Dr. Adel Gastli
ElectromechanicalElectromechanical SystemsSystems && ActuatorsActuators
LINEARLINEAR MOTORSMOTORS
CONTENT
Introduction Types of Linear Motors Applications
Dr. Adel Gastli Linear Motors 2 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 3
Main Types of Linear Motors
Linear Synchronous Motor Permanent Magnet Wound Secondary Type Linear Induction Motor Single-Sided:
Long-primary & Short Secondary
Short-primary & Long-Secondary Double-Sided or Sandwich Linear Stepper Motor
Dr. Adel Gastli Linear Motors 4 Linear Synchronous Motor (LSM)
Field Yoke Field winding
I
Passive rail truck Armature winding
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LSM (Cont’d)
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.
Dr. Adel Gastli Linear Motors 6 LINEAR INDUCTION MOTOR (LIM)
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.
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LIM (Cont’d)
Cut along xy and enroll
x Stator 3 φ winding v Secondary
y vs
Primary Aluminum Rotor sheet Traveling mmf (conductor) (or Flux Density) Wave
Dr. Adel Gastli Linear Motors 8 Traveling mmf wave LINEAR INDUCTION MOTOR
F Fundamental F1 Ni/2
0 −β/2 β/2 β -Ni/2 z g
Fundamental H 1 Fundamental F1 H Ni/2g F Ni/2 F: mmf 0 −β/2 0 β/2 β -Ni/2 z H: Field -Ni/2g
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Traveling mmf wave LINEAR INDUCTION MOTOR
Same Analogy as that of Rotary Machines
iI= cosω t ⎫ am ⎪ 3 ⎛ 2πz ⎞ iIbm=−°cos(ω t120 )⎬ ⇒=F (,)zt Fmax cos⎜ −ωt⎟ ⎪ 2 ⎝ β ⎠ iIbm=+°cos(ω t120 )⎭
N : Number of turns distributed over a length mβ . 4 NIph m ph k : winding factor. F = k kw : winding factor. max π w 2m dz dz dθ β T : Pole pitch v == × = ×=ω 2Tf Tp : Pole pitch dt dθ dt 2π p f : Exciting frequency.
Dr. Adel Gastli Linear Motors 10 LIMLIM PerformancePerformance LINEAR INDUCTION MOTOR
vvs − Slip s = vTfsp= 2 [m / sec] vs
2 air gap power, Pg 3I'2 R'/2 s Thrust F = = [N] synchronous velocity, vssv
R1 l1 l’2
M R’2/s Thrust, F Thrust, F
v vs Speed, v
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Different Types of LIM
LINEAR INDUCTION MOTOR
DOUBLE-SIDED LIM (DLIM)
Secondary Primary
SINGLE-SIDED LIM (SLIM) Short Primary Long Primary
Long Secondary Short Secondary
Dr. Adel Gastli Linear Motors 12 End Effect LINEAR INDUCTION MOTOR
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.
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End Effect on Speed-Thrust Curve LINEAR INDUCTION MOTOR
The LIM cannot run “light” Short-Primary at the synchronous speed LIM
vs=2pf. Equivalent Thrust, F Thrust, F Rotary IM Generally, the running light v Speed, v speed is lower than vs. s Effect of the exit edge loss on the speed-thrust curve of a LIM.
Dr. Adel Gastli Linear Motors 14 APPLICATIONS
Transportation (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
Dr. Adel Gastli Linear Motors 16 Superconducting Magnetically Levitated Linear Motor Car
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.
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Train Depot
Tunnel
Vehicle Control Center Via duct Turnout switches
Test platform Information cables
Feeding section switchgears
Feeder Guideway
Power conversion substation Power converter
Dr. Adel Gastli Linear Motors 18 LCX (Leaky coaxial cable) Panel-type
Side wall Levitation and guidance coils
Power/ Feeding cable Propulsion coils Cross-inductive cable 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 20 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.
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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 22 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.
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Other Types of Levitation Systems
Dr. Adel Gastli Linear Motors 24 OneOne--shaftshaft MulticarMulticar RopelessRopeless ElevatorsElevators
Moving part of linear Stationary armature coil Synchronous motor of motor
Elevator car
Elevator path
Elevator Elevator Car Hall
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Decentralized Elevator Cars Group Control
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.
Dr. Adel Gastli Linear Motors 26 Permanent magnets Armature coils Suspension bar Yoke
Rollers Magnet holder
Elevator car
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38-story tower of terror in Australia
38-story tower of terror in Australia Ramp
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 Dr. seconds.Adel Gastli Linear Motors 28 LinearLinear CompressorCompressor 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.
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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 30 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.
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Linear motor outperforms steam-piston catapults (Cont’d)
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.
Dr. Adel Gastli Linear Motors 32 The Launch Loop: a low cost Earth-to-high orbit launch system
Linear motor and deflecting magnet Loop 80 km
Maglev train riding on the loop
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.
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Small Power Linear Motors
Examples of applications
• textile machinery • packaging machines • handling machinery • robot applications • laboratory automation • and others...
Dr. Adel Gastli Linear Motors 34 Linear Stepper Motors Applied in Robotics
MEGAmation has over 350 Linear XY stepper motor robot heads in use throughout the world.
Pharmaceutical Automotive drive Electronic PCB Mechanical Pick & Place Automation train assembly Maker Assembly
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A Wafer Linear Stepper Motor
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.
Dr. Adel Gastli Linear Motors 36 Linear Motor Drive Men's shaver
Triple Blade shaving System 1 Hour Charge Universal Voltage 12,000 Blade strokes a minute
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