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tcmtech
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Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/20/2011 4:30 PM

I have been processing scrap metals this week and one of the top priority things has been getting all of my old transformers, light ballasts, electric motors, old 6 volt and 12 volt DC generators, and vehicle alternators processed for their copper.

Over the years I have come to find that almost every Motorcraft alternator, Ford style, has an odd winding design. They have 12 pole rotors but the stator coils are wound in an oddly spaced 11 pole layout on each phase.

So whats the point or purpose or theory behind that design?

I have always assumed it was related to their less than fantastic voltage regulation and the natural tendency to be electrically noisy right from day one.
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garth
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#1

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/21/2011 7:12 AM

As the output is rectified DC I don't suppose they are to concerned about the AC waveform so long as it gives the result?

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mjb1962853
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Engineering Fields - Electrical Engineering - Analog and Digital Circuit Design Engineering Fields - Electromechanical Engineering - Transformers, Motors & Drives, EM Launchers Engineering Fields - Engineering Physics - Applied Electrical, Optical, and Mechanical

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#2

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/21/2011 9:43 AM

I believe this is a common practice to minimize "cogging".
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tcmtech
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#3
In reply to #2

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/21/2011 11:18 AM

I cant see where cogging effects would be of the least bit of a concern in a alternator driven by a vehicles engine.

Ford may have built a few pathetically underpowered vehicles over the years but they were not that bad!
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Andy Germany
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#5
In reply to #3

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/21/2011 2:45 PM

Cogging can cause vibration, maybe they have found that "not" cogging increases the drive "V" belt life, for example - just a possible guess.....

Some cars use the Valve toothed belt and extra vibration is certainly not a good idea there......

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Andy Germany
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#4
In reply to #2

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/21/2011 2:42 PM

I believe you are right.....

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cuba_pete
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#6

Re: Odd Alternator Winding Configuration, 12 Pole Rotor 11 Pole Stator

03/24/2011 11:15 AM

This is an example of an inductively loaded alternator. Synchronous (matching rotor/stator configurations) alternators would experience a reversal in the fields of flux each time the rotors pass the stators. Inductive alternators only have flux flow in one direction.

The inductively loaded alternator experiences less magnetic loading, which reduces the effort required by the engine to turn it. A small loss of power at the output is offset by the reduced energy needed by the engine to turn it.
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Andy Germany (2); cuba_pete (1); garth (1); mjb1962853 (1); tcmtech (1)

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