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Re: More Tuning/Debugging Next
On Sat, 7 Sep 1996 16:25:38 -0600, Tesla List
<tesla-at-poodle.pupman-dot-com>, you wrote:
>From: Bert Hickman <bert.hickman-at-aquila-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: More Tuning/Debugging Next
>
[major snip]
>Jim,
>
>I was just reading a section on distribution transformers in a book
>called "Electrical Power Technology" by Theodore Wilde (John Wiley &
>Sons, 1981). The discussion on the no-load saturation curve for these
>transformers says that transformers are usually designed to operate at a
>peak flux density of about 1.5 Tesla, which roughly corresponds to the
>knee of the saturation curve. This implies that, even with no load, the
>primary current will rise dramatically once we begin to apply any
>significant overvoltage to the winding. "We can exceed the nominal
>voltage by perhaps 20%, but if we apply twice the nominal voltage, the
>exciting current may exceed the nominal full load current, even when the
>transformer is not loaded". This sounds exactly like the situation a
>number of coilers are using: overdriving the 120 volt winding(s) to
>push a 6-7.2 KV pig to a higher output (12-15 KV).
>
>Have any coilers actually measured the pig's primary current draw with
>NO output loading versus input voltage?? If the pig is heavily
>saturating, will this tend to improve or worsen the transients created
>by the inductive ballast when the gap extinguishes??
>
Bert,
Thanks for the info. That book or a book like it is at my
local bookstore. It's on my list of books to buy.
I've measured the no load current of my Westinghouse 10+ LL-65
pig as 1.8A with 220Vac into it's 220V tap. With 220V into the 110 tap
and no ballast I trip the 50A breaker instantly. Unfortunately I don't
have a 220V variac or a large enough 110:220 autotransformer to test
the over voltage characteristics at this time.
All,
Would any one else like to try this measurement? Over volt the
110V tap of your pig and plot the current with the HV open.
jim