Abstract: An inverter control unit having a bridge circuit provided with controllable semiconductor switches in upper and lower circuit arms, which bridge circuit converts a direct voltage to be fed to the inverter into an alternating voltage of variable frequency and amplitude, said control unit controlling the semiconductor switches by pulse-width modulation (PWM) to generate an inverter output voltage, and said control unit comprising a first control section (21) at ground potential and a second control section (22) at the potential of the semiconductor switches, galvanically isolated channels being provided between said sections for serial transmission of control data from the first control section to the second control section and of feedback data from the second control section to the first control section.

Abstract: A single-phase or multi-phase inverter protected with respect to the rates of increase of current and voltage, the said inverter comprising a filter capacitor and a choke protecting with respect to the rate of increase of current, as well as, members protecting with respect to the voltage increase rate. In order for it to be possible to discharge the energy stored in the magnetic field of the choke and in the capacitor, between the change-over steps of the inverter substantially without losses, for each phase, there is a series connection of the capacitor and a diode connected in parallel with only one semiconductor switch and a diode is connected between the connection point between the capacitor and the diode, and one terminal of a storage capacitor. The energy in this way transferred to the separate storage capacitor can then be transferred to the filter capacitor by use of a breaker.