On 5/8/21 12:00 PM, cctalk-requ...@classiccmp.org wrote:
Message: 8 Date: Fri, 7 May 2021 21:59:08 +0000 From: W2HX
<w...@w2hx.com> To: Andrew Back <and...@carrierdetect.com>, "General
Discussion: On-Topic and Off-Topic Posts" <cctalk@classiccmp.org>
Subject: RE: 400 Hz Message-ID:
<de37431b96cf4c82ba5ddb2b9daf1...@exbe015sv3.na02.msexchangeoutlook.com>
Content-Type: text/plain; charset="utf-8" I will add that aircraft are
one of the main users of 400 Hz. This is because weight is always an
critical design consideration. So with smaller transformers, smaller
capacitors, etc, you can save a LOT of weight on electronic devices in
an aircraft. 73 Eugene W2HX -----Original Message----- From: cctalk
<cctalk-boun...@classiccmp.org> On Behalf Of Andrew Back via cctalk
Sent: Wednesday, May 5, 2021 11:26 AM To: cctalk@classiccmp.org
Subject: Re: 400 Hz On 05/05/2021 16:07, Grant Taylor via cctalk wrote:
Were the higher frequencies used because it directly effected the
amount of time / duration in (fractions of) seconds between peaks of
rectified (but not yet smoothed) power?
Haven't read the rest of the thread and so at the risk of being profoundly
wrong... Benefit of 400Hz mains is that transformers can be much smaller. Think
of switching power supplies that rectify to DC and then switch up into kHz,
which are then able to use far smaller transformer cores than an old linear
PSU. At least this is a key motivation with 115V/400Hz 3-phase aviation power
AFAIK.
By coincidence we've just built a big 28VDC power supply, so that we can run a
vintage 400Hz aircraft rotary inverter, which will then be used to power up old
mil surplus kit that wants this. A classic adventure in yak shaving. Anyway,
here's the 28VDC bit.
https://www.rs-online.com/designspark/constructing-a-high-current-28v-dc-power-supply
That's a very neat repackaging of the Lambda power supplies! Do they
have the surge capability to start that rotary inverter (which may
require a LOT more than 44 amps until the armature gets moving)... I
hope you tested them first ;)
I bought a 1 KVA 115V 400 Hz supply, a PP-7482/G from Fair Radio back
when they still had them ("Reparable") a few years ago. The H-bridge
TO-3 transistors were all blown, some with holes melted through their
lids. I replaced them with BUX48A parts and it works again. It really
sings that A-flat though ;)
But I don't have anything to run with it! When I was young, 400 Hz
surplus gear was a dime a dozen because no one had 400 Hz power. Now I
do and all that gear has disappeared...
-Charles
WB3JOK/0 since '76 :)
