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


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

Agenda


CST EM STUDIO® Solvers

Electrostatics

Stationary Currents

Magnetostatics Time Domain

Frequency Domain


Rotating machines

Synchronous

PMSM (Brushless DC)

Externally excited (ESM)

Reluctance

Switched Reluctance

(SRM)

Variable Reluctance

(VRSM)

Asynchronous

IM

Traction motor candidates for HEV/EVs


Typical synchronous motor parameters

Requirement Goal Open Circuit MMF Characteristic Parameterization V versus Flux

Torque versus torque angle Parameterization

Torque optimization Maximize

Cogging torque Minimize - vibration

Lq/Ld Extraction Equivalent circuit

Iron loss calculation Efficiency

Permanent magnet demagnetization Short circuit risk

Flux weakening capability Wide range of operating speed


Electrical machine features 2D Transient and Magnetostatic


1. 2D 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)

Key features : 2015


Iron Loss Calculation Methods


Conceptual example PMSM Optimization


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


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

Coil Grouping / Colouring


Permanent magnet definition


Air-Gap Definition (rotional)


Stator and Rotor steel M19 BH Data


Mesh with local mesh properties


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!


Steady state torque and ripple M

inim

ize

Max

imiz

e


Rotor permanent magnets and barriers


Average Torque


Torque ripple


Sum of all goals


Initial and Optimized Steady State Torque


Steady-State torque


Cogging torque (stator open circuit)


Optimized PMSM geometry


B-Field (Abs) versus time


Core losses in Stator and Rotor


Incremental Inductance versus time


Back-EMF results


Back EMF vs. Speed (Frequency)


Other motor types


Induction motor performance Performance characteristic Torque

vs. Speed vs. Frequency

12000 rpm

Torq

ue,

Nm

Speed, rev/min Slip

Standstill S = 1 S = 0

Constant Voltage/frequency (V/f) control scheme for induction motors

100 – 400 Hz Squirrel Cage Type 4 Pole, 400 Hz 3-Phase Stator Winding (AC Supply) Synchronous speed proportional to

applied frequency Rotor “slips” behind synchronous

field


Induction motor B-Field


CPU Acceleration Pyhsical cores/multi-threading

Distributing Computing Parametric/optimisation

Induction motor simulation Single simulation (e.g. @ Slip_T_max) Total time 1 Thread: 9m : 23s Total time 4 Threads: 5m : 15s Acceleration: 1.8

Acceleration


Switched Reluctance Machine


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


Salient Pole Synchronous Motor Open circuit (no-load) test

Rotor speed = synchronous speed Stator RMS voltage (phase A) versus field current, I_field


Multiple rotations : magnetic gear


Shaded-Pole Induction Motor (SPIM)

2D Transient motion

Eddy currents in cage and shaded-pole rings, non-linear magnetic materials

Standard Torque-Speed curves


New features in EMS 2016


1. 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)

Key features : 2016


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

Motor Control


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

Summary

electromagnetic simulation of electric motors for ... – computer ... electromagnetic simulation of...

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