Electricity: motive power systems – Linear-movement motors
Reexamination Certificate
2003-04-08
2004-06-22
Mullins, Burton S. (Department: 2834)
Electricity: motive power systems
Linear-movement motors
C104S286000, C104S294000, C310S012060
Reexamination Certificate
active
06753666
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus for operating a magnet vehicle, especially a magnetically levitated vehicle, and including a synchronous long stator linear motor with at least one long stator winding laid along a track and at least one exciter arrangement cooperating with this, extending in the direction of the track and mounted on the vehicle, wherein the long stator winding is divided into winding sections following one another in the direction of the track, separated from one another by changeover points and each having a greater length than the exciter arrangement, at least two section cables associated with the winding sections for supplying the winding sections with electric power and switch devices for sequential connection of the winding sections each to a section cable in correspondence with the progression of the vehicle.
DESCRIPTION OF THE PRIOR ART
Long stator linear motors of the kind here of interest (e.g. U.S. Pat. No. 5,053,654, DE 199 22 441 A1) comprise as the primary part a long stator laid along a given track, with at least one long stator winding (e.g. U.S. Pat. No. 4,665,329, U.S. Pat. No. 4,728,382), in which a travelling electromagnetic field propagating in the direction of movement of the vehicle to be driven is generated. On the other hand an exciter arrangement mounted on the vehicle and mostly extending over its whole length (e.g. DE 34 10 119 A1) serves as the secondary part and is composed of electromagnets serving simultaneously as supporting magnets. The long stator winding is usually divided into a plurality of winding sections, which lie directly after one another in the direction of travel, separated electrically from one another by changeover points and with lengths of 1000 m to 2000 m for example, which are indeed comparatively short but substantially longer than the vehicle of up to 250 m length for example. At least one comparatively long, e.g. about 40 km long section cable is also laid parallel to the track, being connected at one or both ends to a so-called substation, in which the inverters or the like needed to supply the current and voltage of the stator winding are installed. In order to restrict the power consumption and the effective impedance only that winding section in which the vehicle is actually located is supplied with current, in that the individual winding sections are connected individually and one after the other to the track section cable with the aid of switching devices, in accordance with the progress of the vehicle. The switching over operations needed for this are effected according to known methods, which have become known under designations such as, short-circuit, leap-frog, alternate step, three-step methods for example or the like (for example electrotechnical journal etz, vol. 108, 1987, issue 9, pages 378 to 381). As well as this it is also E own to overlap the individual winding sections over part of their length and always to undertake the switching over from one to the other winding section when the vehicle is located in an overlapped region (U.S. Pat. No. 4,454,457).
In operation of such a magnetically levitated vehicle the substations have to supply voltages which are substantially equal to the sum of the voltage induced by the vehicle (synchronous emf or internal voltage), the voltage drop across the corresponding winding section and the voltage drop across the associated part of the section cable. If the voltage drop across the section cable is neglected, there is available to drive the vehicle that current which can be obtained with the part of the voltage supplied by the substation which exceeds the synchronous emf.
The synchronous emf is, especially at high speeds, substantially proportional both to the speed of the vehicle and to the length of the exciter arrangement (vehicle length). Accordingly the voltages supplied by the substations in those track parts in which high speeds are to be achieved must be especially large. This applies all the more as the substations of these track section parts are provided with high step-up transformers at their outputs so that they do supply high voltages but only provide small currents and thus small thrust forces or powers.
As against the comparatively small construction costs along the track there is the problem with these apparatuses that arbitrary increase of the output voltages of the substations is not possible with the currently available long stator windings or their insulations. A consequence of this that the attainable voltage limits lie around 10 kV to 20 kV for example. In conjunction with the normally provided maximum currents of about 1000 A and with vehicles whose exciter arrangements comprise 10 sections with lengths of 25 m each for example, the attainable speeds amount to about 400 km/h at the most. Higher maximum speeds can only be attained with shorter trains while longer trains can only be realised with smaller maximum speeds.
Synchronous long stator linear motors are also known (DE 28 06 601 A1) in which the individual winding sections of the long stator winding have lengths which correspond to a fraction of the length of the exciter arrangements. The winding sections are fed by inverters which are associated with them in fixed position, each with an associated switching device and connected by a common section cable to a DC source. Against the advantage of a more favourable voltage distribution to a plurality of winding sections there is here the disadvantage that a higher outlay in apparatus along the track is necessary on account of the plurality of inverters and switching devices per vehicle length.
SUMMARY OF THE INVENTION
Starting from the above the invention is based on the object of solving the voltage and power problem discussed above.
A further object of this invention is to design the apparatus mentioned above such that higher vehicle speeds can be obtained with the same lengths of the exiciter arrangements and/or longer exciter arrangements and thus longer vehicles with the same vehicle speed.
Yet another object of this invention is to design the apparatus mentioned above such that higher vehicle speeds and/or longer exciter arrangements can be attained even if conventional long stator windings are used and the maximum voltages appearing at the outputs of the substations are not increased.
A further aim of this invention is to achieve the objects mentioned above without increasing the maximum voltages appearing at the outputs of the substations and without a drastic increase in the construction cost.
These and other objects were solved and these and other aims are attained by the present invention by means of an apparatus of the kind specified above which is characterized in that the winding sections each comprise at least a first and a second winding section part, wherein the first winding section part consists of first winding segments connected electrically conductively to each other and wherein the first and second segments have a smaller lengths than the exciter arrangement and are so arranged one after the other in the direction of the track in a predetermined sequence that the winding sections in any arbitrarily conceived sector extending along the track and having a length corresponding to the exciter arrangement always contain in each case at least one first and one second winding segment.
The result of the subdivision of the long stator winding according to the invention is that the voltage induced by the exciter arrangement at any point of the track is distributed over two or more winding section parts, each connectable to a separate substation.
The result of this is that, without increasing the maximum voltage to be applied to a winding section part, there are voltage or power reserves which allow higher speeds and/or greater vehicle lengths. Nevertheless each winding section and each winding section part can have a substantially greater length than the exciter arrangement, so that the number of inverters or the like to be installed along the length of the track remains comparatively
Jones Judson H.
Mullins Burton S.
Robert & Bosch GmbH
Striker Michael J.
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