Contact wear monitoring device

Abstract

The present invention provides a contact wear monitoring device (1) for monitoring wear of a contact that opens or closes an electrical circuit, the device comprising a computation unit (11) that accepts input of current information indicating a current flowing through the electrical circuit. The computation unit (11) calculates a cumulative contact wear amount, which is the cumulative amount of wear of the contact, on the basis of the current information and arc characteristics data indicating the relationship between a reference arc energy and a cumulative arc energy. The reference arc energy is the arc energy under the condition of a reference arc current, which is an arc current of a preset reference magnitude, and the cumulative arc energy is the cumulative value of opening / closing arc energy, which is the arc energy under the condition of an opening / closing arc current when the contact opens and closes.

Description

Contact wear monitoring device

[0001] The present disclosure relates to a contact wear monitoring device that monitors the wear of contacts of a switch.

[0002] A switch installed in an electric circuit connecting a load such as a motor to a power source has a fixed contact (a stationary contactor) and a movable contact (a movable contactor). The fixed contactor is fixed in a predetermined position, and the movable contactor is installed so that it can move between a closing position where it is in contact with the fixed contactor and a breaking position where it is not in contact with the fixed contactor. When the movable contactor comes into contact with the fixed contactor, current flows from the power source to the load, and when the movable contactor is not in contact with the fixed contactor, the current flowing from the power source to the load is interrupted. Hereinafter, the fixed contacts and the movable contacts are collectively referred to as "contacts." Furthermore, bringing the movable contactor into contact with the fixed contactor is referred to as "closing the contact," and bringing the movable contactor out of contact with the fixed contactor is referred to as "opening the contact."

[0003] When a switch opens or closes the contacts, an arc occurs between the fixed contact and the moving contact, and the heat from the arc discharge melts and vaporizes the fixed and moving contacts. Hereinafter, the melting and vaporization of the fixed and moving contacts due to the heat from the arc discharge is referred to as "contact wear." As the number of switch opening and closing operations increases, the amount of contact wear increases. As the cumulative contact wear increases, poor contact between the fixed and moving contacts can lead to a discontinuity, or the fixed and moving contacts can weld together, causing a switch malfunction. For this reason, users must monitor the cumulative contact wear and take measures such as stopping use of the switch and replacing the contacts before they become worn enough to cause a malfunction.

[0004] Patent Document 1 discloses a contact wear monitoring device that calculates the arc time from the measurement results of the arc current and arc voltage, calculates the arc energy from the information on the arc current and arc time, and estimates the cumulative amount of contact wear by integrating the arc energy.

[0005] U.S. Pat. No. 10,332,698

[0006] However, the contact wear monitoring device disclosed in Patent Document 1 needs to measure not only the arc current but also the arc voltage in order to calculate the arc energy. In other words, the contact wear monitoring device disclosed in Patent Document 1 needs a voltmeter in addition to an ammeter, which poses the problem of requiring many components to estimate the cumulative contact wear amount.

[0007] The present disclosure has been made in view of the above, and has an object to provide a contact wear monitoring device that can estimate the accumulated amount of contact wear using a small number of components.

[0008] In order to solve the above-mentioned problems and achieve the object, a contact wear monitoring device according to the present disclosure is a contact wear monitoring device that monitors wear of contacts that open and close an electric circuit, and includes a calculation unit to which current information indicating a current flowing in the electric circuit is input. The calculation unit calculates a cumulative contact wear amount, which is the cumulative amount of wear of the contacts, based on arc characteristic data and the current information indicating the relationship between reference arc energy, which is the arc energy under conditions of a reference arc current that is an arc current of a predetermined reference magnitude, and cumulative arc energy, which is the cumulative value of opening and closing arc energy, which is the arc energy under conditions of an opening and closing arc current that flows when the contacts are opened and closed.

[0009] The contact wear monitoring device according to the present disclosure has the advantage of being able to estimate the cumulative amount of contact wear using a small number of components.

[0010] FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 1. FIG. 1 shows the configuration of a contact wear monitoring device according to embodiment 1. FIG. 1 shows an example of the relationship between reference arc energy and cumulative arc energy of a contact wear monitoring device according to embodiment 1. FIG. 1 shows an example of a process of multiplying a correction value by reference arc energy of a contact wear monitoring device according to embodiment 1. Flowchart showing the operation flow of a contact wear monitoring device according to embodiment 1. FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 2. FIG. 1 shows the configuration of a contact wear monitoring device according to embodiment 2. FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 3. FIG. 1 shows the configuration of a contact wear monitoring device according to embodiment 3. FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 4. FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 5. FIG. 1 shows the configuration of a power transmission system using a contact wear monitoring device according to embodiment 6. FIG. 1 shows the configuration of a contact wear monitoring device according to embodiment 6. FIG. 1 shows the hardware configuration of a calculation unit of a contact wear monitoring device according to embodiments 1 to 6.

[0011] A contact wear monitoring device according to an embodiment will be described in detail below with reference to the drawings.

[0012] Embodiment 1. Figure 1 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to embodiment 1. The power transmission system 100 according to embodiment 1 is a system that supplies power from a power source 4 to a load 2 that consumes power. The power transmission system 100 includes a switch 5 and a current sensor 6 installed on an electric circuit 3 between the power source 4 and the load 2, and a contact wear monitoring device 1 connected to the current sensor 6. The electric circuit 3 includes first phase wiring 3a, second phase wiring 3b, and third phase wiring 3c. The switch 5 and the current sensor 6 are connected in series on the electric circuit 3. The current sensor 6 measures the current flowing through the electric circuit 3 to obtain current information. The current information is information indicating the current flowing through the electric circuit 3, such as information about a current waveform. The current waveform is represented by a sequence of points representing the current values ​​of the current flowing through the electric circuit 3 at regular intervals.

[0013] The switch 5 has contacts 51. The contacts 51 include fixed contacts 7a, 7b, and 7c, which are fixed contacts 7, and movable contacts 8a, 8b, and 8c, which are movable contacts 8. The fixed contact 7a is installed on the first phase wiring 3a on the power source 4 side. The fixed contact 7b is installed on the second phase wiring 3b on the power source 4 side. The fixed contact 7c is installed on the third phase wiring 3c on the power source 4 side. The movable contact 8a is installed on the first phase wiring 3a on the load 2 side. The movable contact 8b is installed on the second phase wiring 3b on the load 2 side. The movable contact 8c is installed on the third phase wiring 3c on the load 2 side.

[0014] Here, an event in which the movable contacts 8a, 8b, and 8c move from a closing position where they are in contact with the fixed contacts 7a, 7b, and 7c to a breaking position where they are not in contact with the fixed contacts 7a, 7b, and 7c is called an opening event. Also, an event in which the movable contacts 8a, 8b, and 8c move from a breaking position where they are not in contact with the fixed contacts 7a, 7b, and 7c to a closing position where they are in contact with the fixed contacts 7a, 7b, and 7c is called a closing event. Also, opening events and closing events are collectively called switching events. The switch 5 opens and closes the electric circuit 3 by switching events.

[0015] 2 is a diagram showing the configuration of the contact wear monitoring device according to embodiment 1. The contact wear monitoring device 1 includes a calculation unit 11, a storage unit 12, and a display unit 13.

[0016] The calculation unit 11 includes a current measurement unit 111 , a switching event determination unit 112 , an arc characteristics determination unit 113 , and a contact erosion calculation unit 114 .

[0017] The current measurement unit 111 passes the current information input from the current sensor 6 to the switching event determination unit 112 and the contact wear calculation unit 114 .

[0018] The switching event determination unit 112 detects the occurrence of a switching event. For example, the switching event determination unit 112 detects the occurrence of a closing event by detecting a rise in current based on the current information. The switching event determination unit 112 also detects the occurrence of a disconnection event by detecting the cessation of current flow based on the current information. Note that the switching event determination unit 112 may more accurately detect the occurrence of a switching event by using an operation signal from the switch 5, for example.

[0019] The arc characteristic determination unit 113 calculates the reference arc energy at the time when the contacts 51 are opened and closed based on the arc characteristic data indicating the relationship between the reference arc energy and the accumulated arc energy, and passes the calculated value to the contact erosion calculation unit 114. The reference arc energy is the arc energy under the condition of a reference arc current, which is an arc current of a reference magnitude. The accumulated arc energy is the accumulated value of the opening and closing arc energy, which is the arc energy under the condition of the opening and closing arc current that flows when the contacts 51 are opened and closed. The reference arc energy has a relationship in which the reference arc energy increases as the accumulated arc energy increases. In other words, even if the same magnitude of arc current flows, if the accumulated arc energy at that time is large, the arc energy generated by that arc current will be large.

[0020] The initial value of the accumulated arc energy is 0. The arc characteristic data is recorded in the storage unit 12 in advance.

[0021] 3 is a diagram showing an example of the relationship between reference arc energy and cumulative arc energy in the contact wear monitoring device according to embodiment 1. The relationship between reference arc energy and cumulative arc energy is represented by a sequence of points, which is a set of points obtained by basic testing or analysis. The sequence of points showing the relationship between reference arc energy and cumulative arc energy, or an approximation formula created based on the sequence of points, is stored in advance in storage unit 12 as arc characteristic data.

[0022] The dotted line in Fig. 3 indicates an approximation formula created based on a sequence of points showing the relationship between the reference arc energy and the accumulated arc energy. The approximation formula showing the relationship between the reference arc energy and the accumulated arc energy is expressed by an equation using the accumulated arc energy as a variable and a constant specific to the contact 51. For example, when the reference arc energy W ａｒｃｂ An approximate expression representing the relationship between the accumulated arc energy Q and the contact 51 is expressed by the following expression (1) using constants a, b, c, and d specific to the contact 51.

[0023] W ａｒｃｂ = aQ ３ +bQ ２+cQ+d...(1)

[0024] After calculating the reference arc energy, the arc characteristics determining unit 113 passes the reference arc energy to the contact erosion calculating unit 114 .

[0025] The contact erosion calculation unit 114 calculates the cumulative arc energy and the amount of contact erosion based on the reference arc energy passed from the arc characteristic determination unit 113 and the current information passed from the current measurement unit 111 .

[0026] In calculating the cumulative arc energy, the contact erosion calculation unit 114 first calculates the arc current I that flows when the contact 51 is opened and closed. ａｒｃ The arc energy W ａｒｃ As shown in the following formula (2), the arc current I generated by opening and closing the contact 51 is calculated. ａｒｃ The arc energy W ａｒｃ is the reference arc energy W ａｒｃｂ The correction value is calculated by multiplying the arc current I ａｒｃ is the reference arc current I ｓｔｄ The value obtained by dividing the value by the multiplier n specific to the contact 51 is raised to the power of n (I ａｒｃ / I ｓｔｄ ) ｎ is.

[0027] W ａｒｃ =W ａｒｃｂ × (I ａｒｃ / I ｓｔｄ ) ｎ ...(2)

[0028] 4 is a diagram showing an example of a process of multiplying the reference arc energy by a correction value in the contact wear monitoring device according to the first embodiment. The contact wear calculation unit 114 calculates the reference arc current I by multiplying the current value obtained from the current information by the reference arc current I. ｓｔｄ If the reference arc energy is greater than 1, the reference arc energy is multiplied by a correction value greater than 1 to calculate the opening and closing arc energy, and the current value obtained from the current value is the reference arc current I ｓｔｄ If it is smaller than 1, the reference arc energy is multiplied by a correction value smaller than 1 to calculate the opening and closing arc energy.

[0029] The contact erosion calculation unit 114 outputs the updated cumulative arc energy obtained by integrating the calculated opening and closing arc energy to the storage unit 12, thereby updating the cumulative arc energy stored in the storage unit 12. The contact erosion calculation unit 114 also calculates the amount of cumulative contact erosion by multiplying the updated cumulative arc energy by a preset coefficient. The coefficient by which the cumulative arc energy is multiplied is a constant specific to the contact 51.

[0030] The display unit 13 displays information on the accumulated contact erosion amount calculated by the contact erosion calculation unit 114. The storage unit 12 stores information on the accumulated arc energy calculated by the contact erosion calculation unit 114.

[0031] FIG. 5 is a flowchart showing the flow of operation of the contact wear monitoring device according to the first embodiment.

[0032] In step S1 , the current measurement unit 111 acquires current information from the current sensor 6 .

[0033] In step S2, the open / close event determination unit 112 determines whether an open / close event has occurred. If the open / close event determination unit 112 determines that an open / close event has occurred, the answer is Yes in step S2, and the process proceeds to step S3. If the open / close event determination unit 112 does not determine that an open / close event has occurred, the answer is No in step S2, and the process returns to step S1.

[0034] In step S3, the arc characteristic determining unit 113 calculates the reference arc energy at the time when the contact 51 opens and closes based on the arc characteristic data.

[0035] In step S4, the contact erosion calculation unit 114 calculates the reference arc energy W ａｒｃｂ The switching arc energy is calculated by multiplying the value by the correction value.

[0036] In step S5, the contact wear calculation unit 114 calculates and updates the cumulative arc energy by adding the opening and closing arc energy to the cumulative energy stored in the storage unit 12.

[0037] In step S6, the contact erosion calculation unit 114 calculates the amount of accumulated contact erosion by multiplying the updated accumulated arc energy by a preset coefficient.

[0038] In step S7, the display unit 13 displays the accumulated amount of wear of the contacts.

[0039] By checking the cumulative contact wear amount displayed on the display unit 13, the user of the contact wear monitoring device 1 can take measures such as stopping use of the switch 5 and replacing the contacts 51 before they wear out to the point where they could cause malfunction.

[0040] The contact wear monitoring device 1 according to the first embodiment stores the relationship between the reference arc energy and the accumulated arc energy in the storage unit 12, and therefore can calculate the opening and closing arc energy from the accumulated arc energy and current information. Therefore, the contact wear monitoring device 1 according to the first embodiment does not require a voltmeter for measuring the arc voltage when estimating the accumulated contact wear amount, and can estimate the accumulated contact wear amount with a small number of components.

[0041] Embodiment 2. Fig. 6 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to embodiment 2. The power transmission system according to embodiment 2 differs from the power transmission system 100 according to embodiment 1 in that it includes an external device 20 connected to the contact wear monitoring device 1. The external device 20 is, for example, a device such as an overall monitoring system or a monitoring computer that monitors the entire power transmission system 100.

[0042] 7 is a diagram showing the configuration of a contact wear monitoring device according to embodiment 2. The contact wear monitoring device 1 differs from the contact wear monitoring device 1 according to embodiment 1 in that it includes a communication unit 14.

[0043] The communication unit 14 is an interface for transmitting and receiving data to and from the external device 20. By using the communication unit 14 for communication between the contact wear monitoring device 1 and the external device 20, it is possible to output information on the amount of contact wear stored in the memory unit 12 to the external device 20 and to update the arc characteristic data recorded in the memory unit 12 from the external device 20.

[0044] The contact wear monitoring device 1 according to the second embodiment can remotely monitor the wear of the contacts 51 and change the arc characteristic data from the external device 20 in accordance with the update of the switch 5 .

[0045] Embodiment 3. Fig. 8 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to embodiment 3. The power transmission system 100 according to embodiment 3 differs from the power transmission system 100 according to embodiment 2 in that the contact wear monitoring device 1 detects an overcurrent and outputs a cutoff command to the switch 5.

[0046] 9 is a diagram showing the configuration of a contact wear monitoring device according to embodiment 3. The contact wear monitoring device 1 differs from the contact wear monitoring device 1 according to embodiment 2 in that it includes a trip instruction unit 15. The trip instruction unit 15 detects an overcurrent based on current information and issues a trip command to the switch 5.

[0047] The contact wear monitoring device 1 according to the third embodiment can be added with minimal configuration changes a function of detecting an overcurrent and causing an interruption event to occur in the contacts 51 of the switch 5. The contact wear monitoring device 1 according to the third embodiment prevents an overcurrent from continuing to flow in the circuit 3 without being interrupted, thereby preventing the load 2, switch 5, and current sensor 6 from breaking down due to an overcurrent.

[0048] Embodiment 4. Fig. 10 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to embodiment 4. The power transmission system 100 according to embodiment 4 differs from the power transmission system 100 according to embodiment 3 in that a current sensor 6 is incorporated into the contact wear monitoring device 1.

[0049] The power transmission system 100 according to the fourth embodiment can be configured to have a small overall system size, and can also omit wiring between the current sensor 6 and the contact wear monitoring device 1 .

[0050] 11 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to embodiment 5. The power transmission system 100 according to embodiment 5 differs from the power transmission system 100 according to embodiment 3 in that the current sensor 6 and the contacts 51 are incorporated into the contact wear monitoring device 1.

[0051] The power transmission system 100 according to the fifth embodiment can be configured to further reduce the size of the entire system, and can also omit the wiring between the switch 5 and the contact wear monitoring device 1 .

[0052] Sixth embodiment Fig. 12 is a diagram showing the configuration of a power transmission system using a contact wear monitoring device according to the sixth embodiment. Fig. 13 is a diagram showing the configuration of a contact wear monitoring device according to the sixth embodiment. In the power transmission system 100 according to the sixth embodiment, a memory unit 22 is provided in the external device 20. Furthermore, the contact wear monitoring device 1 according to the sixth embodiment does not include a memory unit 12. In other respects, the power transmission system 100 and the contact wear monitoring device 1 according to the second embodiment are the same as those according to the second embodiment.

[0053] The contact wear monitoring device 1 according to embodiment 6 does not include a storage unit 12, thereby enabling the device to be made smaller. In the above description, a configuration has been described in which the external device 20 includes a storage unit 22, but the storage unit may be provided in a device on the network. In the above description, an example has been given of a contact wear monitoring device 1 that does not include a storage unit 12, but the display unit 13 may be externally attached to the contact wear monitoring device 1. In addition, the contact wear monitoring device 1 may be externally attached to both the storage unit 12 and the display unit 13. In other words, the contact wear monitoring device 1 may be configured such that at least one of the storage unit 12 and the display unit 13 is externally attached.

[0054] The following describes the hardware configuration of the calculation unit 11 of the contact wear monitoring device 1 according to embodiments 1 to 6. Fig. 14 is a diagram showing the hardware configuration of the calculation unit of the contact wear monitoring device according to embodiments 1 to 6. The calculation unit 11 is realized by a computer system including a processor 91 that executes various processes, a memory 92 that is a main memory, and a storage device 93 that stores information.

[0055] The processor 91 may be a computing device such as a calculation device, microprocessor, microcomputer, CPU (Central Processing Unit), or DSP (Digital Signal Processor). The memory 92 may be a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The storage device 93 stores a program for calculating the cumulative contact erosion of the contacts 51 based on current information and information indicating the relationship between the reference arc energy and the cumulative arc energy.

[0056] In the computer system described above, the processor 91 reads into the memory 92 programs stored in the storage device 93 and corresponding to the processing of each component, and executes the programs, thereby realizing the functions of the switching event determination unit 112, the arc characteristics determination unit 113, and the contact erosion calculation unit 114. The memory 92 is also used as a temporary memory for each process executed by the processor 91. The programs executed by the processor 91 may be provided in a state stored in a storage medium, or may be provided via a network.

[0057] The configurations shown in the above embodiments are merely examples of the content, and may be combined with other known technologies, or parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0058] REFERENCE SIGNS LIST 1 Contact wear monitoring device, 2 Load, 3 Electric circuit, 3a First phase wiring, 3b Second phase wiring, 3c Third phase wiring, 4 Power source, 5 Switch, 6 Current sensor, 7 Fixed contact, 7a, 7b, 7c Fixed contact, 8 Moving contact, 8a, 8b, 8c Moving contact, 11 Calculation unit, 12, 22 Memory unit, 13 Display unit, 14 Communication unit, 15 Break instruction unit, 20 External device, 51 Contact, 91 Processor, 92 Memory, 93 Storage device, 100 Power transmission system, 111 Current measurement unit, 112 Switching event determination unit, 113 Arc characteristic determination unit, 114 Contact wear calculation unit.

Claims

1. A contact wear monitoring device that monitors the wear of contacts that open and close electrical circuits, The system includes a calculation unit that receives current information indicating the current flowing through the aforementioned circuit, The contact wear monitoring device is characterized in that the calculation unit calculates the cumulative contact wear amount, which is the cumulative wear amount of the contact, based on arc characteristic data showing the relationship between the reference arc energy, which is the arc energy under the condition of a reference arc current, which is an arc current of a preset standard magnitude, and the cumulative arc energy, which is the cumulative value of the arc energy during switching, which is the arc energy under the condition of the switching arc current that flowed when the contact was opened and closed, and the current information.

2. The aforementioned arithmetic unit, An arc characteristic determination unit that calculates the reference arc energy from the accumulated arc energy at the time of opening and closing of the contact, The contact wear monitoring device according to claim 1, further comprising a contact wear calculation unit that calculates the switching arc energy based on the reference arc energy and the current information, and calculates a new cumulative arc energy by integrating the switching arc energies.

3. The contact wear monitoring device according to claim 2, characterized in that the contact wear calculation unit calculates the cumulative contact wear amount by multiplying the cumulative arc energy by a preset constant.

4. The contact wear monitoring device according to claim 1, characterized by having a storage unit for storing arc characteristic data and the accumulated arc energy.

5. The contact wear monitoring device according to claim 1, characterized in that it has a communication unit for communicating with external devices.

6. The contact wear monitoring device according to claim 1, characterized in that it has a shut-off instruction unit that instructs the opening and closing of the aforementioned contacts.

7. The contact wear monitoring device according to any one of claims 1 to 6, characterized in that it has a current sensor that measures the current flowing through the circuit and acquires the current information.

8. The contact wear monitoring device according to claim 7, characterized in that it has the aforementioned contacts.