Back EMF of DC Motor

Back EMF of DC Motor Points : Back EMF of DC Motor According to motoring action, when current carrying conductor placed in a magnetic field so these conductors experience force whose direction will be given by Fleming’s left hand rule and motor (rotor) starts rotating. Now according to generator action, rotating armature conductor cuts the magnetic flux and according to Faraday’s Law of electromagnetic induction an emf induced in armature coil whose direction will be given by Fleming’s right hand rule. (b), The direction of emf induced in an armature conductor is opposite to applied d.c. voltage. Because of its opposing direction, it is referred to as “Back emf” and is represented by “E_b’.
V_t = E_b + I_a R_a
I_a = V_T - E_b/R_a

Always applied voltage is more than generating voltage and difference of this is the I_a R_a drop plus drop in a brush contact (if given).
If suppose E_b (back emf) is more than applied voltage, then I_a starts flowing in opposite direction, the machine works as a generator. This principle is applied in “regenerative braking”.