HV Transformer Winding / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

HV Transformer Winding

1 2 next

Move Thread

LAN_403

Phil T

Thu Apr 23 2009, 07:14PM

Registered Member #1974 Joined: Mon Feb 16 2009, 10:28AM
Location: United Kingdom
Posts: 9

Hello.
I am currently rewinding a HV transformer (details can be seen here

) and I am uncertain which way (clockwise or counter clockwise) the two secondary coils should be wound.
I have one on each outer leg with the primary in the middle. I know there are issues with my design, in so much as the centre primary leg has eight sq inches of core while both the outer secondaryâ€™s only have four square inches each. But I can still get 1 volt per turn on the secondaryâ€™s with this setup (as explained in my link)

I wonâ€™t be connecting the inner ends of the secondaryâ€™s to the core as it will all be in an insulated plastic tub under oil, but with the inner turns of each coil at zero volts it is easier on the insulation. I will be connecting the secondaryâ€™s in series but I want their inner most ends to be a zero volts , so do I need to wind one secondary anti-clock and the other clockwise, or wind both in the same direction. Iâ€™m 99% certain I need to wind one clockwise and the other anti-clock, I just want to check before itâ€™s too late !

Regards

Phil

Dr. Dark Current

Thu Apr 23 2009, 07:20PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Why do you think all transformers are wound with the windings only on the center core leg? It's because you get the most power out of it this way.
Or is there a different reason why do you want to wind it like this?

Finn Hammer

Thu Apr 23 2009, 08:54PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Phil,

I have been thinking long and hard, but everytime I am close to a conclusion, my head starts to explode, and I have to start over.
So I will advice you to do what I would do myself:

Energize the primary, and make a couple of nice test windings with some of the scrap insulated wire you have stashed away for this purpose.
You only need some 5-10 turns to settle the matter, really.

Hope this helps,
Cheers, Finn Hammer

Phil T

Thu Apr 23 2009, 09:03PM

Registered Member #1974 Joined: Mon Feb 16 2009, 10:28AM
Location: United Kingdom
Posts: 9

Hi
As I explained in the link the window size was not big enough to adopt the 'norm'. Originally it was 8.25Kv when the secondary was wound around the primary as per normal. The window though was not big enough for many more windings, I could have pushed 9kv at the most. As the secondary was faulty anyway when I got the tranny (for free - thanks Bob) it had to be rewound anyway.
The core size was ideal, but I wanted to get a slightly higher voltage. The basic spec' (8.25k output) assumes UK 230v input but because ballasting would be needed I may have ended up with 6K / 7K etc. I will use mainly L ballast but it will still drop some volts.
The layout is inefficient, I know that, I'm just after maybe 11k /12K at the end of the day, but the important thing is that it will give me a decent current instead of lugging 3 or 4 NST's around for my coil.
I can still get 1 volt per turn even with this setup (It was 2 volts per turn when wound around the primary) I am led to believe that the inefficiency may also help to limit the short-circuit current - that remains to be seen though.
The one secondary that I have wound today has 4758 turns. As the primary is 130 turns, a theroitical output would be 4785/130 = 36.8 * 230v = 8.46k each side. If in practice I get 6k each side (12k total) Iâ€™ll regard it as succesfull.

Anyway can you answer my original question ?

Regards

Phil

Plasma Lover

Thu Apr 23 2009, 09:17PM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

Phil,

I think thisis going to requiresome trial and error. Is there any chance you could make a small test winding on the core (like twenty primary turns with a small wire diameter and two secondary windings with twenty windings a piece) you coulduse a current-limited transformer at around 5 to 100 volts input, with less than 100W, preferably, and then arrange the secondaries as needed to get double the voltage thatone reads on a meter alone. Although, the lead you select to test does matter when it comes to your final setup, so I cannot think of an effecient way of compensating for that.

Good luck,
Christopher

Phil T

Thu Apr 23 2009, 09:17PM

Registered Member #1974 Joined: Mon Feb 16 2009, 10:28AM
Location: United Kingdom
Posts: 9

Hello Finn
It's not quiet as easy as that - unfortunatelly.
I have yet to wind a new primary. The original bifilier one (I'm replacing it with an identical setup, turns and wire gauge) got a bit worse for wear after several rewinds trying differant setup's, and is currently awaiting a trip to the scrap yard . The lathe (my winding machine) is all setup for the next secondary, and I don't really want to break it all down to wind the new primary, or even put the old back temporay, and then have to set it all up again for the other secondary.
I may have enough small gauge scrap to wind a low-voltage primary though that would not need many turns and that could be done by hand.

I think â€œFlemings Right Hand Ruleâ€ gives the answer, but the beer upsets things <grin>

Sulaiman

Thu Apr 23 2009, 09:23PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

If you make it so that a secondary can be turned 'upside-down' it doesn't matter!
If the voltage is the wrong phase just turn the winding around (top = bottom etc.)
If you want the start of each winding at the same 'end' of the transformer then wind in opposite directions.

The flux in both arms is in the same direction.

Phil T

Fri Apr 24 2009, 07:08PM

Registered Member #1974 Joined: Mon Feb 16 2009, 10:28AM
Location: United Kingdom
Posts: 9

Hello.
I only tried the one arrangement for a test coil that you can see here.

This is what was expected and as Sulaiman states it is the only setup that will give you the zero volts end's of each coil, located both at the same end of the core. It is also the one that NST's use as well I expect, except the zero common point is tied to the core.
I didn't try any other combinations as the temporary coil I made was rather delicate.

Regards

Phil

klugesmith

Wed May 06 2009, 07:28PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Phil,
It looks like you and Sulaiman got the winding directions straight. As he/she pointed out, the flux in both outer legs is in the same direction. We could imagine the center-tapped secondary as starting at one extreme, winding to the zero-volt tap and making that connection, continue winding in the same direction [and jump to other leg of core] until reaching the other extreme end.

Those of us in countries with 60-Hz mains can enjoy the luxury of 17% fewer turns per volt.

The workmanship and pictorial presentation of your rewinding project are spectacular; thanks for sharing.
What tool did you use to draw the winding_direction.jpg illustration?

Rich

twist2b

Wed May 06 2009, 07:35PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

One of his links pointed here:

Figure (9). - Instantaneous polarity depends on direction of winding.
Look at that figure... theres your answer, you can see its effect 100%

No guesswork necessary.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob