daleyd
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- Wrexham, North Wales
It's "unlikely" (very) you'll run a squirrel cage motor "outside its design parameters", unless you do something daft with the vfd settings. I've not seen it, even on very old motors though I'm not doubting it "can" happen.AC does funny things once you start changing the relationship between current and voltage, like running a motor outside it's design parameters
There are motors that will react badly to a change in frequency, +/- 10% probably won't get noticed, but the larger the deviation the greater the possibility.
Depending on application, you won't always save electricity by slowing down (or speeding up) a motor either...
Agreed that the electricity savings dont always occur, and indeed for something like a lathe in a home workshop the savings will be almost negligable (Certainly you'd never get a payback from the inverter cost unless you were running mega hours), but the fact is you run the motor slower then the voltage is lower and since the current is limited then the consumed power will be lower (Inverters will generally have a linear v/f relationship).