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

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

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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

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CST EM STUDIO® Solvers

Electrostatics

Stationary Currents

Magnetostatics Time Domain

Frequency Domain

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Rotating machines

Synchronous

PMSM (Brushless DC)

Externally excited (ESM)

Reluctance

Switched Reluctance

(SRM)

Variable Reluctance

(VRSM)

Asynchronous

IM

Traction motor candidates for HEV/EVs

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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

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Electrical machine features 2D Transient and Magnetostatic

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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

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Iron Loss Calculation Methods

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Conceptual example PMSM Optimization

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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

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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

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Permanent magnet definition

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Air-Gap Definition (rotional)

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Stator and Rotor steel M19 BH Data

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Mesh with local mesh properties

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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!

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Steady state torque and ripple M

inim

ize

Max

imiz

e

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Rotor permanent magnets and barriers

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Average Torque

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Torque ripple

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Sum of all goals

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Initial and Optimized Steady State Torque

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Steady-State torque

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Cogging torque (stator open circuit)

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Optimized PMSM geometry

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B-Field (Abs) versus time

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Core losses in Stator and Rotor

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Incremental Inductance versus time

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Back-EMF results

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Back EMF vs. Speed (Frequency)

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Other motor types

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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

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Induction motor B-Field

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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

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Switched Reluctance Machine

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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

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

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

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Multiple rotations : magnetic gear

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Shaded-Pole Induction Motor (SPIM)

2D Transient motion

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

Standard Torque-Speed curves

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New features in EMS 2016

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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

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

Motor Control

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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