Electromagnetic relay

Abstract

This electromagnetic relay includes a pair of fixed contacts, a movable member, and a current sensor. The movable member includes a pair of movable contacts positioned facing the pair of fixed contacts. The current sensor is positioned on the movable member and detects current flowing between the pair of movable contacts.

Description

electromagnetic relay

[0001] The present invention relates to an electromagnetic relay.

[0002] Patent Literature 1 discloses an arc detection device that determines whether an arc has occurred based on the detection results of a current sensor. When the arc detection device determines that an arc has occurred, it opens the contacts of an electromagnetic relay arranged on the power line to interrupt the arc that has occurred in the solar cell string.

[0003] Japanese Patent Application Laid-Open No. 2017-161417

[0004] In Patent Document 1, the current sensor is arranged to measure the current flowing through the power line. Therefore, when an arc is detected, it is difficult to determine whether the arc is occurring in the power line or inside the electromagnetic relay. If it were possible to determine whether an arc is occurring inside the electromagnetic relay, for example, it would be possible to know when an arc occurs inside the electromagnetic relay that the electromagnetic relay has reached the end of its life or that it is time to replace it.

[0005] An object of the present invention is to provide an electromagnetic relay that makes it possible to determine whether an arc is occurring in the power line or inside the electromagnetic relay.

[0006] An electromagnetic relay according to one aspect of the present invention includes a pair of fixed contacts, a movable member, and a current sensor. The movable member includes a pair of movable contacts arranged opposite the pair of fixed contacts. The current sensor is arranged on the movable member and detects a current flowing through the pair of movable contacts.

[0007] In this electromagnetic relay, a current sensor is disposed on the movable member and detects a current flowing between a pair of movable contacts. This makes it possible to determine whether an arc is occurring in the power line or inside the electromagnetic relay by configuring a control unit that controls the opening and closing of the electromagnetic relay contacts to determine the open / closed state of the electromagnetic relay contacts when an arc is occurring. For example, if the control unit determines that an arc is occurring when the pair of movable contacts are in contact with the pair of fixed contacts in a closed state, it can be determined that an arc is occurring in the power line. On the other hand, if the control unit determines that an arc is occurring when the pair of movable contacts are separated from the pair of fixed contacts in an open state, it can be determined that an arc is occurring inside the electromagnetic relay.

[0008] The electromagnetic relay may further include an arc detection unit that determines whether an arc has occurred based on the detection result of the current sensor. In this case, the electromagnetic relay can determine whether an arc has occurred in the power line or inside the electromagnetic relay.

[0009] The electromagnetic relay may further include an open / close determination unit that determines the open / close state of the pair of movable contacts, and an alarm signal output unit. The alarm signal output unit may output a first alarm signal to the outside when the arc determination unit determines that an arc has occurred and the open / close determination unit determines that the pair of movable contacts are open from the pair of fixed contacts. In this case, it is possible to notify an administrator that an arc has occurred inside the electromagnetic relay.

[0010] The alarm signal output unit may output a second alarm signal to the outside when the arc determination unit determines that an arc has occurred and the open / close determination unit determines that the pair of movable contacts is in contact with the pair of fixed contacts. In this case, it becomes possible to notify an administrator that an arc has occurred in the power line.

[0011] The electromagnetic relay may further include a voltage sensor for determining the open / closed state of the pair of movable contacts, in which case the open / closed state of the pair of movable contacts can be easily determined.

[0012] The electromagnetic relay may further include a semiconductor switching element disposed between the pair of movable contacts, which makes it possible to interrupt an arc, for example, if an arc occurs inside the electromagnetic relay.

[0013] The electromagnetic relay may further include a substrate. The movable member may be the substrate. The current sensor may be mounted on the substrate. In this case, in an electromagnetic relay in which the substrate is used as the movable member, it is possible to determine whether an arc is occurring in the power line or inside the electromagnetic relay. In addition, the current sensor can be easily positioned.

[0014] The electromagnetic relay may further include an auxiliary movable contact arranged on the circuit board for determining whether the pair of movable contacts are in contact with the pair of fixed contacts, making it easy to determine the open / closed state of the pair of movable contacts.

[0015] According to the present invention, it is possible to provide an electromagnetic relay that makes it possible to determine whether an arc is occurring in the power line or inside the electromagnetic relay.

[0016] It is a schematic block diagram showing the configuration of a solar power generation system to which an electromagnetic relay according to an embodiment is applied. It is a block diagram showing the functional configuration of a control unit. It is a diagram for explaining another embodiment according to another embodiment. It is a diagram for explaining the arrangement of switching elements. It is a diagram for explaining another embodiment of a movable member.

[0017] Hereinafter, a photovoltaic power generation system 1 including an electromagnetic relay according to an embodiment will be described with reference to the drawings. Fig. 1 is a block diagram schematically showing the configuration of the photovoltaic power generation system 1. The photovoltaic power generation system 1 is a system for outputting power output from at least one string including a plurality of photovoltaic modules to a load or a power grid.

[0018] The photovoltaic power generation system 1 includes a string 2 , a power conditioner 3 , and an electromagnetic relay 4 .

[0019] The string 2 is made up of a plurality of solar cell modules connected in series. Each solar cell module includes a plurality of solar cell cells (not shown) connected in series. The string 2 is connected to a power conditioner 3.

[0020] The power conditioner 3 converts DC power output from the string 2 into AC power and outputs the AC power. The power conditioner 3 is connected to a power grid 5.

[0021] The power conditioner 3 has the same configuration as a conventional power conditioner, and includes circuits (not shown) such as a converter circuit, an inverter circuit, and a charge / discharge circuit.

[0022] The electromagnetic relay 4 is provided to interrupt an arc that occurs in the power lines 6a and 6b that connect the string 2 and the power conditioner 3. The electromagnetic relay 4 is disposed on the power lines 6a and 6b. The power line 6a is a positive-side electric circuit, and the power line 6b is a negative-side electric circuit.

[0023] The electromagnetic relay 4 is a mechanical relay that mechanically operates contacts, and includes a first switching unit 7, a second switching unit 8, a current sensor 9, and a control unit 10.

[0024] The first switching unit 7 and the second switching unit 8 have a double-break contact structure. The first switching unit 7 is connected to the power line 6a. The first switching unit 7 includes a pair of fixed contacts 11 and a movable member 12. The movable member 12 is a movable contact piece and is made of a conductive material. The movable member 12 includes a pair of movable contacts 12a. The pair of movable contacts 12a are arranged opposite the pair of fixed contacts 11. The movable member 12 is configured to be movable between a closed position where the pair of movable contacts 12a contact the pair of fixed contacts 11 and an open position where the pair of movable contacts 12a are separated from the pair of fixed contacts 11.

[0025] The second switching unit 8 is disposed on the power line 6b. The second switching unit 8 includes a pair of fixed contacts 13 and a movable member 14. The movable member 14 includes a pair of movable contacts 14a. The second switching unit 8 has the same configuration as the first switching unit 7 except for its arrangement, and therefore will not be described here.

[0026] The current sensor 9 is disposed on the movable member 12. The current sensor 9 is integrated with the movable member 12 and configured to move integrally with the movable member 12. The current sensor 9 detects a current flowing between a pair of movable contacts 12 a and outputs a detection signal to the control unit 10.

[0027] The control unit 10 is a functional configuration realized by a CPU, and is realized by the CPU executing a program stored in a ROM, a RAM, etc. The control unit 10 is supplied with power from a control power supply 20. The control power supply 20 is supplied with power from, for example, a commercial power supply. The control power supply 20 may also be generated from power generated by a solar cell module.

[0028] 2, the control unit 10 includes an arc determination unit 10a, a switching control unit 10b, a switching determination unit 10c, and an alarm signal output unit 10d. The arc determination unit 10a determines the occurrence of an arc based on the detection result of the current sensor 9. The configuration of the arc determination unit 10a is the same as that of a conventional unit. The arc determination unit 10a includes an amplifier, a filter, and an A / D converter (not shown).

[0029] The filter is a band-pass filter (BPF) that passes only current within a predetermined frequency range from the current output from the amplifier. The A / D converter converts the analog current signal that has passed through the filter into a digital signal and outputs it to the arc determination unit 10a.

[0030] The arc determination unit 10a performs an FFT on the digital signal output from the A / D conversion unit to generate a power spectrum of the current, and uses the generated power spectrum to determine whether an arc has occurred. The arc determination unit 10a may also use the frequency spectrum of the current signal obtained by performing a Fourier transform on the time waveform of the current signal output from the current sensor 9 to determine whether an arc has occurred.

[0031] The switching control unit 10b controls the opening and closing of the first switching unit 7 and the second switching unit 8 via a drive circuit (not shown) that controls the coil voltage supplied to the coil of the electromagnetic relay 4. The drive circuit controls the opening and closing of the first switching unit 7 and the second switching unit 8, for example, in accordance with an input signal output from the switching control unit 10b. When the control signal from the switching control unit 10b indicates ON, the drive circuit controls the first switching unit 7 and the second switching unit 8 to a closed state, and when the control signal from the switching control unit 10b indicates OFF, the drive circuit controls the first switching unit 7 and the second switching unit 8 to an open state.

[0032] When the arc determination unit 10a determines that an arc has occurred, the switching control unit 10b switches the first switching unit 7 and the second switching unit 8 from the closed state to the open state via the drive circuit, thereby making it possible to interrupt the arc when it has occurred in the power lines 6a, 6b.

[0033] When the arc determination unit 10a determines that an arc has occurred, the switching determination unit 10c determines the switching states of the first switching unit 7 and the second switching unit 8. The switching determination unit 10c determines the switching states of the first switching unit 7 and the second switching unit 8, for example, by determining whether or not an input signal indicating ON is output from the control unit 10 to the drive circuit.

[0034] The alarm signal output unit 10d outputs a first alarm signal to the outside when the arc determination unit 10a determines that an arc has occurred and that the pair of movable contacts 12a, 14a are in an open state where they are separated from the pair of fixed contacts 11, 13. The first alarm signal is a signal indicating that an arc has occurred inside the electromagnetic relay 4.

[0035] The alarm signal output unit 10d outputs a second alarm signal to the outside when the arc determination unit 10a determines that an arc has occurred and that the pair of movable contacts 12a, 14a are in a closed state in contact with the pair of fixed contacts 11, 13. The second alarm signal is a signal indicating that an arc has occurred in the power lines 6a, 6b.

[0036] In the above-described electromagnetic relay 4, the current sensor 9 is disposed on the movable member 12 and detects the current flowing between the pair of movable contacts 12 a. When the arc determination unit 10 a determines that an arc has occurred, the open / close determination unit 10 c determines the open / close states of the first switch 7 and the second switch 8. This makes it possible to determine whether the arc has occurred in the power lines 6 a, 6 b or inside the electromagnetic relay 4 when the arc determination unit 10 a determines that an arc has occurred.

[0037] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0038] 3, the electromagnetic relay 4 may further include a semiconductor switching element 30. The semiconductor switching element 30 is disposed between a first movable contact 31 and a second movable contact 32 of the pair of movable contacts 12a. The first movable contact 31 is connected to the second movable contact 32 via the semiconductor switching element 30. The opening and closing of the semiconductor switching element 30 is controlled by the control unit 10. The semiconductor switching element 30 is, for example, a MOSFET element or an IGBT (Insulated Gate Bipolar Transistor) element.

[0039] In the embodiment shown in FIGS. 4 and 5 , the movable member 12 is configured by a substrate 40. That is, the substrate 40 is a movable substrate including a pair of movable contacts 12 a. The substrate 40 is, for example, a printed circuit board, and is formed of an insulating material such as resin. The current sensor 9 is mounted on the substrate 40. In the embodiment shown in FIGS. 4 and 5 , the electromagnetic relay 4 includes an auxiliary movable contact 42, an auxiliary fixed contact (not shown), and a heat sink 43. The auxiliary movable contact 42 is an auxiliary contact for determining whether the pair of movable contacts 12 a are in contact with the pair of fixed contacts 11. The auxiliary movable contact 42 is disposed opposite the auxiliary fixed contact. The auxiliary movable contact 42 is a contact used to determine whether the first opening / closing unit 7 is in a conductive state. The auxiliary movable contact 42 is disposed on a monitor terminal 44 disposed on the substrate 40. Note that the substrate 40 may be a metal substrate.

[0040] 5, the heat sink 43 is disposed on the rear surface side of the pair of movable contacts 12a on the substrate 40. The heat sink 43 may be, for example, a metal plate.

[0041] In the above embodiment, the second switching unit 8 may be omitted. The electromagnetic relay 4 may include a voltage sensor for determining the open / closed state of the pair of movable contacts 12 a. The voltage sensor may be arranged to detect the voltage of the first switching unit 7, for example.

[0042] The control unit 10 may be disposed outside the electromagnetic relay 4 or may be disposed on the movable member 12 .

[0043] The current sensor 9 may be disposed in the movable member 14. In this case, the current sensor 9 detects the current flowing between the pair of movable contacts 14a. The current sensor 9 may be disposed in each of the movable members 12 and 14. In this case, for example, when an arc occurs inside the electromagnetic relay 4, it becomes possible to determine whether the arc is occurring in the first switching unit 7 or the second switching unit 8.

[0044] 4: electromagnetic relay, 11: one pair of fixed contacts, 12a: one pair of movable contacts, 10a: arc determination unit, 10b: switching control unit, 10c: switching determination unit, 10d: alarm signal output unit, 30: semiconductor switching element, 40: circuit board, 42: auxiliary movable contact

Claims

1. An electromagnetic relay comprising: a pair of fixed contacts; a movable member including a pair of movable contacts arranged opposite the pair of fixed contacts; and a current sensor arranged on the movable member for detecting a current flowing between the pair of movable contacts.

2. The electromagnetic relay according to claim 1, further comprising an arc determination unit that determines the occurrence of an arc based on the detection result of the current sensor.

3. An electromagnetic relay as claimed in claim 2, further comprising: an open / close determination unit that determines the open / closed state of said pair of movable contacts; and an alarm signal output unit that outputs a first alarm signal to the outside when said arc determination unit determines that said arc has occurred and said pair of movable contacts are in an open state from said pair of fixed contacts.

4. An electromagnetic relay as described in claim 2, further comprising: an open / close determination unit that determines the open / close state of the pair of movable contacts; and an alarm signal output unit that outputs a second alarm signal to the outside when the arc determination unit determines that the arc has occurred and the open / close determination unit determines that the pair of movable contacts are in contact with the pair of fixed contacts.

5. An electromagnetic relay according to any one of claims 1 to 4, further comprising a voltage sensor for determining the open / closed state of the pair of movable contacts.

6. An electromagnetic relay according to any one of claims 1 to 4, further comprising a semiconductor switching element disposed between the pair of movable contacts.

7. An electromagnetic relay according to any one of claims 1 to 4, further comprising a substrate, the movable member being the substrate, and the current sensor being mounted on the substrate.

8. An electromagnetic relay according to any one of claims 1 to 4, further comprising an auxiliary movable contact for determining whether the pair of movable contacts are in contact with the pair of fixed contacts.

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