Condition Monitoring of Electrical Machines ABB MACHsense Solution

Transcription

1 Condition Monitoring of Electrical Machines ABB MACHsense Solution

2 Overview Typical failures in motor Traditional condition monitoring methods Shortfall Solutions ABB MACHsense service July 26, 2012 Slide 2

3 Typical Problems in Electrical Machines Rotating components Cage rotor defects Deliverables Bearing problems Installation problems Power supply quality Voltage [V] Time [s] July 26, 2012 Slide 3

4 Existing Condition Monitoring Systems For Motor health assessment Many plants have In-house condition Monitoring team Vibration Analysis (identifying mechanical condition like bearing, installation quality etc) Measures overall vibration Time domain analysis & FFT Specialized methods like demodulation, phase analysis etc Motor Current Signature Analysis (identifying rotor winding defect) Uses Fast Fourier Transformation of Current spectrum Either single phase or three phase July 26, 2012 Slide 4

5 Rotor Damage Significance Percentage of failure less than 5%, but Broken Rotor Bars can Cause Sparking-Safety Hazard for Ex motors Healthy Bars carry more current- Further damage Torque & Speed Oscillation-Premature failure of bearings Centrifugal forces causes bars to lift from slots-hits stator windings to cause serious damage Customer Need: To have advance intimation to prevent catastrophic failure. July 26, 2012 Slide 5

6 Present Day Condition Monitoring Methods Rotor Bar Damage MCSA-Motor Current Signature Analysis FFT(Fast Fourier Transformation) of Current Signal Identifies 2x slip frequency sideband in spectrum Severity based on sideband height from center frequency July 26, 2012 Slide 6 2x slip frequency sidebands Rule of Thumb: faults are detected when these sidebands meet or exceed -35dB (often referred to as '35 db down') db = Excellent db = Good db = Moderate db = Cracked rotor bars or other source of high resistance db = Multiple sources of high resistance. < 30 db = Severe damage

7 Case using Traditional Methods : False Positive: Rotor Bar Cracks Motor Rating: 750 kw, 1490 rpm, 50 Hz, Application: Chipper, Plant: Pulp & Paper Mill - 20 db Test Conditions: Loading: 33.9% Operating Slip:0.229 Hz Operating freq: Hz This is indicative of rotor bar cracks as per standard analysis The rotor was checked visually, with a dye penetrant No crack or defect in the rotor bar was detected Pulsating torque had resulted in observed sidebands July 26, 2012 Slide 7

8 Case using Traditional Methods : False Negative: Rotor bar Cracks Motor Rating: 210 kw, 2982 rpm, 50 Hz Application: BFP, Plant: Chemical Using the slip from the nameplate (MCSA) does not indicate rotor bar cracks - 57 db - 40 db Test Conditions: Loading: 76.7 % Operating Slip:0.23 Hz (MCSA-nameplate slip based) Operating Slip: 0.27 Hz (Vibration) Operating freq: Hz Slip from vibration indicative of rotor bar cracks as per standard analysis Using the slip from the nameplate does not indicate rotor bar cracks Cracks in the rotor were observed July 26, 2012 Slide 8

9 What is Required? Automatic Slip & Side Band Identification Hz Hz Normalization of Load Not to use Name plate slip information as variation can be upto 20% as per IEC Reduced Spectral Leakage using Adaptive Filtering Processes Does Mathematical mapping to identify peak(correct amplitude and frequency) July 26, 2012 Slide 9

10 On Line condition Monitoring ABB Offering ABB MACHsense-P Portable condition monitoring system used widely by all Local service centers. Measures vibration, current, voltage to identify health condition of Motor from point of Rotor Condition Bearings Installation Power quality Automated report generated by ABB Software Engineer carries unit around plant to collect data-4 to 6 motors a day ABB MACHsense-R Remote condition monitoring system, will be launched in April 12 Works with same technology and software as MACHsense-P. Periodic and detailed report given as per service contract Transfers data wireless to web portal which can be accessed by customer through internet. July 26, 2012 Slide 10

11 ABB MACHsense-P Overview A walk around condition monitoring service POWER SUPPLY Periodic measurements Machine in operating condition Detection of defects and evolution over the time by periodic measurements CAGE ROTOR Preventive maintenance plan based on projected time of defect criticality (over a period of 6 months) ANTI-FRICTION BEARING INSTALLATION Alignment, soft foot, air gap July 26, 2012 Slide 11

12 ABB MACHsense-P Measurements Measurement Either 4 vibrations channels or 6 electrical(3 current & 3 voltage) channels simultaneously High resolution data collector for quick & high speed data acquisition July 26, 2012 Slide 12

13 Case Studies Broken Rotor Bar Client-Petrochemical Motor-4.5MW, 4 Pole, 1500RPM, Sleeve bearings Motor was driving compressor, having no stand by. Highest amplitude 7.76mm/sec DE, Vertical direction July 26, 2012 Slide 13

14 The Analysis Automated Report Current Spectrum Traditional Method After Normalizing signal with respect to load July 26, 2012 Slide 14

15 Confirming Rotor winding damage Verifying sources of Torque Oscillation July 26, 2012 Slide 15

16 Cage Rotor Damage Broken Short Circuiting Ring COG Plant KW Load-Compressor August 11 September 11 July 26, 2012 Slide 16

17 Rotor Bar Damage At low Load Essar Steel Vizag Cooler Fan KW 990 RPM July 26, 2012 Slide 17

18 Current [db] frequency [Hz] July 26, 2012 Slide 18

19 Air Gap Eccentricity The solution Vibration signals from motor core are a measure of electromagn etic forces. Unique sensor mounting location to pick up electrical related signals from vibration. July 26, 2012 Slide 19

20 Traditional methods vs ABB MACHsense-P Advantage of using ABB MACHsense-P Traditional methods (MCSA) Cannot differentiate torque oscillation of rotor bar damage from that of load (compressor, crusher etc) or power supply Common norms used to confirm severity of defect irrespective of load Uses name plate slip Mechanical faults not identified or identified at later stage after fault initiation. Does not consider rotor design and construction of motor (cannot accurately determine the severity of the fault or even identify the defect) ABB MACHsense-P Simultaneous measurement of current and voltage makes it possible to confirm and distinguish reason of torque oscillation Normalizes data according to load to confirm defect of rotor bar, air gap eccentricity etc. Automated slip detection Vibration data gives mechanical condition and confirms findings of MCSA ABB consider rotor design and construction of motor which give an unique index to estimate the fault severity. Number of rotor bar, speed etc. July 26, 2012 Slide 20

21 Other Faults Uses traditional Vibration analysis methods Mechanical Problemso Unbalance o Misalignment o Loosensess Installation-Soft foot Shaft Eccentricity Unbalanced electromagnetic pull, mechanical problems can lead to bearing damage. Customer Need: To identify presence of such problems to plan maintenance action. July 26, 2012 Slide 21

22 Unbalance-Spectrum Traditional Analysis methods July 26, 2012 Slide 22

23 Signature What is the problem here? July 26, 2012 Slide 23

24 What is required? PRINCIPLE COMPONENT ANALYSIS Vibration data ISO - RMS Get SPEED Get HARMONICS ISO standards Harmonic RMS to Total Harm. Distortion Other fault: non-synchronous Principal Components Classification Fault classification + Severity

25 Model Based Analysis ABB MACHsense Solution July 26, 2012 Slide 25

26 Principal Component Analysis Torque Oscillation COG Plant Recirculation Pump 370 KW July 26, 2012 Slide 26

27 Eccentric Rotor Workshop-Taloja Motor-2040KW, 3000RPM, Sleeve Bearing Client reported high vibration in motor Measurements made in Taloja Service Center Decoupled condition Overall vibration 4.85mm/sec DE H, 10.5mm/sec NDE H July 26, 2012 Slide 27

28 Phase Measurement Motor No Load, Decoupled state Magnitude 1X 2X 3X 4X Phase 1X 2X 3X 4X Channel Channel Channel Channel Channel Channel Channel Channel Recommendations: Concentricity of bearing with respect to housing. Run out of rotor. Unbalance in rotor Concentricity of Stator with respect to core. July 26, 2012 Slide 28 Findings: Run out of rotor up to 0.8mm. Bearing Changed. Rotor Balanced Present Vibration 2.7mm/sec.

29 Rolling Element Bearing Causes of Bearing Failure Lubrication High Vibration-Misalignment, Unbalance. Installation Faults Soft Foot Air Gap eccentricity July 26, 2012 Slide 29

30 Sensitivity of different methods to detect bearing faults Early detection Failure Severity of the fault Significant change in high frequency RMS value** Smoke** Change in bearing temperature** Significant change in crest factor** Lubricant debris monitoring* A spall has been developed ABB BeAM ABB BeaCon automatic autocorrelation timedomain Time Off-line envelope method and an experienced analyser* Commonly used methods for bearing faults analysis ** Non-specific methods Off-line envelope method and an inexperienced analyser* July 26, 2012 Slide 30

31 Bearings Vibration Analysis : BeAM ABB Approach Common analysis methods use for the envelope method for bearing fault detection The envelop method uses the envelope of high frequency signals generated by defects and compares it to bearing defect frequencies. The ABB BeaCon automatic analysis uses: the auto-correlation time-domain method to filter out the noisy signals more effectively that traditional method July 26, 2012 Slide 31

32 Bearings Vibration Analysis : BeAM Time [ms] Data sequences that contain only noise Time [ms] Data sequences that contain shock pulse + noise Unfiltered vibration signal. Above signal after proper filtering. The ABB BeAM in addition to the ABB BeaCon automatic autocorrelation timedomain analysis: Perform early shock pulse detector analysis which only extract the shock pulses related to bearing defects using special signal processing methods such as adaptive filtering and likelihood ratios to improve the signal sensitivity. Estimates the following parameters to evaluate the condition of the bearing: Kurtosis, high frequency RMS, maximum energy per shock pulse & integrated energy calculations July 26, 2012 Slide 32

33 ABB Condition Monitoring Case study - Bearings Vibration measurement were taken for two identical Boiler Feed Pump motors. Both measurements were taken for 50 % of machine load. Nameplate details: Power Voltage Current Speed Frequency Poles 2000 kw 6.6 kv 204 A 1487 rpm 50 Hz 4 Overall vibration readings in Motor BFP 3C, serial number: Velocity: 1.02 mm/s Acceleration: 0.46 g Overall vibration readings in motor BFP 3B,Serial Number: Velocity: 1.3 mm/s Acceleration: 1.36 g July 26, 2012 Slide 33

34 ABB condition monitoring Case studies Bearings: Early Warning Machine BFP 3C Bearing OK Suggested action: action category: preferred next measurement: in six months Machine BFP 3B Bearing faulty Suggested action: action category: mandatory change bearing as soon as possible but not later than 3 months July 26, 2012 Slide 34

35 ABB Condition Monitoring Case study Bearing related energy trend (early warning detection) Energy related to bearing for faulty case Energy related to bearing for healthy case Warning Level Possibility of comparing the spectra for each measurement Vibration signal in time domain Vibration signal after filtration Bearing related quantities July 26, 2012 Slide 35

36 frequency [Hz] Traditional methods vs ABB MACHsense-P Advantage of using ABB MACHsense-P Vibration [g's] Traditional Methods- Vibration Analysis Multi channel data acquisition but with max frequency range of 16Khz. No access to electrical problems with traditional way of data collection i.e from bearing housing Custom made tools available for monitoring bearing condition. No automated analysis especially for motors ABB MACHsense-P- Vibration analysis 4 channel simultaneous data collection with frequency range of 20Khz. Uses unique sensor mounting methods to pick electrical signals i.e from motor body Powerful algorithms identifies bearing damage at an early stage Automated report for all electrical motors July 26, 2012 Slide 36

37 ABB Approach Combined Vibration & Electrical Data Single software for vibration and electrical data input Vibration Stator Current Key Condition Parameters July 26, 2012 Slide 37 Stator Voltage Patented processes for defect detection used in analysis software Automated analysis includes slip estimation, normalization of load effects and accounts for constructional aspects Automated report

38 Traditional methods vs ABB MACHsense-P Vibration and electrical Traditional Methods Measures vibration and electrical data with individual instrument Separate software analyzes vibration and electrical data No correlation in analysis Common mode of analysis for different electrical type of electrical machines Manual report generation ABB MACHsense-P Measures vibration and electrical data with same instrument Same software gets input of vibration and electrical data Correlates data like slip Unique algorithms developed for different machines-dol, VFD, SM Automated report July 26, 2012 Slide 38

39 ABB MACHsense-P The Levels Deliverables Cage rotor package: Rotor bar defect Eccentricity Shaft bow Internal misalignment Bearing Package Bearing defects Assembly defects Lubrication issues Sleeve bearings Installation Unbalance Looseness Misalignment Soft foot Power supply quality Voltage unbalance Harmonics Standard Regular condition monitoring Measurements made at nominal operating condition and load About 6-8 motors can be analyzed in a day. Charges can be on a per machine basis Report with standard deliverables. Advanced Trouble shooting to assess root cause. Measurements at nominal condition and at different load/speeds. Root cause analysis & standard deliverables. One or two motors are analyzed in a day. Per day charges applicable July 26, 2012 Slide 39

40 Advantages of ABB MACHsense-P Clear Customer benefits A One Stop Shop for Motor health assessment Combined automated analysis of Current, voltage and vibration Overcomes False Positive and False Negatives involved in traditional methods Automated summary status report issued on site Patented algorithms applicable to each motor type Application specific preventive maintenance plan with final detailed report Can be applicable to any make and size of motor Early warning provides enough time for corrective action July 26, 2012 Slide 40

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