Espritmodel.com Telemetry Radio
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Old Apr 07, 2014, 02:51 PM
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p901P901's Avatar
United States, CA, Lancaster
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Help!
Pulse on battery power

On a YEP 100 amp I am seeing a pulse on the battery terminals that is just about the same rate as the timing set on the controller.
At first I thought I was seeing the FET switching then since it was similar with the clock pulse , this could be what I am seeing. The pulse stays at the same frequency during acceleration but the amplitude changes from about 1 v p-p to about 2v p-p.
Could this be just a problem with one phase?
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Old Apr 07, 2014, 04:38 PM
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Bruce Abbott's Avatar
Hastings, New Zealand
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Looks like PWM switching noise. Why do you think it's a problem?
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Old Apr 07, 2014, 05:02 PM
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It just seemed odd that I would see this waveform on the battery side.
I was looking to see if there was a noise problem with these ESC's. I seen this and the next to see if there is a filtration problem with the controller voltage rails. It just seemed odd that I would see this waveform on the battery with some extra .1uF caps installed.

Bruce could you check out to see if I am getting it right on the YEP 150's http://www.rcgroups.com/forums/showp...&postcount=193. report 193 to 250

Thanks
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Old Apr 08, 2014, 01:19 AM
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Bruce Abbott's Avatar
Hastings, New Zealand
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Quote:
Originally Posted by p901P901 View Post
It just seemed odd that I would see this waveform on the battery side.
Depending on the load it could be quite normal.

In the other thread you say that your setup can exceed 150A static. Your scope image is too small to see clearly, but the waveform appears to show a step of about 0.5V on the rising and falling edges. Your ESC has two Rubycon ZLH 470uF 35V smoothing cps, right? If you were running part throttle and the motor current was 50A, then each cap was passing ~25A peak and must have an ESR of about 20 milliohms (0.5V/25A).

According their specs those caps have a maximum ESR of 28 milliohms, so it would seem that they are working correctly. To reduce the ripple voltage you simply need to add more caps.

Quote:
seemed odd that I would see this waveform on the battery with some extra .1uF caps installed.
The ESC already has almost 1000uF across the battery leads, so another 0.1uF won't make a perceptible difference.
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