[Milsurplus] 115 VAC 400 hz power

[Tom Dawson]

Somewhere around here I've got an aircraft electrical systems manual that 
describes the constant speed drives used to drive the 400 cycle AC 
generators, however I cannot swear it is not post-war.  Will post   the date 
when the book turns up.

73

Tom
WB3AKD

----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Mike Morrow" <kk5f at arrl.net>
Cc: <milsurplus at mailman.qth.net>
Sent: Thursday, January 13, 2011 7:39 PM
Subject: Re: [Milsurplus] 115 VAC 400 hz power


> Mike,
>
> As to engine driven generators, I see no technical reason why they would
> be problematic. As the RPM varied, the frequency would vary, but other
> than possible fan or motor speed issues, the electronics should work fine.
> Most all motors I've seen in radios operate on DC anyway.
>
> So, if the alternator produces >400 Hz at idle, it'd not matter if it
> produced 1200 Hz or whatever at full power.
>
> Output voltage was regulated, of course.
>
> This is theoretical knowlege, however.
>
> Best,
>
> -John
>
> =============
>
>
>
>>>115 VAC at 400 hz was also used as input for the power transformers in
>>>some WW2 aircraft nav gear such as SCR 269, ARN 7, APN 4, APN 9 etc.
>>
>> As far as I can determine, all that aircraft 400 Hz power came from
>> inverters.  The -1 flight manual (24APR51) for the B-29, 29A, and 29B
>> (likely the WWII aircraft with the most need of 400 Hz power) indicates
>> that all those loads requiring such power (including the "Raven"
>> countermeasures gear) got it from multiple relatively small 28 vdc input
>> single-phase rotary inverters.
>>
>> Engine-driven 400 Hz generation would be complex, given the requirement
>> for a specific constant speed input to the generating system.  (Today's
>> modern systems haven't that problem.  Honda's EU2000, for example, uses a
>> microprocessor-controlled variable-speed engine to drive an alternator,
>> whose output is rectified and fed to a microprocessor-controlled static
>> inverter to produce some of the cleanest pure sinusoidal 60 Hz at 
>> constant
>> voltage that a portable gasoline-powered 2 KW generator has ever
>> produced.)
>>
>>>I've been tempted to amplify the output and fire it up on the 160M band
>>> to
>>>give the old timers a jolt, but sanity prevailed. The sound of LORAN A
>>>signals is something the old timers on Top Band will never forget.
>>
>> One need not be an old-timer to remember 160m LORAN A signals.  The USA
>> didn't close its LORAN A service until 31DEC80, a mere blink-of-an-eye
>> ago.
>>
>> Mike / KK5F
>>
>> (I bought my R-65/APN-9 LORAN A at John Meshna's store in Lynn, MA, in
>> 1976.
>> An AN/APN-9 was installed on the Royal Netherlands Navy Destroyer Hr.Ms.
>> Amsterdam, on which I was assigned in 1973, but in the North Sea we used
>> the UK Decca Navigator instead as the preferred hyperbolic
>> radio-navigation
>> system.)
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>
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