Electro-Mechanical Systems Laboratory19 Reber Building

Mechanical EngineeringPenn State University

University Park, PA-16802Phone: (814)-863-4346

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Contents

1 People 1

2 High-speed fatigue testing apparatus 2

3 Surface Characterization 7

4 Multi-degree of freedom mechanical vibration apparatus 10

4.1 Hardware implementation and software structure . . . . . . . 12

5 Electric Motor set-up 14

5.1 Motor and Motor-Mount . . . . . . . . . . . . . . . . . . . . . 145.2 Motor Controller . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.2.1 Controller . . . . . . . . . . . . . . . . . . . . . . . . . 165.2.2 Interface . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.3 Motor Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.3.1 Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.3.2 Current Sensor . . . . . . . . . . . . . . . . . . . . . . 195.3.3 Isolator . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.4 Details of the experiments performed . . . . . . . . . . . . . . 205.4.1 Controller Block . . . . . . . . . . . . . . . . . . . . . 205.4.2 Direct magnetic flux linkage estimation block . . . . . 215.4.3 Operating Condition Block . . . . . . . . . . . . . . . 225.4.4 Input and Output Block . . . . . . . . . . . . . . . . . 22

5.5 Demagnetization Procedure . . . . . . . . . . . . . . . . . . . 235.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

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1 People

Name Email

Principal Investigator: Professor Asok Ray axr2@psu.eduFaculty Researcher: Professor Jeffrey Meyer mayer.engr@psu.eduFaculty Researcher: Professor Pan Michaleris pxm32@psu.eduSenior Research Personnel: Dr. Abhishek Srivastav axs964@psu.eduSenior Research Personnel: Dr. Shalabh Gupta szg107@psu.eduSenior Research Personnel: Dr. Eric E. Keller eekeller@psu.eduGraduate Student: Dheeraj S. Singh dss240@psu.eduGraduate Student: Devesh K. Jha devesh.dkj@gmail.com

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2 High-speed fatigue testing apparatus

This servo-hydraulic fatigue test apparatus is built upon a computer-controlledMTS 831.10 Elastometer Test System. The following sub-systems are inte-grated for in-situ monitoring of test specimens under static or dynamic loadsusing optical, ultrasonic and acoustic emission sensing modalities.

Figure 1: High-speed fatigue testing apparatus

Hardware

B Fatigue test equipment is a MTS 831.10 Elastometer Test Systemthat can work at a loading frequency ranging from 0.1 to 200 Hz; thestatic load ratings of the test-set are ± 15kN and ±50mm

B Long Distance Traveling Optical Microscope consists of an Olympusmicroscope mounted on a 3-axis precision stage and is fitted with a dig-ital camera from DALSA. Together with the camera, the microscopecan resolve images on the order of 1 micron per pixel at a distance of≈ 22 mm.

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Figure 2: Ultrasonic Flaw Detection

B 3-axis linear motion stages consists of three stepper motor-drivenprecision stages that that have resolution of 1 µm in each axis. Thisis used to control the location and focus of the microscope.

B Ultrasonic Flaw Detector is a piezo-electric transducer that injectswaves into the specimen and is spatially installed across the crack planeto measure the signal. The signal energy is attenuated as a functionof damage.

The signal from one of the ultrasonic transducers consists of a spikepulse that is modulated into a band-limited signal with frequencies,ranging from 2 to 4 MHz. Alternatively, another transducer may usea gated 5 MHz sine wave signal. Both transducers emit a signal for avery short portion of the measurement cycle. The ultrasonic measure-ment data is collected asynchronously from the test specimens undercyclic loading. Upon crack formation, ultrasonic data may be col-lected when the crack is fully open and thus the attenuation is at itsmaximum. Generally, this phenomenon does not significantly affectthe observations until the crack length is large enough to almost fullyattenuate the ultrasonic signal. In addition to ductile alloys, the ap-paratus has the capability to test matrix composites for investigationof material behavior changes over a prolonged period of time due tofatigue damage.

B Acoustic Emission (AE) occurs when transient elastic waves are pro-duced by a sudden redistribution of stress in a material. An externalstimulus such as change in pressure, load, or temperature can triggerlocalized sources to release of energy. This energy propagate throughthe material in the form of stress waves and can be picked up usingrelevant sensors. Sources of AE can be various such as - initiation andgrowth of cracks, slip and dislocation movements in metallic materials.

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Composites, on the other hand, produce AE via phenomenon such asmatrix cracking, fiber breakage and de-bonding.

Current set-up has acoustic emission sensors from Physical Acoustic

Corporation model R15. These sensors can pick-up elastic waves -plane waves (angle of incidence normal to the face of the sensor) andsurface waves (angle of incidence transverse or parallel to sensor face)with peak sensitivity 63 V/(µbar) and 69 V/(m/s) respectively. Theoperational frequency range of the sensor is 50 - 200 kHz. Receivedwaveforms can be analyzed to get parameters such as rise time, ampli-tude and energy. Localization of the AE source can be done using thetime of arrival and multiple sensors. Also, isolation of spurious noise -such as chatter from the clamping bolts, can be done by filtering basedon time of arrival to localize the region of interest.

Software

Data acquisition and communication is achieved by dedicated software tocontrol and monitor each of the subsystems. The following software havebeen written and integrated for this purpose

B Station Manager for MTS Elastomer This software was provided bythe MTS corporation and is being used to control the Elastomer forload and frequency settings for an experiment. It has the capability ofproducing load cycles in a number of waveform shapes such as sinu-soidal and square. It allows to run both force mode and displacementmode experiments when the control variable is force and displacementrespectively.

B Fatigue Data Monitor This software poles into the controller for theMTS elastomer system to gather fatigue data such as load, load cy-cles, displacement, etc. It then post the acquired information over aTCP/IP network for other programs to download and process.

B Stage Motion Controller This software has been written to controlthe motion of the three linear stages forming the triaxial motion set-up. The three axes are Focus Axis, Horizontal Axis and the VerticalAxis. Each axis can be controlled separately with an accuracy of 1micron. The software stores the current location of all the axes whichis used to measure the length of the crack and monitor its evolutionwith load cycles. Crack lengths and stage positions are clubbed intoa data packet and posted over a TCP/IP network for other clientprograms.

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B Video Server This program controls the camera to get a running videoor still images of the specimen at specified times. This is a serverapplication and can be hooked up from remote machines to view andsave images of the specimen.

B Video Client This is a client program which talks to the Video Serverto acquire video streams and still images over the network. More thanone clients can be connected to the Video server from remote machinesto observe and save image data.

B The HUB This software, as the name suggests, is used to link differentsoftware posting data over the TCP/IP network so that the data canbe synchronized and stored at a desired location. This program talksto the Stage Motion Controller for microscope positions, the StationManager for the load, displacement and load cycle values. These valuesas used to stamp the images, captured by the Video Server and Client,for load cycles and crack length values. It also sends this information

Figure 3: Software communication diagram

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to the Ultrasonic Scope to store cycle and load information with thestored waveforms.

B Scope This software is used to display the data received from the ul-trasonic transducers and store it at a given location. A data windowcan be selected by the user to specify the data range of interest. Wave-forms are stamped with load and cycle information received form theHUB. Using this software, data can be directly converted into MAT-LAB usable form for further processing.

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3 Surface Characterization

Zygo interferometer, Fig. 5 is a surface characterization equipment whichuses light beam splitting and interference between reference beam and theone reflected form the test surface to profile the peaks and valleys. Measure-ments are non contact and non destructive and can be performed in ambientlight conditions.

A three-dimensional profile of the specimen surface is generated by aNewView 5000 surface interferometer apparatus that measures the surfaceheights of the scanned area ranging from 1nm to 5000µm with a resolutionof 0.1nm at the vertical scan speeds up to 10µms−1 It can scan areas upto 50 mm× 50mm using its unique image stitching capabilities. This in-terferometer uses a non-contact scanning method using light interferometryto acquire ultrahigh resolution images. It uses a closed-loop piezoelectricscanner employing low-noise capacitive sensors to ensure accurate and re-peatable linear motion over the full range of a scanned area. The surfaceinterferometer is equipped with the software MetroPro that is used to oper-ate the interferometer and to store the surface profile data in a convenientformat for further data processing.

Currently this set-up is being used to characterize the damage site ina specimen progressively loaded to higher number of cycles under fatigueload. The goal is detect early signatures of damage - manifesting as surfacedeformations before a surface crack becomes observable through the opticalmicroscope.

A typical results of surface characterization experiments of fatigue dam-age site is shown in Fig 6.

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Figure 4: Interferometer for surface characterization

Figure 5: Working Principle of the interferometer

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NoLoad 67.5k cycles

68.5k cycles 69k cycles

Figure 6: Surface profiled: Notch side; Scan size 0.70 × 0.75mm; Specimen:CompactSp15

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4 Multi-degree of freedom mechanical vibration

apparatus

This experimental apparatus has been designed and fabricated specificallyto study the characteristics of complex mechanical vibration systems thathave the capacity of multiple degrees of freedom for motion along differ-ent coordinate directions. This special purpose experimental apparatus isshown in Figure 7. The experimental apparatus can be used to replicate thevibration response of a mechanical structure such as a support beam underexternal excitation (e.g. seismic). The apparatus has three principle degreesof freedom that arise from three actuators that provide the capability of mo-tion along three different directions. Each of the actuator is excited usinga remote computer through an electro-hydraulic position feedback controland is capable of providing a force up to 3,400 kgf. The actuators can beexcited over a wide band of frequency range and can produce oscillations ofsignificant magnitude.

Figure 7: Multi-degree of freedom mechanical vibration apparatus

The experimental apparatus consists of a rectangular base that is boltedto the ground and supports two beams - horizontal (Bh) and vertical (Bv),and three actuators - bottom (Ay), back (Az) and horizontal (Ax). Figure 8gives a two-dimensional schematic of the apparatus. The base of the verticalbeam Bv is connected to the bottom actuator Ay that moves the verticalbeam in the yz-plane about the hinge hy. The back actuator Az is mountedon the vertical beam and moves the horizontal beam Bh, pivoted at hz, in

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(b)

VerticalBeam

HorizontalBeam

BottomActuator

VerticalActuator

Test Beam

x

z

y

P

hy

hz

(Ay)

(Az)

HorizontalActuator

Test Beam

Phx(Ax)

(Bv)

(Bh)

(a)

hz

hx

Figure 8: 2-D schematic of the Multi-degree of freedom apparatus (a) TopView (b) Side View

the yz-plane. The horizontal actuator Ax rotates the test beam about thepivot point hx in the xy-plane. Thus, the angular motion of the beams Bv

and Bh about the hinges hx, hy and hz are controlled by the linear motionsof the three actuators Ax, Ay and Az. For small angular displacements ofthe beams, their angular motions translate into the movement of the pointP in three axes - x, y and z. The test beam is mounted at point P and itcan be given a desired base excitation in all or any direction of motion. Thestructure of beams is made from 6mm thick hollow square steel sections.

The multi-degree of freedom mechanical vibration apparatus in Figure 7is logically partitioned into two subsystems as described below.

a) The plant subsystem consists of the mechanical structure includingflexible hinges that connect the beams, the hydraulic system, and theactuators and

b) The control and instrumentation subsystem consists of control comput-ers, data acquisition and processing system, communications hardwareand software, and the sensors. The sensors include: i) linear variabledifferential transformers (LV DT ) for displacement measurement andb) integrated circuit-piezoelectric shear accelerometers that are used

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x

z

y

Abase Atip

m

ym

yref

Figure 9: Schematic of the test beam structure

to measure the vibrations of the tip and the base of the horizontalbeam (see Figure 9). The sensitivity of sensor is 2.727 mV/ms−2. Thecontrol system and data acquisition software is executed under DSpaceplatform on the windows operating system. The feedback control sys-tem shown in Figure 10 is installed on a Pentium pc along with neces-sary A/D and D/A interface to the feedback amplifiers connected tothe sensors and actuators of the test apparatus.

Figure 10: Control circuit for the mechanical vibration apparatus

4.1 Hardware implementation and software structure

The multi-degree of freedom mechanical vibration apparatus (Figure 7) isinterfaced with a DSpace Data Acquisition Board having 16 A/D channelsand 8 D/A channels. Data acquisition is carried out with a sampling rate at 1KHz for monitoring and control. The time series data for statistical patternrecognition can be decimated as required. The real-time instrumentationand control subsystem of this test apparatus is implemented on a PentiumPC platform. The software runs on the Windows XP Operating Systemand is provided with A/D and D/A interfaces to the amplifiers serving thesensors and actuators through the Control desk front end. The Controldesk front end loads a Simulink (Matlab based) module on to the data

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acquisition card to perform real-time communication tasks, in addition todata acquisition and built-in tests (e.g., software limit checks and saturationchecks).

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5 Electric Motor set-up

The Permanent Magnet Synchronous Motor (PMSM) test-bed developedfor validation and proof-of-concept of the fault detection by symbolic identi-fication technique has been carried out in several parallel stages, all of whichhave been finally integrated and tested. The following sections describe thevarious parts of the PMSM test-bed.

5.1 Motor and Motor-Mount

The properties of the PMSM used in the experimental setup are listedbelow:

B General Parameters

− Cont. Stall Torque Lb-In (N-m): 3.90 (0.45)− Cont. Stall Current: 1.49− Peak Torque Lb-In (N-m): 15.93 (1.8)− Peak Current: 5 Amp

B Electrical Parameters

− Torque Constant Lb-In/Amp (N-m/Amp): 3.10 (0.35)− Voltage Constant Vpk/KRPM (VRMS/KRPM): 30.4 (21.48)− Resistance: 11.95− Inductance (mHy): 16.5

B Mechanical Parameters

− Inertia Lb-In-s2 (Kg-cm2): 6e-005 (0.06774)− Speed at 160 Bus Volts (RPM): 4000− Max Speed (RPM): 10000− No. of Motor Poles: 4

B Feedback Device

− Encoder Line Count 2500ppr

Figure 11 also shows the aluminum motor mount which has been de-signed and manufactured with adjustable sliding support for easy alignmentof the motor with the dynamometer bearing.

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5.2 Motor Controller

The motor controller has been developed in the Matlab/Simulink environ-ment, and interfaced with the hardware through a DSpace card. The fea-tures of the DSpace card are listed below:

B Advanced Control Education Kit 1103 consisting of

B DS1103 PowerPC GX / 1GHz controller board,

B 32 MB application SDRAM,

B 96 MB communication SDRAM,

B PX4 expansion box with high speed serial host interface consistingof DS814, PC-side PCI bus DS817 and opto-cable, CLP1103 Con-nector/LED Panel, CDP Control Development Software Package andMicrotec C Cross Compiler with USB dongle

Figure 11: The PMSM and its mount

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Figure 12: Speed controller implemented in Matlab/Simulink environment

5.2.1 Controller

The speed controller developed is displayed in Fig. 12. The purpose of devel-oping the speed controller is to ensure that the demagnetization experimentsare carried out at a uniform speed of operation thus ensuring uniformity intesting conditions. The controller employed is a simple PI controller in-volving two feed-back loops. The encoder interface block reads the motorposition and speed, which are respectively used in the reference frame trans-formations and a feed-forward term. The current measurement block readsthe line currents which are measured by the Hall Effect sensors. A separateboard has been designed and fabricated for accommodating the Hall Effectsensors, which has been described later. The speed controller is built on topof a torque controller by adding an outer loop with a separate proportional-integral control. The rotational speed read-out from the encoder interfaceis compared with the commanded speed and passed through the PI controlto generate quadrature axis current command, which is proportional to thetorque. The current readings are then compared with the desired values ofthe currents which are dictated by torque requirements in the PI controlblock. The command voltage thus obtained is reference frame transformedand the corresponding duty cycles are generated in the Duty Cycle Gener-ator block. The rest of the blocks are mainly related to over-voltage and

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over-current shutdown of the motor.

5.2.2 Interface

Figure 13: ControlDesk interface for graphical displays and commands

The ’ControlDesk’ has been used to create a user-friendly interface forcommanding the permanent magnet synchronous motor, for real time mon-itoring of the control signals, as well as data capture. A screen shot of theControlDesk interface that has been developed, has been shown in Fig. 13.The graphical displays show the direct and quadrature axis current and volt-ages, as well as the rotor speed and orientation. The bus voltage is displayedas a safety flag.

5.3 Motor Drive

The motor drive circuit for investigating failure in PMSMs has been de-signed using the Integrated Power Module for Appliance Motor Drive: IRAMS10UP60A.The electronic drive may be logically divided into three sub-circuits, whichare explained in the following sections. A schematic of the electronic drive,constructed in Eagle, is shown in Fig. ??.

5.3.1 Drive

The 600V IRAMS module contains six IGBT die each with its own discretegate resistor, six commutation diode die, one three phase monolithic, level

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shifting driver chip, three bootstrap diodes with current limiting resistorand an NTC thermistor/ resistor pair for over temperature trip. The overcurrent trip circuit responds to an input voltage generated from an externalsense element such as a current transformer or sense resistor.

The micro controller provides all of the logic level PWM signal inputsto the IRAMS module as well as processing current and temperature analogsignals fed back from the module. The detailed motor drive circuit usingthe IRAMS10UP60A modules is illustrated in Fig. ??No high-side floatingpower supplies are required because the bootstrap capacitors provide powerfor the three independent high side driver channels.

Motor current is monitored by external Hall effect sensors in each phaseleg of the IGBT inverter. Under normal operating conditions, IGBT tem-perature is continuously monitored by the internal NTC thermistor feedinga temperature dependent voltage to the micro processor. This voltage alsofeeds the internal shut down function of the driver which terminates all 6

! " # $ % & ' () * + , - . / 01 2 3 4 5 ! 6 7 8 6 39 : ; ; < = > + / / . ? @A / B ? 0 C + ) . /

D E E E F G G H I J J K L M N O PFigure 14: Several components of the PMSM drive and their interconnec-tions

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Figure 15: The full setup with two drives, dynamometer and computer

drive signals when activated. In the event of an over current caused by astalled motor or other fault condition, the active low signal from the microcontroller turns off the external N-channel MOSFET and over rides the tem-perature signal causing instant shut down. After shutdown the 1.5W/6.8nFnetwork provides a reset function to re-establish IGBT gate drive followinga 9mS delay. The micro processor can be programmed provide permanenttermination of its outputs following a predetermined number of resets.

5.3.2 Current Sensor

The current sensors used in the setup and shown in Fig. 14 are closed loop(compensated) Hall Effect current transducers LA 55-P procured from LEM.The gains are controlled by using a LM124 chip consists of four independent,high gain, internally frequency compensated operational amplifiers whichwere designed specifically to operate from a single power supply over a widerange of voltages. The OP Amp gains are adjusted by resistors.

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5.3.3 Isolator

The DSpace controller voard has been electrically isolated from the highvoltage side of the drive by using six high speed Photodiode Darlington opto-couplers, shown in Fig. 14. The 5 volt input to the opto-coupler is providedby a 3-Terminal 1A Positive Voltage Regulator LM7805. The LM7805 seriesof three terminal positive regulators are available in the TO−220/D−PAKpackage and with several fixed output voltages, making them useful in a widerange of applications.

5.4 Details of the experiments performed

The purpose of the experiment is to validate advanced FDI algorithms forprognosis and diagnosis of demagnetization failure in permanent magnetsynchronous motors. The needs of the experiment necessitates a highlyspecialized PMSM apparatus with

1. A controller that enables it to run at a specified speed under varyingload torque conditions

2. A method for imposing various load torques on the motor

3. Instrumentation for data collection and storage

4. A method for direct estimation of the level of demagnetization

5. A method for accelerated demagnetization of the motor

The schematic of the entire experimental setup has been shown in Figure 16.The whole figure is divided into several blocks for convenience, each of whichwill be described next.

5.4.1 Controller Block

The PMSM used in the experiment is a three-phase four-pole device ratedat 160 V bus voltage, 4000 rpm and is fed by a pulse-width-modulated(PWM ) inverter. The stator resistance of the motor is Rs = 11.95 Ω; thequadrature-axis and direct-axis inductances are: Lq = Ld = 16.5 × 10−3H;and the rotor inertia is J = 0.06774 kg cm2.

Two PI controllers in two loops have been employed for controlling thepower circuit that drives the PMSM . The inner loop regulates the motor’sstator currents, while the outer loop regulates the motor’s speed. In this

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Q RS TS UV W X Y Z W [ \ ] ^ _ [ W `Y a b ^

c d e f g hc i e f g hc j e f g hk l m n o e f g hY \ p X q r Q Rc m n o e f g hc m n o s tS uv w xy b s ^ [ Z ^ [z |

~ R T u W b Z [ W ^ [

v x

¡ ¢ £ ¤ ¢ £ ¥ ¦ ¤ ¢ £ § ¨ © c ª « c c ¬ © ­® ¯ l ° l ¦ ±² ³ W [ \ ] ^ ´ s µ ´ s t ´ s ¶ · c ¸ © ª c ¹ º ¢ » º l ¦ ¼ ½ ± ¾ ¿ c ¸ © c ¬ À Á Â ÃÄ Å Æ Ç È É

Figure 16: Inverter-driven permanent magnet synchronous motor (PMSM )system

control scheme, the error in the measured and the commanded speed gen-erates the command quadrature axis current, which is directly proportionalto the electromagnetic torque if the direct axis current is maintained to be0. The line currents ia, ib and ic are then measured. The reference valuesare compared with the actual values of the currents, and the error signal,thus constructed is used for generating the gate turn on/off commands.

5.4.2 Direct magnetic flux linkage estimation block

As the permanent magnet inside the PMSM slowly deteriorates, it is im-perative to be able to measure the extent of demagnetization by some kindof direct technique, at each stage of demagnetization, so that the degree ofanomaly predicted by SDF can be mapped to this physical quantity. Severalresearches have dealt with the estimation of the flux of a PMSM . It is ofno doubt that the no-load test method has become the most popular one. In

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this method, an auxiliary motor is required to drive the PMSM at constantspeed. The windings of PMSM are at open-circuit so that the flux can beestimated by the EMF of the PMSM . The two phase stator voltage in therotor reference frame is given by

vr = Rir + Ld

dtir + ωreJ

(

Lir + λrPM

)

(1)

Here

J =

[

0 −11 0

]

is the 90o rotation matrix. Under steady state conditions, the derivative ofthe current vector is dropped, and the voltage expression becomes:

V r = RIr + ΩreJ(

LIr + ΛrPM

)

(2)

where Ωre is the steady state electrical rotor velocity. In open circuit thereare no currents flowing in the windings of the machine, so the voltage isentirely due to the permanent magnet flux linkage, hence

‖V ‖ = ‖JΩreΛrPM‖ =

P

2ΩrΛPM (3)

The permanent magnet flux linkage is therefore

ΛPM =‖V ‖P2Ωr

=

√

23Vl−l RMS

P2

2π rpm60

(4)

At each stage of demagnetization, the line-to-line voltage and the motorspeed in rpm is recorded. The permanent magnet flux linkage is estimatedfrom these following Eqn. 4.

5.4.3 Operating Condition Block

The desired rpm and the load torque is set in the operating condition block.The load torque is directly set by the dyne.

5.4.4 Input and Output Block

All the variables are captured and stored in the output block, while theinput voltage commands are also saved in the input block.

It may be noted, that blocks 5.4.1 and 5.4.2 are never engaged simultane-ously, because that would result in a fight between the external back-drivingmotor and the PMSM controller.

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ÎÐÑ Ò Ó Ò Ô Õ Ô Ò Ö Ê × ØÙË

ÌÚ Û

Ð Ó Ê Ó Ò Ô Õ Ô Ò ÖFigure 17: Scheme for demagnetization of the PMSM

5.5 Demagnetization Procedure

The electromagnetic torque is proportional to the cross-product betweenthe current vector and the permanent magnet flux linkage vector. For agiven current magnitude, torque is therefore maximized if the direction ofthe field generated by the stator windings is perpendicular to the directionof the field generated by the permanent magnets. The resulting torqueattempts to align these fields. The PWM controller attempts to generatethe line current in the three phases in such a way, that this orthogonality ismaintained. Figure 17 illustrates these concepts.

It may be noted that orientation feedback is vital to this scheme, since3-phase to 2-phase conversion is dependent upon correct estimation of therotor angle. In the present experiment, during demagnetization, just enoughoffset is added to the encoder orientation so that instead of being orthogonal,the stator winding field directly opposes the field generated by the perma-nent magnets. Thus, since the two fields are aligned, no torque is generated,instead the permanent magnets slowly lose their magnetism. The consider-able amount of heat generated in the process enhances the loss of magneticproperty in the permanent magnets.

The temperatures which mark the end of each individual demagneti-zation run and the corresponding reduction in the magnetic flux linkagemeasured by the no-load test method (section 5.4.2) are listed in Fig. 18

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80 100 120 140 160 1700

0.5

1

1.5

2

2.5

Temperature

% R

eduction in M

agnetic F

lux

0.3879

0.8708

1.3498

1.8946

2.2743

Figure 18: Variation of Magnetic Flux Linkage with Temperature

5.6 Conclusion

The PMSM experimental setup developed in the Electro-Mechanical Sys-tems Laboratory provides a unique test-bed for performing accelerated de-magnetization experiments on permanent magnet motors in a controlledenvironment and validate advanced algorithms for failure prognosis and di-agnosis.

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