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Old 10-03-2010, 11:32 PM   #24 (permalink)
NiHaoMike
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Quote:
Originally Posted by ConnClark View Post
Ferrite and powdered iron cores won't hold at 100,000 rpm. Also high frequency switching supplies greater than 200K typically use a buck or boost topology where the current flow remains relatively constant and doesn't switch direction.
The stator (made of ferrite or powdered iron) does not move. As such, for a switched reluctance design, the polarity of the stator could be changed so the rotor always sees the same direction of flux.

And some buck converters do have current rapidly reversing through the inductor under certain conditions. It is done to make the output noise more predictable by eliminating "period skipping" operation. Losses do increase but they're insignificant under load.
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