zombiess
10 MW
ZOMGVTEK said:I'm all for trying out new ways to get stuff done. It's just an interesting choice.
I decided to make an 18 FET TO-247 controller about a week ago, and managed to blow it up already. The remains are sitting in a pile, along with the 4 other 15 FET controllers I destroyed by doing dumb things. I still have another 15 FET with 250V FET's that I need to blow up. It's also possible it could actually work at 48S, but unlikely.
I'm armed with some new knowledge, and I'm going to try and make a snazzy 18 FET 150V power stage over the next few days. From everything I've come across people on here doing, it would be the best 150V controller available, and I'm fairly sure I can get it done for about $40-50. I have $20 invested in snubbers, the rest I managed to acquire at no cost.
This is somehow the only picture I managed to take. I have 18 hand picked TO-247's, matched by Rds(on), and a .75 x 1" copper bar to mount them on. I have the PCB mostly designed, I will try to etch it tomorrow. If you sip the datasheet koolaid, it will be good for about 500A phase current. I plan to run no less than 300A phase through it. I'm torn between making a copper slab based waterblock, and just using a big damn heatsink and a thermally switched ducted fan. This thing is probably going to weigh 10 lbs, but it will hopefully be robust.
My choice was because it was off the shelf and quick, something I need since I can't machine nor do I want to at the moment, but am going to be working with etard soon I hope, just need to do a new circuit board layout which I've started.
So what were your setups that was caused you to blow up FETs? Were you extending the leads in a bad way causing ringing on the gate?
Nothing wrong with forced air cooling and a large heat sink. I hope I don't pop my setup, but I'm starting off small and at lower currents and will be scoping the gate signal as I go to see what's happening. I feel pretty confident in my design as long as I haven't made any major PCB error which I'll double check when I get the boards in hand hopefully tomorrow or Thursday.
BTW, never ever sip the Kool Aid, they are Liars and written by Jim Jones... Ok it's not that bad but lots of reading has helped me learn how to intemperate them better. I always assume I'll have the worst RDSon and then add a little. I'm no power control wizard by any means, I just picked FETs based off of specs of ones I knew worked OK IRFB4110's and replaced them with ones that appear to be really close in spec IRFP4568's to drive. The biggest concern I have on my setup is my longish gate traces to the top most FET banks, but I was told I probably won't have a problem due to the lower switching frequencies used in these controllers. I'm still going to scope it to make sure though.
I also try to be very careful with wiring and insulation to prevent shorts. That's just from years of experience jury rigging wiring together only to be bit in the ass because I didn't take the time to do it right. It's why I have something like 30 hours of modification work into my 18FET 4115 controller, the devil is in the details and he takes credit cards if you screw up!
I really can't wait to get my bicycle back with the Hubzilla installed and then get this controller built to test on it. This is just the first testing step of my future compact 24-36FET mega controller if it works (already have the 6 gauge wire in stock, but I think i'm going to be needing about $1500 in Nano tech Lipo for one of my future projects). I dream big, but start small and take baby steps since I'm just learning.
BTW, please be careful when dealing with high voltage like this. I don't know what your background is with electronics or electricity but this goes for everyone including myself. You can't be too safe when dealing with the voltages we are talking about in this thread, one mistake is all it takes with a high voltage lipo pack to do you in. I often wear gloves and safety glasses when making my first connections on new stuff. My one single KFF spooked me and it was very very minor and 100% my fault. Just glad there was no damage, just a flash and a little smoke, but shorting out 30S3P could have been pretty bad if the fuse wouldn't have popped (it vaporized most with no damage to the holder).