50/67 MVA transformer

[bejoyeleengineer]

Hello,
I would like to know why there are two MVA rating given for the transformer i.e, 50 and 67 are given. so what does the 50 indicate for and what about 67 .

 

[kwired]

Just guessing but maybe 50/60 Hz ratings. What does the nameplate say for frequency?

 

[charlie b]

My guess is that this transformer has a set of cooling fans, and that the higher rating applies when the fans are running.

 

[SOG38]

Charlie B is correct.
50 MVA is without fan cooling and 67 MVA is with fan cooling.

 

[zog]

My guess is that this transformer has a set of cooling fans, and that the higher rating applies when the fans are running.

Yep, or could be multiple max rise ratings like 55C/65C

 

[bejoyeleengineer]

thanks for the answer.. 50 MVA means without fan cooling and 67 MVA is with fan cooling..
my friend too gave me the same answer.
Thank you

 

[zog]

thanks for the answer.. 50 MVA means without fan cooling and 67 MVA is with fan cooling..
my friend too gave me the same answer.
Thank you

Maybe, post a photo of the nameplate.

 

[kingpb]

Yep, or could be multiple max rise ratings like 55C/65C

You cannot get that much additional by using the temp rise. 50MVA base @ 55deg C would increase to around 56MVA at 65 deg C rise. approximately 12% increase.

The transformer has to be rated that way as well, i.e. 55/65 deg C. The standard is 65 deg C.

Depending on which design it is, the usual increase is 33% per stage of cooling fans, as would indicate in this situation. Some designs, in the smaller MVA size could be only a 25% increase. it is important to state when you buy them what you expect.

 

[zog]

You cannot get that much additional by using the temp rise. 50MVA base @ 55deg C would increase to around 56MVA at 65 deg C rise. approximately 12% increase.
.

True, excellent point, should have doen the math.