Transformer Laminates

In another group I talked about going to a local transformer shop buying cheap copper wire and getting free mica tape and laminates. But that was in the early 80's. Laminates were large, 4 inch by almost 3 feet.

greg

I keep pushing these things around, always getting in the way.

greg

Lamination materials are inexpensive only when purchased in volume, justifying paperwork, handling and shipping costs. This is true with most materials and should be no surprise.

Transformer manufacturers will typically purchase grades of stock in large rolls, by the skid, truck or box-car load, with inventory and stamping/slitting tooling costs being averaged over long-term use. As the tools age, productivity will reduce and the quality of their output may degrade. Obtaining flat, burr-free stampings from low-volume methods is not an elementary exercise.

You might obtain unvarnished laminated stock from distribution or surplus outlets in sample quantities; they are sold by weight.

It used to be the rule that heavy articles could be competitive when produced locally, resulting in local sources for 60Hz magnetics and materials. This is no longer true. What 'should be' may be irrelevant.

Frankly, it's a lot cheaper to 'iterate' on paper first, or through the use of various public domain spreadsheets or software. The efficiency of the part will benefit most from this exercise and your understanding of the practical limitations of the materials and methods involved.

Evaluation samples of preassembled magnetics, to your design specification, can be requested in the unvarnished state from most custom vendors, if you want to fiddle with similar iterations using those materials.

This skill is not particularly highly valued in the industry, at lower power levels.

RL

Try Temple Steel, I recently purchased approx $100 of laminations as a small qty. They were very helpful.

Cheers

how much was the small quantity? Hopefully large enough to make a few decent sized transformers(25W or more). Would you care to tell me which ones you got and about how many?

Thanks

These were for a 300w transformer

E137H/0136 1 String (28lbs) of M6 grade 29awg was 1.79/lb , I believe it was $100 total with shipping. Got 4 or 5 transformers out of it. The thinner laminations were 1.3/lb and 1.0/lb

The string size depends on the lamination size, So I picked the laminations by a minimum string size. The sales rep was very helpful. Email me if you run into a non helpful rep, and I'll give you the rep I had dealt with. You can try other vendors, they still may be trying to recover commodity prices for the steel they purchased when it was high. Also, I would think that the smaller EI cores would have larger string sizes. Some strings were 500lbs. The 137H was one of the popular laminations.

Hope that helps.

These were for a 300w transformer

E137H/0136 1 String (28lbs) of M6 grade 29awg was 1.79/lb , I believe it was $100 total with shipping. Got 4 or 5 transformers out of it. The thinner laminations were 1.3/lb and 1.0/lb

The string size depends on the lamination size, So I picked the laminations by a minimum string size. The sales rep was very helpful. Email me if you run into a non helpful rep, and I'll give you the rep I had dealt with. You can try other vendors, they still may be trying to recover commodity prices for the steel they purchased when it was high. Also, I would think that the smaller EI cores would have larger string sizes. Some strings were 500lbs. The 137H was one of the popular laminations.

Hope that helps.

You are far better off buying a transformer that is of the frequency and VA rating that your target application is, and remove the transformer windings, and then apply your own.

THAT is, by far, the cheaper method, as without compressive lamination bonding, you are going to have efficiency variances.

By using an existing transformer, you are using an already matched set of plates, and typically get a bobbin in the deal for free.

If you unwind it carefully, you may find one winding that matches your target. Not always, and winding your specific need is best, of course, but it does happen at times.

Thanks Martin, it sure does. I don't live too far away from temple and sometimes travel through it so it might be a good deal for me. Do you mind letting me know how your transformers went? The total cost per transformer and approximately how well it worked? I'm mainly interested in playing around with some transformers and potentially using a few for some vacuum tube projects. I actually don't care too much about optimizing efficiency but buying guitar amplifier transformers is extremely expensive and this seems to be the only source I can find of transformers for the voltages I need.

You can buy standard size E - I laminations ( google it ) but I expect MOQs are high. Toroids are usually wound in large quantities to order or fabricated themselves by large transformer makers.

Graham

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Chat to Pat Turner in rec.audio.tubes. He knows a lot about winding output transformers especially.

Graham

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For mains transformers, some distributors such as Farnell and RS Components used to make 'kits' with pre-wound primaries so you could wind 'odd-ball' output voltages.

Graham

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I modify standard toroid power transformers for funny high current low voltage outputs. Low turns per volt, easy to insulate and mount.

All the best Ian Macmillan

Things did work out well, after 3 iterations. You should also look into toroids.com

Smallest is 60w but you can wind the secondaries to your liking. And at $30 each its not too bad.

BTW, FormCo Has bobbins and brackets, in small qtys. Ask for a cataloge.

Cheers

Thanks, I appreciate it.