When using a clamp-on ammeter to read the HP of a 3-phase motor, what does the ammeter read?

A clamp-on ammeter is designed specifically to measure the current flowing through a conductor without the need for direct contact with the electrical circuit. When assessing a 3-phase motor, the clamp-on ammeter provides a reading of the current in amps. This measurement is crucial because it directly reflects the electrical current that is feeding into the motor, which can then be used alongside voltage information to calculate other performance metrics such as horsepower.

Since the primary function of a clamp-on ammeter is to measure current, the reading will solely indicate the amount of current in amps. It does not measure voltage, wattage, or power factor directly—those values require additional instruments or calculations. Therefore, reading only amps is the feature that the clamp-on ammeter offers when measuring motor performance.