Railways – Magnetically suspended car
Reexamination Certificate
1999-07-20
2001-06-26
Morano, S. Joseph (Department: 3617)
Railways
Magnetically suspended car
C104S282000, C104S284000, C104S286000
Reexamination Certificate
active
06250230
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application relates to and incorporates by reference issued U.S. Pat. No. 5,722,326, entitled “Magnetic Levitation System for Moving Objects,” and assigned to The Regents of the University of California (Oakland, Calif.)
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to apparatus and methods for magnetic propulsion, and more particularly to an apparatus and method for reducing inductive coupling between levitation and drive coils within a magnetic propulsion system.
2. Discussion of Background Art
Magnetic levitation and propulsion systems of one sort or other have been in development for some time. As is well known, these systems use electromagnetic principles to generate magnetic fields which support and/or create motion without direct physical contact between a track of some sort and an object being supported and/or propelled.
For instance, in one type of “maglev” train, electrically powered magnet coils are used to produce a levitation force, and complex control circuits are needed to maintain the separation between the poles of these magnets and the under surface of a steel guide-way from which the levitation forces are produced. The control circuitry must be highly reliable, accurate, and responsive, due to the high speeds at which such trains are designed to operate. Other Maglev systems use superconducting coils, the magnetic fields of which interact with coils in a guide-way to produce levitation. These Maglev systems thus typically come with very high manufacturing, operation, and maintenance costs.
An alternative to “maglev” technology is presented in U.S. Pat. No. 5,722,326, entitled “Magnetic Levitation System for Moving Objects,” by Richard F. Post, and assigned to The Regents of the University of California, Oakland, Calif. The '326 patent describes a less costly levitation and propulsion system incorporating a track containing an array of levitation and drive coils interacting with permanent-magnet bars arranged in a “Halbach Array” that are affixed to an object to be levitated and moved.
Application of the '326 patent's technology to high-speed trains as well as new uses such as launching objects into space and various low speed people mover and mining car applications often requires high acceleration rates. Such high acceleration rates are achieved by sending large current pulses through the drive coils. Since the drive coils are interleaved with the levitation coils, current changes in the drive coils will induce parasitic current fluctuations in the levitation coils, through mutual inductive coupling. These parasitic currents can interfere with normal levitation coil currents, resulting in reduced levitation and drive performance.
In response to the concerns discussed above, what is needed is an apparatus and method for magnetic propulsion which overcomes the problems of the prior art.
SUMMARY OF THE INVENTION
The present invention is an apparatus and method for reducing inductive coupling between levitation and drive coils within a magnetic propulsion system. Within the apparatus of the present invention, a pole array creates a spatially periodic magnetic field. Levitation coils are positioned so that, in response to motion of the magnetic field of the pole array, currents are induced in the levitation coils. A first drive coil having a magnetic field coupled to drive the pole array also has a magnetic flux which induces a parasitic current in adjacent levitation coils. A second drive coil having a magnetic field is positioned to attenuate the parasitic current in the adjacent levitation coils by canceling the magnet flux of the first drive coil which induced the parasitic current.
The method of the present invention includes the steps of generating a magnetic field with a pole array for levitating an object; inducing current in a levitation coil in response to motion of the magnetic field of the pole array; generating a magnetic field with a first drive coil for propelling the object; and generating a magnetic field with a second drive coil for minimizing the effects of the changing magnetic field of the first drive coil on the currents in the adjacent levitation coils.
The apparatus and method of the present invention are particularly advantageous over the prior art because an improved drive coil geometry decouples current pulses in drive coils from levitation coils as an object attached to the pole array is propelled. Symmetric drive coils further enhance this decoupling.
These and other aspects of the invention will be recognized by those skilled in the art upon review of the detailed description, drawings, and claims set forth below.
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Morano S. Joseph
Olson Lars A.
Skorich James M.
The Regents of the University of California
Thompson Alan H.
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