These overload devices are designed to respond to the heat produced by what in the motor?

• A. Voltage across the motor
• B. Current flowing through the motor
• C. Ambient temperature around the motor
• D. Mechanical load on the shaft

Answer: (C)

Overload devices are thermal protectors that respond to heat generated inside the motor windings. The electrical current flowing through the windings produces heat (I^2R losses), and when the motor is overloaded or stalled, the current increases, causing the winding temperature to rise. The thermal protector senses this temperature and trips when it reaches its limit to prevent insulation damage. Ambient temperature around the motor can affect overall conditions, but the device is designed to react to heat produced by the current in the windings, not the surrounding environment.