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Electromechanical Electromechanical Systems & ActuatorsSystems & Actuators
LINEAR MOTORSLINEAR MOTORS
Dr. Adel Gastli
Dr. Adel Gastli Linear Motors 2
CONTENT
Introduction
Types of Linear Motors
Applications
Dr. Adel Gastli Linear Motors 3
INTRODUCTION
Linear Motors are old motors which date from the 1970’s.
Were not intensively used because of their difficult control and low performance.
Advancements in Power Electronics and Microprocessors have overcome the control difficulties and have revived the use of the linear motors.
Linear motors are nowadays emerging as new technologies.
Dr. Adel Gastli Linear Motors 4
Main Types of Linear Motors
Linear Synchronous Motor Permanent Magnet
Wound Secondary Type
Linear Induction MotorSingle-Sided:
Long-primary & Short Secondary
Short-primary & Long-Secondary
Double-Sided or Sandwich
Linear Stepper Motor
Dr. Adel Gastli Linear Motors 5
Linear Synchronous Motor (LSM)
Field windingField Yoke
Armature windingPassive rail truck
I
Dr. Adel Gastli Linear Motors 6
For an LSM to operate properly the control system must accurately track the position of the moving element in order to properly synchronize the moving field current in the stationary frame (stator).
If synchronization is lost or interrupted the motor slips and loss of propulsion can occur. This situation is likely to be encountered by an LSM when external sensors are relied upon to handle motor synchronization.
If a sensor becomes dirty or mis-aligned or if fog, smoke or other airborne obstructions are present, the system will experience problems.
LSM (Cont’d)
Dr. Adel Gastli Linear Motors 7
Linear Induction Motors (LIMs) are significantly different than Linear Synchronous Motors (LSMs) in the way that they produce electro-motive forces or motion.
In a LIM, the motor stator creates an Alternating Current (AC) field that induces currents into the reaction plate, which is typically an aluminum fin. This creates eddy currents in the moving element which react with the moving field in the stator to produce thrust.
The induced currents in the aluminum plate manifest themselves in the form of heat. In cases of high duty cycles or in locked rotor conditions (where the moving element is not permitted to move) overheating can occur. In several reported cases at amusement parks, LIM fins have cracked and parts have melted.
LINEAR INDUCTION MOTOR (LIM)
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LIM (Cont’d)
SecondarySecondary
PrimaryPrimary
vv
vvss
xxStatorStator
RotorRotor
yy
3 3 φ φ windingwinding
AluminumAluminumsheetsheet(conductor)(conductor)
Cut along Cut along xyxy and enrolland enroll
Traveling mmf(or Flux Density)Wave
Dr. Adel Gastli Linear Motors 9
Traveling mmf waveLINEAR INDUCTION MOTOR
gg
FF
zz
Fundamental FFundamental F11
Ni/2Ni/2
--Ni/2Ni/200 β/2β/2 ββ−−β/2β/2
zz
Fundamental HFundamental H11Ni/2gNi/2g
--Ni/2Ni/200 β/2β/2 ββ−−β/2β/2 zz
Fundamental FFundamental F11
Ni/2Ni/2
--Ni/2gNi/2g
00
HHFF
F: F: mmfmmfH: FieldH: Field
Dr. Adel Gastli Linear Motors 10
Traveling mmf waveLINEAR INDUCTION MOTOR
NNphph : Number of turns distributed over a length : Number of turns distributed over a length mmββ ..kkww : winding factor.: winding factor.
Same Analogy as that of Rotary MachinesSame Analogy as that of Rotary Machines
i I t
i I t
i I t
z tz
t
kN I
m
a m
b m
b m
w
ph m
== − °= + °
⎫
⎬⎪
⎭⎪
⇒ = −⎛⎝⎜
⎞⎠⎟
=
cos
cos( )
cos( )
( , ) cosmax
max
ωωω
πβ
ω
π
120
120
3
2
2
4
2
F F
F
vdz
dt
dz
d
d
dtT fp= = × = × =
θθ β
πω
22 TTpp : Pole pitch: Pole pitch
f : Exciting frequency.f : Exciting frequency.
Dr. Adel Gastli Linear Motors 11
LIM PerformanceLIM PerformanceLINEAR INDUCTION MOTOR
SlipSlip sv v
vv T fs
ss p=
−= [m / sec]2
ThrustThrust FP
v
I' R s
vg
s s
=air gap power,
synchronous velocity, = [N]
3 22
2' /
Thr
ust,
FT
hrus
t, F
Speed, vSpeed, vvvss
ll’’22
RR’’22/s/s
ll11RR11
MM
Dr. Adel Gastli Linear Motors 12
Different Types of LIMLINEAR INDUCTION MOTOR
DOUBLEDOUBLE--SIDED LIM (DLIM)SIDED LIM (DLIM)
Long PrimaryLong Primary
Short SecondaryShort Secondary
SINGLESINGLE--SIDED LIM (SLIM)SIDED LIM (SLIM)Short PrimaryShort Primary
Long SecondaryLong Secondary
PrimaryPrimarySecondarySecondary
Dr. Adel Gastli Linear Motors 13
There is secondary current and secondary loss which is not associated with a corresponding amount of useful thrust.
There are reactive volt-amperes drawn from the supply which cannot be accounted for either as being due to magnetization or leakage reactance.
The physical nature of this phenomena is thought to be due to the continual removal of magnetic energy at the exit edge of a machine.
The exit edge produces a backward thrust on the secondary which subtracts from the thrust performance in the region of a speed-thrust curve.
End EffectLINEAR INDUCTION MOTOR
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End Effect on Speed-Thrust CurveLINEAR INDUCTION MOTOR
The LIM cannot run “light”at the synchronous speed vs=2pf.
Generally, the running light speed is lower than vs.
Thr
ust,
FT
hrus
t, F
Speed, vSpeed, vvvss
ShortShort--PrimaryPrimaryLIMLIM
EquivalentEquivalentRotaryRotary
IMIM
Effect of the exit edge loss on the Effect of the exit edge loss on the speedspeed--thrust curve of a LIM.thrust curve of a LIM.
Dr. Adel Gastli Linear Motors 15
APPLICATIONSTransportation (Trains)
Robotics & Material Handling
Elevators
Compressors & Pumps
Catapults and Launchers
Sliding Doors Closer
Cartain pullers
etc...
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Transportation (Trains)
Japan: Linear Chuo Shinkansen
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The superconducting Magnetically-levitated Linear Motor Car is a most promising high speed transportation system in the 21st century.
It is a vehicle befitting the requirements of the high speed and massive transportation age, as it operates at a stunning 500 Kmph, and has the transportation capacity equivalent to the existing shinkansen.
It is a most advanced traffic system, which has less noise and vibration and promises a safe and comfortable ride.
Superconducting Magnetically Levitated Linear Motor Car
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Power converterPower conversion substation
Feeder
Feeding sectionswitchgears
Guideway
Test platform
Turnout switches
Control CenterVehicle
Information cables
Via duct
Tunnel
Train Depot
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Levitation and guidance coils
LCX (Leaky coaxial cable)Panel-type
Side wall
Feeding cable Propulsion coils Cross-inductive cable Power/communication cables
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What is Superconductivity?When certain metals are cooled below a specific temperature, their electric resistance vanishes. This phenomenon is known as "superconductivity".
Once current is applied to a coil made of superconductive metal, it continues to flow permanently and without loss. This coil can generate dozens of times stronger magnetic field than that of permanent magnets.
For the Maglev, a bundle of extremely fine niobium-titanium alloy (superconductive metal) wire is embedded in a copper matrix in order to improve the stability of superconductivity. This wire is cooled with liquid helium (ca-269ßC) to be in a superconductive state.
Dr. Adel Gastli Linear Motors 21
How does it advance forwards? (Propulsion System)
By passing current through propulsion coils on the ground, a magnetic field (north and south poles) is produced, thus the train is propelled forward by the force of attraction between opposite poles and the repulsive force of same poles acting between the ground coils and the superconducting magnets built into the vehicles.
Dr. Adel Gastli Linear Motors 22
How is it levitated ? (Levitation System)
When the superconducting magnets on the vehicles pass through at high speed current flows through levitation and guidance coils on the ground producing electrodynamic levitating force to the vehicles.
Dr. Adel Gastli Linear Motors 23
Why doesn't it collide with the wall? (Guidance System)
The levitation and guidance coils on either side are connected with electric power cables. They keep the vehicles in the center of the guideway at all times by exerting an attractive force on the further side of the vehicle and a repulsive force on the nearer side should the train move off center to either side.
Dr. Adel Gastli Linear Motors 24
Other Types of Levitation Systems
Dr. Adel Gastli Linear Motors 25
OneOne--shaft Multicar Ropeless Elevatorsshaft Multicar Ropeless Elevators
Elevator car
Elevator path
Elevator Car
Moving part of linear Synchronous motor
Stationary armature coil of motor
Elevator Hall
Dr. Adel Gastli Linear Motors 26
Means maximum operating time.
Each elevator controller can act as the group controller.
If one controller is taken out of service temporarily, the remaining controllers continue to operate efficiently.
Decentralized Elevator Cars Group Control
Dr. Adel Gastli Linear Motors 27
Permanent magnets
Yoke Armature coils
Rollers Magnet holder
Suspension bar
Elevator car
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A state-of-the-art linear motor system propels the ride to reach unprecedented speeds of up to 160 km/hour, making it the most technologically-advanced ride in the world. To generate these intense speeds, an incredible 2,200,000 watts (2.2 megawatts) of power, enough to power a small town, is applied for six or seven seconds.
38-story tower of terror in AustraliaRamp
38-story tower of terror in Australia
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A linear compressor is a positive displacement, piston-type compressor in which the piston is driven directly by a linear motor, rather than by a rotary motor coupled to a mechanical mechanism as in a conventional reciprocating compressor.
Linear CompressorLinear Compressor
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Air Compressor and Vacuum Pumps -Linear-motor-driven Free Piston System
This design makes these pumps especially appropriate as air sources or vacuum units for various pneumatically operated equipment and apparatus in advanced industries.
Dr. Adel Gastli Linear Motors 31
Linear motor outperforms steam-piston catapults
Replacement for naval-aircraft launch system offers host of tactical and operational benefits.
In the rural Massachusetts town, engineers are developing the world's highest-thrust linear motor.
For Naval aviation, it may mean the end of the age of steam.
By 2005, naval architects may begin replacing the enormous steam catapults on aircraft carriers with EMALS--The Electromagnetic Aircraft Launch System.
Dr. Adel Gastli Linear Motors 32
EMALS would bring a host of improvements to ship design and Naval aviation.
With a maximum design thrust of 132,000 kgf, EMALS offers 28% more thrust than steam catapults. Proposed EMALS could accelerate 45,000-kg aircraft to 60 m/s2 in 100m.
Linear motor outperforms steam-piston catapults (Cont’d)
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The Launch Loop: a low cost Earth-to-high orbit launch system
A closed loop made of laminated iron ribbon is continuously launched to space by an asynchronous linear motor. The motor consists of high-frequency electromagnets producing an undulating magnetic field. The field moves at 14 km/s -- only slightly faster than the loop. A 2600 km away from the motor, the loop returns to the Earth, to be accelerated by another motor and deflected by a magnet back to space. Cargo is transported by Maglev trains riding on the loop.
80 km
LoopLinear motor anddeflecting magnet
Maglev trainriding on the loop
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Examples of applications
• textile machinery• packaging machines• handling machinery• robot applications• laboratory automation• and others...
Small Power Linear Motors
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MEGAmation has over 350 Linear XY stepper motor robot heads in use throughout the world.
Linear Stepper Motors Applied in Robotics
Pharmaceutical Automation
Automotive drive train assembly
Electronic PCBMaker
Mechanical Pick & Place Assembly
Dr. Adel Gastli Linear Motors 36
A wafer stepper is a high-precision chip manufacturing system. Modern wafer steppers are confronted with more severe demands on their performance, due to the ongoing increase of chip capacity, where performance can be defined in terms of speed and accuracy of the positioning mechanism of the stepper.
A Wafer Linear Stepper Motor
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Triple Blade shaving System 1 Hour Charge Universal Voltage 12,000 Blade strokes a minute
Linear Motor Drive Men's shaver