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

1 Answer

Answer :

The counter e.m.f. of a d.c. motor helps in energy conversion.

Related questions

Last Answer : When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.

Last Answer : The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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

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.

Last 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.

Description : Explain the necessity of starter for D.C. motor. State various types of D.C. motor starter. 

Last Answer : Necessity of Starter for D.C. Motor: Armature current is given by equation Ia = (V−Eb)/Ra i) If the motor is at standstill or rest, back emf Eb is zero (as Eb= ZNP/(60A), at start speed N ... . Types of D.C. motor starters: i) Two point starter ii)Three point starter iii) Four point starter

Description : State at least one function and the material used for the following parts of DC Motor.

Last Answer : Part Function Material Yoke -Provides mechanical support for poles -Acts as protecting cover for machine -Provides path for magnetic flux Cast Iron OR Cast Steel Field Winding - ... Pole core  Provides mechanical support to field winding. Cast Iron OR Cast Steel

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.

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

Last Answer : A d.c. motor can be looked upon as d.c. generator with the power flow reversed.

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

Last Answer : The Eb/V ratio of a d.c. motor is an indication of its efficiency.

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

Last Answer : The normal value of the armature resistance of a d.c. motor is 0.5.

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

Last Answer : Commutator provides unidirectional torque and pulsating dc

Description : In DC motor iron losses are occurred in?

Last Answer : In DC motor iron losses are occurred in the armature.

Last Answer : Series motor has got maximum self relieving property.

Description : D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select the?

Last Answer : D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select the compound motor.

Description : D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the?

Last Answer : DC motor mostly preferred is DC series motor becaus the load is continuous for a long time

Last 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.

Last Answer : Shunt motors,  Series motors, Compound motors

Last Answer : Torque developed by a D.C. motor depends upon magnetic field, active length of the conductor, current flow through the conductors, number of conductors, radius of armature.

Description : The back emf of synchronous motor depends on?

Last Answer : The back emf of synchronous motor depends on load angle.

Last 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.

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?

Last 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.

Description : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is  (1) 1000V (2) 100V (3) 600V (4) 10,000V

Last Answer : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V

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 :

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Last Answer : Counter counts only when the trigger is applied and timer counts continuously with some equal delay.

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