Re: PFCs

To: tesla-at-pupman-dot-com
Subject: Re: PFCs
From: "David Dean" <deano-at-corridor-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Fri, 22 Oct 1999 20:13:21 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme




>Original Poster: Grayson B Dietrich <electrofire-at-juno-dot-com>
>
>Hello All,
>
>
>
>I was wondering,
>
>Would a bank of paralleled motor-start caps be suitable as a power factor
>correction cap? I I calculated, if memory serves, something like 80uF or
>90uF for my 12kV 60mA NST. When powering my TC, it blows a 10 amp fuse no
>problem...   ...and I really wish it wouldn't. Since then I could safely
>fuse my variac with the fuse holder built into it.
>
>
>
>Grayson Dietrich
>http://www.electrophile.8m-dot-com
>
Actually it is the motor _run_  capacitors you want.
Run capacitors come in a metal can and are filled with oil.
They have a single capacity rating, and the working voltage is
usually 370 or 440 for 240 Volt service and lower.
Start capacitors come in a plastic can and are "dry".
The capacitance rating will be something like 88-108 (a range)
and the voltage rating will be right about the rated service
voltage. Like 125, or 220.

Sometimes people call run caps start caps because some motors
use only a run capacitor which is hooked between common and
start. An example would be a PSC motor (perminant split capacitor)
like a blower motor or a fan motor in an A/C or furnace.

Make sure you have the right kind of cap (motor run capacitors are fine to
use
for PFC) because the start caps will at least smoke, and I have seen them
explode violently when a motor has a locked rotor or a shorted start
winding.
This puts the cap effectivly across the line as it would be hooked up as a
PFC.
It sounds like a shotgun blast and pieces of foil and paper go all over the
place.

later
deano