The protective relay integrates stator and rotor heating into a single model, by measuring the terminal currents. When the TCU. The invention discloses a motor thermal overload protection method. The method comprises the following steps: (1), acquiring the load current of a motor, and calculating an equivalent current Ieq; (2), calculating the heat accumulation value of the motor at the moment according to a formula. Overload relays protect motors and equipment from thermal damage caused by prolonged overcurrent conditions. IEC 60255 defines standards, formulas, and performance requirements, enabling accurate calculations and real-world applications. The temperature T at any instant is given by: Temperature rise is proportional to the current squared: Therefore, it can be shown that, for any overload current I, the permissible time t for this. A motor is an electric machine that converts electrical energy to Mechanical energy with typical 98% efficiency.
