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Old 14th Sep 2006, 3:23 pm   #1
DoctorWho
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Default EHT Electrical Insulating Resin or similar

Does anyone know of any kind of electrical insulating resin that could be used to repair broken terminals on EHT transformers and the like which could be used to repair breaks/damage in the original insulation?

The nearest reference I have been able to find is this:

http://www.pitchcare.com/shop/product.php?id=3709

But this doesn't look quite right. I've tried Araldite but it does not seem to insulate EHT voltages, so any suggestions greatly appreciated.

Any substance which sets hard and will insulate would do the job.

Many thanks.

Peter.
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Old 14th Sep 2006, 3:45 pm   #2
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Question Re: EHT Electrical Insulating Resin or similar

Sorry, but I can't hep you on that - but I must ask - since "Araldite" immediately sprung to mind before I reached the end of your Post - in what way does the Araldite fail? Arcing over within? Catastophic insulation failure? Catching fire? Mechanical disintegration? Or?

I ask this because I would have used Araldite without any hesitation whatsoever! So, I need to learn - and, hopefully save myself a big headache one day!

Al.
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Old 14th Sep 2006, 4:55 pm   #3
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Default Re: EHT Electrical Insulating Resin or similar

Well I thought pretty much the same as you in this, but Araldite seemed to act like a conductor rather than an insulator, it made me wonder what exactly it's made from? The arcing increased with Araldite, so it would seem that, when you're talking EHT type voltages Araldite is perhaps not a good insulator?

Any other suggestions greatly appreciated.
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Old 14th Sep 2006, 5:18 pm   #4
Sean Williams
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Default Re: EHT Electrical Insulating Resin or similar

Hi Peter,

I would suggest potting compound - available from RS, or black silicone sealant (the stuff without acetic acid) - I have used both at up to 3000v and they appear to be ok.....

Cheers
Sean
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Old 14th Sep 2006, 5:45 pm   #5
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Default Re: EHT Electrical Insulating Resin or similar

Quote:
Well I thought pretty much the same as you in this, but araldite seemed to act like a conductor rather than an insulator, it made me wonder what exactly it's made from?
Then you must have a conducting type or perhaps mixed it badly. I'm sure it can be a good insulator as it has been used for potting.

If solidity is not an issue then silicone rubber "bath seal" definitely works, but again you have to use the right kind, which I think is the one called "low modulus" - anyway, it's the one that does NOT smell of acetic acid. I used it to pot a 10kV multiplier which would not work in the air at all.
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Old 14th Sep 2006, 5:51 pm   #6
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Question Re: EHT Electrical Insulating Resin or similar

Quote:
Originally Posted by m1ecy View Post
I would suggest potting compound - available from RS,
Sean
Yes, I've used the RS potting compound too - although not to HV levels.
Now I could be wrong on this, but to me, the RS potting compound looked like, acted like, smelt like and set like - Araldite!

Hmm.

Al.
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Old 14th Sep 2006, 5:56 pm   #7
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Question Re: EHT Electrical Insulating Resin or similar

Quote:
Originally Posted by DoctorWho View Post
The arcing increased with araldite, so it would seem that, when you're talking EHT type voltages Araldite is perhaps not a good insulator?
Hmm. I'm fascinated.
Was the arcing inside the Araldite, or running along its surface?
Were there cracks in the Araldite or other forms of mechanical deterioration visible?
There are many types of Araldite available. What one did you use?

Al.
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Old 14th Sep 2006, 6:04 pm   #8
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Default Re: EHT Electrical Insulating Resin or similar

Did you clean all traces of charring or dirt from the area before adding the Araldite?

Once spotlessly clean, have you sprayed the area with an anti-corona insulating lacquer?

Steve
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Old 14th Sep 2006, 9:49 pm   #9
Danny
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Default Re: EHT Electrical Insulating Resin or similar

When I was younger and short of dosh, I used to mend Grundig green triplers with Araldite.
Quite a few sets were done with this and only one fire!
This was put out and a new tripler fitted.

Not to be done now though - COSHH, BEAB, etc.
24kv was the voltage so it should be OK.

Danny
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Old 14th Sep 2006, 10:02 pm   #10
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Default Re: EHT Electrical Insulating Resin or similar

Notice that Araldite may not be suitable in high-temperature applications. The common types softens at relatively low temperatures.

Frank N.
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