the input side of the phase-shifting transformer for each power supply module, phase-shifting transformer secondary winding divided into three groups, based on the voltage level and module series series, generally by 24,30,42,48 pulse series constitute a multi-stage phase superimposed rectifier, can greatly improve the current waveform (grid-side voltage and current harmonics indicators meet the requirements ieee519-1992 and gb / t14549-93's) side of the net. net side power factor close to 1 to make it load without any power factor compensation, harmonic suppression device. since the independence of the transformer secondary windings, so that each unit of the main circuit power is relatively independent, similar to the conventional low-voltage inverter, facilitate the use of existing mature technology.
the output side of each unit by the u, v output terminal connected with each other from star connection to the electrical power supply, with each unit through restructuring pwm waveform obtained stepped sinusoidal pwm waveform. sinusoidal waveform is good, dv / dt / small, cable and motor insulation no damage, no output filter, you can extend the output cable length can be directly used for general motors. at the same time, greatly reduce harmonic losses in the motor, eliminating the mechanical load and drawn into the blade vibration.
when one power module fails, by controlling the output terminals shorted, this unit can bypass exit system, the inverter can run derating machinery; thereby avoiding downtime caused by the loss of many occasions.