<<I remember a trick from a now retired transformer designer from SNC
(Oshkosh, WI)>>
Yep, I had forgotten about that. I've used that too... and it does work.
Sincerely,
Dr. William J. Schmidt, II K9HZ
Trustee of the North American QRO - Central Division Club - K9ZC
Email: bill@wjschmidt.com
WebPage: www.wjschmidt.com
"If computers get too powerful, we can organize them into a committee; that
will do them in." -- Bradley's Bromide
----- Original Message -----
From: "John T. M. Lyles" <jtml@lanl.gov>
To: <amps@contesting.com>
Sent: Wednesday, June 15, 2005 10:03 AM
Subject: [Amps] HV transformer test tspa
>I agree with Harold about it being coated. Although I have bought
> plenty of HV transformers (single and three phase) which had only a
> sinple varnish overcoat that are in commercial transmitters
> (numbering in the hundreds of units in field since 1982). I say
> simple, well, probably they had numerous coats, but they were not
> potted solid like would be if they were done in a tank under vacuum.
> Another trick would be to just place the iron into a large polymer or
> steel tank, full of good oil.
>
> I remember a trick from a now retired transformer designer from SNC
> (Oshkosh, WI), which was to measure the copper primary resistance
> cold (use a four wire milliohmeter) then power test it and measure it
> hot. You should be able to calculate the average temperature rise in
> the winding from the delta R of the copper.
>
> The most potted HV transformer I have seen is the plate tranny from a
> Harris RF102 that I got. It looks like a blob of epoxy, with the
> edges of the lams exposed and flying leads coming out of the gunk.
>
> Depending on the insulation, class B, class F, class H, etc, the
> transformer can run very hot without damage. If it is only class B
> for instance, it must be wound with heavier guage wire and use more
> iron to keep the temp rise down. You can read about these ratings in
> any of the big thick Electronics Handbooks, like the one by IEEE.
>
> 73
> John
> K5PRO
>
>
>
>
>
>>Send Amps mailing list submissions to
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>>
>>Today's Topics:
>>
>> 1. SBE SB1-LA Power out meter (Randy K4QO)
>> 2. questions on my tranformer test (kenw2dtc)
>> 3. Re: questions on my tranformer test (Dr. William J. Schmidt, II)
>> 4. Fw: TRANSFORMER-TEST (Harold B. Mandel)
>> 5. Re: TRANSFORMER-TEST-webpage (kenw2dtc)
>> 6. Re: questions on my tranformer test (kenw2dtc)
>> 7. GS35 QUESTION (ON4IQ)
>> 8. Re: questions on my tranformer test (Steve Thompson)
>> 9. Re: GS35 QUESTION (Ian White GM3SEK)
>>
>>
>>----------------------------------------------------------------------
>>
>>Message: 1
>>Date: Sun, 12 Jun 2005 12:29:41 -0400
>>From: "Randy K4QO" <k4qo@earthlink.net>
>>Subject: [Amps] SBE SB1-LA Power out meter
>>To: <Amps@contesting.com>
>>Message-ID: <018201c56f6b$ef492820$6401a8c0@randyyf6hns82y>
>>Content-Type: text/plain; charset="iso-8859-1"
>>
>>Anyone out there in Amps-land know of a defunct SBE (SideBand Engineers)
>>model SB1LA linear that might have a working RF Output meter I can obtain
>>from it? (or perhaps the whole thing...)
>>
>>I have a restored SB1-LA in need of the stock meter. I have a generic
>>meter
>>in there now and while its not totally ugly (and it works) it would be
>>nice
>>to put the stock meter in there.
>>
>>Thanks and 73,
>>Randy
>>K4QO
>>
>>
>>
>>
>>------------------------------
>>
>>Message: 2
>>Date: Sun, 12 Jun 2005 14:39:52 -0400
>>From: "kenw2dtc" <kenw2dtc@comcast.net>
>>Subject: [Amps] questions on my tranformer test
>>To: <amps@contesting.com>
>>Message-ID: <000301c56f7e$1f12dee0$67612744@ken>
>>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=original
>>
>>Hi,
>>I'm trying to figure out the current rating of a plate transformer. This
>>is
>>my test setup:
>>
>>http://w2dtc.com/2005-0610-transformer-test-page.htm
>>
>>Questions:
>>1. Is this a valid way to find the secondary current capability?
>>2. Is the internal temperature of 180 degrees F too high for a
>>transformer
>>under load for 5 hours?
>>3. Is there a problem running this center tapped beast in a full wave
>>capacitive input configuration?
>>
>>Thanks and 73,
>>Ken W2DTC
>>
>>
>>
>>
>>
>>
>>------------------------------
>>
>>Message: 3
>>Date: Sun, 12 Jun 2005 14:11:50 -0500
>>From: "Dr. William J. Schmidt, II" <bill@wjschmidt.com>
>>Subject: Re: [Amps] questions on my tranformer test
>>To: "kenw2dtc" <kenw2dtc@comcast.net>, <amps@contesting.com>
>>Message-ID: <00dd01c56f82$a7209850$1600000a@SchmidtNet.local>
>>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=original
>>
>>I would think that the best way to tell is measure the wire size of the
>>secondary winding. The second best way is measure he cross-sectional area
>>of the transformer, as theoretically it is related to the power
>>capabilities
>>of the steel.... which you can back into current (after accounting for
>>reasonable efficiencies). 180F seems a little warm for a CCS
>>transformer...
>>maybe Will can weigh in here...
>>
>>Sincerely,
>>
>>Dr. William J. Schmidt, II K9HZ
>>Trustee of the North American QRO - Central Division Club - K9ZC
>>
>>Email: bill@wjschmidt.com
>>WebPage: www.wjschmidt.com
>>
>>"If computers get too powerful, we can organize them into a committee;
>>that
>>will do them in." -- Bradley's Bromide
>>
>>
>>----- Original Message -----
>>From: "kenw2dtc" <kenw2dtc@comcast.net>
>>To: <amps@contesting.com>
>>Sent: Sunday, June 12, 2005 1:39 PM
>>Subject: [Amps] questions on my tranformer test
>>
>>
>>> Hi,
>>> I'm trying to figure out the current rating of a plate transformer.
>>> This
>>> is
>>> my test setup:
>>>
>>> http://w2dtc.com/2005-0610-transformer-test-page.htm
>>>
>>> Questions:
>>> 1. Is this a valid way to find the secondary current capability?
>>> 2. Is the internal temperature of 180 degrees F too high for a
>>> transformer
>>> under load for 5 hours?
>>> 3. Is there a problem running this center tapped beast in a full wave
>>> capacitive input configuration?
>>>
>>> Thanks and 73,
>>> Ken W2DTC
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>>
>>
>>------------------------------
>>
>>Message: 4
>>Date: Sun, 12 Jun 2005 15:23:23 -0400
>>From: "Harold B. Mandel" <ka1xo@juno.com>
>>Subject: [Amps] Fw: TRANSFORMER-TEST
>>To: amps@contesting.com
>>Message-ID: <20050612.152329.2444.4.ka1xo@juno.com>
>>Content-Type: text/plain; charset=us-ascii
>>
>>
>>Dear Ken,
>>
>>You did a great job in investigating the transformer!
>>
>>Let's see: My PWD monster that took three tries to get right
>>from Peter is 12" high by 11" wide by 10 inches across, and weighs
>>167 pounds. It is a "hypersil" object rated at 0 - 1800 - 3000 volts,
>>at 3 amperes CCS.
>>
>>Peter had to do it over and over because he didn't wind a 3 ampere
>>CCS piece and I caught it when it arrived.
>>
>>Since I build monster power supplies I have learned the hard way
>>about component ratings, (almost electrocuting myself last Fall.)
>>
>>The one feature I see on your iron is that the windings are not
>>potted. This means the unit, as it heats and cools, absorbs moisture
>>from the air around it, said moisture settling in the paper laminations
>>and
>>in the wiring. To forestall disaster, I myself pot HV stuff, especially
>>transformers, chokes and coils.
>>
>>I found that the best stuff isn't too expensive: Dolph's Synthite AC-41.
>>
>>It's about 25 dollars a gallon and is made for HV insulation potting, and
>>has
>>the consistency of plain old varnish, but with much better breakdown
>>characteristics. There are several distributors and the stuff is made in
>>Monmouth Junction, New Jersey (732) 329 - 2333. For my 10KV
>>plants I use about 10 layers, either brushing or dipping.
>>
>>The test jig you set up is perfect for doing a preliminary examination.
>>Once you place the transformer into service I would suggest using
>>a mighty fan such as a Tarzan 320CFM, 230vac to move air around
>>the structure.
>>
>>>From your temperature observations I would concur that this is a 2 ampere
>>CCS
>>transformer.
>>
>>However, the acid test will be to actually construct a load bank. Your
>>calculation
>>of 6719.33 vac, after filtering, would yield 6047.40 VDC. (Applying the
>>0.9 factor).
>>
>>Since the power factor comes out to 12KW using around 3K of resistance, I
>>don't
>>know if you want to invest in a bunch o' resistors to do the test, but
>>let's figure
>>this transformer was made for broadcast use.
>>
>>Two 4-1000A's would need 2 amps at 6KV.
>>
>>You'll not probably melt the transformer down at 2 amps CCS, but if you
>>jump to
>>three amps and run AM 'Phone or RTTY it will get plenty hot.
>>
>>Just choose your rectifier bank carefully, Ken. Build it for 18KV,
>>minimum, at four
>>amps, minimum. Cool the diodes with that Tarzan fan, and then, let's
>>talk about
>>capacitors. Please don't tell me you're going to use photoflash
>>oil-filled caps
>>unless you see their voltage rating at 30% of what's written on the cans.
>>One screw-up
>>and the blown cap takes out your diode string and the transformer. I had
>>a huge argument
>>with my capacitor supplier about this and ended up backing up my argument
>>with
>>written evidence. The end result was that for the same money I was
>>shipped three times
>>the actual units to make up a 100 percent Working Voltage Direct Current
>>filter
>>instead of a Peak Voltage Direct Current filter. Your filter better be
>>rated at 12KV
>>also.
>>
>>Work Safely!
>>
>>Regards,
>>
>>Hal Mandel
>>W4HBM
>>
>>
>>------------------------------
>>
>>Message: 5
>>Date: Sun, 12 Jun 2005 15:53:03 -0400
>>From: "kenw2dtc" <kenw2dtc@comcast.net>
>>Subject: Re: [Amps] TRANSFORMER-TEST-webpage
>>To: "Harold B. Mandel" <ka1xo@juno.com>
>>Cc: amps@contesting.com
>>Message-ID: <002a01c56f88$58515dd0$67612744@ken>
>>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=original
>>
>>Hal said:
>>
>>"The one feature I see on your iron is that the windings are not potted.
>>This means the unit, as it heats and cools, absorbs moisture from the air
>>around it, said moisture settling in the paper laminations and in the
>>wiring. To forestall disaster, I myself pot HV stuff, especially
>>transformers, chokes and coils. I found that the best stuff isn't too
>>expensive: Dolph's Synthite AC-41. It's about 25 dollars a gallon and is
>>made for HV insulation potting, and has the consistency of plain old
>>varnish, but with much better breakdown characteristics"
>>
>>Sounds good Hal. I can't lift this transformer so painting would be best.
>>I guess I would apply a gererous amount on the top and let it drain into
>>the
>>windings and paint the bottom and sides. You mentioned 10 layers. Does
>>this mean you paint it, let it dry and paint it again etc., if so how long
>>is the drying period between applications?
>>
>>73,
>>Ken W2DTC
>>
>>
>>
>>------------------------------
>>
>>Message: 6
>>Date: Sun, 12 Jun 2005 16:07:20 -0400
>>From: "kenw2dtc" <kenw2dtc@comcast.net>
>>Subject: Re: [Amps] questions on my tranformer test
>>To: "Dr. William J. Schmidt, II" <bill@wjschmidt.com>,
>> <amps@contesting.com>
>>Message-ID: <004101c56f8a$574ad860$67612744@ken>
>>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=response
>>
>>Dr,
>>I agree with you on measuring the wire size; however, upon investigation
>>the
>>secondary terminals are fed with , thick flat copper bus which has much
>>more
>>area then the actual secondary wires, so I'm not going to tear open the
>>beast to find the wires. A couple of other gentlemen suggested that
>>maybe
>>the transformer has a 2 amp rating, so for the heck of it I will run the
>>test for another 5 or 6 hours at 2 amps and check the temperature again.
>>
>>73,
>>Ken W2DTC
>>
>>------------------------
>>
>>----- Original Message -----
>>From: "Dr. William J. Schmidt, II" <bill@wjschmidt.com>
>>To: "kenw2dtc" <kenw2dtc@comcast.net>; <amps@contesting.com>
>>Sent: Sunday, June 12, 2005 3:11 PM
>>Subject: Re: [Amps] questions on my tranformer test
>>
>>
>>>I would think that the best way to tell is measure the wire size of the
>>>secondary winding. The second best way is measure he cross-sectional
>>>area
>>>of the transformer, as theoretically it is related to the power
>>>capabilities of the steel.... which you can back into current (after
>>>accounting for reasonable efficiencies). 180F seems a little warm for a
>>>CCS transformer... maybe Will can weigh in here...
>>>
>>> Sincerely,
>>>
>>> Dr. William J. Schmidt, II K9HZ
>>> Trustee of the North American QRO - Central Division Club - K9ZC
>>>
>>> Email: bill@wjschmidt.com
>>> WebPage: www.wjschmidt.com
>>>
>>> "If computers get too powerful, we can organize them into a committee;
>>> that will do them in." -- Bradley's Bromide
>>>
>>>
>>> ----- Original Message -----
>>> From: "kenw2dtc" <kenw2dtc@comcast.net>
>>> To: <amps@contesting.com>
>> > Sent: Sunday, June 12, 2005 1:39 PM
>>> Subject: [Amps] questions on my tranformer test
>>>
>>>
>>>> Hi,
>>>> I'm trying to figure out the current rating of a plate transformer.
>>>> This
>>>> is
>>>> my test setup:
>>>>
>>>> http://w2dtc.com/2005-0610-transformer-test-page.htm
>>>>
>>>> Questions:
>>>> 1. Is this a valid way to find the secondary current capability?
>>>> 2. Is the internal temperature of 180 degrees F too high for a
>>>> transformer
>>>> under load for 5 hours?
>>>> 3. Is there a problem running this center tapped beast in a full wave
>>>> capacitive input configuration?
>>>>
>>>> Thanks and 73,
>>>> Ken W2DTC
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>
>>
>>
>>
>>------------------------------
>>
>>Message: 7
>>Date: Sun, 12 Jun 2005 22:09:00 +0200
>>From: "ON4IQ" <on4iq@telenet.be>
>>Subject: [Amps] GS35 QUESTION
>>To: <amps@contesting.com>
>>Message-ID: <001201c56f8a$9297a970$e8b9a451@PIV3000>
>>Content-Type: text/plain; charset="iso-8859-1"
>>
>>I have a 2m amp running a gs35 tube and a G3SEK triode board in it.
>>While runnning the anode at 3.2kv , i get good bias control and all is
>>well.
>>
>>Raising the voltage to 4.2kv off load gives met correct Ia when in
>>ptt, but once
>>the tube goes in cut off , the Ia drops to zero ( thats good) but
>>grid current goes
>>completely negative. After changing tubes with brand new one still
>>have the same problem.
>>
>>
>>I suspect there is something wrong in circuits or power supply.
>>I've checked power supply and find no leakage to ground.
>>
>>Would you have any idea where this negative grid current comes from
>>when tube is in cuttoff.
>>
>>Its abt 50ma.
>>
>>Best regards
>>
>>
>>Johan
>>
>>------------------------------
>>
>>Message: 8
>>Date: Sun, 12 Jun 2005 21:14:21 +0100
>>From: Steve Thompson <g8gsq@ic24.net>
>>Subject: Re: [Amps] questions on my tranformer test
>>To: amps@contesting.com
>>Message-ID: <42AC979D.1090406@ic24.net>
>>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>>kenw2dtc wrote:
>>> Hi,
>>> I'm trying to figure out the current rating of a plate transformer.
>>> This is
>>> my test setup:
>>>
>>> http://w2dtc.com/2005-0610-transformer-test-page.htm
>>>
>>> Questions:
>>> 1. Is this a valid way to find the secondary current capability?
>>I think so. Remember that what you have measured is the rms secondary
>>current - which defines the heating effect. The dc current you can end
>>up with depends on several factors but is likely to be 30-50% of the rms
>>value. Best check is with the Duncan Amps PSU designer which will tell
>>you the rms current in the winding for different configurations,
>>capacitor values and load resistances, but you will have to edit the
>>rectifiers file to create a diode with enough PIV.
>>
>>It's also worth checking how much it heats up with full primary volts
>>and o/c secondary, and derate the secondary current if necessary. I have
>>transformers that run cold like that, and others with noticeable iron
>>loss.
>>
>>> 2. Is the internal temperature of 180 degrees F too high for a
>>> transformer
>>> under load for 5 hours?
>>
>>I'll pass on that one - if you run it at 2.9A rms but, say, 50% duty
>>cycle then the temperature rise will be much lower.
>>> 3. Is there a problem running this center tapped beast in a full wave
>>> capacitive input configuration?
>>Depends on the insulation between the centre tap and the frame. If the
>>designer assumed the ct was going to be ground, it might not be rated
>>for it. I've lost a transformer that way.
>>
>>Steve
>>
>>
>>------------------------------
>>
>>Message: 9
>>Date: Sun, 12 Jun 2005 22:42:59 +0100
>>From: Ian White GM3SEK <g3sek@ifwtech.co.uk>
>>Subject: Re: [Amps] GS35 QUESTION
>>To: amps@contesting.com
>>Message-ID: <ffNtqvkjxKrCFAYo@ifwtech.co.uk>
>>Content-Type: text/plain;charset=us-ascii;format=flowed
>>
>>ON4IQ wrote:
>>>I have a 2m amp running a gs35 tube and a G3SEK triode board in it.
>>>While runnning the anode at 3.2kv , i get good bias control and all is
>>>well.
>>>
>>>Raising the voltage to 4.2kv off load gives met correct Ia when in ptt,
>>>but once
>>>the tube goes in cut off , the Ia drops to zero ( thats good) but grid
>>>current goes
>>>completely negative. After changing tubes with brand new one still have
>> >the same problem.
>>>
>>>
>>>I suspect there is something wrong in circuits or power supply.
>>>I've checked power supply and find no leakage to ground.
>>>
>>>Would you have any idea where this negative grid current comes from
>>>when tube is in cuttoff.
>>>
>>>Its abt 50ma.
>>
>>
>>What's happening is that with the higher B+, the tube needs a higher
>>bias voltage to cut it off. This voltage may be greater than the turn-on
>>voltage of the VDRs, so some current will flow through the VDRs.
>>
>>If you trace the current path back to B-minus, you will find that it
>>flows in the reverse direction through the grid current monitoring
>>resistor - that is why you see the apparent reverse grid current. You
>>will also probably find that the VDRs get slightly warm on standby
>>(careful!).
>>
>>If you know what is happening, this is actually not a big problem. I
>>suggest that you do not increase the VDR voltage, because the VDRs are
>>protecting the bias circuit from excess voltage.
>>
>>
>>
>>--
>>73 from Ian GM3SEK
>>
>>
>>------------------------------
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>End of Amps Digest, Vol 30, Issue 15
>>************************************
>
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