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PREFACE
This book presents a totally new and unique approach to the design of a Maglev system that may be utilized for high-speed ground transportation as well as for launching heavy objects into space. The system proposed in this book is distinguished from any other Maglev type in that it exploits the interaction rare of earth permanent magnets with steel cores
The Maglev high-speed ground transportation system
A Maglev transportation system is designated for the transportation of passengers at a speed of 500 km/h and more. It must be safe and inexpensive and not contaminate the environment. Research conducted in different countries of the world over the past 40 years established the outline and structure of future systems:
Magnetic Suspension together with Propulsion Motor must insure stable motion of the vehicle along an assigned track at a given speed. The Power System must insure uninterrupted power supply with three-phased current. Technical requirements for different parts of the Maglev are as follows: (a) The Maglev vehicle should fly at a speed up to 150 m/s along a guideway with a small air gap between it and the guideway; (b) its track is determined by the surfaces of the guideway; (c) vehicle speed is determined by the form of the track and the distribution of stop stations. The resistance forces of the air are measured in tons. To overcome these the vehicle expends megawatts of power. The power is transferred to the vehicle through the magnetic field in the air gap by Lorentz's force exactly as occurs in an ordinary rotating three-phased synchronous motor. In the Propulsion Motor the rotor magnets' unwrapped (unrolled) poles are installed on each vehicle, while the stator's three-phased winding is common for all vehicles and extended along the whole track. The winding is powered by three-phased sinusoidal current. A traveling wave of current arises in the winding, interacting with the magnetic field produced by the rotor's magnets and propelling the vehicle. A part of Maglev guideway between two adjacent stations involve acceleration and deceleration sections and may have ascents, descents, and curvatures. A flying vehicle is affected by external forces such as gravity, front air resistance, lateral wind pressure and also considerable centrifugal forces on curvatures. All these forces, except for gravity, may arise unexpectedly and vary considerably. At the same time at each point of its track the vehicle must strictly follow an assigned trajectory and fly at an assigned speed. If a deviation of hundred meters from its track is admissible for an aircraft, a deviation of a magnetically suspended vehicle from its track even by 0.0l m leads to disaster. Under these conditions the control of a vehicle speed and its deviations from the guiding surfaces of the guideway pose the following problems: 1. how to insure the safe flight of a vehicle moving at a high speed at a distance less than 0.01 m from guideway surfaces; 2. how to ensure the stable functioning of a linear synchronous propulsion motor at vehicle speeds continuously varying from 25 to 150 m/s. Self-regulation of both Magnetic suspension and Propulsion motor would obviously be an optimal solution. Self-regulation for Maglev means that it should be capable of instant and faultless reaction to any deflection of the vehicle speed from its given value and any deviation from its position on a projected trajectory by producing internal magnetic stabilizing forces sufficient to eliminate such variations. Amlev (the proposed American variant of Maglev) resolves the above problems in an innovative fashion. It is based on permanent magnets and steel cores and utilizes the most intensive way of producing magnetic forces to directly perform all operational functions. Its Magnetic Suspension and Propulsion Motor are both self-regulating, and its Power system is much simpler, more reliable, and cheaper that existing systems of either Electro-Dynamic Suspension (EDS) or Electro-Magnetic Suspension (EMS) Maglev. A detailed description of Amlev is provided in Chapters 2, 3 and 4. As stated above, Amlev consists of three components essentially different from those of EMS and EDS: · Magneto-Dynamic Suspension – MDS; · a Linear Motor also based on permanent magnets – PMLM (permanent-magnet linear motor); · a conventional power system. The sources of magnetic field are rare-earth permanent magnets Crumax and steel cores. Amlev stator winding is powered by sinusoidal current of constant frequency. Magnetic fields, magnetic fluxes and internal forces (stabilizing and destabilizing) are calculated analytically exploiting conformal mapping transformation (computer program is attached).
Advantages of the magneto-dynamic system.
1. As already stated, the magnetic field in an MDS system is produced by the magnetization of soft electrical steel by rare-earth permanent magnets. At the present time this is the most effective physical process for producing magnetic forces. This actually makes it possible to achieve (for a vehicle of length 22 m) a stiffness of the stabilizing force (which is the main qualitative index of a suspension system) of up to 3×107 N/m. This exceeds by at least 10 times maximum stiffness of stabilizing force in the electro-dynamic type of suspension, which employs superconductive magnets. 2. The potential energy of the magnetic field produced by the MDS system has a strict local minimum along the whole guideway length. Therefore, any shift from the set trajectory of the vehicle flying with the speed V>25 m/s causes stabilizing forces tending to bring it back to its track.
In addition the MDS system has other advantages:
3. Self-Regulation. 4. Safety: (a) failure of any auxiliary system in either guideway or vehicle, (such as power system, automatic control system, etc.) cannot lead to collapse; at any shutdown the vehicle will continue its flight, gradually lowering its speed and then emergency supporting wheels will be pulled out to stop it. (b) Magnetic fields of the permanent magnets are closed by the iron cores and are safe for passengers. 5. Simple Construction and Light Weight of the Vehicle. 6. Use of permanent magnets: (a) Permanent magnets are significantly less expensive in both manufacture and operation, can be made in small forms of any shape, and do not loose their magnetization and levitation ability over time. (b) They do not require current, super cooling, a fast-response control system, or a heavy bulky source of energy placed inside the vehicle.
Advantages of the permanent-magnet linear motor
The PMLM is self-regulating. The creation of a self-regulating propulsion motor in either EMS or EDS Maglev has never even been attempted. The stator winding turns in these systems were uniformly laid along the guideway and the rotor magnets installed on the vehicle were of constant length. Under such conditions rotor magnetic flux is limited and propulsion force is proportional to stator winding current. PM speed and propulsion force regulation are provided by electronic converters and inverters of current frequency located along the entire guideway and controlled by servo control systems. In addition the EMS and EDS Maglev PM stator is powered according to a scheme employing the following components: (a) a high voltage current system of commercial frequency; (b) step-down transformer substations installed along the stator winding parts; (c) electronic alternative-to-direct-current converters; (d) electronic inverters of direct current in three-phase alternating current of regulated frequency, capacity, and voltage; (e) servo control systems distributed along the entire track and controlling vehicle speed via radio and electronic converters and inverters located at the powering stations. All this leads to tremendous complication of power system and lowering its reliability. Thus, neither EMS nor EDS Maglev are capable of self-regulation. The proposed design and mode of operation of PMLM are different from and superior to other linear synchronous motors used in high speed ground transportation (HSGT) systems with magnetic suspension. Its advantages include: 1. All the vehicles employing PMLM can move simultaneously with different speeds but they are supplied with power from three-phase current of constant frequency. There is no need in electronic generators for regulated frequency or voltage for powering each single vehicle or train. Nor is there a need for an automatic servo control for tracking the motion of each single vehicle at each point of its track or for regulation of its speed at each its track fragment. In addition, vehicles may depart at brief intervals (about a minute). A collision of vehicles in motion is impossible. 2. The speed and force propelling each vehicle change automatically following an optimal program calculated just once and then incorporated into design of the PMLM stator by distributing stator winding turn lengths, and capacities of feeding transformer substation. 3. This type of speed regulation prevents the rotor from falling out of synchronism and ensures vehicular flight stability. 4. A ferromagnetic yoke in the PMLM considerably increases magnetic field intensity in the rotor working gap. However, the PMLM does not have drawbacks caused by ferromagnetic cores in the other types of linear synchronous motors because: (a) there is no destabilizing force attracting the rotor magnets to the stator winding cores; (b) the rotor yoke does not increase inductance of the stator winding. Hence, the PMLM has a high power factor of input power; (c) there is no direct armature reaction in the PMLM, and, therefore, the electromagnetic process yields to accurate analysis and, consequently, optimization of its design.
Simplified variant of Amlev and its advantages
In Chapter 4 (paragraph 4.2) a simplified version of Amlev is considered that is applied to ground transportation with speeds not exceeding 150 m/s (540 km/h). It employs a levitation system only to support vehicle weight. Rather than horizontally guide the MDS magnetic unit, it is supplied by pairs of horizontal wheels. This variant exploits the same Permanent-Magnet Linear Motor. The main peculiarity of the mentioned wheel assembly is that the wheels of each pair roll both on a side wall of the guiding channel in special paths. The simplified Amlev is much less expensive that Amlev itself because of it does not employ guide units, and construction of its supporting units is much simpler than those of Amlev. In addition, the technology for manufacturing aluminum screens is much simpler and cheaper. Simplified Amlev also has indisputable advantages over high-speed railway transportation: High-speed rail transportation can develop speeds up to 400 km/h, maximum speed being dictated by the reliability of the contact devices powering the vehicle and also by wear on its wheels. In contrast, power supply in S. Amlev is noncontacting and is performed by Lorentz force via the air gap. Moreover its horizontal wheels do not bear the weight of the vehicle. They only compensate the horizontal destabilizing force, which can be reduced to a value 8 ÷ 10 times less than vehicle weight. (see 4.2-2). Therefore the horizontal wheels are much lighter than those in high-speed rail transportation.
Gas-gun accelerator based on passive magneto-dynamic suspension
There are possibilities for using passive levitation systems combined with combustive gases for acceleration and repeated launching of heavy objects into outer space. We propose to use the magneto-dynamic suspension system (MDS) for this purpose. The object is stably suspended in a magnetic field and flies within a launch tube without touching the tube’s walls, that is, without friction. A description of this type of Gas-Gun accelerator is presented in Chapter 4 (Paragraph 4.3). The Gas Gun Acceleration system must ensure the stable equilibrium of two bodies only: an immovable stator (tube) and a flying object with a levitator. To attain this effect, levitator magnets and stator cores are situated in a specific pattern. Interaction between the levitator magnets and stator steel cores produces stabilizing forces. In order to impart the maximum stability to the flying vehicle, the torques of these forces must be as large as possible. Thus, the magnets on the cylindrical object must be attached on both sides of its diameter along the entire body Correspondingly, the stator cores must be located along the launching tube and be parallel to flying magnets within a small distance from them. The object has one degree of freedom directed along the Axis OX. The shapes of both MDS magnets and cores must be cylindrical with their generatrices parallel to the Axis OX of the launching tube. The equilibrium of the levitator flying along the Axis OX supposes that the shape of levitator and stator parts are symmetrical with respect to the plane XOZ. The levitator together with the object are in homogenous gravity. Therefore in addition MDS should compensate for its own weight. As in an ordinary cannon, a heavy cylindrical object is accelerated along the launch tube by gas under high pressure. The latest developments in Gas Gun design employ the use of continuous injection of combustive gas through multiple ports along thе tube as the object passes and burning gas fills the space behind the object. This reduces initial high pressure requirements, lowers peak acceleration values for the object, and maintains a more constant base pressure. Human-piloted object requirements for modest acceleration (<3g) can be satisfied by building a long acceleration tube of large diameter. The design of the Gas-Gun accelerator assembly protects the magnets of the MDS from overheating of burning gases. There is protection against excessive pressure and also aginst penetration of combustive gases into the gap between the object surface and the launch tube. The proposed Gas-Gun Accelerator project differs from the existing ones in that the heavy object flies inside a lunch tube without touching the tube’s internal walls, i.e. without friction and thus without the burning that is inevitable at such great speeds and great object’s mass. A Gas-Gun assembly with MDS would allow repeated launches of heavy objects into space. It would also considerably reduce the cost of planned cosmic programs since in this case the energy of combustive gases are spent only for acceleration of the object’s mass - something that is a dozen times less than the cost of the first rocket stage carrying fuel. All of the above demonstrates that the choice of the MDS has many advantages vs. EDS when considered for use in the development of the Gas Gun Accelerator for repeated launches of spacecrafts. |
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