Flexible material suitable for high voltage (≥70kV) insulation

[blakeflynn]

I am hoping for some advice on materials to be used for insulating up to 70kV. I am doing some preliminary research for an application in the aviation industry, however I am not an engineer and need some guidance. I have looked at mica sheet, although to insulate against such high voltages it seems that the mica would have to be quite thick (and relatively inflexible). Any suggestions on other materials that may be suitable would be greatly appreciated.

 

[yungman]

70KV is way beyond my experience. I can only speak for lower voltage like 15KV or so. I use Dupont Flex circuit.

http://www2.dupont.com/Pyralux/en_US/assets/downloads/pdf/APclad_H-73241.pdf

I use the FR and AP before. Basically it's about 400V per mil. But I won't push it pass 150V per mil. So it's going to be really thick for 70KV if it even work. Even if you count on 1000V/3mil, the insulation thickness is 70X3mil=210mil. This is not going to be flexible.

Second, for high voltage, it's not only the insulation that is the problem. Creepage is 10 times worst for high voltage. Creepage is a conducting path created on the surface of dielectric material. This is affected by moisture, dirt, finger print oil etc. I remember the creepage distance for 12KV is like 3" to 4". That is much more critical in the design. An good luck on finding a connector. Even for 20KV, those Fisher connectors are huge because of the creepage.

You better find an expert to design this, I won't even dare to take this job myself. HV can get strange like RF.

 

[dlgoff]

Perhaps http://www2.dupont.com/Kapton/en_US/tech_info/index.html.

 

[yungman]

Don't quote me, I think the Dupont AP and FR are kapton stuff with coper cladding for flex pcb.

 

[Carl Pugh]

Silicon rubber, teflon, transformer oil, Mylar sheet...
However how you apply insulation at high voltage is as important as the insulation that is used.

 

[yungman]

Silicon rubber, teflon, transformer oil, Mylar sheet...
However how you apply insulation at high voltage is as important as the insulation that is used.

Yep, insulation of dielectrics is the least of concern. It is so hard to control the creepage. Dipping in transformer oil is good, but it is soooooooooo messy. Potting is very hard as any trapped air, impurity on surface form creepage inside. Potting expand or contract and pull components away. I tried potting on the surface mount boards and it destroyed the board.

If you can control the creepage ( BIG IF for 70KV), there is always a way to insulate the stuff. I don't even want to pretend that I know 70KV. It's like designing a 2GHz amplifier is so so different from designing a 500MHz amplifier. I can comfortably speak only up to 15KV. Believe me, 15KV and 5KV behave very different! Even at 15KV, components have to be ultra sonic clean, almost to clean room standard.

 

[dlgoff]

If you can use a liquid (oil=flexible material?) then you might be able to use the gas SF₆.

SF6 gas under pressure is used as an insulator in gas insulated switchgear

http://en.wikipedia.org/wiki/Sulfur_hexafluoride