Three-phase thermal protector

Abstract

The invention relates to the technical field of thermal protectors, and discloses a three-phase thermal protector which comprises a shell, a cover plate and a switching mechanism, a first fixed contact and a second fixed contact are fixedly mounted on the cover plate, and the switching mechanism comprises a movable contact piece, a bimetallic strip and an elastic piece; the movable contact piece can abut against the first fixed contact and the second fixed contact at the same time, two phases of windings of the three-phase motor are electrically connected with the movable contact piece through the first fixed contact and the second fixed contact respectively, and the other phase of windings of the three-phase motor are electrically connected with the movable contact piece through the shell and the elastic piece, so that the three phases of windings of the three-phase motor are connected with one another in a star shape through the movable contact piece. According to the invention, when the extension lengths of the first fixed contact and the second fixed contact are different, it can be ensured that the movable contact piece is in effective contact with the first fixed contact and the second fixed contact at the same time, so that a three-phase winding can be in reliable star connection through the movable contact piece when a three-phase motor operates normally; and thus, the three-phase motor can be prevented from running in an open-phase manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protectors, and in particular relates to a three-phase thermal protector. Background Art

[0002] A thermal protector, also known as a temperature switch or thermostat, is an electrical safety device that monitors temperature changes to disconnect or restore circuits. It automatically disconnects the circuit when the temperature exceeds a set threshold, preventing damage or fire caused by overheating. When using a thermal protector in a three-phase circuit, a single-phase thermal protector is typically connected to two or each phase of the circuit. However, in practice, it is difficult to ensure that all thermal protectors activate simultaneously. If these devices do not activate simultaneously, there is a risk of secondary damage to motors or other equipment due to missing phases.

[0003] In the prior art, there are three-phase thermal protectors for overheating protection of three-phase motors, such as the "Temperaturabhängiger Schalter mit Stromübertragungsglied" (temperature-dependent switch with current transmission element) disclosed in German Patent Publication No. DE102011101862B4. The temperature-dependent switch includes a switching mechanism having a spring snap-action disk and a bimetallic chuck, a housing accommodating the switching mechanism and having a lower portion and an upper portion, with three fixed contacts provided on the upper portion. The spring snap-action disk and the bimetallic chuck are rivet-pierced through at a central position and mounted on a contact plate. The temperature-dependent switch is connected to the neutral point of a three-phase circuit for simultaneously switching the three phases R, S, and T of the three-phase circuit. The spring chuck and the bimetallic chuck press the contact plate against the three fixed contacts. The three fixed contacts are electrically connected to each other via the contact surfaces of the contact plate. When the temperature-dependent switch is closed, the three phases R, S, and T of the three-phase circuit are connected to each other via the contact plate. When the internal temperature of the three-phase motor exceeds the response temperature of the bimetallic chuck due to overload, stall or internal fault, the bimetallic chuck flips due to heat and drives the contact plate away from the three fixed contacts, so that the three phases R, S, and T of the three-phase circuit are simultaneously cut off.

[0004] However, in the existing three-phase thermal protector of the temperature-related switch described above, the three fixed contacts are fixedly mounted on the upper portion of the housing, and the upper portion of the housing is fixedly mounted on the lower portion of the housing. This means that the extension lengths of the three fixed contacts on the side of the upper portion of the housing toward the contact plate are fixed after installation. In actual applications, due to defects in the manufacturing process or assembly precision, it is difficult to ensure that the extension lengths of the three fixed contacts after being assembled to the upper portion of the housing remain consistent, which means that there will be slight differences in the extension lengths of the three fixed contacts. In addition, during use of the three-phase thermal protector, the surface of the fixed contacts will undergo electrical wear due to the impact of current and ablation, making the surface of the fixed contacts uneven and even causing the length of the fixed contacts to shorten. The difference in electrical wear between the three fixed contacts will cause differences in the degree of length loss of the three fixed contacts, which will also cause slight differences in the extension lengths of the three fixed contacts.

[0005] As a result, if there are slight differences in the extension lengths of the three fixed contacts, during the closing process of the three-phase thermal protector's switch mechanism, the contact plate, pushed by the spring snap-action disk and bimetallic chuck until it contacts the two longer fixed contacts, runs the risk of stopping and becoming difficult to push until it contacts the shortest fixed contact. This makes it difficult to ensure that the contact plate and all three fixed contacts maintain effective contact simultaneously when the switch needs to be closed. Therefore, existing three-phase thermal protectors, when the extension lengths of the three fixed contacts differ, have difficulty ensuring stable and effective contact between the three fixed contacts and the contact plate during normal motor operation. This poses a risk of the three-phase motor operating in a phase-missing state, which can easily lead to motor overheating, reduced efficiency, or even burning. Summary of the Invention

[0006] In order to solve or partially solve the problems existing in the related art, the present application provides a three-phase thermal protector. The three-phase thermal protector can ensure that the moving contact piece always maintains stable and effective contact with the first fixed contact and the second fixed contact when there is a difference in the extension length of the first fixed contact and the second fixed contact, so as to ensure that the three-phase winding of the three-phase motor can maintain a reliable star connection through the moving contact piece during normal operation, thereby avoiding the situation where the three-phase motor operates in a single-phase state.

[0007] The present application provides a three-phase thermal protector, comprising a housing, a cover plate, and a switch mechanism. The housing is a cup-shaped structure with a hollow interior. The cover plate is fixedly installed in the housing. The switch mechanism is arranged in a cavity between the cover plate and the bottom of the housing. The cover plate is an insulator, and a first fixed contact and a second fixed contact are fixedly mounted on the cover plate. Both ends of the first fixed contact and the second fixed contact pass through and extend out of the inner and outer sides of the cover plate. The housing is conductive, and the switch mechanism includes a movable contact, a bimetallic strip and a spring installed in sequence on the side of the movable contact facing away from the cover plate via a shaft pin, the movable contact and the spring being conductively connected, and the spring being conductively connected to the housing, and the bimetallic strip driving the movable contact and the first and second fixed contacts to simultaneously close or open according to temperature conditions; Among them, when the response temperature of the bimetallic strip is below the temperature, the moving contact piece is always in contact with the first fixed contact and the second fixed contact at the same time, and two phase windings of the three-phase motor are electrically connected to the moving contact piece by the first lead and the second lead through the first fixed contact and the second fixed contact respectively, and the other phase winding of the three-phase motor is electrically connected to the moving contact piece by the third lead through the housing and the spring piece, so that the three phase windings of the three-phase motor are connected to each other in a star shape through the moving contact piece.

[0008] In an optional solution, the first fixed contact and the second fixed contact are located on the outside of the cover plate and are respectively connected to a welding piece for connecting the first lead and the second lead, and the welding piece includes a fixing plate, a connecting plate, and a positioning plate; The first fixed contact and the second fixed contact are rivet structures. The first fixed contact and the second fixed contact are formed by riveting to fix the corresponding fixed plate to the outer end of the cover plate and are conductively connected to the corresponding fixed plate. The connecting plate is constructed outside the fixing plate and extends outwards. The positioning plates are constructed on both sides of the outer end of the connecting plate. The two positioning plates and the connecting plate enclose a wire clamping groove with three closed sides and one open side.

[0009] In an optional solution, a protrusion is configured on the connecting plate at a position within the wire clamping groove.

[0010] In an optional solution, a process notch is provided on the connecting plate to facilitate bending the connecting plate. The process notch is located between the fixing plate and the positioning plate and is arranged parallel to the cover plate.

[0011] In an optional solution, the welding wire sheet is formed as an integral structure, the connecting plate is arranged perpendicular to the fixing plate, and the positioning plate is arranged perpendicular to the connecting plate; The outer end surface of the connecting plate extends outward and protrudes from the outer end surface of the positioning plate.

[0012] In an optional solution, a stopper protruding from an end surface of the cover is configured on the cover, and the first fixed contact and the second fixed contact are symmetrically arranged on both sides of the stopper.

[0013] In an optional solution, a first step is constructed on the circumference of the inner wall of the shell, a support ring is embedded in the inside of the shell through the first step, the cover plate is placed on the top of the support ring, and the opening at the outer end of the shell is folded inward to form a folded portion, and the cover plate is fixed on the shell by wrapping its top outer edge with the folded portion.

[0014] In an optional scheme, the shaft pin is riveted and fixed on the moving contact piece, and a first shoulder is constructed at the end of the shaft pin facing away from the cover plate, and a through hole is constructed in the center of the spring piece. The spring piece is sleeved on the first shoulder of the shaft pin through the through hole, and the inner side of the spring piece always maintains contact with the moving contact piece so as to be conductively connected to the moving contact piece. A second step is also constructed on the circumference of the inner wall of the shell, and the outer edge of the spring piece is inserted between the second step and the support ring, and the outer edge of the spring piece always maintains contact with the second step so as to be conductively connected to the shell.

[0015] In an optional solution, a second shoulder is further configured on the shaft pin at a position adjacent to the first shoulder, a through hole is configured in the center of the bimetallic strip, and the bimetallic strip is movably sleeved on the second shoulder of the shaft pin through the through hole; When the temperature is below the response temperature of the bimetallic strip, the spring presses the movable contact piece by its own elastic force until it is in constant contact with the first fixed contact and the second fixed contact at the same time. The bimetallic strip flips over when the temperature exceeds the response temperature, so as to overcome the elastic force of the spring and drive the movable contact to separate from the first fixed contact and the second fixed contact at the same time.

[0016] In an optional solution, the surfaces of the housing, the moving contact piece, and the spring are plated with silver.

[0017] Beneficial effects of this application: The present application fixes the first fixed contact and the second fixed contact on the cover plate, and makes the movable contact piece in the switch mechanism conductively connected to the spring piece, and the spring piece conductively connected to the housing, so that two phase windings of the three-phase motor are electrically connected to the movable contact piece by leads through the first fixed contact and the second fixed contact respectively, and the other phase winding of the three-phase motor is electrically connected to the movable contact piece by leads through the housing and the spring piece, so that the movable contact piece only needs to contact the two fixed contacts to connect the three phases of the three-phase motor to each other in a star shape. When the first fixed contact and the second fixed contact are defective due to manufacturing process or assembly accuracy, Or when there are differences in the extension lengths due to different degrees of electrical wear caused by the impact of current and ablation, the moving contact piece can also contact the first fixed contact and the second fixed contact of different extension lengths at the same time in a slightly tilted state, eliminating the influence of the slight inconsistency in the extension lengths of the two fixed contacts on the contact effect with the moving contact piece, and can ensure that the moving contact piece always maintains stable and effective contact with the first fixed contact and the second fixed contact at the same time, so as to ensure that the three-phase winding of the three-phase motor can maintain a reliable star connection through the moving contact piece during normal operation, thereby avoiding the situation of phase loss operation of the three-phase motor.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a cross-sectional schematic diagram of a switch mechanism, a first fixed contact, and a second fixed contact of a three-phase thermal protector in one embodiment of the present application when closed; Figure 2 This is a cross-sectional schematic diagram of a three-phase thermal protector in an embodiment of the present application when the switch mechanism is disconnected from the first fixed contact and the second fixed contact; Figure 3 This is a schematic top view of a three-phase thermal protector in one embodiment of the present application; Figure 4 This is a schematic diagram of the structure and installation position of the welding wire piece of the three-phase thermal protector in one embodiment of the present application; Figure 5 This is a circuit diagram of a three-phase thermal protector connected to a three-phase motor in one embodiment of the present application.

[0021] Reference numerals in the figures: 1-housing, 11-first step, 12-folding portion, 13-second step, 14-connecting piece; 2-cover plate; 3-switch mechanism, 31-moving contact piece, 32-axis pin, 321-first shoulder, 322-second shoulder, 33-bimetallic sheet, 34-spring; 4-first fixed contact; 5-second fixed contact; 61-first lead, 62-second lead, 63-third lead; 7-welding piece, 70-cable slot, 71-fixing plate, 72-connecting plate, 721-process notch, 73-positioning plate, 74-bump; 8-support ring; definition Figure 5 The switch symbol A in the figure represents the circuit on-off relationship between the first fixed contact and the movable contact piece, and the switch symbol B represents the circuit on-off relationship between the second fixed contact and the movable contact piece. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application and not all embodiments. All other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention 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 therefore should not be understood as limiting the present invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0025] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0027] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0028] In the prior art, a three-phase thermal protector adopts a structure in which three fixed contacts installed on the upper part of the shell are in contact with the contact plate at the same time. The three fixed contacts may have different extension lengths due to defects in the manufacturing process or assembly accuracy, as well as electrical wear caused by the impact and ablation of the current. It is difficult to ensure that the three fixed contacts are always in stable and effective contact with the contact plate during normal operation of the motor, and there is a hidden danger of the three-phase motor running in a single phase.

[0029] In response to the above problems, the present application makes improvements and innovations and proposes the following embodiments.

[0030] In one embodiment, see Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 The present application provides a three-phase thermal protector, including a shell 1, a cover plate 2, and a switch mechanism 3. The shell 1 is a cup-shaped structure with a hollow interior. The cover plate 2 is fixedly installed in the shell 1, and the switch mechanism 3 is arranged in a cavity between the cover plate 2 and the bottom of the shell 1.

[0031] The cover plate 2 is an insulator, and a first fixed contact 4 and a second fixed contact 5 are fixedly mounted on the cover plate 2. Both ends of the first fixed contact 4 and the second fixed contact 5 pass through and extend out of the inner and outer sides of the cover plate 2; wherein, a first step 11 is constructed on the circumference of the inner wall of the shell 1, and a support ring 8 is embedded in the interior of the shell 1 through the first step 11. The cover plate 2 is placed on the top of the support ring 8, and the opening at the outer end of the shell 1 is folded inward to form a folded portion 12. The cover plate 2 is fixed to the shell 1 by wrapping its top outer edge with the folded portion 12. In this way, the cover plate 2 is kept fixed inside the shell 1 by the supporting effect of the support ring 8 and the pressing effect of the folded portion 12, so that the first fixed contact 4 and the second fixed contact 5 are fixedly mounted through the cover plate 2.

[0032] The housing 1 is conductive, and the switch mechanism 3 includes a movable contact 31, and a bimetallic strip 33 and a spring 34, which are sequentially installed through a shaft pin 32 on the side of the movable contact 31 facing away from the cover plate 2. The movable contact 31 and the spring 34 are conductively connected, and the spring 34 is conductively connected to the housing 1. The bimetallic strip 33 can drive the movable contact 31 and the first fixed contact 4 and the second fixed contact 5 to close or open simultaneously according to temperature conditions.

[0033] In this embodiment, in the switch mechanism 3, the shaft pin 32 is riveted and fixed on the moving contact piece 31, and a first shoulder 321 is constructed at the end of the shaft pin 32 facing away from the cover plate 2. A through hole is constructed in the center of the spring piece 34, and the spring piece 34 is sleeved on the first shoulder 321 of the shaft pin 32 through the through hole. The spring piece 34 is pressed against the moving contact piece 31 under the mechanical holding force of its own elastic force, so that the inner side of the spring piece 34 always maintains contact with the moving contact piece 31 to be conductively connected to the moving contact piece 31. A second step 13 is also constructed on the circumferential direction of the inner wall of the housing 1, and the outer edge of the spring piece 34 is inserted between the second step 13 and the support ring 8, and the outer edge of the spring piece 34 always maintains contact with the second step 13 to be conductively connected to the housing 1. In this way, the movable contact piece 31 and the spring piece 34 can be conductively connected, and the spring piece 34 and the housing 1 can be conductively connected. When the response temperature of the bimetallic strip 33 is below the response temperature, the spring piece 34 is in a state where the outer edge is slightly bent downward, so that the spring piece 34 presses the movable contact piece 31 under the action of its own elastic force until it is always in contact with the first fixed contact 4 and the second fixed contact 5 at the same time.

[0034] A second shoulder 322 is also formed on the shaft pin 32 near the first shoulder 321. A through-hole is formed in the center of the bimetallic strip 33, through which the bimetallic strip 33 is movably mounted on the second shoulder 322 of the shaft pin 32. When the bimetallic strip 33's response temperature is below, the spring 34, through its own elastic mechanical retaining force, presses the movable contact 31 against the first and second fixed contacts 4, 5, thereby maintaining electrical connection between the movable contact 31 and the first and second fixed contacts 4, 5. When the bimetallic strip 33's response temperature is above, it flips to overcome the elastic force of the spring 34 and simultaneously separate the movable contact 31 from the first and second fixed contacts 4, 5, thereby simultaneously disconnecting the movable contact 31 from the first and second fixed contacts 4, 5.

[0035] like Figure 5 As shown, the definition Figure 5The switch symbol A in the figure represents the circuit on-off relationship between the first fixed contact 4 and the movable contact piece 31, and the switch symbol B represents the circuit on-off relationship between the second fixed contact 5 and the movable contact piece 31. The three-phase thermal protector is installed inside the motor and connected to the neutral point of the three-phase winding to provide overheat protection for the three-phase motor. Specifically, the movable contact piece 31 abuts the first fixed contact 4 and the second fixed contact 5 at the same time, so that the V-phase winding of the three-phase motor is electrically connected to the movable contact piece 31 via the first lead 61 through the first fixed contact 4, the W-phase winding is electrically connected to the movable contact piece 31 via the second fixed contact 5, and the U-phase winding is electrically connected to the movable contact piece 31 via the third lead 63 through the housing 1 and the spring 34, thereby connecting the U, V, and W phase windings of the three-phase motor to each other in a star shape via the movable contact piece 31. Since the housing 1 is conductive, the third lead 63 connected to the U-phase winding can be connected to any position on the outer surface of the housing 1.

[0036] This application Figure 5 Only one connection method of the U, V, and W three-phase windings of the three-phase motor is shown. In a specific application, any phase of the U, V, and W three-phase windings of the three-phase motor can be connected to the housing 1, as long as the other two phases are respectively connected to the first fixed contact 4 and the second fixed contact 5 to meet the star connection method.

[0037] When the three-phase motor operates normally, the internal temperature of the motor is lower than the response temperature of the bimetallic strip 33. At this time, the movable contact 31 is always in contact with the first fixed contact 4 and the second fixed contact 5 at the same time under the pressure of the bimetallic strip 33 and the spring 34. Figure 1 、 Figure 3 As shown, the U, V, and W three-phase windings of the three-phase motor are connected to each other in a star shape through the moving contact piece 31, and the three-phase motor maintains normal operation.

[0038] When the internal temperature of the motor exceeds the response temperature of the bimetallic strip 33, the bimetallic strip 33 is heated and flipped over, thereby driving the moving contact 31 to separate from the first fixed contact 4 and the second fixed contact 5 at the same time. Figure 2 、 Figure 3 As shown, the V phase and W phase of the three-phase circuit are cut off at the same time, that is, the U, V, and W phases are cut off at the same time, thereby forming overheat protection for the three-phase motor.

[0039] In this way, compared with the technical solution in the prior art that requires ensuring that the contact plate and the three fixed contacts maintain effective contact at the same time in order to connect the three-phase windings of the three-phase motor to each other in a star shape, the three-phase thermal protector in this embodiment fixes two fixed contacts, the first fixed contact 4 and the second fixed contact 5, on the cover plate 2, and makes the moving contact piece 31 in the switch mechanism 3 conductively connected to the spring piece 34, and the spring piece 34 and the housing 1 conductively connected. The U-phase winding of the three-phase motor always maintains electrical connection with the moving contact piece 31 through the housing 1 and the spring piece 34, so that the moving contact piece 31 only needs to contact the two fixed contacts to connect the three phases of the three-phase motor to each other in a star shape.

[0040] Specifically, the first fixed contact 4 and the second fixed contact 5 are fixedly installed on the cover plate 2, and when the bimetallic strip 33 is below the response temperature, the movable contact piece 31 will be pushed toward the side of the cover plate 2 by the pressing action of the bimetallic strip 33 and the spring piece 34 until it abuts against the first fixed contact 4 and the second fixed contact 5; since the movable contact piece 31 has only two limit points, the first fixed contact 4 and the second fixed contact 5, during the pushing process, when the first fixed contact 4 and the second fixed contact 5 have inconsistent protruding lengths on the inner side of the cover plate 2 due to defects in the manufacturing process or assembly accuracy, or when there are differences in protruding lengths due to different degrees of electrical wear caused by the impact of current and ablation, the movable contact piece 31 can be slightly tilted under the pressing action of the bimetallic strip 33 and the spring piece 34. The inclined state contacts the first fixed contact 4 and the second fixed contact 5 with different extension lengths at the same time, eliminating the influence of the slight inconsistency in the extension lengths of the two fixed contacts on the contact effect with the moving contact piece 31, so that the moving contact piece 31 can always maintain stable and effective contact with the first fixed contact 4 and the second fixed contact 5 under the pressure of the bimetallic strip 33 and the spring 34, so as to ensure that the U, V, and W three-phase windings of the three-phase motor can maintain a reliable star connection through the moving contact piece 31 during normal operation, thereby avoiding the situation of phase loss operation of the three-phase motor, and effectively avoiding the problems of overheating, reduced efficiency and even burning of the three-phase motor due to phase loss operation, which is beneficial to ensuring the normal operation of the three-phase motor and extending the service life of the three-phase motor.

[0041] In some embodiments, see Figure 1 、 Figure 2 、 Figure 3 、 Figure 4The first and second fixed contacts 4, 5 are located on the outside of the cover plate 2 and are each connected to a soldering piece 7 for connecting to the first and second leads 61, 62. The soldering piece 7 includes a fixing plate 71, a connecting plate 72, and a positioning plate 73. The first and second fixed contacts 4, 5 are rivet structures. The upsetting portion formed when the first and second fixed contacts 4, 5 are riveted can press and secure the fixing plate 71 of the corresponding soldering piece 7 to the cover plate 2, thereby securing the first and second fixed contacts 4, 5 to the corresponding fixing plate 71 on the outer end of the cover plate 2 and conductively connecting to the corresponding fixing plate 71. The connecting plate 72 is constructed on the outside of the fixing plate 71 and extends outward. The positioning plates 73 are constructed on both sides of the outer end of the connecting plate 72. The two positioning plates 73 and the connecting plate 72 enclose a wire clamping slot 70 that is closed on three sides and open on one side. ; In this way, when welding the first lead 61 connecting the V-phase winding of the three-phase motor and the first fixed contact 4, and the second lead 62 connecting the W-phase winding of the three-phase motor and the second fixed contact 5, all the copper wires after the insulation layer of the leads are stripped can be placed in the wire clamping groove 70, and welding between the leads and the welding wire sheet 7 is performed at the wire clamping groove 70, so that the copper wires scattered at the lead ends can be gathered through the connecting plate 72 and the two positioning plates 73, which can effectively avoid the copper wires at the ends of the first lead 61 and the second lead 62 from being scattered, thereby effectively improving the connection reliability between the first lead 61 and the first fixed contact 4, and the second lead 62 and the second fixed contact 5, which is beneficial to ensuring the overcurrent performance, and at the same time, it can avoid the copper wires at the ends of the first lead 61 and the second lead 62 from being cross-entangled and interfering with the circuit.

[0042] In some embodiments, see Figure 1 、 Figure 2 、 Figure 3 A bump 74 is formed on the connecting plate 72 at a position within the wire clamping groove 70. The bump 74 effectively increases the contact area between the copper wires of the first and second leads 61, 62 after the insulation layer is stripped off and the bonding wire piece 7, thereby facilitating the spot welding operation between the first and second leads 61, 62 and the bonding wire piece 7. This can effectively improve the connection reliability between the first and second leads 61, 62 and the bonding wire piece 7, and at the same time help ensure the electrical conductivity between the first and second leads 61, 62 and the bonding wire piece 7.

[0043] In some embodiments, see Figure 1 、 Figure 2 、 Figure 3 、 Figure 4The connecting plate 72 is provided with a process notch 721 for facilitating bending of the connecting plate 72. The process notch 721 is located between the fixing plate 71 and the positioning plate 73 and is arranged parallel to the cover plate 2. By providing the process notch 721, after the two welding wire pieces 7 are respectively spot-welded and fixed with the first lead 61 and the second lead 62, the connecting plate 72 of the two welding wire pieces 7 can be bent through the process notch 721 to reduce the space occupied by the welding wire pieces 7; correspondingly, as Figure 4 As shown, in this embodiment, the third lead 63 is connected to the upper portion of the outer side of the housing 1, located on the side of the bending direction of the welding wire sheet 7. This makes the arrangement of the three leads of the three-phase thermal protector more compact, and the three-phase thermal protector product after subsequent wrapping and molding is compact and has an attractive appearance. In addition, by uniformly providing process notches 721 on the connecting plates 72 and arranging the process notches 721 parallel to the cover plate 2, the connecting plates 72 can be effectively prevented from being broken during the bending process. At the same time, the bending consistency of the two connecting plates 72 can be ensured, facilitating the subsequent wrapping and molding operation of the three-phase thermal protector.

[0044] In some embodiments, the soldering wire piece 7 is integrally formed, with high structural strength and stable and reliable connection. The connecting plate 72 and two positioning plates 73 are formed by bending, wherein the connecting plate 72 is arranged perpendicular to the fixed plate 71, and the positioning plates 73 are arranged perpendicular to the connecting plate 72, so as to facilitate the riveting installation between the first fixed contact 4, the second fixed contact 5 and the corresponding soldering wire piece 7. The outer end surface of the connecting plate 72 extends outward and protrudes from the outer end surface of the positioning plate 73. In this way, the portion of the connecting plate 72 protruding from the outer end surface of the positioning plate 73 can provide support for the portion of the lead near the welding point, which helps to further ensure the reliability of the connection between the first lead 61, the second lead 62 and the soldering wire piece 7.

[0045] In some embodiments, see Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 The cover plate 2 is an insulator and is provided with a stopper 21 protruding from its upper end surface. The first and second fixed contacts 4, 5 are symmetrically arranged on either side of the stopper 21. As such, after the soldering wire sheet 7 is bent and formed, the stopper 21 on the cover plate 2 isolates the first and second fixed contacts 4, 5. This effectively ensures a sufficient creepage distance between the outer ends of the first and second fixed contacts 4, 5. This ensures sufficient creepage distance between the first and second leads 61, 62, respectively connected to the first and second fixed contacts 4, 5, and the corresponding soldering wire sheet 7.

[0046] In some embodiments, the inner and outer surfaces of the housing 1, the surface of the movable contact piece 31, and the surface of the spring 34 are silver-plated. In this way, the current capacity of the housing 1, the movable contact piece 31, and the spring 34 can be effectively improved, thereby improving the reliability of the three-phase thermal protector.

[0047] In some embodiments, an insulating sealing layer can be covered on the upper end of the cover 2. The insulating sealing layer is made of insulating materials such as epoxy resin, and an insulating sleeve is wrapped around the outside of the outer shell 1 and the insulating sealing layer. In this way, the gap between the cover 2 and the outer shell 1 can be sealed by the insulating sealing layer. At the same time, the insulating sealing layer can be used to form an insulating isolation between the first fixed contact 4, the second fixed contact 5 and the connection points of the first lead 61, the second lead 62. The entire ball is then covered with the insulating sleeve, and the insulating sleeve is wrapped tightly around the entire ball by heat shrinking. The excess part is then cut off to form a finished three-phase thermal protector.

[0048] Finally, it should be noted that although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention, and all should be included in the scope of protection of this application.

Claims

1. A three-phase thermal protector, comprising a housing (1), a cover plate (2), and a switch mechanism (3), wherein the housing (1) is a cup-shaped structure with a hollow interior, the cover plate (2) is fixedly mounted in the housing (1), and the switch mechanism (3) is arranged in a cavity between the cover plate (2) and the bottom of the housing (1), characterized in that: The cover plate (2) is an insulator, and a first fixed contact (4) and a second fixed contact (5) are fixedly mounted on the cover plate (2), with both ends of the first fixed contact (4) and the second fixed contact (5) passing through and extending outward from both sides of the cover plate (2); The housing (1) is conductive, and the switch mechanism (3) includes a movable contact piece (31), and a bimetallic piece (33) and a spring piece (34) which are sequentially passed through the movable contact piece (31) on a side facing away from the cover plate (2) via a shaft pin (32). The movable contact piece (31) and the spring piece (34) are conductively connected, and the spring piece (34) and the housing (1) are conductively connected. The bimetallic piece (33) can drive the movable contact piece (31) and the first fixed contact (4) and the second fixed contact (5) to close or open simultaneously according to temperature conditions. Wherein, when the response temperature of the bimetallic strip (33) is below, the movable contact piece (31) is always in contact with the first fixed contact (4) and the second fixed contact (5) at the same time, and two phase windings of the three-phase motor are electrically connected to the movable contact piece (31) by the first lead (61) and the second lead (62) through the first fixed contact (4) and the second fixed contact (5), respectively, and the other phase winding of the three-phase motor is electrically connected to the movable contact piece (31) by the third lead (63) through the housing (1) and the spring piece (34), so that the three phase windings of the three-phase motor are connected to each other in a star shape through the movable contact piece (31).

2. The three-phase thermal protector according to claim 1, characterized in that: The first fixed contact (4) and the second fixed contact (5) are located outside the cover plate (2) and are respectively connected to a welding wire sheet (7) for connecting the first lead (61) and the second lead (62) (6), wherein the welding wire sheet (7) comprises a fixing plate (71), a connecting plate (72), and a positioning plate (73); The first fixed contact (4) and the second fixed contact (5) are rivet structures, and the first fixed contact (4) and the second fixed contact (5) are formed by press riveting to fix the corresponding fixed plate (71) to the outer end of the cover plate (2) and are conductively connected to the corresponding fixed plate (71); The connecting plate (72) is constructed on the outside of the fixing plate (71) and extends outward, and the positioning plates (73) are constructed on both sides of the outer end of the connecting plate (72). The two positioning plates (73) and the connecting plate (72) enclose a wire clamping groove (70) with three closed sides and one open side.

3. The three-phase thermal protector according to claim 2, characterized in that: A protrusion (74) is constructed on the connecting plate (72) at a position within the wire clamping groove (70).

4. The three-phase thermal protector according to claim 2, characterized in that: The connecting plate (72) is provided with a process notch (721) for facilitating bending of the connecting plate (72); the process notch (721) is located between the fixing plate (71) and the positioning plate (73) and is arranged parallel to the cover plate (2).

5. The three-phase thermal protector according to claim 4, characterized in that: The welding wire sheet (7) is formed as an integral structure, the connecting plate (72) is arranged perpendicular to the fixing plate (71), and the positioning plate (73) is arranged perpendicular to the connecting plate (72); The outer end surface of the connecting plate (72) extends outward and protrudes from the outer end surface of the positioning plate (73).

6. The three-phase thermal protector according to claim 1 or 2, characterized in that: The cover plate (2) is provided with a stopper (21) protruding from the upper end surface of the cover plate (2), and the first fixed contact (4) and the second fixed contact (5) are symmetrically arranged on both sides of the stopper (21).

7. The three-phase thermal protector according to claim 6, characterized in that: A first step (11) is formed on the circumference of the inner wall of the shell (1), a support ring (8) is embedded in the interior of the shell (1) through the first step (11), the cover plate (2) is placed on top of the support ring (8), the outer end opening of the shell (1) is folded inward to form a folded portion (12), and the cover plate (2) is fixedly mounted on the shell (1) by wrapping its top outer edge with the folded portion (12).

8. The three-phase thermal protector according to claim 1, characterized in that: The shaft pin (32) is riveted and fixed on the movable contact piece (31); a first shoulder (321) is constructed at one end of the shaft pin (32) away from the cover plate (2); a through hole is constructed at the center of the spring piece (34); the spring piece (34) is sleeved on the first shoulder (321) of the shaft pin (32) through the through hole; and the inner side of the spring piece (34) always keeps in contact with the movable contact piece (31) so as to be conductively connected to the movable contact piece (31); a second step (13) is further constructed on the circumference of the inner wall of the housing (1); the outer edge of the spring piece (34) is inserted between the second step (13) and the support ring (8); and the outer edge of the spring piece (34) always keeps in contact with the second step (13) so as to be conductively connected to the housing (1).

9. The three-phase thermal protector according to claim 8, characterized in that: A second shoulder (322) is also formed on the shaft pin (32) at a position adjacent to the first shoulder (321), a through hole is formed in the center of the bimetallic strip (33), and the bimetallic strip (33) is movably sleeved on the second shoulder (322) of the shaft pin (32) through the through hole; When the temperature is below the response temperature of the bimetallic strip (33), the spring (34) presses the movable contact (31) by its own elastic force to a state where the movable contact is always in contact with the first fixed contact (4) and the second fixed contact (5). The bimetallic strip (33) flips over when the temperature exceeds its response temperature, thereby overcoming the elastic force of the spring (34) and driving the movable contact (31) to separate from the first fixed contact (4) and the second fixed contact (5) simultaneously.

10. The three-phase thermal protector according to claim 8, characterized in that: The surfaces of the housing (1), the movable contact piece (31), and the spring piece (34) are silver-plated.

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