– Magnetic induction Iine – Magnetic flux density – Magnetic flux
9
Electromagnetism (I)
Right-hand screw rule (Ampere's rule)
10
Electromagnetism (II)
Faraday's law of induction
Grade
80~100/1000 30~50/1000
Curve
30 [m] in radius 150 [m] in radius
Operating speed
Up to 500 km/h Below 300 km/h
6
Characteristics
Not suitable for freight Less susceptible for icy conditions Environment friendly Good acceleration and deceleration Difficult for switching or branching off Expensive for construction Dangerous when electricity supply is interrupted
Problems of
– Air services – Automobiles
– Conventional trains
3
Maglev
Magnetic levitation train Levitated and propelled using electromagnetism
Guideway Elevated track Arm
Lenz’s law
dB
dt
– An induced electromotive force (EMF) always gives rise to a current whose magnetic field opposes the original change in magnetic flux
4
History
First patent by Hermann Kemper of Germany in 1934
Quickening period of the 1960s Maturity of the 1970s – 1980s Test period of the 1990s Practical public service in 2003 Main research done by Germany and Japan
11
Electromagnetism (III)
Right-hand rule Left-hand rule
12
Electrical engineering
Rectifier Inverter Chopper
Function
AC -> DC DC -> AC DC -> DC
Typical Circuit
– Magnetic attraction force – Air gap about 10 mm – Need precise control – Easier than EDS technically – Can levitate in zero or low speeds (backup battery)
5
Comparison
Maglev
Wheel-on-Rail
Noise
60 ~ 65 [dB] 75 ~ 80 [dB]
Safety
No derailment Derails from a minor and slipping defect
Maintenance Very little
Perioerview of Maglev 2. Fundamentals 3. Traction system and subsystems 4. Shanghai Maglev
8
Magnetism
Magnetism arises from moving charges Measurement
16
One type
Classification
– Permanent Magnet (PM) – Superconducting Magnet (SCM)
17
Another type
18
EMS
Electromagnetic suspension
Coils on the guideway
Characteristics
14
Subsystems
Levitation Guidance Propulsion Braking Energy supply
15
EDS
Electrodynamic suspension Characteristics
– Magnetic repulsive force – Air gap about 100 mm – Suitable for high-speed operation – Cannot levitate below 100 km/h – Need rubber tires
磁悬浮列车牵引系统
Maglev Traction System
Content
1. Overview of Maglev 2. Fundamentals 3. Traction system and subsystems 4. Shanghai Maglev
2
Background
Changes
– Increase of population – Urbanization – Quality of life
Bridge rectifier PWM inverter Buck/boost circuit
Transformer AC -> AC
-
VFD
AC -> AC
Rectifier + Filter + Inverter
13
Content
1. Overview of Maglev 2. Fundamentals 3. Traction system and subsystems 4. Shanghai Maglev