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1 Bi-directional Automatic Electromagnetic-Thermal Coupling for HEV/EV Traction Motor Design Using Maxwell and ANSYS Mechanical Peng Yuan Eric Lin Zed (Zhangjun) Tang ANSYS, Inc ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary

2 Abstract Electromagnetic and thermal designs are both important and highly coupled when designing a traction motor used in HEV/EV applications Electromagnetic losses affect temperature and temperature change will in turn change the electromagnetic material properties Multiple iterations are needed in order to achieve high accuracy Scripting is needed to automate the process 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

3 Contents Objectives Requirement and Strategy Solution Setups Electromagnetic Field FEA Setup Thermal Simulation Setup Coupled Thermal Feedback Scripting for Automatic Process Case Studies and Working Example Conclusions Appendix 2010 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary

4 Objectives Case #1: What is the final temperature distribution in a motor? At fixed load 0 Case #2: How long does it take to reach the final temperature? At fixed load ( C ) 100 P A R Cycle # Case #3: What is the temperature profile when the motor is running for hours at various operating conditions? At various loads like a typical drive cycle ASM_2.N[rpm] Manhattan Cycle Ansoft LLC Measured Rotor Speed induction_machine_dc_buscap Curve Info ASM_2.N TR Time [s] 2010 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary

5 Requirement and Strategy Requirement ANSYS Maxwell V13.0 or higher ANSYS Mechanical R12.1 or higher Strategy Ideally CFD simulation is needed for traction motor thermal analysis, since this type of motor uses forced air or liquid id cooling, plus it has moving parts As a first approximation, convection heat transfer can be replaced by specifying heat transfer coefficients (HTCs). This approach is taken by ANSYS Mechanical to greatly reduce simulation time Heat transfer coefficients (HTCs) need to be known from either experiments or previous collection of CFD results 2010 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary

6 Electromagnetic FEA Setup - Maxwell Set up by RMxprt automatically, including geometry, material properties, boundary conditions, excitations, mesh Parameterize: rotational speed, simulation time step/stop time, excitation current/current angle, temperature-dependant material properties (copper conductivity) PM material property change is not included in this example, but its BH curve and conductivity can also be implemented as temperature dependent 2010 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary

7 Thermal Simulation Setup ANSYS Mechanical Geometry is generated from RMxprt/Maxwell Geometry can also come from 3D CAD and then sent to Maxwell and ANSYS Mechanical for simultaneous processing End-turns are separated from in-lamination coppers, because they have different temperatures Slot geometry subtracts conductors to generate varnish material, which is very important for heat transfer Boundary conditions with HTCs are applied 2010 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary

8 Coupled Thermal Feedback ANSYS Mechanical calculates temperature for components that have temperaturedependant electromagnetic properties and feeds back to Maxwell Maxwell design with new temperature is executed to export a new sets of losses and are then mapped to ANSYS Mechanical This process continues until convergence criteria or other requirements are met 2010 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary

9 Scripting for Automatic Process JavaScript is used to manage the overall communication between Maxwell and ANSYS Mechanical JavaScript is called directly in ANSYS Workbench environment VBScript is used to run Maxwell APDL (ANSYS Parametric Design Language) is used in Mechanical simulation to scope out temperature information and feed back to Maxwell 2010 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary

10 Case Study #1 Description Goal: what is the final temperature distribution in a motor? Maxwell Transient solver with fixed motor operating condition ( for example, worst case speed, current, current angle) ANSYS Mechanical Static Thermal solver Multiple iterations are needed to accurately account tfor the material properties change 2010 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary

11 Case Study #1 Procedure Run JavaScript from ANSYS Mechanical Update material properties based on temperature No JavaScript calls VBScript to run Maxwell, exports loss results and close Maxwell JavaScript maps Maxwell loss data to ANSYS Mechanical and run thermal simulation Enough Iterations Or Temperature Stabilized? APDL scopes temperature info and sends to JavaScript Yes 2010 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary End

12 Case Study #1 Sample Result ( C ) 200 PART PART PART Cycle # 2010 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary

13 Case Study #2 Description Goal: how long does it take to reach the final temperature? Maxwell Transient solver with fixed motor operating condition (for example, worst case speed, current, current angle) ANSYS Mechanical Transient Thermal solver Multiple iterations are needed to accurately account tfor the material properties change 2010 ANSYS, Inc. All rights reserved. 13 ANSYS, Inc. Proprietary

14 Case Study #2 Procedure Run JavaScript from ANSYS Mechanical Update material properties based on temperature No JavaScript calls VBScript to run Maxwell, exports loss results and close Maxwell JavaScript maps Maxwell loss data to ANSYS Mechanical and run thermal simulation Enough Time Steps Or Temperature Stabilized? APDL scopes temperature info and sends to JavaScript, record thermal transient info Yes 2010 ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary End

15 Case Study #2 Sample Result Time Temp1 Temp2 Temp3 Temp3 Temp4 Temp5 Temp6 Temp7 Temp8 Temp9 Temp10 Temp ANSYS, Inc. All rights reserved. 15 ANSYS, Inc. Proprietary

16 Case Study #3 Description Goal: what is the temperature profile when the motor is running for hours at various operating conditions? Maxwell Transient solver with various motor operating conditions (speed, current, current angle) ANSYS Mechanical Static Thermal solver Multiple l steps are needed d to account for the change of motor operating conditions 2010 ANSYS, Inc. All rights reserved. 16 ANSYS, Inc. Proprietary

17 Case Study #3 Procedure Run JavaScript from ANSYS Mechanical Update material properties based on temperature, load next motor condition No JavaScript calls VBScript to run Maxwell, exports loss results and close Maxwell JavaScript maps Maxwell loss data to ANSYS Mechanical and run thermal simulation Enough Time Steps APDL scopes temperature info and sends to JavaScript, record thermal transient info Yes 2010 ANSYS, Inc. All rights reserved. 17 ANSYS, Inc. Proprietary End

18 Case Study #3 Sample Result 2010 ANSYS, Inc. All rights reserved. 18 ANSYS, Inc. Proprietary

19 Working Example Maxwell2D Transient design ANSYS Mechanical 3D Transient Thermal simulation Start the automatic process by calling JavaScript in ANSYS Workbench 2010 ANSYS, Inc. All rights reserved. 19 ANSYS, Inc. Proprietary

20 Conclusions Highly coupled electromagnetic/thermal design is needed for high performance HEV/EV motor design ANSYS provides both industry-leading electromagnetic and thermal solvers ANSYS Workbench environment offers an integrated design environment for such multi- physics application ANSYS flexibly scripting capability makes it possible to automate complex procedures 2010 ANSYS, Inc. All rights reserved. 20 ANSYS, Inc. Proprietary

21 Appendix Maxwell and ANSYS Mechanical projects, instructions and documentations for scripts can be downloaded from the following link: ftp://ftp.ansoft.com/download/_zt/twowayco uplingtransient.zip Unzip the file and store all files under C:/TwoWayCouplingTransient folder in order for it to work without any modification Change ANSYS Mechanical Units to be Metric (mm, kg, N, s, ) 2010 ANSYS, Inc. All rights reserved. 21 ANSYS, Inc. Proprietary