Alternatives to potting HV planar transformer

Thread Starter

SiCEngineer

Joined May 22, 2019
299
I am developing transformers which have input voltage of 243V and outputs in region of 375-600V. I believe I will use planar transformers. The issue is that although these output voltages are relatively small, I need to isolate the transformer to 12kV. Usually this is done by fully potting the transformer with a silicon compound. I wish to avoid this option.

I have seen some propose that conformally coating each PCB in a high voltage compound before construction within the transformer will give 12kV isolation from the primary to the secondary and to the core.

I’ve had others say that simply adding some Kapton tape between the individual PCBs within the high voltage stack will provide the 12kV - however I do not see how it would provide isolation of the core from the windings.

I believe the conformal coating approach is best but will be more expensive as I will need to find some manufacturers within the U.K. who are able to provide the high voltage conformal coat and test it for the correct isolation.

Has any got any further advice on how best to approach this problem? Does anyone know of any reputable PCB manufacturers preferably within the U.K. who are able to perform these steps and test for high voltage insulation in-house?
 

Deleted member 440916

Joined Dec 31, 1969
0
I cannot imagine who gave you the idea that a single layer of Kapton tape would give you 12kV isolation, the same goes for conformal coating.

What exactly is this PHD course you said you were doing ?
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
I cannot imagine who gave you the idea that a single layer of Kapton tape would give you 12kV isolation, the same goes for conformal coating.

What exactly is this PHD course you said you were doing ?
Thanks for being so rude. I hope you managed to get out of that comment what you set out to achieve.
 

Deleted member 440916

Joined Dec 31, 1969
0
I don't think I was being rude, simply asking as you seem to be having some difficulty with basic concepts
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
I cannot imagine who gave you the idea that a single layer of Kapton tape would give you 12kV isolation, the same goes for conformal coating.

What exactly is this PHD course you said you were doing ?
I am always so hesitant to post on AllAboutCircuits because I know there are people like you on here. You could have easily managed to ignore my thread and go on with your day. Instead you chose to make me feel down. Congratulations it worked. If anyone is able to provide me further with a forum which does not judge others based on their knowledge I would appreciate the guidance.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
I don't think I was being rude, simply asking as you seem to be having some difficulty with basic concepts
You were being rude. End of story. I strive to learn more everyday and to say high voltage isolation techniques is a basic concept is ignorant and untrue. Like I said, I hope you obtained what you wanted from your comment.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
Hello,

Have a look at page 10 of the attached PDF for the electrical properties of kapton.

Bertus
Thank you very much for the data sheet Bertus it is appreciated. I believe the 0.075mm tape has above 12kV isolation. My primary and secondary boards will also be separated by air because they will be on separate PC boards of 2-4 layers each. I think my primary concern is achieving isolation between the primary and the core since the traces will be relatively close to the core. That’s why I was thinking maybe the PCB could be coated in some dielectric material so that it achieves the insulation in all directions.
 
I don't know if you've taken a look at the cross-section of 15kV MV cable before - but the insulation there is a lot thicker than 0.075mm. Said insulation also has a layer of semiconductive carbonacious rubber between the MV conductor and ground potential shield to eliminate air gaps which would otherwise be a source of insulation-damaging ozone in the presence of such a strong electric field.

Point being medium voltage is no joke. MV transformers are either immersed or potted in oxygen-displacing dielectric compounds for a reason. To my knowledge you'll never find a 13.8kV power transformer with bare windings exposed to the air.

Have you considered transformer oil and insulation paper as an alternative to potting? That would probably be the best and easiest way to get the tight tolerances you're talking about without running into issues from corona discharge.
 
Last edited:

shortbus

Joined Sep 30, 2009
8,732
This problem is also why I suggested in your other thread that a LOPT or similar stand alone transformer is more appropriate for these voltages.

If you think @fourtytwo was being *mean* to you, for putting down an idea, wait until you get into most workplaces.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
This problem is also why I suggested in your other thread that a LOPT or similar stand alone transformer is more appropriate for these voltages.

If you think @fourtytwo was being *mean* to you, for putting down an idea, wait until you get into most workplaces.
I find that insulting someones intelligence is quite mean. Whether I will be facing that in the workplace or not is hardly a fair comparison.

I should be okay with someone being mean to me, because other people will be mean to me in the future. What kind of mindset is that to have?
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
You'll see once you get away from *school* and start to live in the real world.
Yep, I've been living in a fake world this whole time. You do not know what I have been through, or anyone for that matter.
You must have a very sad life to be on a forum trying to push this agenda of how bleak life is following "school" and how I am being naive.

Get off your high horse. Done with this conversation, I didn't realise that I would be lectured by yourself and others by attempting to gain knowledge to become a better engineer. After all, isn't that what it's all about? :)
 

shortbus

Joined Sep 30, 2009
8,732
Get off your high horse. Done with this conversation, I didn't realise that I would be lectured by yourself and others by attempting to gain knowledge to become a better engineer. After all, isn't that what it's all about?
Come back in 20 years and reread what you just said.
 

Deleted member 440916

Joined Dec 31, 1969
0
I didn't realise that I would be lectured by yourself and others by attempting to gain knowledge to become a better engineer.
I am afraid if you are unwilling to take any notice of those with vastly more knowledge and experience than yourself then you will never become better at anything.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
I am afraid if you are unwilling to take any notice of those with vastly more knowledge and experience than yourself then you will never become better at anything.
That's exactly what I was attempting to do. This whole thread I was attempting to do that. But whatever.
 
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