Doctoral school of energy- and geo-technology
January 15–20, 2007. Kuressaare, Estonia
Application and analysis of linear induction motors in mechatronic
systems
Roma Rinkevičien÷, Saulius Lisauskas, Vygintas Batkauskas
Vilnius Gediminas Technical University
roma.rinkeviciene@el.vtu.lt
Abstract
This paper introduces electronic engineers into the
mechatronic systems based on the linear induction
motors. Article discusses the advantages and
disadvantages of the linear induction motors (LIM)
employed in mechatronic systems. The list of the
LIM application areas is presented. The integrated
environment of modeling created for analysis
starting and breaking transients is presented.
Simulation results made for LIM with windings
connected in series-parallel.
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Keywords
Mechatronics, linear induction motor, application,
starting and breaking transients, simulation, model.
Introduction
Integrated mechanical electronic systems emerge
from a suitable combination of mechanics,
electronics and control information processing.
Thereby, these fields influence each other mutually.
Mechatronic systems are developed for mechanical
elements, machines, vehicles and precision
mechanic devices [1]. Electromechanical energy
conversation devices change electrical energy to
mechanical. Motor of any type can be used as
electromechanical converter. The most of actuators
operate in the transient mode. The frequent starting,
breaking and reverse modes characterizes operation
of these drives.
Linear induction motor in applications
High-acceleration linear motors are normally quite
short, and are designed to accelerate an object up to
a very high speed and then release the object. They
are usually used for studies of hypervelocity
collisions, as weapons, or as mass drivers for
spacecraft propulsion [2]. LIM characteristics are
worse than rotary motors those because of there
construction, but some disadvantages can be omitted
in different areas of applications. Below some
advantages and disadvantages are presented.
Advantages:
• Direct
electromagnetic
force
(no
mechanical elements, no limitations for
speed).
• Economical and cheap maintenance.
Easy expansion for any linear motion of
system topology.
Exact positioning in closed loop systems.
Possibility to provide inductor and
windings separate cooling. The power
factor developed by naturally cooling LIM
is 1 N / cm 2 . Almost 2 N / cm 2 can be
obtained with an air cooling and from
2,5 − 3 N / cm 2 with liquids [3].
All electro-mechanical controlled systems
used for an induction motors can be
adopted for a LIM without any bigger
changes.
Disadvantages:
• Power factor and efficiency are less than of
rotary motors because of a ratio of large air
gap between inductors and pole pitch
(g / τ) > 1 / 250 .
• The longitudinal end effect reduces power
factor and efficiency. This can be noticed
only with fast speed and small pole number
motors. Influence of the longitudinal end
effect can be reduced with special motor
design methods.
• Extra vibrations with distortions can be
noticed because of uncompensated normal
force [3].
Linear induction motors invented by Charles
Wheatstone in 1840 m., since this time linear
induction motors are investigated, produced and
improved and nowadays are used in mechatronic
systems whose examples are presented below.
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High-speed transport and catapult,
Industry transport systems,
Batching systems,
Vertical transport systems,
Semiconductors and electronics industry,
Explosion localizing systems,
Industry robots and machine-tools,
Protection and control systems of power
energetic,
Medical instruments,
Computer engineering.
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Analysis of LIM application areas shows problems
of developing and investigation of linear drives
being topical and urgent. In Automation department
of VGTU electric drives of catapults, high voltage
circuit-breakers, fast speed dampers, used to localize
dust explosions, pneumatic transport damper drives
with linear induction motors have been developed
and investigated [4]. Investigations of linear
induction motors began in Automation department
in 1970. The structural scheme of applications for
LIM presented in Fig 1.
Fig. 1. Classification of linear induction motor application areas
Modeling software of linear induction
motor
Developed integrated environment of modeling
allows easy to analyze of different linear induction
motor modes and can be used for investigation and
developing new linear electric drives.
Fig 2. Integrated environment of modeling
70
Developed models and their control system gives
possibility to analyze influence of motor
construction parameters or the static load on the
motor dynamic characteristics. Created integrated
environment of modeling execution window is
presented in the Fig. 2.
The integrated environment of modeling allows
choosing a windings connection type, operation
mode, motor construction parameters, acceleration
and braking time. For results program uses a special
Matlab arrays. Then they are used to draw braking
time dependences against secondary element
resistance by braking with continuous and
alternating current.
( R1 , R 2' , X m , X 1 , X 2' , τ , m , FSt )
Created software gives possibility to control model
and investigate various non-symmetrical modes
(breaking with direct current, single phase breaking),
to compare obtained characteristics and consider
influence of motor parameters to dynamic
characteristics [5]. Fig. 3 shows the main program
active window for all entering parameters of the
construction of the LIM.
Fig. 4. Program execution algorithm
Fig. 3. Active window of developed program
In a lower part of the program window these
parameters can be entered:
• inductor phase resistance , R 1 ;
The notations A, B, C, used in Fig. 4 correspond to
different winding connections:
two windings
connected in series, one phase winding and serialparallel connection.
The program allows to calculate these dependences:
• resistance of the secondary element, R '2 ;
v = f ( t ), F = f ( t ), S = f ( t ), I s = f ( t ), I ant = f ( t ),
• the main magnetizing reactance, X m ;
I A = f ( t ), I B = f ( t ), I C = f ( t ), I a = f ( t ), I b = f ( t ),
• leakage reactance of inductor, X1 ;
• leakage reactance of the secondary
element, X '2 ;
• secondary element weight , m;
• pole pitch, τ ;
• static load force, Fst .
By pressing button „Parametrų sk.“ the parameters
of the model are calculated. By pressing
„Modeliuoti“ button begins algorithm of the model
presented in Fig. 2. The results are loaded to all
available arrays. At this time dependences of
variables can be chosen from a right side of the
window Fig. 3. The program execution algorithm
presented in the Fig. 4.
I c = f ( t ).
Research of the motor parameters influence to the
dynamic characteristics requires making a lot of
simulation and all the time measure the LIM steadystate. To shorten time of simulation the program for
an automatic parameters change and LIM transition
time measurement was developed. The integrated
modeling interface is created for easy exchange of
parameters and comparing of different dynamic
characteristics of the drive.
Simulation results
There were already made some experiments of the
LIM modeling with connecting windings in a two
serial and one phase connection [6]. Here we present
71
iA
A
iB
gets the minimal value at the same braking
voltage (Fig. 8).
s
17
16
15
14
tp.p. →
the modeling results when the linear induction motor
windings at the braking mode connected in seriesparallel at breaking by single phase current [6]. Fig.
5 shows the transient current flowing in the inductor
windings. The phase B and C are connected in
parallel at the braking mode so the current decreases
but the A phase winding current remains the same.
iC
13
12
20
11
10
i→
10
9
20
0
-20
1.45
1.5
t→
1.55
1.6 s
Fig. 5. Inductor phase current alternation
A
4
ia
ib
i→
2
1
0
-1
1.52
1.54
1.56
1.58
1.6 s
t→
Fig. 6. LIM secondary element currents without load
at breaking
Induced currents in the secondary element presented
in a Fig. 6, the amplitude of the windings B and C at
any instant of time equals a half of a phase winding
current amplitude. Dependence of breaking time on
breaking voltage and secondary element resistance is
shown in Fig 7.
s
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1. Integrated environment of modeling was
developed to control the model, change its
parameters and inductor windings connection
way, process and compare results of simulation
2. Linear induction motors can be used in many
mechatronic systems. The biggest advantage of
linear induction motor is to expand a linear
motion topology.
3. Developed integrated environment of modeling
program has a friendly user interface and allows
to model different types of LIM constructions.
References
1.
2.
'
R2=80 Ω
30
tp.p. →
'
R2= 20 Ω
4.
20
10
5.
100
150
200
Um →
250
300
350 V
Fig. 7. Dependence of breaking time on braking
voltage when the voltage is attached to one phase
winding
Breaking time decreases with increased voltage at
any value of secondary element resistance. Breaking
time with the change of resistance of the secondary
72
100 Ω
Fig. 8 indicates, that the minimum value of breaking
time can be achieved by changing resistance of the
secondary element.
3.
'
R2=48.83 Ω
0
50
80
Conclusion
ic
3
-2
1.5
60
'
R2 →
Fig. 8. Dependence of breaking time against
resistance of the secondary, when the applied
breaking voltage of 100 V
-10
1.4
40
6.
Rolf
Isermann.
Mechatronic
Systems,
Fundamentals. Springer, USA. 2003, 624 p.
Budig P. K. The application of linear motors.
The third Intenational Power Electronics and
motion Control conference 2000, Vol.3. p.
1336-1341.
Lisauskas
S.
Investigation
into
nonsymmetrical modes of linear induction motors.
Summary
of
Doctoral
dissertation.
Technologija, Vilnius. 2006. 108 p.
Smilgevičius A., Rinkevičien÷ R, Poška A.
Special Systems with Low Speed Linear
Induction Motors. In Proceedings of the
International Conference on Robotics. 1999,
Rinkevičien÷, R. Lisauskas, S. Simulation of
linear induction motor dynamic breaking. In
proceedings of the International Conference
Electrical and control technologies. Kaunas:
Technologija, 2006, p.446-449.
Rinkevičien÷, R., Lisauskas, S., Petrovas, A.
Dynamic Modes of Single Phase Braking of
Linear Induction Motors. Doctoral School of
Energy and Geotechnology”. Kuressaare,
Tallinn University of Technology, 2006, p. 72–
77. ISBN 9985-69-036-2.