What is the difference between EMF and back EMF?

What is the difference between EMF and back EMF?

The back emf is represented as a variable emf that opposes the emf driving the motor. Back emf is zero when the motor is not turning and increases proportionally to the motor’s angular velocity. The generator output of a motor is the difference between the supply voltage and the back emf.

What will happen if the back EMF of a DC motor vanishes suddenly?

What will happen if the back emf of a DC motor vanishes suddenly? Explanation: If back emf vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. If supplying unit didn’t trip down by this time, excess current in armature may heat up the armature. 3.

Which DC motor is used for machine tools?

DC shunt motor

Why is the DC motor preferred over AC motor?

DC motors have the advantage of: higher starting torque, quick starting and stopping, reversing, variable speeds with voltage input and they are easier and cheaper to control than AC. AC motor advantages include: lower power demand on start and minimal maintenance.

Which motor has poorest speed control?

DC motor

Which motor has best speed control?

Good speed regulation can be achieved with a motor which has nearly constant speed at all load below full rated load. I would like to thank you a lot! In case of DC, DC Shunt Motor, and in case of AC, Squirrel Case Induction motor has good speed regulation!

How do you control motor speed?

Thus, the speed of a DC motor can be controlled in three ways:

1. By varying the supply voltage.
2. By varying the flux, and by varying the current through the field winding.
3. By varying the armature voltage, and by varying the armature resistance.

Which motor should not be started on no load?

A series motor should never be started at no load. With no mechanical load on the series motor, the current is low, the counter-EMF produced by the field winding is weak, and so the armature must turn faster to produce sufficient counter-EMF to balance the supply voltage. The motor can be damaged by overspeed.

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

Answer : Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease. Answer : With the increase in load on a d.c. shunt motor, speed of the motor reduces slightly.

Which DC motor has got maximum self relieving property?

5. Which DC motor has got maximum self-relieving property? Explanation: DC series motor develops large starting torque initially and slow down with increase in load and so get automatically relived from heavy excessive load. Thus, DC series motor is called as self-reliving machine.

Why is DC series motor not started on no load?

The motor armature current is decided by the load. On light load or no load, the armature current drawn by the motor is very small. on no load as Ia is small hence flux produced is also very small. Thus, a DC series motor should never be started on no – load.

Which type of load is connected to the DC series motor?

DC Series Motors The series winding will have relatively few turns of larger wire or copper strip which are capable of carrying the full load current of the motor. On starting, because the windings are low resistance, a large current can be drawn producing a high starting torque.

When load is removed motor will run at the highest speed?

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

What is back emf in dc motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.