Electromagnetic propulsion uses the concepts and applications of electromagnets. Technologies that make use of such applications include magnetic levitation technologies, including maglev trains, railguns, and even electromagnetic motors to some degree (though more use is made of the motor principle derived from electromagnets).
Electromagnetic propulsion technology added a big value to the transport technology within our society and future development.
Nowadays different countries use different technologies for their transport systems. The technology highlighted a new mode of transport which is Maglev (Magnetic Levitation). There are different types of Maglev.
The new maglev system highlights a number of advantages for the future transport system technology. With this system there is no need for the wheels anymore which means no mechanical friction between the wheels and the track, since the vehicles are lifted by a magnetic repulsion and propelled by powerful magnets attached to the vehicle.
Further, this points out several advantages in terms of speed, comfort and reliability that this system offers. But the question why is it still not used by more countries?
One of the main reasons which still stop countries from adopting the high-speed-maglev system is the costs and the large payback period.
On the other hand many countries have adopted high-speed steel-wheel technology without taking the risk and investment in the new technology.
However the demand for faster transportation and more punctuality is gradually increasing which gives more challenge for the researchers and engineers to satisfy this demand. Further this essay will highlight the technical aspects of this technology and its limitation.
The rise in civilization may be closely tied to improvement in power development techniques in various fields of our day-to-day life.The mode of transportation which started its evolution from one of the mile stones of humane invention, the wheels; has reached its summit, the mode without the same. Although the growth of technology is sometime unimaginable it always makes a breakthrough for something more sophisticated. Engines which were / are considered as the pivot of transportation even are being surmounted. Another remarkable sighting, the electromagnetism, makes this possible.
The discovery of Electromagnetism, a property of materials under the magnetic field, can be seen as another important milestone in the history of technological evolution. The underlying theory of electromagnetism is that a varying magnetic field generates electric field. This property of electric and magnetic fields are found to mutually dependant. That is magnetic field can also be generated by varying electric fields. This led the way to another important discovery called electromagnetic propulsion. In electromagnetic propulsion a diamagnetic metallic torus is inserted into a changing electric field. The agitated atoms inside the torus produce a magnetic field directly proportional to the intensity of the varying electric field in the opposite direction.
The principle of electromagnetic propulsion has paved the way for the invention of the new means of transportation, obviously easier, reliable, and potentially less harmful “MAGLEV” or Magnetic Levitation. The principle has made transportation possible in many places for trains although the process of research still moves on and wheel – less skating boards; the most recent face of MAGLEV.
The first Maglev system was proposed and published by US in 1966. Shanghai uses the Trans rapid maglev trains which use the technology electromagnetic propulsion.
There are two types of this technology with wheels and without wheels, where maglev is without wheels.
On the other hand Japan uses superconducting maglev with LSM (Linear Synchronous Motor) propulsion.
Maglev has the power of changing the society in terms of transportation because of the speed and the safety it offers. It travels at similar speed of the planes but with much bigger volume and lower price. With maglev vehicle we would be able to provide most of the world with resources at a very fast speed and with low costs.
Maglev vehicles are a high speed vehicles lifted by magnetic repulsion and propelled along an elevated guide way by powerful magnets attached to the vehicle. These vehicles don’t need engines to run, so no fuel consumption. The vehicles are magnetically propelled by electric power fed to the guide located on the guideway.
There are four main points which establish its importance.
- Maglev can move people with bigger volume and with much less costs. Its shelf life is quite high because there is no mechanical contact between the vehicle and the guideway and the weight is not anymore concentrated in the wheels; however it is now spread across the vehicle. The guideway would last for 50 years or more.
- It doesn’t need engines; therefore it is very energy efficient. It consumes electricity instead of burning oil. At 300 miles per hour Maglev consumes only 0.4 mega joules per passenger mile compared to 4 mega joules for oil fuel.
- Maglev is very environmentally friendly because it doesn’t release CO2 even if it uses electricity from coal or natural-gas-fired power plants. It has very high energy efficiency.
Furthermore it is much quite than planes, trucks or automobiles and has narrow beam guideway which uses lest space on the ground.
- Maglev has a safety advantages over the high way vehicles, trains and aeroplanes. The electrical power controls the speed of the vehicle and it automatically adjust so there is no possibility of collision between vehicles on the guideway. (Powell and Danby, 2007)
How does maglev work?
As mentioned before, Maglev works on the principle of electromagnetic propulsion. There are two fundamental types of technology that are presently used in running maglev. They are the Electromagnetic Suspension technology (EMS) and Electro Dynamic Suspension technology (EDS). Other types of technologies like the Magneto Dynamic Suspension are also being used, but are still in the initial stages. In general terms in EMS technology the electromagnets in the train repel away from the steel rail tracks which are made magnetically conductive. In the EDS technology, on the other hand, the track and the train is provided with electromagnets which pushes the train forward.
Electromagnetic Suspension Technology
In EMS technology electromagnets are attached to the train. These electromagnets are oriented towards the rail from under. When magnetic force is applied to the steel rail, the train levitates on the rail and moves forward. This technology has an advantage over EDS technology in the fact that EMS trains can be used to run at all speeds. The EDS technology works only at a minimum speed of 30 kilometres per hour. However, a major drawback is that the technology requires a complex system of running and feedback mechanisms.
Electro Dynamic Suspension Technology
In the EDS technology a magnetic field is made to exert by both the train and the rail. The repulsive forces exerted by the magnetic field of the train and the rail cause the train to levitate. Array of permanent magnets and / or electromagnets are used for EDS technology. A major advantage is that trains using EDS technology are more stable than the ones using EMS technology and hence it does not require complex feedback mechanisms like the EMS technology. But since the trains need to keep a speed higher than 30 KM/Hr, these trains require wheels to support the train till it reaches a minimum speed. The system also creates a drag when operating in slow speeds due to the repulsive forces. However, this drag is now used as an advantage by using it as a reactionary system while the train is moving in slow speeds.
The first Maglev system was based on carrying superconducting magnets that induced current which interacted with the superconducting magnets mounted on the vehicle to levitate the vehicle above the guideway.
The magnetic force works automatically to control the speed of the vehicle so it stays stable and hold on the guideway. It doesn’t get affected from external forces such as wind or centrifugal force on curves. Because the levitation force lifts the vehicle by increasing the force to prevent contact and decrease it if an external force hits the vehicle to keep it on track.
Maglev is very powerful and has zero electrical resistance. The power consumption is zero except a very small amount goes to the refrigerators to control the temperature.
After the first publication in 1966 Maglev programs started in the US, Japan, Germany and other countries. In the early 1970 the US stopped developing their program however Japan and Germany continued their development programs.
Now Japan railway runs on a maglev at top speed 361 mph on their 20 Km guideway in Yamanashi. Superconducting Maglev has a basic feature with their U shaped guideway. The side walls of the vehicle have a second set of aluminium loops which is called Linear Synchronous Motor (LSM). These LSM loops are connected to a power line through electromagnetic switches which propel magnetically the vehicle along the guideway.
The AC current in the LSM loops pushes on the superconducting loops attached to the vehicle causing it to move along the guideway at a constant speed which is determined by the frequency of the current in the LSM loops.
On the other hand Germany has followed a different way to their Maglev system. The German transrapid system uses conventional room temperature electromagnets instead of superconducting maglev.
The superconducting the repulsive force automatically controls the gap between the vehicle and the guideway. If the vehicle gets closer to the guideway then the repulsive force push it away to maintain stability. However in the electromagnetic maglev the when the vehicle gets closer to the guideway the magnetic attractive force becomes greater automatically pulling it closer to the guideway. This would create instability in the vehicle. To solve this problem they use servo control system that automatically adjusts the current in the LSM loops to maintain stability by maintaining the gap between the vehicle electromagnets and the guideway. (Powell and Danby, 2007)
What are the advantages and disadvantages of high speed Maglev? ( Liu & Sun & Wei, 2006)
When the wheel-rail system started in the 1825 it took 140 years to achieve 200Km/h operation speed and then it took another 30 years to achieve 300Km/h which is nearly close to the speed limit because of the mechanical friction between the wheels and the rail.
But with the Maglev high speed system there is no mechanical friction because there are no wheels and no mechanical contact. This helps to increase the speed which results in faster more
The main advantages of high speed Maglev are:
- High speed
It is the only ground transport vehicle which can travel at a speed of 500Km/h
- High accelerating rates, High climbing capability and small curve radii
Because there are no wheels and no friction the electric power determines the acceleration rate, climbing rate and curve radii rather than the friction between the wheels and the railway as in the ordinary trains. The Shanghai vehicle accelerates from 0 to 431Km/h in 3 minutes only. The climbing rate in a maglev system is 10% comparing with 4% for the trains with wheels. The radii of the maglev system are less than the high speed wheel-rail system, which means reduction in the rout for the journeys.
- Safe and Comfortable Riding
In terms of safety there is no possibility of accident to occur within the maglev system because of the mechanical and electrical structure of the maglev system. Also because of the contactless between the vehicle and the guideway the vibration is very small which made the journey much comfortable and calmer. The best safety and reliability evidence of the maglev system is the Shanghai system because it has 99.83% usable rate and 99.57% operating punctual rate.
- Little Maintenance
As a key to reduce the costs of operation and investment is less maintenance work. Within the maglev system there is no mechanical parts to be repaired or replaced, however electronic devices is more reliable and less likely to get damaged especially with continuous improvement on this sector. This should make the maintenance much simpler and less time consuming.
- Friendly to Environment
Maglev has no fuel emission. And less soil needed for the guideway as there will be elevated guideway.
- Higher Efficiency
The only resistances faced by maglev trains are air resistance and electromagnetic drag as there are no frictional forces between the tracks and the train. This makes maglev more power efficient than normal electric trains.
- Lower noise
The maglev trains lacks noise produced by the friction between the tracks and the wheels. The noise caused by the trains is mainly due to the displaced air when the maglev moves at high speed. This makes it a much less noisier mode of transportation than conventional trains.
However this type of transportation is not free from limitations. The following are some of the shortcomings of Maglev trains.
- A major drawback is the lack of backward compatibility by maglev trains. These types of trains cannot be used on conventional railway tracks. Hence the entire infrastructure for using this mode of transportation has to be built. Also the infrastructures required for running maglev trains are highly expensive. A rapid transformation from conventional railway system to maglev system is not easily possible.
- Another issue is in the design field of these trains. These trains are designed to be less heavy than conventional trains for making it more power efficient. Also less reliability of magnetic fields at high temperatures also poses some design constraints.
- Fast responding highly efficient control systems are required for operating this high speed trains. It is this high speed control mechanisms that actually maintain the stability of the maglev trains. But the introduction of new technologies, manufacturing techniques and invention of newer alloys are helping to eliminate the disadvantages posed by maglev trains.
The pictures below show the high-speed steel-wheel technology and electromagnetic suspension technology.
The electric power is supplied by the overhead lines transmitted by an articulated arm as shown on the picture.
This high speed train must run on wide radii.
These trains can run on the normal track but there is a limit for their speed especially where there is crossing with the public.
The EMS train chassis wraps around the guideway. Upward-facing levitation magnets pull the train upward toward the track.
Challenges Facing Maglev
Like any new innovation MAGLEV also being at the initial stages of growth faces a lot of hurdles. Although Maglev has passed through a basic research and engineering development programs, it still faces a lot of technical and economical problems in construction which is to be rectified. To bring the advantages of Maglev it should be operating along large distances to bring down the travel time.
Further the cost is much higher than the wheel railway technology and moreover the variety of landscape features like high winds, steeps and dusts make hindrances for setting up the infrastructure. There are many R&D work on the maglev technology to reduce the costs and improve it, but it is still in the idea or design phase. ( Liu & Sun & Wei, 2006). The geographical feature depends a lot on setting up the infrastructure and this in turn shoots up the cost too. When compared to the convetional railway system the CAPEX and OPEX for MAGLEV technology is too high.
According to the rail expert Christian Wolmar and the rail network in Britain the Maglev has too many negatives. They say there are three main problems with maglev which is:
- It is not a tried and tested technology
- It cannot run of normal lines, so they would have to build a new maglev line, which would be massively expensive.
- Because it is too expensive then it will need a massive passenger numbers to payback the costs.
- Like any operational system the OPEX is still yet unknown because of the lacking of wide functionality.
- The safety certification of the technology is still under shade, which is expected to happen taking more than a couple of years.
- Although working of the MAGLEV trains are said to be quite they produce very high frequency sounds on higher speeds
- The high speed trains could go for a fast run on the high speed line, and come off it for the rest of the journey; but Maglev trains wouldn’t be able to do that, they would be limited to where maglev lines run.
Shanghai maglev railway cost £33m per mile. These lines are more expensive because of the complication involved in the magnets system.
Within the UK the network railway had to stick to the traditional railway because of their concerns on the long term reliability of maglev systems since maglev tracks cannot be used by traditional trains and vice versa. (Smale, 2006).
As a conclusion of the electromagnetic propulsion technology, it is clearly now it is part of many countries transport systems. Some countries use the high-speed steel-wheel system and others use the electromagnetic system.
Both of the systems have advantages and disadvantages. The increasing demand from people on fast and punctual transport gives the researchers and engineers the determination to satisfy the needs of the society.
The need for the electromagnetic system is more than ever. As a result of the lines in China and Japan the advantages are known. Even there is still a big risk because of the cost and the reliability, but I believe that the maglev system is the way forward in the transport technology and will be taking a big part in the future development.
Liu & Sun & Wei. The Developmental Status and Future Prospects of Maglev Technology. China: Institute of Electrical Engineering, 2006. Print.
Powell and Danby. Maglev: Transport Mode. For the 21st Century. Germany: EIR Science & Technology, 2007. Print.
Quain, J. Super Trains: Plans to Fix U.S. Rail Could End Road & Sky Gridlock. Popular Machines. 2007. Web.
Smale, W. Should UK trains look to magnets? BBC News, 2006. Web.