Circuit board assembly of reclosing circuit breaker and reclosing circuit breaker

Abstract

The circuit board assembly comprises a power supply circuit board and a control circuit board, the power supply circuit board and the control circuit board are arranged in a stacked mode, the control circuit board is located above the power supply circuit board, and the power supply circuit board and the control circuit board are electrically connected through a connector; the power supply circuit board comprises a motor driving circuit, a power supply input circuit, a switching power supply circuit and a signal sampling circuit; the switching power supply circuit comprises a high-voltage part and a low-voltage part; from the first surface of the power supply circuit board, components of the motor driving circuit, the power supply input circuit, the high-voltage part and the low-voltage part are respectively arranged at four corners of the first surface of the power supply circuit board. From the second surface of the power supply circuit board, the components of the motor drive circuit, the power supply input circuit, the high-voltage part and the low-voltage part half surround the components of the signal sampling circuit. The method has the advantage of being more reasonable in layout.

Description

Technical Field

[0001] This application relates to the field of low-voltage switch electrical appliances, and is a reclosing circuit breaker, specifically a circuit board assembly of a reclosing circuit breaker. Background Art

[0002] In the field of molded case reclosing circuit breakers, in order to achieve functions such as automatic opening and closing of the circuit breaker, overload protection, short-circuit protection, and parameter setting of the circuit breaker, a circuit board is often required.

[0003] The existing molded case reclosing circuit breaker often only uses a single circuit board to include all the above functions. For example, the switching power supply circuit in the circuit board is used to convert the electricity on the main circuit into an appropriate voltage for other circuits of the circuit board, the motor drive circuit is used to achieve the automatic reclosing function, the protection circuit is used to achieve overload protection, short-circuit protection, etc., and the human-machine interaction circuit is used to achieve parameter setting, etc. For example, the structure disclosed in CN204102832U is exactly like this.

[0004] However, some of these circuits mentioned above belong to the strong electricity part, and some belong to the weak electricity part. For example, the working voltage of the human-machine interaction circuit, protection circuit, etc. is relatively low, while a part of the switching power supply circuit is strong electricity (because it converts the electricity on the main circuit, so there is a high-voltage part connected to the main circuit). Such a single circuit board design is not conducive to the separation of strong and weak electricity. At the same time, with the miniaturization design of the reclosing circuit breaker, the single circuit board structure is also difficult to meet the size requirements of the circuit breaker.

[0005] Therefore, how to design the circuit board assembly more reasonably is undoubtedly also a test. Summary of the Invention

[0006] In view of this, the purpose of this application is to overcome the deficiencies in the prior art, and aims to provide a circuit board assembly of a reclosing circuit breaker and a reclosing circuit breaker, which have the advantages of more reasonable structure, etc.

[0007] The present application provides: a circuit board assembly of a reclosing circuit breaker, which includes a power circuit board and a control circuit board. The power circuit board and the control circuit board are stacked, and the control circuit board is located above the power circuit board. The power circuit board and the control circuit board are electrically connected through connectors. The power circuit board includes a motor drive circuit, a power input circuit, a switching power supply circuit, and a signal sampling circuit. The switching power supply circuit includes a high-voltage part and a low-voltage part. From the first surface of the power circuit board, the components of the motor drive circuit, the power input circuit, the high-voltage part, and the low-voltage part are respectively arranged at the four corners of the first surface of the power circuit board. From the second surface of the power circuit board, the components of these four circuits, namely the motor drive circuit, the power input circuit, the high-voltage part, and the low-voltage part, semi-surround the components of the signal sampling circuit.

[0008] With this structure, the circuit structure of a single circuit board in the prior art is divided into two circuit boards, and all high-voltage circuits (the power input circuit and the high-voltage part of the switching power supply circuit) are arranged in the power circuit board. By reasonably arranging the layout of the power circuit board in this way, the separation between strong and weak electricity (high and low voltage) can be achieved as much as possible. At the same time, the motor drive circuit is arranged on the power circuit board because the power circuit board is located below the control circuit board and is closer to the electric operation part of the reclosing circuit breaker, which is convenient for wiring.

[0009] In some embodiments of the present application, the first surface is the surface of the power circuit board facing the control circuit board. From the first surface of the power circuit board, the components of the low-voltage part are located in the first direction of the components of the motor drive circuit, the components of the high-voltage part are located in the diagonal direction of the components of the motor drive circuit, and the components of the power input circuit are located in the second direction of the components of the motor drive circuit. The first direction and the second direction are perpendicular to each other.

[0010] With this structure, the layout of the components on the power circuit board is more reasonable, and the separation between strong and weak electricity (high and low voltage) can be achieved more effectively.

[0011] In some embodiments of the present application, from the first surface of the power circuit board; the components of the motor drive circuit include a relay and a safety capacitor, the components of the power input circuit include four current-limiting resistors and three varistors, the components of the low-voltage part include three first electrolytic capacitors, the components of the high-voltage part include a power chip U3, a transformer, and two second electrolytic capacitors. The connector for the power circuit board to cooperate with the control circuit board is a first connector, and the first connector is located near the three first electrolytic capacitors.

[0012] With this structure, it doesn't specifically mean that these circuits only have these components. It emphasizes the layout of these components because these components have the largest volume, and the reasonable arrangement of these components will determine the overall structural arrangement of the power supply circuit board.

[0013] In some embodiments of the present application, the signal sampling circuit includes a voltage sampling module and a zero-break detection module; from the second surface of the power supply circuit board, the components of the voltage sampling module use first patch resistors; the components of the zero-break detection module use a patch diode, a second patch resistor, a third patch resistor, a patch capacitor, and an opto-isolator.

[0014] With this structure, since the signal sampling circuit basically uses the method of patch components, the signal sampling circuit will occupy a smaller space. Therefore, it can be arranged on the second surface of the power supply circuit board and is semi-surrounded by the components of the motor drive circuit, the power input circuit, the high-voltage part, and the low-voltage part.

[0015] In some embodiments of the present application, the control circuit board includes a human-machine interaction circuit. The components of the human-machine interaction circuit include a display screen and operation keys. The display screen and operation keys are located on the surface of the control circuit board away from the power supply circuit board, and the position where the display screen is located is directly above the power supply circuit board; a second connector is provided on the surface of the control circuit board adjacent to the power supply circuit board, and the first connector and the second connector are connected by pin headers.

[0016] With this structure, the human-machine interaction circuit of the control circuit board adopts this layout method, and the structure will be more reasonable.

[0017] A reclosing circuit breaker includes a middle cover and a top cover. An accommodation cavity is provided on the middle cover, and the top cover is fixed to the middle cover to close the opening of the accommodation cavity; wherein, a circuit board assembly of the above-mentioned reclosing circuit breaker is arranged in the accommodation cavity; the accommodation cavity includes a first side wall, a second side wall, and a third side wall. The first side wall and the second side wall are arranged in parallel, and the third side wall connects the first side wall and the second side wall; the control circuit board is arranged against the third side wall, a part of the first side wall, and a part of the second side wall.

[0018] With this structure, the circuit board assemblies stacked in this way are more suitable for this small-sized reclosing circuit breaker.

[0019] In some embodiments of the present application, a communication interface is further provided on the control circuit board, a notch is provided on the second side wall, and the communication interface is exposed through the notch.

[0020] The design of the notch will be beneficial to the setting of the communication interface, facilitating communication between an external host computer, a PC, a mobile terminal, etc. and the control circuit board.

[0021] In some embodiments of the present application, a fourth sidewall is further included; the fourth sidewall connects the first sidewall and the second sidewall, and the fourth sidewall and the third sidewall are spaced apart; the distance between the fourth sidewall and the third sidewall is D, the size of the control circuit board in the first direction is d1, and the size of the power supply circuit board in the first direction is d2, and both d1 and d2 are not greater than 0.5D.

[0022] With such a structure and such dimensional design, the overall structure is more compact.

[0023] In some embodiments of the present application, the distance between the first sidewall and the second sidewall is d, and D is greater than d.

[0024] With such a structure and such dimensional design, the structure of the reclosing circuit breaker will be more compact.

[0025] In some embodiments of the present application, the control circuit board has an avoidance groove, and the avoidance groove is located at one end of the control circuit board close to the second sidewall and far from the third sidewall.

[0026] With such a structure, the design of the avoidance groove will be beneficial to the arrangement of the remaining components of the reclosing circuit breaker, such as reserving space for the electric operating structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Shows a perspective view of the reclosing circuit breaker according to an embodiment of the present application;

[0029] Figure 2 Shows a perspective view of the reclosing circuit breaker without the top cover according to an embodiment of the present application;

[0030] Figure 3 Shows a schematic structural view of the circuit board assembly in the reclosing circuit breaker according to an embodiment of the present application;

[0031] Figure 4 Shows a front view of the control circuit board in the reclosing circuit breaker according to an embodiment of the present application;

[0032] Figure 5 Shows a front view of the power supply circuit board in the reclosing circuit breaker according to an embodiment of the present application;

[0033] Figure 6Shows the rear view of the power supply circuit board in the reclosing circuit breaker according to the embodiment of the present application;

[0034] Figure 7 Shows the circuit schematic diagrams of the power input circuit and the switching power supply circuit in the power supply circuit board according to the embodiment of the present application;

[0035] Figure 8 Shows the circuit schematic diagram of the motor drive circuit in the power supply circuit board according to the embodiment of the present application;

[0036] Figure 9 Shows the circuit schematic diagram of the zero-break detection module in the power supply circuit board according to the embodiment of the present application;

[0037] Figure 10 Shows the circuit schematic diagram of the voltage sampling module in the power supply circuit board according to the embodiment of the present application;

[0038] Figure 11 Shows the schematic diagram of the control chip in the circuit board assembly according to the embodiment of the present application;

[0039] Figure 12 Shows the principle block diagram of the line control circuit board according to the embodiment of the present application. Detailed implementation manners

[0040] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for explaining the present application and should not be construed as limiting the present application.

[0041] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.

[0042] In addition, the terms "primary", "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "primary", "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0043] In this application, unless otherwise clearly specified and defined, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0044] In this application, unless otherwise clearly specified and defined, the main feature being "on" or "under" the second feature can be that the main and the second features are in direct contact, or the main and the second features are in indirect contact through an intermediate medium. Moreover, the main feature being "above", "over" and "on top of" the second feature can be that the main feature is directly above or obliquely above the second feature, or merely indicates that the main feature has a higher horizontal height than the second feature. The main feature being "under", "beneath" and "underneath" the second feature can be that the main feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the main feature is less than that of the second feature. Embodiment

[0045] As Figures 1 - 12 shown, a reclosing circuit breaker includes a middle cover 100 and a top cover 200.

[0046] An accommodation cavity 100a is formed on the middle cover 100. The accommodation cavity 100a is surrounded by four side walls, namely a first side wall 101, a second side wall 102, a third side wall 103 and a fourth side wall 104. The third side wall 103 and the fourth side wall 104 connect the first side wall 101 and the second side wall 102. The distance between the fourth side wall 104 and the third side wall 103 is D, and the distance between the first side wall 101 and the second side wall 102 is d, and D is greater than d.

[0047] The top cover 200 is fixed to the middle cover 100, and here screw fastening can be adopted. Of course, in addition to this, fastening can also be carried out by means of rivets or buckles, etc. The function of the top cover 200 is to close the opening of the accommodation cavity 100a to protect the internal components (circuit board, electric operation part).

[0048] A circuit board assembly of the reclosing circuit breaker is arranged in the accommodation cavity 100a. The circuit board assembly of the reclosing circuit breaker here includes a control circuit board 300 and a power supply circuit board 400. The control circuit board 300 and the power supply circuit board 400 are arranged in a stacked manner, and the control circuit board 300 is located above the power supply circuit board 400. The control circuit board 300 is arranged close to a part of the third side wall 103, a part of the first side wall 101 and a part of the second side wall 102.

[0049] Here, the control circuit board 300 is provided with a communication interface 301, which is 485 communication here. Of course, other wired communication methods can also be adopted, such as modbus, etc. A notch 1021 is opened on the second side wall 102, and the communication interface 301 is exposed through the notch 1021.

[0050] Here, the size of the control circuit board 300 in the first direction F1 is d1, and the size of the power supply circuit board 400 in the first direction F1 is d2. Both d1 and d2 are not greater than 0.5D, and here both d1 and d2 are approximately 0.5D.

[0051] Since this application does not improve the circuit of the reclosing circuit breaker itself, but arranges the electronic components of each circuit component more reasonably to adapt to a more compact reclosing circuit breaker. Therefore, only the relevant drawings are attached to the circuit principle part, and its circuit principle will not be described in detail. The focus will be on the introduction of the component settings.

[0052] The power supply circuit board 400 and the control circuit board 300 are electrically connected through connectors. Specifically, a first connector 401 is provided on the power supply circuit board 400, and a second connector 302 is provided on the control circuit board 300. The first connector 401 and the second connector 302 are electrically connected by a pin header 500.

[0053] The power supply circuit board 400 includes a motor drive circuit 410, a power input circuit 420, a switching power supply circuit 430, and a signal sampling circuit 440.

[0054] The switching power supply circuit 430 here includes a high-voltage part 430a and a low-voltage part 430b. The high-voltage part 430a and the low-voltage part 430b here are in a relative relationship. Since the switching power supply circuit rectifies the voltage of the three-phase power supply circuit board and then converts it into low voltage through a transformer 432 for components such as the protection circuit 310 and the control chip to work. Therefore, the high-voltage part 430a is located on the primary side of the transformer 432, and a part of the low-voltage part 430b is located on the secondary side of the transformer 432. In this embodiment, the low-voltage part 430b has two paths, one path outputs 12v, and the other path outputs 3.3v. Of course, since the circuit itself is the prior art in this field, the specific circuit can be referred to Figure 7 , and the circuit will not be described in detail here.

[0055] Viewed from the first surface S1 of the power supply circuit board 400 (i.e., the surface facing the control circuit board 300), the components of the motor drive circuit 410, the power input circuit 420, the high-voltage part 430a, and the low-voltage part 430b are arranged at the four corners of the first surface S1 of the power supply circuit board 400. Specifically, viewed from the first surface S1 of the power supply circuit board 400, the components of the low-voltage part 430b are located in the first direction F1 of the components of the motor drive circuit 410, the components of the high-voltage part 430a are located in the diagonal direction of the components of the motor drive circuit 410, the components of the power input circuit 420 are located in the second direction F2 of the components of the motor drive circuit 410, and the first direction F1 and the second direction F2 are perpendicular to each other. Here, viewed from the first surface S1 of the power supply circuit board 400, the components of the motor drive circuit 410 include a relay 411 and a safety capacitor 412, the components of the power input circuit 420 include four current-limiting resistors 421 (R3, R5, R6, and R8 in the circuit diagram) and three varistors 422 (RV1, RV2, and RV3 in the circuit diagram), the components of the low-voltage part 430b include three first electrolytic capacitors 431 (EC2, EC3, and EC5 in the circuit diagram), the components of the high-voltage part 430a include a power supply chip U3, a transformer 432 (EE16 in the circuit diagram), and two second electrolytic capacitors 433 (EC1 in the circuit diagram and EC4 in the circuit diagram), and the first connector 401 is located near the three first electrolytic capacitors 431. Of course, the above does not mean that only these components are included on the power supply circuit board 400, but the volumes of these components are relatively large, and their reasonable arrangement determines the specific structure of the power supply circuit board 400. Since the volumes of the remaining components of these circuits are very small and some are surface-mounted components, as long as these components with larger volumes are reasonably arranged, the remaining components only need to be filled correspondingly, and the arrangement of the remaining components will not be introduced in detail here.

[0056] Viewed from the second surface S2 of the power supply circuit board 400, the components of the four circuits of the motor drive circuit 410, the power input circuit 420, the high-voltage part 430a, and the low-voltage part 430b semi-surround the components of the signal sampling circuit 440. Since the components of the four circuits of the motor drive circuit 410, the power input circuit 420, the high-voltage part 430a, and the low-voltage part 430b on the second surface of the power supply circuit board 400 are basically electronic components with small volumes, the signal sampling circuit 440 can be arranged among these four circuits and semi-surrounded by the components of these four circuits.

[0057] Here, the signal sampling circuit 440 includes a voltage sampling module and a zero-break detection module. Viewed from the second surface of the power supply circuit board 400, the components of the voltage sampling module use first surface-mounted resistors (the specific components involved are asFigure 10 as shown). The components of the zero-break detection module are a surface-mount diode, a second surface-mount resistor, a third surface-mount resistor, a surface-mount capacitor, and an opto-isolator (the specific components involved are as Figure 9 shown). Since the signal sampling circuit 440 basically uses surface-mount components, it only needs to be arranged on the second surface of the power supply circuit board 400 and is located among the components of the motor drive circuit, the power input circuit 420, the high-voltage part 430a, and the low-voltage part 430b, and is semi-surrounded by them.

[0058] With this structure, since the signal sampling circuit 440 basically uses surface-mount components, the signal sampling circuit 440 will occupy a smaller space. Therefore, it can be arranged on the second surface of the power supply circuit board 400 and is semi-surrounded by the components of the motor drive circuit 410, the power input circuit 420, the high-voltage part 430a, and the low-voltage part 430b.

[0059] For the circuit board assembly, the most core is the design of the power supply circuit board 400, and the control circuit board 300 is relatively easier. The control circuit board 300 has a protection circuit 310. Of course, the protection circuit 310 here includes open-phase protection, leakage protection, short-circuit protection, and overload protection. The specific circuits of these protection functions are well-known common knowledge in the art and will not be elaborated here. For example, as mentioned above, the signal sampled by the signal sampling circuit 440 is fed back to these protection circuits 310 to determine whether there are abnormalities (such as open-phase, leakage, short-circuit, and overload) in the circuit.

[0060] The control circuit board 300 also has a human-machine interaction circuit 320. The components of the human-machine interaction circuit 320 include a display screen 311 and operation keys 322. Here, the operation keys 322 are operation buttons, and the number is 7. The display screen 311 and the operation keys 322 are located on the surface of the control circuit board 300 away from the power supply circuit board 400, and the position where the display screen 311 is located is directly above the power supply circuit board 400. Of course, it is not specifically stated here that the human-machine interaction circuit 320 only has the display screen 311 and the operation keys 322. It also includes other components. For the other components, they are conventional technical means in the art and will not be elaborated here.

[0061] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0062] Although the embodiments of this application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting this application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A circuit board assembly for a reclosing circuit breaker, characterized in that: It includes a power circuit board and a control circuit board, which are stacked and arranged with the control circuit board located above the power circuit board, and are electrically connected to the control circuit board via connectors; the power circuit board includes a motor drive circuit, a power input circuit, a switch power circuit and a signal sampling circuit; the switch power circuit includes a high voltage part and a low voltage part; from the first surface of the power circuit board, the components of the motor drive circuit, the power input circuit, the high voltage part and the low voltage part are arranged at the four corners of the first surface of the power circuit board; from the second surface of the power circuit board, the components of the four circuits, namely, the motor drive circuit, the power input circuit, the high voltage part and the low voltage part, half surround the components of the signal sampling circuit.

2. The circuit board assembly of a reclosing circuit breaker according to claim 1, characterized in that: The first surface is the surface of the power circuit board facing the control circuit board; from the first surface of the power circuit board, the components of the low-voltage part are located in the first direction of the components of the motor drive circuit, the components of the high-voltage part are located in the diagonal direction of the components of the motor drive circuit, and the components of the power input circuit are located in the second direction of the components of the motor drive circuit, and the first direction is perpendicular to the second direction.

3. A circuit board assembly for a reclosing circuit breaker according to claim 2, characterized in that: From the first surface of the power circuit board; the components of the motor drive circuit include relays and safety capacitors, the components of the power input circuit include four current limiting resistors and three varistors, the components of the low-voltage part include three first electrolytic capacitors, and the components of the high-voltage part include a power chip U3, a transformer and two second electrolytic capacitors; the connector used by the power circuit board to cooperate with the control circuit board is the first connector, and the first connector is located near the three first electrolytic capacitors.

4. A circuit board assembly for a reclosing circuit breaker according to claim 2, characterized in that: The signal sampling circuit includes a voltage sampling module and a zero-break detection module; from the second surface of the power circuit board, the components of the voltage sampling module are a first chip resistor; the components of the zero-break detection module are a chip diode, a second chip resistor, a third chip resistor, a chip capacitor and an optocoupler isolator.

5. The circuit board assembly of a reclosing circuit breaker according to claim 3, characterized in that: The control circuit board includes a human-computer interaction circuit, and the components of the human-computer interaction circuit include a display screen and operation keys. The display screen and the operation keys are located on the surface of the control circuit board away from the power circuit board, and the display screen is located directly above the power circuit board; a second connector is provided on the surface of the control circuit board adjacent to the power circuit board, and the first connector is connected to the second connector through a pin header.

6. A reclosing circuit breaker, comprising a middle cover and a top cover, wherein the middle cover is provided with a receiving cavity, and the top cover and the middle cover are fixed to close the opening of the receiving cavity; characterized in that: A circuit board assembly of a reclosing circuit breaker as described in any one of claims 1 to 5 is arranged in the accommodating chamber; the accommodating chamber includes a first side wall, a second side wall and a third side wall, the first side wall and the second side wall are arranged in parallel, and the third side wall connects the first side wall and the second side wall; the control circuit board is arranged against the third side wall, a part of the first side wall and a part of the second side wall.

7. A reclosing circuit breaker according to claim 6, characterized in that: The control circuit board is also provided with a communication interface, and a notch is provided on the second side wall, through which the communication interface is exposed.

8. A reclosing circuit breaker according to claim 6, characterized in that: It also includes a fourth side wall; the fourth side wall connects the first side wall and the second side wall, and the fourth side wall and the third side wall are spaced apart; the distance between the fourth side wall and the third side wall is D, the size of the control circuit board in the first direction is d1, and the size of the power circuit board in the first direction is d2, and both d1 and d2 are not greater than 0.5D.

9. A reclosing circuit breaker according to claim 8, characterized in that: The distance between the first side wall and the second side wall is d, and D is greater than d.

10. A reclosing circuit breaker according to claim 6, characterized in that: The control circuit board has an avoidance groove, and the avoidance groove is located at one end of the control circuit board close to the second side wall and away from the third side wall.

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