Answer :
If the field of a D.C. shunt motor gets opened while motor is running the motor will attain dangerously high speed.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. shunt motor, speed is independent of armature current.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a D.C. shunt motor more than its full-load speed can be obtained by decreasing the field current.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature torque of the D.C. shunt motor is proportional to armature current.
asked
Mar 20, 2018
by
anonymous
Answer :
As the load is increased the speed of D.C. shunt motor will reduce slightly.
asked
Mar 20, 2018
by
anonymous
Answer :
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens this will make armature to take heavy current, possibly burning it.
asked
Mar 20, 2018
by
anonymous
Answer :
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will increase.
asked
Mar 20, 2018
by
anonymous
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
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
asked
May 8, 2018
by
anonymous
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
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
asked
May 3, 2018
by
anonymous
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.
Answer :
increases
asked
Aug 25, 2019
by
anonymous
Description : Why does the speed of a DC shunt motor decrease as the load increases?
Answer :
Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.
asked
Jul 5, 2019
by
anonymous
Description : The effect of increasing load on a synchronous motor running with normal excitation is (A) Increase both its Ia and power factor. (B) Decrease Ia, but increase power factor. (C) Increase Ia, but decrease power factor (D) Decrease both Ia and power factor.
Answer :
The effect of increasing load on a synchronous motor running with normal excitation is Increase Ia, but decrease power factor
asked
Apr 28, 2018
by
anonymous
Description : DC shunt motor
Answer :
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asked
Apr 23, 2020
by
anonymous
Description : State any four applications of DC shunt motor.
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
asked
Jul 27, 2019
by
anonymous
Answer :
Yes, we can make the power factor of synchronous motor leading by adjusting its excitation.
asked
Mar 6, 2018
by
anonymous
Description : If we change the excitation of synchronous machine will it affect on motor speed?
Answer :
No, If we change the excitation of synchronous machine it will not affect on motor speed.
asked
Mar 18, 2018
by
anonymous
Answer :
In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.
asked
Mar 20, 2018
by
anonymous
Answer :
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses.
asked
Mar 20, 2018
by
anonymous
Answer :
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in armature current.
asked
Mar 20, 2018
by
anonymous
Description : what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?
Answer :
When excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor will stop.
asked
Mar 18, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.
asked
Mar 20, 2018
by
anonymous
Answer :
In D.C. shunt motors as load is reduced the speed will remain almost constant.
asked
Mar 20, 2018
by
anonymous
Answer :
The direction of rotation of a D.C. series motor can be changed by interchanging field terminals.
asked
Mar 20, 2018
by
anonymous
Answer :
D.C. shunt motors are used for driving machine tools.
asked
Mar 20, 2018
by
anonymous
Answer :
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor.
asked
Mar 20, 2018
by
anonymous
Description : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load (A) The armature current increases and the power factor decreases (B) The armature current decreases and the power factor also decreases (C) The armature current decreases and the power factor increases but is lagging (D) The armature current decreases and the power factor increases and is leading
Answer :
In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load The armature current decreases and the power factor increases and is leading
asked
Apr 29, 2018
by
anonymous
Answer :
In a manual shunt motor starter over load relay is connected in series and no volt relay in parallel with the load.
asked
Mar 20, 2018
by
anonymous
Description : While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then (A) It would over-run the other alternator (B) Its rotor will fall back in phase with respect to the other machine (C) Its portion of share in load will increase (D) Its power factor would be decreased.
Answer :
While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then Its portion of share in load will increase
asked
Apr 28, 2018
by
anonymous
Answer :
The purpose of retardation test on D.C. shunt machines is to find out stray losses.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.
asked
Mar 20, 2018
by
anonymous
Answer :
If a D.C. motor is connected across the A.C. supply it will burn due to heat produced in the field winding by eddy currents.
asked
Mar 20, 2018
by
anonymous
Answer :
If a D.C. series motor is operated on A.C. supply, it will spark excessively, have poor efficiency, have poor power factor.
asked
Mar 20, 2018
by
anonymous
Answer :
In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.
asked
Mar 20, 2018
by
anonymous
Answer :
For starting a D.C. motor a starter is required because it limits the starting current to a safe value.
asked
Mar 20, 2018
by
anonymous
Answer :
D.C. Series motor is generally preferred for cranes and hoists.
asked
Mar 20, 2018
by
anonymous
asked
Mar 20, 2018
by
anonymous
Answer :
Cumulatively compounded D.C. motor will be suitable along with flywheel for intermittent light and heavy loads.
asked
Mar 20, 2018
by
anonymous
Answer :
The type of D.C. motor used for shears and punches is cumulative compound D.C. motor.
asked
Mar 20, 2018
by
anonymous
Answer :
Cumulative compound D.C. motor is preferred for elevators.
asked
Mar 20, 2018
by
anonymous
Description : The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above
Answer :
The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above
asked
Mar 20, 2018
by
anonymous
Answer :
At the instant of starting when a D.C. motor is put on supply, it behaves like a low resistance circuit.
asked
Mar 20, 2018
by
anonymous
Answer :
In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.
asked
Mar 20, 2018
by
anonymous
Description : As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?
Answer :
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.
asked
Mar 20, 2018
by
anonymous
Answer :
Sparking, is discouraged in a D.C. motor because commutator gets damaged.
asked
Mar 20, 2018
by
anonymous
Answer :
Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a D.C. series motor is inversely proportional to the armature current.
asked
Mar 20, 2018
by
anonymous