CLAIMS [1] An electric motor diagnosis device comprising:
a load torque calculation unit for calculating load torque of an electric motor, using voltage and current sampled and inputted from a main circuit to which the electric motor is connected;
a negative-phase-sequence admittance characteristics storage unit storing load torque/negative-phase-sequence admittance characteristics obtained in advance
when the electric motor is normal;
a negative-phase-sequence admittance calculation unit for calculating a negative-phase-sequence admittance from the load torque calculated by the load torque calculation unit, using the load torque/negative-phase-sequence admittance characteristics stored in the negative-phase-sequence admittance characteristics storage unit;
a winding short-circuit evaluation value calculation unit for calculating a winding short-circuit evaluation value on the basis of the negative-phase-sequence admittance calculated by the negative-phase-sequence admittance calculation unit, negative-phase-sequence current calculated from input current, and negative-phase-sequence voltage calculated from input voltage; and
a winding short-circuit determination unit for determining that winding short-circuit has occurred, when the

winding short-circuit evaluation value calculated by the winding short-circuit evaluation value calculation unit is equal to or greater than a threshold value.
[2] The electric motor diagnosis device according to claim 1, further comprising a voltage unbalance rate determination unit for allowing execution of the calculation by the load torque calculation unit when a maximum difference between each inputted interphase voltage and average voltage thereamong is 5% or lower.