2012 International Symposium on Power Electronics, Electrical Drives, Automation and Motion Development and Performance Investigation of Permanent Magnet Synchronous Traction Motor M Franko*, J Kuchta*, J Buday* * EVPÚ a.s., Electrotechnical Research and Projecting Company, j.s.c., Trencianska 19, SK - 018 51 Nova Dubnica (Slovakia), franko@evpu.sk, kuchta@evpu.sk, buday@evpu.sk been designed some variants of rotor with different PM arrangements This approach to the solution of unifying design as ATM and PMSM, allows the customer to offer traction motor of the same size and weight, but at a slightly higher price with higher efficiency In this paper attention is paid to design of PMSM that was based on ATM with an output of 210 kW Basic parameters of the ATM were verified on the test as EVPÚ j.s.c laboratory as with sinusoidal supply and as the traction power frequency converters, and thus it can be based on real measured operating parameters Based on the measured temperature increase winding of the real ATM 210 kW, considering the available real PM, we rate as the target power of the PMSM set as rated power of 160 kW and reduce the temperature class from C to F Basic parameters of the ATM are shown in Table I Abstract The paper deals with the design of permanent magnet synchronous traction motor (PMSM) that was based on volume and stator windings of asynchronous traction motor with an output power 210 kW The proposed PMSM was built with permanent magnets (PM) placed on the surface of the rotor There will be described the basic parameters as well as analytical analysis of losses in the machine, with emphasis on losses in PM, that depend on the size of PM and they may form a significant component of loss in the paper In the paper will be also described the results of measurements realized on PMSM with rotor made in the initial versions of the rotor and three other modifications realized on the built rotor and their experimental verification and valuation in comparison with the theoretical knowledge Finally they will be compared to the parameters of asynchronous traction motor (ATM) and PMSM with recommendations for mass production of the PMSM for applications in the traction vehicle TABLE I Index Terms analysis and design of electrical machines, losses, measurement, permanent magnet, permanent magnet synchronous motor, traction motor type rated power voltage nominal current rated torque nominal frequency nominal speed connection pole pairs efficiency power factor isolation class cooling I INTRODUCTION Target requirements for design of PMSM for traction application are: - the expected higher efficiency of PMSM as ATM (due to the absence of losses in the rotor winding), - lower weight and volume PMSM as ATM, - PMSM with excitation by rotor PM provides the ability of motor brake in resistors in case of failure of the traction converter, - PMSM made with a larger number of poles enables to make the drive powered rail vehicle (HDV) without gearbox, that is a drive component with major dimensions, weight and price have a direct impact on the final transfer efficiency of the engine torque to the driving wheel-set Noted parameters and especially efficiency of PMSM over ATM led us to intent design, construction and performances investigations of the traction motor of this type ATM210C70Hz425V PN 210 kW U 425 V 332.2 A I1 1018.5 Nm TN fN 67 Hz nN 1971.1 min-1 Y 2p η 0.94 cos φ 0.909 C 240°C forced Content research and development work of the design PMSM was: - selection of the appropriate rotor configuration and arrangement of the permanent magnets (on the surface, inside, combined); - calculation of the PMSM magnetic circuit determining the volume of PM, the calculation of the magnetic field distribution in the air gap, the calculation of moments, reactances et al In these works were tested several alternatives of configuration rotor layout with PM on surface PM or in a rotor For the design and implementation of a prototype 160 kW PMSM was chosen variant with PM mounted embedded to the rotor surface, which seemed like the easiest way of implement the first prototype PMSM Simulation results of magnetic field distribution of the selected configuration option with PM embedded to the II PMSM DESIGN Electromagnetic and thermal design of PMSM based on volume of ATM foreign manufacturer [10], characterized with the internal stator bore pack is the same for the power range of ATM from 70 to 210 kW and single dimensional types differ only with an active length of the stator and rotor For these varieties have 978-1-4673-1301-8/12/$31.00 ©2012 IEEE THE NAME PLATE AND OTHER PARAMETERS OF THE BASE ATM (PRODUCER [10]) 70 surface of the rotor in no-load state can be seen in Fig in the state with nominal current in Fig Fig 2D magnetic flux distribution in cross section of PMSM at no load state and air gap magnetic flux density waveform and harmonic analysis of PMSM magnetic flux density Fig 2D magnetic flux distribution in cross section of PMSM at nominal current I=332.3; torque M=1191.9 Nm and air gap magnetic flux density waveform harmonic analysis of PMSM magnetic flux density x switching frequency fsw 750 Hz Overall losses in the permanent magnets are calculated as: k gM 'PM 2S pnMx nMz f sw2 Bˆ h2 III PERMANENT MAGNET LOSSES To determine the efficiency of an engine is necessary to determine the motor losses In addition to known components of losses such as losses in the stator windings, stator iron losses, iron losses in the stator tooth and mechanical losses is necessary for machines with PM on surface consider also the losses in the PM of rotor Rotor losses in synchronous machines with permanent magnets are usually neglected, because the main rotor flux is constant However, when running from converter to be a time-dependent harmonic field, which is not neglected Alternating flux penetrates into magnets and causes losses in them Theory of losses calculation in permanent magnets due to eddy currents that are described in [5,11,12] In Fig is a sketch of one pole of the machine with the appropriate size and shape and dimensions of the permanent magnet: x dimensions of the permanent magnet (hM x wM x lM): 4.3 x 14°(# 27.16 mm) x 50 mm; x one rotor’s pole is divided into (nMx x nMz): x 13 pc, totally 260 pc where: - p is number of pole pairs; - nMx is the number one magnet pole arc in the direction of the x-axis; - nMz is the number one magnet pole arc in the direction of the z-axis; - Bh harmonic flux density in the air gap; - UM resistivity of magnet; - kgm coefficient of geometry, that calculated according the magnet’s dimension at which the equation is dependent on relation between length and width of magnets The sum of the losses of individual harmonic components without addition to the 3-and the multiple to acquire permanent magnet losses in the rotor 'Pr (highlighted in Table II.) 14° 50 4,3 Permanentný Permanent magnet magnet UM 4,5 R113,3 R109 179 113,5 115 70 ° I2 x 48 Fig PMSM: Cross section of motor pole, shape, dimensions and radius of the permanent magnet, 3D model of designed rotor, photography of rotor’s sheet 71 TABLE II THE IMPACT OF A CHANGE OF PM NUMBER TO ROTOR’S LOSSES 2x3 2x4 2x5 x 10 x 12 x 13 10 x 13 10 x 20 10 x 26 Number of PM 67.89 67.89 67.89 27.16 27.16 27.16 13.58 13.58 13.3 PM wM 216.66 162.5 130 65 54.17 50 50 32.5 24.8 dimensions lM 4.3 (mm) hM kgm3 kgm1 kgm1 kgm1 kgm1 kgm1 kgm3 kgm1 kgm1 Coefficient of 2.429.10-8 1.627.10-8 9.772.10-9 4.167.10-10 2.726.10-10 2.311.10-10 4.49.10-11 2.61.10-11 1,44.10-11 PM geometry 25599 22865 17162 3659 2872 1024 915 660 PM losses (W) 2638 Quotient of losses to 12.2% 10.9% 8.2% 1.7% 1.4% 1.3% 0.5% 0.4% 0.3% nominal power PN=210kW Used in: Version Version Table II refers to the effect of changing dimensions of PM and therefore pieces of the PM too, that make one pole of the machine The increasing number of magnets means reduction of losses For realization was chosen arrangement with 5x13 pieces of PM per machine pole that has been a compromise in consideration of work time consuming and lower cost of PM’s acquisition Doubling the number of PM (10x13) would reduce the loss of 0.75% (relative to total output), but would increase the labour intensive construction as well as the price Effect of loss depends on the size of the magnet and it reflects the variable that describes the geometry of the permanent magnet, coefficient of geometry kgM1 where index expresses assumptions that are basis for deriving the relation of the loss in the PM (lM> wM) IV RESULTS OF DESIGN AND VERIFICATION OF PMSM, MODIFICATIONS EXECUTED ON THE PROTOTYPE OF PMSM ROTOR Designed prototype of rotor for PMSM was verified by tests such as no-load test at the generator running, as well as fed by sinusoidal supply and traction power converter Because during the measurement was found that the rotor is susceptible to mechanical vibration, which was due to the large disparity between the length of iron and the stator bore, what at default induction motor is unknown, was built prototype of PMSM used for further research in order to improve its properties A) B) No load characteristics of PMSM at generator runnig 600 1000 800 10000 600 400 540 9000 200 480 8000 420 No load losses (W) Induced voltage (V) Ui0 100 200 300 400 500 600 700 800 900 1000 -200 -400 -600 -800 U1 U2 U3 7000 -1000 C) 360 6000 300 5000 240 4000 180 3000 D) 'P 120 2000 60 1000 f1 0 U0 Ui0 v1 ver.1 10 15 20 U0 Ui0v2 ver.2 25 30 U0 Ui0v3 ver.3 35 40 45 stratyver.1 v1 loss 50 55 60 stratyver.2 v2 loss 65 70 75 80 85 stratyver.3 v3 loss f (Hz) Fig No load test of PMSM at generator running A) No load characteristics and B)-D) comparison of instantaneous value of voltage curve of motor against to modifications at nominal speed: B) Version of Prototype, C) Version after first modification (G rise), D) Version after second (skew) and third (PM size reduction) modification After rotor’s modification was PMSM tested by measuring selected characteristics This correction meant decrease of induced voltage Ui0, and it reduces the ripple After test of rotor’s prototype the rotor was regrinding so that the air gap was increased to mm (the original ATM has G=1 mm, and rotors prototype had G=1.5 mm) 72 in the curve of actual value Ui and also no-load losses (see Fig 4) In order to optimize the parameters of PMSM and thereby reduce losses and increase efficiency of PMSM we made further modifications of the rotor version, namely: x slewing of the rotor laminated sheet about an angle of one slot - in order to reduce the ripple of magnetic flux density - the suppression of harmonics in the curve of magnetic flux density and hence reduce pulsations of voltage and torque , permanent magnet size reduction to decrease of magnet losses - an initial using permanent magnet (27.16 x50x4.3 mm) was divided into four parts (i.e.:13.58 x25x4.3 mm Proposed modification would have reduce of PM losses from 2640 W to 660 W in compliance with calculation, it was confirmed by efficiency measurement x TABLE III SELECTED ELECTRIC PARAMETER OF THE PMSM Ver.1 (before) Torque (Nm) 1200 1100 1000 900 Ver (after modification) 800 700 No load EMF Ui0 (V) 480 436.8232 (for f=67 Hz) 0.8472 Coupled magnetic flux \M (Wb) 0.9339 062 No load losses 'P0 (W) 125 Synchronous inductance Ld (mH) 1.63 2.36 1.9 2.8 Lq (mH) 0.3791 Leakage inductance LV0 (mH) 11.0679 Stator resistance Rs (m: :) 600 500 400 300 200 100 0 20 40 60 80 100 120 140 -100 160 180 Load angle (°) -200 -300 Meas Torque at I=300 A Meas Torque at I=330 A Sines Torque Torque calculated by FEM Reluct Torque 7000 96 6000 95 5000 94 4000 93 3000 92 2000 91 1000 1200 210000 1000 175000 800 140000 600 105000 400 70000 200 35000 90 0 30 60 90 120 Efficiency 150 180 210 240 270 300 Losses 0 330 50 100 Mech torque Input power Current (A) Pp1 (W); Pmech (W) 97 Losses (W) 8000 Tmech (Nm); Us (V) Efficiency (%) Fig Calculated and measured and dependency of the torque on load angle for PMSM 98 150 200 Term voltage Mech.-output power 250 300 350 Voltage -1harm Current (A) 190 96 170 94 150 92 130 90 110 88 90 86 60 70 84 56 800 50 K (%) 98 96 Pm (kW) Us (V); Us1 (V); Tmech (Nm) 210 100 1250 1100 92 88 950 84 800 K (%) Fig Load characteristics of PMSM at f=50 Hz, UDC=680 V 80 76 650 72 500 68 64 350 200 Torque 200 400 Voltage 600 800 U1harm 000 200 efficiency 400 600 rotation speed (min-1) 200 400 Output power 600 800 Efficiency Fig Mechanical characteristics of PMSM UDC=680 V, I=330 A 73 000 200 400 600 82 800 rotational speed (min-1) Because of the limited extent of the contribution, we have chosen only selected experimental results and much more information can be found in details in [1,2,3] Experimentally confirmed obtained parameters of a realized prototype of the PMSM into stator winding pack from ATM are listed in Table IV., which the most significant parameter is the increase of the machine efficiency by 2% V CONCLUSIONS Objective, which led us to a specific analysis of performance of PMSM and investigation of analytical results from the theoretical development and practical implementation, was the feature of the machine found in the type test The pilot realization of a prototype PMSM was built on basis of ATM with power 210 kW, that have stator bore De=230 mm and stator length lFe=650 mm Such ratio De/LFe of the stator bore to the length has proved unsuitable for the construction of PMSM from mechanical point of view and it results in limitations of maximum speed Rotor PMSM has just sheets and magnets and its mechanical natural frequency significantly decreased and shifted to the operating frequency area, this caused vibration and mechanical scrubbing of the rotor This feature led us to use the prototype rotor for the purpose of research and review in order to obtain theoretical knowledge in practical application ATM has rotor composed of sheets with reinforced rotor bars and therefore the mechanical limitations did not occur there The realization of the rotor, but most of all bonding technology for PM on rotor plate requested address range of material and technological issues that significantly affect the resulting behavior of the machine Comprehensive tests of the prototype brought an important knowledge for redesigned construction machinery in question (namely: the choice of the size of NdFeB magnets in relation to the amount of eddy loss, ratio limits the length of the active rotor and stator to the stator bore diameter lFe/De, skew, etc.) ACKNOWLEDGMENT This work was supported by the Slovak Research and Development Agency under the contract No APVV-0530-07 and realization of project “Research on Highly Efficient Electric Propulsion Systems Components of Locomotives and Public Transport Vehicles” No 26220220078, founded by European Regional Development Fund under Operational Programme Research and Development REFERENCES [1] [2] [3] [4] [5] [6] [7] TABLE IV COMPARISON OF PARAMETERS DESIGNED AND IMPLEMENTED THE PERMANENT MAGNET SYNCHRONOUS TRACTION MOTOR FOR PUBLIC TRANSPORT VEHICLES WITH THE DEFAULT PARAMETERS OF ASYNCHRONOUS TRACTION MOTOR [8] Type: ATM210 PMSM160 Nominal voltage Us_conver (V) 425 Umot=475 (Ugen=420) Nominal current Is (A) 332.2 300 Pole pairs 2p Rated input power Pp (kW) 223 171 Rated output power Pmech (kW) 210 163* Shaft torque Tmech (Nm) 1018 1040 Nominal frequency fn (Hz) 66.7 66.7 Rated speed nn (min-1) 1971 2010 Isolation class C B (F) 94 96 Efficiency K (%) Type of permanent magnet NdFeB 42SH (BH)max (kJ/m3) 344 Dimensions W x H x L (mm) 13.3 x 4.3 x 24.8 Mass of PM GPM (kg) 11.55 1056 Number of PM (pc) Max working temperature (°C) 150 * The output power of proposed PMSM was decreased over to ATM because it was decreased temperature class due to used PMs [9] [10] [11] [12] 74 Annual report of project solutions by contract APVV0530-07, per year 2010, archive EVPÚ a.s , January 2011, (in Slovak) Annual report of project solutions by contract APVV0530-07, per year 2009, archive EVPÚ a.s and Slovak Research and Development Agency, January 2010, (in Slovak) Annual report of project solutions by contract APVV0530-07, per year 2008, archive EVPÚ a.s and Slovak Research and Development Agency, January 2009, (in Slovak) Franko, M.: Permanent magnet synchronous motor for traction applications PhD Thesis, Univesity of Zilina, Slovak republic, May 2009, (in Slovak) Kuchta, J.: Some design issues of asynchronous traction motor for locomotives with electric power transmission Monograph, Univesity of Zilina, Slovak republic, EDIS Žilina, 2008, ISBN 978-80-8070-841-2 (in Slovak) Ferková, Ž., Franko, M., Kuchta, J., Rafajdus, P.: Electromagnetic design of ironless permanent magnet synchronous motor, SPEEDAM 2008, International Symposium on Power Electronics, Electrical Drives, Automation and Motion, Ischia, Italy, 2008, June, 11.-13., AFC, p.: 721-726 Franko, M.; Grman, Ľ.; Hrasko, M.; Kuchta, J.; Buday, J.: Experimental Verification of Drive with Segment Slotless Synchronous Motor with Permanent Magnet, IECON 2009, Porto 3-5.11 2009, abstract proceeding p.360 Kuchta, J.; Franko, M.: Advantages and limitations of using a permanent magnet synchronous motor in the traction drive 20 International conference „Current problems in rolling stock“- ProRail 2011“; 21 – 23 September 2011, Žilina, Slovakia, vol II, p.183-191 ISBN 978-80-89276-31-8 (in Slovak) http://www.skd.cz/EN/index.htm Polinder, H.; Hoeijmakers, M.J.: Eddy-current losses in the permanent magnets of a PM machine, Proceedings of the Eighth International Conference on Electrical Machines and Drives, IEE, Cambridge, UK, 1997, pp 138{142 Nipp, E.: Permanent Magnet Motor Drives with Switched Stator Windings Royal Institute of Technology, Stockholm ISSN-1102-0172 Hrabovcová, V.; Rafajdus, P.; Franko, M.; Hudák, P.: Measurements and modeling of electrical machines Book, EDIS Zilina, april 2004, ISBN 80-8070-229-2 (in Slovak) ... 216 .66 16 2.5 13 0 65 54 .17 50 50 32.5 24.8 dimensions lM 4.3 (mm) hM kgm3 kgm1 kgm1 kgm1 kgm1 kgm1 kgm3 kgm1 kgm1 Coefficient of 2.429 .10 -8 1. 627 .10 -8 9.772 .10 -9 4 .16 7 .10 -10 2.726 .10 -10 2. 311 .10 -10 ... 4.49 .10 -11 2. 61. 10 -11 1, 44 .10 -11 PM geometry 25599 22865 17 162 3659 2872 10 24 915 660 PM losses (W) 2638 Quotient of losses to 12 .2% 10 .9% 8.2% 1. 7% 1. 4% 1. 3% 0.5% 0.4% 0.3% nominal power PN= 210 kW... 71 TABLE II THE IMPACT OF A CHANGE OF PM NUMBER TO ROTOR’S LOSSES 2x3 2x4 2x5 x 10 x 12 x 13 10 x 13 10 x 20 10 x 26 Number of PM 67.89 67.89 67.89 27 .16 27 .16 27 .16 13 .58 13 .58 13 .3 PM wM 216 .66