JPH0112764Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to an overcurrent detection device for circuit breakers. Circuits and breakers to which this invention can be applied are shown in FIGS. 1 to 13. In other words, this three-phase circuit disconnector has a disconnector main body 3 consisting of a stand 1 and a case 2, which are interconnected and installed in the panel using screws through connection holes 3a and mounting holes 3b, respectively. A groove 4 is formed in the instrument base 1, an arc extinguishing device 5 (Fig. 5) is mounted in the groove 4, and positioning guide slits 4a and 4b are formed on the side surface of the groove 4 to attach the operating mechanism part 6. , short circuit sensor 7, bimetal device 8, load side connection terminal 9, and movable contact 10
The supporting frame (frame) A that integrally holds the
1 and 12. Reference numeral 13 denotes a power supply side connection terminal, which connects the fixed contact 14 as shown in FIG.
At the same time, the fixed contact 15 is fixed to the fixed contact 1.
A step is formed so as to be flush with the surface of 5, and also serves as an arc traveling section 14'. As shown in FIGS. 5 to 7, the support frame A has a pivot shaft 16 for opening and closing the contact at one end of its upper part, and a long groove-shaped notch in the opening and closing plate 17 that holds the movable contact 10. A return spring 19 for contact is interposed between the opening/closing plate 17 and a branch piece 18 that engages the bearing groove 17a and protrudes from one side of the support frame A at the lower part of the pivot shaft 16. Further, a handle support shaft 20 is installed at the center of the upper part of the support frame A, a handle link 21 is pivotally connected thereto, and a handle 22 is detachably attached to the support shaft 20. This handle link 21 has a substantially U-shaped plate shape as shown in FIG.
a, 23b are formed, the handle support shaft 20 is fitted into the shaft hole 23a, the reversal shaft 24 is installed in the shaft hole 23b, the reversal link 25 is connected to the reversal shaft 24, and a handle is attached to both end pieces of the handle link 21. The engagement/stopper piece 23c is bent. On the other hand, the handle 22 has a pair of supporting legs 26 and 27 from its shaft bearing.
The handle support shaft 20 is protruded between the support legs 26 and 27.
The intermediate piece 23d of the handle link 21 is positioned so that the handle 22 and the link 21 operate integrally. An interlocking shaft 28 is installed at the lower end of the reversing link 25, and its shaft end passes through the trip state positioning window 29 of the support frame A. A main link 31 is connected to a connecting shaft 30 installed at the bottom. The support frame A further forms a horizontally elongated hole 32 at a position diagonally below the handle support shaft 20, and a movable shaft 33 is movably installed in the elongated hole 32, so that the movable shaft 33 and the interlocking shaft 28 are connected to each other. The tripping side link 34 between
A return spring 28a (using a torsion coil spring) for trip operation supported by the interlocking shaft 28 is interposed between the reversing link 25 and the tripping side link 34. In addition, the horizontally long hole 32 of the support frame A
A latch link support shaft 35 is installed immediately above the
The latch link 36 is swingably supported, and a vertically elongated hole 37 is formed in the side piece 36a of the latch link 36, which is inserted into the movable shaft 33. By horizontally moving the movable shaft 33 through the horizontally elongated hole 32, the latch link 36
6 can be rotated around a support shaft 35. The latch link 36 also has a latch engagement hole 36b.
is formed. As shown in FIG. 7, a tripping metal support shaft 38 is installed diagonally below the horizontally elongated hole 32 of the support frame A, and a tripping metal fitting 39 is pivotally attached to this support shaft 38. The tripping fitting 39 integrally forms an engagement protrusion 40 that engages with the latch engagement hole 36b, and also includes a bimetal pressure sensing portion 41 and a movable bar pressure sensing portion 42 of the short circuit sensor 7.
A return spring 44 for the tripping metal fitting is stretched between the movable rod pressure sensing portion 42 and a hole 43 formed in the supporting frame A. The support frame A further forms a rising piece 45a at one lower end thereof, and a fixing portion 45b on the other side of the support frame A.
The upper arc running plate 45 is horizontally extended from the lower end of the rising piece 45a. Then, the base end of the bimetal 8a of the bimetal device 8 is welded to the upper end 45c of the rising piece 45a, and the base end and the upper end of the movable contact 10 are connected with a copper stranded wire 46, and the tip of the bimetal 8a is welded. The portion is close to the adjustment screw 41a provided on the bimetallic pressure sensing portion 41 of the tripping fitting 39. Also, the coil tube 4 is placed between the rising piece 45a and the mounting plate 47 fixed to the support frame A.
A fixed core 49 is fixed to the mounting plate 47 side of the coil tube 48, a plunger 50 is slidably disposed on the rising piece 45a side, and a return spring 51 is installed between the plunger 50 and the fixed core 49. is intervening. The fixed core 49 has a movable rod 49a in the axial direction.
is inserted, one end of which contacts the plunger 50 and the other end approaches the movable rod pressure sensing portion 42 of the tripping plate 39. A coil 52 is wound around the coil tube 48, one end of which is connected to the tip of the bimetal device 8 via a copper stranded wire 53, and the other end is welded to the load side connection terminal 9. The plunger 50 also integrally projects a protruding rod 50b having a flange 50a at its tip, and penetrates the movable contact 10.
engages with the movable contact 10, forcing the movable contact 10 to open. In addition, 54 is a synchronous tripping member rotatably fitted into the groove 55 of the support frame A, and the support frame in the other phase
It is constructed across A′, A″ and support frame A,
Feet 54a, 54 are placed in each support frame A, A', A'', respectively.
b protrudes, the foot 54a is placed on the latch link 36, the foot 54b is opposed to the tripping metal fitting 39,
If an overcurrent flows in one of the phases, the tripping fitting 3
When the latch link 36 is operated, the leg 54a is lifted up and the synchronous tripping member 54 is rotated, and the leg 54b operates the tripping fitting 39 in the other phase to perform the latch operation. . 56 is a holding plate for the synchronization tripping member 54. The movable contact 10 is positioned in the slit of the device stand 1 by using the protrusions 11 and 12 formed on the arc running plate 45 and the mounting plate 47 to position the support frame A incorporating the operating mechanism and others as described above. The movable contact 10a faces the fixed contact 15, and the load side connection terminal 9 is located on the opposite side of the power supply side connection terminal 13 of the device stand 1. Furthermore, the case 2 prevents the handle 22 from coming off. Next, the arc extinguishing device installed in the groove 4 of the table 1 is installed in the table 1 as shown in FIGS.
The lower arc traveling plate 57 is fixed to the bottom of the groove of the contactor 14.
A gas vent hole 58 is formed in the side wall opposite to the side where the fixed contact 15 and the movable contact 10a are located, and a guide column 59 is erected in front of the gas vent hole 58. integrally molded with). An insulating exhaust plate 61 having two rows of exhaust holes 60 formed therein is erected and supported by the guide column 59 and the guide groove 4c on the side surface of the groove. A deion grid 62 is installed closely in front of the exhaust plate 61 and supported by a block plate 61a. A ceramic arc gas circulation plate 63 is installed in front of the deion grid 62. In addition,
64 is an insulating plate laid on the upper surface of the arc traveling plate 45, and 65 is an insulating plate that partitions each phase. The operation of this circuit breaker will be explained. The on state is as shown in FIGS. 5 and 13a.
First, the tripping metal fitting 39 is returned to the state shown in the figure by the return spring 44, and the latch link 36 is assumed to be engaged with the engagement protrusion 40 of the tripping metal fitting 39 (engaged at the time of reset operation: described later). . When the handle 22 is tilted to the right as shown in the figure, the rotating edge pushes the stopper piece 23c of the handle link 21 to rotate the handle link 21 about the pivot shaft 20, and the reversing shaft 24 is moved to the position shown in the figure. It is rotating and moving to.
In this state, the movable shaft 33 is connected to the latch link 3.
6 is fixed to the engagement protrusion 40, the horizontally elongated hole 3
2 and the longitudinal hole 37, and since the tripping side link 34 is supported by the movable shaft 33, the interlocking shaft 28 is moved downward by the reversing link 25, whereby the tripping side link 34 and the main link 31 extend from the chevron with the interlocking shaft 28 at the apex to a straight line, moving the connecting shaft 30 to the right in the figure, and the movement of the connecting shaft 30 causes the opening/closing plate 17 to release the return spring 19 The movable contact 10a of the movable contact 10 is brought into elastic contact with the fixed contact 15, and contact pressure is applied by the rotational moment about the connecting shaft 30, and the opening/closing plate 1 is rotated around the contact part.
7 swings, and the pivot shaft 16 is slightly moved from the bearing groove 17a. Furthermore, in this state, the spring force of the return spring 19 causes the interlocking shaft 2 of the main link 31 to
8 upward, and the reversing shaft 2 of the reversing link 25
4 is located on the left side (in the figure) of the line connecting the interlocking shaft 28 and the handle support shaft 20, and is pressed in that direction, and the stopper piece 23c is pressed in the upper end recess a of the support frame A.
(Fig. 7), it is in a stable state.
In this way, the electric path includes the power supply side connection terminal 13, the fixed contact 14, the fixed contact 15, the movable contact 10a,
Movable contact 10, copper stranded wire 46, bimetal 8
a, it is closed and formed by the copper stranded wire 53, the coil 52, and the load side connection terminal 9. The off operation is as shown in FIG. 10 and FIG. 13b. That is, the handle 22 is tilted to the left (as shown in FIG. 5) from the above-mentioned on state. As described above, since the interlocking shaft 28 is urged upward by the return spring 19, the reversing shaft 24 moves along the line connecting the interlocking shaft 28 and the handle support shaft 20 by tilting the handle 22 to the left. When it crosses over, the interlocking shaft 28 moves upward forcefully by the action of the return spring 19, tilting the handle 22, and pulling the connecting shaft 30 to open and separate the movable contact 10 about the pivot shaft 16. In this case, until the reversing shaft 24 crosses the line connecting the interlocking shaft 28 and the handle support shaft 20 due to the leftward tilting operation of the handle 22, the movable contact 10 has a contact portion as the center, and the bearing groove 17a is aligned with the pivot shaft 16. The fixed contact 15 and the movable contact 10a are in contact with each other in the range before they are engaged with each other. The trip state is shown in Figures 11, 12 and 1.
As shown in Figure 3 c and d. When an overcurrent flows through the electric circuit, the operation shown in FIGS. 12 and 13c occurs. That is, the bimetal 8a generates heat and moves in a curved manner, causing the bimetal pressure sensitive part 41 of the tripping fitting 39 to
Press the adjusting screw 41a. As a result, the tripping metal fitting 39 swings around the support shaft 38 and performs a tripping operation in which the engagement protrusion 40 is disengaged from the engagement hole 36b. When the engagement protrusion 40 comes off, the latch link 36
The movable shaft 33 moves into the horizontally long hole 3 of the support frame A due to the spring force of the return spring 19 applied to the movable shaft 33 via the main link 31 and the tripping side link 34.
2 to tilt the vertical hole 37 of the latch link 36 and rotate the latch link 36 around the support shaft 35. At the same time, the interlocking shaft 2 attached to the main link 31
8 moves horizontally, the reversing shaft 24 of the reversing link 25 is located on the opposite side of the line connecting the handle support shaft 20 and the interlocking shaft 28, and the reversing shaft 24 is reversely biased by the return spring 28a. The handle link 21 tilts around the handle shaft 20, and the stopper piece 23c and the engaging piece 23d of the handle link 21 rotate the handle 22 to the left. At that time, the interlocking shaft 28 moves upward from the horizontally moved state, so that its shaft end is located at the positioning protruding edge 29a (the seventh position) of the trip state positioning window 29 of the support frame A.
) to keep the handle 22 in the neutral state (upright)
maintain it. Further, as the main link 31 moves leftward, the connecting shaft 30 moves and the opening/closing plate 1
7 is swung about the pivot shaft 16 by the return spring 19, the movable contact 10 is opened and opened, and the movable contact 10a is opened from the fixed contact 15, thereby severing the electric path. On the other hand, when a short circuit current flows, the operations shown in FIGS. 11 and 13d occur. That is, the coil 52
, the plunger 50 is attracted and driven, and the pressure-sensitive part 42 of the tripping metal fitting 39 is pushed through the movable rod 49a, and the tripping metal fitting 39 rotates to trip the latch link 36. At the same time, the flange 50a
The movable contact 10 is forcibly opened, and the movable contact 10 is opened through the trip links of the trip side link 34, the reversal link 25, and the main link 31 before the movable contact 10 is opened. In this case, movable contact 1
0 swings around the connecting shaft 30 of the opening/closing plate 17 against the reaction force of the return spring 19, and rotates around the opening/closing pivot shaft 16.
From then on, the bearing groove 17a begins to move. The reset operation of the handle 22 from the neutral position is performed as follows. That is, when the handle 22 is tilted to the left, the handle link 21 is tilted.
The reversing shaft 24 moves to the upper right and the reversing link 25 pulls up the interlocking shaft 28 from the positioning edge 29a of the support frame A. As a result, the trip side link 34 moves upward to the right and the main link 31 moves to the left upward to the left, the movable shaft 33 is pulled back by the trip side link 34, and the vertical hole 37 of the latch link 36 is pushed to lock the latch link. 36 is rotated, and the engagement hole 36b is engaged with the engagement protrusion 40 of the tripping metal fitting 39 (the tripping plate 39 has been returned to its original position by the return spring 44). This results in the off state shown in FIGS. 10 and 13b. Next, when breaking the electric path, the movable contact 10
The arc generated between the arc extinguishing device 5 and the fixed contact 15 is elongated and transferred to the arc running plates 45 and 57 of the arc extinguishing device 5, and is driven by gas and magnetism to the grid 62, where it is divided and extinguished. The gas is exhausted through the gas vent hole 58. In the above-mentioned circuit breakers and disconnectors, the adjustment of the adjustment screw 41a of the overcurrent detection device is as shown in FIG. In this state, the slightly curved tip of the bimetal 8 is brought into contact with the tip of the adjusting screw 41a as shown in FIG. The adjustment screw 41a is pushed up and the bimetallic pressure sensitive part 41 is driven to tilt, so that the overcurrent is quickly cut off by the tripping mechanism. However, when the rated current is applied, the first
As shown in Figure 4b, the tip of the bimetal 8 is in contact with the adjustment screw 41a, so there is a risk that the adjustment screw 41a will be pushed up by the bimetal 8 and mistrip will occur if even a slight vibration or impact is applied from the outside. Ta. Further, the pressing force (output) of the adjusting screw 41a by the bimetal 8, which is an overcurrent detection device, is small, and an attempt to increase this output results in an increase in the size of the device. Furthermore, since the output of the bimetal 8 is small and the output varies widely, it is necessary to strictly control the product and the number of manufacturing steps increases.
Moreover, many types of bimetals 8 are required to accommodate various rated currents, and the device tends to be expensive. On the other hand, known examples (Utility Model Application Publication No. 50-93574,
Utility Model Application No. 50-93577, etc.) suggests a method using a shape memory alloy instead of a bimetal. According to this shape memory alloy, it is possible to easily prevent mistrips caused by vibrations, etc., and the pressing force is large and the output is stable. However, there was a drawback that many types were required depending on various ratings. Therefore, an object of this invention is to provide an overcurrent detection device for circuits and breakers that uses a shape memory alloy and can accommodate a plurality of ratings with one type. An embodiment of this invention will be described with reference to FIGS. 15 to 23. That is, this overcurrent detection device for circuit breakers includes a heater 66 through which a detection current is passed, a shape memory alloy 67 that is heated and deformed by the heater 66 when an overcurrent is applied, and a shape memory alloy 67 that is deformed by the heater 66 when an overcurrent is applied. An example of the trip member is a trip member 39 that is spaced apart and is pressed by the action of the shape memory alloy 67, and a tension spring 68 that biases the shape memory alloy 67 in a direction opposite to the operating direction. It is provided with an operating temperature adjusting spring and an adjusting means exemplified by an adjustable screw 69 for adjusting the amount of displacement of the shape memory alloy 67 by changing the spring force of the operating temperature adjusting spring. As shown in FIG. 16, the heater 66 has one end supported by a conductive part 70 that conducts to the load side connection terminal 9, and the other end supported by a copper stranded wire 4 that conducts to the movable contact 10.
Connect 6. 10a is a movable contact, 13 is a power supply side connection terminal, and 15 is a fixed contact. The shape memory alloy 67 is, for example, “Cu-Zn-Si,
Formed into a coil shape using Sn, Al, Ga'' alloy,
At room temperature (temperature of heater 66 when rated current is applied), it is in a contracted state as shown in Figure 19a, and at high temperature above the transformation point (temperature of heater 66 when overcurrent is applied) as shown in Figure 19b. The proximal end 67b is fixed to the upper surface of the heater 66 so that the distal end 67a is spaced below the adjusting screw 41a of the pressure sensitive part 41 of the tripping fitting 39 at room temperature. The adjustable screw 69 is threaded through the heater 66 on the axis of the shape memory alloy 67 as shown in FIG. A tension spring 68 is tensioned between the press plate 71 and the upper end of the adjustable screw 69. The biasing force of this tension spring 68 can be adjusted by using an adjustable screw 69.
This is done by inserting a flathead screwdriver into the flathead groove 69a provided at the lower end of the screwdriver and rotating it to adjust the adjustable screw 69 forward and backward in its axial direction. The coil 52 for operating the short circuit sensor 7 (FIG. 16) has one end connected to the movable contact 10 and the other end connected to the conductive part 70.
As shown in FIG. 20, a coil 52 and a heater 66 are connected in parallel between the movable contact 10a and the load side connection terminal 9. The rest of the configuration is the same as that of the prior art, so the same parts are given the same reference numerals and the explanation thereof will be omitted. Next, the operation of the shape memory alloy 67 will be explained.
First, in a non-energized state (off operation), the shape memory alloy 67 is separated from the adjustment screw 41a, as shown in FIG. 15a. Next, when the rated current is applied (when turned on), the shape memory alloy 67 is heated by the heater 66, but since the temperature is still below the transformation point, it is still separated from the adjustment screw 41a as shown in FIG. 15b. It remains as it is.
When an overcurrent flows, the shape memory alloy 67 is heated to a temperature higher than its transformation point by the heater 66 and expands as shown in FIG. Operate the release mechanism to cut off the electrical circuit. In this case, turn the adjustable screw 69 to release the tension spring 68.
shape memory alloy 67 by adjusting the biasing force of
The operating temperature of the tripping mechanism can be adjusted by The principle will be explained below. Figure 21 shows
It is a displacement amount-biasing force relationship characteristic diagram in which the horizontal axis shows the displacement amount of the shape memory alloy 67 and the vertical axis shows the biasing force of the tension spring 68. In the figure, curves L, M, and N are characteristic curves at temperatures T ₁ , T ₂ , and T ₃ (with the relationship of T ₁ <T ₂ <T ₃ ), respectively. Now, tension spring 6
If the biasing force of 8 is set to P ₁ , the temperature will be T ₁ ,
As the temperature increases to T ₂ and T ₃ , the displacement amount of the shape memory alloy 67 increases sequentially to δ ₁ , δ ₂ , and δ ₃ . Similarly, when the biasing force of the tension spring 68 is set to P ₂ (larger than P ₁ ), the amount of displacement of the shape memory alloy 67 increases to δ ₄ , δ ₅ , and δ ₆ as the temperature rises. In this case, as is clear from the figure, the displacement amounts δ ₄ , δ ₅ , δ ₆ when a large urging force P ₂ is applied are the same as the respective displacement amounts δ ₁ , δ 2 , δ ₆ when a small urging force P ₁ is applied. Each becomes smaller compared to δ ₃ . In this way, by adjusting the adjustable screw 69 to increase the biasing force of the tension spring 68, the amount of displacement of the shape memory alloy 67 can be reduced.In other words, the pressing plate 71 presses the adjusting screw 41a and trips it. The so-called operating temperature at which the mechanism is operated can be increased, and conversely, by reducing the biasing force of the tension spring 68, the amount of displacement of the shape memory alloy can be increased and the operating temperature can be lowered. Thus, this circuit breaker uses a shape memory alloy 67 to actuate the tripping mechanism, and this shape memory alloy 67 does not progressively bend as temperature increases like the prior art bimetal 8. Because it has the property of instantaneously expanding when heated above its transformation temperature, it is possible to obtain an output approximately 200 times greater than that of bimetal 8. Therefore, the device can be made smaller. In addition, the shape memory alloy 67 remains in the first position even when the rated current is applied.
As shown in FIG. 5B, since it is far away from the adjusting screw 41a, even if vibration or impact is applied from the outside, the adjusting screw 41a will not be pushed up, and malfunctions such as mistrips can be prevented. Furthermore, since the output of the shape memory alloy 67 is large and the variation in output is small, there is no need for strict manufacturing control, and the number of manufacturing steps can be reduced, resulting in low cost. Furthermore, by simply turning the adjustable screw 69 and changing the biasing force of the tension spring 68, the operating temperature of the tripping mechanism using the shape memory alloy 67 can be adjusted.
One type of shape memory alloy 67 can be commonly used for various ratings. Note that the shape memory alloy 67 returns to its original contracted state (FIG. 19a) when its temperature drops to a predetermined value. Finally, we will explain the basic characteristics of shape memory alloys. In general, shape memory alloys have a special property in that if they are heated to a certain temperature and then rapidly cooled, they change shape, but return to their original shape as the temperature is raised. Figure 22 shows this situation.
Moreover, FIG. 23 shows a characteristic diagram of the relationship between temperature and specific resistance of the Ti--Ni alloy. In the figure, M _s is the M transformation start temperature, M _f is the M transformation end temperature, A _s is the reverse transformation start temperature, and A _f is the reverse transformation end temperature. In other words, if a shape memory alloy is formed into a linear shape at a high temperature, as shown in _FIG . When the temperature is raised again, the temperature at which reverse transformation starts is reached.
When the temperature exceeds A _s , it begins to gradually return to its original shape as shown in Figure c and Figure d, and the temperature at which reverse transformation ends is reached.
When it reaches A _f , it completely returns to its original straight shape as shown in e of the same figure. The table below shows materials with perfect shape memory effect.

[Table] As described above, the overcurrent detection device for circuit breakers of this invention includes: a heater through which a detection current is passed; a shape memory alloy that is heated and deformed by the heater when an overcurrent is applied; a tripping member that is spaced apart from the shape memory alloy and is pressed by the action of the shape memory alloy; an operating temperature adjustment spring that biases the shape memory alloy in a direction opposite to the operating direction; Since the present invention includes an adjusting means for adjusting the amount of displacement of the shape memory alloy by changing the spring force, the following effects can be obtained. That is, the amount of displacement of the shape memory alloy during operation changes depending on the magnitude of the spring force applied in the opposite direction to the direction of operation. Therefore, by biasing the shape memory alloy in the opposite direction to the operating direction using an operating temperature adjustment spring and adjusting the spring force using an adjustment means, it is possible to support multiple types of ratings with one type of overcurrent detection device. I can do it.

[Brief explanation of the drawing]

Figure 1 is a plan view of the circuit breaker which is the basis of this invention, Figure 2 is a plan view with the case removed, Figure 3 is a cross-sectional view taken along the line shown in Figure 1, and Figure 4 is its top view. - Line sectional view, Figure 5 is a line sectional view of Figure 3, Figure 6 is a perspective view of the support frame, Figure 7 is an exploded perspective view thereof, Figure 8 is a partially broken exploded perspective view of the arc extinguishing device. , FIG. 9 is a plan view of the arc extinguishing device, FIG. 10 is a front view of the operating mechanism in the off state, FIG.
Figure 2 is a front view of the operating mechanism in the tripped state;
Figure 3 is a mechanism diagram showing each operating state, Figure 14a,
b, c are explanatory diagrams of the operation of the tripping mechanism made of bimetal, FIG. 15 is an explanatory diagram of the operation of the tripping mechanism made of shape memory alloy in one embodiment of this invention, and FIG.
17 is a perspective view of the shape memory alloy and the heater, FIG. 18 is a side view thereof, FIG. 19a is a side view showing the shape of the shape memory alloy at room temperature, and FIG. Figure b is a side view showing the shape of the shape memory alloy at temperatures above the transformation point temperature, Figure 20 is the circuit diagram of this example, and Figure 21 is a characteristic diagram of the relationship between the displacement amount of the shape memory alloy and the biasing force of the tension spring. , second
FIG. 2 is an explanatory diagram showing the shape change of the shape memory alloy, and FIG. 23 is a characteristic diagram showing the relationship between temperature and specific resistance of the Ti-Ni alloy. 10...Movable contact, 39...Tripping member which is a tripping fitting, 66...Heater, 67...Shape memory alloy, 68...Tension spring which is an operating temperature adjustment spring, 69...Adjustable screw Some adjustment means.

Claims (1)

[Scope of utility model registration request] A heater through which a detection current is passed, a shape memory alloy that is heated and deformed by the heater when an overcurrent is applied, and a tripping member that is spaced apart from the shape memory alloy and is pressed by the action of the shape memory alloy. , a circuit comprising an operating temperature adjusting spring that biases the shape memory alloy in a direction opposite to the operating direction, and an adjusting means that adjusts the amount of displacement of the shape memory alloy by changing the spring force of the operating temperature adjusting spring. and overcurrent detection device for disconnectors.