marți, 4 august 2020
miercuri, 8 iulie 2020
Stupid oil transformer connection & solution
A wise solution to have cheaper transformers was to connect the bars to the coils by rivets instead of bolts and nuts.
This stupid solution led to a lot of trouble, because in Romania before energizing a transformer we measure the resistances of the coils. If the difference exceeds 2% the transformer is considered bad.
I had many cases, one was for a waste water treatment installation from Hoghiz.
First we changed the transformer with another which was worse than first and then I fixed the problem with my friends from IRUEE Campina. We dismantled the transformer, cut the rivet and we put a bolt with a nut. We checked with the installer that it is OK and we immersed back in oil this transformer. I noticed that the rivets were slightly not at 90 degrees than the bars and the coils.
Probably this was from the riveting tool, probably held by hand, even it was hanged on a rail in the factory. The precision of the riveting is a condition of good contact.
This stupid solution led to a lot of trouble, because in Romania before energizing a transformer we measure the resistances of the coils. If the difference exceeds 2% the transformer is considered bad.
I had many cases, one was for a waste water treatment installation from Hoghiz.
First we changed the transformer with another which was worse than first and then I fixed the problem with my friends from IRUEE Campina. We dismantled the transformer, cut the rivet and we put a bolt with a nut. We checked with the installer that it is OK and we immersed back in oil this transformer. I noticed that the rivets were slightly not at 90 degrees than the bars and the coils.
Probably this was from the riveting tool, probably held by hand, even it was hanged on a rail in the factory. The precision of the riveting is a condition of good contact.
marți, 7 iulie 2020
The nightmare from SIBIU airport with FT clones
They put a first transformer on January 4, 2008 and it was faulty at power-up:
On January 21 2008 I was invited at the Sibiu airport to see the replacement transformer when powered-up. They measured the insulation and the value was at a limit.
Finally the powered the transformer and it exploded.
The closed doors of the transformer compartment opened wide.
Thanks God nobody was outside doors as usual, when you wait for power and put the ear on the door to hear when power is on...
Both transformers are FT clones made FOR Schneider by TMC...
Both were kept outside.
Both were are old.
Most of them were stored outside with plastic foil when ordered on stock.
These two were kept outside a long time.
The solution was the 3rd transformer, original France Transfo. This solved the problem.
Finally the powered the transformer and it exploded.
The closed doors of the transformer compartment opened wide.
Thanks God nobody was outside doors as usual, when you wait for power and put the ear on the door to hear when power is on...
Both transformers are FT clones made FOR Schneider by TMC...
Both were kept outside.
Both were are old.
Most of them were stored outside with plastic foil when ordered on stock.
These two were kept outside a long time.
The solution was the 3rd transformer, original France Transfo. This solved the problem.
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