I have measured ripple currents like this (or less) on 10-20kHz motor controllers. Often the DC side current ripple is not much more than the basic accuracy fo the current clamp. (Fluke i410 clamp and Fluke 110 true RMS meter together). On the order of 5A -10A. This is with DC input of 150-200A.
Seth Roger Stockton wrote: > > 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. -- vze3v25q@verizondotnet
