Reliability of transformers

[Fred]

A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?

 

[Spehro Pefhany]

On Mon, 12 Jul 2004 14:08:44 +0100, the renowned "Fred"
<Fred@nospam.com> wrote:

A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?

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
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Woodgate]

I read in sci.electronics.design that Fred <Fred@nospam.com> wrote (in
<40f28d5d$0$7807$db0fefd9@news.zen.co.uk&gt about 'Reliability of
transformers', on Mon, 12 Jul 2004:

A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?



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.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <u775f01pedhsouhc63sgdignae75v909i6@4ax.com&gt
about 'Reliability of transformers', on Mon, 12 Jul 2004:

I don't know how you'd
make a transformer that bad.

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.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Joerg]

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

http://www.analogconsultants.com

 

[legg]

On Mon, 12 Jul 2004 14:08:44 +0100, "Fred" <Fred@nospam.com> wrote:

A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?

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

 

[Mr TUBEAMPS]

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



"Fred" <Fred@nospam.com> wrote in message
news:40f28d5d$0$7807$db0fefd9@news.zen.co.uk...

A transformer winding / supply company has suggested a failure rate of 1%
of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather
poor?

 

[Ian Stirling]

In sci.electronics.design Mr TUBEAMPS <youfinedout@thomuusnonsence> wrote:

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.

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

 

[Tim Shoppa]

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<wf$pB8Ea5s8AFw8K@jmwa.demon.co.uk>...

I read in sci.electronics.design that Fred <Fred@nospam.com> wrote (in
40f28d5d$0$7807$db0fefd9@news.zen.co.uk&gt about 'Reliability of
transformers', on Mon, 12 Jul 2004:
A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?



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.

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.

 

[Tim Shoppa]

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<wf$pB8Ea5s8AFw8K@jmwa.demon.co.uk>...

I read in sci.electronics.design that Fred <Fred@nospam.com> wrote (in
40f28d5d$0$7807$db0fefd9@news.zen.co.uk&gt about 'Reliability of
transformers', on Mon, 12 Jul 2004:
A transformer winding / supply company has suggested a failure rate of 1% of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather poor?



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.

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.

 

[Fred]

"Fred" <Fred@nospam.com> wrote in message
news:40f28d5d$0$7807$db0fefd9@news.zen.co.uk...

A transformer winding / supply company has suggested a failure rate of 1%
of
its products over what I presume to be a year period. The sort of size we
are talking of is around the 100VA.

Can anyone enlighten me if this is typical, just that it seems rather
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.