Analysis of Permanent Magnet Synchronous Machine for Integrated StarterAlternatorBooster Applications

2015 International Conference on Electrical Drives and Power Electronics (EDPE) The High Tatras, 21-23 Sept 2015 Analysis of Permanent Magnet Synchronous Machine for Integrated Starter-Alternator-Booster Applications Florin Nicolae Jurca, Mircea Ruba, Claudia Martis Department of Electrical Machines and Drives Technical University of Cluj-Napoca Romania florin.jurca@emd.utcluj.ro, mircea.ruba@emd.utcluj.ro, claudia.martis@emd.utcluj.ro the internal combustion engine for a short period of time (maximum minutes), in situations where additional mechanical energy is necessary (overruns, ramps etc) [1, 2] The ISAB can be connected to a gasoline or diesel engine either directly through crankshaft or indirectly through belt drive, and they are accordingly called the belt-driven starter alternator (BAS) and normal ISAB, respectively The permanent synchronous machine with outer rotor is an innovative solution of direct connection to the internal combustion engine in both cases in the context of minimal mechanical losses Comparative whit other types of electrical machines, the permanent magnet (PM) synchronous machines have some important advantages like high power density, high efficiency and the possibility to work in high overload [3] The present paper approaches the design and analysis of a special topology of interior permanent magnet synchronous machine (IPMSM) suited for automotive application, shown in Fig.1 This machine is characterized by anisotropic rotor, that is benefit when flux-weakening operations are required The motor torque is due to two components: one is due to the PM flux and the other to the rotor saliency In addition, the anisotropic rotor is advantageous in order to detect the rotor position without using a position sensor [3] Abstract—In the last decade due to their high efficiency and reliability, permanent magnet synchronous machine are widely used in automotive applications There are two main reasons for this trend: the reduction of the fuel consumption and the increase of the travel comfort In this study we consider the approaches of electromagnetic design of a special topology of permanent synchronous machine (radial flux machine with outer rotor) suited for automotive applications The study design requires some analytical analysis, followed by a numerical one in order to attain the performances of the proposed machine in all three cases (starter-alternator-booster) A thermal analysis is required in order to determine the thermal requirements for the automotive applications Keywords— permanent magnet motor; electromechanical system; hybrid vehicule I INTRODUCTION Current research efforts related to electric cars have problems mainly related to the accumulation of electricity In this context (low autonomy, lack of fast charging stations) the use of this type of machine is limited to urban trails Initially considered as a transition between conventional vehicles and the electric ones, the hybrid vehicles remain an alternative that is gaining more ground by combining the advantages of both types of vehicles Of the two types of series and parallel hybrid vehicles, alternative series provides a simpler connection between the two engines and transmission powertrain Passing to the present path of development of hybrid vehicles involves increasing the role in the operation of the electrical machines by increase its power and "responsibility" (starter-alternator-booster) The first steps were be made by using a single electric machine as a generator (alternator) and motor (starter) for starting the internal combustion engine, but for a hybrid car a second electrical machine is used for the electric propulsion The simplification of this structure involves the use of a single electric machine incorporating three operating modes: starteralternator-booster (ISAB) In this case ISAB will initially be able to start internal combustion engine, then when turned on will switch to a generator and will supply the electricity consumers and the electricity storage system Due to the control strategies used, electrical machine is capable to move quickly from generator to motor (booster) and back to help Fig.1 Structure of the ISAB: 42-slot 14 pole IPM machine 978-1-4673-7376-0/15/$31.00 ©2015 IEEE EDPE 2015 272 2015 International Conference on Electrical Drives and Power Electronics (EDPE) The High Tatras, 21-23 Sept 2015 For no-load condition, the air-gap magnetic flux density distribution is depicted in Fig 4, giving an average value of 0.72 T A preliminary design procedure will be performed using SPEED program and the results will be implemented in a FEM based software in order to analyze the performances of the machine: magnetic field density, induced emf, torque and current After that a thermal analysis is required because the thermal behavior can drastically influence the machine's performances Thus a special attention should be paid on the heat transfer within the active and non-active parts of the machine II PRELIMINARY DESIGN The initial phase of the design was conducted using SPEED software The SPEED software allows very fast performance estimation of the electrical machine The software is mainly based on analytical computations The motor structures were refined using ranging analysis that helps to determine the influence of geometrical and electrical parameters on the motor performance In order to improve the electrical machines performances, several winding topologies will be analyzed The output performances of the studied motor are: P – (kW); rated voltage Un – 72 (V); rated speed nn – 500 rpm; pole pair number p – 14 The rotor has three flux barriers per pole The dimensions of the PMs are equal to x 10 mm, 2.5 x 16 mm, x 18 mm The obtained main dimensions and the results for the operation at rated point are shown in Table1 Fig Map of flux density TABLE I GEOMETRIC AND RESULTS PARAMETERS FOR THE DESIGED MACHINE Stator outer diameter [m] 0.210 Rotor outer diameter [m] 0.150 Shaft diameter 0.110 Stack length [m] 0.150 Slot area [mm2] 89.3 Air-gap [m] 0.0005 Slot number 42 Slot depth [m] 0.014 Tooth width [m] 0.006 Back iron height [m] 0.0147 Pole number 14 Air-gap flux density [T] Rates speed [rot/min] 500 Phase emf [V] 42 Rated current [A] 50 Current density [A/ mm2] 15.75 Power factor [%] 0.89 Efficiency [%] 90 Torque [N*m] 155 PM residual flux density [T] 1.42 Fig.3 Flux lines distribution 1.5 III MAGNETIC FIELD ANALYSIS 0.5 B [T] The finite element method (FEM) is a powerful tool for the design of the electrical machines and others electromagnetic devices FEM is a simple, robust and efficient widely used method of obtaining a numerical approximate solution for a given mathematical model of the machine This analysis has been carried out using Flux2D software The magnetic flux density map in the cross-section of the machine is presented in Fig.2 and the flux lines distribution in Fig -0.5 -1 -1.5 40 80 120 160 200 rotor angle [o] 240 Fig Air-gap magnetic flux density EDPE 2015 273 280 320 360 2015 International Conference on Electrical Drives and Power Electronics (EDPE) The High Tatras, 21-23 Sept 2015 The regime operation in load condition will be simulated in order to obtain de torque value at rated speed 190 180 T orque [N *m ] 170 160 150 140 130 120 110 100 0.005 0.01 0.015 Time [s] 0.02 0.025 0.03 Fig Torque variation in time In order to evaluate the efficiency of the machine in starter an alternator mode the iron losses was computed for obtained the efficiency map of ISAB The machine efficiency for over the entire torque (current)/speed of starter and alternator regime, considering the copper losses (80oC) can be seen in Fig.6 and Fig.7 From this efficiencies map, the machine losses can be extracted and used as input data for a thermal simulation of the machine 2 90 81 180 86 71 88 76 87 85 66 67 140 84 07 62 82 48 57 30 48 77 76 74 53 33 72 94 29 35 76 19 68 66 64 9 05 160 Fig.8 Skewing the IPMSM: flux density repartition The geometry of the IPMSM 42/14 was drawn in 2D and after that we have considered an angle of incline of slot (360/42) The effect on rotor sheets incline, as well as the core flux density repartition, is shows in Fig Now, one can verify the torque repartition for the skewed machine, Fig.9 The torque varies between 153 and 158, meaning that the torque ripple corresponds to 3.2% This is an important decrease of torque ripple content This gain can be decisive while preparing the control of the IPMSM 160 40 76 90 120 86 93 150 200 250 300 Speed [rpm] 400 IPMSM IPMSM-skewed 20 90 43 81 350 80 40 95 20 95 93 61 92 02 86 100 60 95 95 20 61 90.43 81 100 Torque [N*m] 43 76 84 92 90 71 87 52 7 89 66 8082 84 85 88 60 92 28 93.619 81 80 88 100 81 140 71 7 5.9 76 3 7 3 48 80 8 57 84 62 85 6 67 87 71 T o rq u e [N *m ] 120 450 500 0.005 0.01 0.015 time [s] 0.02 0.025 0.03 Fig IPMSM, torque ripples: with or without skewing effect Fig.6 Starter efficiency map 88 81 76 9 1 86 88 92 54 9 93 C u r r e n t [A ] 87 33 1500 2000 2500 86.26 19 86 95 24 71 76 87 65 24 81 95 85 56 67 86 95 71 93 86 261 24 For the proposed machine Flux program (Skew module) was used in order to observe the behavior of the machine in all operating regimes (starter-alternator-booster) Thus, we accomplished a simulation scenario in which the proposed machine is analyzed in the three considered operating regimes In order to this the circuit presented in Fig 10 was implemented 84.8714 29 43 65 1000 21 85 5667 476 92 10 93 43 38 87 8 93.21 91 82 91 519 92 91 1.1.82 28 36 9 15 90.4333 3 9 1 20 33 25 90 43 30 68647.8 81 48 3.1 47 1 69 38393.7 19 48279.6 48 487656.9 18 6 9 29 31 8.1 69 38393.7 8891.0 69 4 29 35 3000 3500 Speed [rpn] 89 04 88 34 29 89 81 4000 76 89 04 4500 5000 29 5500 6000 Fig.7 Alternator efficiency map Because this structure is proposes to automotive application, we are trying to find a solution to reduce the torque ripples Theoretically, skewing the stator and rotor core might produce very smooth torque wave For that, we have analyzed the proposed machine with the Flux/Skewed computation module In this case it is easier to make rotor in Skewed technology Fig 10 The circuit model of ISAB regime EDPE 2015 274 2015 International Conference on Electrical Drives and Power Electronics (EDPE) loss, the iron loss and the mechanical loss The thermal analysis for the proposed machines was carried out using dedicated software Motor-CAD After implementing the geometry, the winding, the materials, iron and joule losses, the cooling condition and torque profile depending on time are defined In our case we consider the force cooling using water jacket Usually the starter procedure lasts about second, so in Motor-CAD we have set it to 10 second in order to obtain relevant results about the obtained temperature in the machine in starter mode For starter mode we have considered 15 second in condition of variable load, and for booster we set 10 second The analysis was made for 40 duty cycles Highest temperatures were obtained the winding and stator back iron (91 C0),while in the permanent magnet the temperature is around 92 C0 The behavior of the machine in all three regimes is presented (starter-alternator-booster) in Fig 11 (torque profile), Fig 12, 13 (phase voltage and current on the machine), Fig 14 (dc voltage and current obtained on the load) 160 STARTER 140 120 BOOSTER Torque [N*m] 100 80 60 40 20 ALTERNATOR -20 -40 0.2 0.4 0.6 0.8 time [s] 1.2 1.4 1.6 1.8 The High Tatras, 21-23 Sept 2015 Fig 11 ISAB torque profile 60 phase voltage [V] 40 20 -20 -40 -60 0.2 0.4 0.6 0.8 time [s] 1.2 1.4 1.6 1.8 Fig.12 Three phase voltage obtained in ISAB regime 60 phase current [A] 40 20 -20 -40 a) radial view -60 0.2 0.4 0.6 0.8 time [s] 1.2 1.4 1.6 1.8 Fig.13 Three phase current obtained in ISAB regime 100 DC Voltage 90 D C v o lta g e [V ]/ D C c u rre nt [A] 80 70 60 50 DC Current 40 30 20 10 -10 0.2 0.4 0.6 0.8 time [s] 1.2 1.4 1.6 1.8 Fig.14 DC voltage and current obtained in alternator regime IV THERMAL ANALYSIS In automotive applications with combustion engine, the thermal behavior can drastically influence the machine's performances Thus a special attention should be paid on the heat transfer within the active and non-active parts of the machine The heat sources on the machine are: the cooper b) axial view Fig.15 IPMS temperature values EDPE 2015 275 2015 International Conference on Electrical Drives and Power Electronics (EDPE) [3] [4] Fig 16 Duty cycle configuration [5] [6] V CONCLUSIONS In this paper a structure of permanent magnet synchronous machine with outer rotor, suitable for automotive application (integrated starter-alternator-booster) is presented The preliminary design model of the machine was developed followed by a simulation with finite element method in Flux 2D for ISAB regime The results obtained here provide valuable information on the machine's behavior in all three operating mode The thermal analysis for the proposed machines was carried out in order to evaluate the thermal stress of the ISAB MARTIS Claudia: graduated Electrical Engineering and received the PhD degree in Electrical Engineering from Technical University of Cluj-Napoca, Romania, in 1990 and 2001 respectively Since 1996 she is member of the teaching staff of the Faculty of Electrical Engineering at Technical University of Cluj-Napoca She is currently Professor with the Department of Electrical Machines and Drives of the same university and her research is focused on electrical machines and drives design, modeling, analysis and testing for automotive, renewable energy-based and industrial applications Mircea Ruba He received B.Sc., M.Sc and Ph.D degree from Technical University of Cluj in electrical engineering in 2007, 2008, respectively in 2010 He is a researcher working in the field of switched reluctance machines The results of his researches were published in more than 30 papers in journals and international conference proceedings ACKNOWLEDGMENT This work was supported by the: 1.Research-Development-Innovation Internal Projects of the Technical University of Cluj-Napoca Strategic research topics for young teams: DESIGN DESIGN, ANALYSIS AND CONTROL OF PERMANENT MAGNET SYNCHRONOUS MACHINES AS STARTER-ALTERNATOR-BOOSTER UNIT FOR HYBRID ELECTRIC VEHICLES 2.Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI) under the AUTOMOTIVE LOW-NOISE ELECTRICAL MACHINES AND DRIVES OPTIMAL DESIGN AND DEVELOPMENT (ALNEMAD) Joint Applied Research Project (PCCA) in the frame of "Partnerships" projects (PN II – National Plan for Research, Development and Innovation) DEsign, Modellling and TESTing tools for Electrical Vehicles (DEMOTEST), in the frame of FP7 IAPP Marie Curie Actions REFERENCES [2] integrated starter-alternator application” Industry applications society annual meeting (IAS), IEEE 1-8 (2008) M Barcaro, A Alberti, L.Faggion, M Sgarbossa, Dai Pr’e M, N Binachi, “Expereimental tests on a 12-slot 8-pole integrated starteralternator” Proceedings of the 2008 International Conference on Electrical Machines 1-6 Mirahki, H ; Moallem, M " Design improvement of Interior Permanent Magnet synchronous machine for Integrated Starter Alternator application ", Electric Machines & Drives Conference (IEMDC), 2013 IEEE International DOI: 10.1109/IEMDC.2013.6556279 Publication Year: 2013 , Page(s): 382 - 385 Cited by: Papers (1) IEEE Conference Publications M.Ruba, D.Fodorean : Analysis of Fault-Tolerant Multiphase Power Converter for a Nine-Phase Permanent Magnet, IEEE Trans On Industrial Applications, Vol 48, no 6, pp 2092-2101, ISSN: 00939994, 2012 F.Jurca, R.P Hangiu, C MarĠiú -"Design and performances analysis of an Integrated Starter-Alternator for Hybrid Electric Vehicles" Conference on Interdisciplinary Research in Engineering Steps towards Breakthrough Innovation for Sustainable Development, INTERIN, ClujNapoca 2013, pp 453-460, ISBN: 978-3-03785-785-4 JURCA Nicolae Florin: graduated Electrical Engineering and received the PhD degree in Electrical Engineering from Technical University of ClujNapoca, Romania, in 2004 and 2009 respectively Since 2007 he is member of the teaching staff of the Faculty of Electrical Engineering at Technical University of Cluj-Napoca He is currently Lecturer with the Department of Electrical Machines and Drives of the same university and him research is focused on electrical machines and drives design, modeling, analysis and testing for automotive, renewable energy-based and industrial applications Fig 17 Thermal analysis of the proposed machine, with Motor-CAD: temperatures variation on duty cycle's [1] The High Tatras, 21-23 Sept 2015 W Cai, “Comparison and review of electrical machine for integrate starter-alternator applications” Industry applications society annual meeting (IAS), IEEE 386-393 (2004) M Barcaro, A Alberti, L.Faggion, M Sgarbossa, Dai Pr’e M, N Binachi, S Bologni, “IPM machine drive design and tests for an EDPE 2015 276 ... 84.8714 29 43 65 1000 21 85 5667 476 92 10 93 43 38 87 8 93 .21 91 82 91 519 92 91 1.1. 82 28 36 9 15 90.4333 3 9 1 20 33 25 90 43 30 68647.8 81 48 3.1 47 1 69 38393.7 19 4 827 9.6 48 487656.9 18 6 9 29 ... 400 IPMSM IPMSM-skewed 20 90 43 81 350 80 40 95 20 95 93 61 92 02 86 100 60 95 95 20 61 90.43 81 100 Torque [N*m] 43 76 84 92 90 71 87 52 7 89 66 80 82 84 85 88 60 92 28 93.619 81 80 88 100 81... 120 BOOSTER Torque [N*m] 100 80 60 40 20 ALTERNATOR -20 -40 0 .2 0.4 0.6 0.8 time [s] 1 .2 1.4 1.6 1.8 The High Tatras, 21 -23 Sept 20 15 Fig 11 ISAB torque profile 60 phase voltage [V] 40 20 -20