Monday, August 18, 2008

We don't need no stinkin' capacitors

One solution for the inrush shenanigans described in the last post is to construct an inrush limiting circuit with a large resistor and a contactor- the capacitor is charged through the resistor until the operating voltage is reached, when the contactor is closed, bypassing the resistor. The other way is to yank out the capacitor. The purpose of the capacitor is to filter the rectified AC mains supply so that it is a smooth DC source for the inverter. A battery is already a nice smooth DC source, so the capacitor isn't really needed. I already ditched the 20-plus pound inductor that was the other part of the line filter, so I had no qualms about getting rid of the capacitor. Luckily, the capacitor was its own easily removable module:
The other plus is now the inverter can be put in a much smaller box, and will have considerably less need for interior ventilation, making weather sealing a possibility.

Of course I tested the capacitorless inverter/motor setup the way my pappy taught me -- by revvin' er up real good a few times.

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