Re: [CAD_CAM_EDM_DRO] vfd

tom mazz wrote:

> Hugh,
>
> The VFDs do rectify input voltage to DC. The input can be single or 3
> phase. They then use a 3-phase bridge inverter to create a new 3 phase AC
> with varying voltage and frequency. The inverter uses pwm and the waveform
> is filtered to a smooth AC voltage.

Most VFDs do NOT filter the output waveform in any way. They just have
the power transistors connected straight to the output, usually with current
sensors on 2 of the lines. This is hard on the motor windings, as a lot of
voltage stress (400 V for a 230 V system, 800 V for a 440 V system)
is placed on the outermost few turns of wire.

Jon