Quote:
Originally Posted by thingstodo
...On the agenda for tomorrow - power the inverters from separate 12V batteries, verify that the inverters can be connected in series to get about 280 VDC, and connect this voltage up to a test VFD to ensure that it powers up as it should.
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Progress, but not all the progress I was hoping for.
I got the two DC to AC inverters powered from separate batteries. They are now isolated, so I put them in series and I got 281.2 VDC from them. The inverters are taking in from 0.9A to 1.1A at 12.5 VDC. I have not figured out where the variations in current come from. The cooling fans spin up when power is applied, but they stop almost immediately.
I ran into a bit of a snag.
The VFD that I will be powering has a pre-charge resistor on the AC input, but not on the DC bus. I need to rig up a power switch, a pre-charge resistor, a fuse and a bypass contactor to connect the high voltage DC to the VFD.
The pre-charge resistor limits the current drawn by the VFD to charge up it's capacitors when DC is applied. The bypass contactor 'short out' or bypasses the pre-charge resistor after the capacitors have charged up. This allows full DC current to the VFD.