The invention relates to an overvoltage arrester for an electrical drive, especially a drive for a motor vehicle. The overvoltage arrester is designed to be connected to an on-board power supply system of a motor vehicle. The overvoltage arrester is designed to reduce any overvoltage produced in the on-board power supply system when a load is switched off. According to the invention, the overvoltage arrester is connected to a control unit for an electronically commutated electrical machine. The overvoltage arrester has an input for an on-board power supply system and is designed to detect when a pre-determined voltage value is exceeded and to produce an overvoltage signal depending on whether the voltage value is exceeded. The control unit is designed to transfer the electrical machine from an operating mode in which the machine generates power to an at least partial power-loss mode or to a mode in which it operates as a motor.