CN2151569Y - Safety unit for program-controlled telephone switch board - Google Patents

Abstract

The utility model discloses a safety unit for a program-controlled telephone switch board, comprising two input terminals L1, L2, two output terminals L'1, L'2 and a ground terminal G. The utility model is characterized in that a PTC thermistor is connected in series between the terminal L1 and the terminal L'1, and a PTC thermistor is connected in series between the terminal L2 and the terminal L'2; a zinc-oxide varistor is connected between the terminal L1 and the ground terminal G, and a zinc-oxide varistor is connected between the terminal L2 and the ground terminal G. The safety unit is connected at the interface point of telephone equipment, which can prevent the impact of the excess voltage or the excess current from the external line to avoid the device being damaged. The utility model has the advantages of small size, high reliability, long service life and high sensitivity.

Description

Safety unit for program-controlled telephone switch board

The utility model relates to a kind of SPC telephone exchange protector.

At present, the interface in every repeat circuit of telephone exchange and subscriber line circuit and outside line (comprising open-wire line and cable) generally all is equipped with protector, to prevent causing the damage of switching equipment from the impact of the thunder and lightning of outside line or unexpected overvoltage, overcurrent.

Therefore, protector should have overvoltage protection and two kinds of basic functions of overcurrent protection.As shown in Figure 1, be connected in parallel between outside line side and the earth terminal for overvoltage protecting device (discharge tube F), series connection on the line be over-current protection device (heat coil H).

Traditional overvoltage protecting device is carbon plate lightning arrester, discharge tube lightning arrester, gap lightning arrester etc.Traditional over-current protection device has molten

Pipe, heat coil etc.

The carbon plate lightning arrester is the phone lightning arrester of using the most generally in early days.It is actually a kind of gap lightning arrester, and its discharging gap is to be adjusted by the thickness that is clipped in two blocks of mica sheets between the carbon plate, discharge voltage higher (generally about 350V), and be difficult to consistent.And after each thunderstorm, all carbon plate to be extracted inspection one by one, wipe away the powdered carbon that stays after the discharge clearly, in order to avoid cause electric leakage even short circuit ground down.Maintenance workload is big, fault is many, and volume is big.

The discharge tube lightning arrester is the phone lightning arrester that grows up in the sixties.Than the carbon plate lightning arrester, its discharge voltage lower (about 250V), maintenance workload is less.And because discharge is to carry out under vacuum state, thereby response speed is than carbon plate lightning arrester fast (Millisecond).But volume ratio carbon plate lightning arrester is big, and price is also higher.

Traditional over-current protection device removes substation and the outside line interface is used molten Outside the pipe, switch and outside line interface are used heat coil always.It is with the series connection of the yarn bag resistive conductor coiled coil of wire on the line.When on the circuit during by big electric current because resistance coil heating and with the low temperature glue fusing of its inwall, make its Central Plains by the gluing fuse bullet of living of low temperature to ground plate, at this moment down with circuit.Heat coil after the action has generally just been passed into disuse.Therefore adopt this overcurrent protective device maintenance workload big, volume is big, and expense is also big.

Since SPC telephone exchange was come out, because devices such as a large amount of employing integrated circuits propose more harsh requirement to overvoltage, overcurrent, overtemperature protection, therefore, above-mentioned traditional protector can not adapt to.

The purpose of this utility model is that a kind of SPC telephone exchange protector will be provided, and not only volume is little, highly sensitive for it, and reliable operation, and the life-span is long.

Below in conjunction with drawings and Examples the utility model is specifically described.

Fig. 1 is the circuit diagram of existing a kind of protector.

Fig. 2 is embodiment-circuit diagram.

Fig. 3 is the electric current of zinc oxide varistor--the voltage relationship characteristic curve.

Fig. 4 is the resistance of PTC themistor--the temperature relation characteristic curve.

Fig. 5 is the electric current of PTC--the time relationship characteristic curve.

Fig. 6 is the temperature of PTC--the time relationship characteristic curve.

Fig. 7 is embodiment two circuit diagrams, and Fig. 8 is embodiment two product external views, and Fig. 9 is the upward view of Fig. 8, and Figure 10 is the A-A cutaway view (deleting housing among the figure) of Fig. 8.

With reference to accompanying drawing, embodiment one of the present utility model comprises two input terminal L1, L2, and two outlet terminal L ' 1, L ' 2 and earth terminal G is characterized in that being serially connected with PTC themistor Rt respectively between L1L ' 1 terminals and between L2L ' 2 terminals; Between input terminal L1 and the earth terminal G, being connected to zinc oxide varistor Rv(respectively between L2 and the earth terminal G is ZNR).

Fig. 3 is the electric current of zinc oxide varistor--the voltage relationship characteristic curve.It is big that zinc oxide varistor has a non linear coefficient, (α 〉=40), deboost low (≤250V), characteristics such as discharge capacity big (250A), leakage current little (≤10 μ A), response speed fast (≤50m μ s), voltage temperature coefficient little (≤0.05%/℃), nonpolarity (bi-directional symmetrical), life-span be long.Than carbon plate lightning arrester and discharge tube lightning arrester, advantages such as volume is little, in light weight, safe and reliable, maintenance workload is little are arranged.

Fig. 4, Fig. 5, Fig. 6 are PTC themistor related characteristics curve diagrammatic sketch.The PTC thermistor has positive temperature coefficient big (α 〉=12%/℃), big (Rmax/Rmin 〉=6 * 10 of pressure ratio ³), the low characteristics such as (p25≤73.5 Ω cm) of normal temperature resistance.Be failure to actuate during when it, can move (operate time≤0.2 second during 3A during greater than the operating current some rapidly by operating current; During 2A, operate time≤0.5 second; During 1A, operate time≤1.5 second; 0.5A the time, operate time≤20 second).Thereby melting than tradition usefulness

Pipe and heat coil have remarkable advantages such as response is fast, reliable operation, the life-span is long, volume is little, maintenance workload is little.In sum, this reality is made new embodiment one owing to adopted zinc oxide varistor as overvoltage protector, adopts PTC themistor as overcurrent protector, and therefore, not only reliable operation, life-span are long, and volume is little, and be highly sensitive.

The circuit of embodiment two of the present utility model such as Fig. 7; it comprises two input terminal L1, L2; two outlet terminal L ' 1, L ' 2 and earth terminal G; it is characterized in that being serially connected with PTC themistor respectively between L1L ' 1 terminals and between L2L ' 2 terminals; between input terminal L1 and the earth terminal G, be parallel with zinc oxide varistor and overtemperature protection device T between L2 and the earth terminal G respectively.

Than embodiment one, embodiment two is owing to set up the overtemperature protection device, so fail safe is better.

Fig. 8, Fig. 9 and Figure 10 are embodiment two product configurations schematic diagrames.Among the figure as an input terminal L1(or a L2) lower carriage body 2 on, has a platform 3, be connected with block zinc oxide varistor 4 on the platform and fold in the low-melting-point metal piece 5 of zinc oxide varistor top, the perpendicular expansion link assembly that is equipped with in low-melting-point metal piece top, the expansion link assembly is by bending contact chip 6 down, hang down to being connected to down the montant 7 on the curved contact chip and being placed in the outer stage clip of montant 8 and form, the inner bottom surface of curved contact chip 6 contacts with low-melting-point metal piece 5 down, the spacing of bottom of turning under the curved contact chip and platform equals the thickness of low-melting-point metal piece for a short time down, montant top is placed through on the through hole 9 as the upper supporting plate body 10 of earth terminal G, the lower end of stage clip 8 is pressed on down the upper side of curved contact chip 6, and the upper end overhead is in the downside of upper supporting plate body 10.Input terminal L1(or L2) and outlet terminal L ' 1(or L ' 2) between folder establishing a PTC themistor 11.The bottom side of housing 12 has input terminal L1, L2 spliced eye 13,14, the extension bar 17 of outlet terminal L ' 1, L ' 2 spliced eyes 15,16 and upper supporting plate body stretch out through hole 18.What the upside of housing had a montant 7 stretches out through hole 19.

When this protector is in use overheated, low-melting-point metal piece fusing, stage clip promotes curved contact chip 6 and contact with platform down and makes directly ground down of the dangerous voltage brought in from input wires or electric current.

Whether whether the length of stretching out housing from montant 7 shortens, can differentiate this overtemperature protection device and move.

The utility model is applicable to program-controlled telephone, subsets electron exchanger, accurate electron exchanger and other automatically, common-battery, magneto exchange.This product favorable working performance, cost is not high, and popularizing application prospect is considerable.

Claims (3)

1, a kind of SPC telephone exchange protector, comprise two input terminal L1, L2 two outlet terminal L ' 1, L ' 2 and earth terminal G, it is characterized in that between L1, L ' 1 terminals and L2, L ' 2 terminals between be serially connected with PTC themistor respectively, between input terminal L1 and the earth terminal G, be connected to zinc oxide varistor respectively between L2 and the earth terminal G.

2, a kind of SPC telephone exchange protector; comprise two input terminal L1, L2 two outlet terminal L ' 1, L ' 2 and earth terminal G; it is characterized in that L1, L ' 1; be serially connected with PTC themistor respectively between the terminals and between the L2, L ' 2 terminals; between input terminal L1 and the earth terminal G, be parallel with zinc oxide varistor and overtemperature protection device between L2 and the earth terminal G respectively.

3, SPC telephone exchange protector according to claim 2, it is characterized in that, on the lower carriage body as an input terminal, has a platform, be connected with block zinc oxide varistor on the platform and fold in the low-melting-point metal piece of zinc oxide varistor top, the perpendicular expansion link assembly that is equipped with in low-melting-point metal piece top, the expansion link assembly is by bending contact chip down, hang down to being connected to down the montant on the curved contact chip and being placed in the outer stage clip of montant and form, the inner bottom surface of curved contact chip contacts with the low-melting-point metal piece down, the spacing of bottom of turning under the curved contact chip and platform equals the thickness of low-melting-point metal piece for a short time down, montant top is placed through on the through hole as the upper supporting plate body of earth terminal G, the lower end of stage clip is pressed on down the upper side of curved contact chip, and the upper end overhead is in the downside of upper supporting plate body.

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