22 Dec
2015
22 Dec
'15
9:28 a.m.
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 <elson at 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