Converter for symmetric feeding of three-phase load - with each phase current provided with its own regulator unit

摘要

The converter for feeding a three-phase load (4) incorporates a rectifier (1) fed from the grid, a capacitive intermediate circuit (2) and a transistorised inverse rectifier (3). The phase voltages (U1,U2,U3) formed at the output of the inverse rectifier are adjusted for its transistors by means of a pulse-width modulation control unit (5). The converter is characterised by the following facts: (a) each phase current (i1,i2,i3) is provided with its own regulator (7.1,7.2,7.3), and the same target value of the phase current can be assigned for each regulator; (b) each regulator (7.1,7.2,7.3) has a setting unit (8.1,8.2,8.3) for amplitude modulation of the corresp. phase voltage (U1,U2,U3) with the phases of these voltages set by the unit (5) at 120 deg. to one another. The three phase currents (i1,i2,i3) are equalised by adjustment of the amplitude of the associated phase voltages (U1,U2,U3). The converter is used to symmetrise the currents in three-phase magnetic stirrer, especially a continuous casting stirrer or a mould stirrer. It is used also for symmetrisation of the currents in a linear stirrer. USE/ADVANTAGE - In the metallurgical industry, for example. It allows the phase currents to be symmetrically distributed in the case of asymmetric load impedance.