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Dagnall PCB Mount Transformers

Hi

Has anyone else had problems using Dagnall or Clairtronic (same company) PCB mount transformers.

I am getting very frustrated replacing burnt out transformers. Firstly the transformers bulge and the plastic case darkens and run noticeably hot. Then, I would assume windings start to short and any fuse supplying the transformer blow. The rate of failure is currently running at around 12 -

15% out of the 500 or so after 18months in use.

The transformers we use are the 14VA types which are split primary and secondary, we are running the transformer at around a 50% load factor with occasional peaks for about 10 secs to about 80% rating. When there is a 'burn-out' the blackening only appears in one of the four bobbin segments, sometimes one of the primary and sometimes one of the secondary windings. This seems to point that it is not overload problem as I would expect to see both the primary or secondary windings 'burn' together but so far this has never been the case.

We have approached MGC Electronics who make these transformers in Malta who were of little help and are still holding about 100 of our transformers for 'testing'. We have heard nothing from them for 6 months or more now. We have also approached the original suppliers, Farnell, who say they have had no other complaints and can only follow the findings of the manufacturer.

Our solution has been to swap to a similar unit made by Block from Germany, of exactly the same VA rating, and so far have swapped around 100 over the last year with absolutely no failures whatsoever.

One of my biggest ever mistakes, the day I chose to use Dagnall for our design.

BE WARNED!!!!

Paul Bannister Data Solutions

Reply to
pbanny
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One of the failure modes for a transformer is to get a short between adjacent wires. That makes a shorted loop. You get one turns worth of voltage across the loop which usually means lots of current and hence lots of heat. Soon the insulation on adjacent turns breaks down and it just gets worse... (Positive feedback.)

Are you running any voltage spikes that might breakdown the insulation? How hot are they normally running?

--
These are my opinions, not necessarily my employer's.  I hate spam.
Reply to
Hal Murray

pbanny MULTI-POSTED:

Don't do this:

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If you are going to post to MULTIPLE groups, do this instead:
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*-*-*-marked-as-Read-in-ALL-*-groups+Newsgroups.line

Reply to
JeffM

Can't see any multi-posting on my news server, where are the other posts?

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

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Reply to
Prepair Ltd

Hi Hal

The transformers are currently run with both primaries in parrallel, i.e.

115v mode, and run from a 110volt UPS system to compensate in case of power fluctuations.

Good transformers run quite cool at around 10C above ambient, the ambient has been monitored and does not exceed 35C even on hot days last summer.

I have recently been talking with another company who is also having problems with Dagnall transformers and from this conversation it seems that Farnell are having complaints from many others but will not let on how bad the problem really is. I was beginning to think we were the only people using this product and having problems, but now a little more releaved that it probably is not our circuit design at fault as this other company's product is many years old and it is only since swapping to use Dagnall transformers that their problems started.

Paul Bannister Data Solutions

01384 888600
Reply to
pbanny

Perhaps worth a word to the standards bodies whose marks these parts carry..?

Reply to
Mike Harrison

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