Back of emf in controlling armature current [ back emf as a current register]
voltage eqn for dc motor is Ia(V-Eb)/(Rb)
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 in electric motors
- When something like a refrigerator or an air conditioner (anything with a motor) first turns on in your house, the lights often dim momentarily. To understand this, realize that a spinning motor also acts as a generator.
- Where you may be confused is that there are actually two back-emf – the voltage generated by the motor when it is spinning, and the voltage caused by inductance when the PWM switch opens.
- Back emf helps dc motor runs safely without damaging its winding according to formula Ia=V−EbRa
- The presence of back emf makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load.