 0.25 p.u (D) 0.125 p.u

Last Answer : A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to 0.5 p.u

A cumulative dc compound motor runs at 1500 rpm. on full load. If its series field is short-circuited, its speed

Description : A cumulative dc compound motor runs at 1500 rpm. on full load. If its series field is short-circuited, its speed  (1) becomes zero (2) remains unchanged (3) increases (4) decreases

Last Answer : Increases. As it's cumulative compound motor, both series and shunt field both assist each other. If series field is short circuited, the overall field strength will decrease and atop of that ... speed is inversely proportional to field strength.  So, the speed will increase overall.

An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from _____________. A. one line terminal to each coil lead in succession B. one field coil to each adjacent field coil in turn C. any suitable ground to any available line lead D. any field pole to each field coil lead

Description : An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from ... C. any suitable ground to any available line lead D. any field pole to each field coil lead

Last Answer : Answer: A

If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase

Description : If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase

Last Answer : Answer: D

The full load torque of an electric motor is the __________. A. minimum torque developed by the motor accelerating from stop to full speed B. turning moment exerted by the motor at rated load and speed C. maximum torque developed by the motor with rated voltage and frequency D. turning moment exerted by the motor from any rotor angular position at any load

Description : The full load torque of an electric motor is the __________. A. minimum torque developed by the motor accelerating from stop to full speed B. turning moment exerted by the motor at rated load ... and frequency D. turning moment exerted by the motor from any rotor angular position at any load

Last Answer : Answer: B

belt of silk runs over two metal pulleys, one of which is surrounded by a hollow metal sphere. Two electrodes, in the form of comb-shaped rows of sharp metal points, are positioned respectively near to the bottom of the lower pulley and inside the sphere, over the upper pulley. The top electrode is connected to the sphere and the bottom one to the ground. A high DC potential is applied to the upper pulley. A simple version of which equipment is being described here?

Description : belt of silk runs over two metal pulleys, one of which is surrounded by a hollow metal sphere. Two electrodes, in the form of comb-shaped rows of sharp metal points, are positioned ... potential is applied to the upper pulley. A simple version of which equipment is being described here?

Last Answer : Van de Graaff generator.

As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively ____________ at the start. (A) Lower armature resistance. (B) Stronger series field. (C) Fewer series turns. (D) Larger armature current.

Description : As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively ____________ at the start. (A) Lower armature resistance. (B) Stronger series field. (C) Fewer series turns. (D) Larger armature current.

Last Answer : (D) Larger armature current.

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Last Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt field coil before testing C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing

Description : When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt ... C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing

Last Answer : Answer: B

Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer

Description : Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer

Last Answer : Answer: D

An open armature connection in a DC propulsion motor could be caused by ____________. A. low-load operation B. clogged ventilation ducts C. sparking at the brushes D. a grounded shunt field coil

Description : An open armature connection in a DC propulsion motor could be caused by ____________. A. low-load operation B. clogged ventilation ducts C. sparking at the brushes D. a grounded shunt field coil

Last Answer : Answer: B

The torque, in a _____________is proportional to the square of the armature current (A) DC shunt motor (B) stepper motor (C) 2-phase servomotor (D) DC series motor

Description : The torque, in a _____________is proportional to the square of the armature current (A) DC shunt motor (B) stepper motor (C) 2-phase servomotor (D) DC series motor

Last Answer : (D) DC series motor

The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor.

Description : The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor.

Last Answer : (B) a dc shunt motor.

A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor.

Description : A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor.

Last Answer : (C) synchronous motor.

DC shunt motor

Description : DC shunt motor

Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

State any four applications of DC shunt motor.

Description : State any four applications of DC shunt motor.

Last Answer : Applications of DC shunt motor: 1) Lathe machines 2) drilling machines 3) milling machines 4) Printing machinery 5) Paper industry 6) centrifugal and reciprocating pumps 7) blowers 8)fans

Why shouldn’t a DC shunt motor start on the heavy load setting?

Description : Why shouldn’t a DC shunt motor start on the heavy load setting?

Last Answer : A series motor never started at no load and a shunt motor is never started at on load.

What will happen when a DC shunt motor is started with a load?

Description : What will happen when a DC shunt motor is started with a load?

Last Answer : Starting current will be very high so motor will take more current from supply. It may damage the armature winding.

To conduct load test on a dc shunt motor, it is coupled to a generator which is identical to the motor. The field

Description : To conduct load test on a dc shunt motor, it is coupled to a generator which is identical to the motor. The field of the generator is also connected to the same supply source as the motor. The armature of generator is ... value of this load resistance is  (A) 1.0 (B) 0.98 (C) 0.96 (D) 0.94

Last Answer : To conduct load test on a dc shunt motor, it is coupled to a generator which is identical to the motor. The field of the generator is also connected to the same supply source as the motor. ... obtain rated armature current in both motor and generator. The p.u value of this load resistance is 0.96

A permanent magnet moving coil instrument gives full scale deflection of 25mA when a voltage of 75mV is applied across it. Calculate: (i) Resistance of shunt required for full scale deflection of 150 A. (ii) Series resistance for full scale deflection of 500 V.

Description : A permanent magnet moving coil instrument gives full scale deflection of 25mA when a voltage of 75mV is applied across it. Calculate: (i) Resistance of shunt required for full scale deflection of 150 A. (ii) Series resistance for full scale deflection of 500 V.

Last Answer : Answer :

A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Description : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Last Answer : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will be of 5 Hz.

The simplest method of controlling the terminal voltage of compound-wound DC generator is with a _____________. A. hand-operated field rheostat connected in series with the shunt field circuit B. separate exciter in a series with the shunt field C. carbon pile regulator in series with the load D. balance coil diverting neutral current through the shunt field

Description : The simplest method of controlling the terminal voltage of compound-wound DC generator is with a _____________. A. hand-operated field rheostat connected in series with the shunt field circuit B. ... in series with the load D. balance coil diverting neutral current through the shunt field

Last Answer : Answer: A

The terminal voltage of a DC shunt generator drops on load because of all of the following

Description : The terminal voltage of a DC shunt generator drops on load because of all of the following except : (A) Armature reaction (B) Armature resistance drop (C) Commutation (D) Field weakening due to armature reaction and armature resistance drop

Last Answer : (D) Field weakening due to armature reaction and armature resistance drop