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

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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

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Answer : The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.

Answer : As the load is increased the speed of D.C. shunt motor will reduce slightly.

Answer : The speed of a D.C. series motor is inversely proportional to the armature current.

Answer : In a D.C. shunt motor, speed is independent of armature current.

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

Description : What are the speed control methods of dc motor?

Answer : Field control of DC motor Armature control of DC motor

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Answer : If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will increase.

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.

Description : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) ... proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

Answer : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ directly proportional to α and inversely proportional to Φ

Answer : The speed of a D.C. shunt motor more than its full-load speed can be obtained by decreasing the field current.

Description : The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

Answer : It   can  be  corrected  by  increasing  the  input  to  the  prime  mover.

Description : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min (A) 100 rpm (B) 200 rpm (C) 400 rpm (D) 800 rpm

Answer : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm

Answer : The speed of a universal motor is usually reduced by using gearing.

Answer : Speed control of a universal motor is achieved by varying field flux with tapped field windings, connecting rheostat in series, applying variable voltage by means of silicon controlled rectifier, applying variable voltage by means of variable auto-transformer.

Answer : The speed control of universal motor used for sewing machines is by varying the resistance.

Answer : The operating speed of a synchronous motor can be changed to new fixed value by changing frequency.

Answer : Speed torque characteristic of a repulsion induction motor is similar to that of a D.C. compound motor.

Answer : In variable speed motor a weaker commutating field is needed at low speed than at high speed.

Answer : Series motor has the poorest speed control.

Answer : For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.

Answer : In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.

Answer : Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.

Answer : The speed/load characteristics of a universal motor is same as that of D.C. series motor.

Answer : If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.

Description : Why the speed of synchronous motor is constant?

Description : speed control methods of three phase induction motor?

Answer : Speed control of three phase induction motor

Answer : By looking at Commutator part of the motor, it can be easily confirmed that a particular motor is D.C. motor.

Answer : The direction of rotation of a D.C. series motor can be changed by interchanging field terminals.

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.

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.

Answer : When two D.C. series motors are connected in parallel, the resultant speed is normal speed.

Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

Answer : Ns         equals        f/pair pole 50/4      - 12.5

Answer : The speed of a universal motor is generally reduced by using gear trains.

Answer : Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be cumulatively compounded.

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.

Description : Speed control of the motor using TRIAC

Answer : Speed control of the motor using TRIAC:  This basic phase triggering circuit uses the triac in series with the motor across an AC sinusoidal supply. The variable resistor, VR1 is used ... meaning that it may not trigger at the exact same point for each positive and negative half cycle.

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.

Description : An electric motor in which both stator field and rotor rotates with same speed is called?

Answer : An electric motor in which both stator field and rotor rotates with same speed is called synchronous motor.

Description : Synchronous motor always runs at which speed?

Answer : Synchronous motor always runs at synchronous speed.

Description : Which motor has the best speed regulation?

Description : How do you measure the speed of a motor?

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.

Answer : Cumulatively compounded D.C. motor will be suitable along with flywheel for intermittent light and heavy loads.

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%.

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.

Answer : The current drawn by the armature of D.C. motor is directly proportional to the torque required.

Description : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

Description : Chopper controlled DC motor

Answer : Chopper controlled DC motor

Answer : For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

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