Xentek 5kva isolation transformer runs hot!

[lawname]

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?

 

[bob91343]

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.

 

[AndrewT]

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?

 

[TonyTecson]

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......

 

[lawname]

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.

 

[lawname]

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

 

[lawname]

This transformer weighs around 120 lbs.

 

[lms]

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

 

[Speedskater]

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.

 

[lawname]

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.

 

[bob91343]

That is one big transformer! I can't imagine why you'd want to use such a thing.

If it runs hot it must have a shorted turn. If you have a wattmeter, measure the power draw with no load. Obviously it's high or you wouldn't have that much heat.

I submit that the thing is defective.

 

[bob91343]

AndrewT, looking for a compendium of troubleshooting tidbits - well just ask me. I have more information in my head than even I can believe. Seriously, these things require a certain talent to invent. For instance, I invented (I am sure I'm not the first) a method of discovering where a break is in a shielded cable. It's usually at one end but my method finds it without cutting or piercing, within an inch or so.

It also helps that I have a degree in Electrical Engineering, have been a radio amateur for over 60 years, and owned an electronics repair shop for many years.

 

[AndrewT]

how about writing a transformer Wiki?

 

[TonyTecson]

to dramatically reduce the core loss connect the transformer as 240v to 240v and use on 120v.

this makes a lot of sense if you are not using the full 5kva rating of your isolation traffo..

 

[johansen]

is your line 120 or is it 125?

dropping the line 10% will drastically cut core losses.

 

[ktuuri]

to dramatically reduce the core loss connect the transformer as 240v to 240v and use on 120v.

Yes, it will run cooler and may benifit your system having your amp on Balaned power.

 

[PineappleDave]

It’s 111 lbs as per specs and I do have one it’s one helluva block of iron.