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Old Jan 03, 2012, 12:25 PM
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Moab, Utah, USA
Joined Apr 2003
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Quote:
Originally Posted by Mark Wood View Post
It's also obvious that there is NO ac current but pulsed dc.

mw
Actually, the pulsed DC does create an AC current through the motor windings. The scope traces that Ron posted display represent the voltage applied from the ESC to the motor, not the current flowing through the motor windings. I have attached a photo of a scope trace that does represent the current through one pair of windings on a brushless motor. The center horizontal line with the hash marks represents zero amps. You can clearly see that the current flow is maximum in one direction (trace is above the zero reference) for 2/3 of the commutation cycle and the current is zero for 1/3 of the commutation cycle. During the next commutation cycle the maximum current trace is below the zero reference indication that the current is flowing through the coils in the opposite direction, i.e. AC current.

Larry
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