tag:blogger.com,1999:blog-6585315345071147722.post8688745309192007790..comments2021-01-08T15:07:27.475-07:00Comments on Porsche 924 Electric Conversion: The Need for SpeedMicahhttp://www.blogger.com/profile/11579670342036433869noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-6585315345071147722.post-80531403281496001952013-09-19T19:16:00.595-07:002013-09-19T19:16:00.595-07:00There are 3 IGBTs in there rated for 400 amps each...There are 3 IGBTs in there rated for 400 amps each, so the theoretical max is 1200 amps. I can't remember offhand if that's continuous or not, but I think it is. The only problem is this type of IGBT is not naturally balancing, i.e. if one of the three is conducting more current and starts to heat up unevenly, the resistance goes down causing it to conduct even more current. The other problem is I don't know of any way to tell if one IGBT is hotter than another or how evenly they share the load. <br /><br />Right now I can easily increase the current to 833 amps without getting into some messy software modifications. That would still be okay even if one IGBT is handling essentially half the load, so I think I should be safe there. I intend to slowly creep up on that and see what I think. Micahhttps://www.blogger.com/profile/11579670342036433869noreply@blogger.comtag:blogger.com,1999:blog-6585315345071147722.post-14377356894974417062013-09-18T10:32:13.714-07:002013-09-18T10:32:13.714-07:00Great results. You're going about this the ri...Great results. You're going about this the right way, slowly ramping up your performance. You are also right about looking at the torque curves to pick a motor that matches the rest of your system (battery voltage, C rating, and your gear ratios). I also picked the 9 inch warp over the 11 inch, because I wanted the higher RMP limit and I was satisfied with the torque of the 9 inch curve. <br /><br />I started with a limit of 350 motor amps, and the car was sluggish. At 500 amps, I was getting back to stock performance. 750 amps was fun. At 1000 amps, the car is completely insane, and first gear is completely useless. In second the car jumps off the line much faster than it did with the stock gas engine. It is rare to draw high currents for any length of time. The peak current is only at the start and begins to drop quickly. I also rarely hit my limit of 170 motor volts (pack voltage is 192 V).<br /><br />So how high do you think you can turn up the current without risking your controller? I'm looking forward to your next update. Joeyhttps://www.blogger.com/profile/01042435434585986098noreply@blogger.com