US3820471A

US3820471A - Magnetic levitating and propelling device including split stabilizingcoil for high speed train

Info

Publication number: US3820471A
Application number: US00367367A
Authority: US
Inventors: N Maki; H Okuda
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1973-06-06
Filing date: 1973-06-06
Publication date: 1974-06-28
Anticipated expiration: 1991-06-28

Abstract

A device for magnetically levitating and propelling a car at a high speed utilizing magnetic repulsion in which a stabilizing coil disposed on the ground opposite to a pair of superconducting coils is split into a pair of stabilizing coil sections which are supported in close proximity to the respective superconducting coils so as to reduce the electromagnetic force acting between the superconducting coils and to reduce the magnetomotive force required for these superconducting coils.

Description

United States Patent [191 Maki et al.

1 1 MAGNETIC LEVITA'I'ING AND PROPELLING DEVICE INCLUDING SPLIT STABILIZING COIL FOR HIGH SPEED TRAIN [75] Inventors: Naoki Maki, Ibaraki-ken; Hironori Okuda, Hitachi, both of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: June 6, 1973 [2i] App]. No.: 367,367

[30] Foreign Application Priority Data June 15, 1972 Japan 47-59690 [52] U.S. Cl. 104/148 SS [51] Int. Cl B6lb 13/08 [58] Field of Search 104/148 SS; 310/166; 308/10 [56] References Cited UNITED STATES PATENTS 3,470,828 10/1969 Powell, Jr. et al 104/148 SS OTHER PUBLICATIONS Powell et al. The Application of Superconductors to [451 June 28, 1974 High Speed Transport, Cryogenics and lndustrial Gases, Oct. 1969, pp. 19-24.

Powell et al., The Linear Synchronous Motor and High Speed Ground Transport, 1971 Intersociety Energy Conversion Engineering Conference.

Primary Examiner-M. Henson Wood, Jr. Assistant ExaminerGeorge H. Libman Attorney, Agent, or FirmCraig and Antonelli [5 7] ABSTRACT A device for magnetically levitating and propelling a car at a high speed utilizing magnetic repulsion in which a stabilizing coil disposed on the ground opposite to a pair of superconducting coils is split into a pair of stabilizing coil sections which are supported in close proximity to the respective superconducting coils so as to reduce the electromagnetic force acting between the superconducting coils and to reduce the magnetomotive force required for these superconducting coils.

4 Claims, 6 Drawing Figures mmmmmw 3820.471

sum 10F 3 FIG. I

PRIOR ART PATENTEDJUHZB 1974 3820 471 sum 2 OF 3 MAGNETIC LEVITATING AND PROPELLING DEVICE INCLUDING SPLIT STABILIZING COIL FOR HIGH SPEED TRAIN This invention relates to improvements in a device for magnetically levitating and propelling a train, especially a superhigh-speed train utilizing magnetic repulsion.

Realization of the idea of a superhigh-speed train running at a superhigh-speed of 400 to 600 kilometers per hour has been considered impossible due to the increase in the running resistance with known propulsion guide means including rails and rail-engaging wheels and due to the reduction in the adhesion between the rails and the rail-engaging wheels.

In an effort to realize such an idea, a system has been proposed which comprises means for magnetically levitating the car from the ground and a linear motor such as a linear induction motor or a linear synchronous motor for propelling the car.

FIG. 1 shows one of prior art arrangements in which superconducting coils are disposed on the side of the car and induction repulsion means such as short-circuit coils or sheets of a good conductor are disposed on the ground opposite to the superconducting coils. More precisely, referring to FIG. 1, a pair of

superconducting coils

2 and 2 are disposed horizontally at spaced positions in the lower part of the car body 1 for levitating the car body 1 and a pair of superconducting coils 4 and 4' are disposed vertically with respect to the ground surface at spaced positions opposite to the side walls of a cavity or recess 3 formed in the lower central part of the car body 1 for stably propelling the car body 1. These

superconducting coils

2,2 and 4,4 are housed within

heat insulating vessels

2a, 2a and 4a, 4a filled with liquid helium respectively so that they can be maintained in the superconducting state. Two to six sets of these

superconducting coils

2, 2, 4 and 4 are customarily disposed in each car along the direction of propulsion of the car.

Elements disposed on the ground include a pair of induction repulsion means or short-circuit levitating coils 5 and 5' disposed horizontally opposite to the respective

superconducting coils

2 and 2, a short-circuit stabilizing coil 6 disposed vertically within the recess 3 opposite to the

superconducting coils

4 and 4, and a propelling coil 7 energized by an a.c. power supply for producing a shifting magnetic flux which is in interlinking relation with the

superconducting coils

4 and 4 and is in synchronism with the speed thereby propelling the car. These coils 5, 5', 6 and 7 are fixed to the ground by anchoring means such as a block of concrete 8 while maintaining the predetermined relation between their positions. The induction repulsion means may be sheets of good conductor such as sheets of copper or aluminum in lieu of the levitating coils 5 and 5' above described.

The operation-of the coils for providing the propulsive force, levitating force and stabilizing force will be described. The propulsive force is obtained by the interaction between the flux component of the magnetic flux produced by the

superconducting coils

4 and 4 and interlinked perpendicularly with the propelling coil 7 and the current supplied to the propelling coil 7 from the external power supply. The levitating force is obtained by the magnetic repulsion due to the interaction between the said perpendicular flux component of the magnetic flux produced by the superconducting coils 4 and 4' and the current induced in the successive levitating coils 5 and 5' in the advancing direction of the car due to the voltage induced in the levitating coils 5 and 5' interlinked with the magnetic flux produced by the

superconducting coils

2 and 2.

The stabilizing force will be described with reference to FIG. 2 which shows the distribution of the density of the magnetic flux produced by the

superconducting coils

4 and 4 for interlinkage with the stabilizing coil 6. The density B, of the magnetic flux portion produced by the superconducting coils 4 (AB) and 4 (CD) in the horizontal direction, hence in the direction perpendicular to the advancing direction of the car, is distributed as shown on the right-hand side of FIG. 2. When the car is displaced by x in the transverse direction thereof, a magnetic flux (1), interlinks with the stabilizing coil 6 (PO) thereby inducing a voltage in the stabilizing coil 6(PQ) and inducing a current la in this coil. The density B of the magnetic flux portion produced by the superconducting coils 4 and 4' in the vertical direction of the stabilizing coil 6 (PO) is distributed as shown on the lower side of FIG. 2. This magnetic flux portion having the density B, interacts with the current I, induced in the stabilizing coil 6 (F0) for producing a stabilizing force to prevent lateral displacement of the car so that the car can always be maintained in the neutral position without being displaced in both the transverse and vertical directions. When the displacement x 0, 0x O and l 0. Thus, the stabilizing force, that is, the force tending to restore the car to the position of zero displacement is zero.

In the prior art car levitating and propelling system shown in FIG. 1, the supporting structure for the stabilizing coil 6 must have a sufficient mechanical strength in order to support the stabilizing coil 6 against the electromagnetic force imported thereto. An increase in the thickness T of the supporting structure of, for example, concrete to satisfy the above requirement results in a greater distance between the stabilizing coil 6 and the superconducting coils 4 and 4'. Further, the distance between the superconducting coils 4 and 4' cannot be increased as they should be disposed as close to the stabilizing coil 6 as possible, and thus, a considerable electromagnetic force acts between the

superconducting coils

4 and 4. This is ojectionable in that the car must have an excessively high mechanical strength in order to withstand such a force.

The electromagnetic force F acting between the superconducting coils 4 and 4' is given by F 2 13/2m1 (N/m) where d is the distance in meters between the superconducting coils 4 and 4', I, is the magnetomotive force in ampere-tums of the

superconducting coils

4 and 4, and n is the permeability in air, 41r X 10 Elm. Suppose that a stabilizing force of 1.5 tons/m is required when the car is laterally displaced by 2 cm in'the horizontal direction, I, 6 X 10 AT, and d 0.6 m. Then, the electro magnetic force F acting between the

superconducting coils

4 and 4 is F (4 X 10" X (6 X l0 )/0.6) (l/9.8 X 10) =25 tons/m (2) This electromagnetic force F is about seventeen times the stabilizing force of 1.5 tons/m essentially required. This leads to the disadvantage that the superconducting coils, heat insulating vessels and car body 1 must be constructed stronger than are required in order that they can withstand such electromagnetic force.

It is therefore an object of the present invention to reduce the electromagnetic force acting between the superconducting coils on opposite sides of the stabilizing coil without reducing the required stabilizing force.

Another object of the present invention is to simplify the structure of the superconducting coils and heat insulating vessels and to reduce the mechanical strength required for the car body thereby reducing the weight thereof.

In accordance with the present invention which attains the above objects, the stabilizing coil 6 shown in FIG. 1 is split into two sections corresponding respectively to the superconducting coils 4 and 4' and these two stabilizing coil sections are short-circuited to each other so that the magnetomotive forces produced thereby cancel each other.

The split of the stabilizing coil into such coil sections is advantageous in that the stabilizing coil sections can be spaced apart by a large distance from each other and a supporting material of, for example, concrete can be filled in a large quantity in the space between these coil sections thereby providing a sufficiently strong supporting structure. Further, the distance d between the

superconducting coils

4 and 4 in Equation (1) can be increased due'to the fact that the stabilizing coil 6 is split into the two coil sections which are sufficiently spaced apart from each other. Therefore, the electromagnetic force F acting between these superconducting coils can be reduced as will be readily apparent from Equation (1). Furthermore, due to the fact that the stabilizing coil sections can be substantially supported by the supporting material portion filling the space therebetween, the supporting material portions lying on the sides opposite to the superconducting coils may be eliminated or the thickness thereof may be quite small. Therefore, the distance between the stabilizing coil sections and the corresponding superconducting coils can be reduced to an allowable limit which will not obstruct free running of the car so that the magneto-motive force I, in Equation (1), hence the electromagnetic force F can be reduced.

According to the present invention, the'stabilizing coil 6 is split into the two coil sections which are spaced apart by a large distance from other as above de-- scribed, and thus, the distance d between the superconducting coils 4 and 4' can be remarkably increased. This arrangement is advantageous in that the induction repulsion means such as the levitating coils may be easily disposed at a position interlinked by the magnetic flux loop of the superconducting coils 4 and 4' disposed opposite to the stabilizing coil sections so that the other pair of superconducting coils disposed opposite to these levitating coils may be eliminated and the number of the superconducting coils required in the car may be reduced by half.

The above and other objects, features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic sectional view showing the arrangement of coils in a prior art device for magnetically levitating and propelling a car;

FIG. 2 is a diagrammatic view showing the density distribution of magnetic flux produced by the superconducting coils interlinking with the stabilizing coil in the device shown in FIG. 1;

FIG. 3 is a schematic sectional view showing the arrangement of coils in an embodiment of the device for magnetically levitating and propelling a car according to the present invention; and.

FIG. 4, 5 and 6 are schematic sectional views showing the arrangement of coils in other embodiments of the present invention.

The present invention will now be described in detail with reference to FIGS. 3 to 6 in which like reference numerals are used to denote like parts appearing in FIG. 1.

Referring first to FIG. 3 showing an embodiment of the present invention, a pair of spaced

superconducting coils

4 and 4 are disposed vertically in the body 1 of a car, and a pair of spaced stabilizing

coil sections

6a and 6b are disposed on the ground opposite to the respective

superconducting coils

4 and 4. These stabilizing

coil sections

6a and 6b are connected to each other by

leads

9a and 9b to form a closed circuit so that the magnetomotive forces thereof cancel each other. The stabilizing

coil sections

6a and 6b are embedded in a supporting structure 10 of, for example, concrete together with a pair of levitating coils 5 and 5' and a propelling coil 7. A pair of

superconducting coils

2 and 2 are disposed in the car body 1 opposite to the respective

levitating coils

5 and 5. The stabilizing

coil sections

6a and 6b are secured in position by being substantially supported by the supporting material filling the space 10a therebetween. Alternatively, a supporting material portions having the thicknesses Ta and Tb may be eliminated so that the stabilizing

coil sections

6a and 6b can be supported directly on the side surfaces ofthe supporting structure 10.

According to such arrangement, the magnetic fluxes d) and :12 produced by the

superconducting coils

2, 2, 4 and 4' in the car are'distributed as shown by the onedot chain lines in FIG. 3 so that the desired car levitating, propelling and stabilizing functions can be satisfactorily obtained.

The force required for stabilizing the car in FIG. 3 will now be compared with that in FIG. 1. Suppose that a stabilizing force of 1.5 tons/m is required when the car is laterally displaced by 2 cm in the horizontal direction, magnetomotive force I, of the

superconducting coils

4 and 4 is 6 X 10 AT, and distance d between the

superconducting coils

4 and 4 is 1.8 m which is three times that in FIG. 1. Then, the electromagnetic force F acting between the

superconducting coils

4 and 4 is sought from Equation (1) as follows:

F=(4 x10 x (6 x l0 /1.8 )x( l/9.8 x 10 z 8.3 (tons/m) It will be seen from Equation (3) that the value of the electromagnetic force F in this case is about 33 percent of that given by Equation (2).

Further, due to the fact that the stabilizing

coil sections

6a and 6b can be mechanically supported by the supporting material filling the space 10a between these coil sections, the stabilizing

coil sections

6a and 6b can be disposed at any desired positions in proximity to the

superconducting coils

4 and 4 within the range in which they do not obstruct free running of the car, and thus, the magnetomotive force I, required for the superconducting coils can be reduced. A 30 percent reduction of the magnetomotive force I, in Equation (3) gives an electromagnetic force F of 4.1 tons/m and this value is about 16 percent of 25 tons/m given by Equation (2). Thus, the electromagnetic force F can be remarkably reduced, and a great reduction can be attained in the mechanical strength required for the superconducting coils, heat insulating vessels and car body.

FIG. 4 shows another embodiment of the present invention in which superconducting coils 4 and 4 for stabilized propulsion of the car serve also as means for levitating the car. In this embodiment, levitating coils 5 and 5' on the ground side are inclined with respect to the horizontal as shown so as to increase the eflective component of the magnetic flux produced by the superconducting coils for interlinkage with the levitating coils 5 and 5.

The above description has referred to the case in which a pair of superconducting coils produced magnetic fluxes which run perpendicularly to the advancing direction of the car and substantially horizontally in directions opposite to each other.

However, the present invention is in no way limited to such specific arrangement and the magnetic fluxes produced by these superconducting coils may run perpendicularly to the advancing direction of the car and substantially horizontally in the same direction. In this latter case, the manner of connection of the

leads

9a and 9b for the

superconducting coil sections

6a and 6b is opposite to that illustrated.

In a further embodiment of the present invention, a single levitating coil 5 is disposed beneath a pair of stabilizing

coil sections

6a and 6b supported by a supporting structure in a lower central recess 3 of the car body 1, and a propelling coil 7 is disposed above the stabilizing

coil sections

6a and 6b in the supporting structure 10.

Referring to FIG. 6 showing a modification of the embodiment shown in FIG. 5, the levitating coil 5 in FIG. 5 is connected to another a.c. power supply so that it serves as a levitating and propelling coil 11. According to this arrangement, the coil means disposed on the ground side can be further simplified.

It will be understood from the foregoing detailed description of the present invention that the electromagnetic force acting between the superconducting coils disposed vertically opposite to each other in the car can be remarkably reduced and the magnetomotive force required for these superconducting coils can also be greatly reduced. Thus, a desired reduction can be attained in the mechanical strength and weight of the car and an economical superhigh-speed train can be realized. Further, the mechanical support for the stabilizing coils disposed on the ground side can be easily attained. Furthermore, due to the fact that the superconducting coils can be spaced apart from each other by a greater distance than hitherto, these superconducting coils can also serve as levitating means and the number of levitating coils can be reduced to one-half of the number conventionally employed.

What we claim is:

l. A device for magnetically levitating and propelling a superhigh-speed train comprising at least one pair of d.c.-energized superconducting coils disposed in the lower part of the car for producing magnetic fluxes which run perpendicularly to the advancing direction of the car and substantially horizontally, in directions opposite to each other or in the same direction, a plurality of pairs of stabilizing coils disposed on the ground side along the advancing direction of the car, said stabilizing coils in each pair being disposed opposite to said superconducting coils respectively and short-circuited to each other so as to cancel the magnetomotive forces produced thereby, a plurality of induction repulsion levitating means in the form of short-circuit coils or conductive sheets disposed on the ground along the advancing direction of the car so as to be interlinked by the magnetic flux produced by said superconducting coils, and a plurality of a.c. energized propelling coils disposed on the ground side along the advancing direction of the car so as to produce a magnetic flux interlinking with said superconducting coils.

2. A device for magnetically levitating and propelling a superhigh-speed train as claimed in claim 1, wherein at least one pair of d.c.-energized superconducting coils are disposed in directions opposite to each other or in the same direction in the lower part of the car for producing magnetic fluxes running substantially horizontally so that said induction repulsion levitating means can be interlinked by the magnetic fluxes produced by said superconducting coils.

3. A device for magnetically levitating and propelling a superhigh-speed train as claimed in claim 1, wherein the magnetic fluxes in the closed magnetic loops consisting of said superconducting coils and said stabilizing coils interlink with the flux of said propelling coils disposed on the ground side.

4. A device for magnetically levitating and propelling a superhigh-speed train as claimed in claim 1, wherein said induction repulsion levitating means are inclined with respect to the ground surface.

Claims

1. A device for magnetically levitating and propelling a superhigh-speed train comprising at least one pair of d.c.energized superconducting coils disposed in the lower part of the car for producing magnetic fluxes which run perpendicularly to the advancing direction of the car and substantially horizontally, in directions opposite to each other or in the same direction, a plurality of pairs of stabilizing coils disposed on the ground side along the advancing direction of the car, said stabilizing coils in each pair being disposed opposite to said superconducting coils respectively and short-circuited to each other so as to cancel the magnetomotive forces produced thereby, a plurality of induction repulsion levitating means in the form of short-circuit coils or conductive sheets disposed on the ground along the advancing direction of the car so as to be interlinked by the magnetic flux produced by said superconducting coils, and a plurality of a.c. - enErgized propelling coils disposed on the ground side along the advancing direction of the car so as to produce a magnetic flux interlinking with said superconducting coils.