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

[James Whartenby]

Taigh, Mike and the groupI 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.  So it is not surprising to me that there is no mention in your AEMN document that there is actually a design problem.  What was the expected life span of an airplane during WW2; two weeks or 14 missions?
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.  A moderate resistive load on the alternator should drop any power factor effects out of the test.  If there is any obvious relationships between the two waveforms then the question should be resolved.
This is not an easy test to perform so I doubt that this question will be answered anytime soon.  
Over-thinking problems since 1981!Jim
P.S. I wonder if magnetostriction is the cause of florescent ballast noise?

      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> 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
scott.johnson at ieee.org

-----Original Message-----
From: 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>; 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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