Method and apparatus for condition monitoring of an electric motor for a system

Abstract

The application provides a method and device for monitoring the state of a motor of a system, the method comprising: monitoring state information of the motor; determining whether the state of the motor changes from running to slowing down according to the state information of the motor; if the determination result is yes, monitoring whether the state of the motor changes from slowing down to starting; if the state of the motor is monitored to change from slowing down to starting, triggering at least one protection mechanism of the motor corresponding to the state after the motor starts. After a fast switching device switches a power supply device, whether the motor restarts can be accurately identified, and then the correct protection mechanism can be corresponded to.

Description

Technical Field

[0001] This invention relates to the field of power systems, and in particular to a method and apparatus for monitoring the status of motors in a system. Background Technology

[0002] Currently, electric motors are widely used in various industrial applications. An electric motor is a device that converts electrical energy into mechanical energy. After being connected to the power system, the power system provides power to the motor to ensure its normal operation. In addition, motor protection technology provides protection for the motor. Motor protection technology needs to identify the motor's state, such as whether it is in a starting or running state, so that different protection mechanisms correspond to different states, such as enabling / disabling certain protection mechanisms. For example, overload protection is disabled when the motor is in a starting state, and the restart inhibit function is enabled when the motor is in a stopped state. Therefore, it is necessary to correctly identify the motor's state. Summary of the Invention

[0003] In view of this, the present invention proposes a method for monitoring the status of an electric motor in a system, the system comprising two power supply devices capable of supplying power to the electric motor and a power switching device, the power switching device being capable of triggering a switching between the two power supply devices, the method comprising: monitoring the status information of the electric motor;

[0004] The method further includes:

[0005] Determine whether the motor's state changes from running to gradually slowing down based on the motor's state information;

[0006] If the result is confirmed to be yes, then monitor whether the state of the motor changes from slowing down to starting.

[0007] If the state of the motor is monitored to change from slowing down to starting, at least one protection mechanism of the motor is triggered corresponding to the state after the motor starts.

[0008] Optionally, according to the method described above, the state of the motor can be monitored to change from slowing down to starting:

[0009] Monitor the frequency or speed of the motor;

[0010] If it is detected that the frequency or speed of the motor is gradually increasing, then it is determined that the state of the motor changes from slowing down to starting.

[0011] Optionally, identifying whether the frequency of the motor gradually increases, according to the method described above, includes:

[0012] Determine whether the frequency of the motor meets the following conditions:

[0013] f(n)–f(n-2)>0 and f(n-1)-f(n-2)>0,

[0014] Where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor;

[0015] If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

[0016] Optionally, according to the method described above, determining whether the state of the motor changes from running to slowing down based on the motor's state information includes:

[0017] Determine whether the frequency of the motor meets the following conditions:

[0018] f shows a decreasing trend and the rate of change of f is ≤ a first preset threshold, where f is the frequency of the motor;

[0019] If the result is yes, the state of the motor changes from running to gradually slowing down.

[0020] Optionally, according to the method described above, it also includes:

[0021] Determine whether the state of the motor meets the following conditions:

[0022] Imax < Factor × Irat and I shows a decreasing trend;

[0023] Where Imax represents the largest current in each phase of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor.

[0024] If the judgment result is yes, then the motor's state changes from starting to running.

[0025] Optionally, according to the method described above, the power switching device is a fast switching device, or the frequency is the current frequency of the motor stator or the voltage frequency of the motor stator.

[0026] This invention provides a status monitoring device for an electric motor in a system. The system includes two power supply devices capable of supplying power to the electric motor and a power switching device. The power switching device can trigger a switching between the two power supply devices. The device includes: a first monitoring unit for monitoring the status information of the electric motor.

[0027] The device further includes:

[0028] A first determining unit is used to determine whether the state of the motor changes from running to slowing down based on the state information of the motor. If the determination result is yes, a second monitoring unit is triggered.

[0029] The second monitoring unit is used to monitor whether the state of the motor changes from slowing down to starting. If the state of the motor changes from slowing down to starting, a triggering unit is triggered.

[0030] The triggering unit is used to trigger at least one protection mechanism of the motor corresponding to the state after the motor starts.

[0031] Optionally, according to the apparatus described above, the second determining unit is specifically used for:

[0032] Monitor the frequency or speed of the motor;

[0033] If it is detected that the frequency or speed of the motor is gradually increasing, then it is determined that the state of the motor changes from slowing down to starting.

[0034] Optionally, according to the apparatus described above, the second determining unit, when identifying whether the frequency of the motor is gradually increasing, is specifically used for:

[0035] Determine whether the frequency of the motor meets the following conditions:

[0036] f(n)–f(n-2)>0 and f(n-1)-f(n-2)>0,

[0037] Where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor;

[0038] If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

[0039] Optionally, according to the apparatus described above, the first determining unit is specifically used for:

[0040] Determine whether the frequency of the motor meets the following conditions:

[0041] f shows a decreasing trend and the rate of change of f is ≤ a first preset threshold, where f is the frequency of the motor;

[0042] If the result is yes, the state of the motor changes from running to gradually slowing down.

[0043] Optionally, the apparatus described above may further include a second determining unit, the second determining unit being used to:

[0044] Determine whether the state of the motor meets the following conditions:

[0045] Imax < Factor × Irat and I shows a decreasing trend;

[0046] Where Imax represents the largest current in each phase of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor.

[0047] If the judgment result is yes, then the motor's state changes from starting to running.

[0048] Optionally, according to the device described above, the power switching device is a fast switching device, or the frequency is the current frequency of the motor stator or the voltage frequency of the motor stator.

[0049] The present invention also provides a status monitoring device for a motor of a fast-switching device. The system includes two power supply devices capable of supplying power to the motor and a power switching device, wherein the power switching device can trigger a switching between the two power supply devices. The monitoring device includes:

[0050] At least one memory for storing instructions;

[0051] At least one processor is configured to execute, according to instructions stored in the memory, a method for monitoring the state of an electric motor for a system as described in any of the preceding claims.

[0052] The present invention also provides a readable storage medium storing machine-readable instructions, which, when executed by a machine, enable the machine to perform a motor state monitoring method for a system as described in any of the preceding claims.

[0053] According to the present invention, after the fast-switching device switches the power supply equipment, it can accurately identify whether the motor has restarted, and thus correspond to the correct protection mechanism, avoiding inadequate protection and improving the reliability of motor protection. Attached Figure Description

[0054] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which will make the above and other features and advantages of the present invention more apparent to those skilled in the art. In the drawings:

[0055] Figure 1 This is a flowchart illustrating a method for monitoring the status of an electric motor in a system according to an embodiment of the present invention.

[0056] Figure 2A This is a flowchart illustrating a method for monitoring the state of an electric motor in a system according to another embodiment of the present invention.

[0057] Figure 2B This is a schematic diagram of a motor state transition mechanism according to an embodiment of the present invention.

[0058] Figure 3A This is a schematic diagram of the structure of a motor status monitoring device for a system according to an embodiment of the present invention.

[0059] Figure 3B This is a schematic diagram of the structure of a motor status monitoring device for a system according to another embodiment of the present invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the present invention clearer, the following embodiments are provided to further illustrate the present invention in detail.

[0061] A system may include two power supply devices, one motor, and a power switching device that triggers the switching between the power supply devices. This power switching device may be, for example, a fast-switching device. For instance, one of the two power supply devices is the primary power supply device, and the other is a backup power supply device. If multiple motors are included, they can be connected to the same busbar, and the power supply devices supply power to each motor through the busbar. In the prior art, the states of a motor include: Starting, Running, and Standstill. Under normal circumstances, the primary power supply device supplies power to the motors in the system. If the primary power supply device fails, its power supply will stop, and the fast-switching device will activate the backup power supply device to power the motors. The fast-switching device calculates and switches on the backup power supply at the most appropriate time, thus reducing the inrush current when the backup power supply is switched on and minimizing damage to the motor. Without a built-in fast-switching device for power supply switching, the starting current of a motor is typically 5-7 times its normal operating current. Therefore, the threshold indicating motor starting is set to 6-7 times the normal operating current. This means that if the protection relay detects that the motor's current is 5-7 times the normal operating current, it will activate or disable certain protection mechanisms to provide appropriate protection for the starting or normally operating motor. However, the starting current of a motor restarted due to a power supply switch triggered by a fast-switching device is 2-3 times the normal current. Thus, the existing threshold cannot detect the motor starting status, preventing some protection mechanisms from being activated or disabled. Changing the threshold to detect motor starting would require user-defined settings, which not only provides a less-than-ideal user experience but also risks damaging the device due to improper user settings.

[0062] Therefore, the inventors adopted the motor status monitoring method and apparatus for a system according to the following embodiments to accurately identify the status of a motor in a system with a power switching device.

[0063] Example 1

[0064] This embodiment provides a method for monitoring the status of a motor in a system. The system includes a power switching device, which can be a fast-switching device or an automatic transfer switch (ATS), depending on actual needs. The execution entity in this embodiment is the motor status monitoring device, which can be set up independently or integrated into a relay protection device. As described above, the operation of the fast-switching device will have a certain impact on the technology used to protect the motor.

[0065] like Figure 1 As shown, this is a method for monitoring the status of a motor in a system according to this embodiment. The method includes:

[0066] Step 101: Monitor the status information of the motor.

[0067] In this embodiment, monitoring the motor's status information can be achieved by monitoring various parameters related to the motor's operation. This status information can include information related to the motor's energization status, operating status, current status, voltage status, frequency status, etc. The specific status information to be monitored can be set according to actual needs, and will not be elaborated further here.

[0068] The monitoring here can be continuous so that the status of the motor can be determined in real time.

[0069] Step 102: Determine whether the motor's state has changed from running to gradually slowing down based on the motor's state information. If the determination result is yes, then proceed to step 103.

[0070] The motor status monitoring device used in the system can obtain monitoring status information from other devices (such as sensors, backup power supplies, etc.) through wired or wireless connections. Based on this information, it determines the motor's operating status, such as whether power is off, voltage changes, current changes, speed changes, and frequency changes. Here, the motor frequency can be the frequency of the stator voltage or the frequency of the stator current. The motor speed refers to the rotor speed.

[0071] Gradual slowing means that after the power is cut off, the rotor of the running motor continues to rotate under the action of inertia, but the speed gradually decreases, but it does not stop completely. In other words, gradual slowing is between running and stopping.

[0072] As an example, determining whether a motor has changed from starting to running can be based on the motor's real-time current. For instance, if the motor is a three-phase motor, the change from starting to running can be determined if the largest current in each phase is less than a preset factor multiplied by the motor's rated current. The current in each phase can be obtained through sensors. Other criteria can also be added, such as a decreasing current trend, to further confirm the change and provide a more accurate result. For multi-phase motors, the calculation of the current is an existing technology. For example, in a three-phase motor, the average current of each phase can be used. Alternatively, the current can refer to the current of a single phase, depending on the specific requirements.

[0073] As an example, determining whether a motor's state changes from running to gradually slowing down can be based on the motor's frequency or rotational speed. For instance, it can be determined whether the motor's frequency satisfies the following condition: the rate of change of f ≤ a first preset threshold; where f is the motor's frequency. The rate of change of f can also be represented by df / dt, where t is the sampling time of the motor's frequency. If the result is yes, it indicates that the motor's state has changed from running to gradually slowing down. More specifically, the motor's frequency can be continuously sampled, and a corresponding curve and its slope can be determined based on the values ​​of the sampling points and the sampling time. For example, a coordinate system can be established, with the sampling time on the horizontal axis and the motor's frequency on the vertical axis. After multiple samplings, a curve can be formed, and the slope of each sampling point on this curve is df / dt. If there is a slope less than or equal to the first preset threshold, it indicates that the motor's state has changed from gradually slowing down. Of course, you can also directly observe whether the motor frequency decreases within a preset time period, such as whether it decreases by 2%-5% within 20ms. If so, it indicates that the motor's state has changed from running to gradually slowing down. As an example, if the system frequency is 50Hz and it decreases by 1-2Hz within 20ms, it means the motor's state has changed from running to gradually slowing down. Whether it has stopped requires further observation to determine. Alternatively, you can directly observe the frequency difference between the motor and the power grid supplying it. There are many other specific methods for judgment, which will not be elaborated here.

[0074] Step 103: Monitor whether the motor status changes from slowing down to starting. If the monitoring result is positive, proceed to step 104.

[0075] If it is determined that the motor's state changes from running to gradually slowing down, it is necessary to monitor whether the motor is re-energized and restarted. As an example, determining whether the motor's state changes from gradually slowing down to starting can be based on the motor's frequency or speed. For example, the motor's frequency or speed can be continuously monitored, and if a gradual increase in the motor's frequency or speed is detected, it is determined that the motor is being restarted.

[0076] Specifically, it can be determined whether the frequency of the motor meets the following conditions:

[0077] f(n)–f(n-2)>0 and f(n-1)-f(n-2)>0, where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor;

[0078] If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

[0079] As an example, it can also be determined whether the frequency of the motor rises within a certain period of time, such as rising by 1-2 Hz within tens of milliseconds.

[0080] Step 104: Trigger at least one protection mechanism of the motor corresponding to the state after the motor is started.

[0081] Upon correctly identifying a motor restart, the corresponding protection mechanism for the motor is triggered to correspond to the correct motor state. As an example, disabled overload protection should be deactivated. It's important to note that deactivating this protection does not equate to enabling it; rather, it removes a reason for disabling it. Whether the protection mechanism will be enabled remains undecided. If, based on other reasons, it is determined that the protection mechanism still needs to be disabled, it can still be disabled, only the reason for disabling it will no longer be "motor state is started." As another example, overload protection that prevents restart can be disabled because the current state has already changed to started.

[0082] According to this embodiment, after the fast-switching device switches the power supply equipment, it can accurately identify whether the motor has restarted, and thus correspond to the correct protection mechanism, avoiding inadequate protection and improving the reliability of motor protection.

[0083] Example 2

[0084] This embodiment further supplements the description of the motor status monitoring method for the system in Embodiment 1.

[0085] like Figure 2A The diagram shown illustrates an application scenario of this embodiment. The system includes two power supply devices P1 and P2, and a motor M. Figure 2A Only one motor M is shown. One power supply device currently providing power is designated as the main power supply device, and the other as a backup power supply device. The main power supply device P1 is connected to bus BB via an incoming line, and the backup power supply device P2 is also connected to bus BB via an incoming line. The incoming line includes three phases: A, B, and C, which are connected to the corresponding three phases of bus BB. Each motor M is connected to bus BB via an outgoing line. The motor status monitoring device 202 for the system can be connected to the outgoing line of each motor M. That is, the incoming line, bus, and outgoing line of phase A are connected together, and similarly, the incoming lines, bus, and outgoing lines of phases B and C are also connected together. The incoming line of the main power supply device P1 has a switch CB1, which can be used to disconnect the connection between the main power supply device P1 and bus BB. The incoming line of the backup power supply device P2 has a switch CB2, which can be used to disconnect the connection between the backup power supply device P2 and bus BB.

[0086] When a system failure occurs, the relay protection device (not shown in the figure) will activate, disconnecting the currently supplying main power supply device P1. The fast-switching device 201 will then quickly switch bus BB to the backup power supply device P2. This process takes only a very short time.

[0087] Figure 2B This is a schematic diagram of a motor state transition mechanism according to this embodiment. The state transition mechanism includes four states of the motor: starting 21, running 22, slowing down 23, and stopping 24.

[0088] In this context, "Start 21" indicates that the motor is powered while in the "Stop 24" state. "Running 22" indicates that the motor is in a normal power supply state after starting. "Slowing down 23" indicates that the motor has been de-energized but has not yet been connected to a new power supply, and the motor rotor is still rotating, which is a state approaching a stop. "Stop 24" indicates that the motor has not been connected to a new power supply and the motor rotor has completely stopped rotating.

[0089] The following example illustrates the state of an electric motor. This example uses a three-phase motor, and the values ​​involved are for illustrative purposes only.

[0090] 1. From Stop 24 to Start 21.

[0091] When the current state of the motor is stopped (24) and the maximum current of all three phases of the motor is greater than a first preset threshold, the state of the motor is switched to start (21).

[0092] 2. From startup 21 to running 22.

[0093] For example, the following formula can be used to determine whether the motor's state has changed from starting to running:

[0094] Imax < Factor × Irat and I shows a decreasing trend;

[0095] Where Imax represents the maximum current of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor. More specifically, the largest of the three phases of the motor is taken as the maximum current of the motor.

[0096] As an example, if the current state of the motor is "Start 21", the maximum current of all three phases of the motor is less than 1.2 times the rated current of the motor and the current of the motor is decreasing, then the state of the motor is switched to "Run 22".

[0097] 3. From start 21 to stop 24.

[0098] When the motor's current state is "Start" (21) and all three phases of the motor are open circuits, the motor's state is switched to "Stop" (24). The fact that all three phases are open circuits can be determined by the current values ​​in the three phases.

[0099] 4. From running 22 to stopping 24.

[0100] When the current state of the motor is running (22) and all three phases of the motor are open circuits, the state of the motor is switched to stopped (24).

[0101] 5. From running at 22 to gradually slowing down at 23.

[0102] When the current state of the motor is running (22), and the motor frequency meets the following condition: f shows a decreasing trend and the rate of change of f is ≤ the first preset threshold, then the motor state is switched to slowing down (23). Here, f is the motor frequency value.

[0103] 6. From gradually slowing down 23 to stopping 24.

[0104] When the current state of the motor is slowing down (23) and all three phases of the motor are open circuits, the state of the motor is switched to stop (24).

[0105] 7. From slowing down 23 to starting up 21.

[0106] When the current state of the motor is slowing down 23, if it is detected that the frequency of the motor is gradually increasing, the state of the motor is switched to start 21.

[0107] The above describes how to monitor the motor from one state to another. This application monitors whether the motor state changes from slowing down to starting immediately after the motor is detected to change from running to slowing down. This is done by monitoring the motor frequency. By monitoring the change in motor frequency, it is possible to identify whether the motor has restarted in a timely manner and trigger at least one protection mechanism of the motor corresponding to the state after the motor starts, thereby providing reliable protection for the motor.

[0108] Example 3

[0109] This embodiment provides a motor status monitoring device for a system, used to execute the motor status monitoring method for a system described in the previous embodiment. The system includes a power switching device, which can be a fast-switching device, or alternatively, an automatic transfer switch. The specific device can be configured according to actual needs, and will not be elaborated further here.

[0110] like Figure 3AThe diagram shows a motor status monitoring device for a system according to an embodiment of the present invention. The device includes a first monitoring unit 301, a first determining unit 302, a second monitoring unit 303, and a triggering unit 304.

[0111] The first monitoring unit 301 is used to monitor the status information of the motor; the first determining unit 302 is used to determine whether the status of the motor changes from running to slowing down based on the status information of the motor, and if the determination result is yes, a second monitoring unit 303 is triggered; the second monitoring unit 303 is used to monitor whether the status of the motor changes from slowing down to starting, and if the status of the motor changes from slowing down to starting is detected, a triggering unit 304 is triggered; the triggering unit 304 is used to trigger at least one protection mechanism of the motor corresponding to the state after the motor starts.

[0112] Optionally, the second determining unit is specifically used for:

[0113] Monitor the frequency or speed of the motor;

[0114] If the frequency or speed of the motor is detected to be gradually increasing, then the state of the motor is determined to be changing from slowing down to starting.

[0115] Optionally, the second determining unit, when identifying whether the frequency of the motor is gradually increasing, is specifically used for:

[0116] Determine if the frequency of the motor meets the following conditions:

[0117] f(n)–f(n-2)>0 and f(n-1)-f(n-2)>0,

[0118] Where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor;

[0119] If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

[0120] Optionally, the first determining unit 302 is specifically used for:

[0121] Determine if the frequency of the motor meets the following conditions:

[0122] f shows a decreasing trend and the rate of change of f is less than or equal to the first preset threshold, where f is the frequency of the motor.

[0123] Optionally, such as Figure 3B As shown, the device further includes a second determining unit 305, which is used for:

[0124] Determine if the motor's state meets the following conditions:

[0125] Imax < Factor × Irat and I shows a decreasing trend;

[0126] Where Imax represents the largest current in each phase of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor.

[0127] If the judgment result is yes, then the motor's state changes from starting to running.

[0128] Optionally, the power switching device is a fast switching device, or the frequency is the current frequency or voltage frequency of the motor stator.

[0129] The working method of each unit in this embodiment is the same as that in the previous embodiment, and will not be repeated here.

[0130] According to this embodiment, after the fast-switching device switches the power supply equipment, it can accurately identify whether the motor has restarted, and thus correspond to the correct protection mechanism, avoiding inadequate protection and improving the reliability of motor protection.

[0131] The present invention also provides a status monitoring device for a motor of a fast-switching device. The system includes two power supply devices capable of supplying power to the motor and a power switching device, the power switching device being capable of triggering a switch between the two power supply devices. The monitoring device includes at least one memory and at least one processor, wherein the memory is used to store instructions; the processor is used to execute the status monitoring method for a motor of a fast-switching device as described in any of the foregoing embodiments according to the instructions stored in the memory.

[0132] Embodiments of the present invention also provide a readable storage medium. This readable storage medium stores machine-readable instructions, which, when executed by a machine, enable the machine to perform the motor status monitoring method for the fast-switching device described in any of the foregoing embodiments.

[0133] The readable medium stores machine-readable instructions that, when executed by a processor, cause the processor to perform any of the aforementioned methods. Specifically, a system or apparatus equipped with a readable storage medium storing software program code that implements the functions of any of the embodiments described above, and causing the computer or processor of the system or apparatus to read and execute the machine-readable instructions stored in the readable storage medium.

[0134] In this case, the program code itself, which can be read from a readable medium, can perform the functions of any of the above embodiments. Therefore, the machine-readable code and the readable storage medium storing the machine-readable code constitute a part of the present invention.

[0135] Examples of readable storage media include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer or the cloud via a communication network.

[0136] Those skilled in the art will understand that the various embodiments disclosed above can be modified and varied without departing from the spirit of the invention. Therefore, the scope of protection of this invention should be defined by the appended claims.

[0137] It should be noted that not all steps and units in the above process and system structure diagrams are mandatory; some steps or units can be omitted as needed. The execution order of each step is not fixed and can be adjusted as required. The device structure described in the above embodiments can be a physical structure or a logical structure; that is, some units may be implemented by the same physical entity, or some units may be implemented by multiple physical entities, or they may be jointly implemented by certain components in multiple independent devices.

[0138] In the above embodiments, the hardware units can be implemented mechanically or electrically. For example, a hardware unit or processor may include permanent dedicated circuitry or logic (such as a dedicated processor, FPGA, or ASIC) to perform the corresponding operations. The hardware unit or processor may also include programmable logic or circuitry (such as a general-purpose processor or other programmable processor), which can be temporarily configured by software to perform the corresponding operations. The specific implementation method (mechanical, dedicated permanent circuitry, or temporarily configured circuitry) can be determined based on cost and time considerations.

[0139] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring the status of a motor in a system, the system comprising two power supply devices capable of supplying power to the motor and a power switching device, the power switching device being capable of triggering a switch between the two power supply devices, the method comprising: Monitor the status information of the motor; The method is characterized in that the power switching device is a fast-switching device, and the method further includes: Determine whether the motor's state changes from running to gradually slowing down based on the motor's state information; If the result is confirmed to be yes, then monitor whether the state of the motor changes from slowing down to starting. If the state of the motor changes from slowing down to starting, at least one protection mechanism of the motor is triggered corresponding to the state after the motor starts. Monitor whether the motor's state changes from gradually slowing down to starting: Monitor the frequency or speed of the motor; If it is detected that the frequency or speed of the motor is gradually increasing, then it is determined that the state of the motor changes from slowing down to starting.

2. The method according to claim 1, characterized in that, Identifying whether the frequency of the motor gradually increases includes: Determine whether the frequency of the motor meets the following conditions: f(n)–f(n-2) > 0 and f(n-1) - f(n-2) > 0, Where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor; If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

3. The method according to claim 1, characterized in that, Determining whether the state of the motor changes from running to slowing down based on the motor's state information includes: Determine whether the frequency of the motor meets the following conditions: f shows a decreasing trend and the rate of change of f is ≤ a first preset threshold, where f is the frequency of the motor; If the result is yes, the state of the motor changes from running to gradually slowing down.

4. The method according to claim 1, characterized in that, Also includes: Determine whether the state of the motor meets the following conditions: Imax < Factor × Irat and I shows a decreasing trend; Where Imax represents the largest current among all phases of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor. If the judgment result is yes, then the motor's state changes from starting to running.

5. The method according to any one of claims 1-4, characterized in that, The frequency is the current frequency of the motor stator or the voltage frequency of the motor stator.

6. A status monitoring device for a system's electric motor, the system comprising two power supply devices capable of supplying power to the electric motor and a power switching device, the power switching device capable of triggering a switch between the two power supply devices, the device comprising: A first monitoring unit is used to monitor the status information of the motor; The power switching device is characterized in that it is a fast-switching device, and the device further includes: A first determining unit is used to determine whether the state of the motor changes from running to slowing down based on the state information of the motor. If the determination result is yes, a second monitoring unit is triggered. The second monitoring unit is used to monitor whether the state of the motor changes from slowing down to starting. If the state of the motor changes from slowing down to starting, a triggering unit is triggered. The triggering unit is used to trigger at least one protection mechanism of the motor corresponding to the state after the motor starts; The second monitoring unit is specifically used for: Monitor the frequency or speed of the motor; If it is detected that the frequency or speed of the motor is gradually increasing, then it is determined that the state of the motor changes from slowing down to starting.

7. The apparatus according to claim 6, characterized in that, The second monitoring unit, when identifying whether the frequency of the motor is gradually increasing, is specifically used for: Determine whether the frequency of the motor meets the following conditions: f(n)–f(n-2) > 0 and f(n-1) - f(n-2) > 0, Where f(n) is the nth frequency sampling point of the motor, f(n-1) is the (n-1)th frequency sampling point of the motor, and f(n-2) is the (n-2)th frequency sampling point of the motor; If the judgment result is yes, then the frequency of the motor is identified as gradually increasing.

8. The apparatus according to claim 6, characterized in that, The first determining unit is specifically used for: Determine whether the frequency of the motor meets the following conditions: f shows a decreasing trend and the rate of change of f is ≤ a first preset threshold, where f is the frequency of the motor; If the result is yes, the state of the motor changes from running to gradually slowing down.

9. The apparatus according to claim 6, characterized in that, It also includes a second determining unit, which is used to: Determine whether the state of the motor meets the following conditions: Imax < Factor × Irat and I shows a decreasing trend; Where Imax represents the largest current among all phases of the motor, Factor represents the preset factor, Irat represents the rated current of the motor, and I represents the current of the motor. If the judgment result is yes, then the motor's state changes from starting to running.

10. The apparatus according to any one of claims 6-9, characterized in that... The frequency is the current frequency of the motor stator or the voltage frequency of the motor stator.

11. A status monitoring device for a motor used in a fast-cutting device, characterized in that, The system includes two power supply devices capable of supplying power to the motor and a power switching device, the power switching device being capable of triggering a switch between the two power supply devices, and the status monitoring device including: At least one memory for storing instructions; At least one processor is configured to execute, according to instructions stored in the memory, the method for monitoring the state of an electric motor for a system as described in any one of claims 1-5.

12. A readable storage medium, characterized in that, The readable storage medium stores machine-readable instructions, which, when executed by a machine, enable the machine to perform a method for monitoring the state of a motor for a system according to any one of claims 1-5.

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