Cobham Technical Services

Transcription

The most important thing we build is trust
Cobham Technical Services
Vector Fields Software
Modelling permanent magnet (de-)magnetisation and soft
iron hysteresis within an FEA environment
Contents
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Introduction to Vector Fields Software
Magnetisation & de-magnetisation in permanent
magnets
– Permanent magnet DC machines
– De-magnetisation under fault conditions in a PM machine
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Ferromagnetic hysteresis
– Hysteresis brake
– Electric Steering motors
– Hysteresis motor
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COMMERCIAL IN COFIDENCE
November 13, 2009
Cobham Technical Services – Vector Fields Software
Vector Fields Software provides
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Founded at Oxford England in 1984 by former employees
of the Rutherford Appleton Laboratory
Acquired by Cobham plc in 2005
Name changed in May 2009
SOFTWARE
SUPPORT
for High Frequency Engineering
TRAINING
CONSULTANCY
PARTNERSHIP FOR R&D
for Low frequency Engineering
November 13, 2009
CONCERTO suite
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High Frequency
Electromagnetics
– FDTD Methods
• 3d Microwave analysis
• Antennas, waveguides, filters
• Allows solution to larger problems
• Thermal analysis also available
– Method of Moments
• Discretise material surfaces
• RCS, antenna placement
– Finite Element Analysis Solver
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November 13, 2009
OPERA suite
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OPERA-2d
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OPERA-3d
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Statics and time varying fields
Stress and thermal analysis
Rotary & linear motion analysis
(de-)magnetisation & hysteresis
Lossy-dielectrics
Space charge
Optimisation
Electrical Machines environment
TOSCA : static analysis
ELEKTRA : time varying fields
CARMEN : rotating and linear machines and actuators
SCALA : space charge analysis
TEMPO: thermal analysis
DEMAG: (de-)magnetisation solver
QUENCH: quench in Superconducting magnets
SOPRANO: wave propagation problems
Optimisation
November 13, 2009
The (De-)magnetisation Solver
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Transient Magnetisation
Analysis
– Developed specifically to model
the magnetisation process in
hard magnetic materials
– Uses ‘virgin’ BH curve for
magnetisation and ‘demag’
curves as field decreases
– Inclusion of temperature effects
either as a
• simple, single temperature
model
OR
• distributed temperature model
in coupled
electromagnetic/thermal
simulations
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November 13, 2009
Typical Appliance motor
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Magnet Inserts in Steel Ring
Magnetize in a solenoid using a magnetic
core
Transient solver, incl. eddy current effects
Use of the true magnet characteristic in the
‘application device’(e.g. electric motor)
Computation of de-magnetisation effects
arising during operation due to eg. reverse
armature currents
November 13, 2009
Magnet ring during magnetisation pulse
Note initial flux exclusion from conducting cylinder
Results courtesy of Magnequench
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November 13, 2009
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November 13, 2009
Complete machine - no armature reaction
Radial Field in the
Airgap
4000
3000
2000
Gauss
1000
0
-1000
-2000
-3000
-4000
0
45
90
135
180
225
270
315
360
Degrees
Measurement
Model
Results courtesy of Magnequench
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November 13, 2009
Application in magnetizing of PMDC magnets
Steel magnetizing fixture in
uniform field
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Applied flux density as a
function of time
November 13, 2009
Remanent field strength after magnetizing
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November 13, 2009
Behaviour during operation
Air-gap flux density during
operation
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Minimum values of flux density
in magnets
November 13, 2009
Modelling Magnetising Fixtures in OPERA-3D
Magnetising fixtures may exhibit some important
three-dimensional effects, due to end windings
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November 13, 2009
Demagnetisation ‘in service’
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Polynomial ‘demag curve’ representation for hard rare-earth magnets
Look-up table more appropriate for alnico and ferrite materials, where
finding coefficients for the quadratic becomes difficult.
Recoil line slope user-specified
November 13, 2009
Demagnetisation ‘in service’
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PM Generator
– Run on Open Circuit
– Impose a sudden short circuit and observe demagnetisation
– Clear fault
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November 13, 2009
Demagnetisation in ‘Service’
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Minimum Flux density level reached in magnet during open
circuit and short circuit event
November 13, 2009
Short Circuit Currents & Voltages
– Phase Voltages and Currents before, during and after 3-phase
short circuit
– Observe reduced post-fault open circuit voltage, due to PM
demagnetisation
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November 13, 2009
Treatment of hysteresis in soft
magnetic materials
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November 13, 2009
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November 13, 2009
Treatment of hysteresis in soft magnetic
materials
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The magnetic behaviour is considered as a trajectory B(H)
The trajectory is based on a measured major symmetric loop
that is supplied by the user.
The data may be obtained from in-house measurements or
published data-sheets, and are imported as standard input
tables.
– From the data, the method uses the turning points of the B(H)
trajectory to predict the behaviour of arbitrary minor hysteresis
loops.
The method is practical because it:
• Makes only realistic demands on the user for material data
• Provides a good approximation to the true physical behaviour
• Does not require large computational resources
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November 13, 2009
Flux Distribution in Hysteresis Brake
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November 13, 2009
Eddy Current Loss (Brake at 600 rpm)
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November 13, 2009
Instantaneous Hysteresis Loss
(brake at 600rpm)
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November 13, 2009
Hysteresis Brake Figures
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T (ave) = 2.7 Nm/m
Speed = 600 rpm
=> Power=169 Watts
OR
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Hyst Loss = 151 W
Eddy Current Loss= 14 W
=> Consistent!
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November 13, 2009
Drag Torque
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Electric Steering motors are required to meet extremely
demanding specifications
One of these is that it should take very little torque to rotate
the motors' rotors when the coils are not energized (this
torque is referred to as 'drag-torque‘)
The Hysteresis solver is ideally placed to investigate these
effects
Collaboration between Vector Fields and TRW Conekt (Partners
in TSB funded ‘Advanced Electrical Machines via Materials’)
focuses on accurate evaluation of Drag Torque in PM machines
for different materials, the properties of which are supplied by
TRW.
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November 13, 2009
Instantaneous Hysteresis loss after 40
milliseconds
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November 13, 2009
Instantaneous Hysteresis loss after 60
milliseconds
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November 13, 2009
Typical Drag Torque Patterns
Typical cogging – No Hysteresis
Drag Torque for 2 Silicon Steel materials and 1 hard material
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November 13, 2009
Hysteresis motor
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Simple 50 Hz, 4-pole 3-phase hysteresis motor
– 12 slot conventional stator
– Annular rotor made from hysteretic material
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November 13, 2009
Hysteresis motor
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Torque produced due to hysteresis with a consequent rise in rotational
speed
Ripple of the torque arises because the applied field from the stator is
rotating at 1500 RPM but the rotor is almost stationary in comparison
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November 13, 2009
Conclusions
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De-magnetisation and hysteresis can be modelled
Available as full transient solvers (Elektra TR) & in
Rotating and Linear machines solvers (Carmen RM
& LM)
Available in 2D and 3D
Email : [email protected]
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November 13, 2009

Cobham Technical Services

Transcription

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