Aeg-elotherm G.m.b.h.

Hans G Matthes

Hasso Wittenbecher

Erhard Mauler

Klaus Reifenrath

The invention relates to a parallel oscillatory circuit frequency converter comprising: a rectifier (1); an inverse rectifier (4) having thyristors disposed in a bridge circuit; a parallel oscillatory circuit (5) having an inductance (L) and a series connection of two capacitors (C, C.sub.K) whereby one capacitor (C) is connected to the load points of the bridge circuit; and a gate-controlled turn-off time control device (6) for the alternate firing (switching) of the thyristors a, b forming the particular diagonally adjacent bridge branches with a cycle frequency adapted to maintain a minimum turn-off time, a safety firing circuit (24, 25) controlled by a detector circuit (11-23) to detect incorrect switching delivering firing pulses without delay to all the thyristors at least until all the thyristors are current-carrying.

Parallel oscillatory circuit frequency converter with safety circuit

The invention relates to a parallel resonant-circuit converter having at least one intermediate-circuit inductance. In order to guarantee that the inverter will start even with different loads, the voltage produced when discharging a separately charged capacitor across the load is monitored. At some time after the maximum voltage across the load is reached, another separately charged capacitor is discharged via a thyristor of the inverter located in the biasing circuit of the intermediate-circuit inductance. Because of the blocked thyristor and of the capacitor charged to the voltage maximum, the biasing current is forced to flow via diagonal branches and including the load. In this manner, reliable starting of the inverter is possible even with loads having a different natural frequency.

Starting circuit for a parallel resonant circuit inverter

An inverter circuit with a thyristor bridge circuit, a load circuit developed as a parallel oscillating circuit connected to the bridge circuit, an impulse generating circuit for supplying ignition pulses to the bridge circuit and an arcing time regulating circuit for controlling the impulse generating circuit in accordance with the arcing time. A down-and-up integrating circuit is triggered by an ignition impulse to integrate down until a discriminator circuit produces a signal indicating zero crossover of the load current, thereafter to integrate up until a second discriminator produces a second signal indicating zero crossover of the load voltage, at which time the integrator output indicates arcing time, and is applied to the time regulating circuit to control the impulse generating circuit.

Inverter arcing control for a parallel-resonant circuit static frequency

A circuit and process for disconnecting the current from the operating gap of an electrolytic processing device in the event of a short circuit in which a signal is produced from the AC current in the transformer supplying power to the gap, such signal indicating the gap current, the maximum value of that signal is stored for successive time periods and the stored value for a preceding period compared with the present signal to operate a switch in the current supply to the gap when a short circuit condition is detected.

Short circuit disconnecting circuit

A method and apparatus for electrolytic processing of a metallic workpiece in which short circuits in the operating gap which produce an arc are detected and extinguished by an auxiliary d.c. current of limited duration and counter to the direction of flow of the operating current without withdrawing the electrode or cutting off the operating current.

Process and apparatus for electrolytic metal processing

A bridge circuit of the type whereby a plurality of individual switching elements such as thyristors are mounted in a frame between four contact rails. To minimize interaction between current flow in the elements and to cause the load current to be divided roughly evenly over the elements, the elements are physically mounted between the rails so that adjacent parallel mounted elements belong to different arms and do not carry current at the same time.

Bridge circuit arrangement on electrical frequency converters which can

An improved parallel-resonant circuit inverter of the type having a rectifier, a thyristor DC/AC converter connected thereto and operating at a controllable frequency, a parallel resonant circuit with an inductive load and a method of operation of such circuit whereby the converter voltage U is maintained at a constant operating value U.sub.B for a constant DC current I.sub.g = I.sub.go, in a first control range characterized by a low resonant-circuit damping, and control of the direct current I.sub.g for the purpose of maintaining the DC/AC voltage constant at its operating value U.sub.B, in the case of a constant thyristor extinction time t.sub.L = t.sub.LO, in a second control range characterized by a high damping, as well as by transition from the first to the second control range, if t.sub.L becomes equal to t.sub.LO in the case of increasing resonant-circuit damping, and transition from the second to the first control range, if I.sub.g become equal to I.sub.go in the case of decreasing damping.

Growing community of inventors

Wermelskirchen, Germany

Hans G Matthes