I have a 4000V, 280 FLA induction motor service for reciprocating compressor. Normally, motor running at 240 A (100% compressor), the highest winding temperature is 120degC, but now we found the operating current increasing up to 268 A (we still investigate why. With 268A, the highest winding temperature become 130degC.

Is that normal 28A current increasing (268-240 = 28A) can cause increasing 10degC temp. ?
Is there any equation that state the correlation between current and temperature ??