Heat Shock & Peel test Enamel Copper Wire

there are several different types of insulating varnish or enamel. they are also some that are used as overcoats or in between coats. Depending upon the varnish used, the thermal rating of the wire will vary. Without knowing what material you are using, it is somewhat difficult to know what standard you are testing to.

Heat shock and peel test are two of many tests of magnet wire. The following link tells you about the various test.

Simply put, you elongate your sample, wrap it around a mandrel, and place in an oven set at 20 Celsius higher than the thermal rating of the wire. If it is 155C wire then the oven is set at 175c. After a period of time, the sample is removed and there should not be visible cracks. Cracks generally are an indication of over cure.

go to the web site in the following info more specific details. Richard

NEMA Magnet Wire Thermal Class Ratings File Format: PDF/Adobe Acrobat
This test is used to. evaluate the resistance to cracking of the film insulation. Some typical test conditions for copper magnet wire are: ...
www.spsx.com/uploadedFiles/News/White_Pa...al-class-ratings.pdf

Thanks for your advice. But our problem is that we don't get the results proper for only these two test the rest of the test are OK.
If you can help me how to achieve the results or the area where I work to get the better results.

I assume by not getting the proper results you mean that the wire coil when you remove it from the test oven is cracked. If that is the case then you are probably over curing the wire. Go to your process oven and check it out. Perhaps you can increase the line speed a little bit and the wire will pass heat shock. Other alternative is to decrease overall temperature and this will decrease wire cure.

How are your cut through values, DF values, etc. If they are very good (high) that would support the thought that you may be slightly overcuring the wire.

RB

Thanks . I will follow the procedure and reply.
Thanks again

Hello amirkhi,

We note that you are a process or perhaps chemical engineering consultant to the actual magnet wire manufacturer.

It is impossible for us to understand exactly how you are running your tests in the plant and your latest eleven word answer is surely not helping.

You did not confirm Spectre's comment:

"I assume by not getting the proper results you mean that the wire coil when you remove it from the test oven is cracked."

Spectre also asked:

"How are your cut through values, DF values, etc. If they are very good (high) that would support the thought that you may be slightly overcuring the wire."

You did not answer that!

Likewise you did not tell us anything about your recent experiments other than the fact that the insulation failed again somehow. We received no specific data from you at all in regards to what experimentation you did at the plant and we cannot read your mind! We don't even know if your insulation thickness is uniform! You have also not told us anything else such as the type of enamel, type of machine(s), if the problem is universal to a number of ovens or only one (Was that checked?), etc. etc.

How are we supposed to help you when you don't tell us anything except that you have a problem? We don't even know what standard you are referring to.

Because you have given us only the broadest general information, we can, in return, only give you very generalized technical advice:

(1) What you are going to have to do is set up a series of proper and tightly controlled experiments to prove or disprove the possibility that overcuring of the insulation is indeed occurring. We assume by this statement that you have good experience and training in the design of experiments.

(2) Once (1) is complete and if the problem is still not resolved, talk over the problem (with full and specific details) with the enamel manufacturer just in case you have a bad or very old lot of material.

Good luck with your experiments.

Kindest regards,
Peter J. Stewart-Hay (WAI Forums Moderator)
Principal
Stewart-Hay Associates
www.Stewart-Hay.com