Read and record the motors nameplate amperage for the voltage being used.

Insert the recorded values in the following formula and solve.

x 100


LLA = Loaded Line Amps NLA = No Load Line Amps (Motor disconnected from load) NPA = Nameplate Amperage (For operating voltage)

Please note: This procedure will generally yield reasonably accurate results when motor load is in the 40 to 100% range and deteriorating results at loads below 40%.


• A 20 HP motor driving a pump is operating on 460 volts and has a loaded line amperage of 16.5.

• When the coupling is disconnected and the motor operated at no load the amperage is 9.3.

• The motor nameplate amperage for 460 volts is 24.0.

Approximate load on motor = 100 HP x 0.56 = 56 HP

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