Re: [CAD_CAM_EDM_DRO] UPS to VFD hardware hack

Sven Peter wrote:

> Hello Doug,
> Sounds like a very usefull proposal. If it work out I will be one of the
> first ones to play with it. Sad that I am not an electronics but I will
> ask a neigbour who is development engineer at Numatics.
> It may take a few days to get an aswer.

If he is familiar with this sort of equipment, he will tell you there are at
least 3 reasons why it won't work.

1. Single phase motors with centrifugal starting switches don't work well
at reduced speed (the start winding stays on until it burns out).
The starting capacitor needs to be increased for lower frequency.

2. The motor voltage needs to be reduced in direct proportion to the
frequency.

3. The inverter usually has a transformer, requiring the same thing as #2.

Jon