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What are these & what can I use it for?

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gary350

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I assume this is a new technology ferrite material transformer that replace old technology EI core transformers?

This one has 6 windings. 5 taps, 3 taps, 2 taps, the other side has, 3 taps, 2 taps, 2 taps. All 6 windings have the same size wire #22.

What is the copper strap around the center do?

Can I rewind this to be a 100KHz choke & will it work as good or better than a donut shape choke?

How do you spell toroid spell check & google say it is wrong no matter how it is spelled?

 
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Nigel Goodwin

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It's a switch-mode transformer, for high frequency use, you can't use it at normal low frequency mains - 50/60Hz.

As for 'new technology', 'new' I suppose compared with low frequency transformers, but still decades old.
 

MaxHeadRoom78

Well-Known Member
Even for linear 50hz/60hz power supplies, Toroidal power transformers have replaced the EI version to some degree, in this case they are coiled laminated steel , not ferrite.
Nice because they are relatively easy to modify or add the secondaries.
The copper strap is probably for shielding.
Max.
 

gary350

Well-Known Member
I checked all 6 winding this is what I got, .180mh, .177mh, 110mh, .060mh, .047mh, .005mh. If I connect all these windings in series I get, .579uh. I need a .4mh choke. If I only connect .180 + .177 + .047 = .404mh that is close enough but #22 wire is too small for 50 amps at 102KHz..
 

ronsimpson

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The transformer was dipped in varnish, so it will not come apart nicely. (It will brake first)
If you wanted to reuse it in your project, you need to remove all the wires and rewind.
 

debe

Active Member
pulled plenty apart for rewinding, used an old microwave oven to get them apart.
 

Nigel Goodwin

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Even for linear 50hz/60hz power supplies, Toroidal power transformers have replaced the EI version to some degree
Sorry, I don't quite see the relevance?, the device in question isn't toroidal - and 50/60Hz toroids are still relatively rare, presumably due to their higher cost?. Toroids also have other disadvantages, such as greatly increased power-on surges, with soft-start circuits required on larger amplifiers. However, they have many advantages as well, and are pretty damn cool! :D

There was also a 'half way' design as well, C-Core transformers, which gave some of the advantages of both types.
 

ChrisP58

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I checked all 6 winding this is what I got, .180mh, .177mh, 110mh, .060mh, .047mh, .005mh. If I connect all these windings in series I get, .579uh. I need a .4mh choke. If I only connect .180 + .177 + .047 = .404mh that is close enough but #22 wire is too small for 50 amps at 102KHz..
If you actually connected them in series when you measured them, you'd find that the inductance was much higher than .579uH. While the inductance's of two discreet inductors add if put in series, multiple windings on the same core, connected in series and in phase, are effectively a single winding. Since the inductance of an inductor is calculated based on the square of the turns, two 10 turn windings on the same core that each might have 1uH each, will have 4uH when connected in series.
 

gophert

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I checked all 6 winding this is what I got, .180mh, .177mh, 110mh, .060mh, .047mh, .005mh. If I connect all these windings in series I get, .579uh. I need a .4mh choke. If I only connect .180 + .177 + .047 = .404mh that is close enough but #22 wire is too small for 50 amps at 102KHz..

There is a lot more to selecting an inductor than inductance. You will need to understand the magnetic saturation and ripple - especially since your application is looking at 50 amps.

Also, eddie current heating of your inductor's core material. Selecting insulated iron powder (annealed iron vs "hard" iron (e.g. see Micrometals cores)) vs ferrite vs laminated silicon steel (note that frequency makes a huge difference. Each will perform differently even in the same size or core geometry.
 

gary350

Well-Known Member
If you actually connected them in series when you measured them, you'd find that the inductance was much higher than .579uH. While the inductance's of two discreet inductors add if put in series, multiple windings on the same core, connected in series and in phase, are effectively a single winding. Since the inductance of an inductor is calculated based on the square of the turns, two 10 turn windings on the same core that each might have 1uH each, will have 4uH when connected in series.
This explains something I have been wondering about. I have been thinking my meter has something wrong with it, or bad connector or something? I wound 6 chokes so they all have the save value. If I solder them together is series they add up sorta close depending on how close they are to each other laying on the work bench. With 20 turns of wire on each choke I get .1mh. and 6 in series is .6 mh. If I remove all the wire from each toroid then stack 4 toroids together about 14 turns of wire gives me .45mh.

I checked the value of this transformer on 1 side. Meter takes about 15 seconds to finally decide what the value is. Value slowly climbs then stops. Left to right I get, .240 .330 .440mh. After soldering .240 in series with .330 their values change to .280 & .370 and the total value of the 2 in series is .670mh. .240 .330 .440 in series is 1.534mh

 
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gophert

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This explains something I have been wondering about. I have been thinking my meter has something wrong with it, or bad connector or something? I wound 6 chokes so they all have the save value. If I solder them together is series they add up sorta close depending on how close they are to each other laying on the work bench. With 20 turns of wire on each choke I get .1mh. and 6 in series is .6 mh. If I remove all the wire from each toroid then stack 4 toroids together about 14 turns of wire gives me .45mh.

I checked the value of this transformer on 1 side. Meter takes about 15 seconds to finally decide what the value it. Value slowly climbs then stops. Left to right I get, .240 .330 .440mh. After soldering .240 in series with .330 their values change to .260 & .360 and the total value of the 2 in series is .670mh. .240 .330 .440 in series is 1.534mh
Inductance is way more complicated than capacitance or resistance.
Any overlap in the magnetic fields of inductors will cause additive or subtractive effects. (Wind one counterclockwise and anothe clockwise and compare to overlapping the fields to two similarly wound inductors - especially if bar-shaped cores are placed end to end.
 

ronsimpson

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Meter takes about 15 seconds to finally decide what the value is.
There are several things you are doing that does not add up.
Are you certain you are measuring mH not ohms.
Assuming all turns are on a transformer.
Two windings with 0.5 ohm each. Wire them in series and you get 1.0 ohms. (does not matter if one winding is reversed)
Two windings with 0.5mH each. Wire them in series you get 2mH or near omH depending if they are wired in phase or out of phase.
mH is related to turns squared. so a 2:1 increase in turns gives you a 4:1 increase in inductance.
 

gary350

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There are several things you are doing that does not add up.
Are you certain you are measuring mH not ohms.
Assuming all turns are on a transformer.
Two windings with 0.5 ohm each. Wire them in series and you get 1.0 ohms. (does not matter if one winding is reversed)
Two windings with 0.5mH each. Wire them in series you get 2mH or near omH depending if they are wired in phase or out of phase.
mH is related to turns squared. so a 2:1 increase in turns gives you a 4:1 increase in inductance.
I have 2 chokes in series. Choke on left is 5.5mh + choke on right 9.5mh = 15mh

Same thing with 6 chokes 1mh each in series 1mh x 6 = 6mh

If chokes are close enough together that magnet fields interfere with each other reading is different.

 
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ronsimpson

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If chokes are close enough together that magnet fields interfere with each other reading is different.
If you had a coil like this, two coils will interfere or effect each other.
upload_2018-4-8_12-48-7.jpeg
But coils like this should have little problem with interference.
upload_2018-4-8_12-49-7.jpeg
 

unclejed613

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uncoupled inductors in series will add. so Ltot=L1+L2+... coupled inductors in series and in phase will add, and further, will measure higher than the total of the inductances separately, because of mutual inductance. so, Ltot=L1+L2+Lmut . coupled inductors, if in series but out of phase, will measure less than the total of the separate inductances because of cancellation, so, Ltot=L1+L2-Lmut. it's kind of oversimplified, but that's the basic idea.
 

unclejed613

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and 50/60Hz toroids are still relatively rare
i have 2 or 3 of them from old PA amplifiers. they seem to get used most often in audio equipment, because they don't radiate much in the way of noise and hum. i've also seen CI core transformers used a lot for the same reason, their characteristics are very similar to toroids, but are more easily manufactured using standard transformer construction methods. one of the advantages of ferrite over laminated steel, is that since ferrite is a suspension of iron within an insulator, eddy currents are nearly nonexistent, but laminated steel begins to get lossy as frequency increases because of eddy currents. some ferrites don't get lossy, but actually "disappear" magnetically at high frequencies that's why there are so many grades of ferrites (some of them aren't iron bearing garnet, but actually sintered iron), because different uses require different characteristics.
 

unclejed613

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yes

I do not use "mutual inductance". I use turns squared.
Inductance is turns squared. Does not add up.
A center tapped inductor/transformer: (pin1)--10 turns--(pin2)--10 turns--(pin3)
Measure 1 -2 = 100uH, 2-3 = 100uH, 1-3 = 400uH
that's fine for a center tapped winding, but not if you have two windings connected out of phase. measure 1-2=100uH, 3-4=100uH, 1-3 with 2 connected to 4= less than 100uH (likely close to 0)
 

ronsimpson

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that's fine for a center tapped winding, but not if you have two windings connected out of phase. measure 1-2=100uH, 3-4=100uH, 1-3 with 2 connected to 4= less than 100uH (likely close to 0)
Because +10 turns and -10 turns = 0 turns = almost 0 uH
 

gary350

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Old tube amplifiers have audio output transformers 5000 ohms connected to B+. How is 5K ohms determined?
 
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