Back EMF is the system in the coil of an electric motor that opposes the current flowing through the coil, when the armature rotates. … Back EMF is the system in the coil of an electric motor that opposes the current flowing through the coil, when the armature rotates.
What is back emf 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.
What is meant by back emf?
Counter-electromotive force (counter EMF, CEMF), also known as back electromotive force (back EMF), is the electromotive force (voltage) that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday’s law of induction, electromagnetic induction, Lenz’s law).
What is back emf effect in motors?
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.
Is back emf AC or DC?
Back EMF can have either a sinusoidal (AC) or a trapezoidal (DC) waveform. The shape of the back EMF is important, as it determines the type of drive current and commutation method that should be used for the motor.
What will happen if the back emf of dc motor vanishes suddenly?
If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.
What does back emf depend on?
The back EMF depends, of course, on the speed of the motor — the change in magnetic flux that generates it increases with motor speed — so that as the motor begins to turn, the back EMF grows until the motor has reached its maximum speed, at which point the back EMF stays at its maximum value.
What are the advantages of DC series motor?
Advantages of DC Series Motor
Dc series motor have good accelerating torque. Dc series motor have a relatively huge starting torques. Dc series motor delivers high torque during an overload. The dc series motor draws less current and power from the source compared to a shunt or compound motor.
Is there back emf in AC motors?
ALL motor armatures that spin their coils in a magnetic field, create an Counter AC Voltage called Back-EMF. according to Lenz’s Law. It does not matter if the motor armature has a Slip Ring attached or a Commutator attached.
What is the difference between emf and back emf?
If an open coil is subjected to a variable magnetic field, at the ends of the coil a potential difference is induced which is called induced emf. If a coil is connected to an emf source and switched on, the rising current will produced an variable magnetic field which in turn produces an emf. It is called back emf.