How is Cemf produced?

CEMF is developed in a DC motor by the armature (conductor) rotating (relative motion) in the field of the motor (magnetic field). The function of the voltage that is developed in a DC motor (CEMF) opposes the applied voltage and results in the lowering of armature current.

How the back EMF is generated in DC motor?

When armature of dc motor rotates, the armature conductors move through the magnetic field, emf is induced in them. The induced emf acts in opposite direction to applied voltage. This voltage is known as back emf. is converted to mechanical energy and transmitted through shaft.

What determines the magnitude and polarity of the counter EMF in a DC motor?

The magnitude of the counter EMF is dependent on the magnetic field strength and the speed of the rotation of the armature. The counter EMF increases with the rotation. The effective voltage across the armature windings is the applied voltage minus the counter EMF.

What three factors determine the amount of counter EMF produced in the armature?

22 Cards in this Set

• The strength of the magnetic field of the pole pieces.
• The number of turns of wire in the armature.
• The speed of the armature.

What is counter electromotive force in a motor?

counter electromotive force. The emf that opposes the flow of current. Just as the windings of a generator produce voltage, the rotor in a motor produces voltage that is counter or opposed to the supply voltage. This counter emf creates additional resistance that must be overcome by the supply voltage.

What happens to the counter EMF in a series motor?

When the series motor slows down, the counter EMF decreases and more current flows through the field and the armature, thereby strengthening their magnetic fields.

What is motor emf?

A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.

Where does the emf generated in a dc generator directly proportional?

E = V + Ia Ra Thus, from the dc generator induced emf expressions it is clear that the induced emf is directly proportional to the conductor per pole, speed, number of poles and flux per pole.