I was told currents in Y phase will be more when compared with R & B Phases. can anyone explain theory behind this?

Problem: Running load of motor 252A, cable length: 200mtrs.

Satish,

What are the currents?

Alan

what should be current in Y phase if R and B phase currents are 252 A?

The same, what is the current reading of Y phase? we cannot asses the situation without this value.

Mr. Norman: Value is 257A

A three phase motor can be connected with the windings in star or in delta connection. Star and delta are often abbreviated as Y and D. Is it that somebody has told you that a motor connected in Y will have higher current? Possibly they used the letter "Y" when talking about star connection rather than referring to Yellow phase.

A different possibility - are the controls and contactor coils for this motor connected to Y phase, hence you will measure slightly higher current in the yellow supply lead?

This could be a supply transformer issue. The voltage difference falls within 3% of the voltage nominal and is normal.

I see nothing the value which you should be worried about. You can have your supplier do a tap change to satisfy you.

Kind Regards

Such a small difference between phase currents can be caused by a variety of factors.

One of the most likely causes could be that the supply is via three single-core cables, that are not laid absolutely symmetrically, and with no regular transpositions along the way.

Another cause could be measuring error, in particular if it is difficult to place some clamp-on tong tester so the readings will not be affected by stray magnetic fields from the other two cores.

Such a small difference will rarely be something to be concerned about.