A Nonintrusive and In-Service Motor Efficiency Estimation Method using Air-Gap Torque with Considerations of Condition Monitoring

Verification of the modified AGT method applied to determining efficiency of squirrel-cage induction motor

“…1), which conforms with the analysis in [7][8][9]. Dependences (9) and (10) for three-wire, sinusoidal, and symmetrical power supply system of a three-phase motor produce the following expression of momentary electromagnetic torque t agt :…”

“…Friction and windage losses ΔP m are assumed to equal 1.2% P 2 . These authors have verified the equivalent model of motor losses adopted in [7][8][9] by comparing the actual motor efficiency its estimated value. The results indicate great estimation errors, therefore, the simplifications accepted in [7][8][9] cannot be applied to practical assessments of in-service motor efficiency.…”

“…Available literature ignores losses ΔP Fes in the stator's core and ΔP Fer in the rotor's core to compute P 2 [7][8][9]. Stray load losses ΔP dodr are assumed to comply with IEEE 112 [10].…”

“…T ag is a result of momentary value of t ag defined as a module of the product of momentary values of stator fluxes vector ψ s times momentary values of stator currents vector i s [7][8][9]:…”

Investigation of reductions in motor efficiency caused by stator faults when operated from an inverter drive

“…Efficiency is reduced by approximately 0.2% from the faulty motor compared to baseline. The air gap torque ag T calculation used is given below [14]:…”