JP3216780B2 - Circuit breaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker such as a circuit breaker for a wiring or an earth leakage breaker, and more particularly to a protection plate attached to an arc gas discharge port thereof.

[0002]

2. Description of the Related Art FIG. 11 is a longitudinal sectional view of a main part of a three-pole circuit breaker showing a conventional structure, and FIG.
It is principal part sectional drawing along a line. In FIG. 11, case 1
In an insulating container made up of a cover 2 and a cover 2, there is formed a cut-off portion including a fixed contact 3 fixed to the case 1 and a movable contact 5 driven to be opened and closed by an opening and closing mechanism 4. An arc chamber 6 is provided. Although the figure shows the cutoff portion at the center pole portion, the interior of the insulating container is partitioned into three-phase spaces by the phase separation walls, and the respective phase cutoff portions are accommodated in the respective spaces. The fixed contact 3 has a power terminal 3 at one end.
a is integrally formed, and the other end on which the fixed contact 7 is provided is folded back into a U-shape to form a parallel conductor along the movable contact 5. A movable contact 5 having a movable contact 8 which comes in contact with and separates from the fixed contact 7 is rotatably supported by the case 1 via an insulating holder 9, and is shown in a closed state with an opening / closing shaft 9 a integral with the holder 9 as a fulcrum. Is driven between the open state and the open state indicated by the chain line.

The arc-extinguishing chamber 6 includes a pair of left and right insulating support plates 10.
In this configuration, a plurality of grids 11 are vertically stacked and supported at appropriate intervals, and the grid 11 is provided with a V-shaped notch surrounding the open / close trajectory of the movable contact 5. A partition 12 made of an insulating plate is provided between the blocking unit and the opening / closing mechanism 4. The partition 12 separates the opening / closing mechanism 4 from the blocking unit except for a slit through which the movable contact 5 passes. Further, an arc gas outlet 13 is provided in front of the cutoff portion, and the arc gas outlet 13 is closed by a protective plate 14 made of an insulating material for preventing foreign matter from entering. As shown in FIG. 12, both edges of the lower half of the protection plate 14 projecting right and left are inserted and held in the groove 1 a of the case 1.

In the above-mentioned circuit breaker, when the internal pressure of the interrupting section increases due to the generation of arc gas at the time of interrupting a large current, the upper half of the protection plate 14 is pushed outward as shown in FIG. Thus, the arc gas is discharged obliquely upward from the opened arc gas discharge port 13 as indicated by the arrow. The arc gas contains the melt generated from the contacts 7 and 8, the fixed and movable contacts 3 and 5, the grid 11, and the like, but the partition 12 blocks the movement of the arc gas to the opening / closing mechanism 4 side, and the contained melt is This prevents scattering and adhesion to the opening / closing mechanism 4 and its peripheral portion.

[0005]

As described above, the protection plate for closing the arc gas discharge port of the interrupting portion usually prevents foreign substances from entering the interrupting portion, and when current is interrupted, is deformed due to a rise in internal pressure to discharge the arc gas. However, the conventional protection plate configuration has the following problems. (1) The left and right edges of the lower half of the protective plate are inserted and held in the groove of the case, and the upper half is deformed when discharging the arc gas. If the hanging amount (height dimension) is small, the protective plate will come off and pop out in one interruption, whereas if the hanging amount is too large, the deformation resistance of the upper half will increase and the internal pressure of the interruption part will be excessive, and the case and The cover may crack. (2) Since only the upper half portion of the protective plate is deformed, the direction of arc gas ejection is obliquely upward, and arc gases discharged from the respective poles may intersect with each other on the upper surface of the cover, resulting in a short-circuit between phases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit breaker in which arc gas is smoothly discharged so that a protective plate does not come off and a short circuit between phases caused by the discharged arc gas does not occur.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an arc gas discharge port in front of a cut-off portion comprising a fixed contact fixed to a case and a movable contact driven by an opening / closing mechanism. In a circuit breaker in which the arc gas discharge port is closed by a protective plate made of an insulator, a pair of right and left extending toward the arc gas discharge port is provided on a partition wall of the insulator provided between the breaking portion and the opening / closing mechanism. Are integrally formed, and the protective plate is rotatably connected to the arm via a support shaft (claim 1).

According to such a configuration, since the protection plate is connected by the support shaft, the protection plate does not easily come off even when the internal pressure increases.
In addition, when the arc gas is discharged, the arc gas is rotated around the support shaft so that the arc gas discharge port is largely opened, and the arc gas is discharged toward the power supply side of the circuit breaker. Never intersect. In this case, it is conceivable that the guard plate is directly attached to the case.However, it is not possible to form a bearing hole for receiving the support shaft on the guard plate side or a spindle inserted into the bearing hole on the guard plate side. Very difficult in molding technology. Therefore, it is preferable that a pair of left and right arms extending toward the arc gas discharge port be integrally formed on a partition wall of an insulator provided between the blocking portion and the opening / closing mechanism, and a protective plate be coupled to the arms. It is easy to integrally form the spindle or bearing hole in the partition,
In this case, the protection plate can be integrated into the case integrally with the partition, so that the assembling work is also simplified.

In the circuit breaker according to the present invention, if the elastic piece is integrally formed on the protective plate, and the elastic piece is engaged with the arm of the partition to hold the protective plate in the closed position, the arc gas is discharged. The protection plate can be automatically returned to the closed state (claim 2). In this case, if a flexible portion is formed in the vicinity of the support shaft of the protection plate, the discharge of the arc gas becomes smoother.

According to another aspect of the present invention, an arc gas discharge port is provided in front of a cut-off portion including a fixed contact fixed to a case and a movable contact driven by an opening / closing mechanism. In the circuit breaker, the arc gas outlet is closed by a protective plate made of an insulating material. In the circuit breaker, a cut is made in the protective plate to form a double-sided valve body in the plate surface, and the lower valve body is formed. The upper said valve
Longer than the body, before the lower open at the time of A Kugasu emissions
So that the valve body covers the terminal screw on the power supply side, and
The thickness of the base portion of the upper valve body is made smaller than that of the lower valve body.
And the opening angle of the lower and upper valve
It is assumed that they are substantially equal (claim 4). The cut is preferably H-shaped or W-shaped.

According to such a configuration, since only the valve body in the plate surface of the protection plate is deformed, both right and left edges thereof can be gripped by the grooves of the case and the cover over the entire height. It does not come off easily even if the internal pressure rises.
In addition, since the valve element opens up and down, the arc gas is discharged to the power supply side in parallel with the longitudinal direction of the circuit breaker, and the arc gas discharged from each pole does not cross each other on the upper surface of the cover. The lower valve body is made longer than the upper valve body so that the lower valve body opened at the time of discharging the arc gas covers the terminal screw on the power supply side, so that the arc gas is directly blown and the terminal is blown. The screw is prevented from being damaged. Furthermore, by making the thickness of the base portion of the upper valve body thinner than that of the lower valve body and making it easier to deform, even if the lengths of the upper and lower valve bodies are different, the opening angle of the upper and lower valve bodies is almost equal. The arc gas can be discharged to the power supply side parallel to the longitudinal direction of the circuit breaker.

In this case, if the valve body is formed by slightly bending the valve body toward the shut-off portion, even if a slight permanent deformation may remain in the valve body due to the interruption of a large current, the permanent deformation is provided in advance. The bending cancels out and the arc gas outlet is surely reclosed (claim 5).

By the way, if the thickness of the protective plate is increased, the durability is increased, but on the other hand, the protective plate is hardly deformed, and the internal pressure of the blocking portion is increased. Therefore, in the circuit breaker according to the fourth aspect, it is preferable that the thickness of the upper and lower valve bodies is gradually reduced from the root portion toward the tip portion (claim 6). As a result, it is possible to easily deform the valve body as a whole while increasing the thickness of the base portion of the valve body that is most consumed, and to suppress an increase in the internal pressure.

Further, in the circuit breaker according to the present invention, an insulating gas stopper plate which covers a predetermined height range from a root portion of the lower valve body to an upper portion thereof is disposed inside the protective plate. Thereby, discharge of the melt in the arc gas to the outside can be suppressed (claim 7). In other words, by disposing the gas stopper plate near the base of the lower valve body, which is located diagonally in front of the fixed contact, the arc gas containing a large amount of molten material immediately after the contact is separated once hits the gas stopper plate, Therefore, the melt in the arc gas is captured on the gas stopper plate, and the amount of discharge to the outside is reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of the present invention will be described. It is to be noted that the same reference numerals are used for the portions corresponding to the conventional example, and the description of the same components is omitted.

Embodiment 1 FIGS. 1 to 4 show an embodiment in which a protective plate is connected to a partition wall via a support shaft. FIG. 1 is a longitudinal sectional view of a main part of a circuit breaker, and FIG. A) is a front view of the protection plate, (B) is a side view thereof, (A) is a plan view of the partition wall, (B) is a side view thereof, (C) is a right front view thereof, and FIG. It is a figure which shows the discharge situation of the arc gas of 1 circuit breaker.

First, in FIG. 3, a partition wall 12 formed of an arc-resistant resin such as polyester has a slit 15 at the center for allowing the movable contact 5 to pass therethrough, and a cover for covering the U-bent portion of the fixed contact 3 at the base. 12a, and a pair of left and right arms 12b is formed on the front surface with the same width as the cover 12a. At the tip of the arm 12b, a bearing hole 12c is provided for receiving a support shaft 14a of the protection plate 14, which will be described later. In front of the bearing hole 12c, only one of the arms 12b is integrally formed with a cylindrical convex portion 12d so as to protrude inward. Have been.

As shown in FIG. 1, the partition wall 12 is placed over the fixed contact 3 from above, and the fixed contact 3 is formed by a pair of ridges 12e having a sawtooth cross-section integrally formed on the inner facing surface of the cover 12a. Locked to the folded end. In addition, the partition wall 12 is further fixed with both shoulders 12f pressed down by the step 10a of the support plate 10 of the arc-extinguishing chamber 6. In this case, the arm 12b is located inside the V-shaped notch of the grid 11.

On the other hand, in FIG. 2, the protection plate 14 is formed of, for example, nylon, and a pair of support shafts 14a projecting left and right are integrally formed at the lower end, and a flat bar-shaped elastic piece 14b is integrally formed on one of the support shafts 14a. Is formed. The protective plate 14 is connected to the partition 12 by inserting a support shaft 14a into a bearing hole 12c thereof while elastically deforming the arm 12b before the partition 12 is mounted, and the elastic piece 14b is connected to the convex portion of the arm 12b. The lower side of 12d is engaged. The protective plate 14 is incorporated into the case 1 integrally with the partition 12, and the upper end thereof is held in a position shown in FIG.

In this embodiment, when current is interrupted, the internal pressure of the interrupting section rises due to the generation of arc gas, and the protection plate 14 which has received the internal pressure, as shown in FIG.
Pivoted in the counterclockwise direction in FIG.
3 is opened to discharge the arc gas in the direction indicated by the arrow. In the meantime, the elastic piece 14b is curved as shown. Then, when the arc gas is discharged and the internal pressure decreases, the protection plate 14 returns to the closed position in FIG. 1 due to the stored force of the elastic piece 14b.

According to this embodiment, the protection plate 14 is connected via the support shaft 14a serving as a rotation fulcrum.
Even if the protection plate 14 receives the internal pressure of the blocking part, it does not come off simply by pivoting and opening. The protective plate 14 is attached to the arm 12b of the partition wall 12, but the bearing hole 12 of the arm 12b is provided.
The c and the protruding portion 12d can be easily formed integrally with the partition wall 12, and the protective plate 14 is attached to the partition wall 12 in advance, and the protective plate 14 can be integrated with the partition wall 12 into the case 1, which is advantageous in assembling work. is there.

Further, since the protective plate 14 is entirely opened with the support shaft 14a as a fulcrum, the arc gas is discharged toward the power source side (left side in FIG. 4) along the longitudinal direction (left-right direction in FIG. 4) of the circuit breaker. Thus, it is less likely to reach the upper surface of the cover 2. Therefore, no interphase short-circuit occurs due to the exchange of the discharged arc gases between adjacent electrodes. In addition, partition 1
Since the elastic piece 14b engaged with the second convex portion 12d automatically returns the protective plate 14 to the closed position after the discharge of the arc gas,
There is no need to manually return the protective plate after tripping the circuit breaker.

In the above-described embodiment, the support shaft 14a is provided on the protection plate 14 side. However, a support shaft is provided on the arm portion 12b side, and a lug is formed on the protection plate 14 side to form a bearing hole. May be provided. When the protective plate 14 is not provided with the elastic piece 14b, for example, a groove is provided in the cover 2 and the upper end of the protective plate 14 is inserted into this groove, so that the protective plate 14 can be held in the closed position. It is.

FIGS. 5A and 5B show an embodiment in which a flexible portion is provided on the protection plate 14, wherein FIG. 5A is a front view of the protection plate, and FIG. 5B is a side view thereof. That is, the protection plate 14 is provided with a flexible portion 14c which is bent in a waveform near the support shaft 14a in order to facilitate the elastic deformation of the protection plate 14 itself. If such a flexible portion 14c is provided, the protection plate 14 is deformed by the flexible portion 14c in addition to the rotation about the support shaft 14a when the internal pressure of the blocking portion is increased, thereby discharging the arc gas more smoothly.

Embodiment 2 FIG. 6 shows an embodiment in which a cut is made in a protective plate. FIG. 6 (A) is a front view of the protective plate, and FIG. 6 (B) is a longitudinal sectional view thereof. In FIG. 6, an H-shaped notch 16 is formed in the protection plate 14 as shown in the figure, and valve bodies 14d and 14e which open up and down are formed in the plate surface. Here, in FIG. 6, the lower valve element 14e is longer than the upper valve element 14d, and in the illustrated case, the valve element 14e is almost four times as long as the valve element 14d. Also, as shown in FIG.
The thickness of the valve body 14e is uniform from the base to the tip, but the thickness of the valve body 14d is reduced only at the base 14d '. For example, the thickness of the valve body 14e and other parts of the valve body 14d is reduced. If it is 0.7 mm, the base portion 14d 'is 0.4 mm.

FIG. 7 shows a main part of a circuit breaker to which the protection plate 13 of FIG. 6 is attached. The protection plate 14 is gripped by inserting both edges into grooves provided in the case 1 and the cover 2 of the circuit breaker. Then, when the internal pressure of the interrupting section increases due to the current interruption, the valve element 14
d and 14e open elastically and discharge the arc gas as indicated by the arrow. At this time, since only the valve elements 14d and 14e in the plate surface are deformed when the arc gas is discharged, both edge portions thereof can be gripped over the entire height and easily come off and jump due to an increase in the internal pressure of the cutoff portion. There is no. Further, since the valve bodies 14d and 14e open up and down, the arc gas is discharged toward the power supply side of the circuit breaker as can be seen from FIG. Therefore, the arc gas is discharged to the upper surface of the cover 2, and no interphase short circuit occurs due to the arc gas intersecting between adjacent poles.

Further, the lower valve element 14e covers the terminal screw 18 on the power supply side as shown in the figure. As a result, the arc gas is guided by the valve element 14e, passes above the terminal screw 18, and is not directly blown to the terminal screw 18. Therefore, it is possible to prevent the terminal screw 18 from being damaged by being exposed to the high-temperature arc gas and from being stuck due to the adhesion of the molten material. Here, the action of gas pressure on the upper valve body 14d, which is shorter than the lower valve body 14e, is smaller than that of the valve body 14e, but the valve body 14d has a base portion 14d 'whose thickness is thinner than the valve body 14e. Therefore, when the arc gas is discharged, the opening angles of the valve bodies 14d and 14e are substantially equal, and the arc gas is discharged toward the power source in parallel with the longitudinal direction of the circuit breaker.

The protective plate 14 may be formed from a crystalline resin such as nylon. However, if the protective plate 14 is formed using a non-crystalline resin, such as polyarylate, polycarbonate, or polyetherimide, which is less elastically degraded by high temperatures, The valve function is maintained satisfactorily even after the interruption of the large current, which is more preferable for safety.

Embodiment 3 FIG. 8 is a side view of a protection plate showing an embodiment in which a valve body is formed by cutting a valve body toward a shut-off portion side. In FIG. 8, a protective plate 14 made of an arc-resistant resin such as nylon is provided with an H-shaped cut 16 in a thin flat plate portion between the left and right side edges, which is made thicker.
d and 14e are formed, and this valve element 14d, 1
4e is the front and rear dimension L on the circuit breaker side (the right side in the figure).
It is formed by bending only. The function of discharging the arc gas from the protection plate 14 is as described in the embodiment of FIG. 6, but in particular, in this embodiment, the valve bodies 14d and 14e are formed by being slightly bent in advance to the cutoff side. Even if the arc gas is excessively deformed when the arc gas is discharged and a slight permanent deformation remains after that, this deformation is offset by the bending amount L, and the valve bodies 14d and 14e project forward (to the power supply side). Never be. Therefore, this protective plate 14 has a rated current of 5 to 5.
The arc gas outlet 13 is surely closed even after the overload interruption of about six times, and also after the interruption of the large current, and there is no intrusion of foreign matter even in the subsequent continuous use.

Embodiment 4 FIG. 9 is a longitudinal sectional view showing an embodiment in which the valve bodies 14d and 14e of the protective plate 14 shown in FIG. 6 are gradually reduced in thickness from the base to the tip. . According to such an embodiment, as shown by the dashed line, the amount of deformation of the distal end portions of the valve bodies 14d and 14e increases, thereby facilitating discharge of the arc gas. It is possible to increase the thickness of the base portions of the large valve bodies 14d and 14e. For example, instead of making the plate thickness of the valve element 14e in Embodiment 4 equal to 0.7 mm, even if the base portion is 1 mm and the tip portion is 0.4 mm, the increase in internal pressure can be made substantially the same.

Embodiment 5 FIG. 10 shows an embodiment of a gas stopper plate 19 which is arranged so as to be superimposed on the inside of the protective plate 14 shown in FIG. 6 or FIG. 9, and FIG. FIG. 1B is a longitudinal sectional view thereof. The gas stopper plate 19 is a flat plate having a thickness of, for example, 0.5 mm and includes a central gas stopper portion 19a and a pair of mounting portions 19b rising on both sides thereof. Manufactured from insulation. The gas stopper plate 19 is placed inside the protective plate 14 as shown by a chain line in FIG. 6 (A), and is sandwiched between the protective plate 14 and the front end face of the side plate 17a of the insulator 17 as shown in FIG. Is held. In this state, the gas stopper 19a
Covers the bottom of the protection plate 14 from the root of the valve body 14e to a certain height range, and in the illustrated case, to approximately the same height as the upper surface of the terminal screw 18.

According to this embodiment, the arc gas containing a large amount of molten material immediately after the contacts 7 and 8 are separated once collides with the gas stopper plate 19 and is discharged to the outside. The amount discharged to the outside by being captured on the stopper plate 19 is reduced. Since the melt in the arc gas is conductive, the risk of interphase short-circuit increases when a large amount of melt is discharged. However, by capturing this melt with the gas stopper 19, the effect of preventing interphase short-circuit is further improved. Can be enhanced.

[0033]

According to the present invention, the protection plate is connected to the partition wall via the support shaft, or is held by the insulating container over the entire height of both edges, so that the protection plate can be easily formed even when the internal pressure rises when current is interrupted. It does not come off and jump out. Also, at the time of gas discharge, since the support shaft is widely opened at the fulcrum or both up and down, the discharge direction of the arc gas is not biased toward the cover side, and therefore the arc gas discharged from each pole crosses each other on the upper surface of the cover, and there is a risk of generating a short circuit between phases. There is no. In that case,
If the lower valve body is made longer than the upper valve body so that the lower valve body that opens when discharging the arc gas covers the terminal screw on the power supply side, the arc gas is directly blown and the terminal screw is damaged. It is prevented from receiving.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a circuit breaker according to a first embodiment of the present invention.

FIG. 2 shows a protection plate in FIG. 1, (A) is a front view,
(B) is a side view thereof.

3A and 3B show partition walls in FIG. 1, wherein FIG.
(B) is a side view thereof, and (C) is a right front view thereof.

FIG. 4 is a view showing a discharge state of arc gas in the circuit breaker of FIG. 1;

FIG. 5 shows a different embodiment of the guard plate in FIG. 1,
(A) is a front view, (B) is the side view.

6A and 6B show a second embodiment of the present invention, wherein FIG. 6A is a front view of a protection plate, and FIG. 6B is a longitudinal sectional view thereof.

7 is a vertical sectional view of a main part of a circuit breaker provided with the protection plate of FIG. 6;

FIG. 8 shows a third embodiment of the present invention, wherein (A) is a front view of a protection plate, (B) is a side view thereof, and (C) is C of (A).
It is sectional drawing which follows the -C line.

FIG. 9 is a longitudinal sectional view of a protective plate according to a fourth embodiment of the present invention.

FIG. 10 shows a fifth embodiment of the present invention, in which (A) is a front view of a gas stopper plate, and (B) is a longitudinal sectional view thereof.

FIG. 11 is a longitudinal sectional view of a main part of a circuit breaker showing a conventional example.

12 is a cross-sectional view of a main part along line XII-XII in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Cover 3 Fixed contact 4 Opening / closing mechanism 5 Movable contact 6 Arc extinguishing chamber 12 Partition wall 12b Arm 13 Arc gas discharge port 14 Protective plate 14a Support shaft 14b Elastic piece 14c Flexible part 14d Valve 14e Valve 14g Valve 14f Valve 16 Notch 18 Terminal screw 19 Gas stop plate

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koji Asakawa 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Masao Miura 1, Tanabe Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. (56) References JP-A-57-824 (JP, A) JP-A-53-114076 (JP, A) JP-A-3-114117 (JP, A) JP-A-4- 131844 (JP, A) Fully open 1988-91141 (JP, U) Fully open 1988-93043 (JP, U) Fully open, 2-64134 (JP, U) Really open, 61-176756 (JP, U) J. 45-5082 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 73/18 H01H 73/06

Claims (7)

(57) [Claims] An arc gas outlet is provided in front of a cut-off portion comprising a fixed contact fixed to a case and a movable contact driven by an opening / closing mechanism, and the arc gas outlet is provided by a protective plate made of an insulating material. In the circuit breaker to be closed, a pair of left and right arms extending toward an arc gas discharge port are integrally formed on a partition wall of an insulator provided between the breaking portion and the opening / closing mechanism, and the arm is provided with the protection plate. A circuit breaker, which is rotatably connected via a connector. 2. The circuit breaker according to claim 1, wherein an elastic piece is integrally formed on the protection plate, and the elastic piece is engaged with an arm of the partition to hold the protection plate in a closed position. 3. The circuit breaker according to claim 2, wherein a flexible portion is formed near the support shaft of the protection plate. 4. An arc gas outlet is provided in front of a cut-off portion comprising a fixed contact fixed to a case and a movable contact driven by an opening / closing mechanism, and the arc gas outlet is provided by a protective plate made of an insulating material. In the circuit breaker to be closed, a cut is made in the protective plate to form a double-sided valve body in the plate surface, and the lower valve body is connected to the upper front side.
The lower side which is longer than the valve body and is opened when discharging arc gas
So that the valve body covers the terminal screw on the power supply side,
The thickness of the base of the upper valve body is reduced by the lower valve.
The opening angle of the lower and upper valve body, thinner than the body
Circuit breakers characterized in that they are substantially equal to each other . 5. The circuit breaker according to claim 4, wherein said valve body is formed by bending the valve body toward a breaking portion. 6. The circuit breaker according to claim 4, wherein the thickness of the valve body is gradually reduced from a root portion to a tip portion. 7. A protection plate according to claim 4 , wherein a gas stopper plate made of an insulating material covering a predetermined height range from a root portion of the lower valve body to the upper portion is disposed inside the protection plate. Circuit breaker.