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: Exactly defined current pulses having high edge steepness and high final value are required for the pulse-like generation of high magnetic fields in inductive users. Particularly in nuclear magnetic resonance tomography, such pulses serve the purpose of building up a topically variable magnetic field with an optimally linear field strength gradient. A power supply for generating such current pulses includes a series connection of a stepping voltage switch and a variable voltage source, whose resultant output voltage is applied to the inductive by a voltage commutator user with a suitable operational sign for the build-up or dismantling of the individual pulses. A switching and regulating circuit controls the stepping switch, the variable voltage source and the voltage commutator dependent on prescribed rated curves of the pulses, such that the pulses have a rise and decay time independent of the final value.

Abstract: A pressure valve has a valve member 22 which can be lifted from its seat against the effect of a valve spring 25, 26 and a control piston 12 which is movable coaxially to the valve member, and a connection passage 15, 21, 23 having a throttle point 16 extending from the pressure side of the valve member to an opening on the side of piston 12 which faces away from the valve member. In order that the valve limit pressure peaks with a simple structure, the valve spring abuts on the control piston and the surface of the valve member on which pressure acts is smaller than the surface of the control piston on which pressure acts and which connected to the valve member surface through the connection passage.