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Heat Shock test For Magnet Wire
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TOPIC: Heat Shock test For Magnet Wire

Heat Shock test For Magnet Wire 2 years, 3 months ago #299

I am having problem with Heat Shock of Wires produced with different wire enamels.

I do have some knowledge regarding production of magnet wires and I have already tried quite a few combinations but I am still far away from a solution.

The enamels I have tried are produced by known and reputed manufacturers of the world such as Hitachi in Japan and Malaysia, SIVA in Italy, Schenectady in the USA, Altana in Italy and so on.

I have tried different temperatures in the oven and different speeds.

I have tried variable passes in the oven ....all the results are OK but heat shock!

I have also tried Polyester-imide based,PVF based varnish and have checked as per relevant BSS Specs but the results are still the same.

If you need any other details please inform.

Thanks.

Re: Heat Shock test For Magnet Wire 2 years, 3 months ago #300

Hello,

For a start, we suggest you read this two page WAI Forums thread from 2006 very carefully:

www.wireassociation.com/forum/viewmessag...orum=8&Topic=277

Likewise please note the comments regarding the Dansk system for tangent delta equipment www.dse.dk and the pull mandrel test.

Since you have tried many enamel manufacturers, it would seem to us that it is indeed your process. We would guess that you are slightly over curing the enamels.

Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

Re: Heat Shock test For Magnet Wire 2 years, 3 months ago #301

What ever came of this heat processing idea? I am anxious to hear a little bit more about what happened and why this process was not going according to plan?


C

www.bwire.com/

Re: Heat Shock test For Magnet Wire 2 years, 3 months ago #302

Peter,
I'll comment tomorrow. I've tried twice and don't know where my repy went. Will do in word and then paste.
richard

Re: Heat Shock test For Magnet Wire 2 years, 3 months ago #303

Hello,

Heat shock is generally thought of as a test of cure (or over cure). As you say the enamels you are using are from reputable companies. You take a sample, elongate it some, wrap it around a mandrel, and then place in a lab oven for a period of time at a temperature that is 20 degrees hotter than the thermal rating of the wire.

Over the years I have learned a few things:

1) Get input from the enamel supplier as to suggested temperature profile in the oven.
2) Get input from the oven manufacturer regarding what they think are good temperature speeds.

The best performance occurs when you set the temperature profile, air flow, fan speed, and wire speed for each type enamel and wire size. This means you are operating at optimal conditions.

If you try to run all products and enamels and only vary the speed, you compromise production and quality.

There is no normal reason that I can think of that all of your enamels would fail heat shock. My first thought is that I would check the accuracy of my test oven. Normally heat shock tests are 20 degrees over the thermal rating of the wire for a specific time. If your oven is off even a little it would make a difference.

If the lab oven temperatures are good, then you need to look at your oven. Maybe you have a hot spot or the wire is dragging on the oven or touching a heating element (assuming they are in the wire chamber).

- Is the wire centered in the wire chamber?
- Is it too close to one wall?
- Are you running the oven too hot?
- What kind of oven are you using? Electric? Radiant? Recirculating? Single direction air flow?
- Does the air flow with the direction of the wire or against the movement of the wire?

There are a lot of questions that perhaps you can answer.

Richard

Re: Heat Shock test For Magnet Wire 2 years, 3 months ago #304

For a definition of Heat shock go to www.spsx.com/uploadedFiles/News/White_Pa...al-class-ratings.pdf

The idea behind heat shock is to see if rapidly changing the temperature of the wire will make it fail. Typically you elongate the wire, make a coil, hang in an oven heat opeating at 20 degees C above it thermal rating of the wire. After a period of time you remove the sample, let it air cool and check for cracks in the insulation. You mention BSS specs - is that a Boeing spec. Exactly what is that standard. If it exceeds the basic NEMA heat shock requirements your samples may fail. In NEMA once you reach 200 degree rated wire the oven temp is the same as the rating of the insulation. If it placed in an oven that is too hot or stays in too long it will fail!
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