What is the full load amperage of a 500 HP motor at 380 volts?

1HP =746 watts power(watts)= current times voltage ... 746x500=373000. 373000/380= 981.58 so 981.58 amps

You have not supplies sufficient information to answer the question.

The load current depends upon the type of motor(d.c./a.c./ single-phase/ three-phase), and the efficiencyof the motor. Before you can calculate the current, you need to determine the input power to the machine, which is always greater than its output power, which you have described as being 500 hp. Once you have determined the input power, and the type of motor, only then can you can calculate the load current