The application provides an over-temperature protection method of a variable frequency driving device and the variable frequency driving device, wherein the method comprises the following steps: obtaining the input
voltage of a power supply circuit and the output
voltage and output current of a
driving circuit in real time during the operation of an
alternating current motor, calculating the preliminary over-temperature threshold of a
power module of the
driving circuit, comparing the preliminary over-temperature threshold with the
maximum temperature value allowed by the
power module to determine the final over-temperature threshold, obtaining the temperature of the
power module, judging whether the temperature of the power module exceeds the final over-temperature threshold, adjusting the speed instruction when the final over-temperature threshold is exceeded, and enabling the
driving circuit to drive the
alternating current motor to work according to the adjusted speed instruction. Thus, the over-temperature threshold of the power module is adjusted adaptively according to the input
voltage, the output voltage and the output current, and the speed instruction is adjusted according to the over-temperature threshold, so that the temperature of the power device of the
power factor correction circuit and the
inverter circuit is prevented from being too high.