[Boatanchors] Are 400 Hz variac's good for anything but a real 'boat anchor'

Bruce Long coolbrucelong at yahoo.com
Mon Jul 18 11:08:51 EDT 2011

But the 7:1 guys are correct  Nowhere in the thread has anyone suggested applying 120vrms/60Hz to a 400 Hz variac.  The 7:1 factor is the required de-rating needed to operated a 400 Hz variac on 60 Hz in order to avoid core saturation.

--- On Mon, 7/18/11, J. Forster <jfor at quik.com> wrote:

From: J. Forster <jfor at quik.com>
Subject: Re: [Boatanchors] Are 400 Hz variac's good for anything but a real      'boat anchor'
To: "Bruce Long" <coolbrucelong at yahoo.com>
Cc: "Bill L''Fuqua" <wlfuqu00 at uky.edu>, doc at kd4e.com, "John Hurst" <hurstjsj at verizon.net>, "'Boatanchors List'" <boatanchors at puck.nether.net>
Date: Monday, July 18, 2011, 10:58 AM

The statement is true. In a properly designed 400 Hz transformer operating
at the rated voltage, the iron is not being saturated during any part of
the cycle.

If you go to 60 Hz with the same applied voltage, the iron will be
hopelessly saturated, and it's incremental permeability will drop to near
that of free space. It's like the iron just vanished.

The magnetizing current will go up far, far more tha 7x.




> "The magnetizing current @60 Hz will *much* higher than 7 times the
> current
> at 400Hz."
> Please explain- justify.
> I agree with the 7:1 guys on this. 
> Basically the issue arises in the electronic speed/torque control of
> induction motors.    Bruce   KJ3Z

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