400 Hz

W2HX w2hx at w2hx.com
Fri May 7 16:59:08 CDT 2021

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-bounces at classiccmp.org> On Behalf Of Andrew Back via cctalk
Sent: Wednesday, May 5, 2021 11:26 AM
To: cctalk at 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.



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