JP2025021770A - Current Switching Device - Google Patents

Abstract

To cut off a current without arc by solving the problem of deposition in a current switchgear using a mechanical latch type electromagnetic contactor.SOLUTION: A current switchgear comprises: a bidirectional semiconductor switch connected in parallel with a metal contact of a mechanical latch type electromagnetic contactor and consisting of two semiconductor switching elements 5 which are connected in reverse series; an insulation gate drive circuit 7 which outputs a control voltage for turning on or turning off to a gate of each semiconductor switching element 5; a diode bridge 9; and a constant voltage diode 10. A drive power source of a drive coil of the electromagnetic contactor is connected to an AC input terminal of the diode bridge 9, a DC output terminal of the diode bridge 9 is connected via a current limiting resistor 8 to an input terminal of the insulation gate drive circuit 7 and further, the constant voltage diode 10 for overvoltage protection is connected between DC output terminals of the diode bridge 9.SELECTED DRAWING: Figure 1

Description

The present invention relates to an AC or bidirectional DC current switching device, and in particular to a current switching device that includes a so-called mechanically latched electromagnetic contactor that excites a contact drive coil with an external drive power source only when the metal contact begins to be turned on or off, driving the metal contact to an on or off state, and then maintains that state even after the excitation of the contact drive coil is stopped, and a bidirectional semiconductor switch connected in parallel with the metal contact, and that drives the gate of the bidirectional semiconductor switch in an insulated manner using the drive power source for the contact drive coil, making it possible to open and close the metal contact without chattering when it is on, or the contact current when it is off, without generating an arc.

An electromagnetic contactor is a control device known as a plunger-type relay (including a type that is mechanically held by an electromagnet and spring, and a type that is held by a permanent magnet).
It should be noted that plunger-type relays also include electromagnetic switches (magnet switches), but an electromagnetic switch is an electromagnetic contactor to which a thermal relay has been added, and since the operation of the metal contacts is the same as that of an electromagnetic contactor, unless otherwise specified, in this specification the term electromagnetic contactor is taken to include electromagnetic switches.

The following two problems have been pointed out with such electromagnetic contactors: When the DC voltage and current are large enough, arcing between the contacts continues and the DC current cannot be interrupted, and even with AC, arcing of the metal contacts causes wear and welding problems.
If chattering occurs when the metal contacts are on, a large inrush/starting current is repeatedly opened and closed at high speed several to ten times, causing an arc between the metal contacts, which melts and evaporates the metal contacts, and then welding and consumption of the contact metal occurs. If contact welding occurs, the contacts cannot be controlled to open, the current continues, and this can cause serious damage to the system.

The inventors have proposed (but have not yet disclosed) a current switching device that can solve the problems of welding due to chattering of metal contacts in current switching devices using such electromagnetic contactors, and the problem of arc generation when interrupting AC or DC current (see Patent Document 1 below).

Patent application No. 2022-187004

However, there are also mechanically latched electromagnetic contactors that generate electromagnetic force for only a short time (about 50 ms) when the metal contacts begin to turn on or off, causing the metal contacts to go from closed to open, or from open to closed. Unlike ordinary electromagnetic contactors, these do not require a continuous flow of current through the contact drive coil even in the on state, and are characterized by the fact that there is no heat generation due to power consumption in the coil.
There are two types of mechanically latched electromagnetic contactors. One type has only one drive coil, and the movable iron closes the contacts depending on the direction of the coil current, or opens them when the coil current is reversed. Even if the drive current is stopped, the contacts maintain that state, i.e., are latched (single winding latching type).
The other type has two drive coils, one for closing the contacts and one for opening the contacts, and the open/closed state of the contacts can be changed by passing current through each coil individually, and that state can be maintained even after the current to the coils is stopped (two-winding latching type).

A common feature of these two types of mechanically latched electromagnetic contactors is that current flows through the drive coil only for a short period of time (approximately 50 ms) when the metal contacts begin to turn on or off.
On the other hand, the electromagnetic contactor described in Patent Document 1 requires that current continue to flow through the coil while the metal contacts are on, and the power supply that drives the coil cannot be turned off while the metal contacts are on.
Furthermore, because the power supply that drives the drive coil is also used as the power supply that drives the gate of the semiconductor switch, there is a problem that the gate drive control circuit described in Patent Document 1 cannot be used for the gate drive control circuit of the semiconductor switch of a current switching device that uses a latching electromagnetic contactor that turns off the power supply to the drive coil immediately after the metal contact is turned on.
Furthermore, in the case of a single winding latching type, when the contacts are opened, the coil current must be reversed, so the gate drive control circuit described in Patent Document 1 cannot be used.

The present invention was developed in consideration of the above-mentioned problems, and aims to solve the above-mentioned problems in current switching devices using mechanically latched electromagnetic contactors.

The present invention relates to a current switching device that is inserted between a bidirectional DC power supply or an AC power supply and a load. The above object of the present invention is achieved by a current switching device that includes a single-winding latching type mechanically latched electromagnetic contactor, a bidirectional semiconductor switch consisting of two semiconductor switching elements connected in reverse series and parallel to the metal contacts (hereinafter referred to as "contacts") of the electromagnetic contactor, an insulated gate drive circuit that outputs a control voltage for turning on or off to the control terminals of each of the semiconductor switching elements, a diode bridge, and a constant voltage diode, and an external drive power supply that is provided to supply a positive or negative pulse voltage to the drive coil of the electromagnetic contactor to close or open the contacts is connected to the AC input terminal of the diode bridge, and the DC output terminal of the diode bridge is connected to the input terminal of the insulated gate drive circuit via a current limiting resistor, and further, the constant voltage diode is connected between the DC output terminals of the diode bridge for overvoltage protection.

The above object of the present invention is also achieved by a current switching device comprising a two-winding latching type mechanically latched electromagnetic contactor, a bidirectional semiconductor switch consisting of two semiconductor switching elements connected in reverse series in parallel with the contacts of the electromagnetic contactor, an insulated gate drive circuit that outputs a control voltage for turning on or off to the control terminals of each of the semiconductor switching elements, two diodes, and a constant voltage diode for overvoltage protection, and the positive side of an external drive power source provided to separately and independently supply power to the drive coil for closing the contacts of the two drive coils of the electromagnetic contactor and the drive coil for opening the contacts of the drive coil is connected to the anode of each of the diodes, and the cathode of each of the diodes is connected to the input terminal of the insulated gate drive circuit via a current limiting resistor, and further, the cathode of the constant voltage diode is connected to the cathode of each of the diodes, and the anode of the constant voltage diode is connected to the earth side of the drive power source.

According to the current switching device of the present invention, when current is applied, the bidirectional semiconductor switch turns on before the metal contacts close. Therefore, even if "bouncing" or "rubbing" occurs when the metal contacts close, the current mainly flows toward the semiconductor switch, so no large arc is generated and therefore no welding of the metal contacts occurs. As a result, the problems of chattering and welding of the metal contacts are eliminated.

Furthermore, in the case of a current switching device using a single-winding latching type mechanically latched electromagnetic contactor, even if the direction of the current in the drive coil is switched when switching the open/closed state of the contacts, a voltage in the same direction is always input to the input terminal of the insulated gate drive circuit due to the action of the diode bridge, so that the on/off of the bidirectional semiconductor switch can be controlled by the output of the insulated gate drive circuit.
Furthermore, in the case of a current switching device using a two-winding latching type mechanically latched electromagnetic contactor, even if the drive power supplies for the respective drive coils are switched when switching the open/closed state of the contacts, a voltage is input to the input terminals of the insulated gate drive circuit via each diode, so that the on/off of the bidirectional semiconductor switch can be controlled by the output of the insulated gate drive circuit.

1 is a block diagram showing an example of a first embodiment of a current switching device according to the present invention; FIG. 1 is a diagram showing an example of a drive power supply for a single-winding latching type electromagnetic contactor. 4 is a diagram for explaining an operation sequence of the current switching device according to the present invention. FIG. FIG. 2 is a block diagram showing another example of the example of the first embodiment of the current switching device according to the present invention. FIG. 11 is a block diagram showing an example of a second embodiment of a current switching device according to the present invention. FIG. 1 is a diagram showing an example of a drive power supply for a two-winding latching type electromagnetic contactor.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
Fig. 1 is a block diagram showing an example of a first embodiment of the current switching device according to the present invention. The current switching device according to the present invention is used by being inserted between a bidirectional DC or AC power source (hereinafter simply referred to as "power source") 1 and a load 4, and includes a mechanically latched electromagnetic contactor (single winding latching type) having a drive coil 3, a contact 2 that performs an opening and closing operation by the force of an electromagnet when a drive power source (the part surrounded by a dotted line in Fig. 1, which is provided externally and is not a constituent element of the present invention) is turned on to the drive coil 3, a bidirectional semiconductor switch consisting of two semiconductor switching elements 5 connected in reverse series and connected in parallel to the contact 2, an insulated gate drive circuit 7 that outputs a control voltage for turning on or off to the control terminal (gate) of each semiconductor switching element 5, a diode bridge 9, and a constant voltage diode 10.

Furthermore, a resistor 6 (for example, 1 kΩ) is inserted between the output of the insulating gate drive circuit 7 and the gate of the semiconductor switching element 5 to prevent oscillation.
An external drive power supply is connected to the AC input terminal of the diode bridge 9. The DC output terminal of the diode bridge 9 is connected to the input terminal of the insulated gate drive circuit 7 via a current limiting resistor 8 (for example, 400 Ω to limit the current to approximately 10 mA), and a constant voltage diode 10 is connected between the DC output terminals of the diode bridge 9. When the current is interrupted to the drive coil 3 of the electromagnetic contactor, a high-voltage back electromotive force is generated due to inductance, but to prevent an excessive voltage from being applied to the insulated gate drive circuit 7 as a result, a constant voltage diode 10 (for example, 6 V) is connected to block this.

As the semiconductor switching element 5, a self-extinguishing semiconductor element capable of being turned on/off by control of a control terminal (gate), such as a MOSFET or a reverse conducting IGBT, can be used.
Furthermore, a photovoltaic output photocoupler (hereinafter referred to as "photovoltaic") can be used as the insulated gate drive circuit 7. A photovoltaic has an infrared LED and a photodiode array, and emits light from the internal infrared LED with a current of about 10 mA on the input side to generate an open circuit voltage of about 7 V maximum that is insulated from the photodiode array in the output section. Examples of such a photovoltaic include the TLP3906 manufactured by Toshiba Electronic Devices & Storage Corporation.

Figure 2 is a diagram showing an example of a drive power supply for a single-winding latching type electromagnetic contactor. When closing (setting) the contact 2, SW1 is turned on for a short time (about 20 ms) (then turned off) to apply the set power supply (positive voltage: +5 V as an example) to the drive coil 3. Even if SW1 is then turned off, the contact 2 is latched and the closed state is maintained.
When SW1 is turned off (SW2 is also off), the input to the insulated gate drive circuit 7 becomes 0 and the output of the insulated gate drive circuit 7 also becomes 0 and the semiconductor switching element 5 turns off. However, this does not cause a problem because contact 2 is latched and continues to be on.
On the other hand, when contact 2 is opened (reset), SW2 is turned on for a short time (about 20 ms) (then turned off) to apply a reset power supply (negative voltage: -5 V as an example) to drive coil 3. Even if SW2 is then turned off, contact 2 is latched and the open state is maintained.
When SW2 is turned off (SW1 is also off), the input to the insulated gate drive circuit 7 becomes 0, and the output of the insulated gate drive circuit 7 also becomes 0 and the semiconductor switching element 5 turns off. However, contact 2 opens approximately 10 ms after SW2 is turned on. At that point, the semiconductor switching element 5 is still in the on state, so no arc is generated when contact 2 opens.

The portion of the current switching device according to the present invention with the electromagnetic contactor (the combination of the contacts 2 and the drive coil 3) removed will be referred to as the "hybrid unit" 11 here. In other words, the current switching device according to the present invention can be constructed by retrofitting an existing electromagnetic contactor with a hybrid unit, so the hybrid unit can also be the subject of the invention.

FIG. 3 is a diagram for explaining the operation sequence of the current switching device according to the present invention.
When the set power is turned on, the semiconductor switching element (MOSFET) 5 turns on almost instantly (less than 1 ms) and current flows through the bidirectional semiconductor switch. At the same time, a drive current flows through the drive coil 3, but it takes about 10 ms for the contacts 2 to close. This is because it takes time, about 10 ms, for the electromagnetically driven plunger to start.
When the contact 2 is closed, the MOSFET 5 is on, so that no arc occurs at the contact 2.
When contact 2 is closed, the main current of the circuit flows through contact 2, so almost no current flows through the bidirectional semiconductor switch, which has a higher resistance than contact 2. When the set power supply is turned off approximately 10 ms after contact 2 is closed, the gate voltage of MOSFET 5 becomes zero and MOSFET 5 turns off, but current continues to flow through contact 2 because contact 2 is latched and maintains the closed state.

Next, when the reset power supply is turned on, a drive current flows in the reverse direction through the drive coil 3, and the contacts 2 attempt to open, but it takes about 10 ms for the contacts 2 to open. This is because it takes time, about 10 ms, for the electromagnetically driven plunger to start.
In addition, when the reset power supply is turned on, the semiconductor switching element (MOSFET) 5 turns on almost instantaneously. At this time, however, the contact 2 is still in the closed state due to the mechanical delay as described above, so that the main current of the circuit flows through contact 2, and almost no current flows through the bidirectional semiconductor switch due to the difference in the on-resistance between contact 2 and the semiconductor switch.
However, when contact 2 opens 10 ms later, MOSFET 5 is on, so the main current is commutated to the semiconductor switch and no arc occurs at contact 2. This is because an arc voltage of at least about 10 V is required to generate an arc, almost regardless of the current. When the reset power supply is turned off approximately 10 ms after contact 2 opens, the gate voltage of MOSFET 5 becomes zero, MOSFET 5 turns off, and the main current is interrupted.
That is, the main current is cut off at the timing when the reset power supply is turned off, by turning off the semiconductor switch.
This effect makes it possible to control the delay and jitter in the timing of closing/opening, which are drawbacks of electromagnetically driven contact switches, by using semiconductor switches connected in parallel.

FIG. 4 is a block diagram showing another example of the first embodiment of the current switching device according to the present invention.
The bidirectional semiconductor switch consisting of two MSFETs 5 connected in reverse series as shown in Fig. 1 is replaced with a bidirectional semiconductor switch consisting of a second diode bridge 12 and one or more MOSFETs 5 (one is shown in Fig. 4 for convenience, but two or more may be used), and the AC input terminals of the diode bridge 12 are connected in parallel to the contact 2, while the MOSFETs 5 are connected in parallel to the DC output terminals of the diode bridge 12 as shown in the figure. Note that the reason for connecting multiple MOSFETs 5 in parallel is to reduce the load per unit and suppress heat generation when handling a large current, and it goes without saying that a single MOSFET will suffice depending on the amount of current handled.
When the drive power supply is turned on, the bidirectional semiconductor switch is turned on by a gate voltage pulse from the insulated gate drive circuit 7, but if there is a delay after that and contact 2 is turned on, a sneak current may be generated in the bidirectional semiconductor switch from the on voltage of contact 2. Since the forward voltage of this diode bridge 12 is about 2V to 3V, this sneak current can be completely blocked.
Other points are the same as those in the embodiment of FIG. 1, so the explanation will be omitted.

FIG. 5 is a block diagram showing an example of a second embodiment of a current switching device according to the present invention.
The difference from the example of the first embodiment shown in Fig. 1 is that the drive coil 3 of the electromagnetic contactor is a single winding latching type in the first embodiment, whereas it is a double winding latching type in the second embodiment. In the double winding latching type electromagnetic contactor, the drive coil 3 is divided into a set coil (closing coil) 3a and a reset coil (opening coil) 3b, which are provided separately, and the drive power source is also provided with a set power source and a reset power source separately. In the single winding latching type, a set power source and a reset power source are also provided separately, but the only difference is the direction of the current, which is supplied to the same drive coil 3.

In contrast, in the case of a two-winding latching type, although the drive coils are different, the direction of the supplied current (polarity of voltage) is the same.
Therefore, since the polarity of the input voltage to the insulated gate drive circuit 7 does not change between the set and reset states as in the first embodiment, the diode bridge 9 is not necessary, and instead, two reverse current prevention diodes 9 (one for set and one for reset) are provided.
That is, the positive side of the set power supply or reset power supply is connected to the anode of each diode, and the cathode of each diode is connected to the input terminal of the insulated gate drive circuit 7 via a current limiting resistor 8, and further, the cathode of the constant voltage diode 10 is connected to the cathode of each diode 9, and the anode of the constant voltage diode 10 is connected to the earth side of the set power supply or reset power supply. Since the rest is the same as in the first embodiment, a description thereof will be omitted.
Also, for this second embodiment, there is a modification (FIG. 4) similar to that of the first embodiment, but the description is the same as for FIG. 4 and will be omitted.

Fig. 6 is a diagram showing an example of a drive power supply for a two-winding latching type electromagnetic contactor. When the contact 2 is closed (set), SW1 is turned on for a short time (about 20 ms) (then turned off) to apply a set power supply (positive voltage: +5V as an example) to the drive coil 3a. Even if SW1 is then turned off, the contact 2 is latched and the closed state is maintained.
When SW1 is turned off (SW2 is also off), the input to the insulated gate drive circuit 7 becomes 0 and the output of the insulated gate drive circuit 7 also becomes 0 and the semiconductor switching element 5 turns off. However, this does not cause a problem because contact 2 is latched and continues to be on.
On the other hand, when contact 2 is opened (reset), SW2 is turned on for a short time (about 20 ms) (then turned off) to apply a reset power supply (positive voltage: +5 V as an example) to drive coil 3b. Even if SW2 is then turned off, contact 2 is latched and the open state is maintained.
The rest is the same as in the case of the drive power supply for a single winding latching type electromagnetic contactor, so a description thereof will be omitted.

This concludes the explanation, but the mechanically latched electromagnetic contactor in this invention encompasses all electromagnetic contactors whose contacts are locked in their original state even after the power to the relay drive coil is turned off, including those generally known as latching relays, regardless of the contact locking method (magnetic locking type/mechanical locking type).

1: Bidirectional DC power supply or AC power supply 2: Metal contact (of electromagnetic contactor) 3: Drive coil (of electromagnetic contactor) 4: Load 5: Semiconductor switching element (MOSFET)
6: Gate resistor 7: Insulated gate drive circuit (photovoltaic)
8: Current limiting resistor 9: Diode bridge 10: Constant voltage diode 11: Hybridization unit 12: Second diode bridge

Claims (5)

A current switching device that is inserted between a bidirectional DC power source or an AC power source and a load, the current switching device comprising:
A single-winding latching type mechanically latched electromagnetic contactor, and a bidirectional semiconductor switch consisting of two semiconductor switching elements connected in anti-series in parallel with a metal contact (hereinafter referred to as "contact") of the electromagnetic contactor;
an insulated gate drive circuit that outputs a control voltage for turning on or off each of the semiconductor switching elements to a control terminal of the semiconductor switching elements;
A diode bridge;
and a constant voltage diode.
a current switching device, characterized in that an external drive power supply provided for supplying a positive or negative voltage to a drive coil of the electromagnetic contactor to close or open the contacts is connected to an AC input terminal of the diode bridge, a DC output terminal of the diode bridge is connected to an input terminal of the insulated gate drive circuit via a current limiting resistor, and further, the constant voltage diode for overvoltage protection is connected between the DC output terminals of the diode bridge. A current switching device that is inserted between a bidirectional DC power source or an AC power source and a load, the current switching device comprising:
A two-winding latching type mechanically latched electromagnetic contactor, and a bidirectional semiconductor switch consisting of two semiconductor switching elements connected in anti-series in parallel with the contacts of the electromagnetic contactor;
an insulated gate drive circuit that outputs a control voltage for turning on or off each of the semiconductor switching elements to a control terminal of the semiconductor switching elements;
Two reverse current prevention diodes;
and a constant voltage diode for overvoltage protection.
a positive side of an external drive power supply provided to separately and independently supply power to one of the two drive coils of the electromagnetic contactor for closing the contacts and to one of the drive coils for opening the contacts, the positive side of which is connected to the anode of each of the diodes, the cathode of each of the diodes being connected via a current limiting resistor to an input terminal of the insulated gate drive circuit, and the cathode of the constant voltage diode being connected to the cathode of each of the diodes, the anode of the constant voltage diode being connected to the earth side of the drive power supply. The bidirectional semiconductor switch consisting of the two semiconductor switching elements connected in reverse series is replaced with a bidirectional semiconductor switch consisting of a second diode bridge and one or more semiconductor switching elements,
an AC input terminal of the second diode bridge is connected in parallel to the contact;
3. The current switching device according to claim 1, wherein the semiconductor switching element is connected in parallel to a DC output terminal of the second diode bridge. A hybridization unit used by being connected in parallel to the contacts of the electromagnetic contactor of the current switching device according to claim 1, the hybridization unit comprising:
a bidirectional semiconductor switch including two semiconductor switching elements connected in anti-series in parallel with the contact;
an insulating gate drive circuit that outputs a control voltage for turning on or off each of the semiconductor switching elements to a control terminal of the semiconductor switching elements; a diode bridge; and a constant voltage diode;
a hybridization unit characterized in that an external drive power supply provided for supplying a positive or negative voltage to a drive coil of the electromagnetic contactor to close or open the contacts is connected to an AC input terminal of the diode bridge, a DC output terminal of the diode bridge is connected to an input terminal of the insulated gate drive circuit via a current limiting resistor, and further, the constant voltage diode for overvoltage protection is connected between the DC output terminals of the diode bridge. A hybridization unit used by being connected in parallel to the contacts of the electromagnetic contactor of the current switching device according to claim 2, the hybridization unit comprising:
a bidirectional semiconductor switch including two semiconductor switching elements connected in anti-series in parallel with the contact;
an insulating gate drive circuit that outputs a control voltage for turning on or off each of the semiconductor switching elements to a control terminal of the semiconductor switching elements, two reverse current prevention diodes, and a constant voltage diode for overvoltage protection;
a positive side of an external drive power supply provided to separately and independently supply power to one of the two drive coils of the electromagnetic contactor for closing the contacts and to one of the drive coils for opening the contacts, the positive side of the external drive power supply being connected to the anodes of the diodes, the cathodes of the diodes being connected to input terminals of the insulated gate drive circuit via current limiting resistors, and the cathodes of the constant voltage diodes being connected to the cathodes of the diodes, the anodes of the constant voltage diodes being connected to the earth side of the drive power supply.