Thanks for your informative reply , I owe you
I am in Greece and waiting for a specialist to come from England,
unfortunatley next week so I had to do something myself ...I
understand the danger and I will follow your instructions step by
step.
Trying to work again today since the voltage -not accurate measures I
took looked "normal" to me, that is instead of 400 V/50 Hz ... 430-460
V due to harmonics I supose.
So after talking to him despit the heating up of the busbars he told
me I can work ... I have a short circuit thyristor more ((
Amperage was not high , according to the instruments steadily at 900 A
- it is designed for 1.300 A, thyristors can take 1800 V - Itav 1400 A
Yes , it is an Inverter ... I take two bus bars from the 6 bridge
rectifier SCR's that is DC ... passing through a secondary protection
coil goes to an Inverter ... 2 pairs of fast , inverter grade
thyristors and they finaly give to the Load high frequency AC at
600-1000 Hz
All started two weeks ago with the secondary coil overheating - just
one widing , it has two , one for each DC phase I supose
I was told that it is short circuit and it went for rewind ... waste
of time and money ...
After having the same overheating at the secondary - protection
coil ... I was told and it was true that I had one water cooled cable
to the load cut ... it was so
After that I was able to work for some melts until the source coming
bus bars started to overheating ... I though it was from bad
thyristors they can;t take too much heat for long , though the system
has everything on it like drops the power from overheating at various
points etc.
Water that cools the cabinet components are highly deionised but I
noticed that in this particular winding , water pressure was low ....
the same cooling line passes from the thyristors so I am thinking of
giving a new one just for the coil and thyristors with enough pressure
to cool them down
Tomorrow I will have one new slow rectifier phase thyristor to test
I am also suspecting short circuit at the load coil ... it is heavily
built up with yokes and supporting woods and isulations between
them ... so I have to exclude any short circuit conditions on the load
side
I exchange two thyristors ... 1-3 and the voltage ... with the
multimeter I did measured it ... seems normal as I told you before .
THanks for the thyristor and triggering instructions I shall try them
also tomorrow !