[Milsurplus] 800 CPS inverters

[Michael Hanz]

The 800Hz frequency _was_ probably arbitrary, but the Navy did find that 
the weight savings in transformer and generator iron by doubling the 
line frequency was a bit more than "negligible", as one might surmise.  
The British even used 1,600 Hz in their GEE and countermeasures 
equipment, prompting the U.S. to follow suit on their countermeasures 
gear so that the Brits could use it in their aircraft.  Several of my 
WWII jammers and surveillance receivers list 115/80 volt inputs at up to 
1,600Hz as an alternative power source.

The problem with initial Navy standardization on 800Hz became clear only 
after more than one load began to be hung on generators and inverters.  
The ugly head of power factor correction turned out to be a greater 
headache than the Navy engineers had anticipated, and hanging multiple 
loads on a single generator, especially loads that changed from one 
moment to the next, created voltage regulation problems and even damage 
to generating equipment.  That's the reason for the multiple switched 
compensation capacitors on the GO-9 and GP-7, plus other available 
"fixed" compensating capacitors like the Kellogg Type A condenser box at 
the bottom of the page at http://aafradio.org/flightdeck/go9.htm

That effect was much reduced at 400Hz, and the constant readjustment of 
loads - and damage to alternators for not properly doing so - finally 
drove the Navy to tacitly admit what it likely dreaded admitting...that 
the Army (and commercial aviation in the bargain) was right.  Oh well, 
it seemed like a good idea at the time.

           73,
  - Mike  KC4TOS

On 11/17/2017 8:24 AM, elden meyer via Milsurplus wrote:
> There is a brief but interesting section on inverters
> in volume 17 of the MIT Radiation Lab Series.
>
> As mentioned here recently the author states that
> the Navy choice of 800 CPS was more or less arbitrary
> and made prior to the standardization on 400 CPS.
>
> The series is on-line at:
>
> https://www.jlab.org/ir/MITSeries.html

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