View Single Post
Old 10-07-2011, 01:20 PM   #590 (permalink)
EcoModding Lurker
Join Date: Aug 2011
Location: Michigan
Posts: 32
Thanks: 3
Thanked 29 Times in 10 Posts
Originally Posted by energymiser View Post
Hi Collink. Saw the video. Did you figure out why the big motor didn't want to go?
I knew better than to try running the big motor but we did it anyway. The Siemens motor has like 0.1 to 0.2 ohm resistance windings. At start up there is no back EMF and so the windings will draw whatever your V/Winding R is. At the 100 volts I could supply that would equate to a start up current of 500 - 1000A. I had 200A surplus used IGBTs installed and no capacitor bank. This was not a smart idea. So, for future reference, don't try to start a motor with underpowered used transistors and no capacitor bank. I think that's why it rapidly went down hill. I've since rebuilt things (ack... I had blown two VLA500 boards, 1 IGBT module, 3 diodes, and one resistor) and I'm installing the capacitor bank and precharge system now.

I checked out the BG2A driver boards and Digikey wants $187 for a kit c/w 2 gate drivers. I am hoping to do better than that. I think I saw someone posted the schematic for the VLA500 gate driver, I'll keep looking.

I need to get started building something, so I will start with the driver boards. The parts price including the boards is where I'll start to see how much cheaper it can be done.
Mrbigh has the driver boards I was using in the video. He sells them for a very fair price. Ask him about it. I do have the schematic for the boards and I'm pretty sure I'd be allowed to post it. Could either Paul or Mrbigh confirm that?

BTW, the VLA modules are $43 a piece so 43 * 2 + like $5 in other parts plus the PCB from mrbigh and you are still looking at a little over $100 a driver board (and, obviously you need three). So count on like $350 for the driver section.
  Reply With Quote