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Burning out of winding in motor is due to
Short circuited capacitor
Capacitor value changed
Open circuiting of capacitor
None of above
Short circuited capacitor
Burning out of the auxiliary or main winding in a single-phase capacitor-start/run induction motor is primarily caused by a short-circuited capacitor. When the capacitor shorts, it draws excessive current from the supply and continuously keeps the high-resistance starting (auxiliary) winding energized, leading to severe overheating and insulation breakdown.
Burning out of the auxiliary or main winding in a single-phase capacitor-start/run induction motor is primarily caused by a short-circuited capacitor. When the capacitor shorts, it draws excessive current from the supply and continuously keeps the high-resistance starting (auxiliary) winding energized, leading to severe overheating and insulation breakdown.
H=I2Rt тАФ Heat produced in the winding due to excessive current
IauxтАЛ=ZauxтАЛVтАЛ тАФ Current flowing through the auxiliary winding circuit
In a single-phase induction motor, the starting (auxiliary) winding is designed for intermittent duty with high resistance and low reactance. Under normal conditions, a healthy capacitor provides the required phase shift, and a centrifugal switch disconnects the auxiliary winding once the motor reaches ~75% rated speed. If the capacitor shorts, it behaves like a dead short circuit, resulting in extremely high line current flowing continuously through the auxiliary winding. This excessive I2R heat generation quickly burns out the winding insulation.
A short-circuited capacitor eliminates its capacitive reactance (XCтАЛ=0), drastically lowering the impedance of the auxiliary winding circuit.
The reduced circuit impedance causes abnormally high current to flow continuously through the auxiliary winding.
Auxiliary windings are constructed with thinner wire (higher resistance) and cannot sustain continuous full-load heavy currents without burning.
Option B (Capacitor value changed): Alters starting torque and phase angle, leading to poor performance or hum, but usually does not cause immediate burnout.
Option C (Open circuiting of capacitor): Prevents phase shift, so the motor fails to start (remains stationary and hums), but normally trips thermal overload protection rather than immediately burning the winding.
A is correct тАФ A short-circuited capacitor allows excessive current to flow through the starting winding, causing extreme I2R heating and winding burnout.
Always remember: An open capacitor prevents a single-phase induction motor from starting (zero torque), whereas a shorted capacitor causes severe overcurrent and immediate winding burnout.