Bit of help with the Kollmorgen...

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LinkOfHyrule's picture
Last seen: 14 years 5 months ago
Joined: Wednesday, October 17, 2007 - 14:54
Points: 730
Bit of help with the Kollmorgen...

I'm working on an EV project right now. Kind of like an electric skateboard (mebbe with a removable seat, haven’t decided), but much bigger, heavier, and more dangerous. Fun stuff.

Anyway, it started with me buying some Kollmorgens off of eBay. It has since taken only vague shape, and probably will not be completed for a while (namely until I get me a decent MIG welder, or a friend of mine lets me use his). Right now it consists of little more than some motors, batteries (still need more), and various connectors. The sheet metal and other raw materials I should get in a while.

With the four Kollmorgens I plan to put in it it should put out about 1600 watts. While this is quite a bit of power to play with, I do plan on racing this thing. I want to use an external controller with the Kollmorgens. This poses a bit of a problem, mostly on how to go about it. I could just buy a brushless controller, but I really don't want to spend that much money, especially because I might need two.

Option two is rather more difficult. I could keep the motor controller intact and use the phase outputs and hall wires to drive higher power components. This would almost undoubtedly require I use voltage regulators so I don't fry the brains of the controller, not to mention getting a lot of FETs to replace the stock ones. However if the old FETs (I haven’t taken out any of the potted controllers to spec out the parts) can handle more than they are being used for, this might not be too much of a problem. Seems unlikely that they could, but if someone could tell me for sure, that would be great. I think this might be the most wallet-friendly solution, so I'll be trying it out on a extra motor just to find out.

My last idea is a little more exotic but I like the concept: If I could find a chip that would take the signal from the hall sensors and use it to drive some FETs, I could essentially make it work just like a brushed motor, and use a PWM controller to control the speed. However, I don't have the slightest idea where to find such a chip. I have seen a few that do this, however they are basically the entire controller on a chip, and therefore more expensive. In addition, I will certainly be messing with the voltage input, and if the chip and the FETs will not accept a (really) wide voltage range, the whole idea falls apart.

Basically, I need a few ideas (and possibly instructions) on how to go about converting the Kollmorgens to external control.

If anyone can help me with finding some useful parts (chips, controllers, FETs, etc.) I would really appreciate it. I'm not a electronics supergenius, but I do have a fair bit of experience with this sort of thing. More than the average Joe, at least.


P.S. What would you guys recommend as the max power rating on these motors? Could they handle 2,000 watts? I can attach the things to a water cooling system, so heat isn't really a problem, but I don't want the magnets cracking or anything.

Fechter's picture
Last seen: 14 years 11 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
Re: Bit of help with the Kollmorgen...

The Kollmorgen motor internal controllers are pretty much at their limit in the stock configuration. You can't push over 24v. Even at 24v, they had a habbit of blowing.

To run an external controller, it's not too hard to separate the internal controller wires and bring the hall and phase wires out. Trying to boost the output of the internal controller could be an option, but is nearly as much work as building a whole controller. The wiring is documented in some posts somewhere around here. I can find it.

With an external controller, those motors could probably take 600w or more and something like 1200w for short bursts. The rotor flies apart somewhere around 60volts. You can run them at 48v. Any kind of cooling will increase the long-term power rating. For 1 minute bursts, the windings are the limiting factor.

Each motor needs it's own controller. It may be possible to run two off a single controller if the shafts were locked together and at exactly the right angle. I wouldn't recommend this.

If you're cheap (like me), you could look for blown brushless controllers and repair them. Another option would be to get a cheap chinese brushless controller and upgrade the FETs and caps. I think I've seen some for around $25 that could be boosted. Since you can't run over 60v without exploding the motor, you could use 75v rated FETs, like IRFB3808's. These can handle around 50 amps. I have a Crystalyte controller that uses them in pairs and I can peak at over 100 amps on acceleration. IRFB4110's are better, but more expensive.

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