Victor Tikhonov wrote: > Fine. All these details are obscuring my point that there is > a variable - frequency - applicable to AC motors only.
How about a "brushless DC" motor, like a computer fan? They are actually AC motors, with an electronic commutator. There is no frequency input, and they run at a speed determined by load and the voltage applied. How about the induction motors in your furnace, window fan, or ceiling fan? They all run on fixed 60 Hz AC (no frequency control), yet are variable speed just by varying the voltage to them. Frequency applies to DC motors, too. The coils all have AC or pulsating DC flowing in them, produced by the commutator (mechanical or electronic). Higher frequencies = higher speeds. Unipolar stepper motors, for example; coil current is pulsating DC (one polarity), and the repetition rate determines speed. -- Lee A. Hart Ring the bells that still can ring 814 8th Ave. N. Forget your perfect offering Sartell, MN 56377 USA There is a crack in everything leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
