[BC] Extra 9 phase

[Davis, Jack L. KTXL]

Message: 25
Date: Thu, 12 May 2005 22:32:01 -0500
From: "Dave Dunsmoor" <mrfixit at min.midco.net>
Subject: Re: [BC] 12 phase
To: "Broadcast Radio Mailing List" <broadcast at radiolists.net>
Message-ID: <003901c5576c$53b2fa10$0200a8c0 at cd2176218a>
Content-Type: text/plain;	charset="iso-8859-1"


> >>The Bauer of the day with its 12 Phase
> >>Power supply had overated its power and modulation transformers and
would
> >>usually get well over 100%.
>
> >Must have had a "Zig-zag" plate transformer, then
>
> -- the Marconi BD272C 250KW HF broadcast transmitter had 12 phases; each
> phase fed an AR64 ignitron rectifier (mercury pool dippers). Simply done
by
> taps at appropriate points on the HT transformer. Gives very low ripple
and
> doubles the ripple frequency, so the HT smoothing components can be
lighter
> and less bulky.
> - Clive


Ok, I gotta ask. where did the other 9 phases come from?

Dave Dunsmoor



A more correct term would be 12 pulse rectifier.  The input is 3 phase but
the transformer is a delta wye configuration that gives 12 rectifier pulses
per cycle. Here is a link that explains the concept.
http://www2.ing.puc.cl/power/paperspdf/dixon/21.pdf This increases the
ripple frequency and makes the HV filter components much smaller. TV Beam
supplies have used multi pulse rectifiers for years on Klystron and IOT
transmitters. 

Jack Davis
KTXL-TV