JP2003189466A - Surge protector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surge protector which can suppress a surge voltage more significantly and more quickly. <P>SOLUTION: A varistor and a pnpn device 12 are connected in series to each other. A breakover voltage as a whole is approximately equal to the sum of the varistor voltage of the varistor and the breakover voltage of the pnpn device 12. If a surge is applied, the pnpn device 12 is short-circuited by the breakover voltage as a whole. The surge voltage can be suppressed by the voltage characteristics of the varistor which is smaller than the breakover voltage as whole. The surge voltage can be suppressed more significantly and, further, by the high responsiveness of the pnpn device 12, the surge voltage can be suppressed more quickly. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surge protection device having a voltage limiting element.

[0002]

2. Description of the Related Art Conventionally, a fuse as a fuse body and a voltage limiting element having a non-linear voltage-current characteristic have been used for surge protection of circuits requiring high reliability such as telephones and computer facilities. A surge protection device is used in which a metal oxide varistor of 3 is connected in series.

Here, the metal oxide varistor is used, for example, for a normal AC 100V commercial power source because an overcurrent frequently flows and is not deteriorated by noise generated when starting and stopping a protected circuit. In this case, a varistor voltage of about 240V is selected.

The surge protection device is inserted and connected between single-phase commercial power supply lines to which the protected circuit is connected, or between the commercial power supply line, each power supply line, and the ground.

Thereafter, for example, when a lightning surge or the like flows into the commercial power supply line, the metal oxide varistor has a low resistance to the surge voltage, and a large current flows to absorb energy.

Further, the metal oxide varistor is damaged and short-circuited when energy exceeding the allowable value passes,
It may be necessary to immediately disconnect this metal oxide varistor from the protected circuit because it may cause a secondary failure, in which case the fuse will overcurrent when the metal oxide varistor is damaged. Then, the metal oxide varistor is cut off from the protected circuit.

However, in this surge protection device,
Since the voltage between the terminals of the metal oxide varistor increases due to the surge current, the surge voltage is not sufficiently suppressed, and the voltage of the power supply to which the metal oxide varistor is connected fluctuates. As a result, for example, when the protected circuit is a circuit such as a semiconductor integrated circuit which is sensitive to fluctuations in the power supply voltage, the protected circuit may be adversely affected.

A surge protection device in which a metal oxide varistor and a so-called gas arrester as a surge protection element are connected in series is also used.

In this surge protection device, the overall breakover voltage is the sum of the varistor voltage of the metal oxide varistor and the breakover voltage of the gas arrester. Therefore, for example, when used between ordinary commercial power supplies of 100 V AC, the metal oxide varistor and the gas arrester are selected so that the overall breakover voltage is 240 V or more, as in the above-mentioned surge protection device.

In this surge protection device, for example, when a lightning surge or the like flows into the commercial power supply line, the terminal voltage of the gas arrester exceeds the discharge start voltage of the gas arrester due to the lightning surge, and the gas arrester is arced. To start. As a result, the surge voltage is reduced to, for example, several tens of V when passing through the gas arrester, so that the surge voltage can be suppressed to a lower voltage characteristic of the metal oxide varistor. At this time, the metal oxide varistor used in this surge protection device has a smaller varistor voltage than the metal oxide varistor used in the surge protection device in which the fuse and the metal oxide are connected in series as described above. Can be suppressed.

However, in this surge protection device,
It takes several microseconds from when the surge voltage is applied to the gas arrester to reach the arc discharge area of this gas arrester, so the operation response speed is relatively slow. May not protect electrical equipment from

[0012]

As described above, in the surge protection device in which the fuse and the metal oxide varistor are connected in series, the surge voltage is not sufficiently suppressed, and the metal oxide varistor and the gas arrester are connected in series. The surge protection device connected to has a problem that the operation response speed until the suppression of the surge voltage is relatively slow.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a surge protection device capable of suppressing a surge voltage at a higher level and at a higher speed.

[0014]

According to a first aspect of the present invention, there is provided a surge protective device including a voltage limiting element and a surge protective element connected in series with the voltage limiting element and short-circuited by a surge.

By connecting the voltage limiting element and the surge protection element that is short-circuited by the surge in series, the total breakover voltage is the sum of the limiting voltage of the voltage limiting element and the breakover voltage of the surge protection element. Is almost equal to. As a result, when a surge flows in, the surge protection element is short-circuited at the overall breakover voltage, and the surge voltage is suppressed by the voltage characteristic of the voltage limiting element that is smaller than the overall breakover voltage.

According to a second aspect of the surge protection device of the first aspect, in the surge protection device of the first aspect, a fuse body connected in series with the voltage limiting element and the surge protection element, and a notification in conjunction with the fusing of the fuse body are provided. And means for activating the means.

When the voltage limiting element is damaged by the surge and an overcurrent flows in, the fuse body connected in series with the voltage limiting element is blown by the overcurrent, and the starting means is interlocked with the fusing of the fuse body. Activates the notification means. As a result, damage of the voltage limiting element and fusing of the fuse body can be easily and surely found by the notification means.

According to a third aspect of the present invention, in the surge protective device according to the second aspect, the voltage limiting element, the surge protective element, the fuse body and the starting means are integrally formed and can be attached to and detached from the protected circuit. There is something.

The voltage limiting element, the surge protection element,
Since the fuse body and the starting means are integrally formed and can be attached to and detached from the protected circuit, they can be easily replaced after the voltage limiting element is broken and the fuse body is blown.

A surge protective device according to a fourth aspect is the surge protective device according to any one of the first to third aspects,
The voltage limiting element is a varistor.

Since the voltage limiting element is a relatively inexpensive varistor, the manufacturing cost is suppressed.

A surge protection device according to a fifth aspect is the surge protection device according to any one of the first to fourth aspects.
The surge protection element is a PNPN element.

The surge protection element is a relatively inexpensive P
Since it is an NPN element, manufacturing cost is suppressed.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration of an embodiment of the surge protection device of the present invention will be described below with reference to FIGS.

1 to 8, reference numeral 1 is a surge protection device. This surge protection device 1 has a hollow case body 2 having a substantially rectangular box shape. The case body 2 is configured by fitting an upper case 3 and a lower case 4 each formed of an insulating synthetic resin. Further, a first partition wall portion 3a is formed in a substantially central region in the longitudinal direction of the upper case 3 so as to project downward in the height direction of the upper case 3, that is, vertically downward. On the other hand, in the substantially central region of the lower case 4, the second partition wall 4a projects upward in the thickness direction of the lower case 4, that is, vertically upward, and extends along the width direction of the lower case 4. About half the width dimension of.

The first partition 3a and the second partition 4a are joined together with the upper case 3 fitted in the lower case 4, and the voltage limiting element housing 5 and the fuse body housing 6 are connected to each other. The case body 2 is formed adjacent to the width direction of the case body 2. The fuse body housing portion 6 is formed so as to be narrower than the voltage limiting element housing portion 5.

Further, in the voltage limiting element accommodating portion 5, a substantially circular plate-shaped varistor 11 as a voltage limiting element is accommodated so that the thickness direction thereof is substantially along the width direction of the case body 2. Has been done. The varistor 11 is, for example, a zinc oxide (ZnO) varistor as a metal oxide varistor and has a voltage-current characteristic as shown in FIG. here,
V ₁ is the varistor voltage of this varistor 11. further,
The varistor 11 has a varistor body 11a having a substantially disc shape.

Here, the varistor main body 11a is formed by sandwiching a ceramic body (not shown), which is formed into a disc shape by firing powder mainly containing zinc oxide, between a pair of electrodes (not shown). , A pair of electrodes (not shown) are provided with terminals 11b and 11c for external connection, respectively.
Is provided so as to protrude substantially along the longitudinal direction of.

Further, on the protruding side of the terminals 11b and 11c of the varistor 11 at one end in the width direction inside the case body 2, a substantially rectangular PNPN current control type bidirectional silicon thyristor as a surge protection element, that is, a so-called PNPN. element
Twelve are arranged. The PNPN element 12 has a voltage-current characteristic as shown in FIG. 7, and is arranged with its longitudinal direction substantially along the width direction of the case body 2 as shown in FIG. Here, V ₂ is a breakover voltage of the PNPN element 12.

On the upper surface of the PNPN element 12, plate-shaped external connection terminals 12a, 12b, 12c are formed so as to project above the PNPN element 12. These terminals 12a, 12c
Are P on both ends of the PNPN element 12, not shown.
The layer 12 and the N layer (not shown) are connected, and the terminal 12b is connected to the P layer (not shown) in the center of the PNPN element 12. Further, the terminal 11b of the varistor 11 is electrically connected to the terminal 12a by welding, for example, with solder or the like.

The tip of the terminal 12c of the PNPN element 12 is electrically connected to one end of the substantially rectangular plate-shaped power supply terminal 13 by soldering, for example, toward the side of the PNPN element 12. ing. Here, one end of the power supply terminal 13 to which the terminal 12c of the PNPN element 12 is connected is bent substantially vertically, and the power supply terminal 13 is formed in a substantially L-shape in cross section and is provided on the upper surface of the lower case 4. Partially locked. Furthermore, this power supply terminal in the lower case 4
A terminal hole 14 is provided on the lower side of the lower portion 13 so as to penetrate in the thickness direction, and the power supply terminal 13 is fitted into the terminal hole 14 and protrudes to the outside of the lower case 4.

On the other hand, in the fuse body accommodating portion 6, a substantially cylindrical fuse tube 15 as a fuse protector is provided in the longitudinal direction of the case body 2 by the first partition wall portion 3a and the second partition wall portion 4a. The fuse tube 15 is housed in a sandwiched manner and is partitioned by the fuse tube 15 into the fuse body housing portion 6 to form a display chamber 21. Here, the display chamber in the axial direction of the fuse tube 15
A substantially bottomed cylindrical fitting body 22 having an inner diameter dimension substantially equal to the outer diameter dimension of the fuse tube 15 is fitted to one end on the side opposite to 21. Further, a through hole 22a is provided in a substantially central region of the bottom surface of the fitting 22.

Further, a relay terminal 23 bent in a crank shape is attached to the second partition wall 4a so as to face one end of the fitting 22 opposite to the display chamber 21.
Further, a fitting insertion hole 23a is provided on the upper side of the second partition wall portion 4a in the thickness direction of the second partition wall portion 4a, and one end of the relay terminal 23 is fitted into the fitting insertion hole 23a. Are locked. Then, in the fuse tube 15, a fuse wire 24 as a fuse body inserted substantially along the central axis of the fuse tube 15 and accommodated in the fuse tube 15 is inserted, and the relay terminal 23 is passed through the through hole 22a to the relay terminal 23, for example. It is welded with solder. The fuse wire 24 is formed in a thin wire shape, for example, from a low melting point alloy containing silver (Ag) as a main component.

Further, a fuse wire in the fuse tube 15
The circumference of 24 is filled with, for example, silica sand 25 as an arc extinguishing member.
Has been done. Furthermore, in the center area of the relay terminal 23,
The connecting part 26 of the shape is cut and raised, and this connecting part 26 is formed.
The terminal 11c of the varistor 11 is melted with, for example, solder.
It is worn and electrically connected. As a result,
The varistor 11, the PNPN element 12, and the
Cable 24 is connected in series, and surge protector 1 is shown in FIG.
It has such a voltage-current characteristic. Where V_ThreeIs
This is the breakover voltage of the entire surge protection device 1.
This V_ThreeIs V ₁And V_TwoIs almost equal to the sum of
It

Further, below the fuse tube 15, a load terminal 30 having a substantially rectangular plate shape, one end of which is bent substantially vertically, that is, a substantially L-shaped cross section, is provided. It is attached by engaging with the partition wall 4a.
Further, below the display chamber 21 in the lower case 4, a terminal hole 31 is provided so as to penetrate in the thickness direction of the lower case 4. The load terminal 30 is fitted into the terminal hole 31 and protrudes to the outside of the lower case 4 substantially along the outer surface of the second partition wall portion 4a which is the inner wall of the display chamber 21. The lower end of the load terminal 30 projects to a position substantially equal to the lower end of the power supply terminal 13.

As shown in FIG. 2, a display window 32 is provided on the upper side of the display chamber 21 so as to penetrate the case body 2. Inside the display chamber 21, conductive and elastic materials are provided. A movable piece 33 is provided as the fuse blown display means. In the movable piece 33, the display portion 33a is substantially vertical on one end side,
That is, the spring portion 33b is formed to have a substantially L-shape in cross section, and the other end has an elastic spring portion 33b, which is formed to be substantially U-shaped in cross section on the same side as the display portion 33a toward the one end side. There is. Further, the movable piece 33 is arranged such that the end on the display portion 33a side faces one end of the fuse tube 15 on the side facing the display chamber 21, and the spring portion 33b is brought into contact with the side surface of the load terminal 30. Are electrically connected.

On the display portion 33a side of the movable piece 33, one end of the fuse wire 24 is fused and electrically connected by, for example, solder. Due to the fuse wire 24, the movable piece 33 is elastically deformed toward the end portion of the fuse tube 15 in the direction of being pulled by the fuse wire 24, against the elasticity of the movable piece 33 itself. As a result, the display portion 33a of the movable piece 33 is retracted from the display window 32 into the case body 2, and when the fuse wire 24 is blown and cut, the movable piece 33 itself has an elastic force. 33 is restored, and the display unit 33a moves to a position where the display window 32 is closed, that is, a position indicated by a chain double-dashed line in FIG.

Further, in the lower case 4 in the display room 21,
A third partition 34 is formed so as to project upward in the thickness direction of the lower case 4, and a contact chamber 35 is defined in the display chamber 21 by the third partition 34. The lower case 4 below the contact chamber 35 is provided with a through hole 35a penetrating the lower case 4 in the thickness direction.
A substantially rectangular plate-shaped alarm terminal 41 is fitted and inserted in a and projects to the outside of the lower case 4.

Here, the alarm terminal 41 includes a conductive and elastic elongated first alarm terminal 41a and a conductive elongated second alarm terminal 41b as insulating members. Are insulated from each other through the alarm part insulating plate 41c and integrally joined. In addition, these first alarm terminals 41
The inner ends of the case body 2 between the a and the second alarm terminal 41b are free ends facing each other with a predetermined gap. Further, the alarm terminal 41 has a smaller amount of protrusion to the outside of the case body 2 than the power supply terminal 13 and the load terminal 30.

A substantially spherical contact portion 42 is integrally formed at the free end of the first alarm terminal 41a, and the contact portion 42 forms the third partition wall portion 34 in the longitudinal direction of the case body 2. It penetrates and projects to the display room 21 side. The alarm terminal 41 and the contact portion 42 constitute the starting means 43, and when the movable piece 33 is restored by melting the fuse wire 24, the movable piece 33 pushes the contact portion 42 into the inside of the contact chamber 35 and the first contact portion 42 is pushed. The alarm terminal 41a and the second alarm terminal 41b are short-circuited. As a result,
An alarm circuit (not shown) such as a buzzer is activated in association with the blowout of the fuse wire 24.

The surge protector 1 is composed of the varistor 1
1, the PNPN element 12, the fuse wire 24, etc. are integrally formed and housed in the case body 2, so that a so-called plug-in type can be attached to and detached from a protected circuit (not shown) through a holder (not shown). There is.

Next, the operation of the above embodiment will be described.

First, the surge protective device 1 is attached to a holder (not shown) connected to a protected circuit (not shown).
At this time, the power supply terminal 13, the load terminal 30, and the alarm terminal 41
Are inserted and attached to predetermined terminals of a holder (not shown).

In this state, if a surge voltage exceeding the breakover voltage V ₃ is about to flow into the protected circuit (not shown), the PNPN element 12 reacts at high speed and the PNPN
Element 12 is short circuited.

Then, since the varistor 11 is connected in series with the PNPN element 12, the resistance value of the entire surge protection device 1 becomes substantially equal to the resistance value of the varistor 11, so that a voltage smaller than the breakover voltage V _3. The varistor 11 having the characteristic suppresses the surge voltage due to the voltage characteristic of the varistor 11.

When energy larger than the predetermined energy flows into the varistor 11 due to the surge, the varistor 11
Is short-circuited and damaged, and an overcurrent flows through the surge protective device 1.

Then, the fuse wire 24 is blown by this overcurrent, and the varistor 11 is cut off from the protected circuit (not shown).

At this time, the movable piece 33 is restored by elastic force,
The display portion 33a of the movable piece 33 closes the display window 32 of the display chamber 21 and transmits the blowout of the fuse wire 24 to the outside.

Further, the contact portion 42 is restored by the restoration of the movable piece 33.
Is pushed inward of the contact chamber 35 by the movable piece 33 and elastically deformed, and the first alarm terminal 41a becomes the second alarm terminal 41b.
Contact with and short-circuit.

As a result, an alarm circuit (not shown) is activated and the blowout of the fuse wire 24 is transmitted.

In this case, the damaged surge protective device 1 is removed from the holder (not shown) and replaced with another undamaged surge protective device 1.

As described above, according to the one embodiment, the breakover voltage V ₃ is changed to the varistor voltage V ₃ by connecting the varistor 11 and the PNPN element 12 in series.
_It becomes approximately equal to the sum of ₁ and the breakover voltage V ₂ . As a result, if this breakover voltage V ₃ is made substantially equal to the breakover voltage of a conventional surge protection device not shown, for example, the surge voltage is applied to a normal voltage while operating similarly to the conventional surge protection device not shown. , The PNPN element 12 is short-circuited and the breakover voltage V ₃
The surge voltage can be suppressed by the voltage characteristic of the varistor 11 which is smaller than that. As a result, the surge voltage can be further suppressed.

Further, since the PNPN element 12 has high responsiveness, the surge voltage can be suppressed at a higher speed.

Further, when the varistor 11 is damaged by a surge, the fuse wire 24 is blown by an overcurrent, and the activating means 43 activates an alarm circuit not shown in conjunction with the fusing of the fuse wire 24, so that the varistor 11 is damaged. Also, the fusing of the fuse wire 24 can be easily and surely found.

Since the surge protection device 1 is a plug-in type, it can be easily replaced.

Further, by notifying the blowout of the fuse wire 24 from the display window 32 through the display portion 33a of the movable piece 33, the blowout of the fuse wire 24 can be easily confirmed visually and the structure is relatively simple. The productivity can be improved by surge notification device 1.

Furthermore, by filling the periphery of the fuse wire 24 inside the fuse tube 15 with silica sand 25, the fuse wire 24 can be extinguished by the silica sand 25, and metal vapor generated when the fuse wire 24 is blown, etc. From the display window 32 to the case body 2
Can be prevented from going outside.

Further, since the varistor 11 and the PNPN element 12 are relatively inexpensive, the manufacturing cost can be suppressed.

The PNPN element 12 is controlled by the terminal
Since it is only necessary to connect the two terminals 12a and 12c, it is possible to easily manufacture and improve the manufacturability.

In addition, in the above-mentioned one embodiment, the movable piece
The display unit 33a does not have to be provided for the 33 as long as the blowout of the fuse wire 24 can be electrically notified by an alarm circuit (not shown).

Alternatively, if the blowout of the fuse wire 24 can be reliably notified by the display portion 33a of the movable piece 33, it is not necessary to connect it to an alarm circuit (not shown) or the like.

The fuse tube 15 may be expanded, for example, toward the relay terminal 23 side. In this case, it is possible to prevent metal vapor or the like generated when the fuse wire 24 is blown out from the display window 32 to the outside of the case body 2. Further, in this case, the silica sand 25 may be omitted.

Further, the voltage limiting element need not be the varistor 11, and the surge protection element need not be the PNPN element 12 as long as it responds at high speed.

[0064]

EXAMPLE An example of measurement of the voltage suppression effect by the surge protective device according to the above embodiment will be described below with reference to FIGS.
This will be described with reference to Table 1, Table 1 and Table 2.

In the present embodiment, the power supply voltage is AC 10
ZNRV151U (manufactured by Matsushita Electric Industrial Co., Ltd.) having a varistor voltage V ₁ of 150 V was used as the varistor 11. Further, the PNPN element 12 has a breakover voltage V ₂
KT40N14 of 130V (made by Shindengen Industry Co., Ltd.)
A 10 A alarm fuse (manufactured by Daito Communication Equipment Co., Ltd.) was used for the fuse wire 24.

Then, the voltage suppression characteristic of the surge protective device 1 of this embodiment was measured. The result is shown in FIG. In addition,
As a first comparative example, a varistor with a varistor voltage V ₁ of 240 V is used, and as a second comparative example, a varistor voltage V _{1 is used.}
A varistor of 150 V was used. In addition, the voltage drop of the fuse wire 24 is extremely small compared to the varistor 11 and the PNPN element 12, and is therefore omitted.

As shown in FIG. 9, the surge protective device 1 of the present embodiment has substantially the same voltage suppression characteristic as that of the first comparative example when the current is small, but when the current is increased, the PNP is increased.
It can be seen that the N element 12 is short-circuited and has a voltage suppression characteristic substantially equal to that of the second comparative example.

Next, in the surge protection device 1 of the present embodiment, 8
A surge current waveform of / 20 μs was applied from 2 kV to 14 kV while changing the charging pressure by 2 kV, and the current value and voltage value were measured. The results are shown in FIG. 10 and Table 1. As a third comparative example, the varistor voltage V ₁ is 2
A 40V varistor and a 10A alarm fuse were connected in series.

[0069]

[Table 1]

As shown in FIG. 10 and Table 1, the surge protective device 1 of the present embodiment responds to a relatively high speed surge voltage, and the voltage is 140 V higher than that of the third comparative example at each charging voltage. It turns out that it can be suppressed more. Further, when the charging voltage becomes 14 kV, the fuse wire 24 is blown out, and it is prevented that the varistor 11 which is damaged by the surge voltage and short-circuited short-circuits the power supply line (not shown) to cause a secondary failure. ing.

Next, using this embodiment and the third comparative example, a surge current waveform of 10/1000 μs was measured at 4.3 k.
The results of measuring the current value and the voltage value while changing the charging pressure from V to 17 kV are shown in FIG. 11 and Table 2.

[0072]

[Table 2]

As shown in FIG. 11 and Table 2, 10/1
It can be seen that even in the case of a surge current waveform of 000 μs, the voltage of this example is suppressed by about 120 V as compared with the third comparative example.

In the above embodiment, the varistor 11 is used.
The varistor voltage V ₁ is selected to be larger than the peak value of the power supply voltage. This is because the PNPN element 12 is short-circuited by the surge voltage and then the varistor is generated due to the follow current of the power supply voltage waveform.
This is to prevent the varistor 11 from being damaged due to a large current flowing through the varistor 11 and the temperature of the varistor 11 rising.

By making the varistor voltage V ₁ of the varistor 11 larger than the peak value of the power supply voltage waveform and closest to this peak value, the voltage suppressing effect can be maximized and the surge voltage is protected against surge. After passing through the device 1, it is possible to reliably prevent a follow-up flow.

[0076]

According to the surge protection device of the first aspect, since the voltage limiting element and the surge protection element short-circuited by the surge are connected in series, the overall breakover voltage is limited by the voltage limiting element. It is approximately equal to the sum of the voltage and the breakover voltage of the surge protection device. This allows
When a surge flows in, the surge protection element is short-circuited at the overall breakover voltage, and the surge voltage can be suppressed by the voltage characteristic of the voltage limiting element that is smaller than the overall breakover voltage.

According to the surge protection device of the second aspect,
In addition to the effect of the surge protection device according to claim 1, when a voltage limiting element is damaged by a surge and an overcurrent flows in, a fuse body connected in series to the voltage limiting element is blown by the overcurrent, and the fuse body is fused. The activation means activates the notification means in conjunction with the fusing. As a result, damage of the voltage limiting element and fusing of the fuse body can be easily and surely detected by the notification means.

According to the surge protection device of claim 3,
In addition to the effect of the surge protection device according to claim 2, the voltage limiting element, the surge protection element, the fuse body and the starting means are integrally formed, and can be attached to and detached from the protected circuit.
It can be easily replaced after the voltage limiting element is broken and the fuse body is blown.

According to the surge protection device of the fourth aspect,
In addition to the effect of the surge protection device according to any one of claims 1 to 3, the voltage limiting element is a relatively inexpensive varistor, so that the manufacturing cost can be suppressed.

According to the surge protection device of claim 5,
In addition to the effect of the surge protection device according to any one of claims 1 to 4, since the surge protection element is a relatively inexpensive PNPN element, the manufacturing cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a surge protection device of the present invention.

FIG. 2 is a top view showing the same surge protective device.

FIG. 3 is a front sectional view showing the same surge protection device.

FIG. 4 is a side sectional view showing the same surge protective device.

FIG. 5 is a circuit diagram showing the same surge protection device.

FIG. 6 is a graph showing voltage-current characteristics of the voltage limiting element of the same surge protective device.

[Fig. 7] Same as above, voltage of surge protection element of surge protection device −
It is a graph which shows a current characteristic.

FIG. 8 is a graph showing voltage-current characteristics when a surge protection element and a voltage limiting element of the same surge protection device are connected in series.

FIG. 9 is a graph showing the limiting voltage characteristic of the voltage limiting element in one embodiment of the same surge protective device.

FIG. 10 is a graph showing voltage suppression characteristics in an example of the same surge protection device.

FIG. 11 is a graph showing another voltage suppression characteristic in one embodiment of the same surge protection device.

[Explanation of symbols]

1 Surge protection device 11 Varistor as voltage limiting element 12 PNPN element as surge protection element 24 Fuse wire as fuse body 43 Starting method

Claims (5)

[Claims] 1. A surge protective device comprising a voltage limiting element and a surge protective element connected in series to the voltage limiting element and short-circuited by a surge. 2. A fuse body connected in series with the voltage limiting element and the surge protection element, and a starting means for activating the notification means in conjunction with the fusing of the fuse body. Surge protection device as described. 3. The surge protection device according to claim 2, wherein the voltage limiting element, the surge protection element, the fuse body and the starting means are integrally formed and can be attached to and detached from the protected circuit. 4. The surge protection device according to claim 1, wherein the voltage limiting element is a varistor. 5. The surge protection device according to claim 1, wherein the surge protection element is a PNPN element.