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Old Sep 09, 2011, 11:44 AM
matttay is offline
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It was this thread:

http://www.rcgroups.com/forums/showthread.php?t=551079

The peak versus average occurs when you are just starting up an electric bike (220 pounds AUW including rider in this case), for example. In the attached graph, there are the following curves: Green is the max phase currents (all 3 phases recorded) during PWM on. It's a bit noisy, but I've since cleaned up the ADC readings and verified by manually reading across 3 ohm sense resistor. It is indeed around 160A.

But the inline fluke (in this case) is reporting 29A.

However, look at the duty cycle, which is the middle ramp trace. This is duty cycle ranging from about 25% to 40%. The very bottom ramp is RPM. And the blue is bus voltage.

Now, the phase current reported is the MAX during the on time. So it's a bit pessimistic compared to RMS.

But this is another indicator that inline meters at partial throttle are miles away from what is actually happening. In this particular case, I'm learning that a 100A startup current when duty cycle is low can mean 1000A peak inductor current for 10's of uS if you are trying to start quickly.
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