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Re: Microwave trannies in series
From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: Monday, November 10, 1997 6:35 AM
To: tesla-at-pupman-dot-com
Subject: Re: Microwave trannies in series
In a message dated 97-11-10 10:25:06 EST, you write:
<< Hi,
> Was wondering whether 5 or more secondary series-linked Microwave trannies
>>would
> make a good power supply for a TC as these are very easy to get hold
> of and for free.
> I have a number of these units which put out a wopping 800ma at 2200V
> and would love to be able to use them if i can as Neons or polepigs are
> hard if not impossible to obtain in New Zealand.
> Thanks in advance.
>>
Matt,
I'm assuming these have one end of the secondary grounded to
the core as in the ones I've seen. The problem with series-ing
these is that the more you series, the higher the voltage becomes
between the primary and the core. The primary to core insulation
is poor and can allow breakdown.
However, I have used 4 of these trannies in series despite the
above weakness and have obtained 65" flaming arcs at 6 kVA,
using the internal current limiting inherent in these trannies. I'm
assuming your's are current limited too. In my set-up, I grounded
two of the cores, then connected the cores of the two other
trannies to the hot sides of the first two. This puts them in
series with a midpoint ground. During operation in a darkened
room, I could see corona in the two outboard trannies which see
an unhappy voltage stress between primary and ground. The
primaries were run in series parallel to allow the use of 240V,
(the trannies are 120 volt types). It is probably a good idea to
place at least the outboard trannies in oil to insure reliability.
Also there's some danger because the cores of the outboard
trannies will be electrically hot, (about 2kV). I posted this
info on the list some time ago, and some responses were
negative, but the method does work. It is doubtful that any
of the naysayers actually tried it. Have fun.
John Freau