I've been in contact with the transformer manufacturer and so far they sound very 
helpful.

They say I'm using it correctly, ie. it's appropriate to wire the two primaries in 
parallel. They discussed core losses and copper losses, and did a quick calculation 
on temperature rise that agrees with the temperatures I am observing. They point 
out that this temperature is well within the specifications (insulation rating of 155 
deg C) BUT they say they would like to see it lower than this (so would I !!!). Further 
to this they will take a transformer from their warehouse and do some testing at 
50Hz to confirm, and look at what changes if any can be made to improve 
performance under these conditions.

Thanks for all the responses, I'll report back when I know some more!

-- 
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: 027 433 4069
eMail:  brent.brown@clear.net.nz


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