Condition Monitoring of Electrical Machines ABB · PDF fileInstallation Power quality ... Vibration measurement were taken for two identical Boiler Feed Pump motors. Both measurements

Condition Monitoring of Electrical MachinesABB MACHsense Solution

© ABB GroupJuly 26, 2012 | Slide 2

Overview

Typical failures in motor

Traditional condition monitoring methods

Shortfall

Solutions

ABB MACHsense service


Typical Problems in Electrical Machines

Deliverables

Rotating components

Cage rotor defects

Bearing problems

Installation problems

Power supply quality

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Existing Condition Monitoring Systems

Motor Current Signature Analysis(identifying rotor winding defect)

Uses Fast Fourier Transformation of Current spectrum

Either single phase or three phase

Many plants have In-house condition Monitoring team

For Motor health assessmentVibration Analysis(identifying mechanical condition like bearing, installation quality

etc)Measures overall vibration

Time domain analysis & FFT

Specialized methods like demodulation, phase analysis etc


Rotor Damage

Percentage of failure less than 5%, but…

Broken Rotor Bars canCause Sparking-Safety Hazard for Ex motorsHealthy Bars carry more current-Further damageTorque & Speed Oscillation-Premature failure of bearings Centrifugal forces causes bars to lift from slots-Hits stator windings to cause serious damage

Significance

Customer Need:To have advance intimation to prevent

catastrophic failure.


Present Day Condition Monitoring Methods

FFT(Fast Fourier Transformation) of Current Signal

Identifies 2x slip frequency sideband in spectrum

Severity based on sideband height from center frequency

Rotor Bar Damage MCSA-Motor Current Signature Analysis

2x slip frequency sidebands

Rule of Thumb: faults are detected when these sidebands meet or exceed -35dB (often referred to as '35 dB down').54-60 dB = Excellent48-54 dB = Good42-48 dB = Moderate36-42 dB = Cracked rotor bars or other source of high resistance.30-36 dB = Multiple sources of high resistance.< 30 dB = Severe damage

© ABB Group July 26, 2012 | Slide 7

Case using Traditional Methods : False Positive: Rotor Bar Cracks

This is indicative of rotor bar cracks as per standard analysis

The rotor was checked visually, with a dye penetrantNo crack or defect in the rotor bar was detectedPulsating torque had resulted in observed sidebands

- 20 dB

Motor Rating: 750 kW, 1490 rpm, 50 Hz, Application: Chipper, Plant: Pulp & Paper Mill

Test Conditions:Loading: 33.9%Operating Slip:0.229 HzOperating freq: 49.194Hz


Case using Traditional Methods : False Negative: Rotor bar Cracks

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

- 40 dB

Motor Rating: 210 kW, 2982 rpm, 50 Hz Application: BFP, Plant: Chemical

Test Conditions:Loading: 76.7 %Operating Slip:0.23 Hz (MCSA-nameplate slip

based)Operating Slip: 0.27 Hz (Vibration)Operating freq: 49.713 Hz

Using the slip from the nameplate

(MCSA) does not indicate rotor bar

cracks - 57 dB


What is Required ?

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•Reduced Spectral Leakage using Adaptive Filtering Processes•Does Mathematical mapping to identify peak(correct amplitude and frequency)

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Automatic Slip & Side Band Identification

Normalization of Load

Not to use Name plate slip information as variation can be upto 20% as per IEC


On Line condition Monitoring

ABB MACHsense-PPortable condition monitoring system used widely by all Local service centers.Measures vibration, current, voltage to identify health condition of Motor from point of

Rotor ConditionBearingsInstallationPower quality

Automated report generated by ABB SoftwareEngineer carries unit around plant to collect data-4 to 6 motors a day

ABB MACHsense-RRemote condition monitoring system, will be launched in April ‘12Works with same technology and software as MACHsense-P.Periodic and detailed report given as per service contractTransfers data wireless to web portal which can be accessed by customer through internet.

ABB Offering


ABB MACHsense-P

•A walk around condition monitoring service

•Periodic measurements

•Machine in operating condition

•Detection of defects and evolution over the time by periodic measurements

•Preventive maintenance plan based on projected time of defect criticality (over a period of 6 months)

Overview

INSTALLATIONAlignment, soft foot, airgap

CAGEROTOR

POWERSUPPLY

ANTI-FRICTIONBEARING


MeasurementEither 4 vibrations channels or 6 electrical(3 current & 3 voltage) channels simultaneously

High resolution data collector for quick & high speed data acquisition

ABB MACHsense-PMeasurements


Case Studies

Client-PetrochemicalMotor-4.5MW, 4 Pole, 1500RPM, Sleeve bearingsMotor was driving compressor, having no stand by.Highest amplitude 7.76mm/sec DE, Vertical direction

Broken Rotor Bar


The Analysis

Current Spectrum

Traditional Method

Automated Report

After Normalizing signal with respect to load


Confirming Rotor winding damageVerifying sources of Torque Oscillation


Cage Rotor Damage

August 11

September 11

Broken Short Circuiting Ring• COG Plant• 14900 KW• Load-Compressor


Rotor Bar Damage

Essar Steel VizagCooler Fan-32550KW990 RPM

At low Load


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Air Gap Eccentricity

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Vibration signals from motor core are a measure of electromagnetic forces.

Unique sensor mounting location to pick up electrical related signals from vibration

The solution


Traditional methods vs ABB MACHsense-P

Traditional methods (MCSA)Cannot differentiate torque oscillation of rotor bar damage from that of load (compressor, crusher etc) or power supplyCommon norms used to confirm severity of defect irrespective of loadUses name plate slipMechanical 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-PSimultaneous measurement of current and voltage makes it possible to confirm and distinguish reason of torque oscillationNormalizes data according to load to confirm defect of rotor bar , air gap eccentricity etc.Automated slip detectionVibration data gives mechanical condition and confirms findings of MCSAABB consider rotor design and construction of motor which give an unique index to estimate the fault severity.

Number of rotor bar, speed etc.

Advantage of using ABB MACHsense-P

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Other FaultsUses traditional Vibration analysis methods

Mechanical Problems-oUnbalanceoMisalignmento 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.


Unbalance-SpectrumTraditional Analysis methods


SignatureWhat is the problem here?

Vibrationdata

ISO - RMS

Get SPEED

Get H ARMONICS

H armonic RMS toTotal Harm. Distortion

ISO standards

PrincipalComponentsClassification

Fault classification ++ Severity

Other fault:non-synchronou s

What is required?PRINCIPLE COMPONENT ANALYSIS


Model Based AnalysisABB MACHsense Solution


Principal Component Analysis

COG PlantRecirculation Pump370 KW

Torque Oscillation


Eccentric Rotor

Motor-2040KW, 3000RPM, Sleeve BearingClient reported high vibration in motorMeasurements made in Taloja Service CenterDecoupled conditionOverall vibration 4.85mm/sec DE H, 10.5mm/sec NDE H

Workshop-Taloja


Phase MeasurementMotor No Load, Decoupled state

Magnitude 1X 2X 3X 4X Phase 1X 2X 3X 4X

Channel 1 0.011462 0.000356 0.000881 0.001477 Channel 1 -116.638 42.91414 141.1764 35.86918

Channel 2 0.003896 0.002198 0.00149 0.00082 Channel 2 -12.3934 35.60742 144.8034 -25.6252

Channel 3 0.013151 0.008774 0.000652 0.001888 Channel 3 35.63641 156.9605 -74.4833 -159.302

Channel 4 0.012856 0.000357 0.000986 0.001642 Channel 4 54.55921 11.70966 98.6241 24.32922

Recommendations:Concentricity of bearing with respect to housing.Run out of rotor.Unbalance in rotorConcentricity of Stator with respect to core.

Findings:Run out of rotor up to 0.8mm.Bearing Changed.Rotor BalancedPresent Vibration 2.7mm/sec.


Rolling Element BearingCauses of Bearing Failure

Lubrication

High Vibration-Misalignment, Unbalance.

Installation Faults

Soft Foot

Air Gap eccentricity


Sensitivity of different methods to detect bearing faults

Time

Severity of the fault

A spall has been developed

ABB BeAM®

Off-line envelope method and an experienced analyser*

Off-line envelope method and an inexperienced analyser*

ABB BeaCon automatic autocorrelation time-domain

Significant change in crest factor**

Significant change in high frequency RMS value**

Change in bearing temperature**

•Commonly used methods for bearing faults analysis** Non-specific methods

Lubricant debris monitoring*

Smoke**

Early detection Failure


Bearings Vibration Analysis : BeAM®

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

ABB Approach

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Bearings Vibration Analysis : BeAM®

The ABB BeAM® in addition to the ABB BeaCon automatic autocorrelation time-domain 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

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Data sequences that contain shock pulse + noise

Data sequences that contain only noise

Unfiltered vibration signal.

Above signal after proper filtering.


ABB Condition Monitoring

Vibration measurement were taken for two identical Boiler Feed Pump motors. Both measurements were taken for 50 % of machine load.

Nameplate details:

Overall vibration readings in Motor BFP 3C, serial number: 3991201-1Velocity: 1.02 mm/s Acceleration: 0.46 g

Overall vibration readings in motor BFP 3B,Serial Number: 3991201-2Velocity: 1.3 mm/sAcceleration: 1.36 g

Power Voltage Current Speed Frequency Poles

2000 kW 6.6 kV 204 A 1487 rpm 50 Hz 4

Case study - Bearings


ABB condition monitoring

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

Case studies – Bearings: Early Warning


ABB Condition MonitoringCase study – Bearing related energy trend (early warning detection)

Bearing related quantities

Energy related to bearing for healthy case

Energy related to bearing for faulty case

Warning Level

Possibility of comparing thespectra for each measurement

Vibration signal in time domain

Vibration signalafter filtration


Traditional methods vs ABB MACHsense-P

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 bodyPowerful algorithms identifies bearing damage at an early stageAutomated report for all electrical motors

Advantage of using ABB MACHsense-P

Traditional Methods-Vibration Analysis

Multi channel data acquisition but with max frequency range of 16Khz.No access to electricalproblems with traditional way of data collection i.efrom bearing housingCustom made tools available for monitoring bearing condition.No automated analysis especially for motors

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ABB Approach

Single software for vibration and electrical data input

Combined Vibration & Electrical Data

Vibration

Stator Voltage

Stator Current

Patented processes for defect detection used in analysis softwareAutomated analysis includes slip estimation, normalization of load effects and accounts for constructional aspects

Key Condition Parameters

Automated report


Traditional methods vs ABB MACHsense-PVibration and electrical

ABB MACHsense-PMeasures vibration and electrical data with same instrumentSame software gets input of vibration and electrical dataCorrelates data like slipUnique algorithms developed for different machines-DOL, VFD, SMAutomated report

Traditional MethodsMeasures vibration and electrical data with individual instrumentSeparate software analyzes vibration and electrical dataNo correlation in analysisCommon mode of analysis for different electrical type of electrical machinesManual report generation


ABB MACHsense-P

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

Deliverables

Cage rotor package:Rotor bar defectEccentricityShaft bowInternal misalignment

Bearing PackageBearing defectsAssembly defectsLubrication issuesSleeve bearings

InstallationUnbalanceLoosenessMisalignmentSoft foot

Power supply qualityVoltage unbalanceHarmonics

The Levels


Advantages of ABB MACHsense-P

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

A One Stop Shop for Motor health assessment

Clear Customer benefits

Documents

Condition Monitoring of Electrical Machines ABB · PDF fileInstallation Power quality ... Vibration measurement were taken for two identical Boiler Feed Pump motors. Both measurements