improvement of thrust force ripple in ultra high speed train

Introduction • Why maglev trains needeed ? They consume less energy. Move faster than normal trains because they are not affected by

ground friction Depleting fuel resources

• High speed trains are solution for these problems and Maglev trains are even better solution

• Maglev trains are based on maglev principle and they are non contact , friction less , high speed with low maintenance cost trains.

Basic Principle of Maglev Trains

Maglev trains have to perform the following functions to operate in high speeds

1.Leviation

2.Propulsion

3.Lateral Guidance

Principle of PropulsionA linear electric motor (LEM) is a mechanism which converts electrical

energy directly into linear motion without employing any intervening rotary components

Linear Induction Motor (LIM) is basically a rotating squirrel cage induction motor opened out flat

Instead of producing rotary torque from a cylindrical machine it produces linear force from a flat one.

LIM thrusts vary from just a few to thousands of Newtons , depending mainly on the size and rating

Speeds vary from zero to many meters per second and are determined by design and supply frequency

• A conventional rotary synchronous motor , is made up of two rings of alternating north and south magnetic poles.

• The outer ring (the stator) is stationary, while the inner one (the rotor) is free to rotate about a shaft.

• The polarity of the magnets on one (either) of these rings is fixed; this element is known as the field.

o The magnets of the other ring, the armature, change their polarity in response to an applied alternating current.

• Attractive forces between unlike magnetic poles pull each element of the rotor toward the corresponding element of the stator.

• Just as the two poles are coming into alignment, the polarity of the armature magnets is reversed, resulting in a repulsive force that keeps the motor turning in the same direction.

• The armature poles are then reversed again, and the motor turns at a constant speed in synchronism with the alternating current which causes the change in polarity

DRAWBACKS OF USING LIM

• The main draw back of this type of maglev train is its speed limit i.e. upto 500 km/hr Because of air resistance and aerodynamic noise, greater speeds are difficult to reach.

Introduction of ultra high speed train• To overcome this speed limitation ,Switzerland

and South Korea came up with the concept of the tube train , an ultra-high-speed tube train adopting the linear synchronous motor (LSM).

• the LSM is responsible for both propulsion and levitation of the train.

• It runs through a partial vacuum tube.• It attains speed of about 700 km/hr

PROBLEM FACED BY TUBE TRAIN

• At a speed of 700 km/hr a large thrust force ripple causes vibration, noise and severe levitation disturbance during the train operation.

FIG : Characteristic curves of the running resistance and the required tractionforce by the speed variety of the 700 km/h ultra-high-speed tube train in thepartial vacuum tunnel

WOUND-TYPE FIELD MAGNET DESIGN IN LSM

An efficient design model is presented that

considers the future manufacturability of the wound-type field magnet of the LSM. In this ne design auxiliary teeth were added to make the closed magnetic path at the two end poles of the field magnet core .

Fig: Newly designed wound-type field magnet model of LSM for the 700 km/h ultra-high-speed tube train. (a) Conventional wound-type field magnet model. (b) Newly designed wound-type field magnet model. (c) 3-D image of the LSM with 1 module (10 poles) of field magnet.

IMPROVEMENT OF THRUST FORCE

MPSS AND TFM METHOD The Conventional PSS Method Definition of the MPSS Method MPSS and TFM Methods

The Conventional PSS Method

• The phase set shift (PSS) method is used to reduce the thrust force ripple of the LSM for the industrial transport system.

• Used where moving armature and a stationary permanent magnet track is present for a short-distance operation.

Definition of the MPSS Method

• Module phase set shift(MPSS) method is Modified form of the general PSS method.

• It is a long field magnet-type that consists of 20 modules per 1 field magnet array and 10 poles for 1 module.

Improvement of Thrust Force using MPSSand TFM Methods

• The thrust force mapping (TFM) method is proposed with the MPSS method for the precise calculation of the proportion force of all the LSM modules.

• The MPSS ratio increased , the force ripple decreased, but at the same time, the average thrust force decreased

Fig : Average force ripple characteristics of each of the 20 LSM field magnet modules by variations in the MPSS ratio. (a) Average force ripple characteristics of each LSM field magnet module. (b) Average force ripple reduction of each LSM field magnet module.

CONCLUSION

• To reduce the thrust force ripple, the thrust force characteristic was improved by using the MPSS method. Furthermore, for the precise calculation of the total thrust force of all the LSM modules, the TFM method, along with the MPSS method, was presented.