Motor condition and performance analyzer

Claim 1

A method of evaluating performance of a polyphase induction motor, the motor including a number of pole pairs, by using data from an uncoupled motor condition test and data acquired during a coupled motor condition test, comprising the steps of: (a) acquiring current data by simultaneously sensing an instantaneous current signal supplied to the motor as a function of time for all three electrical phases of the motor; (b) acquiring voltage data by simultaneously sensing an instantaneous voltage signal supplied to the motor as a function of time for all three electrical phases of the motor; (c) measuring individual motor stator resistances in both the uncoupled condition and the coupled condition; (d) calculating slip from the coupled test data; (e) calculating total real power dissipated by the motor in both the uncoupled condition and the coupled condition; (f) calculating stator I 2 R loss for both the coupled condition and the uncoupled condition, as the individual currents squared multiplied by the respective individual stator resistances corresponding to the particular motor operating condition; (g) estimating loss for the uncoupled condition as the total real power less the stator I 2 R losses; (h) estimating core loss as a percentage of the uncoupled loss; (i) calculating rotor I 2 R loss as the total real power less the stator I 2 R loss less the estimated core loss, multiplied by slip; (j) determining stray losses in accordance with a predetermined value based on a machine rating of the motor; and (k) calculating output power as the total real power less the uncoupled loss less the stator I 2 R loss in the coupled condition less the rotor I 2 R loss in the coupled condition and less the estimated stray losses.

Claim 2

A method of evaluating performance of a polyphase induction motor, the motor including a number of pole pairs, by using data from an uncoupled motor condition test and data acquired during a coupled motor condition test, comprising the steps of: (a) acquiring current data by simultaneously sensing an instantaneous current signal supplied to the motor as a function of time for all three electrical phases of the motor; (b) acquiring voltage data by simultaneously sensing an instantaneous voltage signal supplied to the motor as a function of time for all three electrical phases of the motor; (c) measuring individual motor stator resistances in both the uncoupled condition and the coupled condition; (d) calculating slip from the coupled test data; (e) calculating total real power dissipated by the motor in both the uncoupled condition and the coupled condition; (f) calculating stator I 2 R loss for both the coupled condition and the uncoupled condition, as the individual currents squared multiplied by the respective individual stator resistances corresponding to the particular motor operating condition; (g) estimating loss for the uncoupled condition as the total real power less the stator I 2 R losses; (h) estimating core loss as a percentage of the uncoupled loss; (i) calculating rotor I 2 R loss as the total real power less the stator I 2 R loss less the estimated core loss, multiplied by slip; (j) determining stray losses in accordance with a predetermined value based on a machine rating of the motor; and (k) calculating output power as the total real power less the uncoupled loss less the stator I 2 R loss in the coupled condition less the rotor I 2 R loss in the coupled condition and less the estimated stray losses.