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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: sci.electronics
Subject: 400 Hz transformers
Message-ID: <726@neoucom.UUCP>
Date: Fri, 9-Oct-87 23:45:37 EDT
Article-I.D.: neoucom.726
Posted: Fri Oct  9 23:45:37 1987
Date-Received: Mon, 12-Oct-87 06:10:08 EDT
Organization: Northeastern Ohio Universities College of Medicine
Lines: 29
Keywords: Mostly to save weight


I have done some work on power distruibution systems-- though not
too much.  Most 400 Hz stuff is designed for use in mobile
applications where saving weight and size is very important.  I'll
side with Larry (as usual) on this issue.

Working with 400 Hz power is much less fun becuase there is much
more loss due to direct radiation from the transmission line.  Yes,
indeed, at high power levels skin effect at 400 Hz is a problem.

400|800|1200 whine is much more annoying than 60|120|180 Hz hum
from poorly regulated power supplies.  Of course, one of the big
advantages of using 400 Hz is that filter capacitors can be smaller
to achieve the same level of regualtion.  Unfortunately, rectifier
diodes are less efficient at 400 Hz.

The best win is that 400 Hz power transformers are very small.
Torroidal construction is much more common for 400 Hz applications
thatn it is for 60 Hz.  Many 400 Hz transformers are 95-98%
efficient.  By the way, most 60 Hz transformers are over 90%.  We
have several 50 KVA transformers here that are air cooled and are
only about 18 inches (~50 cm) on a side cubes.

If memory serves me right, Cray computers are equipped with 6 power
supplies disguised as benches mounted around the lower outside part
of the CPU.  Each power unit is about 5 KVA, I think.

Bill
(wtm@neoucom.UUCP)