Re: ballasting

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Peter Komen by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pkomen-at-zianet-dot-com>

I don't think I can do the same type of measurements, but maybe I can
theorize a little.
Comments interspersed.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, October 15, 2002 7:55 AM
Subject: ballasting


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<herwig.roscher-at-gmx.de>
>
>
> Fellow coilers,
>
> Some time ago I posted to the list:
> ---------
> If a PIG's LV winding was ballasted with an arc welder and the PIG
> fed the primary circuit of a TC system: Does the current consumption
> change *much*, if the initially open welding leads are shorted?
I would expect it to.
>
> IMO the leakage inductance of a welder is much larger than its
> magnetizing inductance. Therefore the reflected secondary short,
> which in fact shorts the primary magnetizing inductance, should not
> have a dramatic influence on the total primary inductance of the
> welder and the current from the wall socket. As the relationship
> between both primary inductances of MOTs is smaller, shorting or
> opening their secondary winding should have a larger influence on the
> current. Right?

I don't know.  If someone does, you would probably have gotten an answer
already.

>
> Unfortunately I don't operate a TC system fed from a PIG or a MOT and
> I can not perform measurements therefore. But of course I'd like to
> understand the theory.
> ----------
> Today I made some measurements:
> I connected a 500 W halogen light via wattmeter to the wallsocket and
> read "480 W".

I don't know the wall socket voltage or AC frequency in Germany.  May not be
applicable to this discussion.

> Then I wired a MOT with open secondary winding in series with the
> load and measured "100 W".

Wired wall socket to MOT to halogen light to wattmeter back to wall socket?
I would expect  some non-linear function to calculate the inductance
relative to the halogen light resistance.  This would be complicated by the
changing resistance of the halogen light.

Fairly high inductance to get low current.  If this was run without the
light, you should be able to calculate the magnetizing inductance.

> I shorted the secondary winding and the reading was "420 W".

Much lower inductance; lower than welder with open secondary.  w/o light,
calculate leakage inductance (maybe the total of leakage and magnetizing
currents).

>
> After that I substituted the MOT with a small arc welder and repeated
> the measurements:
> Open welding leads "240 W" and shorted welding leads "480 W"

Magnetizing current is higher for the welder, but the leakage inductance is
lower.  If the light is still in series here, the welder is contributing
next to nothing in impedance to the load which appears to be limited by the
light resistance.

To determine which has the higher ratio of magnetizing to leakage inductance
(or preferably just express these in currents), figure both and calculate
the ratio.  It appears to me, that the welder has a greater range because of
the very low leakage inductance

>
> These results seem to confirm my a.m. theory - right?
>
> BTW: Instead of inductive ballasts one could use capacitive ones.
> Besides of changing the phase relationship, which could make the
> correct alignment of a RSG difficult, are there any other drawbacks?
> Why are inductive ballasts used mostly?
>
> Any comments and critics are very welcome.
>
> Cheers,
>
> Herwig
> ---------------------------------------
> Greed is the root of all evil!
> ---------------------------------------
>

Can you hook to wattmeter in series with just the MOT or Welder and run
these tests?

I hope this helps.  Be careful because I could be wrong.

Regards,

Pete Komen