What would happen if the centrifugal switch or relay, for cutting out the starting winding of a split-phase induction motor, failed to open while the motor was in operation?
• Split-phase induction motor operation: purpose of the starting (auxiliary) winding vs. the running (main) winding • Role of the centrifugal switch/relay in disconnecting the starting winding once up to speed • Effects of keeping a high-resistance starting winding energized during continuous operation (current, heating, torque, speed)
• Ask yourself: Is the starting winding designed for continuous duty, or only for the short starting period? What happens if it carries current the whole time? • Consider whether keeping the starting winding in the circuit will make the rotor spin faster, slower, or mostly at the same synchronous speed, and which effect is more critical in practice. • Think about which failure mode is most common in motors: overspeed, reduced speed, insulation overheating, or an automatic time delay stopping the motor.
• Verify the duty rating of the starting/auxiliary winding (is it continuous or intermittent?). • Check how current and heat in the starting winding compare to the main winding when left in the circuit. • Confirm whether a time delay device is normally part of a simple split‑phase motor’s protection, or if damage occurs before protective action.
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