In a motor protection system, what typically triggers an overload relay to activate?

An overload relay is specifically designed to protect electric motors from damage due to excessive current, which can occur when a motor is subjected to greater loads than it is rated for. When the current flowing through the motor exceeds a predetermined threshold, the overload relay activates, interrupting the circuit and preventing overheating and potential damage to the motor. This mechanism functions based on the principle that excessive current can indicate that the motor is under strain, either due to mechanical overload or other issues that may lead to failure.

High ambient temperature, low voltage supply, and inconsistent phase supply are factors that can influence motor performance, but they do not directly trigger the overload relay. While high temperatures can contribute to decreased motor efficiency, they do not cause the overload relay to trip. Low voltage can lead to other operational issues, such as overheating due to increased current draw, but it does not directly indicate an overload condition. Inconsistent phase supply may lead to imbalances and operational anomalies, yet the primary purpose of the overload relay is to respond to excessive current, making that the definitive trigger for activation.