[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: PFC Question
- To: tesla@xxxxxxxxxx
- Subject: Re: PFC Question
- From: "Tesla list" <tesla@xxxxxxxxxx>
- Date: Sun, 06 Nov 2005 11:15:13 -0700
- Delivered-to: email@example.com
- Delivered-to: firstname.lastname@example.org
- Old-return-path: <email@example.com>
- Resent-date: Sun, 6 Nov 2005 11:16:18 -0700 (MST)
- Resent-from: tesla@xxxxxxxxxx
- Resent-message-id: <B2DNgC.A.cbH.hhkbDB@poodle>
- Resent-sender: tesla-request@xxxxxxxxxx
Original poster: Steve Conner <steve@xxxxxxxxxxxx>
I'm having a hard time understanding how there can't be any series
inductance when, say, the setting as at the midway point.
It all depends on a lot of things.
When the variac is wired as a variac, it does introduce some
inductance. I noticed this when testing rectifiers that draw sharp
spikes of current from the supply and are very sensitive to
inductance. It seems to go from about a couple of millihenries when
the dial is set to 50%, down to practically zero when it's set to
100%, then back up again as you go above 100% on an overwound variac.
This is of course leakage inductance: the result of whatever flux
lines can squeeze their way around the core. The iron core doesn't
play any part because it links all the windings.
When the variac is wired as a ballast, the core contributes to the
inductance which can then be several henries, and probably varies as
the square of the dial setting. But it may only take an amp or two
before saturating, unless you modify it by adding an airgap.