[ARC5] [Milsurplus] 800 HZ Power: Theoretical Question

Sun Nov 19 17:14:24 EST 2017

On 11/19/2017 3:23 PM, James Whartenby wrote:
> Taigh, Mike and the group
> I would think that any magnetostriction effects would be built into 
> the design of the 800-1 or any transformers so there is nothing a tech 
> could do to change it.

Agreed.

> So it is not surprising to me that there is no mention in your AEMN 
> document that there is actually a design problem.

Not quite so fast.  That is sorta like looking under a streetlight for 
your dropped car keys because you can see better there. :-) In the Navy 
supply system on display in the AEMN (and ARMN, for that matter), 
fundamental design problems were addressed as quickly as any other 
problem.  The fast identification of a production batch of poorly made 
bearings was quickly caught and solved.  The use of a substandard 
bearing grease was quickly identified through the same process of 
constant statistical improvement.  The significant replacement rate of 
carbon pile regulators led to the discovery that aircraft vibration was 
doing them in - producing a crash effort to install them all on shock 
mountings of various types...some jury rigged with garden hose.  Just 
because they didn't have computers doesn't imply that the logistics 
branches of the Armed Services were not intelligent in pursuing their 
mission of getting the highest quality materiel to the troops.

> What was the expected life span of an airplane during WW2; two weeks 
> or 14 missions?

If we try to look at it in a lump sum way, we would then lose the 
nuances associated with the use of 800Hz versus traditional DC avionics, 
and in particular, the US Navy focus of the problem set. For the most 
part, the Navy 800Hz equipment appears to have been put into larger 
aircraft.  Single seat fighters typically received DC operated 
equipment.  Only the larger aircraft, like patrol aircraft and 
multi-engine bombers received the more complex avionics that required 
800Hz equipment, like long range search radar.  That segment of the 
aircraft population didn't have nearly the combat loss rate as the 
carrier aircraft that had such high mortality rates, particularly 
earlier in the war.

> The only way I can think of to see if any of the noise is from 
> magnetostriction is to monitor the current waveform to the 800-1 and 
> compare it to audio from a decent microphone placed in the vicinity of 
> the 800-1.

So, lets assume as a thought experiment that the two waveforms have some 
tenuous relationship.  (I have some uncertainty that any correlation 
might actually mean anything beyond interesting resonances of individual 
parts in a rapidly spinning system, but I'll entertain the thought to 
see where it leads.)  How would we then separate out potentially harmful 
vibrations from ones that don't do anything at all to the structure, and 
how would we know they were harmful and why?

> A moderate resistive load on the alternator should drop any power 
> factor effects out of the test.

That assumption back in the 1940s (that power factor effects in the 
alternators were due to reactive loads), was one which was shared by 
many line maintenance folks.  It was roundly rejected by the engineers 
in the AEMN articles, where they pointed out that, "The fault, dear 
Brutus, is not in our stars, But in ourselves, that we are underlings." 
   Turns out that most of the 800Hz loads were far more resistive than 
was assumed by the "underlings" on the flight line, and were not really 
causing the problems.  The problem was in the alternators, and the 
additional compensating capacitors was a solution to that - not 
correcting wonky loads.  As soon as the underlings understood that 
simple fact, there was a big push in installing and checking the 
required external caps on loads of more than 500VA.  Working smarter, 
not harder...

> If there is any obvious relationships between the two waveforms then 
> the question should be resolved.

I guess I forgot the question.  Either that or the correlation of the 
two waveforms actually implying anything involving the demise of 800Hz 
has escaped me.  I hasten to say that it wouldn't be the first time 
something has escaped me.  But if you look at the grand scheme of 
things, it seems to me that it was largely the significant investment of 
time and money in continually having to "tune" 800Hz systems with a 
gazillion capacitors, as well as the failure to appreciate the economics 
of single frequency hardware acquisition programs for both Services, 
that eventually doomed the Navy's 800Hz "movement".  It's all about the 
money, honey...

> This is not an easy test to perform so I doubt that this question will 
> be answered anytime soon.

True that.

> Over-thinking problems since 1981!
> Jim
>
> P.S. I wonder if magnetostriction is the cause of florescent ballast 
> noise?

Auuugh!  There he goes again!  (Heh, heh...just teasin' Jim.  You do 
have a fertile mind.)

73,
  - Mike  KC4TOS

> ------------------------------------------------------------------------
> *From:* Taigh Ramey <taigh at twinbeech.com>
> *To:* Michael Hanz <aaf-radio-1 at aafradio.org>
> *Cc:* ARC-5 <arc5 at mailman.qth.net>; milsurplus at mailman.qth.net
> *Sent:* Sunday, November 19, 2017 12:39 PM
> *Subject:* Re: [Milsurplus] [ARC5] 800 HZ Power: Theoretical Question
>
> Great information Mike. It will certainly help us with the PV-2’s 
> radar project.
> Thanks,
> Taigh
>
> Sent from my iPad
>
> On Nov 19, 2017, at 5:35 AM, Michael Hanz <aaf-radio-1 at aafradio.org 
> <mailto:aaf-radio-1 at aafradio.org>> wrote:
> Well, according to the Airborne Electrical Maintenance Notes dated 
> September 1945, there did not appear to be any problems caused by 
> magnetostriction effects. The 1" thick document _does_ describe a 
> litany of maintenance problems stemming from issues like improper 
> power factor correction for alternator loads causing heating in the 
> alternator, poor cooling, improper voltage regulator adjustment, 
> vibration affecting operation and life of the carbon pile regulators, 
> use of the wrong grease in bearings, faulty bearing lots, tight 
> brushes, etc.
>
> Not a word about magnetostrictive vibration effects or mitigation for 
> same, on either alternator iron nor transformer iron.  Plenty of 
> photos of the results of problems experienced in Navy fleet 
> operations.  It's a pretty interesting book that I need to scan and 
> put on my website.  There are pieces of it posted at 
> http://aafradio.org/docs/800-1.htm and 
> http://aafradio.org/docs/Voltreg.htm to provide a flavor.
>
> 73,
> Mike  KC4TOS
>
> On 11/18/2017 10:30 PM, Scott Johnson wrote:
>> The big problem is still there:  The unit you are powering has presumably
>> has 800 Hz transformers, and they will sing due to the magnetostriction
>> effect in  the cores.
>> I dare say that is why the 800 Hz "experiment" failed, and 400 Hz became the
>> de facto standard for lightweight AC power applications.
>> BTW, the magnetosrictive vibration eventually displaces the lacquer between
>> the laminations, causing a marked decrease in performance of the
>> transformer.  This was also a problem in the inverters, and lead to fairly
>> short service life.
>>
>> Scott V. Johnson W7SVJ
>> 5111 E. Sharon Dr.
>> Scottsdale, AZ 85254-3636
>> H (602) 953-5779
>> C (480) 550-2358
>> scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net>
>> scott.johnson at ieee.org <mailto:scott.johnson at ieee.org>
>>
>> -----Original Message-----
>> From:arc5-bounces at mailman.qth.net <mailto:arc5-bounces at mailman.qth.net>  [mailto:arc5-bounces at mailman.qth.net] On
>> Behalf Of David Stinson
>> Sent: Friday, November 17, 2017 11:01 AM
>> To: ARC-5<arc5 at mailman.qth.net> <mailto:arc5 at mailman.qth.net>;milsurplus at mailman.qth.net <mailto:milsurplus at mailman.qth.net>
>> Subject: [ARC5] 800 HZ Power: Theoretical Question
>>
>>
>> Theoretical Question:
>> Goal: Simple, *quiet* answer to the 800Hz question.
>>
>> You begin with an unknown inductance with a link-coupled output. (Like
>> transformers).
>>
>> Drive the inductance with a powerful Class-C amplifier, sourcing pulses at
>> freq F.
>>
>> Make the unknown inductance the PA's "tank,"
>> introducing tank capacitance to bring the "tank" into resonance at F,
>> causing the tank to "ring" and provide a sine-wave output.
>>
>> Rectify the sine-wave output as a DC power source.
>>
>>
>> So....
>> Rectify line AC.  Heavy-Current MOSFET pulses the GP or TBW power
>> transformers at 800 Hz.
>> "Tank" capacitor across the transmitter primaries resonates and allows the
>> transformers to "ring."  Ringing transformers output the voltage and away we
>> go.
>>
>> Will it work?
>>
>> 73 OM DE Dave AB5S

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