EE MCQ

SSC JE Electrical 2019 with solution SET-1
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In a capacitor start single phase induction motor the current in the:

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.

Related Question

SSC JE Electrical 2019 with solution SET-1
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In the circuit shown, if R = 0, then the phase angle between v(t) and i(t) is

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°.

SSC JE Electrical 2019 with solution SET-1
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Split-phase, capacitor, and shaded-pole single-phase motors classified as:

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.

SSC JE Electrical 2019 with solution SET-1
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A magnetic circuit is applied with a current that changes at a rate of 5 A/sec. The circuit has an inductance of 2H, then the self-induced EMF is

Given

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