In the capacitor start, single-phase induction motor the capacitor is connected in series with the starting auxiliary winding. In this manner, the current in the starting winding may be made to lead the line voltage. Since the running winding current lags the line voltage, the phase displacement between the two currents is made to approximately 90° on starting.
Placing the capacitor in the auxiliary winding circuit to produce a greater phase difference between the current in the main and the auxiliary windings. Due to greater phase difference capacitor Start motors have very high starting torque for a single-phase AC motor.
In the given circuit if R = 0 then the circuit becomes purely inductive. So the phase angle between v(t) and i(t) is 90°.
Split-phase, capacitor, and shaded-pole single-phase motors classified as single phase motor.
The single-phase motor with a single winding is not self-starting, because if the single winding is fed with a.c., it simply produces a “pulsating field” which rises and falls with the alternating current, and this type of field produces no torque in the rotor.
Inductance L = 2 H
Rate of change of current di/dt = 5 A/sec
Self induced EMF = − (Rate of change of current × Inductance) = −L(di/dt)
= −(5 × 2) = −10V