Last week I found out how to adjust the speed of a universal motor; thanks to the members of the forum.
Can I fully rectify an AC wave and then PWM the resulting DC, at a frequency of approximately 30 kHz to adjust its speed? Would this be inefficient? Or would it even work?
Thanks
Tom
P.S When something says 240VAC or 24VAC is that the Vrms or V peak to peak?
Of course it works. It also keeps the torque relatively constant at low speeds,
I'm assuming a nameplate. Yes, RMS. They also assume a sine wave input. Also remember that 120 VAC applied to a load, the load would dissipate the same number of Watts as if 120 VDC was applied to the resistive load.
For a DC motor and it should apply to a universal motor too:
Torque is directly proportional to current.
Speed is proportional to voltage.
a) A DC motor can act s a generator when unloaded and that voltage is proportional to speed
b) It's also proportional to Vmot = Vmeas - Imotor*Rarmature
PWM allows you to use the full amount of current and the voltage, hence speed, is related to the PWM duty cycle.