A method of controlling a switching frequency of an inverter, the method comprising the steps of: measuring a signal indicative of a temperature variable at a first switching frequency to determine a measured temperature variable; comparing the measured temperature variable to a first threshold; determining if the measured temperature variable is above the first threshold; if the measured temperature variable is not above the first threshold, calculating the temperature variable at a second switching frequency; if the temperature variable calculated at the second switching frequency is less than the first threshold, setting the switching frequency of the inverter to the second switching frequency.