Power supply system and method for linear stator motor

In a power supply system for a linear stator motor, the installed operating means should be utilized in an optimum manner, while the losses due to energy transfer should be maintained as low as possible. For this purpose, the cable route systems should be connected with each other by at least one controllable coupling switch, in such a way that the switching segment in which the vehicle is located at any particular time is always connected with all the cable route systems.

BACKGROUND OF THE INVENTION 
The present invention relates generally to power supply systems and 
methods, and more particularly to a power supply system and method for a 
linear stator motor. 
DE-B 23 10 812 discloses a power supply system for magnetic suspension 
vehicles, in which the stator winding of the linear stator motor is 
divided into several switching segments along the travel path. The 
switching segments are alternately assigned to a first and a second cable 
route system. The switching segments and the cable route systems can be 
switched via switching devices (e.g. contactors) to controllable power 
supply devices, which are usually arranged in transformer substations. In 
the switching segments, a revolving field voltage U.sub.p is then induced 
by the vehicle in each case which supplies a thrust F.about.U.sub.p 
.times.I, where I is the input current. 
This power supply system operates according to the leap frog control 
method. Here, a differentiation is made between a short route (or 
secondary) with only one transformer substation, and a long route with 
more than one substation along the travel path. 
In the case of secondary or short routes with two cable route systems, two 
power supply devices (e.g. converters) are arranged in a single 
substation. Each converter is arranged in a cable route system. The 
switching segments are alternately rigidly assigned to one of the two 
cable route systems, and can be switched on or off via contactors. In each 
case, the switching segment in which the vehicle is located is switched on 
and supplied from one of the two converters. When changing switching 
segments, the converter which was previously inactive becomes active, and 
supplies the following switching segment. 
In the case of long routes with two cable route systems, at least two 
converters are housed in each of the substations. The switching segment in 
which the vehicle is located is simultaneously supplied from two 
converters from adjacent substations. When changing switching segments, 
the other two (previously shut off) converters of the same substations are 
activated and supply the following switching segment. 
In the previous power supply systems, one of the two converters is 
therefore not utilized, both for short and for long routes--aside from 
changes in switching segments. Furthermore, each of the cable route 
systems are only utilized for approximately 50% of the total operating 
time. 
SUMMARY OF THE INVENTION 
The present invention is directed to the problem of developing a power 
supply system and method for linear stator motors, which utilizes the 
installed operating means, especially the power supply devices (e.g. 
converters) and cable route systems, in an optimum manner, while 
simultaneously maintaining the losses due to the energy transfer from the 
power supply devices to the switching segments as low as possible. 
The present invention solves this problem by coupling the cable route 
systems together in such a manner so that a switching segment in which the 
magnetic suspension vehicle is located at a specific time is always 
connected with the first and second cable route systems, and when changing 
from the first switching segment to the second switching segment both 
switching segments are each coupled to only one cable route system. 
An advantageous embodiment of the present invention utilizes a vehicle 
detection device, which detects the location of the magnetic suspension 
vehicle. This allows proper control of the switching segments and enables 
control of the controllable coupling switch. 
Another advantageous embodiment occurs when each cable route system has 
precisely one power supply device coupled to it. In this embodiment, the 
power supply device comprises a current converter and a feed switch 
arranged within a substation. 
Another advantageous embodiment occurs when each cable route system 
utilizes several power supply devices. In this embodiment, the power 
supply devices comprise a converter and a feed switch, and these power 
supply devices are distributed among several substations. In addition, 
each switching segment is simultaneously supplied from at least two 
converters from adjacent substations. 
An additional advantageous embodiment occurs when the segment switches are 
located in switching points, and when the coupling switches are coupled to 
the ends of the cable route systems. This embodiment is especially well 
suited for short or secondary routes because it is particularly easy to 
implement. 
For long routes with several substations, power supply systems in which the 
coupling switches are coupled to the cable route systems in the 
substations, or between the substations, or at the switching points are 
particularly advantageous, since the existing cable systems are fully 
utilized, and redundancy is also available in case of problems. 
In a power supply system in which the coupling switches are located within 
substations, the converters can be optionally switched to both cable route 
systems directly from the substation. Thus minimizing the power paths from 
the substation to the switching segment. 
A power supply system according to the present invention results in a 
reduction in cable stress for the cable route systems. The converters 
first feed into different cable systems, so that in the case of two cable 
route systems, the current load is reduced by approximately 50% up to the 
point where the closed coupling switch brings the currents of the two 
cable route systems together. 
In a power supply system in which the coupling switches are located at each 
switching point, the current paths are minimal, and the cable stress is 
simultaneously reduced in half. 
The power supply system according to the present invention is suitable both 
for short or secondary routes with only one transformer substation and for 
long routes with more than one substation along the route. By connecting 
the cable route systems by means of coupling switches, the existing power 
supply devices (e.g. converters) are utilized in an optimum manner, since 
they can simultaneously supply power. With two cable route systems, both 
converters can simultaneously supply the switching segment in which the 
magnetic suspension vehicle is located at a particular time. The first 
converter accomplishes this directly via the first cable route system, 
while the second converter accomplishes this via the second cable route 
system, the coupling switch and the first cable route system. 
As compared with the previous power supply systems operated according to 
the leap frog method, the present invention, in the case of two cable 
route systems, for example, now makes available either twice as much 
current and therefore twice the thrust, or enables the converters to be 
half the size. For long routes, rather than reducing the size of the 
converters half of the converters can be eliminated. 
The method of the present invention operates in such a way to allow current 
from all power supply devices to flow to the switching segment in which 
the magnetic suspension vehicle is located. When the vehicle is changing 
from one segment to another, the current from one power supply device 
flows into only one switching segment and the current from another power 
supply device flows into the other switching segment. Finally, when the 
magnetic suspension vehicle moves completely within the other switching 
segment, the current from all power supply devices flows into the other 
switching segment, and none flows into the switching segment in which the 
vehicle was previously.

DETAILED INVENTION 
In FIGS. 1-19, the stator winding of a linear motor is divided into several 
switching segments 1-4 along the travel path for a magnetic suspension 
vehicle. In the examples shown, the switching segments 1-4 are equally 
long, but they can also have different lengths. The switching segments 1-4 
can be alternately connected to a first and a second cable route system 9 
or 10, respectively, via segment switches 5-8. Two of the segment switches 
5-8 are arranged in each of a switching point 24 or 25. In the examples 
shown in the figures, the switching segments 1 and 3 are assigned to the 
cable route system 9, and the switching segments 2 and 4 are assigned to 
the cable route system 10. For short routes (FIGS. 1 and 9-11), a single 
converter 11 or 12, respectively, is assigned to the first cable route 
system 9 and the second cable route system 10, respectively. The cable 
route system 9 can be connected with the converter 11 via a feed switch 
13, and the second cable route system 10 can be connected to the converter 
12 via a feed switch 14. The converters 11 and 12 with their related feed 
switches 13 and 14 are housed in a common substation 17. 
For long routes (FIGS. 5 and 15-18), several converters 11a, 11b, or 12a, 
12b, are assigned to each cable route system 9 or 10, respectively. In 
this case, the cable route system 9 can be connected with the converters 
11a and 11b via feed switches 13 and 15. The cable route system 10 can be 
connected with the converters 12a and 12b via a feed switch 14 or 16, 
respectively. The converters 11a and 12a are housed together in a 
substation 17, and the converters 11b and 12b are housed in a substation 
18, which is adjacent to the substation 17. The prior art power supply 
system is operated according to the leap frog control method. In this 
method, the switching segment in which the vehicle is located at a 
particular time is always switched on and supplied from one of the two 
converters 11 or 12. The position of the magnetic suspension vehicle is 
designated with x. The arrow 19 designates the direction of travel. In the 
case shown in FIG. 1, the vehicle is located in switching segment 1 and is 
moving towards switching segment 2. As long as the vehicle is located in 
switching segment 1, the segment switch 5 and the feed switch 13 are 
closed and the segment switches 6-8 and the feed switch 14 are open. 
Therefore the switching segment 1 is only supplied by the converter 11, 
and a revolving field voltage U.sub.p1 is induced in the latter, which 
provides a thrust F.sub.1 .about.U.sub.p1 .times.I.sub.1. For a better 
overview, the revolving field voltages and the currents as well as the 
thrusts are drawn in different sizes in the individual switching segments. 
Furthermore, the values indexed with 1 are drawn with dot-dash lines in 
all the diagrams, and the values indexed with 2 are shown with broken 
lines. 
When changing switching segments (e.g. from switching segment 1 to 
switching segment 2) at the time t.sub.A, the segment switch 6 and the 
feed switch 14 are closed, in addition, so that the switching segment 1 is 
supplied from the converter 11 and the switching segment 2 is supplied 
from the converter 12 (see FIGS.2-4). At the times t.sub.w indicated in 
FIGS. 2-4, the vehicle is precisely half in switching segment 1 and half 
in switching segment 2. After the change in switching segments (time 
points t.sub.E), the switches 5 and 13, which were previously closed, are 
opened. The converter 11 is therefore shut off. In the known control 
method, one of the two converters 11, 12 is not utilized--except during 
changes from one switching segment to another. 
For the power supply system of a long route (FIG. 5), it also holds true 
that only the switching segment in which the vehicle is located at a 
particular time is supplied from its related converters. In FIG. 5, this 
again is the switching segment 1, which is connected with the converters 
11a and 11b. The segment switch 5 and the feed switches 13 and 15 are 
closed for this purpose, the segment switch 8 and the feed switches 14 and 
16 are open. Therefore the switching segment 1 is only supplied with a 
current I.sub.1. The current I.sub.1 which flows via the segment switch 5 
is the total of the currents I.sub.1a and I.sub.1b fed into the cable 
route system 9 by the converters 11a and 11b. 
When changing from switching segment 1 to switching segment 2, at the time 
t.sub.A, the segment switch 6 and the feed switches 14 and 16 are closed, 
in addition, so that the switching segment 1 is supplied from the 
converters 11a and 11b and the switching segment 2 is supplied from the 
converters 12a and 12b. After the change in switching segments (time point 
t.sub.E), the switches 5, 13 and 15, which were previously closed, are 
opened. The converters 11a and 11b are then shut off. Even for long 
routes, half of the converters are therefore not utilized, with the 
exception of changes from one switching segment to another (see diagrams 
in FIGS. 6-8). t.sub.w again indicates the time at which the vehicle is 
located half in each of the switching segments 1 and 2. 
In the power supply system according to the present invention (FIGS. 9-11 
and 15), coupling switches 20, 21 are provided, with which the cable route 
systems 9, 10 can be connected with each other in such a way that the 
switching segment in which the vehicle is located at a particular time is 
always connected with all the converters 11, 12, or 11a, 11b and 12a, 12b. 
For short routes (FIGS. 9-11), the switching points 22, 23 present at the 
ends of the cable route system 9, 10 are obvious locations for the 
installation of coupling switches. As long as the vehicle is in the 
switching segment 1 (FIG. 9; time t.sub.1 in FIGS. 12-14), one of the two 
coupling switches 20, 21 (e.g. coupling switch 21) is closed. Furthermore, 
the segment switch 5 and the feed switches 13 and 14 are closed, and the 
segment switches 6-8 are open. Therefore the switching segment 1 is 
connected both with the converter 11 and with the converter 12 (converter 
11 directly via the first cable route system 9; converter 12 via the 
second cable route system 10, the coupling switch 21, the first cable 
route system 9 and the closed segment switch 5). The current I flowing in 
the switching segment 1 is therefore the total of the currents I.sub.1 and 
I.sub.2 supplied by the converters 11 and 12. 
When changing from switching segment 1 to switching segment 2 (FIG. 10; 
time t.sub.3 in FIGS. 12-14), the cable route systems 9 and 10 are 
separated from each other by opening of the coupling switch 21. At the 
same time, the segment switch 6 is closed, so that the switching segment 1 
is supplied from the converter 11 (current I.sub.1) and the switching 
segment 2 is supplied from the converter 12 (current I.sub.2). t.sub.w 
again indicates the time at which the vehicle is located half in each of 
the switching segments 1 and 2. 
After the change in switching segments, the vehicle is located in switching 
segment 2 (FIG. 11; time t.sub.4 in FIGS. 12-14). The segment switch 5, 
which was previously closed, is opened, and the coupling switches 21 is 
closed again. Therefore, a current I only flows in switching segment 2, 
which current again is the total of the currents I.sub.1 and I.sub.2 
supplied by the converters 11 and 12. 
From the schematics (FIGS. 9-11), in combination with the diagrams (FIGS. 
12-14), the method of functioning of the power supply system at a change 
in switching segments is evident. 
The vehicle is first located in the switching segment 1 and the converter 
11 supplies this switching segment with current I.sub.1. At the same time 
that the coupling switch 21 is opened, the converter 12 regulates the 
current I.sub.2 to zero. Then the switching segment 2 is connected. The 
converter 12 regulates the current I.sub.2 up again, and now supplies the 
switching segment 2 via the cable route system 9. While this is happening, 
half of the vehicle has moved into the switching segment 2 (FIG. 10). Now 
the converter 11 regulates the current I.sub.1 to zero, the switching 
segment 1 is shut off and the coupling switch 21 is closed again. Then the 
converter 11 regulates the current I.sub.1 up again and supplies the 
switching segment 2 via the cable route system 9, the coupling switch 21 
and the cable route system 10 (FIG. 11). 
In the power supply system according to the present invention for a long 
route (FIGS. 15-18), the coupling switches 20, 21 can be arranged in the 
switching points 24, 25 of the segment switches 5 and 6 or 7 and 8, 
respectively; in FIG. 15, a single coupling switch 21 is arranged in the 
switching point 25, in FIG. 18, the coupling switch 20 is arranged in the 
switching point 24 and the coupling switch 21 is arranged in the switching 
point 25. 
Control of the individual switching segments as well as regulation of the 
currents takes place analogous to the regulation and control for short 
routes. 
In FIG. 15, the vehicle is located in switching segment 1. The coupling 
switch 21 as well as the feed switches 13 to 16 and the segment switch 5 
are closed. The segment switches 6-8 are opened. Therefore the switching 
segment 1 is connected both with the converters 11a, 11b and with the 
converters 12a, 12b (converters 11a, 11b directly via the first cable 
route system 9; converters 12a, 12b via the second cable route system 10, 
the coupling switch 21 and the first cable route system 9, as well as the 
closed segment switch 5). The current I flowing in the switching segment 1 
is therefore the total of the currents I.sub.1 and I.sub.2 supplied by the 
converters 11a, 11b as well as 12a, 12b. The currents I.sub.1 and I.sub.2, 
in turn, are the total of the currents I.sub.1a and I.sub.1b, and I.sub.2a 
and I.sub.2b, respectively. 
In addition to the arrangement of the coupling switches 20, 21 in the 
switching points 24, 25 (FIGS. 15 and 18), the coupling switches 20, 21 
can also be arranged in the substations 17 and/or 18 (FIG. 16) as well as 
between the substations 17, 18 (FIG. 17), as an alternative. In the 
examples in FIGS. 16 and 17, the vehicle again is located in the switching 
segments1, so that with regard to the current flow as well as the change 
in switching segments, reference is made to the above explanations. 
As shown in FIG. 19, the current can be transported to the switching 
segment 4 via an alternative path (first cable route system 9) in case of 
problems in the route switching of the power supply system according to 
the present invention, e.g. an interruption 26 in the cable route system 
10. Therefore redundancy is achieved in an advantageous manner for when 
problems occur.