Rotary power transmission system for linear motor elevators

Abstract

Rotary power transmission system for linear motor elevators A rotary power transmission system for a linear motor elevator, characterized in that it comprises at least one rotor (2) with magnetic poles facing a stator coil (1) and attached to an elevator cabin, at least one generator (3) or set of secondary coils (5) connected to the rotor (2), and an excitation algorithm providing a moving excitation current to the section of the linear motor stator facing the rotor (2).

Description

[Technical field]

[0001] The present invention relates to the general field of elevator electrical engineering and has particular specific application to ropeless linear motor elevators. The power transmission system described in this invention provides low cost and reliable power transmission for ropeless linear motor elevators. It may be used by single car or multi-car linear motor elevators operating on straight, curved, or diverging tracks. [Background technology]

[0002] Self-propelled ropeless linear motor elevators offer various benefits such as the ability to operate several elevator cabins independently in the same hoistway, potentially on curved travel paths, etc. On the other hand, the traditional method of providing power via wire connections in the "traveling cable" is no longer available, and appropriate methods must be developed to provide the power required for lighting, ventilation, door operation, etc. in the cabins.

[0003] A commonly used wireless power transfer method uses electromagnetic connection between coils and / or wire loops installed in the elevator cabin and the hoistway side. The connection is usually realized by high frequency excitation of the order of 100 kHz or higher, and the coupling is made efficient by resonance. Although this method can provide the required power transfer, it has the disadvantage that the hoistway side coil, which runs the entire length of the hoistway, is a separate device, thus requiring high initial and maintenance costs, and also increasing the number of potential failure points.

[0004] Instead of providing a separate device for electromagnetic field generation, it would be advantageous to use the already available coils of the linear motor stator. Unfortunately, however, it is not feasible to directly couple the secondary coils to the stator coils: In the case of high frequency electromagnetic coupling, for example, the solid wire of the stator coils common in resonant power transfer has a very high effective resistance due to the skin effect making power transfer impractical. It would be necessary to use Litz wire in the stator, but this is not practically feasible due to cost, strength, and other considerations. For low frequency couplings such as those used in motor operation, the transformer formed by the stator coils and the cabin secondary coil would have very high transfer impedance due to the effective air gap, thus also making power transfer impractical. To create an effective transformer would require an iron core, which is undesirable for linear motor elevators due to cost, cogging torque, attractive forces, and other issues.

[0005] The abstract of the prior art patent application with publication number US10531256B2 is as follows; "An elevator system includes an elevator car disposed in and arranged to move along a hoistway. A linear propulsion system of the elevator system is constructed and arranged to propel the elevator car and includes a plurality of primary coils engaged with and distributed along a hoistway defined by a generally stationary structure. A wireless power transfer system of the elevator system is configured to inductively transfer power to the elevator car. The wireless power transfer system includes a secondary coil mounted on the elevator car and configured to be induced by an electromotive force from the primary coil and to output power for use by the elevator car. A communication system of the elevator system is configured to exchange communication data signals utilizing the secondary coil and the plurality of primary coils." As can be seen, this prior art document fails to provide a solution to the above-mentioned disadvantages.

[0006] As a result, due to the above-mentioned disadvantages and inadequacies of existing solutions, improvements are needed in the art. [Objective of the Invention]

[0007] The present invention aims to provide a method with different technical characteristics that are different from the implementations used in the industry and bring a new perspective to this field.

[0008] SUMMARY OF THE PRESENT EMBODIMENT It is a primary object of the present invention to provide a low cost, reliable power transmission solution for linear motor elevators that use stator coils as part of the system.

[0009] A system for rotary power transfer for linear motor elevators is disclosed. The system allows for practical power transfer to elevator cabins by reusing existing linear motor stator coils for the secondary purpose of power transfer. The disclosed system provides safe and reliable power transfer for single or multi-car linear motor elevators.

[0010] In order to achieve the above object, the present invention provides at least one rotor with magnetic poles facing the stator coil and attached to the elevator cabin; at least one generator or secondary coil set connected to the rotor; an excitation algorithm for providing a moving excitation current to the section of the linear motor stator facing the rotor; A rotary power transmission system for a linear motor elevator, comprising:

[0011] The structural and unique features and all advantages of the present invention will become more apparent from the following figures and detailed description made with reference to these figures, and therefore an evaluation should be made with reference to these figures and detailed description. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 shows a schematic of a portion of a preferred embodiment with a generator connected to a rotor. [Diagram 2]FIG. 13 shows an extended embodiment with two rotors facing each other across the linear motor stator coils. [Diagram 3] FIG. 13 shows a schematic of a portion of another preferred embodiment with a secondary coil set surrounding the rotor.

[0013] The drawings are not necessarily to scale and may omit details that are not necessary for understanding the invention. Furthermore, elements that are at least substantially identical or at least substantially identical in function are designated with the same numbers. [Explanation of symbols]

[0014] 1. Stator coil 2 Rotors 3. Generator 4 Secondary rotor 5 Secondary coil 6. Mover 7. Magnets 8. Magnetic Flux 9 Rotations DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following is a detailed description of exemplary embodiments to illustrate the principles of the present invention. The embodiments are provided to illustrate aspects of the present invention, but the present invention is not limited to any embodiment. The scope of the present invention encompasses numerous alternatives, modifications, and equivalents; it is limited only by the scope of the claims.

[0016] In order to provide a thorough understanding of the present invention, numerous specific details are set forth in the following description. However, the present invention may be practiced according to the claims without some or all of these specific details. For the purposes of clarity, technical matters known in the art related to the present invention have not been described in detail so as not to unnecessarily obscure the present invention.

[0017] Figure 1 shows an overview of the preferred embodiment: a rotor (2) with a connected generator (3) facing the stator. It shows a cross-section of the stator coils (1) and rotor (2) and a front view of the rotor (2) with a generator (3) attached to its shaft and facing the stator.

[0018] Figure 2 shows an overview of another preferred embodiment, two rotors (2) with a connected generator (3) separated by a stator. It shows a cross-section of the stator coil (1) and two rotors (2) facing each other across the stator.

[0019] Fig. 3 shows a schematic of yet another preferred embodiment: rotor (2) with secondary coils (1). Fig. 3 shows a cross-sectional view of the stator coil (1), rotor (2) and a set of secondary coils (5).

[0020] The rotary power transmission system that is the subject of the present invention is used in linear motor drive systems and ropeless single-car or multi-car linear motor elevator systems having one or more elevator cabins. The term "linear motor elevator drive" defines a stator or multiple stators and a mover or multiple movers that together are capable of holding and moving an elevator cabin or multiple elevator cabins.

[0021] A three-phase excitation current in the stator coil (1) generates a moving magnetic field capable of driving a magnetic rotor (2). The rotor (2) with alternating magnetic poles is placed facing the stator coil (1) and rotates simultaneously with the moving magnetic field. The rotor (2) is mounted on a linear motor mover (6) and moves therewith. A generator (3), usually a three-phase permanent magnet synchronous generator, is mounted on the shaft of the rotor (2) and generates output power. A secondary rotor (4), usually identical to the rotor (2), is placed on the other side of the stator coil (1) to close the path of the magnetic flux (8) and increase the magnetic field strength inside the stator coil (1). A set of secondary coils (5) are placed near, and preferably around, the rotor (2), enabling the rotor (2) to perform two roles: first, as a synchronous motor rotor (2) cooperating with the stator coils (1); and second, as a synchronous generator rotor (2) cooperating with the secondary coils (5).

[0022] The linear motor stator coils (1) are arranged in sections that are to be driven independently of each other by a three-phase inverter. In this arrangement, the stator coils (1) that are not required for generating forces with the mover (6), i.e. not facing the mover (6), are available for a secondary role of driving the rotor (2). During operation of the linear motor, the stator coils (1) are available behind the mover (6) as the mover (6) moves along the stator. When the stator coils (1) are driven by a three-phase current with a rotating phasor, the generated moving magnetic field interacts with the magnets (7) of the rotor (2) or the composite magnets (7) of the rotor (2) and the secondary rotor (4) to rotate it or them simultaneously. The direction of rotation (9) of the rotor (2) can be changed if the direction of the magnetic flux (8) is changed. The generator (3) attached to the rotor (2) will also rotate and generate a voltage and, in the case of a finite load, also a current. This voltage and current is available for use on the mover (6) side as contactless transmitted power. Meanwhile, while the rotor (2) and the secondary rotor (4) are rotating, a voltage and current is induced across the terminals of the secondary coil (5), thus providing additional power transfer.

[0023] A rotor (2) is generally defined to include any type of rotating or circulating device equipped with magnetic poles capable of interacting with the moving magnetic field of the linear motor stator coils (1). The pole pitch of the magnetic poles of the rotor (2) is set approximately equal to the pole pitch of the linear motor stator or a portion thereof.

[0024] The generator (3) is an electrical generator connected to the shaft of the rotor (2) and may operate as a synchronous generator, a DC generator, an asynchronous generator, or a similar device suitable for converting rotational motion into electrical energy.

[0025] The secondary coil (5) set is energized by the rotating magnetic field of the rotor (2) and acts as a synchronous generator (3), an electrical generator.

[0026] A rotor (2) or multiple rotors (2) are mounted on a linear motor mover (6) supporting the elevator cabin with their axis of rotation (9) parallel to the linear motor stator coils (1) and their surfaces are at a close distance from the surfaces of the stator coils.

[0027] During operation, when there is a need to generate electrical power for the elevator cabin, the linear motor stator coils (1) facing the rotor (2) are energized with three-phase current to generate a moving magnetic field along the stator. This moving magnetic field interacts with the magnetic poles of the rotor (2) causing it to rotate. The rotation (9) drives the generator (3), which generates electrical power that is available to the elevator cabin.

[0028] When the linear motor mover (6) is fixed, and thus the rotor (2) is in a fixed position relative to the stator, the excitation will be in the stator coils (1) facing the rotor (2). When the linear motor mover (6) is moving, the stator coils (1) facing the rotor (2) will change, and the excitation will need to follow the movement of the rotor (2) along the stator.

[0029] For the rotor (2) to operate as a synchronous motor, the phase of the excitation needs to be synchronized with the phase angle of the rotor (2). If there is only a small torque acting on the rotor (2) from the generator (3), the synchronism can be achieved automatically by the magnetic torque acting between the stator and the rotor (2). However, it is generally necessary to provide a means to synchronize the stator current with the rotor (2) angle. One simple means of achieving this is to use a sensorless vector control algorithm, common, for example, in ESC (Electronic Speed ​​Controller) inverters used in RC (Radio Control) model cars or drones.

[0030] The generated voltage will be proportional to the rotational speed of the rotor (2), which is proportional to the frequency of the stator excitation. This frequency can be set according to the required power transfer and increase it when more power is required. During the movement of the linear motor mover (6), the speed of the rotor (2) will be determined by the difference between the linear travel speed and the excitation frequency. This needs to be taken into account when controlling the excitation frequency to set the transferred power.

[0031] In general, it is preferable to use a rotor (2) with a small number of poles. One reason is that it allows for a relatively high rotational speed at a relatively low excitation frequency. Another reason is that those poles are more effective at coupling the stator magnetic field to the rotor (2) that faces directly towards the stator; if the diameter of the rotor (2) and its number of poles are large, there will be many poles that face away from the stator and therefore do not contribute to the operation.

[0032] To improve the magnetic path of the rotor (2) poles, it is advantageous to install two rotors (2) spaced apart by the stator coils (1) as shown in Figure 2. This increases the strength of the magnetic field across the stator and therefore results in higher torque for the same stator current. A further arrangement might use four rotors (2), two tandem on each side (not shown) to provide an even lower reluctance to the magnetic field.

[0033] Other pole arrangements are also possible, for example by using a rotor axis perpendicular to the stator surface to achieve motion of the rotor (2) magnets parallel to the stator surface. Such variations are easily designed by engineers familiar with the operation of linear and rotary motors, and therefore, they are within the scope of the present invention.

[0034] If the generator (3) is a three-phase synchronous generator, the generated AC voltage will usually be rectified and the resulting DC voltage will be conditioned by feeding it to a DC / DC converter. The resulting voltage will be used to drive the cabin equipment. A wireless signal can be transmitted from the cabin to the stator side to inform the stator control about the generated voltage; if necessary, the stator control will control the excitation of the stator coils (1) to increase or decrease the rotor (2) speed.

[0035] The disclosed embodiments are exemplary and not limiting. While a specific configuration of a rotary power transmission system has been described, it is understood that the present invention can be applied to a wide variety of elevator systems. There are many alternative ways of implementing the present invention, including but not limited to having different arrangements for the rotor (2). The present invention is also suitable for linear motor elevators with non-linear (curved) motion paths, or for motion along branching paths with switches. (Other possible items) (Item 1) At least one rotor (2) with magnetic poles facing the stator coil (1) and attached to the elevator cabin; At least one generator (3) or secondary coil (5) set connected to the rotor (2); an excitation algorithm for providing a moving excitation current to a section of the linear motor stator facing said rotor (2); A rotary power transmission system for a linear motor elevator comprising: (Item 2) Many elevator cabins are installed in the same hoistway, Each elevator cabin is equipped with a rotary power transmission device, Each of the rotary power transmission devices is arranged to be driven by the same stator coil (1). 2. The rotary power transmission system according to item 1. (Item 3) 2. The rotary power transfer system according to claim 1, wherein a secondary rotor (4), usually identical to the rotor (2), is placed on the other side of the stator coil (1) to close the path of the magnetic flux (8) and increase the magnetic field strength inside the stator coil (1). (Item 4) Linear motor drive system, Elevator Cabin 2. The rotary power transmission system according to item 1, used in a ropeless linear motor elevator system. (Item 5) Linear motor drive system, Multiple elevator cabins 3. The rotary power transmission system according to item 1 or 2, for use in a ropeless, multi-car, linear motor elevator system.

Claims

1. at least one rotor with magnetic poles facing the stator coil and attached to the elevator cabin; at least one generator or secondary coil set connected to the rotor; an excitation algorithm for providing a moving excitation current to a section of a linear motor stator facing said rotor; A rotary power transmission system for a linear motor elevator comprising:

2. Many elevator cabins are installed in the same hoistway, Each elevator cabin is equipped with a rotary power transmission device, Each of said rotary power transfer devices is arranged to be driven by the same stator coil.

10. The rotary power transmission system of claim 1.

3. 2. The rotary power transfer system of claim 1, wherein a secondary rotor, normally identical to the rotor, is placed on the other side of the stator coil to close the magnetic flux path and increase the magnetic field strength inside the stator coil.

4. Linear motor drive system, Elevator Cabin 13. The rotary power transmission system of claim 1 for use in a ropeless linear motor elevator system comprising:

5. Linear motor drive system, Multiple elevator cabins 3. The rotary power transmission system of claim 1 or 2 for use in a ropeless, multi-car, linear motor elevator system comprising:

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