torroidal transformer vendor

Thanks! We'll zap them our spec.

John

Thanks; we'll try them. And yeah, we had to go to TT superslow fuzes for this one. We also used the inrush limiter thingies, the ones that look like black disc caps. Primary resistance runs about 5 ohms per

John

Thanks. We'll add them to the bid list.

I hate magnetics.

John

I've used their standard products in that range:

You know this, but toroidal power xfmrs can have a nasty turn-on current surge.

Best regards, Spehro Pefhany

I do like transmission-line transformers wound with micro-coax. We just did a small 1:1 that puts a 60 volt pulse into 50 ohms with rise/fall around 2 ns. That's fun.

John

You'll get farther with your searching if you spell it 'toroid', with one R.

If you're serious about wanting production pricing, I suggest you contact Bridgeport/Alphacore/Tortran (all the same company, really)

Piece prices from them are often much lower than the competition. Quality is good.

If you're concerned about turn-on surges, look for an article about new toroid transformers designed to limit power-on surge:

Paul Mathews

No problem photocopying the page out of the EEM and giving it to purchasing. It must have 200 vendors.

Thanks.

As I told Speff, we have NTC surge limiters and TT fuzes, so that seems to be under control.

John

Sure. At 10% overvoltage.

The guy who spec'd and tested the trannies no longer works for me; one day he walked into my office, said "it's time to move on" and left. Interestingly, he used to work for Signal Transformer. I guess he didn't test it for saturation. All you really need to do is overvoltage it at 60 Hz, find the knee, and multiply by 5/6.

Our customer (it's an OEM product) took our gadget to a major test lab for the full CE suite, including specific transformer tests. Their test report *justifies* why it was not necessary to actually test at

John

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

Hey John, Rayco Electronics, lightning free prototypes, great production prices, works for me.

Of course we did.

We're using TT fuses.

The CE test involves loading the transformer secondary to just below the fuse blow point and then waiting to see how hot the transformer gets; that is a lot nastier than a clean short. And this box has no fans. So we have to use the smallest possible fuse rating, or we pay for it in transformer iron. So between the powerup surges (core+caps) and the fact that this is a pulsed power amp, things get interesting.

I think what happened was that the original transformer design was OK but a bit too big. Somebody at the transformer company (another somebody "no longer here") scrunched the design program and wound up with a transformer that was smaller but had no saturation margin.

John

Hello John,

I had lots of good experience with Ulveco. There have been mergers et cetera and I believe in the US it might now be:

Regards, Joerg

Hello John,

Power transformers can be kind of boring. But I love ferrite stuff. You can do cool things with those.

Regards, Joerg

Your own spotty behind was covered by the mention of 50Hz, somewhere in the spec?

Don't you test these things?

RL

Toroid International.

The MD owns the company and is highly knowledgable and most helpful. Their prices are good too as they manufacture in asia.

Graham

You didn't put 50Hz on the spec ?

Sounds like a transformer supplier who doesn't understand that there's a whole world out there.

Oh - and if you're selling in Europe don't forget to use IEC spec fuses not UL. The blowing characteristics are very different too.

I've *never* had to use a TT fuse. Ts normally work just fine for me and I regularly use toroids.

Fuse only needs to blow when ( typically ) you short out any one of the secondary side reservoir caps btw.

Graham

My customer wanted it CE tested, so we told them to do it themselves. They took it to ITS, a big US test lab, and that's what they did. I'll try to find out which spec they were working to.

But the transformer smoke test really only forced us to use the TT fuses and the inrush limiters... it didn't really dominate the transformer design, which was more of an available-space problem.

John

There used to be a UK contributor to sed (Mark Daniels) who owns his own transformer company. I bought some custom transformers from him a couple of years ago. They were ok.

Jem Electronics, 173a High Street, Clay Cross, Chesterfield, S45 9DZ, 0870 787 1708.

BTW: What's the rough spec? Size? PCB-mount or flying leads? Secondary Volts/Amps?

Note that Soddes Law says that urgently trying to get a new transformer designed and wound, by an unknown supplier, in a different country, could bite you in the bum.

I'm still looking for a better reference, but I've been led to believe (by a visiting rep) that this toroidal transformer technology, touted for its EMI filtering benefits, also has improved inrush characteristics:

Having just re-read the article, I find no mention there, so apologize for possibly sending anyone on a goose chase. However, the EMI aspects are interesting in their own right. Paul Mathews

I read in sci.electronics.design that John Larkin wrote (in ) about 'torroidal transformer vendor', on Tue, 8 Feb 2005:

Which standard are you applying? It sounds to me that you may not be applying the correct one.