Blodt 3논문

1. 1
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
• Load torque under mechanical fault
• Rotor speed
• Rotor angle
+ H.O.T
In steady state
->Torque oscillation 으로 일어나는 항
1.[Mechanical Load Fault Detection in Induction Motors by Stator Current Time-Frequency
Analysis],2006,TIA, 270인용
Blodt (2006,2008,2009) 논문 3개

2. 2
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
• Rotor MMF wave
• Stator MMF wave -> no direct influence of torque oscillation
+ H.O.T
• Airgap Magnetic Flux Density = MMF Sum X Permeance
• Airgap Magnetic Flux = integration of Airgap Flux Density
• Stator voltage equation Time-varying phase
질문 : PMSM에서는
어떻게 되나요?
1.[Mechanical Load Fault Detection in Induction Motors by Stator Current Time-Frequency
Analysis],2006,TIA, 270인용

3. 3
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
• PSD based on discrete FT
• Instantaneous Frequency (IF)
• Wigner Distribution (WD) : FT of a kernel Kx(τ,t) with respect to the delay variable τ . The kernel is similar to an autocorrelation function.
• Spectrogram : time-frequency distribution based on the FT of the product of a sliding window h(t) with the signal
1.[Mechanical Load Fault Detection in Induction Motors by Stator Current Time-Frequency
Analysis],2006,TIA, 270인용

4. 4
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
2.[Models for Bearing Damage Detection in Induction Motors Using Stator Current
Monitoring],2008, TIE, 536인용 ,
• Airgap length variation
• Airgap permeance
• Airgap Magnetic Flux Density = MMF Sum X Permeance
Fault-related sine waves(k>1)
• Airgap Magnetic Flux ->has additional term as Airgap Magnetic Flux Density
I. Radial Rotor Movement (Rotor Eccentricity)
본인의 2006 논문에다 베어링 고장을 2가지 관점(Rotor
Eccentricity, Load Torque Oscillation)으로 연관시킴

5. 5
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
• Stator voltage equation ->has additional term as Airgap Magnetic Flux
radial rotor movement due to the bearing fault results in
additional frequencies in the stator current
I. Radial Rotor Movement (Rotor Eccentricity)
2.[Models for Bearing Damage Detection in Induction Motors Using Stator Current
Monitoring],2008, TIE, 536인용 ,

6. 6
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
• Load Torque
II. LoadTorque
Variations
each time a ball passes in a hole, mechanical resistance will appear
when the ball tries to leave the hole. The consequence is a small
increase of the load torque; The bearing fault-related torque variations
appear at the previously mentioned characteristic vibration frequencies
fc
• Rotor speed
• Rotor angle
• Rotor MMF
• Airgap Magnetic Flux Density
• Stator current I1 > I2
2.[Models for Bearing Damage Detection in Induction Motors Using Stator Current
Monitoring],2008, TIE, 536인용 ,

7. 7
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
3. [Distinguishing Load Torque Oscillations and Eccentricity Faults in Induction Motors Using
Stator Current Wigner Distributions],2009,TIA, 144인용
Mechanical Faults
Load Torque Oscillations
Eccentricity Faults
Above both
[In general, eccentricity is a sign for a mechanical problem
within the electric motor, whereas load torque oscillations
point to a fault that is located outside of the motor.]
이전 논문들에서 나왔던 Eccentricity, Load Torque Oscillation을
좀더 심도있게 분석 , PM AM 을 WD 로 구별하는 방법씀
2006논문의 결과와 동일, Phase Modulation
II. Air gap Eccentricity (AM)
• Dynamic Eccentricity
• Airgap permeance
I. Load Torque Oscillations(PM)

8. 8
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
3. [Distinguishing Load Torque Oscillations and Eccentricity Faults in Induction Motors Using
Stator Current Wigner Distributions],2009,TIA, 144인용
• Airgap Magnetic Flux Density = MMF Sum X Permeance
• Stator current
MMF Sum
Airgap Magnetic Flux Density
Amplitude Modulation

9. 기계적 고장에 의한 Stator Current Modulation 에 관한 조사
9
III. Torque Oscillations Resulting From Eccentricity-> Eccentricity 있으면 결국 AM + PM 발생함을 설명
a nonzero torque is only produced if the pole-pair
numbers of the interacting waves are equal + Time-
varying torque is produced if the waves have equal
pole-pair numbers and different pulsations.
torque
realistic eccentricity faults in practice include a
mixture of static and dynamic eccentricity
simultaneously, which is termed mixed eccentricity.
In this case, additional p ± 1 pole-pair waves with
pulsations ωs and ωs ± ωr are present.
Oscillating torque
3. [Distinguishing Load Torque Oscillations and Eccentricity Faults in Induction Motors Using
Stator Current Wigner Distributions],2009,TIA, 144인용

10. 10
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
IV. WD 로 PM(Load Torque Oscillations )과 AM (Eccentricity, 사실 AM+PM)을 구별
• WD of PM
• WD of AM
lower sideband has the opposite sign to the
upper sideband for a given point in time
upper and lower sideband
oscillations have the same
amplitudes for a given point in
time
PM AM
합성된신호 실제신호
PM(Load Torque Oscillations )
AM+PM
(Eccentricity)
3. [Distinguishing Load Torque Oscillations and Eccentricity Faults in Induction Motors Using
Stator Current Wigner Distributions],2009,TIA, 144인용

11. 기계적 고장에 의한 Stator Current Modulation 에 관한 조사
4.[Hilbert versus Concordia transform for three-phase machine stator current time-frequency
monitoring], Baptiste Trajin,2009,MSSP, 65인용
핵심 내용 : 앞선 Blodt et.al 논문에서는 eccentricity와 load torque oscillations와 같은 Mechanical
faults 이 각각 AM and PM of stator current를 발생시킨다고 증명함. AM, PM 분석 위해 instantaneous
amplitude (IA)와 instantaneous phase (IP)의 엄밀한 정의가 필요. 이를 위해 Complex signal이 필요. 전
통적으로 이를 위해 Hilbert Transform(HT)이 많이 쓰임. Bedrosian 조건에서는 분리된 modulation이 가
능했지만 일부 Mechanical faults는 이 조건을 위반함(Fast modulation일때). 그리하여 HT대신
Concordia transform (CT)를 이용하여 Complex vector 생성하여 Bedrosian 조건을 어기는 경우에 CT의
WD를 사용하여 Mechanical faults를 Fast/Slow modulation 모두에서 강건하게 진단하는게 목표.
• Stator current (3상)
Healthy
Dynamic eccentricity
pure Load torque oscillations
Dynamic eccentricity+Load torque oscillations
AM
PM
PM+AM

12. 4.[Hilbert versus Concordia transform for three-phase machine stator current time-frequency
monitoring], Baptiste Trajin,2009,MSSP, 65인용
• Complex signal representation : univocal phase and amplitude definition을 위해
*Hilbert Transform(HT) : cancelation of negative frequency components
Bedrosian condition
*Concordia transform(CT) : cancelation of negative frequency components
기계적 고장에 의한 Stator Current Modulation 에 관한 조사

13. 4.[Hilbert versus Concordia transform for three-phase machine stator current time-frequency
monitoring], Baptiste Trajin,2009,MSSP, 65인용
• HT와 CT 비교
These extra harmonics may lead to a misleading diagnosis since pure
AM and pure PM both appear as mixed AM/PM
깔끔함
Slow/Fast
일때가 다름
HT는 Fast
modulation일때
sideband 다름
기계적 고장에 의한 Stator Current Modulation 에 관한 조사

14. [Induction motor stator current analysis for planetary gearbox fault diagnosis under time-varying speed
conditions],2020,MSSP
14
1.
• Air gap flux
• Motor stator current ->amplitude modulation and phase modulation in faulty cases
• Load torque fault-induced torque oscillation
• Rotor angle
PM(t)
Speed oscillation 적분

15. [Induction motor stator current analysis for planetary gearbox fault diagnosis under time-varying speed
conditions],2020,MSSP
15
1.
• when gear fault and rotor eccentricity exist, a series of time-varying
frequency sidebands are expected around the power supply
frequency
&

16. 16
2.
• 기존 : In most of these techniques, time and frequency domain features are manually extracted from a
vibration sensor and used for fault detection and diagnosis.
• 이 논문 핵심 : MCSA for downstream mechanisms (e.g. gearboxes) , Sensor Fusion(feature level이 아닌 data
level) , Deep Learning
• 한계 : load 가 0일 때만 실험, sample - rate 50000Hz , 속도의 종류는 많지만 변속이 아님
• 이 논문에서 참고할만한 점 : 전처리(outlier 제거 이후 2차 버터워스 LPF 사용하여 노이즈 제거 ), 슬라이딩윈도
[Multisensor data fusion for gearbox fault diagnosis using 2-D convolutional neural network and motor current
signature analysis],2020,MSSP
The acquired data from multiple current sensors are fused by a novel 2-D convolutional neural network

17. 17
2.
[Multisensor data fusion for gearbox fault diagnosis using 2-D convolutional neural network and motor current
signature analysis],2020,MSSP
논의 사항 :
1. the information loss is minimized and the correlation between different sensors is preserved by applying
different convolution filters on raw data stacked in a 2D matrix
2. mechanical anomaly within the downstream mechanical components driven by the attached motor
generate unexpected oscillatory motion of the gearbox shaft both rotationally and radially. Such a motion
directly influence on the air gap eccentricity which affects the air gap flux density. The stator will draw
current according to the variation in the electromagnetic field. Since the variations in motor current are
related to motion in downstream components
a fault in the load part of the drive is seen from the induction machine by a variation of the load torque and
these torque oscillations make the stator current modulated as well
3. It needs to be observed that the amplitude and location of sidebands (associated with fault) is not
consistent in spectrums of both phases of motor current (Phase U and Phase W).

18. 18
2.
[Multisensor data fusion for gearbox fault diagnosis using 2-D convolutional neural network and motor current
signature analysis],2020,MSSP
• a fault in the load part of the drive is seen from the induction machine by a variation of the load torque
and these torque oscillations make the stator current modulated as well
Load torque
rotor angle
Stator current

19. 19
3.
Interturn short
[Inter-Turn Short Circuit Detection Based on Modulation Signal Bispectrum Analysis of Motor Current
Signals],2013
Stator faults causes uneven distribution of the air-gap flux waveform around the stator cross section,
which allows the stator currents to be modulated by rotor slot frequency (유도전동기)

20. 20
기계적 고장에 의한 Stator Current Modulation 에 관한 조사
Blodt (2006,2008,2009) 논문 3개
1.[Mechanical Load Fault Detection in Induction Motors by Stator Current Time-Frequency
Analysis],2006,TIA, 270인용
• faults causing torque oscillations
Load Torque Oscillation의 관점에서
Stator Current분석