EP1480230B1 - Linear motor with a winding - Google Patents

Abstract

An electrical cable for a linear motor comprises a conductor (6) surrounded by an inner electrically conductive layer (7), an isolation layer (8), an outer conductive layer (9), a conductive intermediate layer (11) formed of a band whose resistance is adjustable between 1 and 30 ohm/m and a cover layer (10) of conductively rendered isolating material. An independent claim is also included for a winding for a linear motor comprising a cable as above.

Description

The invention relates to a linear motor according to the preamble of claim 1 ( DE 196 38 603 A1 ).

Linear motors have long been known for electric drives of various types. There are both DC and AC synchronous and asynchronous motors. In the linear motor, both a fixed stator and a movable rotor part, in contrast to the conventional motor are not circular, but arranged in a straight line. The electrical energy is converted in a linear motor so into mechanical energy that it is directly usable for a translational movement. Areas of application for a linear motor are, for example, passenger transport, conveying and transport, assembly lines, luggage transport, mining, cranes, towing systems, carriages of machine tools and the operation of gate valves. In principle, the linear motor can have an excitation winding arranged in the slots of an inductor, which is designed to be three-phase with alternating current. The rotor part then consists either of a rail of electrically good conductive material, such as copper or aluminum (asynchronous motor), or of permanent magnetic material (synchronous motor).

If such a linear motor is used for example for driving a maglev train for the Fernschnellverkehr, then results for the inductor and thus also for the attached in its grooves cable a very long length. Since such a linear motor is operated for this reason with a relatively high electrical voltage, the cables with an inner and a outer conductive layer and a screen to be equipped. The shield of such cables, designed as medium-voltage cables, is required for safe guidance of capacitive charging currents, ground fault detection, fault location and protection against mechanical damage to the layers surrounding the conductor. He should also protect living beings from the risk of high voltages.

When using medium voltage cables with the described structure in the very long, consisting of inductor and cables stator of a linear motor, a high withstand voltage is induced on the shields of the cable, which can be far more than 1 kV, for example, with a length of the stator of 100 m. So that such high voltages can not occur, the screens could be divided into very short sections and each section grounded on one side. This is cumbersome and expensive and increases the risk of cable faults. With known shielded medium voltage cables, small parasitic voltages could also be achieved by earthing the shields at either end of a section of almost any length, or by connecting the shields of the three cables used for the winding at almost random intervals. But then large shield currents would flow, which would cause large energy losses and act as eddy current brake.

From the DE 30 06 382 A1 is known a three-phase AC winding for a linear motor, which consists of electrical medium voltage cables according to the described structure. The cables used here have an outer, made of electrically conductive insulating material jacket. At least on one side of the stator is in the region of the projecting from the grooves end windings of the cable extending over the entire length of the stator extending, with the conductive sheaths of the cable in good contact and connectable to ground strand of electrically good conductive material arranged. The electrically conductive made coats of cable simultaneously represent their screen, which has a relatively low electrical conductivity. The combination of the sheaths with the strand connected to earth potential results in an overall shield, which ensures a good dissipation of capacitive currents and also ensures that currents resulting from induced voltages remain small. The winding thus has Overall, a low power loss and the field influence is negligible. In addition, since no high electrical voltages can occur, a threat to living things is avoided.

In the known cable according to the above-mentioned DE 196 38 603 A1 is between the outer conductive layer and the outer electrically conductive jacket made over the entire length of the cable extending, completely enclosed metal insert as an intermediate layer present, through which the electrical conductivity of the shield of the cable is increased. It should be achieved that in the screen induced electrical voltages and currents, by which the drive power of the linear motor could be reduced, are kept as low as possible. In addition, the longitudinal resistance along the cable axis should be homogeneous due to the metal insert, and the detection of a ground fault as well as the discharge of fault currents should be ensured to a sufficient extent with reduced effort. This is also achieved with this known cable in many applications. Nevertheless, it can happen that the cable is damaged especially at high operating voltage.

The invention has for its object to make the line motor described above so that it can be easily adapted to different operating voltages, so that damage to its winding can be excluded by excessive operating voltages.

This object is achieved according to the characterizing features of claim 1.

In this winding electrical cables are used as winding strands, in which the electrical resistance of the screen to the respective requirements in a simple manner adaptable. The structure of the cables, the manufacturing process and the equipment used for this purpose can remain unchanged. The tape used for the intermediate layer increases the conductivity of the screen of the cables to such an extent that it can carry sufficiently high currents to ensure easy and rapid detection of a ground fault. The tape can be used as a Hybrid band be executed with plastic threads and metallic wires or consist of a single unit combined carbon fibers. The resistance value of the shield remains so high that no high-loss, low-impedance secondary circuits result. Losses due to voltages and currents induced in the screen of the cables are negligible compared to other line losses. The resistance value of the band is adjusted in each case so that it is sufficiently high for the particular application of the cable or the winding produced from the same. It will in any case be set higher than the resistance value of the earth conductor in good contact with the conductive sheaths of all three cables. Regardless of the operating voltage used for the linear motor then error and balancing currents are safely dissipated via the ground wire. The cables and in particular their outer shells are effectively protected in this way against damage from excessive currents. This also applies to large temperature differences to which the cables are exposed during operation, day and night and in different seasons. The band of the intermediate layer keeps its resistance value set during manufacture with great accuracy even then.

Embodiments of the subject invention are illustrated in the drawings.

• Fig. 1 ein zu einem mäanderförmigen Wicklungsstrang gebogenes Kabel für die Wicklung nach der Erfindung.
• Fig. 2 das Kabel selbst mit abschnittsweise sichtbaren Schichten seines Aufbaues.
• Fig. 3 bis 8 unterschiedliche Anordnungen eines im Kabelaufbau vorhandenen Hybridbandes.

Show it:

• Fig. 1 a bent to a meandering winding strand cable for the winding according to the invention.
• Fig. 2 the cable itself with sections visible layers of its structure.
• Fig. 3 to 8 different arrangements of existing in cable construction hybrid band.

1 with the inductor of a linear motor is called, which forms the stator of the same together with a three-phase winding. The inductor 1 consists of laminated cores in which grooves 2 are mounted for receiving winding strands of the winding. The stator is elongated. It can be many kilometers long. The winding strands consist in the present case of electrical cables whose more accurate structure, for example Fig. 2 evident.

In Fig. 1 a cable 3 is shown, which is fastened with a meandering course in the grooves 2 of the inductor 1. The unoccupied grooves 2 of the inductor 1 are provided for receiving two further cables having the same construction as the cable 3. They are not shown for the sake of simplicity. The three cables together form the three-phase winding of the linear motor. The cable 3 is constructed so that it is easy to deform to the meandering course and without additional effort its shape in the lying outside of the inductor 1 areas - the winding heads 4 - maintains. On at least one side of the inductor 1 extends over its entire length serving as a grounding metallic strand 5 of electrically good conductive material, which is in good electrical contact with the cables and can be connected to Erdpotentiel.

• Der Leiter des Kabels 3 ist als Leiterseil 6 ausgebildet, das aus einer Vielzahl von Einzeldrähten gebildet ist. Es sind mindestens zwei Lagen von Einzeldrähten vorhanden.
• Die Schlagrichtung der Verseilung in diesen beiden Lagen soll entgegengesetzt sein. Für den Fall, daß mehr als zwei Lagen vorhanden sind, sollen sie abwechselnd entgegengesetzte Schlagrichtung aufweisen. Das Leiterseil 6 kann aus Aluminiumdrähten bestehen. Es könnten aber auch Kupferdrähte oder Drähte aus einem Aluminium-Kupfer-Verbund verwendet werden.

The cable 3 used for the winding according to the invention, as well as the other two cables, for example, has the following structure:

• The conductor of the cable 3 is formed as a conductor 6, which is formed from a plurality of individual wires. There are at least two layers of individual wires.
• The impact direction of the stranding in these two layers should be opposite. In the event that more than two layers are present, they should have alternately opposite direction of impact. The conductor 6 may consist of aluminum wires. However, copper wires or wires made from an aluminum-copper composite could also be used.

The conductor cable 6 is surrounded by an inner conductive layer 7, which may be extruded onto the same. The extrusion process is adjusted so that the material of the conductive layer 7 also penetrates into the gusset, which are present between the individual wires of the outer layer of the conductor 6. The conductive layer 7 is thereby firmly connected to the conductor 6, since it anchors to the same. The interference fit is so good that the conductive layer 7 is released from the conductor 6 either by bending or by axial stress. For the inner conductive layer 7, a material based on EPDM (ethylene-propylene-diene monomer) may preferably be used. This is a material based on a copolymer of ethylene and propylene. The base material becomes highly active carbon black added. That can be a Leitruß alone. It is also possible to use several conductive carbon blacks in the blend.

Over the inner conductive layer 7, an insulation 8 is arranged, which can also be applied in the same operation by extrusion. The insulation 8 consists for example of a mixture based on EPR (ethylene-propylene rubber). Also in the same operation, an outer conductive layer 9 can be extruded onto the insulation 8, for which the same material as for the inner conductive layer 7 can be used. By anchoring the inner conductive layer 7 on the conductor 6 results for the three firmly interconnected layers 7, 8 and 9 in total so good a tight fit on the conductor 6 that these layers are immovable even when assembling sets of cables.

The cable 3 has an outer jacket 10 made of a conductive plastic. It is also applied by extrusion. As materials for the shell 10 are, for example, polymers based on acetate copolymers of ethylene, for example, have an acetate content of 30% to 70%. Highly conductive carbon blacks are added to these polymers, preferably in combination

Between the outer conductive layer 9 and the conductive shell 10, an electrically conductive intermediate layer 11 is arranged, whose electrical resistance is between 1 Ω / m and 30 Ω / m. The intermediate layer 11 consists of a band H ( Fig. 3 to 8 ). For example, it may be a hybrid tape in which plastic threads and metallic wires of variable composition are joined together. The electrical resistance per unit length of such a hybrid band is thereby changed. It can be adjusted within the specified limits in the production of the hybrid band, for example using the so-called Rascheltechnik, and so adapted to the respective requirements in a simple manner. As materials for the plastic threads, for example, polyamide, polyaramide or glass are suitable. The metallic wires are preferably made of copper. The hybrid tape can be made in any width and length. For example, the width may be between 10 mm and 150 mm for use in cables. The same advantages apply to a band H consisting of unitary carbon fibers.

The desired value for the electrical resistance of the band H is given to the manufacturer of the same by the manufacturer of the cable. The band H supplied by the manufacturer then has the value required for its purpose between 1 Ω / m and 30 Ω / m. To achieve this, the manufacturer of the band H has different possibilities. Thus, to adapt the electrical resistance of the strip H to the predetermined values, the number of metallic wires can be variable compared to the number of plastic threads. The diameter of the metallic wires can also be varied. The metallic wires may also be electrically either in series or parallel to each other over a predetermined length of the band H. They can also be arranged alternately both in series and parallel to each other.

• Gemäß Fig. 6 ist das Band H so um die äußere Leitschicht 9 des Kabels 3 herumgewickelt, daß seine Kanten einander überlappen. Die Überlappung Ü kann beispielsweise zwischen 2 mm und 8 mm betragen. Das Band H selbst kann als Wickelband 10 mm bis 80 mm breit sein.

The band H may be either wound around the outer conductive layer 9 or formed around in the longitudinal direction to form the intermediate layer 11, as shown in FIGS Fig. 3 to 8 is reproduced:

• According to Fig. 6 the band H is wound around the outer conductive layer 9 of the cable 3 so that its edges overlap one another. The overlap Ü may for example be between 2 mm and 8 mm. The band H itself can be as wrapping tape 10 mm to 80 mm wide.

The band H can according to Fig. 4 also be wrapped around the outer conductive layer 9 so that its edges abut each other. This results in a heel-free, closed all around and in the longitudinal direction of the cable intermediate layer 11th

An uninterrupted intermediate layer 11 is given even if the tape H according to Fig. 5 with gap L wound around its outer conductive layer 9 between its edges.

The same situation arises when the band H is longitudinally formed around the outer conductive layer 9 of the cable 3, according to Fig. 6 with overlapping, longitudinal edges (overlap Ü) or according to Fig. 7 with abutting edges or according to Fig. 8 with gap L between the edges. For this longitudinal shaping, a wider band H with a width of 80 mm to 150 mm can be used. Decisive here is the diameter of the respective cable over the outer conductive layer. 9

Claims (3)

1. Winding for a linear motor, comprising three electrical cables (3) arranged in grooves (2) of an elongated inductor (1), wherein the three electrical cables have an electrically conductive sheath (10) and a metal comprising intermediate layer (11) arranged between the sheath and an outer conductive layer (9), and wherein at least one metal strand (5) of an electrically highly conductive material that has electrically highly conductive contact with the conductive sheaths of the cable and serves as a grounding conductor is present over the whole length of the stator, said stator including the inductor (1) and the three cables (3), characterized in

   - that the intermediate layer (11) comprises a ribbon (H), the value of resistance per unit of length of the ribbon being between 1 Ωm and 30 Ω/m, and

   - that the value of electrical resistance of the intermediate layer (11) is greater than the corresponding resistance value of the strand (5) used as the grounding conductor.
2. Winding according to claim 1, characterized in that the ribbon (H) is a hybrid ribbon which comprises plastic fibers and metallic wires that are connected to a unit.
3. Winding according to claim 1, characterized in that the ribbon (H) comprises carbon filaments which are combined to a unit.

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