Red Seal Industrial Electrician Practice Exam

Question: 1 / 400

How do overload relays operate?

By measuring voltage across the motor terminals

By sensing heat from current in resistive elements

Overload relays operate primarily by sensing heat generated from the current flowing through resistive elements within the relay. When the motor draws excessive current—often due to a mechanical overload or a fault condition—this excess current leads to increased heating in the relay's components. The overload relay typically contains bimetallic strips that bend as they heat up, which ultimately triggers the relay to open its contacts and disconnect power to the motor. This mechanism protects the motor from damage caused by prolonged overcurrent conditions.

Understanding how overload relays function emphasizes the importance of thermal protection in motor control systems. By sensing heat rather than just electric parameters like voltage or rotational speed, overload relays can provide a crucial safety mechanism to ensure that motors operate within safe limits, promoting reliability and longevity in industrial applications.

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By controlling voltage to the motor

By monitoring the motor's rotational speed

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