Victor Tikhonov [mailto:[EMAIL PROTECTED]] wrote:
> If you draw PWM 200A pulses 50% duty cycle (like > 200A-0A-200A-0A every 100us or so), the average current is > 200*0.5=100A but your analog movement meter may show 60...70A. > > A good way to check is to connect a scope to the shunt and > get the average voltage reading ar some load. Divide it by > shunt resistance > and you'll get the current your analog meter should show. With modern high-frequency PWM controllers, the battery current is not as described; in the example Victor suggests, the battery current with your DCP controller should be pretty much 200A with perhaps 20A of ripple at the 20kHz (or so) switching frequency (actually, 50% duty is the worst case scenario, so the ripple might be a bit higher % of the average under this case and better everywhere else; Rich or Damon will know for sure). The big current spikes are sourced by the controller's bus caps so that the battery sees essentially only the average current; this is one of the big advantages of modern high-frequency PWM controllers over low-frequency ones such as the GE EV-1 SCR controller (switching at 50-300Hz, Victor's description is right on the money for it. Your analog meter isn't likely to respond to the ~20kHz ripple on the current signal anyway, so its inaccuracy may be inherent to the meter or shunt that feeds it. Cheers, Roger.
