Thermal relays are mainly used to protect the load from overload. The function of the air switch function: short circuit protection, overload protection function, isolation switch function, residual current action, low voltage trip function, etc.

When the motor is protected, the common air switch is used as the short-circuit protection component (most air switches can double as the isolation component), and the thermal relay is used as the overload protection component (because the air switch is not easy to accurately set as the load protection component setting value).

It is also useful to use an air switch (thermal magnetic trip) with a double release for short-circuiting and overload protection of the motor. Do not use a thermal relay.