In motor protection, what is the main role of overload relays?

The main role of overload relays is to protect against overheating. Overload relays are designed to detect excessive current flowing through the motor, which can indicate that the motor is overloaded or running under conditions that could lead to overheating. When the current exceeds the relay's preset threshold for a specified duration, the relay will open the circuit, disconnecting power to the motor and preventing potential damage from overheating.

This function is critical because it ultimately helps extend the life of the motor by reducing the risk of thermal failure. Overheating can lead to insulation breakdown and other issues that can cause the motor to fail prematurely. Thus, the overload relay acts as a safeguard to ensure that the motor operates within safe parameters, enhancing reliability and longevity.

In this context, while other options relate to different aspects of motor control and protection, they do not specifically focus on the primary function of preventing damage from overheating that overload relays are designed for.