If i run a 50 hz three phase motor in very low speed eg: 5-10 hz control by vfd, will it damage the motor?
Answer:
you'll need to watch the current.
at such slow speed, the back-emf will not be sufficient to provide the design resistance.
remember how when you turn a large motor on, the lights on the same circuit dim till the motor gets going.
that's because the rotational speed is too low to generate the needed back-emf.
if the motor were to run continuously at that slow speed, it would burn out.
now, if you also limit the voltage, thus the current (which is the problem) you might get away with it.
but it would seem a poor use of a rather valuable motor to me.
it would seem to make more sense to get a motor that was designed to do what you need.
also, running that slow, you'd get very poor electrical efficiency.
really, see if you can get a motor to match the task.
You would only damage the motor if an excessive amount of current were allowed to flow through it, thus overheating it and burning out the coils or melting the insulation on the wiring. If your vfd limits the current, then things should be fine.
I once used a 150-watt incandescent light bulb in series with a chopped Electrolux vacuum cleaner, in order to slow the motor and cut the noise. (This was to power an old pedal-pump reed organ.) Because the bulb limited both the voltage and the current, the motor worked fine for many years.
the motor winding will be overheated.
there is hardly any counter emf if you run the motor at almost dc current.
running a motor at higher frequency is generally not damaging. running at lower will cause problems real fast. eddy currents in the iron can cause overheating even without the motor connected to a load. same is true of transformer devices.
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: