Article to test power transformer current?

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Article to test power transformer current?

Postby Blair » Sun Jan 19, 2014 5:30 pm

Can we put a sticky up somewhere:)?

I can never find the article. I have a power transformer with 900VCT and 55 ohms DCR across the winding. I'm trying to determine the max secondary current for this transformer.

It also has 800VCT taps, do that's more likely what I will use.

Thanks!

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Re: Article to test power transformer current?

Postby DeathRex » Sun Jan 19, 2014 6:45 pm

Capacitor input about 240ma, choke about 320ma. Loaded your voltage should go down to 873.

viewtopic.php?f=4&t=1465&start=15
Last edited by DeathRex on Sun Jan 19, 2014 6:52 pm, edited 1 time in total.
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Re: Article to test power transformer current?

Postby Blair » Sun Jan 19, 2014 6:50 pm

I have some UTC iron that I know to be at least 300mA HV into a choke input with twice the DCR of this thing. It's not potted and could be use as a chock block for a tank. I think it will do better than that.
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Re: Article to test power transformer current?

Postby DeathRex » Sun Jan 19, 2014 7:00 pm

BIg question, how heavy is it? Should be 12-17 pounds, depending on how many secondaries and what current they are. I got a postage scale from an antique shop to check these things. I have 2 lights that go over the sink, one takes 4 lamps, one takes 3. All the lamps are connected in series, the most I can put on them is 840 volts. I have a bunch of 15, 25, 40, 43(60 watt halogen), 55(75 watt halogen) and 60 watt lamps to put a load on the transformer under test. Let it cook for 4 hours and see how hot it is.
How big is it? When one of the dimensions get to 6 inches, it's a big transformer.
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Re: Article to test power transformer current?

Postby Blair » Sun Jan 19, 2014 7:14 pm

Image

Dude, it's big. I own output transformers bigger than most folks have seen for power iron. That's not bragging, but I'm saying I know average power transformer sizes. This thing dwarfs the Bogen MO-200 power transformers I have.
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Re: Article to test power transformer current?

Postby DeathRex » Sun Jan 19, 2014 7:32 pm

I'd probably put that one on the bathroom scale. Did you see the link I put in? I'll put it here too.

viewtopic.php?f=4&t=1465&start=15

http://www.audiophool.com/Misc/XFMR1.JPG
http://www.audiophool.com/Misc/XFMR2.JPG
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Re: Article to test power transformer current?

Postby DeathRex » Sun Jan 19, 2014 7:43 pm

I tried the article out with a known 830CT transformer that's 3 1/2 X 4 1/2 X 4 7/8, that's 11 pounds. It reads 76 ohms and comes out to about 180ma, which is what it is rated at. It also has a 6.3V 5A, 6.3A 1.2A, and 5V 3A secondaries.
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Re: Article to test power transformer current?

Postby DeathRex » Sun Jan 19, 2014 8:01 pm

Check the 800 volt resistance too, it might be vastly different than the 900. On my conn organ transformer, the secondary is 410-305-24-0-24-305-410. The 610 volt secondary will do 350ma. The 820 is only good for 100ma.
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Re: Article to test power transformer current?

Postby Blair » Sun Jan 19, 2014 9:06 pm

It's not like that one. It's 49.3 ohms across the 800vct taps.
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Re: Article to test power transformer current?

Postby DeathRex » Mon Feb 03, 2014 8:52 am

What did you find out Blair? I just got a 800 volt kinda high current amp 250ma. It's 3 3/4 x 4 1/2 x 5 1/2, the same length and width as a ST70 power transformer, but alot thicker. It has just the one secondary and measures 32 ohms across it. According to the table it should be good for 250ma cap input. It is alot smaller than yours, but I'm wondering why yours has such a high secondary resistance?
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Re: Article to test power transformer current?

Postby Blair » Mon Feb 03, 2014 9:07 am

I took it apart to do cosmetics on it. Then it got cold. I'm a Texan. We don't go outside, except to get beer if its below 50F :)

I will play around with it when I reassemble and let you know. I will not keep it. I have way too much power iron!

Blair

It's also a tough one because of the case. It's big, but the case makes it look bigger.
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Re: Article to test power transformer current?

Postby kheper » Mon Feb 03, 2014 9:31 am

I combined the two images of the Rating unknown transformers article, and I'll archive it below:

http://nekhbet.com/trans_rate.jpg
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Re: Article to test power transformer current?

Postby Blair » Mon Feb 03, 2014 10:26 am

Thank you! I will bookmark it:)
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