This is for you electronics engineers out there..
Now I'm getting frustrated. Earlier, I posted a message about theoretically having a controller with inifinte capability by simply feeding the output to a bank of however many MOSFETs to do whatever you wanted, so to speak. Well, I tried it, and it almost worked. I bought a DC to PWM Velleman kit from Jameco, and fed the output of it to an IRC1405 power mosfet. I copied looked at how the MOSFET was treated in the Velleman kit (it can output up to six amps), and did the same thing for the 1405- just a .47 ohm resistor from the drain to ground, a flyback diode from source to positive, and the gate going to the output of the PWM unit. My idea worked, if only briefly, as the 1405 when driving a 750 watt motor on the test bench would work for a while, then invariably overheat and fail, going to a full on state permanently. I tried putting two 1405s in parallel, and that assembly would just switch itself on and off at about 2Hz, then fail and go to full on.
(Why the IRC1405? Because of the listed drain-source amperage of 169A! At $2.95 apiece, I thought that would be some serious bang for the buck! I should have known it wouldn't be that easy.)
This is the bottom line: there's no controller out there other than the Navitas TSP-36 which has a 100A rating, and that specific controller has had a lot of problems; mine made the bike I was working on leap out of control and land on top of me. I would like to build my own controller which would be capable of 75 to 100A at 36V, but all the controller schematics out there max out at about 20A and they're usually H-bridge designs which are needlessly complicated for the brushed motors I'm using. All I need is forward, I don't need reverse, or brake, etc. I've opened the case on two chinese made controllers, both rated at 40A, and they both use the LM-339 quad comparator chip for something, I guess the PWM clock. These controllers look ridiculously simple on the inside; a lot of the circuitry is given over to the voltage regulation for the PWM part of the controller. Can anyone suggest a place for schematics for these things, or figuring out what I did wrong with my "hot rodding" idea?
In the meantime I'll hook the old "Yi-Yun" controller back up because I'm tired of the smell of burning silicon (probably pretty bad for me too.)