What is cable size for a 15 kw 3 phase induction motor 50 meter run for cable 380v?

The formula you are looking for is I = kW x 1000/ 1.73 x E x pf. The formula uses .9 as a power factor. A #1/0 copper conductor will limit the voltage drop to 3% or less when supplying 116 amps for 59 feet on a 415 volt system.