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Power transformer. Is this OK for electrostatic shield?
Power transformer. Is this OK for electrostatic shield?
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Old 20th December 2017, 10:52 PM   #11
trobbins is offline trobbins  Australia
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The shield can have a few purposes.

As this is a power transformer, and as you are bypassing the benefit of a split core, then the shield can become an extra safety mechanism by becoming a 'protective earth' barrier between primary and secondary (as required in some standards) - but that requires the shield and lead to be rated for earth fault current level (ie. the earth wire size that would be acceptable for the primary winding current rating/wire size).

For an electrostatic screen, then just one screen is corner cutting, as it forces capacitive currents from the primary side, and from the secondary side, to pass along the same leadout wire, and connect to the same grounding point. If you are wanting to route those currents to different parts of the equipment then you need two screens.

Capacitive currents are by nature higher in frequency, and so the screen should be designed with high frequency current flow in mind. That is better achieved by locating the lead-out wire in the 'middle' of the turn, and by using a layout that minimises the length of the lead-out wire.
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Old 21st December 2017, 07:22 AM   #12
Elerion is offline Elerion  Spain
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what do you mean by "corner cutting"?
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Old 21st December 2017, 08:42 AM   #13
AndrewT is offline AndrewT  Scotland
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Corner cutting = doing less than required.
regards Andrew T.
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Old 21st December 2017, 01:34 PM   #14
noSmoking is offline noSmoking  United States
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Power transformer. Is this OK for electrostatic shield?
Default shielding

Originally Posted by Elerion View Post
Yes, very interesting page. I already knew about it, and I also recommend it!
That's great!

I built a M2 I have never built a shield for a signal transformer,I did notice the pins on the side are too long and would touch anything wrapped around the sides so I clipped them off for clearence,So I have some MU steal ,do I just make a box with a top,does it need a ground to the board or soldered all around?

Mod if this should be in M2 thread please move it.

Last edited by noSmoking; 21st December 2017 at 01:36 PM. Reason: N/a
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Old 1st January 2018, 01:41 PM   #15
Elerion is offline Elerion  Spain
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I'm just using my first PT on a custom made SE KT88 !
It works as expected.
Filament voltage went a bit higher (7V unloaded) so I use a simple 2W 0.22ohm in series and get 6.35V with tubes.

Just the transformer buzzes.
Laminations are just hold together with four bolts. I plan on using yoke or even bells for vertical mounting. I've got bells for lay down, but I thinks that not an optimum choise because of EMI inside the (steel) chassis. Also tightly isolate one more turn with a thick isulation.

I don't plan impregnating the transformer. Too much mees for doing at home.

Any reccomend?
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