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I realise that; but the pulse-delay method is somewhat different in that it is synchronised with the internal commutation.
The article you linked to mentions [instantaneous] current being greater because the back-emf is less at lower speeds, but in the experiments I did I found, surprisingly, that instantaneous current was not significantly different as speed changed. Unexplained, but useful. Maybe I was just lucky with the guinea-pig motors.
Previously-published speed controllers for BLDC motors require access to the individual coils of the motor to vary the coil drive, and involve either dedicated ICs or microcontrollers together with optical or back-emf rotor-position sensing arrangements
Can't explain why the instatanious current wouldn't be higher since the back emf subtacts from the supply voltage. Of course the ESR and inductance limits the rate of rise so maybe fan motors handle it a little better that the bigger motors with no protection against a stall.
I also like it because it will be hard to stall so if the voltage gets to low it will still limp along. Seems like it should also add a small amount of constant speed control.
@ronv
Thanks. I'll edit the article to clarify that the previously-published methods aren't the only known ones. Apart from PWM there is, of course, the voltage-reduction method used in the OEM controller.
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