How do electromagnetic overload relays operate?

Electromagnetic overload relays operate on the principle of magnetic induction, where the magnetic field generated by the electrical current flowing through the relay coil increases with the current level. As the current rises beyond a specific threshold, the magnetic force becomes strong enough to actuate the relay mechanism, which typically involves tripping a circuit or activation.

This operation is critical in protecting motors from overheating due to excessive current, which can cause damage to the motor windings. By activating in response to higher current levels, electromagnetic overload relays serve as an effective means of safeguarding machinery against overload conditions, ensuring operational efficiency and prolonging equipment lifespan.

In this context, resistance of materials and thermal expansion do not play roles in electromagnetic overload relays, as their primary function is driven by electromagnetic principles. Neither do mechanical switch operations define the working mechanism of these relays, which rely heavily on the relationship between current intensity and the resulting magnetic field strength.