Fine. All these details are obscuring my point that there is a variable - frequency - applicable to AC motors only. There is no frequency concept when you deal with supplying DC.
This is a distinction. For Ac frequency converter is outside the motor and solid state. For DC frequency converter is commutator and is inside the motor, so its "frequency" is directly tight to the motor speed while outside inverter for AC can vary frequency infependently of the shaft rotation. This is another distinction. Now, if you view motor AND controller/inverter as one black box as Lee suggested) with pure DC in - there can be no difference. Let's end this thread please. Victor David Dymaxion wrote: > > A shunt motor can act very much like an AC induction motor in this > regard. This is a reason they are popular for escalators, conveyor > belts, and elevators -- you give them more load and they hardly slow > down. Sometimes they are called "constant speed" motors. Putting more > voltage on a shunt motor doesn't speed it up, but makes it "stiffer" > against slowing down under load. > > Also, an AC induction motor does slip, and until breakdown more slip > = more torque (like a shunt motor!). > > --- Victor Tikhonov <[EMAIL PROTECTED]> wrote: > > Also increasing [AC] voltage will not > > make AC motor run faster. *You* need to take care of frequency > > increase to achieve that. This is different from DC motors where > > the frequency converter (commutator) is part of the rotor and you > > have no control over that (cannot control frequency and voltage > > separately as you can for AC motors. > > > > High voltage and low frequency makes the motor "stiff", spinning > > with some RPM regardless of the load (almost like stepper motor), > > while lower voltage will make it "softer". You cannot do that with > > DC motor - higher load will inevitably lower its RPM. > > (closed loop controls aside here). > > > > __________________________________________________ > Do You Yahoo!? > Yahoo! Finance - Get real-time stock quotes > http://finance.yahoo.com
