JPH0740503B2 - Surge absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surge absorber, and more specifically, a gap type surge absorber and a varistor voltage are smaller than a line voltage, and a voltage nonlinear coefficient of the varistor is small. The present invention relates to a surge absorber which is electrically connected in series with a varistor.

[Prior Art] The ZnO varistor has a very large non-linearity in the voltage-current (VI) characteristic, and the voltage-current characteristic is I = kV ^α
The voltage non-linearity coefficient α expressed by
Since some of them have excellent non-linearity, they have been conventionally used for surge absorption etc. by utilizing their characteristics. However, such a ZnO-based varistor causes a leakage current when a voltage is applied, and when it is used for a long time while a voltage is always applied, the voltage-current characteristic gradually deteriorates, and finally, There is a risk of causing a short circuit due to destruction and causing thermal runaway.

Therefore, while maintaining the original excellent surge response characteristics of the ZnO-based varistor, to prevent the deterioration of the ZnO-based varistor by suppressing the occurrence of the leakage current to the minimum, and in order to avoid the danger, ZnO-based varistor. A surge absorbing device has been proposed in which a gap type surge absorbing element such as a neon tube or an arrester is electrically connected in series to a varistor. However, in this device, ZnO having a large voltage nonlinear coefficient α is
Since the system varistor was used, the ZnO varistor showing the varistor voltage higher than the line voltage was selected.

[Problems of the prior art] Since such a conventional surge absorber uses a ZnO-based varistor that exhibits a varistor voltage higher than the line voltage, the discharge start voltage and surge response voltage of the surge absorber increase. As a result, the surge response speed is inevitably slowed down, so that there is a problem that the discharge capacity of the surge absorbing device is small and therefore the capacity of the surge absorbing device for protecting the equipment is not sufficient.

[Matters of knowledge based on research] Therefore, the present inventors have obtained the following knowledge as a result of various studies in view of the above-mentioned situation.

In the surge absorber 1 in which the gap type surge absorbing element 2 and the varistor 3 shown in the equivalent circuit of FIG. 1 are electrically connected in series, the voltage-current (VI) characteristic of the varistor 3 is increased. Considering Fig. 2, which shows the figure, the voltage nonlinearity coefficient α of the varistor expressed by α = 1 / log ₁₀ (V _10mA / V _1mA ) is the VI curve from 1mA to 10mA in Fig. 2. And the gradient of the VI curve a of the varistor with a small α is the V of the varistor with a large α.
It can be seen that the slope is larger (abrupt) than the slope of the −I curve b ′.

Here, the current values of 1 mA and 10 mA are used because the definition of the voltage nonlinear coefficient, which is the basic characteristic of the varistor, is α = 1 / log ₁₀ (V
This is because it is _10mA / V _1mA ), and this meaning is a numerical representation of how the current does not change in response to changes in the current. (However, V _1mA means the voltage that appears between the varistor electrodes when a current of 1mA flows.) As the varistor 3 used by being incorporated in the above surge absorber 1, the gap type surge absorber is used. Since it is necessary to avoid damage to the element, it is naturally necessary to select a varistor that exhibits a varistor voltage (V _1mA ) so that a follow current does not occur. For that purpose, the line voltage _VL and the VI curve b The line current I _{L at the} point of intersection with ′ must be smaller than the arc maintaining current L _A of the gap type surge absorbing element 2, that is, I _L <I _A. The ZnO-based varistor used in the prior art has a characteristic as shown by the VI curve b, but if I _L <I _A , no follow current is generated. Therefore, even with a ZnO-based varistor, the varistor voltage V _O V
'Down to the curve b' _O it is possible to use those V-I characteristics, such as.

Further, regarding the varistor showing the VI curve a having a larger slope between 1 mA and 10 mA than the VI curve b ′, that is, the varistor having a small α, the line voltage V _L
And the current I _L ′ at the point where the V-I curve a intersects V _{1mA to} V
_Since the voltage change during _{10 mA} is large, it is smaller than I _L , that is, I _L ′ <I _L. Therefore, the VI curve a
Was allowed to translate to the right 'until, I _L other words' V-I curve a is until _{I L (I L' = I} L <I A), V-I
It is possible to reduce the varistor voltage V _O ′ of the varistor showing the curve a to V _O ″.

Focusing on the above points, the present inventors have found a varistor having a varistor voltage smaller than the line voltage under the condition of I _L <I _A and a voltage nonlinear coefficient α in the range of 1 <α <20. When incorporated as the varistor 3 of the surge absorber 1, the follow-up current is not only prevented as in the conventional surge absorber, but the discharge start voltage is low and the surge response voltage is low, resulting in a surge response. It has been found that a surge absorber having a high speed and a low residual voltage after a surge response, that is, a surge absorber having excellent surge absorption characteristics can be obtained.

[Object of the Invention and Structure of the Invention] The present invention has been made on the basis of the above findings, and provides an excellent surge absorbing device having surge absorbing characteristics, that is, a follow current is prevented and a surge response voltage and a residual voltage are low. For the purpose of providing, in a surge absorbing device in which a gap type surge absorbing element and a varistor are electrically connected in series, a varistor voltage of the varistor is smaller than a line voltage and a voltage non-linear coefficient of the varistor. α is in the range of 1 <α <20,
Further, the varistor is TiO ₂ type, SrTiO ₃ type, SiC type or SnO _{2 type.}
The present invention relates to the above surge absorber, which is a varistor selected from the system.

[Detailed Description of the Invention] As a gap type surge absorbing element used in the present invention, a pair of electrodes are provided close to each other in a glass tube in which low-pressure neon is enclosed together with a small amount of argon. Reducing the peak value of abnormal voltage by discharging a part or the rest of the energy, such as a neon tube or a gas tube arrester in which a pair of electrodes facing each other in the gas enclosed in the tube form a protective gap. Any conventional gap-type surge absorbing element in which a gap is formed in the electrode tube in order to make it possible to use, and the discharge start voltage may be higher than the maximum circuit voltage of the circuit in which the element is incorporated, It is appropriately set according to the type and characteristics of the circuit.

The varistor used in the present invention can be any type of varistor as long as the varistor voltage is smaller than the line voltage and the voltage nonlinear coefficient α is in the range of 1 <α <20. , Preferably T _i O ₂ system, S _r T _i
O ₃ type, S _i C type and S _n O ₂ type varistors are used, and it is preferable that α is usually 5 to 10.

In the present invention, the voltage nonlinear coefficient α of these varistors is
The reason for limiting the numerical value in the range of 1 <α <20 is that the varistor such as zinc oxide is usually used to prevent the follow current when the α value is 50 or more. However, the voltage of the varistor used in the present invention is As for the non-linear coefficient α, by using one having an α value larger than the linear resistance (α = 1) and smaller than the above-mentioned 50, the surge response voltage and the residual voltage are significantly lowered together with the follow current prevention effect. The excellent effect of the present invention that it can be expected is expected. However, in order to carry out the present invention more effectively (that is, to use a varistor having a varistor voltage lower than the line voltage, which no one has so far omitted), the α value is set to be several steps smaller than 50. Yes, especially when α is set to a value of 10 or 20, a varistor with a varistor voltage several steps lower than the line voltage can be used. In other words, if the voltage nonlinear coefficient α is 20 or more, the varistor V _1mA
Since there is no big difference between V and _{10 mA} , even if a varistor having a varistor voltage lower than the line voltage is used, a sufficient effect cannot be obtained. Also, with an α value of 1, it is a linear resistance and has a large surge resistance. And the residual voltage is high, and therefore the effect of the present invention cannot be obtained.
The α value must be 1 or more. Also, since the α value of the varistor with a small α that actually exists is in this range, 1
Although <α <20 is set, it is preferably 5 <α <10 in practical use.

To connect the gap type surge absorbing element and the varistor, any means may be used as long as they are electrically connected, but it is convenient to use caulking, soldering, wiring with a board, or the like. .

In assembling the surge absorbing device of the present invention, in order to stabilize the overall shape, the surge absorbing device is generally covered with an insulating case or a covering material, a heat-shrinkable tube, or the like, or further filled inside the covering member. It is preferable to fill the material.

INDUSTRIAL APPLICABILITY The surge absorbing device of the present invention can be incorporated in a wide range of electrical devices and equipment circuits, and is particularly advantageously used between equipment and equipment lines having a power supply line, and between line and ground.

EXAMPLES Next, the present invention will be described with reference to examples.

Example 1 A neon tube 5 and a varistor 4 which are electrically connected in series by caulking 6 are fixed on a cylindrical insulating base 7 as shown in the longitudinal sectional view of FIG. 3, and An experiment was performed by applying a surge to a surge absorber having a structure in which the outside of the base was covered with a heat-shrinkable tube 8.

Varistor used was alpha = 10, the varistor voltage = 20V S _r T _i O
_{It is a 3-} system varistor, and the surge waveform used is (1.2 ×
50) μsec-5 KV.

For comparison, a ZnO varistor with α = 60 and varistor voltage = 220V was used instead of the above varistor, and the same experiment as above was repeated.

The conditions and results of these experiments are shown in Tables 1 and 2, respectively.

From the results shown in Table 2, it can be seen that the discharge start voltage, the surge response voltage, and the surge residual voltage are all significantly reduced in Example 1 as compared with Comparative Example 1.

Example 2 A gas tube arrester 10 and a varistor 9 which are electrically connected in series by caulking 6 are housed in a cylindrical insulating case 11, as shown in the longitudinal sectional view of FIG. 4, and The same experiment as in Example 1 was performed on the surge absorber having a structure in which the case 11 was filled with the insulating filler 12.

The varistor used was TiO _{2 with} α = 8 and varistor voltage = 50V.
For comparison, a similar experiment was repeated using a ZnO varistor with α = 70 and varistor voltage = 470V instead of the above varistor.

The conditions and results of these experiments are shown in Tables 3 and 4, respectively.

From the results shown in Table 4, it can be seen that the discharge start voltage, the surge response voltage, and the surge residual voltage are all significantly reduced in Example 2 as compared with Comparative Example 2.

[Effects of the Invention] As is clear from the above description, according to the present invention,
Provided is a surge absorbing device which not only prevents a follow-up current but also has a low discharge starting voltage, a surge response voltage, and a residual voltage, and thus a high response speed and an excellent surge absorbing ability.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram showing the device of the present invention, FIG. 2 is a graph for explaining the characteristics of the device of the present invention, and FIGS. 3 and 4 are surge absorption used in the embodiments of the present invention. It is a longitudinal cross-sectional view of an apparatus. In the figure, 2 ... Gap type surge absorber, 3,4,9 ... varistor, 5 ... neon tube, 10 ... gas tube arrester, a,
a ', b, b' ... Voltage-current curve.

Continuation of the front page (72) Nobuya Saruwatari 2270 Yokoze, Yokoze-cho, Chichibu-gun, Saitama Sanryo Mining & Cement Co., Ltd.Ceramics Research Institute (72) Tamiji Ito 2270 Yokose, Yokose-cho, Chichibu-gun, Saitama Sanryo Mining Cement Co., Ltd. Ceramics Research Laboratory (56) Reference JP-A-55-88284 (JP, A) Actual development Shou 62-201490 (JP, U)

Claims (1)

[Claims] 1. A surge absorbing device in which a gap type surge absorbing element and a varistor are electrically connected in series,
The varistor voltage of the varistor is smaller than the line voltage, and the voltage nonlinear coefficient α of the varistor is 1 <α <20.
And the varistor is TiO ₂ system, SrTiO ₃ system,
A surge absorber, which is a varistor selected from SiC-based or SnO ₂ -based.