Contents

1 Introduction 1

2 Literature Review 32.1 Linear electromagnetic machines (LEMs) . . . . . . . . . . . . 32.2 Long-Stator Linear Synchronous Motor Drive . . . . . . . . . 4

3 Comparison Study 113.1 Steam Catapult vs. Electromagnetic Aircraft Launch System

(EMALS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2 Linear Induction Motor vs. Linear Synchronous Motor . . . . 17

3.2.1 Flexibility to variable and uncertain demand . . . . . . 173.2.2 Reliability of operation . . . . . . . . . . . . . . . . . . 193.2.3 Capital cost . . . . . . . . . . . . . . . . . . . . . . . . 203.2.4 Operational cost . . . . . . . . . . . . . . . . . . . . . 22

4 Analytical Design 24

5 Conclusion 45

1

List of Figures

2.1 Linear electric machines (a) with progressive motion (LEMs) (AfterBoldea, I. Nasar, S.A., Linear Motion Electromagnetic Devices,

Taylor Francis, New York, 2001); (b) with oscillatory resonant

motion (LOMs): motor plus generator (a. linear motor, b. linear

generator, c. resonant springs (features), d. coupling shaft). (After

Pompermaier, C. et al., IEEE Trans. IE, 58, 2011.) . . . . . . . . 42.2 Transrapid TR08 vehicle and close-up of propulsion/levitation mod-

ule containing on-board exciting magnets for LSM . . . . . . . . . 62.3 Cross-section of segment of LSM. Flux,, from the exciting mag-

net interacts with the travelling magnetic wave from the stator to

generate vehicle thrust . . . . . . . . . . . . . . . . . . . . . . . 62.4 Block Diagram of the power circuit for the LSM . . . . . . . . . . 7

3.1 Steam catapult being used for Launching a jet from a naval aircraftcarrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.2 Disk Alternator Cross Section . . . . . . . . . . . . . . . . . . . 143.3 EMALS launch Motor . . . . . . . . . . . . . . . . . . . . . . . 173.4 EMALS being tested on a US navy ship . . . . . . . . . . . . . . 18

4.1 Maxwell3D Magnetic ux density Plot for a single winding . . 44

2

List of Tables

3.1 EMALS REQUIREMENTS . . . . . . . . . . . . . . . . . . . . 13

3

Abstract

Linear synchronous motors (LSMs), which have great advantages, such

as simple structure, high positioning accuracy, good performance, high thrust

force density, high dynamic response, are widely used in high precision di-

rect drive eld. Linear Synchronous Motor (LSM) technology is scalable and

adaptable to a wide range of applications, from small transport and posi-

tioning systems to large people movers. Unlike short stroke linear motors,

LSMs generate propulsive force by running current through a stator creating

an electro-magnetic eld that interacts with a set of permanent magnets on

a vehicle to create thrust. The permanent magnets serve as the motor sec-

ondary, equivalent to a rotor in conventional motors, enabling linear motion.

The magnet array and vehicle is propelled by the moving electro-magnetic

eld, traveling along as electric current is applied to the stator beneath the

vehicle. The vehicles movement is regulated by a sophisticated control sys-

tem incorporating state-of-the-art position sensing technology.

With the proliferation of electromagnetic launch systems presently being

designed, built, or studied, there appears to be no limit to their application.

One of the intriguing applications is electromagnetically catapulting aircraft

from the deck of an aircraft carrier.

This report describes the design and analysis of a very large actuator for

a military ship system - an Electro-Magnetic Aircraft Launching System, or

EMALS, which will accelerate aircraft to ight speeds in very short distances.

The aim is to replace the steam catapult currently used on aircraft carriers

with a Linear electric motor. The entire system should t within the connes

of the existing steam catapult. The advantages of such a system are increased

operational availability, lower airframe stress due to programmable acceler-

ation proles, and reduced maintenance (and hence reduced manning). The

goal of the study described here is to investigate the many feasible solutions

and to use simulations to compare their performance.

Chapter 1

Introduction

Electro-Magnetic Aircraft Launch System (EMALS) is a complete carrier-

based launch system designed for Naval Aircraft Carriers. The launching

system is designed to expand the operational capability of the Navys future

carriers. The mission and function of EMALS remains the same as tradi-

tional steam catapult; however, it employs entirely dierent technologies.

EMALS uses stored kinetic energy and solid-state electrical power conver-

sion. This technology permits a high degree of computer control, monitoring

and automation. The system will also provide the capability for launching

all current and future carrier air wing platforms lightweight unmanned sys-

tems to heavy strike ghters. As the 21st century dawns, steam catapults

are running out of steam. Massive systems that require signicant manpower

to operate and maintain, they are reaching the limits of their abilities, es-

pecially as aircraft continue to gain weight. Electromagnetic catapults will

require less manpower to operate and improve reliability; they should also

lengthen aircraft service life by being gentler on airframes.

The amount of steam needed to launch an airplane depends on the crafts

weight, and once a launch has begun, adjustments cannot be made. If too

much steam is used, the nose wheel landing gear, which attaches to the cat-

apult, can be ripped o the aircraft. If too little steam is used, the aircraft

wont reach takeo speed and will tumble into the water. The launch con-

trol system for electromagnetic catapults, on the other hand, will know what

1

speed an aircraft should have at any point during the launch sequence, and

can make adjustments during the process to ensure that an aircraft will be

within 3 mph (4.827 km) of the desired takeo speed.

The present EMALS design centers around a linear synchronous motor,

supplied power from pulsed disk alternators through a cycloconverter. Av-

erage power, obtained from an independent source on the host platform, is

stored kinetically in the rotors of the disk alternators. It is then released

in a 2-3 second pulse during a launch. This high frequency power is fed to

the cycloconverter which acts as a rising voltage, rising frequency source to

the launch motor. The linear synchronous motor takes the power from the

cycloconverter and accelerates the aircraft down the launch stroke, all the

while providing "real time" closed loop control[1].

2

Chapter 2

Literature Review

2.1 Linear electromagnetic machines (LEMs)

LEMs develop electromagnetic forces based on Faradays and Amperes

laws, and produce directly linear motion. Linear motion may be either pro-

gressive (Figure 2.1a) or oscillatory (Figure 2.1b) [2, 3, 4, 5]. Linear pro-

gressive motion even when experiencing back and forth, but nonperiodic,

operation modes leads to LEMs whose topology dier (in general) from that

of linear oscillatory machines (LOMs). The linear oscillatory motion takes

place in general at resonancewhen mechanical eigen frequency equals the elec-

trical frequencyto secure high eciency in the presence of a strong springlike

force (mechanical or even magnetic) [6].

In general, the progressive motion LEMs are three-phase ac devices that

operate in brushless congurations, while LOMs are typically single-phase ac

devices.

The progressive motion LEMs operate at variable voltage and frequency

to vary speed at high eciency for wide speed control ranges. On the con-

trary, LOMs operate in general at resonant (xed) frequency and variable

voltage. Close-loop position control may be applied for both LEMs and

LOMs. A slight variation of frequency in LOMs may be needed to adjust the

resonance frequency with the mechanical (magnetic) springs rigidity varia-

tion due to temperature and (or) aging and thus secure high frequency over

3

Figure 2.1: Linear electric machines (a) with progressive motion (LEMs) (After

Boldea, I. Nasar, S.A., Linear Motion Electromagnetic Devices, Taylor Francis,

New York, 2001); (b) with oscillatory resonant motion (LOMs): motor plus gen-

erator (a. linear motor, b. linear generator, c. resonant springs (features), d.

coupling shaft). (After Pompermaier, C. et al., IEEE Trans. IE, 58, 2011.)

the entire device life (10 years or more). Linear progressive motion machines

may be classied by principle into Linear induction machines (with sinu-

soidal current control) Linear synchronous (brushless ac) machines (with

sinusoidal current control) Linear brushless dc machines (with trapezoidal

(block) current control) Linear dc brush machines

2.2 Long-Stator Linear Synchronous Motor

Drive

Basic conguration

LSM drives with electromagnets were developed and are utilized for the

German Transrapid maglev system for high-speed transportation. [7] This

system has been tested in Emsland, Germany since 1984, and is now applied

to the 30 km Shanghai Pudong Airport connection to city-center. A very

low-speed system for urban applications, the German M-Bahn, was utilized

in Berlin for a few years beginning in 1988 as a demonstration track.[8]

4

The basic system construction of the long-stator linear synchronous mo-

tor (LSM) drive is shown in Figure 2.2 through Figure 2.4. Figure 2.2 shows

the Transrapid TR08 maglev vehicle that is the type of vehicle being installed

in the Shanghai airport-city connector line. As with the LIM-driven system,

propulsion-levitation modules that wrap around the guideway are located on

each side of each vehicle. Each module contains the exciting eld magnets

of the LSM that also serve as the levitation magnets that pull the vehicle

up to the LSM stator magnets packs attached to the guideway. Figure 2.3

shows a side-view cross-section of the LSM with the 3-phase primary wind-

ing embedded in the stator core on the guideway and the vehicles levitation

magnets.

The long stators of the LSM located on the guideway form the active

track. The reactive forces of propulsion and vehicle levitation act on the

stator cores. Its supporting structure is required to have enough strength to

handle repeated loading of this force, and the stator coils need to be isolated

from ground. Dimensions of the stators are determined by the highest per-

formance requirement of the systems.

In order to reduce operational losses and for stability of the power supply

system, the long stator of the LSM is separated into a number of sections

controlled by the section switches. The minimum length between two section

switches depends on the required acceleration and length of a train. The op-

erating frequency of the section switches becomes high if a large number of

trains are operated on the track each day.

The currents in the stator coils must be synchronized with the trains

position and velocity. Proper control of the train can only be accomplished

by sending information to the converter stations through the use of sensing

equipment and signal transmission systems. Because synchronization is es-

sential to the LSM, the sensing and signal transmission system must have

high precision and reliability.

The railway substation shown in Figure 2.4 is connected to the power

5

Figure 2.2: Transrapid TR08 vehicle and close-up of propulsion/levitation module

containing on-board exciting magnets for LSM

Figure 2.3: Cross-section of segment of LSM. Flux,, from the exciting magnet

interacts with the travelling magnetic wave from the stator to generate vehicle

thrust

6

grid, so its location may be constrained. In some cases it is advantageous

for the system operator to own the transmission line from the grid. The

power converter station feeds variable-voltage power to the long stator sec-

tions through the transmission lines, and controls both the powers frequency

and phase as required by the trains position and velocity. This means that

the number of converter stations must equal the maximum number of trains

possible on the whole track. An increased number of converter stations will

be required near train terminals and intermediate stations. Operational volt-

age of the converter is limited by the maximum voltage level capability of

transmission cables, section switches, and stator windings to prevent arcing

and electrical breakdown.

Figure 2.4: Block Diagram of the power circuit for the LSM

Advantages

Vehicle drive power is supplied by the long-stator, winding attached to

the guideway. Because the stator winding and power conditioning equipment

is located wayside, the vehicle should be generally lighter. This permits the

operation at high-speed (up to 500 kph has been demonstrated) because the

7

vehicle does not bear the weight of the high-power primary propulsion com-

ponents needed to obtain these speeds, nor does the electric power need to

be transferred to the vehicle. The power-rating capability of the motor can

be tailored to the requirements of the specic section of route such as regions

of high grade or at the station for high acceleration.

The Transrapid and other proposed LSM systems also use the on-board

levitation electromagnets (or permanent magnets) as part of the eld source

for the LSM propulsion. This results in a highly integrated bogie design that

reduces vehicle weight, and helps reduce the requirements of the levitation

control system to mitigate the eects of transverse forces on ride quality.

Other systems such as power generation and operation control can be in-

tegrated with drive system. The placement of main power components on

the wayside and reduction in vehicle weight results in high acceleration and

deceleration capability. However, the utility of the high acceleration is lim-

ited by ride comfort, seat-belt operating conditions, and safety requirements.

Within these limits for the FTA urban maglev program, both LIM and

LSM have the capability to meet the high-acceleration requirements, and

neither has a particular advantage in terms of the superiority of these three

factors.

The electrical-to-mechanical conversion eciency of LSM is high at the

terminals of the guideway motor, but the impedance of the active block length

of the motor reduces that value. A detailed analysis conducted for the U.S.

Dept. of Transportation National Maglev Initiative modelled the Transrapid

TR07 LSM with a lumped-parameter synchronous motor circuit model.[9]

This model was benchmarked with data from the Transrapid TR06-II mo-

tor, and the author of that study indicates that the agreement with data was

excellent. For the TR07 with an on-board active length of 45 meter with

a relatively-short LSM block section length of 300 meters, the eciency at

the terminals of the LSM immediately below the vehicle is 98% at a vehi-

cle speed of 200 kph in maximum-thrust operating mode. The eciency at

the terminals of the LSM block section is 85%, and at the output of the

8

variable-voltage, variable-frequency converter, the eciency drops to 62% at

the same speed and operating condition. The maximum eciency at the

converter output for this LSM, which was designed for higher speed, is 87%

at a speed of 480 kph. However, it should be noted that if the block section

length of the active LSM is longer, the eciency is reduced.

Disadvantages

One disadvantage of the LSM drive is that it requires data for the exact

position of the on-board magnets to ensure that the vehicle is synchronous

with the traveling wave generated by the stator winding in the guideway.

A very reliable and precise vehicle position and velocity sensing system is

essential. This information must be transmitted to the converter station to

generate the travelling magnetic eld at the appropriate magnitude and fre-

quency.

Compared to the simple reaction rail of the LIM, the active track struc-

ture of the LSM is very complicated. It requires continuous installation of

stator coils in the guideway and wayside converters to energize each block

section of track. This results in many components that must be maintained

to assure the safety of the system. The maintenance of proper position of the

guideway stator coils is particularly critical so that the proper clearance gap

is maintained to the on-board levitation/excitation magnets. Reduction of

the normal 1 cm gap can result in signicant increase in the vehicle lift force

causing the vehicle to lock-on to the guideway or impact between the vehi-

cle magnets and the guideway stator. Frequent inspection and maintenance

of the guideway coils and stator core is necessary to ensure proper alignment.

There are several operational requirements for the vehicles relative to the

guideway. Each block section of the guideway can drive only one vehicle at

a time, and that section requires its own converter. The operational density

of trains on the route determines the number of converter stations, which

implies many converters are necessary for short headway systems. This has

particular impact near terminals where the power feeding system becomes

9

complicated and many converters are needed since vehicles are moving slowly,

more closely spaced, and switching direction or routes. The vehicle has an

LSM motor on both the port and starboard sides, and each of these is pow-

ered by independent power supplies at the transitions between stator sections.

These supplies must have high reliability for balanced thrust from both sides

of the vehicle. The eld magnet of LSM is also commonly used for vertical

suspension, which means it is operated continuously. This requires a very

reliable on-board power supply including batteries. In the event of a mal-

function of trackside stators, the riding comfort is signicantly deteriorated.

The performance of the transportation system is determined by the con-

guration of the active guideway, and the system is not adaptable to the

change of passenger demand. Vehicles cannot be added easily to accommo-

date changes outside the original design (although they are easily removed).

The LSM must be congured, and the initial investment made to accommo-

date the highest demand anticipated over the life of the design. For ecient

use of capital investment, a very accurate estimate of demand is necessary.

10

Chapter 3

Comparison Study

3.1 Steam Catapult vs. Electromagnetic Air-

craft Launch System (EMALS)

The steam catapults are large, heavy, and operate without feedback con-

trol. They impart large transient loads to the airframe and are dicult and

time consuming to maintain. The steam catapult is also approaching its op-

erational limit with the present complement of naval aircraft. The inexorable

trend towards heavier, faster aircraft will soon result in launch energy require-

ments that exceed the capability of the steam catapult. An electromagnetic

launch system oers higher launch energy capability, as well as substan-

tial improvements in areas other than performance. These include reduced

weight, volume, and maintenance; and increased controllability, availability,

reliability, and eciency.

The existing steam catapults currently installed on Naval carriers con-

sist of two parallel rows of slotted cylinders in a trough 1.07 m deep, 1.42

m wide, and 101.68 m long, located directly below the ight deck. Pistons

within these cylinders connect to the shuttle which tows the aircraft. The

steam pressure forces the pistons forward, towing the shuttle and aircraft at

ever increasing speed until takeo is achieved. While the catapult has many

years of operation in the eet, there are many drawbacks inherent in the

steam system. The foremost deciency is that the catapult operates without

11

Figure 3.1: Steam catapult being used for Launching a jet from a naval aircraft

carrier

feedback control. With no feedback, there often occur large transients in tow

force that can damage or reduce the life of the airframe. Also, extra force is

always added due to the unpredictability of the steam system. This tends to

unnecessarily overstress the airframe. Even if a closed loop control system

was added to the steam catapult, it would have to be highly complex to sig-

nicantly reduce the thrust transients to a reasonable level. Other drawbacks

to the steam catapult include a high volume of 1133 m3, and a weight of 486

metric tons. Most of this is top-side weight that adversely impacts the ship's

stability and righting moment. The large volume allocated to the steam cat-

apult occupies "prime" real estate on the carrier. The steam catapults are

also highly maintenance intensive, inecient (4-6%), and their availability is

low. Another major disadvantage is the present operational energy limit of

the steam catapult, approximately 95 MJ. The need for higher payload ener-

gies will push the steam catapult to be a bigger, bulkier, and more complex

system.

12

The requirements of the EMALS are driven by the aircraft, the carrier,

and the operational requirements of the carrier's airwing. These requirements

are:

Endspeed 28-103 m/s

Max Peak-to-Mean Tow Force Ratio 1.05

Launch Energy 122 MJ

Cycle Time 45 seconds

Weight < 225,000 kg

Volume < 425 m3

Endspeed variation 0 to +l.5 m/s

Table 3.1: EMALS REQUIREMENTS

The present EMALS design centers around a linear synchronous motor,

supplied power from pulsed disk alternators through a cycloconverter. Av-

erage power, obtained from an independent source on the host platform, is

stored kinetically in the rotors of the disk alternators. It is then released

in a 2-3 second pulse during a launch. This high frequency power is fed to

the cycloconverter which acts as a rising voltage, rising frequency source to

the launch motor. The linear synchronous motor takes the power from the

cycloconverter and accelerates the aircraft down the launch stroke, all the

while providing "real time" closed loop control.

A. Disk Alternator

The average power from the prime power is rectied and then fed to in-

verters. With power from the inverters, the four disk alternators operate as

motors and spin up the rotors in the 45 seconds between launches. The disk

alternator is a dual stator, axial eld, permanent magnet machine (see Fig.

3.1). The rotor serves both as the kinetic energy storage component and the

eld source during power generation and is sandwiched between the two sta-

tors. There are two separate windings in the stators, one for motoring and

the other for power generation. The motor windings are placed deeper in

13

the slots for better thermal conduction to the outside casing. The generator

windings are closer to the air gap to reduce the reactance during the pulse

generation. The use of high strength permanent magnets allows for a high

pole pair number, 20, which gives a better utilization of the overall active

area. The rotor is an inconel forging with an inconel hoop for prestress.

The four disk alternators are mounted in a torque frame and are paired in

counter-rotating pairs to reduce the torque and gyroscopic eects. The rotors

operate at a maximum of 6400 rpm and store a total of 121 MJ each. This

gives an energy density of 18.1 KJ/KG, excluding the torque frame.

Figure 3.2: Disk Alternator Cross Section

Each disk alternator is a six phase machine with phase resistance and

reactance of 8.6 m and 10.4 pH, respectively. At max speed, the output of

one of the disk alternators would be 81.6 MW into a matched load. The

frequency of this output is 2133 Hz and drops to 1735 Hz at the end of the

pulse, for a max launch. Machine excitation is provided by the NdBFe 35

MGOe permanent magnets, which are housed in the rotor. These magnets

have a residual induction of 1.05 T at 40oC and create an average working air

gap ux density of 0.976 T, with tooth ux densities approaching 1.7 T. The

stator consists of a radially lotted laminated core with 240 active slots and

liquid cold plate. The maximum back EMF developed is 1122 V. Maximum

output voltage is 1700 V (L-L) peak and current is 6400 A peak per phase.

The disk alternator's overall eciency is 89.3%, with total losses of 127 KW

14

per alternator. This heat transfers out of the disk alternator through a cold

plate on the outside of each stator. The coolant is a WEG mixture with

a ow rate of 151 litres/minute. The average temperature of the copper is

84oC, while the back iron temperature is 61oC.

B. Cycloconverter

The cycloconverter, or power electronics in general, is the pivotal tech-

nology allowing EMALS to become a reality aboard ship. With a 103 m long

motor, power electronics permit ecient operation by turning on only the

coils that can aect the launch at a particular time rather than the entire

motor at once. It also permits EMALS to operate at its most ecient point

at all speeds by allowing for a variable voltage, variable frequency supply.

The cycloconverter is a naturally commutated 34-14 bridge circuit. The out-

put of one bridge is paralleled / seriesed with outputs of other bridges to

attain the power levels required. By paralleling/seriesing the bridge outputs

and not the switches themselves, the design eliminates the current sharing

reactors and the series capacitors. The output of a cycloconverter is 0-644

Hz and 0-1520 V (L-L) the peak current output is 6400 A for a max launch.

The cooling for the switching assembles takes place through liquid cold plates

to which the components are mounted. The medium is de-ionized water at

35oC input, 100 psig max, 1363 litres/minute. This is required to dissipate

528 KW lost in the cycloconverters.

C. Linear Synchronous Motor

The launch motor is a linear synchronous "coilgun", as shown in Fig.

3.2. The trough is the same as the steam catapult trough to allow for back-

t capability. The motor itself is a dual, vertical stator conguration with

the active area facing outwards. The rotor, or carriage, sits over the stators

much like a saddle and protrudes through the ight deck to be attached to

the aircraft. The carriage contains 160 full permanent magnets, the same

type used in the disk alternator, NdBFe. The carriage is restrained in two

axes by rollers. The rollers run in channels welded to the stator frame. This

15

allows both the stator and trough to ex with the ship and the carriage to

follow this exure while maintaining a consistent air gap of 6.35 mm. The

stator consists of 0.640 m long segments, which are 0.686 m high and almost

0.076 m thick. These segments turn on and o as the carriage passes. The

position sense system is based on Hall Eect sensors, much as in today's ro-

tary brushless commutated motors. As can be seen in the gure, the stators

are protected by osetting them from the slot in the ight deck. This is due

to the contaminants, typically jet fuel, nuts, bolts, wrenches, hydraulic oil,

etc., that constantly invade the trough through the slot and could, over time

aect the stators. Between the stators, in an environmentally sealed housing,

are the busbars and the static switches, which are SCRs used to control the

power to the stator segments. The launcher stator is based on the modular

unit called a segment. There are a total of 298 segments, 149 per side, for

the entire launch motor, each 0.640 m long. The segment is wound as a

three phase lap winding with 6 turns per slot and a total of 24 slots. This

translates to 8 poles per segment and P pole pitch of 8 cm. These coils are

epoxied into a slotless stator structure with G10 separating the coil legs. The

slotless stator design keeps the phase inductance low at 18 pH. The phase

resistance is 41 m while the bus resistance is 0.67. The air gap working

ux is 0.896 T with the armature reaction of approximately 0.24 T. At full

thrust, the permanent magnets experience a shear stress of 38 psi. At the

end of the 103 m power stroke, the front of the carriage enters the brake.

This brake consists of shorted stator segments, which act as eddy current

brakes. At the same point in time, the carriage is still covering a number of

active stator segments. Two phases are switched in these segments so that

reverse thrust is initiated to help with the braking force.

With a projected eciency of 70% and peak losses of 13.3 MW in the

stator, active cooling will be necessary. Maximum coil action is 4.36e6 As,

resulting in a maximum copper temperature delta of 118.2oC. The launch

motor has an aluminium cold plate to remove this heat from the attached

stator windings and back iron. The cold plates consist of stainless steel

tubes in an aluminium casting. The peak temperature reaches approximately

155oC and, after cooling for the 45 second cycle time, cools to 75oC. The

16

Figure 3.3: EMALS launch Motor

carriage that houses the permanent magnets will be cooled by convection,

since there will be only slight heating from eddy currents in the carriage

structure and magnets.

3.2 Linear Induction Motor vs. Linear Syn-

chronous Motor

3.2.1 Flexibility to variable and uncertain demand

The LIM-driven transit system has a great degree of exibility to respond to

variable or uncertain demand by adjusting the number and size of vehicles

on a short-term or long-term basis. The ability to add and move vehicles

provides the operator rapid response capability to volatile demand and the

recovery from any o-normal shutdown or schedule deviation. If additional

power is needed to accommodate an upgrade in the system capacity, the

impact to the guideway is almost negligible requiring only the addition of

way-side power electrication and conditioning equipment. To meet opera-

tional requirements, the train control can also be easily adjusted with little, if

any, modication to the civil structures. The LSM lacks exibility to change

system performance. Replacement of ground facilities is necessary to change

17

Figure 3.4: EMALS being tested on a US navy ship

system capacity or its operational mode, which is quite similar to building a

new system. Its active track and power supply installation must be designed

and installed for the highest demand and capacity of the system contem-

plated during the design phase. This may signicantly shorten the useful life

of the system or greatly increase the life-cycle costs if actual demand does

not follow planned usage.

Line operators may experience o-normal schedule delays, interruptions,

or shutdowns due to causes beyond their control or equipment failure. Rapid

recovery of scheduled operation is critical to maintaining ridership. The abil-

ity of the LIM drive to move and stage vehicles on the guideway with moving

block control provides a great amount of exibility to rapidly restore service.

This includes tailoring vehicle congurations for short-term, high-capacity

operation to immediately accommodate the high-demand resulting from any

unscheduled stoppage or deviation from normal scheduled service. The LSM

requires a single vehicle per section of track, and cannot accommodate a surge

in service throughput, unless the system was highly underutilized previously.

18

The required movement of a single vehicle on a xed guideway section greatly

limits the exibility to stage vehicles to respond to o-normal demand pro-

les or incidents.

In the event of a malfunction of the propulsion motor, the speed of recov-

ery of service is very important. In the case of LIM propulsion, the vehicle is

simply moved and replaced. This can be done with the aid of another transit

vehicle or special service vehicle. If the vehicle is LSM powered, it is much

more likely that the track may need time-intensive repair or replacement of

stator winding sections. During that repair and re-qualication testing, the

entire track is out of service. Service vehicles for such incidents may need

to be independently powered, and may be unable to utilize the guideway

structure eectively.

3.2.2 Reliability of operation

Operational reliability of the LSM strongly depends on the detection and

signal transmission system for vehicle position and velocity to ensure that

the magnetic wave generated in the stator winding is synchronous with the

movement of the excitation magnets on the vehicle. Doubly-redundant sys-

tems are required. Reliability of the LIM in a high-vehicle-density operation

of a transportation system is based on existing conventional-rail technologies,

and has been well established, for example, in the Linear Metro system in

Tokyo, Japan.

Although many future transit systems are contemplating driverless oper-

ation, for systems where drivers are determined to be necessary, the human

factors have been well established for the LIM drives. The operators of con-

ventional railways can easily adapt to the new LIM system using much of

their previous experience.

The reliability of the electrical and mechanical components of the linear

drive must be evaluated, and it is very important to obtain duration-test data

from the designed track to fully qualify the reliability of the drive. This infor-

19

mation is compared to corresponding data from previous installations or test

tracks to determine the eects of design, fabrication, or installation process

modications. The larger the database of previous applications and lifetime

testing of a technology, the higher the condence will be in a planned systems

reliability. The application of LIM drives in steel-wheel transit systems and

the historic usage of similar power conditioning equipment in conventional,

rotary drive rails systems provides a signicant experience base for condent

projection of LIM designs to future maglev applications. Although LSM has

been signicantly evaluated at test tracks, the reliability of active tracks and

section switches must be established with duration tests under revenue ser-

vice conditions. Collection of this data is still in progress, and will not be

completed for a few years.

3.2.3 Capital cost

The capital cost for a maglev system is dominated by the cost of the civil

structures including the guideway, and the size of that structure depends on

the loadings, including the weight of the vehicles. To obtain an accurate cost

comparison between the LIM and LSM propulsion methods, a detailed anal-

ysis must be done for a given route and ridership requirements. However,

there are features of each drive system than can be identied which have

signicantly dierent cost elements.

The weight of the vehicle using the LSM drive is expected to be lighter

than one using the LIM since there is little on-board power conditioning

equipment. This would, in principle, reduce the cost of the guideway. How-

ever, from the design experience for the Colorado Urban Maglev Project, the

live load is a small part compared to the dead load weight of the structure

itself, and the weight of the car does not strongly inuence the cost of the

guideway. It is also interesting to note that the 24.3 meter long, LIM-driven

COL-200 vehicle that carries 103 passengers weighs 44 tonne fully loaded,

while the 24.8 meter long, LSM-driven Transrapid vehicle that carries 126

passengers weighs approximately 60 tonnes fully loaded. While the Tran-

srapid vehicle can achieve higher speed, its weight would not decrease if the

20

vehicle were limited to the 200 kph design speed of the COL-200.

The reaction rail structure in the guideway of a LIM-driven vehicle is very

simple with a conducting sheet anchored to steel that serves as back iron for

the motor. The active guideway of the LSM drive includes laminated stator

cores, stator coils, section switches, feeder cables, and signaling system for

synchronization of operation that is much more expensive. The stator coils

and core components must be very rugged to withstand the repeated cycling

of mechanical forces without degradation of insulation, operate for years in

all-weather conditions, and be low cost. As the complexity of the reaction

rail and power distribution of a LIM-driven system is signicantly less than

that for an LSM system, the time required for construction and operational

testing is also considerably shorter. This results in lower overall capital in-

vestments costs.

The number of power converters per unit length of track may be simi-

lar assuming the same number and type of vehicles on that given length of

track. The LIM drive requires only a wayside rectication system to supply

the constant DC voltage to the vehicle on a single or double hot rail from

the wayside distributed utility electric power. However, each vehicle has a

variable-voltage, variable frequency inverter on board to drive the LIM. The

power to each of the LSM guideway stators is also conditioned through rec-

tication to DC and then reformed to 3-phase AC at variable voltage and

frequency, and one inverter is needed per stator section assuming each section

powers a separate vehicle. However, even if the LSM track is not utilized at

full capacity, all the inverters and distribution network are required in the ini-

tial capital investment and all are operated as vehicles use each stator section.

While the LIM drive may have lower energy eciency, power factor, and

feeder voltage, this does not signicantly increase the investment cost com-

pared to the LSM. This is because the LSM has a more complicated converter

station, lower voltage coils, and 3-phase feeder to stators.

Because of the complexity of the LSM active guideway structure and

21

the synchronous operation of a LSM train, the system structure near end

terminals requires more physical space than LIM driven systems which fur-

ther increases investment cost. The mechanical switch from track to track is

larger, and it takes more physical space to transfer LSM vehicles from one

track to another. As every LSM track section requires a converter, transfers

of many vehicles with short headways at slow speed requires more power

converters in these areas, all installed at the time of initial operation.

In the comparison of capital cost between maglev systems based on LIM

and LSM, it is very clear that the capital cost of the guideway for the system

with LSM is very substantially higher than that for the LIM. Conversely,

the capital cost of vehicles for the LIM-driven system is higher than for one

driven with an LSM. While the total capital costs of either the LIM or LSM

may be greater than that for a conventional railway system, the increase of

the LIM-driven system cost above the conventional system cost is certainly

less than the cost increase for an LSM-driven system.

3.2.4 Operational cost

The operational cost for a maglev system has major contributions including

energy and manpower. Again, an accurate cost comparison between the LIM

and LSM propulsion methods requires a detailed analysis for a given route

and ridership requirements. However, there are features of each drive system

than can be identied which can signicantly aect these cost elements.

In general, the higher energy eciency of LSM drives will reduce the

energy cost compared to LIM systems. However, this very much depends on

the design of motor and power supply system. If the section length of the

LSM stator becomes long, the eciency is reduced. The eciency (ratio of

mechanical power to input real power) of the two drives is very similar, but

the power factor (ratio of real power to apparent power) is larger for the LSM.

The load seen by the utility is the real power, and hence, for this case, the

energy usage is the same assuming the same thrust vs. speed proles along

the route. The consequence of the lower power factor for the LIM is the

22

penalty of increased weight of the on-board power conditioning equipment

to deliver the higher apparent power.

23

Chapter 4

Analytical Design

MATLAB is a high-level language and interactive environment for numeri-

cal computation, visualization, and programming. Using MATLAB, you can

analyze data, develop algorithms, and create models and applications. The

language, tools, and built-in math functions enable you to explore multiple

approaches and reach a solution faster than with spreadsheets or traditional

programming languages, such as C/C++ or Java. You can use MATLAB for

a range of applications, including signal processing and communications, im-

age and video processing, control systems, test and measurement, computa-

tional nance, and computational biology. More than a million engineers and

scientists in industry and academia use MATLAB, the language of technical

computing. we will write one program for calculation of DSLIM parameters

so that we can calculate main dimensions and other parameters for dierent

variables like frequency, current density , slot pitch.

24

DESIGN APPROACH

25

26

27

28

29

30

31

Calculated Stator Parameters (MATLAB CODE MAT-LAB RESULT)

clc

m=3; %no of phases

Vl=3300; %stator phase voltage(volt)

V=50; % desired velocity(m/sec)

n=.50; %efficiency

pf=.5; %power factor

s=.05; %slip

f=100; %frequency (HZ)

L=100; %length (m)

Bav=0.36; %average flux density

ac=50000; %ampere conductors

j=25; %current density (A/mm2)

t=0.25; %pole pitch (m)

mass=50; %weight (ton)

q=2; %slot per pole per phase

nc=1; %no of turns per slot

Kw=0.955; %winding factor

dcu=8900; %density of copper

Bymax=1.5; %maximum flux density of yoke

rhoal=2.65*((10)^(-8)); %resistivity of alluminium (ohm*m)

rhoiron=9.71*((10)^(-8)); %resistivity of iron (ohm*m)

rhow=19.27*((10)^(-7)); %resistivity of cu (ohm*m)

disp('synchronous velocity (m/sec)')

Vs=V/(1-s)

disp('accelaration(m/sec2)')

a=[(V*V)/2*L]/10000

disp('Force(KN)')

F=mass*a

32

disp('time(sec)')

time=V/a

disp('output mechaical power(KW)')

Pm=F*V

disp('input power electrical(KW)')

Pin=Pm/n

disp('per phase current(A)')

I=Pin/(3*V*pf)

disp('no of poles')

p=L/t

disp('slot pitch(m)')

sp=(t/m*q)

disp('no of slots')

ns=2*m*sp

disp('slot width(m)')

ws=sp/2

disp('tooth width(m)')

wt=sp/2

disp('no of turns per phase')

N1=nc*p*q

disp('cross sectional area of wire(mm2)')

Awt=I/j

33

disp('cross sectional area of slot(mm2)')

As=(10/7)*Awt

disp('slot height(cm)')

hs=As/ws

disp('current sheet strength')

Jm=(2*1.41*I*m*Kw*nc)/L

%length of end connection lce=?

lce=0.7 %temp val

disp('length of one turn(m)')

lw=2*(ws+lce)

disp('length of Cu wire per phase(m)')

lcu=N1*lw

disp('total length(m)')

Tlw=q*m*lw

disp('volume of copper wire()')

Vcu=Awt*Tlw

disp('weight of copper')

Wcu=Vcu*dcu

Qp=(Bav*L*ws)/(rhoal)

disp('height of yoke')

hy=Qp/(2*Bymax*ws)

disp('Volume of yoke')

34

Vy=L*ws*hy

disp('volume of tooth')

Vtooth=ws*wt*hs

disp('volume of teeth')

Vteeth=m*p*q*Vtooth

disp('volume of iron')

Viron=Vy+Vteeth

disp('weight of iron')

Wiron=rhoiron*Viron

disp('weight of stator')

Wstator=Wiron+Wcu

disp('per phase stator resistance')

R=(rhow*lw)/Awt

gm=0.015

d=0.010

go=gm+d

Y=(4/pi)*((ws/(2*go))*atan(ws/(2*go))-L*sqrt(1+(ws/(2*go))^2));

kc=sp/(sp-Y*go);

ge=kc*go;

ld=(s*(ge/ws))/(s+4*(go/ws));

kp=1;

le=0.3*(3*kp-1);

ls=(hs*(1+3*kp))/(12*ws);

disp('per phase stator slot reactance')

X=(2*pi*4*pi*(10^(-7))*f*((ls*(1+(3/p))+ld)*(ws/q)+le*lce)*N1)/p

35

disp('goodness factor')

G=(2*4*pi*((10)^(-7))*f*(t^2))/(pi*ge*(rhow/d))

wse=ws+go;

Xm=(24*4*pi*(10^(-7))*pi*f*wse*Kw*(N1^2)*t)/((pi^2)*400*ge);

E1=sqrt(2)*pi*f*Qp*Kw*N1

synchronous velocity (m/sec)

Vs =

52.6316

accelaration(m/sec2)

a =

12.5000

Force(KN)

F =

625

time(sec)

time =

36

4output mechaical power(KW)

Pm =

31250

input power electrical(KW)

Pin =

62500

per phase current(A)

I =

833.3333

no of poles

p =

400

slot pitch(m)

sp =

0.1667

no of slots

37

ns =

1

slot width(m)

ws =

0.0833

tooth width(m)

wt =

0.0833

no of turns per phase

N1 =

800

cross sectional area of wire(mm2)

Awt =

33.3333

cross sectional area of slot(mm2)

As =

47.6190

38

slot height(cm)

hs =

571.4286

current sheet strength

Jm =

67.3275

lce =

0.7000

length of one turn(m)

lw =

1.5667

length of Cu wire per phase(m)

lcu =

1.2533e+03

total length(m)

Tlw =

9.4000

39

volume of copper wire()

Vcu =

313.3333

weight of copper

Wcu =

2.7887e+06

Qp =

1.1321e+08

height of yoke

hy =

4.5283e+08

Volume of yoke

Vy =

3.7736e+09

volume of tooth

Vtooth =

40

3.9683

volume of teeth

Vteeth =

9.5238e+03

volume of iron

Viron =

3.7736e+09

weight of iron

Wiron =

366.4160

weight of stator

Wstator =

2.7890e+06

per phase stator resistance

R =

9.0569e-08

gm =

41

0.0150

d =

0.0100

go =

0.0250

per phase stator slot reactance

X =

0.1522

goodness factor

G =

39.2247

E1 =

3.8427e+13

42

Maxwell Design Procedure

Maxwell solves the electromagnetic eld problems by solving Maxwell's equa-

tions in a nite region of space with appropriate boundary conditions and

when necessary with user specied initial conditions in order to obtain a

solution with guaranteed uniqueness.

Methodology

43

Figure 4.1: Maxwell3D Magnetic ux density Plot for a single winding

44

Chapter 5

Conclusion

Electromagnetic motors for both launching and recovery of aircraft

aboard a carrier are now possible due to a myriad of technical advancements.

The advantages of electromagnetic motors are their improved performance

capability over present systems and the resultant reduced weight and

volume because of the high power, force, and energy densities possible.

These savings are especially important on a carrier where they are precious

commodities. In the future Navy, weight and volume may be of even

higher importance as smaller budgets may demand smaller ships, and future

design will require, just as in automobiles and space vehicles, etc., more

performance out of smaller boxes. Electromagnetics oers this advantage.

These systems would also provide the inherent controllability that comes

with electrical machinery allowing for safer, less mechanically stressing

operations. This will lead to extended life of airframes, nose-gear, and

tail-hooks. Most importantly, electromagnetic motors will provide high level

forces and greater eciencies, which will permit the future generations of

heavier, faster aircraft to operate o a carrier. Systems need to be developed

that can produce the necessary performance. Electromagnetics oers a

viable option.

Each of the LIM and LSM type drives has their advantages and disadvantages

for maglev / EMALS propulsion. Although the guideway is more costly for

the LSM, it is the only appropriate choice for high-speed operation (>>250

45

km/h) as the weight penalty of the on-board power conditioning equipment

for the LIM alternative becomes prohibitive at high speed, and the ability to

transfer the high electrical power to the vehicle for LIM propulsion becomes

impractical in this speed regime. At low speeds (250 kph) the LIM drive

has already demonstrated the capability to provide economical, all-weather

propulsion in maglev and steel-wheel transit systems. For speeds on the

order of 200 kph, with high passenger demand and short headways, the issue

is which technology is most cost eective considering the life-cycle of the

installed design.

46

Bibliography

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Klimowski, "Electromagnetic Aircraft Launch System - EMALS", Naval

Air Warfare Center, Aircraft Division, Lakehurst, NJ 08733, IEEE Trans-

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[2] S.A. Nasar and I. Boldea, "Linear Motion Electric Machines", John Wiley

Interscience, New York, 1976.

[3] I. Boldea and S.A. Nasar, "Linear Motion Electromagnetic Systems",

John Wiley Sons, New York, 1985.

[4] J.F. Gieras, "Linear Induction Drives", Oxford University Press, Oxford,

U.K., 1994.

[5] J.F. Gieras, "Linear Synchronous Motors", 2nd edn., CRC Press, Boca

Raton, FL, 2000.

[6] C. Pompermaier, F.J.H. Kalluf, A. Zambonetti, M.V. Ferreira, and I.

Boldea, "Small linear PM oscillatory motor magnetic circuit modelling

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[7] Klaus Heinrich and Rolf Kretzchmar,"Transrapid International", Tran-

srapid Maglev System, eds., Hestra-Verlag, Darmstadt, 1989

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[9] Gorazd Stumberger, Damir Zarko, Mehmet Timur Aydemir, Thomas A.

Lipo, "Design and Comparison of Linear Synchronous Motor and Linear

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48