Re: [CAD_CAM_EDM_DRO] VFD problems with my Bridgeport CNC..

Peter Reilley wrote:

>VFD's are terrible at handling surge loads. When driving a 3 phase motor
>you are
>supposed to connect the motor directly to the VFD without a switch. You
>use
>the VFD to bring the motor up to speed. This is not compatible with using
>it to power the other loads. You could use two VFD's, one for the spindle
>motor
>and another for the rest of the machine. Obviously, the VFD powering the
>rest of the machine would be fixed at 60Hz.
>
>

This might actually work if you constructed a filter to remove the
400 V square pulses that the VFD uses to simulate a varying voltage
sine wave. Without such a filter, any transformer will overheat very
quickly with both hysteresis and eddy losses from the high-frequency
high-voltage pulses. I know of no VFD manufacturer that suggests running
any equipment but an induction motor from them. They all seem to warn
not to power any transformers of any type from a VFD.

Jon