Transcript 2D Transient

2D Transient
Overview
2D Transient
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4/20/04, pg. 2
Introduction and Theory
Source Types
Source Waveforms
Time-varying materials
Solution Setup
Mechanical Setup
Results
General Suggestions
Introduction to 2D Transient
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4/20/04, pg. 3
Transient “time-stepping” or “time-domain” solver
Coupled FEA with external circuits and motion
equations
Allows non-sinusoidal current or voltage excitation
Allows rotational or translational motion
Links with external user control program
Comprehensive results
Application Examples
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4/20/04, pg. 4
Motors/ Generators (RMxprt)
Variable Reluctance Sensors
Eddy Current Braking
Frictionless Bearings/Actuation
Inductors/Transformers
Solenoids
Fully Coupled
Dynamic Physics Solution
Time-varying Electric and Magnetic Fields
Current Source Density
Electric Scalar Potential
Velocity
A
   A  J s  
 V    H c      A
t
Magnetic Vector Potential
4/20/04, pg. 5
Permanent Magnet
Types of Induced Eddy Currents
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4/20/04, pg. 6
Within source conductors (skin effect)
Resulting from a stationary AC field diffusing into a
nearby conductor (proximity effect)
Resulting from the motion of a DC source, such as
a magnet, near a conductor (proximity effect)
A combination of all three above (the most
complex)
Magnetic Field Diffusion
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Magnetic fields “diffuse” into materials at different rates
depending on:
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Material properties of the component
Physical size of the component
For a cylindrical conductor, diffusion time is:
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4/20/04, pg. 7
a 2
2.4048
2
(sec)
Induced eddy currents always occur in conducting objects
due to time-varying fields; however, they may not always be
significant
Time varying Input Parameters
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4/20/04, pg. 8
Conductor Sources
Load Conditions
Electrical Parameters and Components
Mechanical Parameters and Components
Linear Material Properties
Freely Defined Behavior
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Constants
Functions (Expressions)
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4/20/04, pg. 9
Numeric
Algebraic
Trigonometric
Input Data File (Piecewise linear)
Meshing for Rotational Motion
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“Moving Surface” method used
Stationary part
Master moving
surface
7
7'
5
6
6'
5'
3
4
4'
3'
2
2'
1
1'
Slave moving
surface
Moving part(s)
4/20/04, pg. 10
Meshing for Rotational Motion
Rotor
Stator
Band
4/20/04, pg. 11
Air gap
Meshing for Translational Motion
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“Moving Band” method used
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Re-mesh band area at each time step
Stationary region and moving part(s) are not re-meshed
Stationary region
Band
Moving part(s)
4/20/04, pg. 12
Comprehensive Results
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Solution Parameters vs. Time
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Field Evaluations at an Instant of Time
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4/20/04, pg. 13
Back EMF, Flux Linkage, Power Loss, Terminal Voltage,
Winding Current
Force, Torque, Position, Speed
Error
Single instant
Numerous field solutions can be viewed at a user defined
interval
Additional Key Features
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4/20/04, pg. 14
Solution Pause/ Re-Start Feature
Refresh Solution Parameters
Comparison of 2D Products
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Electrostatic, Magnetostatic, Eddy Current
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Equivalent Circuit Generator
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Series of DC solutions at instants (or snap-shots) in time
Partially dynamic solution
Concentrates on saturation and back-emf effects
Can evaluate design alternatives with parametrics
No time-induced field effects are considered!
2D Transient
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4/20/04, pg. 15
Steady State Solvers (DC and frequency domain)
Completely dynamic solution (time domain)
Types of Sources - Overview
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Current, voltage, and external sources are
available
Two conductor types:
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4/20/04, pg. 16
Solid - eddy currents
Stranded - no eddy currents considered
Types of Sources
2D Transient
Sources Types
Current
Stranded
Total
Current (A)
Current
Density (A/m2)
Winding Setup
Polatrities
No. of Turns
No. of Parallel Branches
Voltage
Extra Connection
Solid
Stranded
Solid
Total
Current (A)
Total Terminal
Voltage (V)
Total Voltage
Drop (V)
Winding Setup
Terminal Attribute I(initial), R, L, C, Wye Connected
Polarites
No. of Turns
No. of Parallel Branches
Note: for stranded conductors
 Need to select both Go and Return objects together
 Need to define “winding setup” as the total phase winding
seen from the terminals
4/20/04, pg. 17
Solid Current or Voltage Source
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4/20/04, pg. 18
A solid current source (total Amps only) can be
functional or constant
A solid voltage source (total Volts only) is assumed
to be the total voltage drop over the length of a
conductor. Voltage drops can be functional or
constant; however, the potential is constant over
the entire cross-section of the conductor
Stranded Current Source
Winding Setup
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4/20/04, pg. 19
Specify polarity of each object as positive,
negative, or function
Specify total turns as seen from terminal
Specify number of parallel branches as seen from
terminal
Stranded Voltage Source
Winding Setup
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4/20/04, pg. 20
Specify polarity of each object
as positive, negative, or function.
A function will be used for brush
type motors to handle commutation.
The value of polarity is either 1 or -1.
In general df = f (T,S,P)
Make the polarity index, df, a function of position (0, 360 deg).
Whenever a coil passes over a stationary brush, the change
of its polarity is used to indicate the transition from one coil
group to the other
Use commutation interval to represent the actual brush size
Use different transition curves to describe different
commutation processes
Stranded Voltage Source
Terminal Attributes
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Initial Current: used if motor is
running at t=0
Resistance: DC resistance of the
winding or additional external
resistance, f (S, T, P)
Inductance: End turn or additional
external inductance, f (S, T, P)
Capacitance: External capacitance,
such as a starting capacitor in a single phase induction motor used
to change capacitance as a function of speed, time, or position
Y-connect: Used for three phase machines to indicate that the
windings are Y-connected and have NO neutral return (Ia + Ib + Ic =
0)
Specify total turns as seen from terminal
Specify number of parallel branches as seen from terminal
NOTE: R, L, and C are assumed to be connected in SERIES
at end of the terminal
4/20/04, pg. 21
External Connection
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4/20/04, pg. 22
Choose External Connection
Can be either solid or stranded
Value field is not active. The
value will be determined by
the external circuit.
External Connection
Winding Setup
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4/20/04, pg. 23
For winding setup specify:
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Polarity
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Initial Current
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Total Turns and the
number of Parallel
Branches
External Connection
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Windings are represented in the Schematic Editor
as a 1H inductor
The dot represents the
positive terminal
4/20/04, pg. 24
External Connection
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To complete the winding definition, you need to add
the DC resistance and any end leakage inductance
or line inductance.
This inductor represents the
end turn leakage inductance
of the entire B phase winding.
4/20/04, pg. 25
This is the DC resistance of
the entire B phase winding.
This inductor is automatically
included. It represents the B
phase winding in the FEA model;
the value of 1H is neglected.
Create Custom Drive Circuit!
Freewheeling
Diode
A Phase
Winding
Current and
Voltage Probes
B Phase
Winding
Diode and Switch
combination acting
as a transistor
Position dependent sources to toggle switches S1-S8
Elements: R, L, C, Diode, and
Switches (V & I)
3 Diode types: Default, Rectify,
Freewheel
Sources: V & I as a function of
Time, Speed, or Position
4/20/04, pg. 26
External Circuit
Position Dependent Source
Voltage
One Voltage Pulse
44.9
1.0
22.45
45
0.1
When you exit the Schematic
Editor - indicate Time, Position,
or Speed Dependent
4/20/04, pg. 27
Mechanical
Degrees
0.1
These values represent position in
mechanical degrees, even though
labeled as [s]
Source End Connections
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Multiple objects must be selected
Used primarily for passive conductors (with no
source current assigned) such as squirrel cage
induction machines to indicate that the group of
objects selected are connected together
The resistance and inductance between selected
objects is specified with following assumptions:
1.
2.
3.
4/20/04, pg. 28
The connections are periodic
There are no breaks in the end ring
These values are constant only
Source Waveforms
Overview
2D Transient Excitation Waveforms
 Static DC Current
 Steady State Sinusoid
 Steady State Square Wave
 Steady State Triangle Wave
 Composite
 PWM Waveform
 Arbitrary Piecewise Linear Table
4/20/04, pg. 29
Source Waveforms
4/20/04, pg. 30
DC Pulse
Sinusoidal
Square Wave
Triangle Wave
Source Waveforms
Composite Waveform
PWM
Arbitrary
4/20/04, pg. 31
Functional Source Summary
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4/20/04, pg. 32
Current and voltage sources (solid or stranded) can be
constant or functions of time, position, or speed
Auxiliary and Main winding can be a function of time, a good
choice for single and multi-phase machines.
For DC machines, it’s often better to use sources as a
function of position. Here a new expression in the function
evaluator is used: pwlx
Time-varying materials
Functional conductivity
based on speed
4/20/04, pg. 33
Time-varying materials
T - Time (seconds)
P - Position (degrees)
S - Speed (rpm or deg/sec)
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4/20/04, pg. 34
Bar_Cond: conductivity changes as a function of speed. In
the locked rotor case where the motor usually runs a little
warmer, = 2.68e7 (S/m) and increases linearly until rated
speed (3600 rpm) where its value is 2.96e7 (S/m).
Single_Bar: Here the conductivity switches from 2.68e7 to
zero (S/m) to simulate a broken rotor bar at 0.1 seconds.
Summary of Functional
Variables
Source variables
Solid Conductor Variables
The following range of functional source variables are available
for their respective conductors:
The following range of functional variables
are available for solid conductors:
Perfect Conductor
Total current source
Func(p, s, t)
Conductivity
Func(x, y, p, t)
Solid Conductor
Current Source
Voltage Source
Func(p, s, t)
Func(p, s, t)
End Resistance
Must be constant
Stranded Conductor
Current Density
Current Source
Voltage Source
Func(x, y, p, t)
Func(p, s, t)
Func(p, s, t)
End Inductance
Must be constant
Winding Variables
4/20/04, pg. 35
Mechanical Transient Variables
The following range of functional variables are available for
windings:
The following functional variables are
available for mechanical transient setups:
Polarity
Func( p, s, t)
Speed
Func(p, s, t)
Resistance
Func(p, s, t)
Load
Func(p, s, t)
Inductance
Func(p, s, t)
Friction
Func(p, s, t)
Capacitance
Func(p, s, t)
Setup Solution Options
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4/20/04, pg. 36
MUST manually create a mesh No remeshing for entire solution
Stop and Restart capability
Fixed time step is typically 20-50
steps per electrical cycle
Adaptive time step needs an
initial, maximum, and minimum
timestep
Specify save fields time step by
clicking on Setup…
Model depth (in user units)
Symmetry multiplier for periodic
models (quarter model uses 4)
Identify custom User Control
Program
Identify post processing macros
Output energy error is desired
Setup Solution Motion Setup
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Three types of Objects:
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2.
3.
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4/20/04, pg. 37
Stationary
Band
Moving
Set Band: all objects inside of
Band object are automatically
chosen and are assumed to
be moving together
Select type of Motion, center
of rotation, limits, and initial
position.
Mechanical Setup
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Check “consider mechanical transient” unless objects are stationary or have
constant speed
Set units of speed. If degrees/sec is selected, then all functions set
previously that depend on speed will be in deg/sec. The other option is rpm.
Enter moment of inertia (for rotational motion) or mass (for translational
motion)
When performing a mechanical transient simulation, damping and load
torque (or load force) can be a function of f (T, S, P).
Note:
While inertia is automatically
calculated by the simulation,
gravity must be separately
entered as a load torque or
load force
4/20/04, pg. 38
Functional Mech Examples
T(N-m)
4/20/04, pg. 39
Load Torque
2D Transient Results
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4/20/04, pg. 40
Transient plots can be viewed
by selecting Solutions/
Transient Data
Fields can be viewed at a
particular time step by
selecting Post Process/
Fields...
Transient plots can be opened,
modified, and combined by
selecting Post Process/
Transient Data...
Transient plot
4/20/04, pg. 41
Field plot from Post Processor
4/20/04, pg. 42
Combined transient plot
4/20/04, pg. 43
General Suggestions
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Manual Mesh - transient solution relies on the
creation of a ‘sound’ manual mesh
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Time Step
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Each problem will have an ‘optimum’ step
User must experiment to get suitable value
Large Motion
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4/20/04, pg. 44
Distribution should be as even as possible
Total number of elements should be adequate
Re-meshing inside “band” required with linear motion
Mesh density inside “band” must be fine