linear_motors.pdf

Electromechanical Electromechanical Systems & ActuatorsSystems & Actuators

LINEAR MOTORSLINEAR MOTORS

Dr. Adel Gastli

Dr. Adel Gastli Linear Motors 2

CONTENT

Introduction

Types of Linear Motors

Applications


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.


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


Linear Synchronous Motor (LSM)

Field windingField Yoke

Armature windingPassive rail truck

I


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)


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)


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


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


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.


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


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


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


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.


APPLICATIONSTransportation (Trains)

Robotics & Material Handling

Elevators

Compressors & Pumps

Catapults and Launchers

Sliding Doors Closer

Cartain pullers

etc...


Transportation (Trains)

Japan: Linear Chuo Shinkansen


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


Power converterPower conversion substation

Feeder

Feeding sectionswitchgears

Guideway

Test platform

Turnout switches

Control CenterVehicle

Information cables

Via duct

Tunnel

Train Depot


Levitation and guidance coils

LCX (Leaky coaxial cable)Panel-type

Side wall

Feeding cable Propulsion coils Cross-inductive cable Power/communication cables


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.


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.


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.


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.


Other Types of Levitation Systems


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


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


Permanent magnets

Yoke Armature coils

Rollers Magnet holder

Suspension bar

Elevator car


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


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


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.


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.


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)


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


Examples of applications

• textile machinery• packaging machines• handling machinery• robot applications• laboratory automation• and others...

Small Power Linear Motors


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


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


Triple Blade shaving System 1 Hour Charge Universal Voltage 12,000 Blade strokes a minute

Linear Motor Drive Men's shaver

linear_motors.pdf

Documents

adel gastli linear motors

linear motors tp

introduction linear

linear synchronous motors

old motors

sandwich linear stepper

motor stator

motor synchronization