Thursday, October 22, 2009

Contactor control and mods

It has been a little while since our last post, but lots has been done. When we commissioned the clutch at the garage we grabbed the contactor box to investigate interfacing it with the Tumanako inverter. The box had a few "nasties" in it - the precharge resistor was switched in across both contactors with IGBTs - no galvanic isolation, at any point!

Last week Phil and I put together a bit of a plan to modify it for increased safety and to interface it with the Tumanako inverter's STM32 chip. We removed the IGBTs and instead installed a third contactor (a Gigavac GX12 Phil had bought previously as a secoundary safety device, now becoming a primary safety device). With the HV circuit now sorted out all we needed to do was interface these 12V coils with the 3.3V micro. A circuit was drawn up, and a quick trip down to the local electronics store and we were ready. I put together the circuit on a strip of veroboard, and with a bit of Phil's coding we had a basic IO test clicking the contactors in and out.

This week I have tidied up the contactor box, mounting the veroboard circuit while Phil attacked the precharge code. We are nearly ready to try out a decent battery pack, and if that goes well we will have the chance to try out the Siemens motor.

This will be quite a milestone: race motor, race inverter and contactors. The car will be ready to spin it's wheels (under it's own power) for the first time.

Stay tuned!


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