3-phase power

[Eric Smith]

On Tue, Jan 4, 2022 at 8:36 PM Grant Taylor via cctalk <
cctalk at classiccmp.org> wrote:

> My limited understanding is that VFDs simulate / emulate various
> frequencies by turning the output on and off (at full input voltage)
> such that the (sliding) /average/ of the output looks like it's a at a
> lower voltage.


That's how all buck switching power supplies work. It's just a question of
how much low-pass filtering you do on the output. A switching power supply
to power sensitive electronics that requires good voltage regulation and
low ripple contains electrolytic capacitors on the output. A VFD may or may
not. The specs on the VFD should tell you about the output characteristics.

If you're just going to power a three-phase synchronous motor, then no
filtering is needed. The inductance of the motor windings and the
mechanical characteristics of the motor will filter it just fine.