A method of operating an inverter for controlling an electrical machine

A method of operating an inverter for controlling an electric machine, the method comprising the steps of determining a fundamental frequency of one or more inverter stages based on a torque command for controlling the torque, speed or direction of the electrical machine (117); Generating an initial reference output current based on the torque command; Estimating each junction temperature of a corresponding semiconductor device among a plurality of semiconductor devices for each phase of an inverter (188); Determining a hottest device with a maximum junction temperature among the semiconductor devices in the inverter (188); includes, and determining whether the highest junction temperature parameter is less than the maximum junction temperature parameters for the corresponding semiconductor device in order to decide whether or not a duty cycle of the semiconductor devices is not adjusted.