Abstract: In addition to a circuit for clamping a power supply voltage supplied from a power supply to a rated voltage, a circuit for clamping the power supply voltage to a voltage of less than the rated voltage is arranged. Even if it is necessary to flow a large current into the voltage clamping transistor for overvoltage protection, a large current can be flowed within a safe operating area of the transistor if the transistor is operated at a low voltage. Damage of the voltage clamping transistor or degradation of reliability can be prevented.

Abstract: An arrangement for transporting air with the aid of corona-wind including tubes to extract detrimental side effects from corona discharge. A first tube is arranged with an open end located downstream of and axially in line with the corona electrode, as to face towards the electrode and such that the air flowing past in the vicinity of the corona electrode will flow into the open end of the first tube. A second tube having an open end is positioned upstream of and axially in line with the corona electrode, this second tube being directed downstream. The first tube and the second tube are connected together so that the air flowing in through the open end of the first tube will be conducted to the second tube and flow out through the open end of the second tube in the immediate vicinity of the corona electrode.

Abstract: A control for an inductive load switches current on and off to regulate about a command value, a decaying recirculation current flowing through the load during the switch off periods. The current is sensed during the switch on periods and charges a capacitor to provide a simulation signal representing the motor current. The capacitor is allowed to discharge through a resistor during the switch off periods at the rate of the decaying recirculation current. The simulation signal is compared to the command value to control the switching. The simulation signal is sensed during a command value of zero current to determine offset errors for calibration purposes.