Abstract: A method and a device balance a three-phase system (18) that is produced by means of an invertor (12) from a d.c. voltage source (10), such that the output (R',S',T') of this invertor (12) is equipped with a filter (14) to which a neutral grounding transformer (16) has been added. In keeping with the invention, absolute values (u.sub.R.sup.*, u.sub.S.sup.*, u.sub.T.sup.*), each of which is fed into a regulator device (34, 42; 36, 44; 38, 46) are formed from measured phase-to-phase voltages (u.sub.RL, u.sub.SL, u.sub.TL). Each absolute value produces a phase-to-phase voltage manipulated variable (U.sub.StR, U.sub.StS, U.sub.StT) such that by means of a transformer device (54), these phase-to-phase voltage manipulated variables (U.sub.StR, U.sub.StS, U.sub.StT) are transformed into phase-to-neutral manipulated variables (U.sub.Str, U.sub.Sts, U.sub.Stt) and are fed into angularly symmetrical control units (96, 98, 100).

Abstract: A method and a device balance a three-phase system (18) formed by means of an invertor (12) from a dc voltage source (10), the output (R', S', T') of said invertor (12) being provided with a filter (14) followed by a neutral grounding transformer (16). Positive and negative phase-sequence system components (u.sub.1s, u .sub.1c, u.sub.2c, u.sub.2s) are formed from the measured voltages (u.sub.R, u.sub.S, u.sub.T). These measured voltages (u.sub.R, u.sub.S, u.sub.T) form positive and negative phase-sequence system manipulated variables (U.sub.St.phi., U.sub.St1c, U.sub.St2c, U.sub.St2s). The positive and negative phase-sequence system manipulated variables (U.sub.St1c, U.sub.St2s, U.sub.St2c) are transformed by means of a transformation device (50) into phase-to-neutral voltage manipulated variable (U.sub.Str, U.sub.Sts, U.sub.Stt) and routed to angularly symmetrical drive units 76, 78, 80).

Abstract: A device which generates a symmetrical output voltage system at the output of a transformer with a neutral point which can carry current on the secondary side or a Y-point former, even if the load is asymmetrical, each primary terminal being fed from a pair of bridge arms of a pulsed inverter. The device further comprises a decoupling network in which the conductor voltages measured on the secondary side are converted into substitute actual values according to the structure of the transformer circuit, which actual values represent symmetrical output voltages or a likewise symmetrical system with a free Y-point. These substitute actual values are controlled to form a system of symmetrical reference values.

Abstract: An inverter arrangement for generating a three-phase AC output voltage is provided with three pulse-controlled, free-running single-phase inverters. The inverters are connected at their inputs to a DC voltage source, and at their outputs to respective low-pass filters. The low-pass filters are connected to corresponding single-phase transformers, each having an output winding. The output windings of the single-phase transformers are connected to one another in a Y-circuit configuration to produce the output AC voltages, having a grounded neutral terminal. Each of the single-phase inverters is controlled by an associated pulse control device which contains a vector-oriented control device and a control unit. A vector oscillator generates signals corresponding to a symmetrical three-phase system of reference vectors for the vector-oriented control devices.

Abstract: An inverter arrangement comprising two controlled three-phase inverters is disclosed. The inputs of these inverters are preferably connected to a common DC voltage source, while the output voltages delivered by the inverters are of rectangular waveshape and are added together by means of transformers to form resultant output voltages. In accord with the invention, in order to obtain resultant output voltages whose harmonics are of orders which do not change when voltage control is applied, all the output inverter voltages are caused to comprise in each period a positive and a negative voltage pulse, each of which pulses has breaks or no-voltage intervals of controllable width positioned at predefined places within the pulse.