ballasting

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

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:
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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?

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?

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.
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Today I made some measurements:
I connected a 500 W halogen light via wattmeter to the wallsocket and 
read "480 W".
Then I wired a MOT with open secondary winding in series with the 
load and measured "100 W".
I shorted the secondary winding and the reading was "420 W".

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"

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
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Greed is the root of all evil!
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