Abstract: To maintain a defined three-phase voltage system at the output terminals of a transformer device TE, for example, a transformer in a delta/wye connection where the primary-side neutral point is unconnected, even when an asymmetrical load is connected to it and to the secondary-side neutral point, single-phase transformers are used, whose primary windings are supplied with voltage by a pulse-width modulated, three-phase invertor in a bridge connection. Through the use of voltage regulators, the actual values of the secondary-side line voltages form the control voltages for each bridge-arm pair. The closed-loop control circuits of the three phase voltages are broken down in accordance with the structure of the transformer device by means of a break-down element. The setpoint values can be calibrated to a synchronizing voltage, and/or a current control for the conductor currents is superposed on the voltage regulators.

Abstract: In order to scrub a waste gas, for example, of foreign matter by means of an electrostatic filter, a power supply is provided which contains a converter whose output feeds the primary winding of a high-voltage transformer. The secondary winding is connected to the electrostatic filter via a high-voltage rectifier. Disposed in the intermediate circuit of the converter is a control element for the intermediate circuit current. This shields the supply network against the effects of the power converter commutations and of short-circuits in the filter to a great extent. A limiter for the filter voltage and a temporary separation of the transformer from the inverter in case of filter short-circuits may be provided to reduce the stress on the components which can be made small if a high-frequency working cycle for the setter and the inverter is used.

Abstract: To supply various loads connected to a uninterruptible bus, a power supply system N is connected (when functioning normally) by means of a mechanical switch, keeping an energy storage unit charged by means of a static converter which also functions preferrably as a phase shifter to stabilize the supply voltage. In the event of a power system malfunction, the storage unit is discharged by means of the static converter arrangement, and the mechanical switch is opened. The opening of this switch is not critical since between the switch and uninterruptible bus there is an inductance arrangement and an auxiliary switch. In case of a power system malfunction (auxiliary switch open), a large inductance and its large corresponding impedance of the inductive impedance arrangement becomes effective which during proper operation of the power system is shunted.

Abstract: An electrostatic precipitator is fed high voltage pulses by a pulse generating circuit including a high voltage transformer and a first thyristor switch connected in series with a primary winding of the transformer. Magnetic saturation of the core of the high voltage transformer is prevented by recurrently short circuiting the primary winding of the transformer by means of a second thyristor switch connected in parallel to the primary winding. The second thyristor switch is closed for a period of time extending from a first instant following a high voltage pulse crest to a second instant at or before the start of a pulse generating cycle subsequent to the pulse crest.