On an AC motor nameplate, rated load current in amps is at

• A. The motor's shaft horsepower
• B. The current at no load
• C. Nameplate horsepower (HP) with nameplate voltage and frequency
• D. The rated full-load torque

Answer: (C)

The current at which an AC motor’s rating is defined is tied to the motor’s rated electrical and mechanical operating point. Specifically, the full-load (rated load) current is the current the motor will draw when it is delivering its named horsepower at the nameplate voltage and the nameplate frequency. This is the standard operating point used for sizing fuses, breakers, and drives. The nameplate lists the horsepower, voltage, and frequency together, and the full-load current corresponds to that exact combination. Current will vary if you change the voltage, frequency, load, or power factor, so the rating is given for that defined condition. It is not the no-load current (which is much smaller) and not simply the shaft horsepower (which is the mechanical output, not the electrical input).