[ARC5] [Vintage-Military-RADAR] 800 Hz Static Inverters

[Mike Hanz]

On 5/23/2014 3:40 PM, 'J. Forster' jfor at quikus.com 
[Vintage-Military-RADAR] wrote:
> I want to power up parts of an ASB-5 RADAR. The thing takes 800 Hz, either
> 80 or 115 VAC, Single Phase, roughly 500 - 1000 Watts.
>
> I've read articles on the web about modifying commercial (Asian) 60 Hz
> units for 400 Hz. This seems a possible alternative, but the articles
> referred to obsolete and unavailable converters.

This is certainly a possibility, but will require some development 
work.  It depends on how much time you have to devote to it.

> Does anybody know of suitable 'true sinewave' 60 or 800 Hz inverters that
> are currently available (used OK) that have documentation available? My
> guess is that not only the internal clock, but also any output filters,
> would need modifying.

Sure.  Behlman makes the best, and occasionally you can pick one up on 
auction for a reasonable price if you are patient.  Don't be put off by 
the ebay asking prices - I got one 100C for $35 and another for $16.  
Shipping was more than that, though...these things are heavy!  Both 
worked fine on receipt.  You'll need a varible oscillator plug-in, but 
it's simple and the mainframe is good from 45-2,000Hz.  It has a 
harmonic distortion of about 0.5%.  For the wattage you are looking for, 
a Behlman 100C would be about right. One with an analog output meter 
will usually be a lot more reasonable.  You'll need 7" of rack space for 
it, though.  PDF manuals are available from Behlman, or from a fan base 
that is quite extensive.

> Alternately, does anyone know if there are 1 Phase VFDs that are line
> powered that can be used as an inverter?

I know of no single phase output VFDs, and they are all pretty much 
matched to a 3 phase motor's starting characteristics, not a transformer 
with a resistive load.  The anecdotal evidence suggests this is not a 
good solution, though cranking up the sampling frequency and diddling 
with the programming might be possible.

Good luck,
  - Mike