[Amps] Fw: Another Plate Transformer Question

[Will Matney]

John and Don,

Is those overall dimensions you gave, or core dimensions from the catalog? If core, something sure dont jive right by calculating it. To be honest, they sound to me like overall dimensions, and by the voltage and current rating, be about right. The reason being, it's going to drop the core depth about 4 inches or so on my calculation by removing the endbells. 8 inches deep for the iron core itself (not counting endbells, just the lams) sounded to me to be too much. At a 1.75 or 2 inch tonge, it should have been like 4 inches deep, maybe 5 at the most. If that's right, I'll re-calculate it. The way it stands now is the transformer would be good for 2205 Vdc (from 1560 AC) using a full wave C.T. at 200 mA, or 441 watts. Being it's for 50 Hz operation also will raise the core size some but not a lot. However, using a core at 2" X 4" gives 8 square inches and is a 2500 watt core (at 60 Hz) even back as far as the 20's they used the same formula. At 50 Hz, it's good for 1722 watts. The old RCA formula for 60 Hz was;

a = sqrt of P / 5.58

Using 2500 watts;

sqrt of 2500 / 5.58

50 / 5.58 = 8.906 square inches which is almost a sq. inch over a 2 X 4 core at 8 sq inches but still in the ball park.

Using the 0.16 formula gives 8 sq inches for 2500 watts at 60 Hz.

The difference between 50 Hz and 60 Hz is a factor of 1.2 so it still dont add up. I'm wondering if something still isn't measured right? In other words, something is way off on that transformer as compared to the equations used to derive its size. That's all I can do on the calculation without knowing everything exact in measurement.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 5/5/05 at 8:52 PM John Finner wrote:

>Don
>
>And The Master 23rd edition Thordarson section says:
>T-21P83
>1560-0-1560
>1250-0-1250
>@ 200 ma DC
>Pri 117 V 50/60 cps (I know, I know)
>Secondary voltage changed by primary tap.
>Static shield.
>Size H 6"  W 4 3/4"  D 8 1/2"
>Mtgs cntrs 7 5/8" x 2 3/4"
>
>John, WA4EPI
>
>> Date: Wed, 4 May 2005 09:13:40 -0500
>> From: "Don Lemley" <w8hrq at comcast.net>
>> Subject: [Amps] Another Plate Transformer Question
>> To: <amps at contesting.com>
>> Message-ID: <00bc01c550b3$79291230$6bfea8c0 at HamBone>
>> Content-Type: text/plain; charset="us-ascii"
>> 
>> I just ran on to a HB power supply that looks to have been built for a
>> tetrode amp of some sort, with hollow state electronic regulated 350V
>> screen supply, etc.
>> However, I don't know the actual ratings on the plate xfrmr, and the
>> power supply needs several electrolytics replaced, etc before I can
>> bring it up.
>> My question is, does anyone know the specs on a Thordarson T-21P83 plate
>> xfrmr?  I have checked the catalogs that I have been able to find,
>> including the 1938/39 and 1942, as well as the newer Catalog #76, but I
>> don't find any reference to this puppy.  My guess is that this thing was
>> designed for a half gallon amp, but the screen supply is much too large
>> for that, and the plate transformer also looks to be a little large for
>> a half kw, so I could use some help if someone has a catalog that lists
>> this thing.
>>  
>> Many thanks in advance,
>>  
>>             Don
>>  
>> Don Lemley - W8HRQ
>> w8hrq at comcast.net
>
>
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