View Single Post
Old 09-17-2013, 09:26 PM   #6229 (permalink)
EcoModding Lurker
Join Date: Jan 2012
Location: Gilbert AZ
Posts: 20
Thanks: 1
Thanked 17 Times in 8 Posts
Hey, I learned a fun lesson the other day with my IGBT version of the controller that would be applicable to anyone with this controller. I never adjusted the deadband in the throttle position. I also use a limit switch on the pot box to control a contactor on the B+ side of the controller. As I figured out recently, the PWM duty cycle starts to rise a teeny tiny bit before the switch clicks. I drove my car for 3 months like this without noticing it until one morning I was trying very slowly ease onto the pedal to back down my driveway when all of a sudden the wheels spin out and leave a foot of rubber on the concrete! Lucky for me, the IGBTs were able to handle this short burst of current, so my controller is still intact. The reason that happened is I pushed the throttle to the point that the controller was trying to supply current to the motor. Since only 1/4 amp is available through the precharge resistor, the control loop kept increasing the duty cycle. When the contactor finally closed, whatever the duty cycle was at resulted in enough current to spin out the wheels before either the controller shut it down or I took my foot off the pedal.

So let this be a warning to all of you to make sure the deadband is properly adjusted on your controller, especially if you have a limit switch operating a contactor like I do!
Electric Porsche 924 Converted using an IGBT based Paul and Sabrina Controller
  Reply With Quote