[ARC5] 800 HZ Power: Theoretical Question

[Scott Johnson]

I think it may not have been a first order problem during WWII, but I am sure it hastened the demise of  800 Hz power systems.  400 Hz is just about as high in frequency as is practical for general power distribution on a vessel.  

 

To the problem, though, I have successfully used a TECO spindle VFD to run a TBW.  The VFD is silent but the transformers still sound like fingernails on a chalkboard.

 

Scott V. Johnson W7SVJ

5111 E. Sharon Dr.

Scottsdale, AZ 85254-3636

H (602) 953-5779

C (480) 550-2358

 <mailto:scottjohnson1 at cox.net> scottjohnson1 at cox.net

 <mailto:scott.johnson at ieee.org> scott.johnson at ieee.org

 

From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Michael Hanz
Sent: Sunday, November 19, 2017 6:35 AM
To: 'ARC-5' <arc5 at mailman.qth.net>; milsurplus at mailman.qth.net
Subject: Re: [ARC5] 800 HZ Power: Theoretical Question

 

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  <mailto:arc5 at mailman.qth.net> <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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