Xentek 5kva isolation transformer runs hot! - diyAudio
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Old 11th October 2010, 05:05 PM   #1
lawname is offline lawname  United States
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Default Xentek 5kva isolation transformer runs hot!

I purchased a Xentek 5Kva isolation transformer from ebay. I configured this transformer as 120v in and 120v out. It runs hot! I cannot stand it when I hold my hand on it after 45 minutes of use. Any ideas?
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Old 11th October 2010, 08:15 PM   #2
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I assume you are testing it with no load. If it runs hot with no load, the reason could be the core is saturating or there is a shorted turn or more.

Put it on an inductance bridge and then short the secondary to see how much the inductance changes. A ratio of 1000 to 1 is not unusual and means you don't have a shorted turn. A slight change means a shorted turn.

If you don't have a shorted turn then the core is saturating. Recheck your connections to make sure you are really applying 120 V to a 120 V winding. Try connecting it to a higher voltage tap if you have one.
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Old 12th October 2010, 11:15 AM   #3
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by bob91343 View Post
Put it on an inductance bridge and then short the secondary to see how much the inductance changes. A ratio of 1000 to 1 is not unusual and means you don't have a shorted turn. A slight change means a shorted turn.
is there a compendium of these troubleshooting titbits?
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Old 12th October 2010, 11:28 AM   #4
AJT is offline AJT  Philippines
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how hot is hot? did you measure actual temperature rise?

how heavy is your traffo?

cores used for traffos have a definite core loss stated in watts per pound of core, these together with magnetizing and no load primary current contribute to a hot transformer......
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Old 12th October 2010, 11:57 PM   #5
lawname is offline lawname  United States
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Thanks for your reply! I have 120V receptacle on the output. I tried my Coda 2.5 class A power amplifier. It runs hot with or without the amplifier. I don't have the knowledge to try the way you mentioned at your reply. I connected it 120v in and out based on the diagram at the panel of this transformer. I will attach some pics. Maybe it will help an expert to understand the situation.
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Old 13th October 2010, 12:26 AM   #6
lawname is offline lawname  United States
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Default Xentek 5kva isolation transformer runs hot!

Many thanks for all your replies! I attached some pics. I think this will help you experts here understand the situation better. I followed the diagram at the panel of this transformer for 120v in and out.

I don't have any knowledge regarding this transformer other than that. I didn't measure the temperature. I touched it with my hand and couldn't hold it after its 45 minutes running with or without my coda class A amplifier.

Thanks, again. Jim
Attached Images
File Type: jpg Input.JPG (94.6 KB, 145 views)
File Type: jpg output to receptacle.JPG (75.2 KB, 136 views)
File Type: jpg the monster1.JPG (107.8 KB, 146 views)
File Type: jpg the monster 2.JPG (102.4 KB, 136 views)
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Old 13th October 2010, 12:30 AM   #7
lawname is offline lawname  United States
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This transformer weighs around 120 lbs.
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Old 13th October 2010, 12:32 AM   #8
lms is offline lms  Micronesia
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to dramatically reduce the core loss connect the transformer as 240v to 240v and use on 120v. You will have a cool running 2.5kw isolation transformer and save up to 50w of power at idle
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Old 13th October 2010, 12:39 AM   #9
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If I remember correctly a Model 5410 weighs about 42 pounds. This puppy has 0.005 pF leakage capacitance. I'll try to find the terminal wiring schematic.
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Old 13th October 2010, 12:58 AM   #10
lawname is offline lawname  United States
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Quote:
Originally Posted by lawname View Post
Many thanks for all your replies! I attached some pics. I think this will help you experts here understand the situation better. I followed the diagram at the panel of this transformer for 120v in and out.

I don't have any knowledge regarding this transformer other than that. I didn't measure the temperature. I touched it with my hand and couldn't hold it after its 45 minutes running with or without my coda class A amplifier.

Thanks, again. Jim
Note: The first two photos are from my 1kva Xentek. They have same diagram at the panel.
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