Influence of Single or Multiple Faults Short-circuit, Broken Rotor - - PowerPoint PPT Presentation
Influence of Single or Multiple Faults Short-circuit, Broken Rotor Bar and Eccentricity on the Torque and Rotor Force in Induction Motors V. FIRETEANU, A. I. CONSTANTIN POLITEHNICA University of Bucharest M. POPA University of Oradea,
7.5 kW two-poles squirrel-cage induction motor, 3 x 380 V, 50 Hz supply, 2880 rpm imposed rotor speed Healthy motor Resistivity of all rotor bars, ρ = 0.048 Ωmm2/m Rotor rar breakage simulation Increased resistivity 1.2ρ, 2ρ, 10ρ, 102ρ, 103ρ, 107ρ for FAR1, FAR2, FAR3, FAR4, FAR5, FAR6 faulty states
Coils of the phase U of stator winding. Elementary coil subject of the short- circuit fault, in yellow Circuit model associated with the 3D finite element model Healthy motor state Rshc = 10 MΩ Stator short-circuit simulation Rshc = 90 Ω, 9.0 Ω, 5.0 Ω, 0.9 Ω, for FAS1, FAS2, FAS3, FAS4 faulty states
Healthy motor state Gap1 = Gap2 = 0.50 mm Static rotor eccentricity 20 % Gap1 = 0.40 mm, Gap2 = 0.60 mm Transversal symmetry plane
Gap1 Gap2 Zoom Gap1 Zoom Gap2
(1-1) Signature of SHC fault in the torque time variation Healthy motor HE SHC faulty state Almost the same results for SHC fault as for HE
HF application Mean value HF = 23.12 Nm
(1-2) Signature of BB and ECC faults in the torque time variation BB faulty state ECC faulty state
LF application HF application HF application Mean value LF = 15.67 Nm Mean value HF = 16.07 Nm Mean value HF = 22.89 Nm
(1-3) Comparison HE, SHC, BB and ECC – the first three harmonics
(2-1) Signature of SHC&BB fault in the torque time variation Healthy motor HE SHC&BB faulty state
(2-2) Signature of BB&ECC and ECC&SHC faults in the torque time variation BB&ECC faulty state ECC&SHC faulty state
(2-3) Comparison HE, SHC&BB, BB&ECC and ECC&SHC – the first three harmonics
Comparison SHC, BB, ECC and SHC&BB&ECC – the first three harmonics
(1-1) Signature of SHC fault in the rotor force time variation Healthy motor HE SHC faulty state
LF application Mean value LF = 20.78 N LF application Mean value LF = 70.89 N HF application Mean value HF = 70.41 N
(1-2) Signature of BB and ECC faults in the rotor force time variation BB faulty state ECC faulty state
LF application Mean value LF = 368.4 N LF application Mean value LF = 197.3 N HF application Mean value LF = 191.8 N
(1-3) Comparison HE, SHC, BB and ECC – the first three harmonics
Most important five harmonics
time variation
BB&ECC SHC&BB ECC&SHC
Comparison SHC, BB, ECC and SHC&BB&ECC – the first three harmonics
Only in the cases of broken bar fault, the triple fault and in the two double faults where the broken bar fault is present, the mean values of the motor torque are different from the (HE) case mean value. The harmonic 4 Hz of the motor torque has the highest value of the amplitude in all cases that include the broken bar fault. The stator short-circuit fault does not affect the amplitude of this harmonic, and the eccentricity generates a slight increase of the amplitude of this harmonic. The slotting harmonic 850 Hz of the motor torque is important in the healthy case and in all faulty cases without broken bar.
In contrast to motor torque, the mean values of the rotor unbalanced force present important increases in comparison with the healthy motor state even in case of the stator short- circuit fault. An important increase is generated by the eccentricity fault. However, the most important increase is associated with the broken bar fault. The harmonic of 4 Hz of the rotor force is the most important in the healthy case and in the broken bar case alone, or in association with the stator short-circuit. The most important harmonics of the rotor force generated by the stator short-circuit fault, alone or in association with the eccentricity fault, have the frequencies 200 Hz and 100 Hz. The eccentricity fault alone, in combination with the broken bar fault, or with the other two faults, is reflected in the rotor force harmonics of 60 Hz and 48 Hz.
The investigation methodology based on finite element analysis in time domain offers a deeper research of the electromagnetic phenomena in induction motors, in particular of the motor torque and
the rotor unbalanced force harmonics.