On Wed, 30 Dec 2009, Craig Haynie wrote:
When the power to the controller is switched off, no induction is measured in the stator coils. Why? Isn't this how a generator works?
Ferromagnetic materials are nonlinear. If their operation is kept well below the saturation region, then yes, a motor must be a generator. But if the combination of drive current and PM magnet fields cause the core material to approach saturation, then the simple motor-generator rule no longer applies.
By moving a magnetic field across a conductor, don't we get induction, and hence, electricity?
Not in a toroid inductor with unsaturated core. The ring-shape core will shield the inductor against fields coming from nearby magnets. But if the combination of drive pulse and PM magnet's field are causing the toroid core to leave the linear operating region, then the generator effect can only exist during the drive pulses.
It's similar to how flux-gate compasses work. (((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-762-3818 unusual phenomena, tesla coils, weird sci
