Protector for direct-current high-voltage current

Abstract

To provide a protector for a direct-current high-voltage current that can be used stably for a long time by immediately attenuating sparks generated between contacts and suppressing ignition and flame propagation even when handling direct-current high voltage of 500 V or higher.SOLUTION: A device includes a fixed contact 11 and a movable contact 21, the movable contact approaching and separating from the fixed contact 11 in accordance with the inversion operation of a bimetal 31 made of a reversing bimetal. A magnet 40 is arranged at side parts of the fixed contact 11 and the movable contact 21. A contact-opening distance between the two contacts is 1.5-2 mm, and the magnet 40 is arranged continuously over the entire vertical range corresponding to the contact-opening distance. The magnet 40 is a ferrite magnet having heat resistance of 300°C or higher, and the structure is configured so that one inversion operation of the reversing bimetal generates the contact-opening distance. At least the surfaces of the fixed contact 11 and the movable contact 21 are formed of a binary alloy or a ternary alloy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protector (overheat protector) for high voltage DC current. [Background technology]

[0002] A conventional thermal protector proposal is described in Patent Document 1. This proposes disposing a bimetal between a fixed contact and a moving contact, and sealing an inert gas inside the casing. However, sealing an inert gas inside the casing increases the number of manufacturing and quality control processes, which can also be a factor in increasing costs.

[0003] On the other hand, in recent years, there has been a demand for thermal protectors that can handle high-voltage DC currents of 500 V or more. When using such high-voltage DC currents, if a spark or arc (hereinafter, both will be referred to as a spark) occurs between the contacts, it will immediately burn the surrounding components. To solve this problem, sealing an inert gas inside the casing, as in Patent Document 1, is an effective means, but as mentioned above, there are issues such as increased costs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-174816 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a protector for high-voltage DC current that can be used stably for a long period of time by immediately attenuating sparks generated between contacts to suppress ignition and fire spread, regardless of whether the environment is an inert gas atmosphere or not, even when the protector is used for high-voltage DC current, particularly for high-voltage DC current of 500 V or more. [Means for solving the problem]

[0006] The inventor has succeeded in developing a protector for DC high voltage current that can solve the above-mentioned problems, in which a bimetal switch is placed in a casing and has a movable contact on a contact plate that moves toward and away from a fixed contact as the bimetal reverses its motion. In the present invention, a magnet is disposed around the area between the fixed contact and the movable contact, thereby attenuating sparks between the two contacts. The magnet is disposed over the entire area of ​​the contact opening in the vertical direction, on at least one side along the longitudinal direction of the contact plate, and in an area longer than the length of the movable part of the contact plate. In carrying out the present invention, the outer dimensions of the casing are 40 x 60 x 33 mm or more, and one magnet (48 x 22 x 10t) of 130 mT or more is arranged on the right or left side of the contact plate, The bimetal may be circular in plan view with a diameter of 25 mm or more, and the contact opening between the fixed contact and the movable contact may be 1.5 to 2 mm. It is also desirable that the DC high voltage current is 500V or higher, and that the magnet is a ferrite magnet with an insulation resistance of 50 to 100MΩ and a heat resistance of 300°C or higher. [Effects of the Invention]

[0007] The present invention has provided a protector for DC high voltage current that can be used stably for a long period of time by immediately attenuating sparks that occur between contacts, thereby suppressing ignition and fire spread, even when targeting DC high voltage current, particularly DC high voltage current of 500 V or more, regardless of whether the environment is an inert gas atmosphere or not. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a left side view showing the internal structure of a protector for a high voltage DC current according to an embodiment of the present invention; [Figure 2] FIG. 2 is a plan view showing the internal structure of the DC high-voltage current protector. [Figure 3] FIG. 2 is a front view showing the internal structure of the DC high-voltage current protector. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (overview) In the DC high voltage current protector of this embodiment, a bimetal switch is assembled inside a cylindrical casing 41. In the following description of the present invention, the relationships of up, down, front, back, left and right merely indicate relative positional relationships, and the positional relationships may be changed within the scope of the present invention.

[0010] The bimetal switch has as its main components a fixed contact 11, a movable contact 21, a contact plate 22 having the movable contact 21 at its free end, a bimetal 31 arranged below the contact plate 22, and a magnet 40 arranged around the area between the fixed contact 11 and the movable contact 21. As shown in FIG. 2, the magnet 40 is disposed only on the left side of the periphery of the fixed contact 11 and the movable contact 21.

[0011] This bimetal switch is configured so that as the temperature rises, the bimetal 31 reverses from a closed state (see Figures 1 and 3) in which the fixed contact 11 and the movable contact 21 are in contact, pushing up the tip side of the contact plate 22 and changing to an open state (not shown) in which the contact opening dimension between the two contacts is 1.5 to 2 mm or more.

[0012] This DC high-voltage current protector equipped with a bimetal switch is attached to a temperature-measuring object, such as a hot water tank, to detect a rise in the object's temperature. When it detects that the object's temperature has risen above a predetermined temperature, it is placed in an external circuit and performs a specified operation, such as issuing a detection signal or cutting off power to the hot water tank's heater. (Regarding fixed contact 11)

[0013] 1, the fixed contact 11 is attached by a fixing means such as a screw or press-fitting to a contact stand 46 that is one step higher than the right side of the bottom 43 of the casing 41. The fixed contact 11 can be connected to a power source or the like on the positive side of an external circuit (not shown) by having the fixed terminal 12 connected inside the casing 41 protrude from the right wall 42 to the outside. (Regarding the moving contact 21)

[0014] The movable contact 21 is disposed above the fixed contact 11 so as to face the fixed contact 11. The movable contact 21 is attached to the underside of the tip (free end) of a contact plate 22 made of a conductive plate. The base end of the contact plate 22 is fixed by a fixture 23 to a step 45 that is one step higher than the left side of the bottom 43 of the casing 41 . The contact plate 22 can be connected to an external circuit via the mounting fixture 23 and the movable terminal 27, and in the external circuit, the movable contact 21 and the movable terminal 27 are grounded and act as negative poles.

[0015] It is preferable that the fixed contact 11 and the movable contact 21 have a shape that allows for point contact. Also, the contacts can be made of various conductors, but it is preferable to make them of a binary alloy of silver and nickel, or even a ternary alloy. The movable contact 21 is fixed to the contact plate 22 by caulking. This fixing can be implemented in various ways, for example, it may be fixed by high-temperature solder, so as to form a fail-safe mechanism in which the movable contact 21 and contact plate 22 become unable to conduct electricity when the temperature rises above the melting point of the high-temperature solder. (About Bimetal 31)

[0016] Bimetal 31 is a plate-like body (circular in plan view with a diameter of 25 mm in Fig. 2) made of an inverting bimetal that inverts as the temperature rises, and is placed below contact plate 22. An opening 44 is formed in bottom 43 of the casing below it, so that when this protector is attached to an object to be measured (not shown), the heat is efficiently applied to bimetal 31.

[0017] 1, the peripheral edge of the bimetal 31 is slidably fitted loosely between the bottom 43 and the bottom cover 52 attached thereto, which has a central opening, thereby providing a configuration in which heat from the object to be measured is most easily transmitted. Note that an example of a slidable support structure is one in which a retaining groove is formed in the peripheral wall of the casing 41 close to the opening 44, and the peripheral edge of the bimetal 31 is loosely fitted into the retaining groove, but a fixed structure is also acceptable as long as the bimetal 31 can be reversed.

[0018] 1, since the bimetal 31 is disposed on the bottom surface of the casing 41 as described above, a distance is created between the bimetal 31 and the contact plate 22. For this reason, in this example, the contact leg 28 is provided on the underside of the contact plate 22. The length of the contact leg 28 may be finely adjustable. (contact opening and closing)

[0019] As shown in FIG. 1, at normal temperatures, the bimetal 31 does not reverse and does not push up the contact plate 22. As the temperature rises, the bimetal 31 reverses. Specifically, as the bimetal 31 reverses, its center suddenly pushes up the underside of the contact plate 22 via the abutment leg 28, causing the contact plate 22 to rise. This opens the gap between the fixed contact 11 and the movable contact 21 to a predetermined contact opening dimension. In this case, even when a high-voltage DC current of 500 V or even 1000 V or more is used, the contact opening dimension can be kept to 1.5 to 2 mm by effectively suppressing sparks.

[0020] 1, contact plate 22 can be implemented as a generally straight contact plate when viewed from the side, but in this example, it is implemented as a plate-like body bent slightly downward at a portion near the base end. The reverse actuation temperature of bimetal 31 can be changed as appropriate depending on the required detection temperature, but in this example, the reverse actuation temperature can be set to approximately 120°C, and the release temperature can be set to approximately -40°C to 40°C.

[0021] In these embodiments, a manual reset switch 50 is provided to accommodate the need to return the fixed contact 11 and the movable contact 21 to the closed state before the temperature of the bimetal 31 drops to the return temperature. The manual reset switch 50 presses down on the contact plate 22 from above to forcibly close the contact, and can reverse the bimetal 31 back to its pre-reversal return state even before the ambient temperature drops to the return temperature. In the example of FIG. 1, the manual reset switch 50 is equipped with a stem that penetrates a top cover 51 attached to the open top end of the casing 41. The stem that protrudes above the top cover 51 is manually or mechanically pressed down against the biasing force of a spring (not shown) to press down the contact plate 22 and the bimetal 31 to the closed state, but this switch can be changed to another type or omitted.

[0022] (Regarding magnet 40) It is desirable to prevent sparks from occurring when the contacts are opened and closed. After extensive research, the inventors finally succeeded in distributing and attenuating any sparks that may occur by arranging the magnet 40 over an area longer than the length of the movable portion of the contact plate 22. This confirmed that it was possible to reliably prevent ignition caused by sparks that accompany the opening and closing of the contacts, even with high DC voltage current, and thus the present invention was completed.

[0023] In the example of FIG. 1 , the magnet 40 is disposed over a length sufficient compared to the diameter of the fixed contact 11 and the movable contact 21. Specifically, the magnet 40 is disposed in an area longer than the length of the movable portion of the contact plate 22. More specifically, one magnet (48 × 22 × 10t) 130 mT is disposed on the right or left side of the contact plate. By making the magnet 40 sufficiently long in this way, the magnetic flux density can be increased and the magnetic field can be exerted to points far from the fixed contact 11 and the movable contact 21. As a result, sparks generated when the contacts are opened or closed are dispersed, reducing the spark heat and protecting the contacts, contact plate, casing, and other surrounding components.

[0024] The magnet 40 is arranged continuously across the entire contact opening dimension in the vertical direction (see FIG. 1). The thickness of the magnet 40 is equal to or greater than the diameter of the fixed contact 11 and the movable contact 21. In the example of FIG. 2, the magnet 40 is rectangular in plan view.

[0025] Since magnet 40 is exposed to the high temperatures of sparks, it is preferable that it has high heat resistance (the ability to maintain magnetism even at high temperatures); specifically, a ferrite magnet with an insulation resistance of 50 to 100 MΩ and a heat resistance of 300°C or higher is appropriate.

[0026] Since the spark damping effect is exerted by the magnetic force of the magnet 40, it is desirable to have a small distance between the fixed contact 11 and the movable contact 21 and the magnet 40. In this example, however, the magnet 40 is housed and arranged within the magnet arrangement section 47 of the insulating casing 41, thereby achieving both magnetic proximity and thermal insulation. (Regarding casing 41)

[0027] Casing 41 can be made of various heat-resistant synthetic resins or metal materials, but in this example, it is made of a heat-resistant synthetic resin that can be mass-produced. Its shape can be changed in various ways as long as it can stably incorporate the bimetal switch described above, but in this example, it is made into a roughly box-like shape with a rectangular bottom in a plan view. Note that this can be done regardless of whether an inert gas atmosphere is present, so casing 41 can be made regardless of whether it is gas-tight.

[0028] Specifically, walls 42 extend upward from the four sides of a bottom 43 having an opening penetrating vertically. These walls 42 have heat insulating properties and can therefore be made relatively thick.

[0029] The upper end of the wall portion 42 is flat and is closed by an upper cover 51 of an appropriate shape, such as a plate-like body, and is fixed by an appropriate means, such as by screws, into cover holes 48 provided at the four corners of the wall portion 42. The bottom cover 52 in FIG. 1 is attached in a structure substantially similar to that of the upper cover 51. As shown in FIG. 3, bottom cover 52 has two protruding pieces on the left and right, and main body mounting holes 49 are formed in the protruding pieces, penetrating vertically, and are fixed to the object to be measured by appropriate means, such as by screws. [Example]

[0030] Examples are given below to aid in understanding the present invention, but the present invention should not be understood as being limited to these examples. As an example, a protector for both DC high voltage currents was created as shown in Figures 1 to 3. A ferrite magnet 40 with a resistance of approximately 130 mT was attached to a magnet placement section 47 formed approximately 5 mm away from the fixed contact 11 and the movable contact 21. A general-purpose silver-nickel binary or ternary alloy was used for the fixed contact 11 and the movable contact 21, and a bimetal 31 made of a bimetal adjusted to a reversal operating temperature of approximately 120°C and a release temperature of approximately 40°C was used, with a contact opening dimension of approximately 1.5 to 2 mm. (Electrical heating test)

[0031] The DC high voltage current protectors of both examples were fixed to a temperature-adjustable test object in a natural air environment, and a repeated ON / OFF test was conducted by raising and lowering the temperature while applying a load of 1000V 15A.The test was terminated when it was confirmed that 50,000 cycles had been achieved in all examples without any abnormalities such as the generation of flames. [Explanation of symbols]

[0032] 11: Fixed contact 12:Fixed terminal 21: Movable contact 22: Contact plate 23: Mounting fixture 27: Movable side terminal 28: Contact leg 31: Bimetal 40: Magnet 41: Casing 42:Wall part 43: Bottom 44: Opening 45 :Double part 46: Contact point 47: Magnet placement section 48: Lid hole 49: Main body mounting hole 50: Manual reset switch 51: Upper lid 52: Bottom lid

Claims

1. A bimetal switch is provided on a contact plate with a movable contact that moves toward and away from a fixed contact as the bimetal reverses its motion. This bimetal switch is arranged in a casing as a protector for DC high voltage current. a magnet is disposed around the fixed contact and the movable contact, so that sparks between the fixed contact and the movable contact are attenuated; A protector for DC high voltage current, characterized in that the magnet is arranged on at least one side along the longitudinal direction of the contact plate, across the entire vertical range of the contact opening dimension, in an area longer than the length of the movable part of the contact plate.

2. The outer dimensions of the casing are 40 x 60 x 33 mm or more, The magnet is one (48 x 22 x 10t) with a torque of 130 mT or more and is arranged on the right or left side of the contact plate, The bimetal has a circular shape in plan view with a diameter of 25 mm or more, The contact opening dimension between the fixed contact and the movable contact is 1.5 to 2 mm; 2. The DC high voltage current protector according to claim 1.

3. The DC high voltage current is 500 V or more, The magnet is a ferrite magnet with an insulation resistance of 50 to 100 MΩ and a heat resistance of 300°C or higher, 3. The DC high voltage current protector according to claim 1, wherein the fixed contact is a grounded negative terminal and the movable contact is a positive terminal.

4. a contact leg portion disposed on the lower surface of the contact plate; The contact leg extends downward to contact the bimetal when the bimetal is reversed, The bimetal is disk-shaped, and the periphery of the bimetal is supported in a retaining groove of the casing.

3. The DC high voltage current protector according to claim 1, wherein the bimetal is configured to push up the contact leg portion by one reversal movement of the bimetal, thereby obtaining the contact opening dimension.

5. 3. The DC high voltage current protector according to claim 1, wherein at least the surfaces of the fixed contact and the movable contact are made of a binary alloy or a ternary alloy.

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