A single-phase capacitor-start induction motor starts, comes up to about 75% rated speed, slows down to a lower speed, and accelerates again. Where is the problem most likely to be?
• Capacitor-start induction motor operation: how the starting and running windings and capacitor work together as speed increases • Centrifugal switch function: when it opens, what it disconnects, and what happens if it fails or chatters • Typical symptoms of faulty starting vs running components (windings vs capacitor vs switch)
• At about what speed does the starting circuit normally disconnect in a capacitor-start motor, and which component controls that? • If the starting circuit cuts in and out around that speed, which component would cause repeated connection/disconnection rather than a complete loss of torque? • Would a bad winding or capacitor be more likely to prevent starting altogether, or to cause the speed to cycle up–down–up as described?
• Identify which component is responsible for connecting and disconnecting the starting winding based on motor speed. • Decide whether the described symptom is intermittent engagement of the start circuit, or a permanent loss of either start or run function. • Verify which choice corresponds to the device that operates mechanically with speed (not electrically with current alone).
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