Recent questions and answers in DC motor

1 answer 8 views

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

answered Jul 5 in DC motor
1 answer 9 views

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

answered Jul 5 in DC motor
1 answer 16 views

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

answered Jul 5 in DC motor
1 answer 12 views

With the increase in load on a d.c. shunt motor, speed of the motor (a) increases proportionately (b) remains constant (c) increase slightly (d) reduces slightly 

answered Jul 5 in DC motor
0 answers 38 views
2 answers 49 views

 A DC Motor develops a torque of 150 N-m. A 10 percent reduction in the field flux causes a 50 percent increase in armature current. The new value of torque is: A) 102.5 N-m B) 202.5 N-m C) 172.5 N-m D) 232.5 N-m

answered Jun 9 in DC motor
5 answers 27 views

If a d.c. motor is disconnected from the source and armature circuit is short circuited through a suitable resistance, the process is called (a) regenerative breaking (b) rheostatic breaking (c) dynamic breaking (d) no breaking is possible

answered Jul 22, 2018 in DC motor
0 answers 19 views

A separately excited d.c. motor fed from single phase full converter with firing angle 60° runs at 1000 r.p.m. If motor is connected to single phase semiconverter with the same firing angle of 60°, it would run at (a) 2000 rpm (b) 1850 rpm (c) 1500 rpm (d) 1000 rpm 

asked May 25, 2018 in DC motor
0 answers 5 views

The widely used series-parallel system of speed control of d.c. series motors in traction work gives a speed range of about (a) 1 : 2 (b) 1 : 3 (c) 1 : 4 (d) 1 : 6

asked May 25, 2018 in DC motor
0 answers 10 views

Retardation test on d.c. shunt motors is performed for (a) frictional losses (b) stray losses (c) copper losses (d) iron loss  

asked May 25, 2018 in DC motor
0 answers 22 views

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 full load speed of the motor is (a) 1200 r.p.m. (b) 1080 r.p.m. (c) 1040 r.p.m. (d) 1000 r.p.m.

asked May 25, 2018 in DC motor
0 answers 11 views

The purpose of inserting external resistance at the time of starting a d.c. motor is to (a) increase the starting torque. (b) increase the armature flux. (c) reduce the starting current. (d) reduce the armature flux. 

asked May 25, 2018 in DC motor
0 answers 15 views

The function of carbon brush and commutator arrangement in a d.c. motor is (a) to produce unidirectional torque. (b) to produce unidirectional current in the armature. (c) to help in changing the direction of rotation. (d) to reduce sparking. 

asked May 25, 2018 in DC motor
1 answer 8 views

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

answered May 18, 2018 in DC motor
1 answer 10 views

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 connected to a load resistance. The armature resistance is 0.02 p.u. Armature reaction and mechanical losses can be neglected. ... rated armature current in both motor and generator. The p.u value of this load resistance is  (A) 1.0 (B) 0.98 (C) 0.96 (D) 0.94

answered May 18, 2018 in DC motor
1 answer 16 views

The dc motor, which can provide zero speed regulation at full load without any controller is  (A) series (B) shunt (C) cumulative compound (D) differential compound

answered May 17, 2018 in DC motor
1 answer 17 views

The chief advantage of Ward-Leonard system D.C. motor speed control is that is  1. Can be used even for small motors 2. has high overall efficiency at all speeds 3. Gives smooth, sensitive and wide speed control 4. Uses a flywheel to reduce fluctuations in power demand

answered May 13, 2018 in DC motor
1 answer 14 views

Under which of the following conditions is a DC motor provided with compensating winding used?  1. Wide range of speed control above normal  2. Wide range of steady load variation with no speed control  3. Wide range of rapid variation in load.   Select the correct answer using the codes given below:   (a) 1, 2 and 3 (b) 2 and 3 (c) 1 and 2 (d) 1 and 3

answered May 13, 2018 in DC motor
2 answers 88 views

A 220 V shunt motor develops a torque of 54 N-m at armature current of 10 A. The torque produced when the armature current is 20 A, is?

answered Apr 23, 2018 in DC motor
1 answer 30 views

In a d.c. motor, unidirectional torque is produced with the help of

answered Mar 26, 2018 in DC motor
1 answer 49 views

A 200 V, 10 A motor could be rewound for 100 V, 20 A by using .......... as many turns per coil of wire, having .......... the cross-sectional area.

answered Mar 26, 2018 in DC motor
1 answer 15 views

A shunt d.c. motor works on a.c. mains?

answered Mar 26, 2018 in DC motor
1 answer 19 views

The d.c. series motor should never be switched on at no load because?

answered Mar 26, 2018 in DC motor
1 answer 23 views

A series motor is best suited for driving?

answered Mar 26, 2018 in DC motor
1 answer 16 views

When load is removed, .......... motor will run at the highest speed.

answered Mar 26, 2018 in DC motor
1 answer 16 views

Unlike a shunt motor, it is difficult for a series motor to stall under heavy loading because?

answered Mar 26, 2018 in DC motor
1 answer 16 views

As compared to shunt and compound motors, series motor has the highest torque because of its comparatively .......... at the start.

answered Mar 26, 2018 in DC motor
1 answer 16 views

The Ta/Ia graph of a d.c. series motor is a?

answered Mar 26, 2018 in DC motor
1 answer 22 views

Between no-load and full-load, .......... motor develops the least torque.

answered Mar 26, 2018 in DC motor
1 answer 39 views

A d.c. shunt motor is found suitable to drive fans because they require?

answered Mar 26, 2018 in DC motor
1 answer 12 views

If the field circuit of a loaded shunt motor is suddenly opened?

answered Mar 26, 2018 in DC motor
1 answer 27 views

If the pole flux of a d.c. motor approaches zero, its speed will?

answered Mar 26, 2018 in DC motor
1 answer 10 views

If the load current and flux of a d.c. motor are held constant and voltage applied across its armature is increased by 10 per cent, its speed will?

answered Mar 26, 2018 in DC motor
1 answer 16 views

If load on a d.c. shunt motor is increased, its speed is decreased due primarily to?

answered Mar 26, 2018 in DC motor
1 answer 23 views

Neglecting saturation, if current taken by a series motor is increased from 10 A to 12 A, the percentage increase in its torque is ........ percent

answered Mar 26, 2018 in DC motor
1 answer 130 views

A d.c. motor develops a torque of 200 N-m at 25 rps. At 20 rps it will develop a torque of .......... N-m.

answered Mar 26, 2018 in DC motor
1 answer 20 views

The shaft torque of a d.c. motor is less than its armature torque because of .......... losses.

answered Mar 26, 2018 in DC motor
1 answer 15 views

The current drawn by a 120 - V d.c. motor of armature resistance 0.5 Ω and back e.m.f. 110 V is .......... ampere.

answered Mar 26, 2018 in DC motor
1 answer 16 views

It is possible to increase the field flux and, at the same time, increase the speed of a d.c. motor provided its .......... is held constant.

answered Mar 26, 2018 in DC motor
1 answer 10 views

Under constant load conditions, the speed of a d.c. motor is affected by?

answered Mar 26, 2018 in DC motor
1 answer 15 views

The maximum torque of d.c. motors is limited by?

answered Mar 26, 2018 in DC motor
1 answer 20 views

In a d.c. motor, the mechanical output power actually comes from?

answered Mar 26, 2018 in DC motor
1 answer 22 views

A d.c. motor can be looked upon as d.c. generator with the power flow?

answered Mar 26, 2018 in DC motor
1 answer 15 views

The induced e.m.f. in the armature conductors of a d.c. motor is?

answered Mar 26, 2018 in DC motor
1 answer 17 views

The mechanical power developed by the armature of a d.c. motor is equal to?

answered Mar 26, 2018 in DC motor
1 answer 12 views

The Eb/V ratio of a d.c. motor is an indication of its?

answered Mar 26, 2018 in DC motor
1 answer 39 views

The normal value of the armature resistance of a d.c. motor is?

answered Mar 26, 2018 in DC motor
1 answer 15 views

The counter e.m.f. of a d.c. motor?

answered Mar 26, 2018 in DC motor
1 answer 66 views

In DC motor iron losses are occurred in?

answered Mar 26, 2018 in DC motor
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