Jump to latest posthow do you demagnetize a transformer?
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Junior Member
Posted January 13, 2019
Pro Subscriber
how do you demagnetize a transformer?
Junior Member
Posted January 15, 2019
Pro Subscriber
Some winding resistance test sets have a demag functionOriginally Posted by jaycee91
Junior Member
Posted January 17, 2019
Pro Subscriber
Use a car battery and let the current flow through the winding.
Junior Member
Posted January 23, 2019
Pro Subscriber
So DC current is the answer?
Experienced Member
Posted January 23, 2019
Pro Subscriber
AC or DC can be used. AC amps applied close to the excitation knee and slowly lowered can demag, and long tedious alternating of lowering DC currents can demag. Edit: I would highly recommend using AC
Previous TestGuy thread about it:
https://testguy.net/threads/2749-Cor...nsformer-cores
Article on importance of demag xfmrs with AC explanation:
https://www.tdworld.com/substations/...nsformer-cores
NETA Level III
Posted January 23, 2019
Pro Subscriber
More like alternating DC, which is effectively AC - just not the 60Hz frequency you might be used to. You can use a car battery to pass current thru a winding in different directions, if you watch a winding resistance test set de-mag function you can see the process in action.
An example would be something like this:
+10A
-10A
+7A
-7A
+5A
-5A
+3A
-3A
+1A
-1A
This isn't exact by any means, I'm just trying to show an example. I'm sure you can also use regular AC voltage but a car battery was mentioned earlier and that's how I was originally taught. Also winding resistance sets usually operate off DC which is why the above method is used. As far as I understand you only need to perform this on one winding to de-mag a polyphase transformer.
