DE2912415A1 - OVERVOLTAGE PROTECTION CIRCUIT - Google Patents

Description

£ 3 ut

Patent attorney DIPL.-PHYS. DR. W. LANGHOFF re ^ -sanwa .. · B. LA :. ■ ': - β MÜNCHEN 81 - WiSSMANNSTRASSE 14 · TELEPHONE 93 2 7 7 4 TELEGRAM ADDRESS. LANS- "" · ■ "- ..

Munich, March 29, 1979 Our reference: 11 - 18Ii

Patent application
the

Staco Werner Stauber GmbH, Alte Reutstr. 170, 8510 Fuerth

Overvoltage protection circuit

030041/0225

The invention relates to a protection circuit for protection against. electrical devices against overvoltages.

Such protective circuits are already known in which controllable semiconductors are used in their control circuit there are diodes, the arrangement being such that the semiconductor arrangement is above the lock voltage the diode can be controlled into a conducting state. Such a circuit arrangement speaks screaming. but has limited energy absorption. (DE-OS 26 54 419).

It is also a circuit arrangement is known in which a Thyristor or triac in series with at least one diode switches off is, wherein the control voltage for the thyristor or triac is obtained from a circuit branch that is made of Resistors and a zener diode. With such a device it can be achieved that for a short time If overvoltages occur, the device to be protected is not switched off, but continuously supplied is, however, the energy absorption capacity is also in this circuit limited.

Selenium overvoltage limiters, so-called U diodes, are also known for overvoltage limitation. However, these have the disadvantage that there is no sharp limiting effect can be achieved.

Finally, metal oxide varistors are used to limit the voltage, which have a strict limitation application, but can absorb relatively low energy, without being permanently changed or destroyed.

830041/0225

BATH ORIGINAL

The invention is based on the task of creating a protective circuit of the type mentioned at the beginning, which has a high energy absorption capacity and a sharp one -: - ". ·.. Limiting effect.

The solution to this problem is given by a selenium surge suppressor and by a metal oxide varistor connected in parallel to the supply voltage terminals are.

Preferably, the metal oxide varistor is so dimensioned that. ^ its power consumption at the nominal operating voltage is less than 10 times its continuous load capacity.

It is advantageous if a selenium overvoltage limiter is used whose long-term load capacity is at least 50 times the long-term load capacity of the metal oxide varistor.

The selenium overvoltage limiter should be dimensioned in such a way that Z ~. ~ Its power consumption at the nominal operating voltage is a maximum of 3% of its continuous load capacity.

According to a particularly advantageous embodiment, dsr Selenium surge suppressors on the supply voltage side connections and the metal oxide varistor on the device side Connections, and in at least one of the power lines is between the selenium surge suppressor and the metal oxide varistor switched on an inductor.

This is preferably designed as a printed circuit.

According to a development, the metal oxide varistor can be a Capacitor be connected in parallel.

O30Q41 / Q225

BATH ORIGINAL

It is also beneficial to run parallel to the selenium overvoltage limiter to switch a spark gap, which is preferably as an interruption in the conductor track and board eir.r-r: - printed circuit is formed.

The invention is described below with reference to schematic drawings additionally described using an exemplary embodiment.

Fig. 1 is a circuit diagram of a protection circuit;

Figure 2 is a top plan view of a completed protective device.

The protection circuit shown in Fig. 1, the interconnection is intended between the AC network and a consumer, includes supply voltage-side connections 1 and 2 and consumer-side connections 3 and 4. Connections 1 and 4 are directly connected to each other, and an inductance 5 is connected between the terminals 2 and 3. Connections 1 and on the supply voltage side 2 are bridged by a selenium overvoltage limiter 6 and a spark gap 7. The selenium surge suppressor 6 consists of nine non-polarized so-called Ü-diodes, which are connected in series.

The consumer-side connections 3 and 4 are bridged by a metal oxide varistor 8, which may be a Capacitor 9 can be connected in parallel.

Fig. 2 shows a plan view of a practical embodiment of a protective device. This includes a circuit board 10, on which two conductor tracks 11 and are upset. The conductor track 11 has at one end

© 30041/0225 _ßAD original

a bore 13 which corresponds to the connection 2 on the supply voltage side. It runs over a substantial part of the Length of the circuit board 10 straight and then goes into a spiral Area 14 over, which forms an inductance.

The other conductor track 12 has at one end eber.i ^^ Is a bore 15 which corresponds to the supply voltage-side connection "1, and extends straight to the other T '::" of the circuit board and is there with a bore 16 versGl :;. n _r which corresponds to connection 4 on the consumer side.

The inner end of the spiral-shaped region 14 and a point of the conductor track 12 adjacent to this end are provided with small bores 17 and 18, respectively, through which the connecting wires of the metal oxide varistor 8, which are soldered to the conductor tracks in question at these points, can be guided. On the other side of the circuit board 10 there is a conductor track 19, one end of which extends into the region of the bore 17 and the other end of which has a bore 20 which corresponds to the connection 3 on the consumer side.

On the straight areas of the conductor tracks 11 and 12 are the Terminal lugs 21 and 22 of the selenium overvoltage limiter 6 are soldered on. Between the soldering points and the holes 13 and 15, the two conductor tracks 11 and 12 are provided with mutually facing legs 23 and 24, which on a end dumbbell-shaped cutout 25 of the circuit board Ί0 and form a spark gap that is exceeded when a responds to a certain voltage.

The selenium high voltage limiter 6 is shown in Fig. 2 with five in Series of connected U diodes shown. For an operating voltage of 220 volts alternating current are generally

130041/0225

291241b

- ν Λ-

nine non-polarized U diodes required.

The metal oxide varistor 8 is chosen so that it is at eir-.r DC voltage of 430 volts a current of 1 inA through I "" = t. The long-term load capacity of the same is 0.6 watts.

The selenium overvoltage limiter 6 contains U diodes with a plate size of 23 23 mm, which at a voltage of 430 volts pass a current of 600 mA.

When overvoltages occur, the selenium overvoltage limiter is used first active, which seir.er an energy of 100 Ws electrical overvoltage impulses without change Properties and can destroy without damage.

The spark gap 23, 24, 25 responds when the voltage at the connections 13 and 15 exceeds 1000 volts.

When an overvoltage occurs, the voltage will rise on the metal oxide varistor 8 by the inductance 5 in connection with the self-capacitance of the varistor, which in of the order of 1000 pF is limited. This avoids having very steep and high voltage peaks the metal oxide varistor 8 is overloaded. Thus, the majority of the energy of an overvoltage pulse is in the selenium overvoltage limiter 6 destroyed and possibly in the spark gap 7, while the metal oxide varistor in connection with the inductance 5 and possibly with a capacitance 9 connected in parallel with the metal oxide varistor is very sharply limited, so that reliable protection a device connected as a consumer is achieved.

930041/0225

BAD ORIQiNAL

The protective circuit shown combines a high energy absorption capacity with a steep voltage limitation and is relatively robust and easy to manufacture.

The data of the individual parts can of course be adapted to a particular purpose within the scope of the invention will.

030041/0225

bad original

JD.

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Claims (9)

11-1813 claims: 1. Protective circuit for protecting electrical devices α = ·? * .. _.,. Overvoltages, characterized by the parallel connection of a selenium overvoltage limiter ^f < ^: > * and a metal oxide varistor (8) to the power saving lines. 2. Protection circuit according to claim 1, characterized in that g e k e η .- is characterized that the metal oxide varistor (8) is dimensioned so that its power consumption at the nominal operating voltage kl < Long-term resilience. Operating voltage is less than 10 times 3. Protection circuit according to claim 2, characterized in that a selenium overvoltage limiter (6) is used whose long-term load capacity is at least 50 times the long-term load capacity of the metal oxide varistor 08) is. 4. Protection circuit according to claim 3, characterized in that the Sölen overvoltage limiter is dimensioned in such a way that its power consumption at the nominal operating voltage does not exceed 3% of its continuous load capacity amounts to. 5. Protection circuit according to claim 1 to 4, characterized ge indicates that the selenium overvoltage limiter (6) is connected to the supply voltage side connections (1,2) and the metal oxide varistor is connected to the device-side connections (3,4) and that in at least one of these Viscb? .- verbir.der.3en current conductor τ-- r. © 30041/0225 BATH between the selenium overvoltage limiter (6) and derr. Metal oxide varistor (8) a choke is connected. 6. Protection circuit according to claim 5, characterized in that the throttle is designed as a printed Sz ':: -: 1 ~ device (14). 7. Protection circuit according to claim 5 or 6, characterized g ~ indicates that the metal ^oxide: a capacitor (9) is connected in parallel. 8. Protection circuit according to claim 5 to 7, characterized ge
indicates that a spark gap (7) is connected in parallel with the selenium overvoltage limiter (6). 9. Protection circuit according to claim 8, characterized in that the spark gap as an interruption (25) in the conductor track (23,24) and the board
(10) a printed circuit is formed. 930041/0225