Magnetic Levitation Train.
General overview:
Magnetic levitation train is also known as Maglev train is a floating train used for land transportation that’s supported by either electromagnetic attraction or repulsion.
Two sorts of maglevs are in commission Electromagnetic suspension (EMS) and electrodynamic suspension (EDS). [1]
How does it work:
These trains float over guideways using the principles of magnets. There isn’t any rail friction, meaning these trains can hit speeds of many miles per hour.
There are three components in a Maglev train system:
1. A large electrical power source
2. Metal coils lining a guideway or track.
3. Large guidance magnets attached to the bottom of the train.
The magnetized coil run along the guideway. [2]
There are three varieties of levitating systems:
· Electromagnetic Suspension
· Electrodynamic Suspension
· Inductrack System
1.Electromagnetic suspension (EMS): It uses the attractive force between magnets present on the train’s sides and underside and on the guideway to levitate the train. In this system, the bottom of the train surrounds a steel guideway. Electromagnets attached to the train’s undercarriage are directed up toward the guideway, which levitates the train by about 1 inch above the guideway. Additional guidance magnets embedded in the train’s body keep it stable during travel.
It is simpler to implement than Electrodynamic Suspension and it maintains levitation at zero speed. The drawbacks are that the system is inherently unstable even though it has guidance magnets. This causes the train to not levitate and come grinding to a halt.
2. Electrodynamic suspension (EDS): uses magnets to repel the train from the guideway rather than attract them. The electromagnets used are super-cooled and superconducting. This type of electromagnet can conduct electricity even after the electric current supply is cut off. Cooling the coils to a very low temperature also helps to save essential energy.
This type of levitation helps maintain stability even at high speeds. Maintaining correct distance between train and guideway is not a major concern. The main drawback is that sufficient speed needs to be built up in order for the train to levitate. Also, this system is complex and expensive.
3. Inductrack Levitating system: The Inductrack is a newer type of levitating system that uses permanent room-temperature magnets to produce the magnetic fields instead of powered electromagnets or cooled superconducting magnets. A power source is used to accelerate the train only until it begins to levitate. In case of power failure, the train can slow down gradually and stop on its auxiliary wheels.
The track contains electrically shorted circuits containing insulated wire in an array. When the train moves, a magnetic field repels the magnets which causes it to levitate. The magnets are configured so that the intensity of the magnetic field concentrates above the array rather than below it. This helps to create enough levitating force.
[3]
The magnets employed are once again superconducting here.
Once the train is levitated, power is supplied to the coils within the guideway walls to form a novel system of magnetic fields that pull and push the train along the guideway. The electrical current supplied to the coils within the guideway walls is alternating to change the polarity of the magnetized coils after every half cycle. This variation in polarity causes the magnetic field in front of the train to drag the vehicle forward, while the magnetic field behind the train adds more forward thrust.
Propulsion:
Maglev uses an electrical linear motor for propulsion. The stator is laid flat and therefore the rotor rests above it. Rather than a rotating magnetic flux, the stator generates a field that travels down its length.
In a linear motor, the stator is commonly called as the ‘primary’ and the rotor as the ‘secondary’. In maglev trains, the secondary is attached to the underside of the train cars, and thus, the primary is in the guideway. So, a field is sent down the guideway and it pulls the train along after it. However, in this configuration, the secondary always lags behind the moving field in the primary. This ends up in speed loss. In a Linear Synchronous Motor (LSM), this lag is removed by attaching permanent magnets to the secondary. Since, the secondary is now producing its own stationary magnetic field, it travels down the primary in sync with the moving field. Hence, due to increased efficiency, LSMs are the preferred choice.
The aerodynamic shape of the Maglev train allows it to reach speeds of up to 500 km/hr.
Guidance:
Repulsive magnetic forces help in achieving guidance in high-speed maglev trains. There are two sorts of guidance namely Trans Rapid guidance and MLX guidance used for Maglev trains.
In the Trans Rapid guidance, two electromagnetic rails are placed on the train which face either side of the guideway.
In the MLX, guidance is integrated with the levitation system. The levitation rails on either side of the train are connected to each other to ensures that the train stays on course. [4]
Purpose:
These trains have a high speed. Because the trains rarely touch the track, there’s far less noise and vibration than traditional trains. Due to less friction and mechanical vibrations fewer mechanical breakdowns will tend to occur, meaning that maglev trains are less likely to encounter weather-related delays.
The Maglev train can reach speeds of about 500 km/hr and some even up to 601 km/hr. These speeds will allow for faster mass and efficient mass transport.[5]
Bibliography
[1] https://www.britannica.com/
[2] https://science.howstuffworks.com/
