Insulation temp ratings

[daleh007]

I have recently been looking at magnet wire for winding coils and have noticed a wide variation in the insulations temperature rating. There is a 200 degree C, 155 degree C and 135 degree C rating I have seen on wire insulation and wonder how much is enough. Does anyone know or have measured how how hot the coils can get and also how much temperature can the fiberglass they are housed in stand?

Daleh007  

[02coyote]

I was interested in this also, would it help to cast a hole in the middle of the coils so air could pass thru, ?  Also would more coils with smaller magnets produce less heat, or is the heat just proportional with the output?  Thanks

[Flux]

I think it makes sense to use the highest temperature grade you can get, I don't really know what temperature the polyester resins will stand long term, but it seems reasonable for 120deg C . Remember that the centre of the coils will be much hotter than the bits you can feel on the outside. Personally I would avoid the polyurethane coating (solderable) whatever temperature grade it is quoted for. The other coatings die slowly with heat and will continue working for years when cooked. Above a critical temperature polyurethane decomposes producing toxic gas and leaving bare copper.

I doubt whether leaving the centres of the coils un potted will have much effect on the temperature rise.

[treab]

My suggestion is to use the 200C wire for the price difference. Having said that chances are

your insulation system will never approach that. A class F insulation system is 155c. That means

at full load and an ambient of 40c the insulation system will not exceed 155c. When buying magnet wire

look for spike resistant wire i.e.. inverter duty. You know the phrase, an ounce of prevention.....

Regards