Electromagnetic simulation of electric motors for automotive applications

Transcription

1 Electromagnetic simulation of electric motors for automotive applications Adrian Scott Market Development Manager Low Frequency Applications

2 Agenda Quick introduction to CST EMS for LF simulation and applications Short summary of motors in automotive applications Typical motor design parameters Simulation example of a PMSM model set up and useful design parameter extraction Other motor examples : Induction and reluctance motors Outlook CST EMS 2016

3 CST EM STUDIO Solvers Electrostatics Frequency Domain Stationary Currents Magnetostatics Time Domain

4 Traction motor candidates for HEV/EVs Rotating machines Synchronous Asynchronous PMSM (Brushless DC) Externally excited (ESM) Reluctance IM Switched Reluctance (SRM) Variable Reluctance (VRSM)

5 Typical synchronous motor parameters Requirement Open Circuit MMF Characteristic Torque versus torque angle Torque optimization Cogging torque Lq/Ld Extraction Iron loss calculation Permanent magnet demagnetization Flux weakening capability Goal Parameterization V versus Flux Parameterization Maximize Minimize - vibration Equivalent circuit Efficiency Short circuit risk Wide range of operating speed

6 Electrical machine features 2D Transient and Magnetostatic

7 Key features : D LT Motion solver 2. Permanent magnet transformation 3. Coil grouping 4. State-Space (Ms) 5. Transient Inductance monitors (LT) + Back EMF (LT) 6. Impedance Matrix (LF) 7. Core Loss models (LT)

8 Iron Loss Calculation Methods

9 Conceptual example PMSM Optimization

10 Permanent Magnet Synchronous Motor Stator consisting of three-phase rotating field winding system, non-linear steel Rotor consisting of Permanent magnets Air barriers for flux diversion

11 Coil Grouping / Colouring Multi-phase winding/coil systems Voltage and/or current groups Reduced inductance matrix Summation of coils inductances Terminals i.e. single or 3-phase systems... Colouring helps to ensure correct coil definition

12 Permanent magnet definition

13 Air-Gap Definition (rotional)

14 Stator and Rotor steel M19 BH Data

15 Mesh with local mesh properties

16 PMSM optimization Average torque and torque ripple (check also cogging torque?) Permanent magnet radial position, angle between magnets, magnet lengths, barrier geometry Motivation : difficult to derive analytical expressions due to non-linear effects e.g. Barrier shape, proximity to rotor surface Conflict of interests : maximum torque, reduced ripple!

17 Steady state torque and ripple Minimize Maximize

18 Rotor permanent magnets and barriers

19 Average Torque

20 Torque ripple

21 Sum of all goals

22 Initial and Optimized Steady State Torque

23 Steady-State torque

24 Cogging torque (stator open circuit)

25 Optimized PMSM geometry

26 B-Field (Abs) versus time

27 Core losses in Stator and Rotor

28 Incremental Inductance versus time

29 Back-EMF results

30 Back EMF vs. Speed (Frequency)

31 Other motor types

32 Induction motor performance Performance characteristic Torque vs. Speed vs. Frequency Squirrel Cage Type 4 Pole, 400 Hz 3-Phase Stator Winding (AC Supply) Synchronous speed proportional to applied frequency Rotor slips behind synchronous field Torque, Nm Hz Standstill Speed, rev/min rpm S = 1 Slip S = 0 Constant Voltage/frequency (V/f) control scheme for induction motors

33 Induction motor B-Field

34 Acceleration CPU Acceleration Pyhsical cores/multi-threading Distributing Computing Parametric/optimisation Induction motor simulation Single simulation Slip_T_max) Total time 1 Thread: 9m : 23s Total time 4 Threads: 5m : 15s Acceleration: 1.8

35 Switched Reluctance Machine

36 Salient Pole Synchronous Motor Salient pole rotor with DC excitation 4 Pole, 50 Hz, 3-Phase Stator Winding (AC Supply) Synchronous speed proportional to FREQUENCY / Number of magnetic poles

37 Salient Pole Synchronous Motor Open circuit (no-load) test Rotor speed = synchronous speed Stator RMS voltage (phase A) versus field current, I_field

38 Multiple rotations : magnetic gear

39 Shaded-Pole Induction Motor (SPIM) 2D Transient motion Eddy currents in cage and shaded-pole rings, non-linear magnetic materials Standard Torque-Speed curves

40 New features in EMS 2016

41 Key features : Voltage driven coils in 2D (LT) 2. Zero NET current constraint in LT 2D in magnets 3. Permanent magnet demagnetization Monitor (LT) 4. Periodicity LT (subvolume) 5. Equation of motion (LT) 6. Linear motion (LT) 7. Additional core loss models 8. 2D Forces, 3D LT Force density (Ms, LT) 9. H-Field calculation for (LF EQS) 10. Moment calculation (Ms)

42 Motor Control PMSM : Pulse Width Modulation New voltage sources in 2D LT Transient User-Defined PWM stator voltage signals PWM Signals from inverter unit

43 Summary New features in EMS 2015 for the simulation of electrical machines Efficient 2D simulations Simulation example of a PMSM model set up and useful design parameter extraction The possibilities to optimize design parameters of a PMSM was shown Same principles can also be applied to induction and reluctance motors Outlook CST EMS 2016