Need to find current of balanced three phase 15-kw heater(delta connected) when applied to balanced rated voltage of 440/3/60


16.7 amps?

 

Read well what is said here:
http://www.allaboutcircuits.com/vol_2/chpt_10/5.html

So, for delta circuits:

I_line = 1.73 * I_phase

and current required will be:

I_line = P / 1.73 * U_line = 15 [kW] / 1.73 * 0.44 [kV] = 19.70 amps.