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Old May 22, 2016, 02:34 AM
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Figure erpm?

For a 12'tooth and 14 magnet motor. How do u do it ?
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Old May 22, 2016, 05:16 PM
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Rpm x magnet pairs. So rpm x 7
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Old May 22, 2016, 08:22 PM
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Jack
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What is erpm?

Jack
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Old May 22, 2016, 08:34 PM
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Electrical revs per minute. How many comutations the esc does per motor rev I think.
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Last edited by Hummina; May 22, 2016 at 08:46 PM.
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Old May 22, 2016, 09:22 PM
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That is what we also call cogging steps I think, you can get those from the Winding Scheme Calculator here:

http://www.bavaria-direct.co.za/scheme/calculator/

For a 12N14P motor it is 84 cogging steps.

Jack
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Old May 23, 2016, 12:09 AM
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1 mechanical revolution is how far a rotor turns in order to get back into the physically identical position it started in. This is always 360 degrees.

1 electrical revolution is how far a rotor turns in order for it to get back into the magnetically identical position it started in. If there are only 2 poles on the motor, then the rotor will make a 360 degree rotation before the north and south poles are in the same position they started in. If there are 4 poles then the rotor will be magnetically in the same position after only 180 degrees. If there are 6 poles, then it will be 120 degrees and if there are 8 poles, then it will be 90 degrees.

This means the electrical RPM's is always the number of pole pairs times the mechanical RPM's.

Note that this is different than the number of commutations per rev and different than the number of cogging steps. In a "6 step" (trapezoidal) control, there are always 6 commutation steps per electrical revolution. And the number of cogging steps depends not only on the number of magnetic poles but also on the number of stator teeth.
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Old May 23, 2016, 12:25 AM
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So for our 12x14 motors one rpm is 7 erpm.
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Old May 23, 2016, 08:26 PM
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Yes, that's correct.
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