Welding detection device and welding detection method

Abstract

A welding detection device comprises a first circuit, a first circuit power supply and a second circuit. The first circuit is connected to a first line connecting the power supply to a main relay and a second line connecting the load to the main relay. The first circuit includes a detection element. The first circuit power supply supplies a DC power supply to the first circuit. The second circuit is connected to the first circuit and detects a voltage difference between the first line and the second line. When the main relay is controlled from a closed state to an open state, the first circuit detects welding of the main relay based on whether the current from the first circuit power supply flows to the detection element via the main relay. When the main relay is controlled from a closed state to an open state, the second circuit cuts off the first circuit only when a voltage difference is generated between the first line and the second line.

Description

Technical Field

[0001] The present invention relates to a welding detection device and a welding detection method. Background Art

[0002] Currently, as a method for detecting whether the contacts of a relay are welded, a method of monitoring the voltage applied to the relay to detect the welding of the relay is generally used. However, in this method, when no voltage is applied, the welding of the relay cannot be accurately detected. Therefore, Patent Document 1 discloses the following welding detection device: when the relay is controlled to be in an off state, the welding of the relay is detected by detecting whether there is a current flowing through the relay through a detection element.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-173428 Summary of the invention

[0006] Problems to be solved by the invention

[0007] For example, when the welding detection device is used as a switching device for switching the power source connected to the load from a single-phase three-wire AC power source to another AC power source, there is a concern that the welding detection device may erroneously detect welding. Figure 4 As shown, when the welding detection device 90 is used to detect the welding of the relay 91 that switches the load and the power supply, if an AC voltage of 100V between the neutral line N and the power line L1 is applied to the relay 91, an AC current flows from the line 92 that connects the load and the power supply to the welding detection device 90 without passing through the relay 91. This current flows to the detection element, and there is a concern that the welding detection device 90 may mistakenly detect the welding of the relay 91.

[0008] An object of the present invention is to prevent erroneous detection of welding in a welding detection device that detects welding of a relay based on the presence or absence of current flowing through a detection element.

[0009] Solutions to Solve Problems

[0010] A welding detection device of one embodiment of the present invention detects the welding of a main relay that opens and closes the connection between a load and a power supply that supplies AC power to the load. The welding detection device includes a first circuit, a first circuit power supply, and a second circuit. The first circuit is connected to a first line that connects the power supply to the main relay, and a second line that connects the load to the main relay. The first circuit includes a detection element. The first circuit power supply supplies a DC power supply to the first circuit. The second circuit is connected to the first circuit to detect the voltage difference between the first line and the second line. When the main relay is controlled from a closed state to an open state, the first circuit detects the welding of the main relay based on whether the current from the first circuit power supply flows to the detection element via the main relay. When the main relay is controlled from a closed state to an open state, the second circuit cuts off the first circuit only when a voltage difference is generated between the first line and the second line.

[0011] In the welding detection device, when the main relay is controlled from the closed state to the open state, only when a voltage difference is generated between the first circuit and the second circuit, the first circuit is cut off by the second circuit to disable the detection element of the first circuit. That is, when a voltage is applied to the main relay, it is possible to prevent the AC current of the power supply from flowing from the second circuit to the first circuit without passing through the main relay. Therefore, it is possible to prevent the AC current of the power supply from flowing from the second circuit to the first circuit without passing through the main relay, and the current from flowing to the detection element, so that the welding detection circuit erroneously detects the welding of the main relay.

[0012] The first circuit may further include a first relay that opens and closes a connection with the first line, and a second relay that opens and closes a connection with the second line.

[0013] The welding detection device may also be provided in a switching device that switches the power supply for supplying AC power to the load from one of the first system power supply and the second system power supply to the other. The switching device may also include a main relay. The main relay may also include a first main relay that opens and closes the connection between the first system power supply and the load, and a second main relay that opens and closes the connection between the second system power supply and the load.

[0014] A welding detection method according to one embodiment of the present invention detects the welding of a main relay that opens and closes the connection between a load and a power supply that supplies AC power to the load. A welding detection device includes a first circuit and a first circuit power supply. The first circuit includes a detection element that detects current, and is connected to a first line that connects the power supply to the main relay, and a second line that connects the load to the main relay. The first circuit power supply supplies a DC current to the first circuit. The welding detection method includes the following steps: when the main relay is controlled from a closed state to an open state, a step of detecting the welding of the main relay based on whether the current from the first circuit power supply flows to the detection element via the main relay; and when the main relay is controlled from a closed state to an open state, a step of cutting off the first circuit only when a voltage difference is generated between the first line and the second line.

[0015] According to the present invention, in a welding detection device that detects welding of a relay based on the presence or absence of current flowing through a detection element, erroneous detection of welding can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram schematically showing the structure of a power supply switching device in which a welding detection device is incorporated.

[0017] Figure 2 This is a diagram schematically showing a circuit diagram of a welding detection device.

[0018] Figure 3 It is a timing chart showing the timings at which the main relay, the first relay, and the second relay operate.

[0019] Figure 4 This is a diagram for explaining the problems of the welding detection device. DETAILED DESCRIPTION

[0020] Figure 1 1 is a diagram schematically showing the structure of a power switching device 1 in which a welding detection device 10 according to one embodiment of the present invention is assembled. The power switching device 1 switches the power supply for supplying AC power to a load 2 from one of a first system power supply and a second system power supply to the other. Specifically, when the supply of AC power from an industrial power supply A to the load 2 is cut off due to a power outage or other fault, the power supply for supplying AC power to the load 2 is switched from the industrial power supply A to another industrial power supply or an independent power supply B. The independent power supply B is, for example, a power supply using power generated by a solar power generation system.

[0021] The power switching device 1 in this embodiment switches the power supply for supplying AC power to the load 2 from one of the industrial power supply A and the independent power supply B to the other. The industrial power supply A and the independent power supply B are single-phase three-wire AC power supplies. In the single-phase three-wire system, a voltage of AC100V is applied to the power lines L1 and L2 with the neutral line N as a reference.

[0022] The power supply switching device 1 includes main relays 3a, 3b, main relays 4a, 4b, and a control unit 5. The main relays 3a, 3b, 4a, and 4b are latching relays of a contact. The main relays 3a, 3b, 4a, and 4b open and close the connection between the load 2 and the power supply that supplies AC power to the load 2. The main relays 3a and 3b are examples of first main relays, and the main relays 4a and 4b are examples of second main relays. In addition, the main relays 3a, 3b, 4a, and 4b may also be relays other than latches. For example, it may also be a relay that maintains the open state or the closed state of the contact only during the period when the coil is excited.

[0023] The main relays 3a and 3b open and close the connection between the industrial power supply A and the load 2. The main relay 3a opens and closes the connection between the power line L1 of the industrial power supply A and the load 2. The main relay 3b opens and closes the connection between the power line L2 of the industrial power supply A and the load 2. The main relays 4a and 4b open and close the connection between the independent power supply B and the load 2. The main relay 4a opens and closes the connection between the power line L1 of the independent power supply B and the load 2. The main relay 4b opens and closes the connection between the power line L2 of the independent power supply B and the load 2. In addition, the main relays may be arranged on the neutral line N, and the main relays arranged on the neutral line N may also open and close the connection between the industrial power supply A and the independent power supply B and the load 2.

[0024] The control unit 5 performs opening and closing control on the main relays 3a, 3b, 4a, and 4b. The control unit 5 performs opening and closing control on the main relays 3a and 3b at the same time. The control unit 5 performs opening and closing control on the main relays 4a and 4b at the same time. For example, when AC power is supplied from the industrial power supply A to the load 2, the control unit 5 controls the main relays 3a and 3b to be in a closed state and controls the main relays 4a and 4b to be in an open state. In addition, it is also possible to configure that a main relay is also provided on the neutral line N, and the main relay provided on the neutral line N is controlled to be opened and closed in conjunction with the main relays 3a, 3b, 4a, and 4b.

[0025] When the power source connected to the load 2 is switched from the industrial power source A to the independent power source B, the control unit 5 controls the main relays 3a and 3b from the closed state to the open state, and controls the main relays 4a and 4b from the open state to the closed state. On the contrary, when the power source connected to the load 2 is switched from the independent power source B to the industrial power source A, the control unit 5 controls the main relays 3a and 3b from the closed state to the open state, and controls the main relays 4a and 4b from the open state to the closed state. For example, when the control unit 5 detects that the supply of AC power from the industrial power source A to the load 2 is cut off, the main relays 3a and 3b are controlled from the closed state to the open state, and the main relays 4a and 4b are controlled from the open state to the closed state.

[0026] When the power switching device 1 switches the power connected to the load 2, the welding detection device 10 detects the welding of the main relays 3a, 3b, 4a, and 4b. For example, when the power connected to the load 2 is switched from the industrial power supply A to the independent power supply B, the main relays 3a and 3b are changed from the closed state to the open state, and the welding of the main relays 3a and 3b is detected. Then, if the welding of the main relays 3a and 3b is not detected, the control unit 5 controls the main relays 4a and 4b from the open state to the closed state. In the present embodiment, it is configured so that the welding of all the main relays 3a, 3b, 4a, and 4b can be detected by one welding detection device 10. In addition, it can also be configured so that the welding detection device 10 is separately set on the main relays 3a, 3b, 4a, and 4b, and the welding of the main relays 3a, 3b, 4a, and 4b is detected separately.

[0027] Figure 2 1 is a diagram schematically showing a circuit diagram of the welding detection device 10. The welding detection device 10 includes a first circuit 12, a first circuit power supply 14, and a second circuit 16. The first circuit 12 is connected to a first line 21 connecting a power line L1 of an industrial power supply A to a main relay 3a, and a second line 22 connecting a load 2 to the main relay 3a.

[0028] The first circuit 12 includes a third line 23 connected to the first line 21 and a fourth line 24 connected to the second line 22. The third line 23 and the fourth line 24 are connected to the first circuit power supply 14. Current limiting resistors R1 and R2 are provided in the third line 23. In addition, a diode D1 for protecting the circuit is provided in the fourth line 24.

[0029] The first circuit 12 includes a first relay 12a and a second relay 12b. The first relay 12a is arranged on the third line 23, and opens and closes the connection between the first line 21 and the first circuit 12. The second relay 12b is arranged on the fourth line 24, and opens and closes the connection between the second line 22 and the first circuit 12. For example, the first relay 12a and the second relay 12b are simultaneously controlled to be opened and closed according to a control signal from the control unit 5. When the welding of the main relay 3a is detected, the first relay 12a and the second relay 12b are controlled from the open state to the closed state. The first relay 12a and the second relay 12b can also be composed of switching elements such as transistors and FETs.

[0030] The first circuit 12 includes a detection element 30 and a transistor 31. The detection element 30 is, for example, a photocoupler including a light emitting diode and a phototransistor. The detection element 30 detects the current flowing in the fourth line 24. The first circuit 12 detects the welding of the main relay 3a based on whether the current from the first circuit power supply 14 flows to the detection element 30 via the main relay 3a.

[0031] A power source is connected to the output end of the detection element 30 via a resistor. If the current does not flow to the detection element 30, the detection element 30 is in a cut-off state. That is, the detection element 30 is in a state where a voltage from the power source is applied, and a high signal indicating a high voltage is output from the detection element 30. On the other hand, if the current flows to the detection element 30, the detection element 30 is in an on state and a low signal is output. If a low signal is output from the detection element 30, a well-known notification mechanism such as an alarm notifies that the main relay 3a has been welded.

[0032] The transistor 31 is provided in the fourth line 24. The transistor 31 is provided between the detection element 30 and the first circuit power supply 14. The transistor 31 is controlled to be always in the on state so that the first circuit 12 operates normally.

[0033] The first circuit power supply 14 is composed of an isolated DC / DC converter, and supplies a direct current to the first circuit 12. Figure 2 As shown, the first circuit power supply 14 supplies a direct current to the first circuit 12 in a manner that flows from the third line 23 to the fourth line 24 via the main relay 3 a .

[0034] The second circuit 16 is connected to the first circuit 12, and detects the voltage difference between the first line 21 and the second line 22. That is, the second circuit 16 detects the voltage difference between the contacts of the main relay 3a. When the main relay 3a is controlled from the closed state to the open state, the second circuit 16 cuts off the first circuit 12 and disables the detection element 30 only when a voltage difference is generated between the first line 21 and the second line 22.

[0035] The second circuit 16 is connected to the third line 23 and the fourth line 24. The second circuit 16 includes a full-wave rectifier 41, a smoothing circuit 42, a constant current circuit 43, and a photocoupler 44. When a voltage difference is generated between the first line 21 and the second line 22, the photocoupler 44 changes from an off state to an on state via the full-wave rectifier 41, the smoothing circuit 42, and the constant current circuit 43. By turning the photocoupler 44 into an on state, the GS of the transistor 31 provided in the first circuit 12 is short-circuited, and the transistor 31 changes from an on state to an off state. As a result, the first circuit 12 is cut off.

[0036] Next, refer to Figure 2 and Figure 3 The operation of the welding detection device 10 when detecting the welding of the main relay 3a when the power source connected to the load 2 is switched from the commercial power source A to the independent power source B will be described. Figure 3 1 is a timing chart showing the timing of the operation of the main relay 3a, the first relay 12a and the second relay 12b. After the control unit 5 controls the main relay 3a from the closed state to the open state, it controls the first relay 12a and the second relay 12b from the open state to the closed state. Thus, the first circuit 12 is connected to the power line L1.

[0037] If the main relay 3a is welded, Figure 3 As shown by the middle dotted line, the DC current from the first circuit power supply 14 flows from the third line 23 through the main relay 3a to the detection element 30. As a result, a low signal is output from the detection element 30, and a notification mechanism such as an alarm notifies welding.

[0038] When the main relay 3a is not welded, the DC current from the first circuit power supply 14 does not flow to the detection element 30. Therefore, the detection element 30 remains in the cut-off state, and the detection element 30 continues to output a high signal. As a result, the control unit 5 determines that the main relay 3a is not welded, controls the main relay 4a from the open state to the closed state, and switches the power supply connected to the load 2 from the commercial power supply A to the independent power supply B. In addition, in fact, for the main relay 3b, the power supply connected to the load 2 is also switched by the same method after the welding detection device 10 determines that the main relay 3b is not welded.

[0039] Here, when the main relay 3a is not welded, when a voltage of 100V is applied to the power line L1 with reference to the neutral line N, a voltage difference of 100V AC is generated between the first line 21 and the second line 22. Therefore, when the first circuit 12 is connected to the power line L1, a current of 100V AC flows in reverse, as shown in FIG. Figure 2As indicated by the two-dot chain line, a current flows from the second line 22 to the third line 23 of the first circuit 12 . This current flows to the detection element 30 , and there is a concern that the welding detection device 10 may erroneously detect welding of the main relay 3 a .

[0040] In order to prevent such erroneous detection, when a voltage difference of 100V is generated between the first line 21 and the second line 22, the first circuit 12 is cut off by the second circuit 16. Specifically, when a voltage difference (here, for example, a voltage difference of 100V) is generated between the first line 21 and the second line 22, the photocoupler 44 of the second circuit 16 is turned on. Then, by turning on the photocoupler 44, the transistor 31 is forced to change from the on state to the off state, and the first circuit 12 is cut off. As a result, the AC current of 100V can be prevented from flowing into the detection element 30. That is, the detection element 30 is maintained in the off state, and a high signal is continuously output from the detection element 30, so as to prevent the welding detection device 10 from erroneously detecting welding.

[0041] In addition, if no voltage difference is generated between the first line 21 and the second line 22, the AC 100V current will not flow back and will not flow into the first circuit 12 from the second line 22 side. Therefore, as described above, the first circuit 12 is used to detect the welding of the main relay 3a based on whether the DC current from the first circuit power supply 14 flows to the detection element 30.

[0042] Regarding the action of the welding detection device 10 when the power supply connected to the load 2 is switched from the independent power supply B to the industrial power supply A, only the main relay for detecting welding (in this case, the main relays 4a and 4b) is different, and the action is the same as the action when detecting the welding of the main relay 3a, so the description is omitted.

[0043] As mentioned above, although the embodiment of the welding detection device which is one aspect of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and various changes can be made without departing from the scope of the invention.

[0044] In the above embodiment, the welding of the main relay 3 a is detected by passing current through the detection element 30 . However, for example, the welding detection device 10 may be configured to detect the welding of the main relay 3 a without passing current through the detection element 30 .

[0045] In the above embodiment, the power switching device 1 is exemplified as a structure in which the power supply for supplying AC power to the load 2 is switched from one of the industrial power supply A and the independent power supply B to the other, but the power supply switched by the power switching device 1 is not limited to the above embodiment. As long as the power supply for supplying AC power to the load 2 is switched from one of the first system power supply and the second system power supply to the other, it can be used. For example, the power switching device 1 may be a structure that switches between the industrial power supply A and the backup power supply, or it may not be an industrial power supply.

[0046] In the above embodiment, the configuration in which the welding detection device 10 is adopted in the power supply switching device 1 is exemplified, but the application of the welding detection device 10 is not particularly limited. The welding detection device 10 can be adopted in various devices and circuits.

[0047] Industrial Applicability

[0048] According to the present invention, in a welding detection device that detects welding of a relay based on the presence or absence of current flowing through a detection element, erroneous detection of welding can be prevented.

[0049] Explanation of symbols

[0050] 2…load; 3a, 3b, 4a, 4b…main relay; 10…welding detection device; 12…first circuit; 14…first circuit power supply; 16…second circuit; 30…detection element; 21…first line; 22…second line.

Claims

1. A welding detection device for detecting welding of a main relay that opens and closes a connection between a load and a power supply that supplies AC power to the load, the welding detection device comprising: a first circuit including a detection element for detecting a current and connected to a first line connecting the power source with the main relay and a second line connecting the load with the main relay; a first circuit power supply that supplies a direct current to the first circuit; as well as a second circuit connected to the first circuit, detecting a voltage difference between the first circuit and the second circuit, When the main relay is controlled from a closed state to an open state, the first circuit detects welding of the main relay based on whether a current from the first circuit power supply flows to the detection element via the main relay. The second circuit cuts off the first circuit only when a voltage difference is generated between the first line and the second line when the main relay is controlled from a closed state to an open state.

2. The welding detection device according to claim 1, characterized in that: The first circuit further includes a first relay that opens and closes a connection with the first line, and a second relay that opens and closes a connection with the second line.

3. The welding detection device according to claim 1 or 2, characterized in that: The welding detection device is provided in a switching device that switches the power supply for supplying AC power to the load from one of a first system power supply and a second system power supply to the other. The switching device includes the main relay, The main relay includes a first main relay that opens and closes a connection between the first system power supply and the load, and a second main relay that opens and closes a connection between the second system power supply and the load.

4. A welding detection method, comprising: a welding detection device for detecting welding of a main relay, wherein the main relay opens and closes a connection between a load and a power supply for supplying AC power to the load, wherein the welding detection method comprises: The welding detection device comprises: a first circuit including a detection element for detecting a current and connected to a first line connecting the power source and the main relay and a second line connecting the load and the main relay; and a first circuit power supply that supplies a direct current to the first circuit, The cladding detection method comprises the following steps: a step of detecting welding of the main relay based on whether current from the first circuit power source flows to the detection element via the main relay when the main relay is controlled from a closed state to an open state; and A step of cutting off the first circuit only when a voltage difference is generated between the first line and the second line when the main relay is controlled from the closed state to the open state.

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