I took apart a DC motor of questionable quality and I noticed that it uses only one permanent magnet. Basically a round cylinder covering the whole circumference of the steel can that it sits in. How can this work? I thought you'll need two permanents, one with the polarity N and another S to produce a consistent magnetic field. Can anybody tell me if these motors were designed badly or maybe somebody can educate me on how it can work. Thank you.
Single PM DC motor
Dec 16, 2004
4 Replies
Thanks John. Is there any drawback to use such magnets? Any correlation with electrical noise generated by motors equipped with such magnets?
Corey
John Woodgate wrote:
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I read in sci.electronics.design that snipped-for-privacy@yahoo.com wrote (in ) about 'Single PM DC motor', on Thu, 16 Dec 2004:
It's magnetised across a diameter, so that one spot on the surface is N and the opposite spot is S. You can even get quadrupole magnets, which have N-S-N-S at 90 degrees around the circumference. This is especially so with ferrite magnets, because they have a very high coercivity. Without that, the magnet would gradually weaken.
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
wrote
Please don't top-post. :-) Any rf noise you're getting is most likely from the brushes, assuming of course that there are brushes.
I read in sci.electronics.design that snipped-for-privacy@yahoo.com wrote (in ) about 'Single PM DC motor', on Thu, 16 Dec 2004:
No. Electrical noise comes form commutation, whether by a mechanical commutator or semiconductors.
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
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