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Old 12-09-2015, 10:49 AM   #2458 (permalink)
MPaulHolmes
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Oh dear, I made a mistake in my figgerin'. I was thinking I had line to neutral voltage from the DC bus, but it was line to line voltage. I better go re-figger and see what happens. haha

Crap, so the 3 phase bridge can make a LINE TO LINE voltage of -DC Bus to +DC Bus. So, the LINE to NEUTRAL voltage can go from -DC Bus / sqrt(3) up to +DC Bus / sqrt(3). So, the 3 phase power is then...

Code:
power = DCBus / sqrt(3) * peakPhaseCurrent * sin(0) * sin(0) + DCBus / sqrt(3) * peakPhaseCurrent * sin(0) * sin(0) + DCBus / sqrt(3) * peakPhaseCurrent * sin(120deg) * sin(120deg) + DCBus / sqrt(3) * peakPhaseCurrent * sin(240deg) * sin(240deg)

power = DCBus / sqrt(3) * 1.5 * peakPhaseCurrent
power = DCBus * sqrt(3) / 2 * peakPhaseCurrent
power = DCBus * sqrt(3/2) * rmsPhaseCurrent

So, after the boosting, let's say we have a 700v DC bus, and 50ampRMS phase current.  That means:
power = 700V * sqrt(3/2) * 50ampRMS = 42866Watt. 

So, the DC bus current is sqrt(3/2) * 50ampRMS = 61Amp
So, the battery bus current is 122amp, so the current through the inductor would be 122amp.  

The RMS current in the boost switches is 3 times the rms phase current, so is 150amp.  At the moment, there are 2 high and 2 low boost switches, so they would have to do 75ampRMS each.  Maybe there should be 3 high and 3 low.
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Last edited by MPaulHolmes; 12-09-2015 at 11:34 AM..
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