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switchboard voltages 270/127V ?

switchboard voltages 270/127V ?

switchboard voltages 270/127V ?

(OP)
Can anybody explain backround for voltages used in a Mexican power plant:

Auxiliary transformer 480/270V Dyn (secondary winding star point solidly grounded)

Switchboard has voltage ratings: 270/127V

I could understand voltages 240/120V as used in US influenced countries but 270/127V? It cannot be printing mistake because 127V is nominal voltage for the country.

att

RE: switchboard voltages 270/127V ?


Is it possible the transformer-secondary and switchboard voltage are 220Y/127 volts?  

460V - 220Y/127V is one standard transformer rating for Latin-American applications.
  

RE: switchboard voltages 270/127V ?

(OP)
Thank you "busbar" for your early reply.

I would assume that the switchboard nominal voltage is 220/127V instead of 270/127V. Then all other busbar voltages applied make sense.
The transformer ratio 480/270V might have misled the drawer? I just wonder why such ratio has originally been selected - to compensate high internal voltage drop? Or is that value wrong as well?

Thanks anyway.

att

RE: switchboard voltages 270/127V ?


North of Mexico, a standard system voltage is 480Y/277 volts, and does not represent a primary-to-secondary transformer rating.  It designated nominal phase-to-phase and phase-to-neutral magnitudes {in this case--likely that of a 4-wire system serving the subject transformer primary.}   

Presumably, the same logic applies in Mexico and “270” is in error.  Another site visit may be in order, for accuracy’s sake.

A “slash” is typically reserved to separate ø-ø and ø-n labeled voltage ratings of a single wye-connected transformer winding.

A “dash” is the conventional means used on a label to separate transformer primary and secondary voltages.  
  

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