12 Oct
2024
12 Oct
'24
8:58 p.m.
On Oct 12, 2024, at 4:54 PM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 10/12/24 14:30, Paul Koning via cctalk wrote:
Yes, I've heard that. But why? Power supplies of that era start with a transformer,
which acts as a low pass filter, and after the rectifier there's another filter. Sure
you can turn the PWM waveform into sines, but I can't see that it matters much.
paul
Years ago I commented (on this list, probably)
that a "VFC" would likely make a good 400 Hz supply. VFC is "Variable
frequency controller", a device that takes mains input and turns it into three phase
output of a frequency of your choice. The upper frequency is typically fairly low; I
don't think mine reaches 400 Hz but then again it cost me less than $100 for a unit
that can drive a 3 hp motor. That one takes either single or three phase (220 volt)
input; larger ones are normally specified as 3 phase only though chances are they would in
fact work if you fed them single phase power.
VFDs use IGBTs to create variable width square waves of about 400 V. These can be turned
into appropriate waveforms with a filter, but you sure don't want to feed these
directly into any kind of computer power supply directly.
Jon