barry995 said:
I guess I should clarify a few things. I am using a sold state rectifier
What sort of rectifier are you using then?
Valve?
Mechanical commutator?
I hope it's a solid state rectifier with schottky or silicone diodes.
not designing my own and the dimmer I have is an old style pot, not a modern PWM that has zero crossing detection etc.
That dimmer won't work on DC, it's designed for AC!
I redrew they way I want to connect it in my circuit to vary the DC voltage supplied to my output FETs, hopefully it is a little clearer.
Did you actually look at the datasheets for the components you're planning you use?
Look at the datasheet for the LM78XX series regulators - they will be cooked on 160V DC!
Thanks Hero for catching my duty cycle error, I had it in my head that I wanted a 50% duty cycle.
Your motor is designed to work on 50Hz or 60Hz (we would know the frequency if you filled your location in) AC with an RMS voltage of 120V. Your square wave will produce an RMS of 160V which is far too high. Excessive currents will flow in your motor leading to core saturation and eventually smoke, fire and a dead motor!
I am actually getting a severely reduced duty cycle out of my 555 timer at low frequency. I think if i eliminate the flip-flop and with some tuning I should be there.
The duty cycle needs to be reduced even more at lower frequencies because your AC motor is not designed to be run at anything lower than the rated frequency therefore more current will flow at lower frequencies; to prevent this you need to reduce the duty cycle considerably. This is done by pulse position modulation; you keep the pulse lengh equal but increase the time between pulses.
The chances are your single phase motor won't work with a variable frequency dirve because the starting mechinism is probably frequency dependent. You might have some luck starting it at full speed then reducing it down to a lower speed and maybe you could go as slow as half the speed but no lower.
Why don't you buy a three phase motor and a variable speed drive that will work from a single phase supply? No offence intended but judging by your past posts you don't have enought experiance to attempt a project like this.