[Milsurplus] 12-24 vdc converters and toroid cores

Mike Feher n4fs at eozinc.com
Mon Oct 12 13:03:06 EDT 2009 

Robert Flory just mentioned to me that the guy in Cyprus has a lot of them.
As it turns out, I bought mine from the guy in Cyprus also, and, not the one
from Israel. The ad claims 12 amps output, so, I guess my tests pretty much
confirm that. I bought mine on August 9 for $86, plus $46 shipping. Nice
little package, other than for the whine. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960




-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Mike Feher
Sent: Monday, October 12, 2009 11:54 AM
To: 'Mike Feher'; 'Al Klase'
Cc: boatanchors at mailman.qth.net; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] 12-24 vdc converters and toroid cores

Well, I finally got around to testing out the converter from Israel that I
purchased, and it appears several on here have them including Gene. I also
received an email from Bill, KD0FKT, who did not get connectors with his,
but, was able to get them from www.spacecraft.com in Nevada. Regardless,
here are some crude test results run on the unit. I used an HP 428B clamp-on
amp meter, which only has an upper limit of 10 amps. Using a fully charged
car battery as the source, with a no load output of 13 volts, I turned on
the inverter, and as Gene mentioned it really sang. This was without the
inverter being physically clamped down. More than likely in a vehicle it may
not be noticed. The no load output was right at 28 volts. As I slowly
decreased the variable load resistance I got the output current up to 10
amps, with an output voltage around 26.5. By this time my input voltage had
dropped to about 12 volts. I was unable to measure the input current since
as I said, the meter was limited to 10 amps max. I did run it for a little
while at over 10 amps to the load, and the breaker shut of on the inverter,
so, about 10 amps or so seems to be the limit. By this point I could smell
the heat from my load, so, decided this was close enough for now. I really
would have liked to measure the input current, but, I bet it was probably
close to 30 amps, which is just a guess. Still not bad for a 250 or so watt
inverter. BTW, during my testing, the inverter never even got warm. 73 -
Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960


  

-----Original Message-----
From: Mike Feher [mailto:n4fs at eozinc.com] 
Sent: Tuesday, October 06, 2009 1:17 PM
To: 'Al Klase'
Cc: 'boatanchors at mailman.qth.net'; 'milsurplus at mailman.qth.net'
Subject: RE: [Milsurplus] 12-24 vdc converters and toroid cores

Al -

Ok - I have not had a reason to try it yet, but, Gene's earlier post implied
it may have some issues. I'll try to hook it up yet today and then put a
decent load on it and will give the report of results on here. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960


-----Original Message-----
From: Al Klase [mailto:al at ar88.net] 
Sent: Tuesday, October 06, 2009 1:11 PM
To: Mike Feher
Cc: boatanchors at mailman.qth.net; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] 12-24 vdc converters and toroid cores

Hey Mike,

Let us know how that thing works.  I've been tempted to get one of 
those.  It looks like a much better solution to the 24-volt radio in a 
12-volt vehicle problem.  All this change the alternator/use two 
batteries stuff is fraught with complications.

I've also contemplated building an inverter, but as the original poster 
pointed out, the magnetics (the transformer core) are a major question 
mark.  If there's a good $100 solution, it's not worth the engineering 
exercise.

Al

Mike Feher wrote:
> I admit that I have not been following thread, so, please take my comments
> accordingly - About a week or so ago I purchased a 12 to 24 volt converter
> from a guy in Israel on eBay. It arrived in good shape, and with
connectors.
> I believe this was intended for the RT-524, and, with shipping it was just
a
> little over $100. Have not tried it yet. He seems to have several. 73 -
Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>   
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Peter Gottlieb
> Sent: Monday, October 05, 2009 7:17 PM
> To: Michael Tauson
> Cc: boatanchors at mailman.qth.net; milsurplus at mailman.qth.net;
> boatanchors at lists.tempe.gov
> Subject: Re: [Milsurplus] 12-24 vdc converters and toroid cores
>
> Simplified:  the current times time during the magnetizing part of the 
> waveform must not saturate the core.  Raising the frequency reduces 
> that, but core losses can increase depending on core material.
>
> You can monitor the primary current to watch for saturation by using 
> either a current probe or a series small value non-inductive resistor.
>
> Peter
>
>
> Michael Tauson wrote:
>   
>> Most civilized civilian vehicles have 12 volt electrical systems these
>> days.  Much of the surplus I'd like to use aboard my all to civilized
>> Jeep requires 24vdc.  Building a small but mighty astable
>> multivibrator to handle the primary and an appropriately wound
>> secondary aren't a problem.  Where I do have a question or seventeen
>> is core material - and size, for that matter.
>>
>> I know some materials are expressly for power transformers but is
>> there any particular reason about any material can't be used for this
>> application?  Frequency shouldn't be an issue but are there materials
>> that might not like being in the presence of the currents that will be
>> presented?  Aside from needing space to feed the wires through, are
>> there any size requirements of note?
>>
>> I've read what I could find on the web.  Maybe the meds are messing me
>> up (They do that, you know.) but I couldn't find anything that
>> addressed these questions.
>>
>> ANy thoughts anyone?
>>
>> BEst regards,
>>
>> Michael, WH7HG
>>   
>>     
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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