Abstract: There is disclosed an apparatus and method for determining locked rotor test data for three-phase alternating current motor without mechanically coupling the rotor to any instrumentality. The "locked rotor" test is conducted by connecting a source of single-phase alternating current with a variable frequency to the field windings of a three-phase a.c. motor. The frequency of the voltage source is varied from approximately the rated frequency to a lower frequency and the input electrical power and the input voltage are recorded at two or more data points defined by two or more frequencies between the rated frequency and 0. The single-phase input power data and the single-phase input voltage data is then scaled by a scaling factor to convert it to equivalent three-phase locked rotor data. Particularly, the single-phase input power is multiplied by 1.515 to convert it to equivalent three-phase input power, and the single-phase input voltage is multiplied by 0.