Method for operating a contactor and related device

Abstract

The present disclosure relates to a method and apparatus for operating a contactor. A switching assembly is provided on at least one phase branch of the contactor, the switching assembly comprising a thyristor and an electromagnetic relay connected in parallel with the thyristor, the method comprising: in response to a closing instruction of the contactor, providing a trigger signal to a control electrode of the thyristor to make the thyristor conductive; detecting a current of the phase branch; determining a pull-in timing of the electromagnetic relay based on the current; and providing a trigger signal to the electromagnetic relay to make the electromagnetic relay close based on the pull-in timing. By controlling the closing timing of the electromagnetic relay, arcless closing of the relay is achieved in a low-cost manner, so as to improve the service life of the contactor.

Description

Technical Field

[0001] Embodiments of this disclosure generally include the control of contactors, and particularly relate to methods and apparatus for operating electrical equipment. Background Technology

[0002] Loads such as electric motors often include inductive loads. Traditionally, contactors are used to control the starting of electric motors. Due to the inductive characteristics of inductive loads, when the current flowing through the inductive load undergoes a transient change, an induced electromotive force (EMF) is generated across the inductive load. The value of this EMF is proportional to the inductance and the rate of change of current. This inductive characteristic of the electric motor affects the performance of the switching devices within the contactor, thus significantly impacting the contactor's lifespan. Improvements to the methods used to operate contactors are desired to increase their lifespan and / or performance. Summary of the Invention

[0003] Embodiments of this disclosure provide a method and apparatus for operating a contactor, aimed at solving one or more of the problems described above and other potential problems.

[0004] According to a first aspect of this disclosure, a method for operating a contactor is provided. A switching assembly is provided on at least one phase branch of the contactor, the switching assembly including a thyristor and an electromagnetic relay connected in parallel with the thyristor. The method includes: providing a trigger signal to the control electrode of the thyristor to turn on the thyristor in response to an on command of the contactor; detecting the current in the phase branch; determining a timing for the electromagnetic relay to engage based on the current; and providing a trigger signal to the electromagnetic relay to close the electromagnetic relay based on the engagement timing.

[0005] In some embodiments, determining the activation timing of the electromagnetic relay based on the current includes: determining the period of the current; determining the current zero-crossing point in the phase branch based on the period; and determining the activation timing of the electromagnetic relay based on the current zero-crossing point, such that the current in the phase branch is zero when the electromagnetic relay is activated.

[0006] In some embodiments, determining the activation timing of the electromagnetic relay based on the current zero-crossing point includes: acquiring the activation curve of the electromagnetic relay; determining the activation timing of the electromagnetic relay based on the activation curve; and determining the activation timing of the electromagnetic relay based on the activation timing and the current zero-crossing point.

[0007] In some embodiments, determining the activation timing of the electromagnetic relay based on the activation timing and the current zero-crossing point includes: determining the time difference between the period and the activation timing; and determining the activation timing of the electromagnetic relay based on the time difference.

[0008] In some embodiments, determining the engagement timing of the electromagnetic relay based on the time difference includes: in the next cycle immediately following the cycle of detecting the current, after the time difference has elapsed from the start of the next cycle, sending an engagement command to the electromagnetic relay.

[0009] In some embodiments, each phase branch of the contactor includes a switching assembly, each switching assembly including a corresponding thyristor and a corresponding electromagnetic relay connected in parallel with the corresponding thyristor, wherein each phase branch is controlled independently of each other.

[0010] In some embodiments, the contactor is configured to close the phase branch to start the motor.

[0011] In some embodiments, the contactor is configured to close the phase branch to initiate an inductive load.

[0012] According to a second aspect of this disclosure, an apparatus for operating a contactor is provided, wherein at least one phase branch of the contactor is provided with a switching assembly, the switching assembly including a thyristor and an electromagnetic relay connected in parallel with the thyristor, the apparatus comprising: a current sampling device for sampling current in the phase branch; and a controller communicatively connected to the current sampling device and configured to perform the method of the first aspect.

[0013] According to a third aspect of this disclosure, a motor starter is provided, including the means described in the second aspect.

[0014] According to a fourth aspect of this disclosure, a computer-readable medium is provided that stores computer-executable instructions thereon, which, when executed on a processor, perform the method according to the first aspect.

[0015] According to the method and apparatus for operating a contactor according to embodiments of the present disclosure, by controlling the closing timing of an electromagnetic relay, arc-free closure of the relay can be achieved at low cost, thereby improving the lifespan of the contactor. Attached Figure Description

[0016] The above and other objects, features, and advantages of embodiments of the present disclosure will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated in the drawings by way of example and not limitation.

[0017] Figure 1A schematic diagram of a system for controlling a load according to an embodiment of the present disclosure is shown.

[0018] Figure 2 A flowchart illustrating a method for operating a contactor according to an embodiment of the present disclosure is shown.

[0019] Figure 3 A flowchart illustrating a method for operating a contactor according to an embodiment of the present disclosure is shown.

[0020] Figure 4 A flowchart illustrating a method for operating a contactor according to an embodiment of the present disclosure is shown.

[0021] Figure 5 A schematic diagram is shown for determining the activation timing of an electromagnetic relay according to an embodiment of the present disclosure.

[0022] Figure 6 A block diagram of an apparatus capable of implementing several embodiments of the present disclosure is shown.

[0023] In the various figures, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0024] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0025] The term "comprising" and its variations as used herein signify an open-ended inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". Terms such as "upper", "lower", "front", and "rear", indicating placement or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are used only for the purpose of describing the principles of this disclosure, and are not intended to indicate or imply that the elements referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting this disclosure.

[0026] Figure 1A schematic diagram of a system 100 for controlling a load according to an embodiment of the present disclosure is shown. The load 50 may include a device with an inductive load. In some embodiments, the load 50 may be, for example, an electric motor. The system 100 may be, for example, a contactor or motor starter for controlling the starting and disconnection of the load 50. A contactor or motor starter is a device for assisting in starting an electric motor. It is worth noting that although the operating principle for controlling the starting of an inductive load according to an embodiment of the present disclosure is illustrated using a contactor as an example in the illustrated embodiment, this is merely exemplary, and the load 50 may include any other suitable device containing an inductive load. Furthermore, although the operation process is illustrated using a contactor as an example, the method described according to an embodiment of the present disclosure can be applied to other similar devices.

[0027] like Figure 1 As shown, system 100 may include three-phase power lines La, Lb, and Lc, each connected to an inductive load 50 (shown schematically in its entirety only in the figure). Each phase may be equipped with multiple switching components for controlling the operation of the load; each switching component may include a thyristor and an electromagnetic relay. It is worth noting that although the illustrated embodiment uses a three-phase electric motor as an example to illustrate the operating principle of the method and apparatus according to embodiments of this disclosure, this is merely exemplary; the apparatus and method according to embodiments of this disclosure can be applied to single-phase or two-phase power.

[0028] In the illustrated embodiment, for the La phase, at least one thyristor G1 and an electromagnetic relay U1 connected in parallel are provided in the power supply circuit. Similarly, for the Lb phase, a thyristor G2 and an electromagnetic relay U2 connected in parallel are provided in the power supply circuit; and for the Lc phase, a thyristor G3 and an electromagnetic relay U31 connected in parallel are provided in the power supply circuit.

[0029] System 100 may further include controller 20, input interface 40, and driver 30. Input interface 40 may be connected to controller 20 to provide control commands. Controller 20 may be configured to generate control commands, which may be translated via driver 30 to be suitable for driving switching components G1, U1; G2, U2; G3, U3. Although driver 30 is shown as a separate component in the illustrated embodiment, in other embodiments, driver 30 may be integrated into controller 20.

[0030] The operation of system 100 is as follows: After receiving the command to start load 50 at input interface 40, controller 20 sends a command to driver 30 to first close thyristors G1, G2, and G3. After thyristors G1, G2, and G3 are turned on, the power on each phase La, Lb, and Lc is supplied to load 50 through the switching devices via the branches of thyristors G1, G2, and G3. After closing thyristors G1, G2, and G3, controller 20 then sends a command to driver 30 to close electromagnetic relays U1, U2, and U3. After receiving the command from driver 30, electromagnetic relays U1, U2, and U3 close, short-circuiting thyristors G1, G2, and G3. Controller 20 then sends a command to the thyristors to open G1, G2, and G3. Thus, the power on each phase La, Lb, and Lc is supplied to load 50 via the branches of electromagnetic relays U1, U2, and U3.

[0031] The above system has the following advantages. Taking the operation of the La phase branch as an example, the operation of other phase branches is similar. Since the thyristor G1 and the electromagnetic relay U1 are connected in parallel and turned on sequentially, especially since the thyristor G1 turns on first and then the electromagnetic relay U1 closes, the electromagnetic relay U1 is only subjected to the voltage drop across the thyristor G1 when it is closed, which is, for example, about 1 to 2V; this avoids the impact on the performance of the electromagnetic relay U1 caused by excessive voltage drop.

[0032] The inventors of this disclosure have discovered that the above-mentioned operating timing can be further optimized to further improve the performance of system 100. The inventors have discovered that when the electromagnetic relay U1 operates at an arbitrary closing timing, the electromagnetic relay may close under conditions where a large current flows through the La phase branch, and this large current may generate an electric arc at the contacts of the electromagnetic relay. The continuous electric arc will erode the contacts and thus affect the lifespan of the electromagnetic relay.

[0033] The system 100 according to an embodiment of this disclosure may further include current sensing devices 10a, 10b, and 10c. The current sensing devices 10a, 10b, and 10c are configured to sense the current flowing through the corresponding phase current loops La, Lb, and Lc. The current sensing devices can be implemented in various ways, as long as current sensing is achieved. In some embodiments, the current sensing devices can be implemented as voltage divider resistors, Hall effect sensors, current transformers (CTs), magnetic sensors (TMRs), etc.

[0034] According to the embodiments of the present disclosure, the system 100 can achieve arc-free closure of the relay in a low-cost manner by controlling the closing time of the electromagnetic relay based on the current obtained by the current sensing devices 10a, 10b, 10c, and by controlling the closing time of the electromagnetic relay, thereby improving the lifespan of the system 100.

[0035] Figure 2A schematic flowchart of a method 200 for operating a contactor according to an embodiment of the present disclosure is shown. Method 200 may include the following actions: At block 202, in response to an on command of the contactor, a trigger signal is provided to the control electrode of a thyristor to turn on the thyristor. At block 204, the current in the phase branch is detected. At block 206, based on the current, the timing for the electromagnetic relay to engage is determined. At block 208, based on the engagement timing, a trigger signal is provided to the electromagnetic relay to close the electromagnetic relay.

[0036] Also combined Figure 1 Taking the La-phase branch as an example, after the input interface 40 inputs a command to the controller 20 to control the start of the load 50, the controller 20 can generate a corresponding control command and send the command to the driver 30. The driver 30 then drives the thyristor G1 to close. The controller 20 can sample the current of the La-phase branch through the current sensing device 10a and determine the timing of the electromagnetic relay's activation based on the sampled current. Based on the activation timing, the controller 20 sends a command to the driver 30 to cause the driver 30 to drive the electromagnetic relay to close at the activation timing. After the electromagnetic relay closes, the controller 20 then sends a command to the thyristors to disconnect G1, G2, and G3.

[0037] It is worth noting that although the method 200 for operating the contactor is described using the La phase branch as an example, other phase branches Lb and Lc can be performed independently of La and in a similar manner, and detailed descriptions of them are omitted.

[0038] The term "closing timing" here refers to the timing at which the contacts of an electromagnetic relay close, determined in a way that minimizes the arc generated when the contacts close. Considering that arc generation is related to the magnitude of the current flowing through the electromagnetic relay, the closing timing is determined such that the current flowing through the electromagnetic relay is equal to or less than a predetermined threshold, wherein the predetermined threshold may be related to the current of the arc generated when the electromagnetic relay is activated. In some embodiments, the closing timing is determined such that the current in the phase branch containing the electromagnetic relay is zero. Thus, according to the method of embodiments of this disclosure, the risk of arcing when the contacts of an electromagnetic relay close can be reduced by controlling the closing timing of the electromagnetic relay contacts.

[0039] Determining the timing of an electromagnetic relay's activation based on the sampled current can be achieved in various ways. Figure 3 A flowchart illustrating a method 300 for operating a contactor according to an embodiment of the present disclosure is shown. Figure 3 An example is shown that determines the activation timing of an electromagnetic relay based on a sampled current. Figure 3As shown, method 300 may include the following actions. At block 302, the period of the current is determined based on the sampled current. For example, multiple points (e.g., 3 points) may be sampled for the phase branch to determine the period of the current based on the sampling points. At block 304, the zero-crossing point of the current in the phase branch is determined based on the period. At block 306, the timing of the electromagnetic relay's activation is determined based on the current zero-crossing point, such that the electromagnetic relay activates at the current zero point in the phase line.

[0040] exist Figure 3 The embodiment exemplifies an example of determining the activation timing of an electromagnetic relay based on the period of the current in the phase branch. The advantage of this is that, considering the presence of an inductive load in load 50, the period of the current in the phase branch may fluctuate; by determining the current period and determining the activation timing based on the current period, the accuracy of the zero-crossing point determination can be ensured.

[0041] In other embodiments, the activation timing of the electromagnetic relay can be predetermined. This is applicable, for example, to situations where the phase branch is relatively stable, and can accurately determine when the current in the phase branch is at or near zero.

[0042] Figure 4 A flowchart illustrating a method for operating a contactor according to an embodiment of the present disclosure is shown. Figure 4 An embodiment is shown that determines the activation timing of an electromagnetic relay based on the current zero-crossing point. For example... Figure 4 As shown, method 400 may include the following actions: At block 402, the pull-in curve of the electromagnetic relay is obtained. At block 404, the pull-in timing of the electromagnetic relay is determined based on the pull-in curve. At block 405, the pull-in timing of the electromagnetic relay is determined based on the pull-in timing and the current zero-crossing point.

[0043] exist Figure 4 In the embodiment shown, the closing characteristics of the moving contact of the electromagnetic relay are considered in the timing of the electromagnetic relay's activation, thereby allowing for a more accurate determination of the current zero-crossing point or near-zero-crossing point of the phase branch.

[0044] In some embodiments, determining the activation timing of the electromagnetic relay based on the activation timing and the current zero-crossing point includes: determining the time difference between the period and the activation timing; and sending an activation command to the electromagnetic relay based on the time difference. In this case, the current zero-crossing closure of the electromagnetic relay can be conveniently achieved based on the time difference as a control parameter.

[0045] Figure 5 A schematic diagram illustrating a method for determining the activation timing of an electromagnetic relay according to an embodiment of the present disclosure is shown. Figure 5As shown, the upper figure represents the current curve 52 on the phase branch; the lower figure represents the current curve 54 of the electromagnetic relay coil. At point C1 (corresponding to time t3), the electromagnetic relay begins to perform the closing action; and at point C2 (corresponding to time t4), the electromagnetic relay reliably closes. In some embodiments, the timing t of the electromagnetic relay's activation is selected such that the closing point C2 of the electromagnetic relay coincides with or is close to the zero-crossing point of the current on the phase branch (time t4 in the figure) (in which case, although the current on the phase branch is not zero, the current value is small).

[0046] This is illustrated by taking the example of selecting the closing timing of the electromagnetic relay so that the closing point C2 of the electromagnetic relay coincides with the zero-crossing point of the current in the phase branch. Figure 5 The process diagram shown is as follows. Figure 5 As shown, the symbol T represents the current period, t1-t2 represents the first period, which is the period after the controller 20 receives the load start command from the input interface 40. In this period, the controller 20 can determine the period T of the phase current by sampling the phase current; t2-t4 represents the second period immediately following the first period.

[0047] The known activation timing of the electromagnetic relay can be obtained. Figure 5 The diagram shows the time corresponding to C1-C2. The time difference Δt can be calculated by subtracting the time interval from the period T. After the first cycle ends and the current zero-crossing point is determined, the drive signal for the electromagnetic relay is issued at time t after a delay of Δt. Through this operation, the contact point C2 of the electromagnetic relay corresponds to the zero-crossing point t4 of the current in the next cycle.

[0048] By issuing a closing command to the electromagnetic relay at time t, the relay engages at the current zero-crossing point t4 in the next cycle immediately following the first cycle. The advantage of this operation is that the electromagnetic relay can be closed as early as possible, avoiding excessively long on-time of the thyristor G1. Furthermore, considering the frequency fluctuations in the phase branch, control accuracy can be improved. It is worth noting that this is merely an example; the closing timing can be determined by considering any other suitable method based on the known engagement timing of the electromagnetic relay.

[0049] According to embodiments of this disclosure, each phase branch of the contactor includes a switching assembly, each switching assembly including a corresponding thyristor and a corresponding electromagnetic relay connected in parallel with the corresponding thyristor, wherein each phase branch is controlled independently of each other. This ensures that the electromagnetic relay in each phase branch can achieve zero-crossing start.

[0050] According to a second aspect of this disclosure, an apparatus for operating a contactor is provided, wherein at least one phase branch of the contactor is provided with a switching assembly, the switching assembly including a thyristor and an electromagnetic relay connected in parallel with the thyristor, the apparatus comprising: a current sampling device for sampling current in the phase branch; and a controller communicatively connected to the current sampling device and configured to perform the method described above.

[0051] Figure 6 A block diagram of a computing device 600 capable of implementing various embodiments of the present disclosure is shown. As shown, the device 600 includes a central processing unit (CPU) 601, which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) 602 or loaded from storage unit 608 into random access memory (RAM) 603. Various programs and data required for the operation of the device 600 may also be stored in RAM 603. The CPU 601, ROM 602, and RAM 603 are interconnected via bus 604. An input / output (I / O) interface 605 is also connected to bus 604.

[0052] Multiple components in device 600 are connected to I / O interface 605, including: input unit 606, such as keyboard, mouse, etc.; output unit 607, such as various types of monitors, speakers, etc.; storage unit 608, such as disk, optical disk, etc.; and communication unit 609, such as network card, modem, wireless transceiver, etc. Communication unit 609 allows device 600 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0053] Processing unit 601 executes the various methods and processes described above, such as methods 200, 300, 500, and 600. For example, in some embodiments, methods 200, 300, and 400 may be implemented as computer software programs tangibly contained in a machine-readable medium, such as storage unit 608. In some embodiments, part or all of the computer program may be loaded and / or installed on device 600 via ROM 602 and / or communication unit 609. When the computer program is loaded into RAM 603 and executed by CPU 601, one or more steps of process 200 described above may be performed. Alternatively, in other embodiments, CPU 601 may be configured to execute methods 200, 300, and 400 by any other suitable means (e.g., by means of firmware).

[0054] The functions described above in this document can be performed at least in part by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload programmable logic devices (CPLDs), and so on.

[0055] The program code used to implement the methods of this disclosure may be written in any combination of one or more programming languages. This program code may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may be executed entirely on a machine, partially on a machine, as a standalone software package partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0056] In the context of this disclosure, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0057] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0058] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with embodiments of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0059] Furthermore, although the operations are described in a specific order, this should be understood as requiring that such operations be performed in the specific order shown or in sequential order, or requiring that all illustrated operations be performed to achieve the desired result. In certain environments, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this disclosure. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

[0060] Although the subject matter has been described using language specific to structural features and / or methodological logic, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are merely illustrative examples of implementing the claims.

[0061] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for operating a contactor, wherein at least one phase branch of the contactor is provided with a switching assembly, the switching assembly comprising a thyristor and an electromagnetic relay connected in parallel with the thyristor, the method comprising: In response to the contactor's turn-on command, a trigger signal is provided to the control electrode of the thyristor to turn on the thyristor; Detect the current in the phase branch; Based on the current, determine the timing of the electromagnetic relay's activation; as well as Based on the stated engagement timing, a trigger signal is provided to the electromagnetic relay to close it, thereby short-circuiting the thyristor. The timing of the electromagnetic relay's activation based on the current includes: Determine the period of the current; Based on the period, determine the current zero-crossing point in the phase branch; and Based on the zero-crossing point of the current, the timing of the electromagnetic relay's activation is determined so that the current in the phase branch is zero when the electromagnetic relay is activated. The timing of the electromagnetic relay's activation, determined based on the current zero-crossing point, includes: Obtain the pull-in curve of the electromagnetic relay; Based on the pull-in curve, the pull-in duration of the electromagnetic relay is determined; and The timing of the electromagnetic relay's activation is determined based on the activation duration and the current zero-crossing point.

2. The method according to claim 1, wherein determining the activation timing of the electromagnetic relay based on the activation duration and the current zero-crossing point comprises: Determine the time difference between the cycle and the engagement duration; Based on the time difference, the timing of the electromagnetic relay's activation is determined.

3. The method according to claim 2, wherein determining the engagement timing of the electromagnetic relay based on the time difference comprises: In the next cycle immediately following the current detection cycle, after the time difference has elapsed since the start of the next cycle, an activation command is sent to the electromagnetic relay.

4. The method according to any one of claims 1-3, wherein each phase branch of the contactor includes a switching assembly, each switching assembly including a corresponding thyristor and a corresponding electromagnetic relay connected in parallel with the corresponding thyristor, wherein each phase branch is controlled independently of each other.

5. The method according to any one of claims 1-3, wherein the contactor is configured to close the phase branch to start the motor.

6. The method according to any one of claims 1-3, wherein the contactor is configured to close the phase branch to initiate an inductive load.

7. An apparatus for operating a contactor, wherein at least one phase branch of the contactor is provided with a switching assembly, the switching assembly comprising a thyristor and an electromagnetic relay connected in parallel with the thyristor, the apparatus comprising: A current sampling device is used to sample the current in the phase branch; as well as The controller is communicatively connected to the current sampling device and configured to perform the method according to any one of claims 1-6.

8. A motor starter comprising the device according to claim 7.

9. A computer-readable medium having stored thereon computer-executable instructions, which, when executed on a processor, perform the method according to any one of claims 1-7.

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