[MRCG] 800Hz AC Power for Navy Radios

[Mark J. Blair]

On May 26, 2013, at 14:51 , Scott Johnson <scottjohnson1 at cox.net> wrote:
> Most of the noise comes from magnetostriction in the stator.  I have tried
> to quiet those things dowN, but to no avail.

Dennis W7QHO (IIRC) said that was the main noise source in the BIG motor-generator set that Paul N6FEG bought at the MRCG meet, seen here in the back of Tom W6TOM's truck:

  http://www.nf6x.net/wp/wp-content/uploads/2013/05/IMG_2573.jpg

I don't think there's much that can be done about that other than putting the whole thing in a suitable enclosure. Maybe vacuum-impregnation of the coils and cores with epoxy might help if they're not already potted? That doesn't sound like something that would be easy for a hobbyist to do, though.

I got the impression that blower noise is a substantial contributor to the noise from the model 800-1 inverters. Looking at the picture, the blower assembly looks like a mechanical siren to me:

  http://aafradio.org/flightdeck/800-1_Inverter.JPG

I would hazard a guess that blower noise could be reduced by changing the geometry of the air outlets in the end bell. But if it also makes a lot of magnetostrictive noise, then quieting down the blower might not help much. I haven't experienced any operating 800 Hz rotary machines in person yet.


> Even the 700 VA solid state inverter I modded made a lot of noise
> (laminations in the transformer), so will the transformers in the rig. (The
> TBW was very noisy)

I wonder how much noise my solid-state inverter will make under load once I convert it. It doesn't have any laminated core devices in its output circuits, but the toroidal filter choke windings might still sing. It's certainly capable of making audible noise, as I discovered when I touched some noise-sensitive nodes with a scope probe.


-- 
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/