Which one of the following describes the operation of a thermal overload device for a large motor?
A. A temperature sensor monitors the temperature of the operating equipment and completes a circuit to trip the breaker if the temperature setpoint is exceeded.
B. A balanced bridge circuit compares actual current to a fixed overcurrent setpoint and completes a circuit to trip the breaker if the current setpoint is exceeded.
C. A heater element in series with the motor heats up in proportion to the motor current and completes a circuit to trip the breaker if a high current condition persists.
D. An induction coil in series with the motor generates a secondary current proportional to the primary current and completes a circuit to trip the breaker if a high current condition persists.
Show Answer
Answer: C
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