Author Topic: High temperature thin dielectric or insulating coatings for bare copper coils?  (Read 4513 times)

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Offline magicsmokeTopic starter

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Offline David Hess

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I would not even try it without using a vacuum during application.

My own experience is that a thick application will crack the insulating material or worse unless the temperature coefficient and elasticity are suitable.  Potting compounds tend to be very elastic which will not be suitable in this case.   Sometimes a more compliant base coat is used before a hard potting compound.
 

Offline magicsmokeTopic starter

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I actually found something that might work for the turn to turn insulation (CTD-201 Polyimide Coating, https://www.ctd-materials.com/wordpress/wp-content/uploads/2014/05/CTD201-Polyimide-Coating-December-2013.pdf). It looks like it is sprayable and suitable for complex shapes. Not sure if it can be made to wick inside which as David mentioned probably requires a vacuum system.
 

Offline magicsmokeTopic starter

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I would not even try it without using a vacuum during application.

Have you tried anything like this with a jury rigged/non-professional vacuum or VPI system?
 

Offline trobbins

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Yes, there will be increased AC resistance just because of the high frequency AC excitation (skin and proximity effects). The PWM harmonics will also add additional losses. I am going to try to build in some features to the coil to mitigate these losses.
Have you estimated Rac/Rdc for the operating waveform?  I can appreciate you may be able to modify proximity losses, but not skin effect.

If effective Rac/Rdc is more than say a few % increase, or you can't confidently model and do some form of prototype test confirmation of AC losses, then I can't see any merit in maxing out the single conductor copper area to aspire to a max slot fill %, to the detriment of a myriad of foreseen and unforeseen risks.  Perhaps you've looked at other practical conductor structures and assessed that a single conductor is the best outcome for your operating current waveform.
« Last Edit: February 13, 2020, 11:04:31 pm by trobbins »
 

Offline David Hess

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I would not even try it without using a vacuum during application.

Have you tried anything like this with a jury rigged/non-professional vacuum or VPI system?

I have always done it with a random vacuum pump and vacuum chamber.
 

Offline graybeard

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Are you derating the current capability of the copper for the higher operation temperature?
Are you accounting for the higher resistance of the copper at elevated temperatures?


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