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Old 05-22-2010, 09:16 PM   #3410 (permalink)
harlequin2
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Join Date: Mar 2010
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I'm told that the LS is derived from the old Curtis 123-something. I think it used MOSFETs originally, but this version has 24 x 600v x 78A IGBTs in parallel. Its the 1000A, 156V model.
The control board doesn't use a micro, just a large number of comparators and op-amps and the current sensing is just a diode off the IGBT collectors. That was disconnected in my one, by the way. It had a resistor missing from the control board that was needed to make it work. When I did connect it, it behaved very erratically going into current limit as soon as the throttle was opened. I guess they couldn't get it to work either! Also, the thermistor that is supposed to provide overheat limiting was replaced by a fixed resistor. So, no current limiting and no thermal control - no wonder so many of them have blown up.
I played around with the current sense and fitted a low pass filter to stop the spikes from causing it to shut off and it now works quite well. Also fitted a thermistor and that causes the PWM frequency to drop from about 13.5 kHz to 4 kHz when it gets hot. Hopefully, it is now more reliable than the original.
I am toying with fitting your controller board with the Hall sensor instead, but I'd have to redesign the layout to fit in the case.
How's the ac controller coming along?
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