Reliability of transformers

That is absolutely insanely horribly bad. Ordinary mains-frequency low-voltage power transformers used well within their ratings will outlast most any other part in your design. It's also hard to kill them even by moderately abusing them (cook them at extremely high temperature or arcing them will do them in). I don't know how you'd make a transformer that bad.

Of course if you're talking about a cheaply made 10kV transformer run at 125°C, that's maybe a horse of a different color.

Best regards, Spehro Pefhany

I read in sci.electronics.design that Fred wrote (in ) about 'Reliability of transformers', on Mon, 12 Jul 2004:

That's a spec written by a marketroid. 1% over 10 years might be more realistic, but I'd be disappointed. I'd expect a World War 2 100 VA transformer kept in a benign environment to still work.

I read in sci.electronics.design that Spehro Pefhany wrote (in ) about 'Reliability of transformers', on Mon, 12 Jul 2004:

Battery-charger transformers that are not varnish-impregnated fail after a few years, but that's probably intentional, and is due to the bad environments (especially very high humidity) they experience. A varnished one will last forever.

Hi Fred,

To add to Spehro's and John's concerns: Just imagine if every part in your design had a "reliability level" that would cause 1% to fail in a year? How many systems would still work after one year? How soon would the warranty overhead on this design eat up a corporation's assets?

Regards, Joerg

Perhaps it's your presumption of 'a year period' that is in error. Obviously you'd need to find out for sure, however.....

Early mortality prior to shipping, shipping damage, and 'returns for other reasons' can sometimes all be lumped into the same 'total defects' category. This does not provide any meaningful representation of device reliability or failure rate, nor does it give anyone a clue as to possible methods of avoidance/improvement without more serious analysis.

But it's what a bean counter wants, and he has every right to it.

RL

some power transformers have a thermal fuse hidden under the primery winding tape, when thay blow, winding is open. the fix is to peal back the tape to fined it, and then brige it with wire and use a external fuse. use silicon or hot glue to reseel.

john

of

poor?

I'd replace thermal fuse, and improve ventilation, if possible.

Most 1940's era transformers have had an insulation failure since then. Not all... and a lot of insulation failures go undetected.

A good fraction of transformer failures are due to the stuff it supplying failing catastrophically, taking out the transformer with it. Rectifier and filter capacitor failure does this. I wouldn't attribute this as a failure due to the transformer, but maybe the manufacturer does in counting totals. The "1% over maybe a year" is not a real spec in any event.

Tim.

Most 1940's era transformers have had an insulation failure since then. Not all... and a lot of insulation failures go undetected.

A good fraction of transformer failures are due to the stuff it supplying failing catastrophically, taking out the transformer with it. Rectifier and filter capacitor failure does this. I wouldn't attribute this as a failure due to the transformer, but maybe the manufacturer does in counting totals. The "1% over maybe a year" is not a real spec in any event.

Tim.

of

poor?

Just found out the 1% is the failure rate after 1st test. Had me worried for a moment.

Thanks for all the replies. Will keep you posted on any further figure.

I also thought it was worryingly poor. My experience is they tend to be one of the last things to fail.