Insulated Gate Bipolar Transistor

Robiconfect Harmony line of medium voltage variable frequency drives uses a power circuit technology. In this circuit each motor phase is driven by multiple power cells that are connected in series.

Each cell is a static PWM power converter capable of receiving input power at 480VAC or 690VAC, 3 phase, 50/60 Hz, and delivering that power to a single phase load at variable voltage and frequency. The cells are constructed to 600 volt standards using 600 volt class components. The power cells and their secondaries are insulated from each other and from ground for 5 kV class service.

A power cell front end is a simple, six-pulse diode rectifier. The DC side of the rectifier is connected directly to the capacitator bank, while the AC side is fed by a dedicated secondary winding with approximately 8% source reactance. A compliment of power cells results in a secondary harmonic current spectrum much better than nominal six-step.

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