Well logic is still kind of being decided on since I'm trying to decide on a how and when to change frequency and amps based on my inputs. Plus the original sheet I'd found that detailed the initial construction was 1 year ago and I lost track of time and hadn't found it.
I'm using a pic chip to variable PWM output at 3 times the AC frequency I wanted, after that I think it put that through a capicitor and some filters to smooth it a bit. It wasn't quite a smooth AC wave but supposedly was good enough. Then it had some 'counters' ? My electronics knowledge isn't too good, I can read a diagram and solder but never really sure why I'm doing what I'm doing, etc. Anyway I believe it used 2-3 transitors, maybe one was an SCR and it basically was able to count pulses in the PWM and only actually let every third one through. It had three of these each 1 count seperated and generated the correct phases.
I can't remember I really have to find that document.
I understand 3 phase and being 120 degrees apart and polarity reversal. But when I meant was that with 2 leads from single phase AC I can picture the Sine wave and know when polarity between the leads will reverse, etc, but if you have 1 lead each from the 3 phases all connected together then what happens ? Wouldn't there be some cancelling? Would any given leg be able to switch the polarity and 'pull' to the same height trough as peak?
with the 3 phases, they aren't equal but opposite at any given time. they don't reach peak at the same time nor do they cross zero at the same time. actually, one phase leads the other and causes the rotating action. in a single phase motor, you need a phase shifting cap to get the thing spinning. in a 3 phase motor, all you have are windings which further simplify the motor. so at any given time you have one phase going high and one going low and one in the negative which rotates the shaft.
you are thinking of it more like a center tapped transformer where the voltages are equal but opposite which isn't the case.
I have also put a very cheesy paper drawing to kind of show the wave form and the motor degrees for you. they are not to scale and are very poorly drawn. I do apologize for that. I don't really have time right now to look it up on the web as I am at work and should be working.
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