On 2011-07-06, axolotl wrote:
On 7/6/2011 10:32 AM, Spehro Pefhany wrote:

Here's the MIL spec for aircraft power from '59:
http://www.everyspec.com/MIL-STD/MIL...D_704.1080.pdf


Here's the current spec, 704F.

http://docimages.assistdocs.com/watermarker/transient/B0731B2B03B641D89CBFA7FB8886890F.pdf

Hmm ... I've just thought of something. I have a couple of
ancient aircraft instruments (a gyrocompass and an artificial horizon)
which each use a gyro powered by 115V 400 Hz three phase. Fine, those
should work well with a VFD powering them.

But also included are devices to adjust for proper axis on the
gyros -- during spin up and more slowly once in the air. These consist
of torque motors on each axis in the gymbals, which are fed current to
bring that axis into alignment (vertical on the artificial horizon, and
horizontal on the gyrocompass). Each of these are fed through a clip-in
device which has what I suspect to be saline solution in the bottom of
a shallow dome (curved down in the center), and feed that to four
contacts at 90 degree intervals. I'm not sure how well that will
balance with the synthesized sine waves output from the VFD.

And -- FWIW -- I can use only one of these instruments at a
time, because the stator (these are inverted rotor motors) in one is
burned out, and it takes me about a half an hour or so to swap it from
one to the other. :-)

Hmm ... perhaps time to try rewinding the stator? I didn't even
think of it back in the early 1960s when I first got these. :-)

Enjoy,
DoN.

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