15 May 2008

Investigate - motor controller

This motor controller has temperature limit, motor current limit, and low voltage shutoff settings set at the factory. It will handle 600 motor amps peak and 200 amps continuous. Maximum voltage is 144 nominal. Low voltage cutoff is XX. Temperature limit is XX.

I wanted to adjust the limits to better suit my setup, but there is no documentation on that anywhere! So what do I do? I open it up for a peek of course! Undoing all the screws around the case, it is siliconed closed. After prying it open, I find a large power board and a little control board inside. I'm an EE and interested in motor controllers, so I immediately identify most of whats going on. The large blue parts are computer grade aluminum electrolytic capacitors. I can identify the push-pull gate drivers, temperature sensor, current sensor, and various chips on the control board. I can see 3 multi-turn potentiometers used to fine tune adjustment points along the end of the control board, but there is no labeling as to what each does! There is another single turn pot farther in on the board that I only guess adjusts the switching frequency. I'll have to get out my multimeter and keep dreaming of an oscilloscope while I try to figure out what the pots adjust.

One complaint I have with these controllers (pretty much all of them except the Zillas) is they use the high voltage as a reference for any signal input/output. Sure it only takes 12V to enable the controller, but it's referenced to the high voltage negative! They should include built in isolators or relays so that the low voltage signal lines are isolated and easier to interface with. I've added my own relays to this controller. One for enable, and one for it's fault signal.

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