Some VFDs are not just plain PWM pulses, but a stepped sort of thing that sort-of approximates a sinewave.
As I said, all this depends on what VFD you are using, and what you might have to act as a filter, and what the load is - a case-by-case thing. -- Will On Tue, Dec 22, 2015 at 12:12 PM, Jon Elson <el...@pico-systems.com> wrote: > On 12/22/2015 10:25 AM, William Donzelli wrote: >> >> Another thought - with scrap transformer prices in a crapper right >> now. you might also be able to pick up a really beefy isolation >> transformer for spare change, in order to clean up a VFD. Generally, >> normal industrial grade 50 Hz transformers will not care too much if >> you use them at 60 Hz. >> > An isolation transformer will NOT "clean up" a VFD's output. The output of > a VFD is NOT some dirty sine wave, it is a train of 400 V PWM pulses with > perhaps a 15 KHz carrier frequency. It could be filtered, but would take a > filter built out of a bunch of HUGE inductors and capacitors. It might > actually be a decent solution for keeping museum-quality gear running in an > unaltered state, but it isn't something you could whip up in a couple hours > in your garage. > > Jon
