WO2015113659A1

WO2015113659A1 - Circuit arrangement for overvoltage protection

Info

Publication number: WO2015113659A1
Application number: PCT/EP2014/072555
Authority: WO
Inventors: Robert Hoffmann
Original assignee: Epcos Ag
Priority date: 2014-01-31
Filing date: 2014-10-21
Publication date: 2015-08-06
Also published as: DE202014100428U1

Abstract

The invention relates to a circuit arrangement for overvoltage protection comprising: a surge arrester (1) having a first electrode (A), the connection thereof being coupled to a first potential node (10), a second electrode (B), the connection thereof being coupled to a second potential node (20) and a central electrode (C); a first voltage-dependent resistance component (2) which is coupled to the connection of the central electrode (C) and to the connection of the first potential node (10); and a second voltage-dependent resistance component (3) which is coupled to the connection of the central electrode (C) and to the connection of the second potential node (20).

Description

description

The invention relates to a circuit arrangement for the overvoltage protection

Overvoltage protection .

Electrical or electronic devices connected to

AC mains are operated, are designed for a given nominal voltage, the mains side

provided. The power distribution and supply of current and voltage to the device takes place in a single-phase connection via a neutral conductor, referred to for short as N or N conductor, and an outer conductor, referred to as L or L conductor or alternatively as a phase. The rated voltage can be for example 230V. For three-phase connections, there are three outer conductors, labeled LI, L2, and L3.

Line voltage fluctuations can cause the electrical or electronic equipment to be exposed to a temporary or permanent overvoltage that exceeds the rated voltage.

Such overvoltages can for example also be done by a wrong connection of the device. This is the case, for example, if the N-conductor has a further phase,

For example, L2 or L3, is reversed.

Another cause of overvoltages can

Be voltage fluctuations in the network. This problem occurs, for example, in countries where the expansion of network infrastructure is not in line with industrial development but also in so-called developing countries with weak network architecture.

Such surges can cause the equipment to be damaged or destroyed. Then it is

required to repair them respectively

out.

It raises the task of electrical equipment through a circuit arrangement before temporary or permanent

Protect overvoltages.

This object is achieved by a circuit arrangement for overvoltage protection with the features of claim 1.

The circuit arrangement comprises a surge arrester having a first electrode whose terminal is coupled to a first potential node, a second electrode whose terminal is coupled to a second potential node, and a center electrode. A first voltage dependent resistance component is connected to the terminal of

Center electrode and the first potential node coupled. A second voltage dependent resistance component is connected to the terminal of the center electrode and the second

Coupled with potential nodes.

The first and second voltage-dependent resistance components are connected in series. Advantageously, the

voltage-dependent resistance components connected to the terminal of the center electrode and the corresponding potential node. This circuit arrangement serves as a protection circuit and limits an overvoltage applied on the input side to protect the circuit arrangement connected downstream

electrical device.

The three-electrode surge arrester is a component for limiting dangerous overvoltages. This may for example be a Gasabieiter. Of the

Überspannungsabieiter has three electrodes, of which the first and second are usually arranged on the front side. The center electrode is interposed therebetween. The terminals of the electrodes allow connection to other circuit elements. In compact designs contacting the electrodes takes place directly on the outer sides, which serve as connections in this case. The terminals can also be led away from the electrodes, for example as

Wires, be designed.

If the voltage between two of the electrodes rises above a response voltage, also called ignition voltage, then the

Overvoltage degraded by the ignition of a gas discharge.

This comes at mains voltages of one hundred volts and more

Short circuit same. Usually, the short circuit between the first and the second electrode, which are arranged at the outer ends of the surge arrester. But it can also be a short circuit between one of these

Electrodes and the center electrode done.

The voltage-dependent resistance components have a non-linear characteristic. Their resistance depends on the applied voltage and increases with increasing

Tension off. The voltage dependent resistance component may be a single device or a group of Comprise components. The voltage-dependent

Resistor component may include, for example, a varistor. The term "coupled" means that elements coupled together can be electrically connected to each other directly or via other elements, in the former case, the elements are connected via traces or conductor patterns that conduct, but not influence, current and voltage between the elements In the other case, one or more components are connected between the coupled elements, while the term "connected" means that the components connected to each other directly, without

Interconnecting further elements are connected to each other electrically conductive. Connecting two elements via another element means that the latter is connected between the former. This circuit arrangement can be connected upstream of an electrical device in that the first potential node corresponds to the L conductor, for example, and the second one

Potential node corresponds to the N conductor. Is one between the first and second potential node

Rated voltage at which the device can or should be operated on, the circuit arrangement acts, except for small possible leakage currents, as an insulator between the L and N conductors. Serving as a protective circuit circuit arrangement with their combination of various overvoltage and

Overcurrent protection components limit an adjacent Overvoltage to a fixed value. There is also protection against interference pulses.

For glitches, which are also called surge voltages, fast

Overvoltages or the English term "surges" are the voltage-dependent ones

Resistor components due to their faster

Response time active and limit the voltage. Even at low overvoltage the Überspannungsabieiter ignites yet and the voltage-dependent resistance components are active, so that a current flows to the voltage limiting via the series connection of first and second voltage-dependent resistance component. For a limited time

Over-voltage ignites the distance between the two

Electrodes, which limits the voltage. If the overvoltage decreases again, the surge absorber returns to its insulating state. These

Overvoltages usually go with one

Amplitude increase associated with the AC voltage.

The surge arrester has a first response voltage for a discharge between the first and the second electrode, which is accompanied by a current flow, a second response voltage for a discharge between the first electrode and the center electrode, which with a

Current flow is associated, and a third operating voltage for a discharge between the center electrode and the second electrode, which is accompanied by a current flow. The first response voltage is greater, usually much greater, than the second response voltage. The first response voltage is greater, usually much larger, than the third

Response voltage. The second and the third response voltage are the same or almost the same. Response voltages and the discharging process are also referred to as "ignition voltage" or "ignition". When the second or third response voltage, but not the first response voltage, is exceeded, discharge may occur over the distance between the first electrode and the center electrode or over the distance between the second electrode and the center electrode. In these cases, the current flow for voltage dissipation via the ignited route and the varistor, which is connected in parallel to the other route.

The first voltage-dependent resistance component has a first threshold voltage, and the second voltage-dependent

Resistor component has a second threshold voltage. The sum of the first and second threshold voltage is less than the first threshold voltage, so that at low

Overvoltages the derivation of the overvoltage by a current flow over the voltage-dependent

Resistance components takes place.

In one embodiment, the first potential node is coupled to a third potential node and the second

Potential node is with a fourth potential node

coupled. Between the third and fourth potential node is externally a voltage with a predetermined

Nominal voltage value can be applied, which is used to supply the

Circuit arrangement downstream device is used. This predetermined nominal voltage value allows the operation of the

connected devices in normal operation and can

for example, be 230 volts. The first response voltage and the sum of the first and the second threshold voltage are greater than the first

Nominal voltage value, so that the voltage limitation does not already occur during normal operation.

In one embodiment, the connection of the first electrode to the first potential node is coupled via an impedance. Alternatively or additionally, the connection of the second electrode to the second potential node is coupled via an impedance. The impedances may each comprise one or more components. A supply voltage for a device nachschaltbares the circuit arrangement can be provided between the first and second potential node. In one embodiment, the connection of the first electrode to the first potential node is coupled via an impedance. Alternatively or additionally, the connection of the second electrode to the second potential node is coupled via an impedance. The impedances may each comprise one or more components. In this embodiment, the

Supply voltage for one of the circuit arrangement

Downstream device instead of the first on a fifth

Potential node and / or provided instead of the second at a sixth potential node. The fifth potential node is between the first impedance and the terminal of the first electrode, and the sixth potential node is between the first impedance and the terminal of the second electrode. In other words, the supply voltage tap occurs between the potential at either the first or fifth

Potential node and the potential at either the second or sixth potential node. The impedances allow a better decoupling of the

Surge arrester in case of surge voltage. The

Impedances may be inductive or capacitive in nature or may include inductive components to decouple the surge absorber at high frequency surge voltages.

As a result, the surge arrester does not fire at surge voltages, but the voltage spikes are dissipated across the voltage dependent resistive components. In one embodiment, the surge arrester has an overcurrent protection device that is designed to short-circuit between the first and second and

advantageously trigger the third electrode. The short circuit will be triggered by one after ignition

To prevent overloading of the surge arrester. The short-circuit mechanism of the overcurrent protection device becomes longer-lasting or indefinitely

Overvoltages, such as a wrong connection, triggered. In such a case, only the replacement of the circuit arrangement, but not of the entire electrical device is required.

Such an overcurrent protection device can one

Have shorting bar, by a fusible

Element is deflected such that it is not electrically connected to both the first and the second electrode, or, in other words, from the first

Electrode and / or the second electrode is isolated. However, the connection with only one of the electrodes is possible. After melting the fusible element is the

Shorting bar electrically conductively connected to both the first and the second electrode. Since melting of the fusible element usually takes a longer time Overload requires, the short-circuit mechanism triggers for prolonged overvoltages. After triggering the short-circuit mechanism, the current over the

Shorting bar derived. As a result, the voltage between the first and the second electrode collapses.

In one embodiment, a first overcurrent protection element with the first potential node and the third

Potential node or a second overcurrent protection element to be connected to the second potential node and a fourth potential node. The overcurrent protection elements interrupt the flow of current after triggering the short-circuit mechanism. The overcurrent protection element serves as a rather sluggish

Overcurrent protection and can, for example, a

Have fuse. These upstream

Overcurrent fuses prevent damage from long-lasting surges.

To protect a circuit arrangement described above, it is provided that a supply voltage is applied to the third and fourth potential node, wherein at

Exceeding a response voltage of

Surge arrester a current flow to

Overvoltage dissipation over the first electrode and second electrode extends.

The surge arrester is short-circuited after the current flow for overvoltage dissipation over the first

Inserted electrode and second electrode. Then the current flow is interrupted by triggering a fuse.

Advantageous embodiments of the surge arrester are the subject of dependent claims. The arrangements described above are explained in more detail below with reference to exemplary embodiments. The drawings are not to scale. FIG. 1 shows a circuit diagram of an embodiment of the invention

Circuitry, a circuit diagram of another embodiment of the circuit arrangement, a circuit diagram of a further embodiment of the circuit arrangement, the timing of current and voltage at Überspannungsabieiter when occurring

Overvoltage, the temporal representation of current and voltage at the surge arrester with decreasing overvoltage and

Figure 6 shows the timing of current and voltage on

Overvoltage arrester when tripping the

Short circuit mechanism in case of longer

continuous overvoltage.

Figure 1 shows the circuit diagram of a circuit arrangement for overvoltage protection, which is connected between the phase and neutral L and Ν ^{λ of} an electrical device (not shown) and phase and neutral conductors L and N of a supply network (not shown). Phase and neutral LL and NN of the electrical device and the network are each via an overcurrent protection element 5, 6, ie a

Fuse, connected to each other so that on the line side in both the phase and in the neutral conductor one each

Overcurrent protection is used.

Between the L ^x conductor, which corresponds to a first potential node 10, and the N ^x conductor, the second

Potential node 20 corresponds, a surge arrester 1 and two voltage-dependent resistance components, which are designed as varistors 2, 3, are connected.

The circuit arrangement comprises a surge arrester 1 having a first electrode, denoted by A in the schematic representation of the surge arrester 1, a second electrode, denoted by B in the schematic illustration, and a center electrode, denoted by C in the schematic illustration. The terminal of the first electrode A is connected to the first potential node 10. The terminal of the second electrode B is connected to the second potential node 20. In other words, phase L ^x and neutral conductor Ν ^λ are connected to the first and second electrodes A, B, respectively. A current flow can over the distance AC, from the first

Electrode A to the center electrode C, take place. A current flow can take place over the distance C-B, from center electrode C to the second electrode B. A current flow can take place over the distance A-B, from the first electrode A to the second electrode B.

The tap between the series-connected first and second varistors 2, 3 is connected to the terminal of Center electrode C connected. In other words: the

Connection of the center electrode is connected to the star point of two varistors 2, 3. Between the first potential node 10 and the L-conductor of the network, which corresponds to a third potential node 30, a first overcurrent protection element 5 is connected. Between the second potential node 20 and the N-conductor of the network, which corresponds to a fourth potential node 40, a second overcurrent protection element 6 is connected. The

Overcurrent protection elements 5, 6 may include fuses, also referred to as "fuses".

Between the third and fourth potential nodes 30, 40, a mains voltage for supplying the electrical device (not shown) can be applied.

The surge arrester 1 has three possible current paths, A-C, C-B and A-B, over which overvoltages can flow. When a first response voltage between the terminals of the first electrode A and the second electrode B is exceeded, a current flows on the route A-B. When a second response voltage between the terminals of the first electrode A and the center electrode C is exceeded, a current flows on the route A-C. If a third is exceeded

Response voltage between the terminals of the center electrode and the second electrode B, a current flows on the route C-B. The first response voltage is greater than the second response voltage as well as the third

Response voltage. The latter two are

usually the same. It turns out for the first

Response voltage UAB, the second response voltage UAC and the third response voltage UBC following formula relationships: UAB »UAC, UAB» UBC, UAC ~ UCB.

The surge arrester 1 has a

Overcurrent protection device 7, which is designed to trigger a short circuit between the first and the second electrode A, B. The short circuit is triggered by overvoltages lasting for a longer period of time or unlimited, in order to prevent an overload due to the associated current flow. The overcurrent protection device 7 can

For example, a shorting bar, as indicated in Figure 1, include.

The shorting bar 7 is deflected by a fusible element, such as plastic or solder, such that it is not electrically connected to both the first and the second electrode. After this

Melting of the fusible element causes a

Restoring force, for example, the spring force of

deflected shorting bar, that the first and the second electrode A, B are connected by shorting bar 7 electrically conductive.

The first and second varistors 2, 3 have a first one

or a second threshold voltage, in which the

Current through varistors 2, 3 noticeably larger than the reverse current is, so that an overvoltage on the first and second varistor 2, 3 can flow. The first and the second

Varistor 2, 3 may be the same type with the same current-voltage characteristic, so that the first and the second

Threshold voltage are the same. Alternatively, the first and the second varistor 2, 3 may have different current-voltage characteristics, so that the first and the second Threshold voltage are different. The first

Response voltage is greater than the sum of the first and the second threshold voltage. When the rated voltage is applied, a current flow between the first and second potential nodes 10, 20 through the

Circuitry locked. Overload may cause a current flow between L ^x and N ^x conductors across the various branches of the circuitry. A first branch 51 is between the first first potential node 10 and the terminal of the first electrode A; a second branch 52 is between the terminal of the second electrode B and the second potential node B; in the third branch 53, the first varistor is voltage-dependent

Resistance component 2; a fourth branch 54 is the voltage-dependent second varistor

Resistance component 3.

The above-described circuit arrangement in FIG. 1 responds to various interference situations as follows:

In the case of overvoltages which are above the nominal voltage and the sum of the threshold voltages, but below the first response voltage of the surge arrester 1, the surge arrester 1 does not fire, but blocks the first and the second branch 51, 52. The overvoltages are produced by the first and second varistor 2, 3, so that a current flows through the third and fourth branches 53, 54. Overvoltages caused by interference pulses are at low

Overvoltages below the first operating voltage for the time being, the varistors active. For overvoltages above the rated voltage but below the first operating voltage of the Surge arrester 1 lie, ignites the

Surge arrester 1 does not, but blocks the first and second branches 51, 52. The low overvoltages are dissipated by the first and second varistors 2, 3, so that a current flows through the third and fourth branches 53, 54.

Although these glitches may have a greater value than the first operating voltage of the surge arrester, this does not ignite because of the inertia of the surge arrester 1.

However, it may happen, in particular in the case of larger interference pulses, that one of the two distances A-C or C-B of the

Surge arrester 1 ignites. In the former case, the current flow takes place via the first branch 51, the route A-C and the second varistor 3 in the fourth branch 54. In the other case, the current flows via the first varistor 2 in the third branch 53, the route C-B and the second branch 52.

For temporary overvoltages, especially in the

Frequency range of AC mains voltage, with a

Amplitude increase accompanied ignites the

Surge arrester 1 the route A-B. In this case, a current flows through the first and second branches 51, 52. The voltage is limited.

Figure 4 shows the temporal behavior of current I and

Voltage U between the first and second electrodes A, B when an overvoltage occurs. It should be noted that the current and voltage curves are schematic without

Consideration of transients are shown. Example values can be a mains voltage with a Rated voltage of 230V as well as an increase to about 440V. The first operating voltage UAB is greater than 230V: UAB »230V. At Überspannungsabieiter 1 is initially a sinusoidal voltage U, whose amplitude is less than the first operating voltage UAB. The surge arrester 1 is in an insulating state and blocks; no current flows over the distance AB.

At time Tl, the amplitude voltage increases such that it lies above the first response voltage UAB. When the first response voltage UAB is exceeded, the surge arrester ignites; As a result, a current flows over the distance A-B and the voltage U breaks down. With the next applied half-wave, the current flow is extinguished and the effect described above occurs again.

The resulting voltage and current waveform has vertically truncated sine half-waves.

FIG. 5 schematically shows the temporal behavior of current I and voltage U between the first and second electrodes A, B when the excessive voltage U drops below the first response voltage UAB.

First of all, the sinusoidal voltage U is present whose amplitude is greater than the first response voltage UAB. The effects occurring here are already for FIG. 4

been described.

At time T2, the amplitude voltage of the

sinusoidal signal again below the first operating voltage UAB. As the overvoltage subsides, the surge absorber 1 returns to its insulating state. In this case, a sinusoidal voltage is again applied across the surge arrester 1, and no current flows.

FIG. 6 shows the temporal behavior of current I and

Voltage U between the first and the second electrode A, B, in antiphase, at longer lasting

Exceeding the response voltage UAB.

Initially, the voltage and current course are vertical

cut half sine waves, as for Figure 4

described.

At time T3, the short-circuit mechanism 7 of the surge arrester 1 ignites. As a result, the current between the first and second electrodes A, B flows off via the short-circuit bar and irreversibly collapses the voltage, so that the current I becomes sinusoidal

Course has.

If the shorting mechanism is the L ^x and N ^x conductors

Short-circuited, shortly after release the fuses 5, 6, resulting in a separation of the device from the network. The current flow is interrupted when one of the fuses 5, 6 triggers (not shown in Figure 6).

Figure 2 shows another embodiment of the

Circuitry. In the following, only the

Differences to the embodiment described in Figure 1. This circuit arrangement differs from that shown in FIG. 1 in that an impedance 8 is coupled between the connection of the first electrode A and the first potential node 10. Between the connection of the second electrode B and the second potential node 20, a second impedance 9 is coupled. The impedances 8, 9 can be inductive or

have capacitive character. They cause that at

Pulse-shaped surge voltages the pulses from

Überspannungsabieiter 1 are decoupled, so that ignition is avoided. With time-limited overvoltages in a lower frequency range occur in this

Embodiment that in the figures 4 to 6

illustrated effects on. FIG. 3 shows a further exemplary embodiment of the invention

Circuitry. In the following, only the

Differences from the exemplary embodiment in FIGS. 1 and 2

described. Also in this circuit is between the

Connection of the first electrode A and the first

Potentialkoten 10 coupled an impedance 8. Between the connection of the second electrode B and the second

Potential node 20 is coupled to a second impedance 9. The impedances 8, 9 can have inductive or capacitive character. They have the effect that the pulses are decoupled from the surge arrester 1 in the case of pulsed impulse voltages, so that ignition is avoided. For a limited time

Overvoltages in a lower frequency range also occur in this embodiment, the illustrated in Figures 4 to 6 effects. However, the embodiment in FIG. 3 differs from that in FIG. 2 in that a supply voltage for a device which can be connected to the circuit arrangement (not shown) is provided between a fifth potential node 50 and a sixth potential node 60.

The fifth potential node 50 corresponding to the L ^{x line} is between the first impedance 8 and the terminal of the first electrode A, and the sixth potential node 60 corresponding to the N ^{x line} is between the second impedance 9 and the terminal the second electrode B.

In this circuit arrangement, not only the fuse 5 but also the first impedance 8 is connected in series between the L and L ^x conductors. In this circuit arrangement, not only the fuse 6 but also the second impedance 9 is connected in series between N and N ^x conductors. It should be understood that the features of the embodiments may be combined.

Reference sign

1 surge arrester

2, 3 voltage-dependent resistance component,

varistor

5, 6 fuse

7 short circuit mechanism

8, 9 impedance

A, B, C electrodes

10, 20, 30, 40, 50, 60 potential nodes

51, 52, 53, 54 branch

Claims

Claims:

1. Circuit arrangement for overvoltage protection with

a surge arrester (1) having a first electrode (A) whose terminal is coupled to a first potential node (10), a second electrode (B) whose terminal is coupled to a second potential node (20), and a center electrode (C )

- A first voltage-dependent resistance component (2) connected to the connection of the center electrode (C) and the first

Potential node (10) is coupled, and

- A second voltage-dependent resistance component (3), which is coupled to that with the connection of the center electrode (C) and the second potential node (20).

2. Circuit arrangement according to claim 1,

wherein the surge arrester (1) is a first

Response voltage (UAB) for a current flow between the first and the second electrode (A, B) has,

has a second response voltage for a current flow between the first electrode (A) and the center electrode (C), has a third response voltage for a current flow between the center electrode (C) and the second electrode (B), and wherein the first response voltage (UAB) is greater than the second operating voltage and the first operating voltage (UAB) is greater than the third operating voltage.

3. Circuit arrangement according to claim 1 or 2, wherein

the first voltage-dependent resistance component (2) has a first threshold voltage,

the second voltage-dependent resistance component (3) has a second threshold voltage, and wherein the sum of the first and the second threshold voltage is less than the first response voltage (UAB).

4. Circuit arrangement according to one of the preceding

Claims,

wherein the first potential node (10) with a third

Potential node (30) is coupled and the second

Potential node (20) is coupled to a fourth potential node (40), and wherein between the third and fourth potential node, a voltage with a predetermined

Rated voltage value can be applied.

5. Circuit arrangement according to claim 4,

wherein the first response voltage (UAB) is greater than the nominal voltage value.

6. Circuit arrangement according to one of claims 4 or 5, wherein the sum of the first and the second threshold voltage is greater than the nominal voltage value.

7. Circuit arrangement according to one of the preceding

Claims,

wherein the terminal of the first electrode (A) is coupled to the first potential node (10) via an impedance (8) and / or the terminal of the second electrode (B) is coupled to the second potential node (20) via an impedance (9) ,

8. Circuit arrangement according to one of the preceding

Claims,

wherein the surge arrester (1) has a

Overcurrent protection device (7), which is formed a short circuit between the first and the second

Trigger electrode (A, B).

9. Circuit arrangement according to claim 8,

wherein the overcurrent protection device (7) has a

Shorting bar, which is deflected by a fusible element such that it is isolated from the first

Electrode (A) and / or the second electrode (B), and is electrically connected after melting of the fusible element with both the first and the second electrode (A, B).

10. Circuit arrangement according to one of the preceding

Claims,

wherein the first voltage-dependent resistance component (1) has a varistor and / or the second

voltage-dependent resistance component (2) has a varistor.

11. Circuit arrangement according to one of claims 4 to 10, wherein a first overcurrent protection element (5) between the first potential node (10) is connected to the third potential node (30) and / or a second overcurrent protection element (6) between the second potential node (20) and the fourth potential node (40) is connected.

12. Circuit arrangement according to one of the preceding

Claims,

wherein a supply voltage for one of

Circuit arrangement nachschaltbares device between the first and the second potential node (10, 20) is provided.

13. Circuit arrangement according to one of claims 7 to 12 with a fifth potential node (50) and a sixth potential node (60) to which a supply voltage for a device nachschaltbares the circuit arrangement wherein the fifth potential node (50) is between the first impedance (8) and the terminal of the first electrode (A) and the sixth potential node (60) between the second impedance (9) and the terminal of the second electrode (B) is.