Hi Guys,
Ron, I am a novice in the use of FETs but not with working with high voltages.
I was an electrician for 30 years, both industrial and domestic, so I have a healthy regard for the invisible stuff!
I am trying to slow down a 20,000rpm 230v 0.22hp universal motor. I have already geared down the output by pulleys but my biggest and smallest pulleys still give about double the desired rpm. Most speed control circuits use AC and then DIAC/TRIAC combinations, but I don't have any DIACs unless I can find an old board with one on. The holidays are not helping buying things.
I do have the 600v N-FETs though so I thought why not rectify the AC and PWM the FET on the low side. This is when my knowledge of FETs let me down. I have used them before for the odd PWM LED circuits but never above 30v or so and cannot understand the correlation between required gate voltage/current to source/drain voltage/current, if there is one.
My basic question is just that. Is there a formula or rough guide I can apply and understand?