Thermally protected metal oxide varistor with indicator circuit

Abstract

This relates to a thermally protected metal oxide varistor including an indicator circuit. [Solution] The thermal protection device may include a varistor body within a housing, the varistor body including a thermal electrode arranged along a first surface. The thermal protection device may further include a first terminal connected to the first surface and a second terminal connected to a second surface of the thermal electrode. The thermal protection device may further include an indicator circuit including a first pin and a second pin arranged along the first surface of the varistor body, where the second pin is connected to a slider, and a thermal event causes the slider to move between a first position and a second position, where the first pin and the second pin are separated from each other when the slider is in the second position.

Description

Technical Field

[0001] This disclosure generally relates to protecting electrical and electronic circuits and devices from power surges, and more particularly to a thermally protected metal oxide varistor including an indicator circuit.

Background Art

[0002] Overvoltage protection devices are used to protect electronic circuits and components from damage due to overvoltage fault conditions. Such overvoltage protection devices may include metal oxide varistors (MOVs) connected between the circuit to be protected and the ground wire. MOVs have specific circuit voltage characteristics that enable them to protect such circuits from destructive voltage surges. Typically, these devices utilize spring elements and link materials that can melt during abnormal conditions to form an open circuit. In particular, when a voltage greater than the nominal voltage or threshold voltage is applied to the device, current flows through the MOV, generating heat. This melts the link element. When the link melts, an open circuit is formed, thereby preventing the MOV from firing.

[0003] Thermally protected varistors are currently commercially available, but currently available thermal cut-off varistors have complex assemblies and are costly to manufacture. Another drawback of known approaches to thermally protected varistors is that they are single-use components that must be replaced when thermal cut-off occurs. Since the thermal cut-off portion is usually surrounded by a cover, it may not be easy for the maintenance personnel of the equipment to determine whether replacement is required as a result of thermal cut-off.

[0004] Therefore, there is a current need for a varistor that can be easily maintained and repaired and can be efficiently constructed to protect electrical circuits and devices vulnerable to abnormal overvoltage transitions. Improvements are provided with respect to these and other considerations. [Overview of the Initiative]

[0005] This summary is provided to introduce various concepts that will be further described in more detail later in a simplified form. This summary is not intended to clarify any important or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter.

[0006] In some embodiments, the thermal protection device may include a varistor body within a housing, the varistor body including a thermal electrode arranged along a first surface. The thermal protection device may further include a first terminal connected to the first surface and a second terminal connected to a second surface of the thermal electrode. The thermal protection device may further include an indicator circuit including a first pin and a second pin arranged along the first surface of the varistor body, where the second pin is connected to a slider, and a thermal event causes the slider to move between a first and a second position, where the first and second pins are separated from each other when the slider is in the second position.

[0007] In some embodiments, a metal oxide varistor (MOV) device may include a varistor body within a housing, the varistor body including a thermal electrode arranged along a first surface, and a first terminal connected to the first surface and a second terminal connected to a second surface of the thermal electrode. The MOV device may further include an indicator circuit including a first pin and a second pin arranged along the first surface of the varistor body, where the second pin is connected to a slider, and a thermal event causes a break between the first terminal and the thermal electrode, which causes the slider to move between a first position and a second position, where the first pin and the second pin are separated from each other when the slider is in the second position.

[0008] In some embodiments, a thermal metal oxide varistor (TMOV) device may include a varistor body within a housing, the varistor body may include a thermal electrode arranged along a first surface, and a first terminal connected to the first surface and a second terminal connected to a second surface of the thermal electrode. The TMOV may further include an indicator circuit including a first pin and a second pin arranged along the inner wall of the housing, where the second pin is connected to a slider, and a thermal event causes a break between the first terminal and the thermal electrode, which causes the slider along the inner wall to move between a first position and a second position, where the first pin and the second pin are separated from each other when the slider is in the second position. [Brief explanation of the drawing]

[0009] The attached drawings illustrate exemplary methods of disclosed embodiments devised to date for the practical application of the principle.

[0010] [Figure 1] A circuit diagram including an MOV device according to an embodiment of this disclosure is shown.

[0011] [Figure 2] This is a top perspective view of an MOV device according to an embodiment of the present disclosure.

[0012] [Figure 3] This is a cutaway diagram of an MOV device according to an embodiment of the present disclosure.

[0013] [Figure 4] This is a top perspective view of an MOV device according to an embodiment of the present disclosure.

[0014] [Figure 5] This is a top perspective view of an MOV device according to an embodiment of the present disclosure.

[0015] [Figure 6] This is a top perspective view of an MOV device according to an embodiment of the present disclosure.

[0016] [Figure 7] This is an enlarged perspective view of the terminal connection portion of the MOV device according to the embodiment of this disclosure.

[0017] [Figure 8] This is a bottom perspective view of the MOV device according to an embodiment of the present disclosure.

[0018] The drawings are not necessarily to scale. The drawings are for illustrative purposes only and are not intended to depict any particular scope of this disclosure. The drawings are intended to illustrate representative embodiments of this disclosure and should therefore not be considered as limitations on scope. Similar elements are represented in the drawings with similar numbering.

[0019] Furthermore, to clarify the explanation, certain elements may be omitted or not shown to scale in some of these figures. Sectional views may be in the form of "slice" or "myopic" sections, and certain background lines that would normally be visible in a "true" section are omitted for clarity. Additionally, for clarity, some reference numbers may be omitted in certain drawings. [Modes for carrying out the invention]

[0020] The protective devices relating to this disclosure will now be described more thoroughly below with reference to the accompanying drawings. The accompanying drawings illustrate embodiments of the system and method. However, the protective devices may be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure may be complete and sufficient, and so that the scope of the system and method may be adequately conveyed to those skilled in the art.

[0021] Referring now to FIG. 1, a thermally protected varistor (TPV) device 10 for use with an electrical circuit 2 according to an embodiment of the present disclosure will be described. The TPV device 10 may be a TMOV. The simplified electrical circuit 2 generally includes a TPV device 10, a power supply 3, and an electrical circuit or device 4 to be protected. As will be understood by those skilled in the art, during normal operation, the TPV device 10, which may be disposed in parallel between the first terminal of the power supply 3 and the electrical circuit 4 to be protected, is in a closed, i.e., conductive, position, and power is supplied from the power supply 3 to the electrical circuit 4 to be protected. As will be described later, in an overvoltage situation, the TPV device 10 opens. The electrical circuit 2 described herein is not for the purpose of limitation, but merely provides an example of a general electrical circuit for illustrative purposes.

[0022] Referring now to FIGS. 2-4, a MOV device (hereinafter "device") 100 according to an embodiment of the present disclosure will be described in more detail. The device 100 may be the same as or similar to the above-described TPV device 10. As shown, the device 100 may include a housing 102 that houses a varistor body 106, which in this embodiment has a rectangular or cuboid shape. The varistor body 106 may include a thermoelectric electrode 108 disposed along a first surface 110 and an electrode (not shown) disposed along a second surface 116. The first terminal 120 is electrically connected to the thermoelectric electrode 108, and the second terminal 122 is electrically connected to the electrode along the second surface 116 of the varistor body 106. In some embodiments, the thermoelectric electrode 108 is ceramic, silver, copper, aluminum, or a metallization layer of copper and aluminum.

[0023] The housing 102 may include a base 124 and a central portion 125, and the central portion 125 may include an inner wall 126 that extends between outer walls 127. Although not shown, the housing 102 may include an upper cover. The inner wall 126 and the outer wall 127 define an interior 128 of the housing 102. In the interior 128, a first end 130 of the first terminal 120 is disposed adjacent to the slider 132. As will be described in more detail herein, the slider 132 may be disposed in an upper / adjacent position of the inner wall 126 and may also be connected to an indicator circuit 136 including a first pin 138 and a second pin 140.

[0024] In some embodiments, the first terminal 120 may include a spring body 142 that extends beyond the slider 132, and the spring body 142 is located between a first end 130 and a second end 148 of the first terminal 120. The first end 130 of the first terminal 120 may extend through an opening 144 in the inner wall 126 and may also be connected to the thermoelectric electrode 108 by a thermal link element (e.g., solder). When the thermal link element exceeds its melting point, for example, in an overcurrent state, the spring body 142 disengages from the thermoelectric electrode 108 exposed in the opening 144, resulting in disconnection from the power source. Before being heated, the thermal link element prevents the free end 130 from separating from the thermoelectric electrode 108, and thus also prevents the slider 132 from rotating toward the opening 144. In some embodiments, the first terminal 120 may include a protrusion 150 that is operable to engage the body 152 of the slider 132.

[0025] The indicator circuit 136 is operable to indicate whether the first terminal 120 is in a conductive state with the thermal electrode 108. That is, in the first position of the slider 132, the first pin 138 and the second pin 140 are in direct physical and electrical contact with each other, as shown in Figures 2 and 3. When the slider 132 is in the second position, that is, when the slider 132 is rotated toward the opening 144, the first pin 138 and the second pin 140 are separated from each other, as shown in Figure 4. This disconnection between the first and second pins 138 and 140 results in a change in the state signal. As shown, the second pin 140 is directly coupled to the slider 132, and the first end 154 of the first pin 138 is operable to engage / disengage with the first end 158 of the second pin 140. The second end 160 of the first pin 138 and the second end 162 of the second pin 140 extend to the outside of the housing 102. In some embodiments, the second pin 140 may include a coiled portion 166 wound around a support column 170 of the housing 102, thereby causing the second pin 140 to act as a torsion spring. More specifically, the second pin 140 may include an "L-shaped" first portion connected to one of the outer walls 127, with the first end 158 extending into the body 152 of the slider 132. In this way, the second pin 140 applies force to the spring body 142 of the first terminal 120 via the slider 132.

[0026] Referring now to Figures 5 and 6, another MOV device (hereinafter referred to as "device") 200 according to the embodiments of this disclosure will be described in more detail. Device 200 may be the same as or similar to device 100 described above. For this reason, in order to keep the description brief, only specific embodiments of device 200 will be described below. As shown in the figures, device 200 may include a housing 202 that houses a varistor body 206, which may include a thermal electrode 208 arranged along a first surface and an electrode (not shown) arranged along a second surface. A first terminal 220 is electrically connected to the thermal electrode 208, and a second terminal 222 is electrically connected to the electrode along the second surface of the varistor body 206. In some embodiments, the thermal electrode 208 is a ceramic, silver, copper, aluminum, or a copper and aluminum metallization layer.

[0027] The housing 202 may include a base 224 and a central portion 225, the central portion 225 including an inner wall 226 extending between the outer walls 227. Although not shown, the housing 202 may include a top cover. The inner wall 226 and the outer walls 227 define the interior 228 of the housing 202. In the interior 228, the first end 230 of the first terminal 220 is located adjacent to the slider 232. The slider 232 may be located above / adjacent to the inner wall 226 and may be connected to an indicator circuit 236 including a first pin 238 and a second pin 240.

[0028] In some embodiments, the first terminal 220 may include a spring body 242 extending beyond the slider 232, the spring body 242 being located between a first end 230 and a second end 248 of the first terminal 220. The first end 230 of the first terminal 220 may extend through an opening 244 in the inner wall 226 and may be connected to the thermal electrode 208 by a thermal link element (e.g., solder). If the thermal link element exceeds its melting point, for example in an overcurrent condition, the spring body 242 will detach from the thermal electrode 208 exposed in the opening 244, resulting in a disconnection from the power supply. Before heating, the thermal link element prevents the free end 230 from detaching from the thermal electrode 208 and therefore also prevents the slider 232 from rotating toward the opening 244. In some embodiments, the first terminal 220 may include a projection 250 operable to engage with the body 252 of the slider 232.

[0029] The indicator circuit 236 is operable to indicate whether the thermal electrode 208 of the first terminal 220 is in a conductive state. That is, in the first position of the slider 232, the first pin 238 and the second pin 240 are in direct physical and electrical contact with each other, as shown in Figure 5. When the slider 232 is in the second position, that is, when the slider 232 is rotated toward the opening 244, the first pin 238 and the second pin 240 are separated from each other, as shown in Figure 6. This disconnection between the first and second pins 238 and 240 results in a change in the state signal. As shown, the second pin 240 is directly coupled to the slider 232, and the first end 254 of the first pin 238 is operable to engage / disengage with the first end 258 of the second pin 240. More specifically, the first end 254 of the first pin 238 may include a coiled portion 261, and when the slider 232 is in the first position, the second pin 240 is sandwiched between adjacent coil elements of the coiled portion 261. The second end 260 of the first pin 238 and the second end 262 of the second pin 240 extend outward from the housing 202. In some embodiments, the second pin 240 may include a coiled portion 266 wound around a support 270 of the housing 202, thereby causing the second pin 240 to act as a torsion spring, applying force to the spring body 242 of the first terminal 220 via the slider 232.

[0030] Figure 7 shows an example relating to a first end 330 of a first terminal 320 according to one embodiment of the present disclosure. In this embodiment, the first end 330 may include a retaining member 333 within a central opening 335. The retaining member 333 may extend toward an opening 344 of the housing 302 and may be operable to engage with the body 352 of the slider 332. The retaining member 333 may be a rib or finger that helps reduce stress from the slider 332 on the solder joint 337 and helps lift the first terminal 320 when thermal cutting occurs. The retaining member 333 may be included as part of the first terminals 120 and 220 described herein.

[0031] Figure 8 shows a rear view of an example of a device 400 according to an embodiment of the present disclosure. As shown, the varistor body 406 may include a second terminal 422 positioned along a second surface 416 of the varistor body 406. That is, the first end 480 of the second terminal 422 may extend along the electrodes of the varistor body 406, and the second end 482 of the second terminal 422 may extend outside the housing 402 of the device. Device 400 may be the same as or similar to devices 100, 200, and 300 described above.

[0032] In short, the embodiments described herein offer at least the following advantages: First, the indicator function is mechanically linked to the thermal cutter, thereby providing a reliable / accurate signal output. Second, the device is small and features a simplified microswitch / indicator design, contributing to space savings in end-user applications. Third, the fast, robust, and reliable design of the thermal cut mechanism is useful for safe handling (main circuit current interruption), for example, based on a 200kA SCCR (Short-Circuit Current Rating) test.

[0033] In this specification, elements or steps described in the singular and beginning with the word "a" or "an" should be understood not to exclude multiple elements or steps, unless such exclusion is explicitly stated. Furthermore, references to "one embodiment" in this disclosure are not intended to be construed as excluding the existence of additional embodiments that also incorporate the described features.

[0034] The terms "including," "comprising," or "having," and their variations, are used herein to encompass the items and their equivalents listed thereafter, as well as any additional items. Therefore, the terms "including," "comprising," or "having," and their variations, are open-ended expressions and are used interchangeably herein.

[0035] This disclosure is not limited in scope by the specific embodiments described herein. In fact, various other embodiments and modifications thereof will be apparent to those skilled in the art from the above description and accompanying drawings, in addition to those described herein. Accordingly, such other embodiments and modifications are intended to be included within the scope of this disclosure. Furthermore, this disclosure is described herein in the context of specific implementations in specific environments for specific purposes. Those skilled in the art will recognize that its usefulness is not limited thereto, and that this disclosure can be beneficially implemented in various environments for various purposes. Accordingly, the claims set forth below should be interpreted in light of the entirety and spirit of this disclosure as described herein.

Claims

1. A varistor body located within a housing, the varistor body having a thermal electrode positioned along a first surface; A first terminal connected to the first surface, and a second terminal connected to the second surface of the thermal electrode; and An indicator circuit having a first pin and a second pin arranged along the first surface of the varistor body, wherein the second pin is connected to a slider, and a thermal event causes the slider to move between a first position and a second position, and when the slider is in the second position, the first pin and the second pin are separated from each other. A thermal protection device equipped with the following features.

2. The thermal protection device according to claim 1, wherein the housing has an inner wall, the inner wall includes an opening, and when the slider is in the first position, the first end of the first terminal extends through the opening.

3. The thermal protection device according to claim 2, wherein the first end of the first terminal has a projection that is operable to engage with the body of the slider.

4. The thermal protection device according to claim 1, wherein the second pin is a torsion spring coupled to the outer wall of the housing.

5. The thermal protection device according to claim 1, wherein the first pin includes a first end extending into the housing, and when the slider is in the first position, the first end is in direct contact with the second pin.

6. The thermal protection device according to claim 5, wherein the first end of the first pin includes a coiled portion.

7. The thermal protection device according to claim 1, wherein the second pin includes a coiled portion wound around a support column of the housing.

8. The thermal protection device according to claim 1, wherein the first terminal has a spring body that extends beyond the slider.

9. The thermal protection device according to claim 1, wherein the first terminal is connected to the thermal electrode by a thermal link material.

10. A metal oxide varistor (MOV) device, A varistor body located within a housing, the varistor body having a thermal electrode positioned along a first surface; A first terminal connected to the first surface, and a second terminal connected to the second surface of the thermal electrode; and An indicator circuit having a first pin and a second pin arranged along the first surface of the varistor body, wherein the second pin is connected to a slider, and a thermal event causes a break between the first terminal and the thermal electrode, and the break between the first terminal and the thermal electrode causes the slider to move between a first position and a second position, and when the slider is in the second position, the first pin and the second pin are separated from each other. A MOV device equipped with [a specific feature / feature].

11. The MOV device according to claim 10, wherein the housing has an inner wall, the inner wall includes an opening, and when the slider is in the first position, the first end of the first terminal extends through the opening.

12. The MOV device according to claim 11, wherein the first end of the first terminal has a projection that is operable to engage with the body of the slider.

13. The MOV device according to claim 10, wherein the second pin is a torsion spring coupled to the outer wall of the housing.

14. The MOV device according to claim 10, wherein the first pin includes a first end extending into the housing, and when the slider is in the first position, the first end is in direct contact with the second pin.

15. The MOV device according to claim 14, wherein the first end of the first pin includes a coiled portion, and when the slider is in the first position, the second pin is located between two adjacent coil elements of the coiled portion.

16. The MOV device according to claim 10, wherein the second pin includes a coil wound around a support column of the housing.

17. The MOV device according to claim 10, wherein the first terminal has a spring body that extends beyond the slider.

18. A thermometal oxide varistor (TMOV) device, A varistor body located within a housing, the varistor body having a thermal electrode positioned along a first surface; A first terminal connected to the first surface, and a second terminal connected to the second surface of the thermal electrode; and An indicator circuit having a first pin and a second pin arranged along the inner wall of the housing, wherein the second pin is connected to a slider, and a thermal event causes a break between the first terminal and the thermal electrode, and the break between the first terminal and the thermal electrode causes the slider along the inner wall to move between a first position and a second position, and when the slider is in the second position, the first pin and the second pin are separated from each other. A TMOV device equipped with the following features.

19. The TMOV device according to claim 18, wherein the inner wall includes an opening, and when the slider is in the first position, the first end of the first terminal extends through the opening.

20. The TMOV device according to claim 18, wherein the first end of the first terminal has a projection that is operable to engage with the body of the slider.

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