Analysis of the Evolution of the Stator Short-circuit and Rotor - PowerPoint PPT Presentation

Analysis of the Evolution of the Stator Short-circuit and Rotor Bar Breakage Faults in a Squirrel- cage Induction Motor V. FIRETEANU and A. I. CONSTANTIN – POLITEHNICA University of Bucharest Vincent LECONTE and Patrick LOMBARD – ALTAIR Engineering France

Summary Introduction  Dedicated finite element model of  a squirrel-cage induction motor Stator short-circuit fault signatures.  Early detection of the short-circuit fault Rotor bar breakage signatures.  Early detection of the bar breakage through  harmonics of the stator currents and of the magnetic field Conclusions 

3D finite element model of a squirrel-cage IM. Rotor bar breakage simulation Rotor speed = 2880 rpm Healthy motor: resistivity of all rotor bars, ρ = 0.048 Ω mm 2 /m 7.5 kW two-poles squirrel-cage IM 3 x 380 V, 50 Hz supplied Bar breakage simulation: increased resistivity 1.2 ρ , 2 ρ , 10 ρ , 10 2 ρ , 10 3 ρ , 10 7 ρ , for FAR1, FAR2, FAR3, FAR4, FAR5, FAR6

Stator short-circuit fault simulation Rotor speed = 3000 rpm Circuit model associated to the 3D finite element model of an IM Rshc Healthy motor: Rshc = 10 M Ω Short-circuit simulation: Coils of the phase U of stator winding. Rshc = 90 Ω , 9.0 Ω , 5.0 Ω , 0.9 Ω , for Elementary coil subject of the short- FAS1, FAS2, FAS3, FAS4 circuit fault, in yellow

Stator short-circuit fault signatures (1) Signature in the stator phase U current FAS4 faulty state Healthy motor

Stator short-circuit fault signatures (2-1) Signature in the magnetic field Bx[M] outside the motor FAS4 faulty state Healthy motor

Stator short-circuit fault signatures (2-2) Signature in the magnetic field Bz[P] + Bz[Q] outside the motor FAS4 faulty state Healthy motor

Broken rotor bar fault signatures (1) Signature in the stator phase U current FAR6 faulty state Healthy motor

Broken rotor bar fault signatures (2) Signature in the magnetic field Bz[P] + Bz[Q] outside the motor Healthy motor FAR6 faulty state

Early detection of the stator short-circuit and a rotor bar breakage faults EFFICIENCY of FAULT DETECTION criterion definition : ratio between the amplitude of a given harmonic for faulty state and for healthy state Fault detection through the harmonics of the stator currents Fault detection through the harmonics of local values of different components of the magnetic flux density outside the motor

Early detection of the stator short-circuit fault

Efficiency of the short-circuit detection through harmonics of the I U stator current f [Hz] FAS1 FAS2 FAS3 FAS4 150 1.055 1.821 2.340 4.320 950 0.976 0.985 1.053 1.596 1050 0.723 4.675 8.113 27.74

Efficiency of the short-circuit detection through harmonics of the I U stator current

Efficiency of the short-circuit detection through harmonics of Bx[M] f [Hz] FAS1 FAS2 FAS3 FAS4 950 1.009 1.081 1.194 2.466 1050 1.013 1.117 1.217 1.800

Efficiency of the short-circuit detection through harmonics of Bx[M]

Efficiency of the short-circuit detection through harmonics of Bx[M] – Bx[N] f [Hz] FAS1 FAS2 FAS3 FAS4 750 1.026 1.173 1.331 3.023 1350 1.015 1.249 1.608 6.524 1950 1.016 1.298 1.766 3.777

Efficiency of the short-circuit detection through harmonics of Bx[M] – Bx[N]

Efficiency of the short-circuit detection through harmonics of Bz[P] + Bz[Q] f [Hz] FAS1 FAS2 FAS3 FAS4 1250 1.320 4.471 6.235 20.32 1950 1.042 3.660 11.37 41.76

Efficiency of the short-circuit detection through harmonics of Bz[P] + Bz[Q]

Most appropriate quantity & harmonic to supervise the stator short-circuit fault evolution I U current Bx[M] Bx[M] – Bx[N] Bz[P] + Bz[Q]

Early detection of a rotor bar breakage fault

Efficiency of the rotor bar breakage detection through harmonics of the I U stator current FAR1 FAR2 FAR3 FAR6 f [Hz] 46 3.27 8.29 14.09 34.52 225 1.056 1.174 1.673 3.478

Efficiency of the rotor bar breakage detection through harmonics of the I U stator current

Efficiency of the rotor bar breakage detection through harmonics of Bx[M] f [Hz] FAR1 FAR2 FAR3 FAR4 FAR5 FAR6 2 1.145 1.438 4.542 21.17 68.92 115.6 2 Hz is the frequency of rotor currents corresponding to the motor speed 2880 rpm

Efficiency of the rotor bar breakage detection through harmonics of Bx[M]

Efficiency of the rotor bar breakage detection through harmonics of Bx[M]-Bx[N] f [Hz] FAR1 FAR2 FAR3 FAR4 FAR5 FAR6 2 4.657 15.72 52.96 268.2 890.7 1513 1.285 4.250 10.68 47.15 100 - -

Efficiency of the rotor bar breakage detection through harmonics of Bx[M]-Bx[N]

Efficiency of the rotor bar breakage detection through harmonics of Bx[P]-Bx[Q] f [Hz] FAR1 FAR2 FAR4 FAR6 100 1.285 3.266 7.640 33.00

Efficiency of the rotor bar breakage detection through harmonics of Bx[P]-Bx[Q]

Efficiency of the rotor bar breakage detection through harmonics of Bz[P] f [Hz] FAR1 FAR2 FAR3 FAR4 FAR5 FAR6 2 1.361 2.627 9.128 44.14 144.9 244.6 1.057 1.587 3.098 13.63 100 - -

Efficiency of the rotor bar breakage detection through harmonics of Bz[P]

Efficiency of the rotor bar breakage detection through harmonics of Bz[P] +Bz[Q] f [Hz] FAR1 FAR2 FAR3 FAR4 FAR5 FAR6 2 6.557 21.76 74.11 369.6 1225 2073 1.532 4.912 12.31 53.96 100 - -

Efficiency of the rotor bar breakage detection through harmonics of Bz[P] +Bz[Q]

Most appropriate quantity & harmonic to supervise the rotor bar breakage evolution Bx[M] I U current Bx[M] – Bx[N] Bx[P] – Bx[Q] Bz[P] Bz[P] + Bz[Q]

Conclusions The monitoring of the evolution of the short-circuit faults in the IM stator winding through the stator currents and/or the magnetic field in the motor proximity represent an efficient solution. The harmonic 1050 Hz of the stator current offer high values of the efficiency in early detection of the stator short-circuit fault. The short-circuit fault investigation based on the axial component of the magnetic field in the overhang region of the stator winding offers the best result with the 1250 Hz harmonic. The monitoring of the broken bar faults can be done through the following harmonics of the stator current and of the magnetic field: a) the 46 Hz harmonic of the current, with the efficiency of fault detection 35; b) the 225 Hz harmonic of the current, with the efficiency of fault detection 4; c) the 2 Hz harmonic of the magnetic field Bz[P] + Bz[Q], with a very high efficiency of fault detection 2100; d) the 100 Hz harmonic of the magnetic field Bz[P] + Bz[Q], with the efficiency 54.

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