WO2002033716A1

WO2002033716A1 - Method and device for reducing the contact erosion of a switchgear

Info

Publication number: WO2002033716A1
Application number: PCT/DE2001/003814
Authority: WO
Inventors: Norbert Elsner; Gerd Griepentrog; Reinhard Maier; Diethard Runggaldier; Bernhard Streich
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-10-16
Filing date: 2001-10-04
Publication date: 2002-04-25
Also published as: CN1214421C; EP1327254A1; CN1446367A; JP2004512637A; DE10051161C1; EP1327254B1; DE50112489D1; JP3828866B2

Abstract

In order to reduce the contact erosion of a switchgear (1), in particular a breaker, a switching command (ES) is delayed until the command angle (ΓKξ), related to the phase angle (Γ) of the control voltage (US) of a magnetic system (4) coupled to the main contacts (K1, K2, K3) of the switchgear, is reached, which is associated with the main contact (K1, K2, K3) that currently has the greatest erosion. A number of evaluation units (ALn) for determining the contact erosion (Δmn), a memory unit (10) for determined command angle (ΓKξ) and a phase comparator are provided, which, by means of a comparison of the preferred command angle (ΓKξ) with the phase angle (Γ) of the determined control voltage (US), generates an impulse (S) for starting the switch process.

Description

description

Method and device for reducing the contact erosion of a switching device

The invention relates to a method for reducing the contact wear of a switching device, in particular a contactor. It further relates to an apparatus for performing the method.

In the case of a switching device controlled by alternating current and electromagnetically actuated, the main contact arrangements of which are referred to as main contacts switch a three-phase system, the aim is to reduce the contact erosion by suitable operation and thus to increase the operating time of the switching device. Thus, by avoiding the so-called switching synchronization effect, a uniform erosion can be achieved in the usually three main contacts, which increases the operating time. This is already the wiring of the switchgear or

Contactor coil with a capacitance has been proposed. In addition, a desired equalization of the contact erosion can be increased by avoiding the so-called auto-synchronization of the switching device. For this purpose, for example, switching commands can be delayed according to certain methods in such a way that the switching angles are evenly distributed.

In order to compensate for both the auto-synchronization effect and the mechanical synchronization effect caused, for example, by manufacturing tolerances, the main contact arrangement most severely affected by the current erosion could be relieved by suitable selection of the switching time. This would place a greater load on the other two main contact arrangements, which would also bring about leveling. The invention is based on the object of specifying a method for reducing the contact erosion of a switching device, in particular a contactor, with which on the one hand a diverging erosion of the main contacts, in particular caused by the switching synchronism, and on the other hand the total erosion of all three main contact arrangements of the switching device is reduced. Furthermore, a device that is particularly suitable for carrying out the method is to be specified.

With regard to the method, this object is achieved according to the invention by the features of claim 1. For this purpose, in the case of a switching device, after receiving a switch-on command, it is delayed until a preferred phase or command angle is reached, which is assigned to the main contact with the currently most severe erosion. The command or switching command angle1 is a specific point in time related to the phase position of the control or coil voltage for the electromagnetic actuation of the main contacts. The switch-on command angle takes into account the contact closing time that is dependent on this between the application of the coil or control voltage of the magnet system of the switching device coupled to the main contacts and the contact of the contact elements of the respective main contacts.

The invention is based on the consideration that in every half of the network period there are three preferred times or command angles at which a switching operation causes a statistically lower total burnup of all three main contacts than any other

Time or any other equally distributed command angle. Exactly one main contact can be assigned to each of the preferred points in time or command angle, which, on a statistical average, has a lower burnup compared to the other two main contacts when a switching operation initiated at this time or at this command angle. This assignment between the preferred times ten or command angles and the main contacts is unambiguous, so that each main contact or each main contact arrangement is also assigned exactly one preferred command angle. Each preferred command angle has two essential properties, namely, on the one hand, minimal burn-up for a specific main contact. On the other hand, if this preferred command angle, which is assigned to only one of the main contacts, is selected, the burn-up is statistically smaller for all main contacts than for any other command angle.

The delay can be brought about, for example, by a discretely implemented delay element or by a microcontroller. Since there are a total of three preferred command angles or times for every half network period, the delay is at most 180 °, which corresponds to a delay time of 10 ms at a network frequency of 50 Hz. In this way, the avoidance of any switching synchronization is ensured on the one hand. On the other hand, a reduction in the cumulative contact erosion is achieved in all three main contacts or main contact arrangements.

The current erosion of the three main contacts is preferably determined by measuring the time interval during the switch-off process. The time span between a separation of the magnetic system provided for the electromagnetic actuation of the main contacts and the separation of the main contacts is recorded. The magnet system can be separated by a characteristic voltage pulse on the associated one

Magnetic coil can be detected. The separation of the main contacts also results in a voltage pulse, the level of which corresponds at least to the anode-cathode voltage of an arc that arises. Such a time interval measurement is described for example in DE 196 03 310 AI and DE 196 03 319 AI. The time interval measurement uses the knowledge that the burn-off of the main contacts is primarily in a reduction in the thickness of the contact pad and thus expressed in a shortened way.

With regard to the device, the stated object is achieved according to the invention by the features of claim 5. Advantageous refinements are the subject of the subclaims which refer back to the device.

The device thus comprises a number of evaluation elements for determining the erosion of each main contact of the switching device. For this purpose, each evaluation element carries out a time interval measurement based on the voltage across the respective main contact and the voltage of the magnet coil of the magnet system. The three preferred command angles, which are phase angles of the coil or control voltage for the magnet system of the switching device assigned to the three phases of the three-phase network, are expediently stored as a table in a memory module.

A phase comparator generates a comparison of the

Main contact with the command or phase angle currently assigned to the strongest erosion with the phase angle of the currently detected control voltage of the magnet system provides a pulse to initiate the switching process. The pulse sequence of the generated pulse expediently corresponds to half a network period. A flip-flop connected downstream of the phase comparator, preferably a flip-flop, transmits the switch-on command to a switch for applying the control or coil voltage to the magnet system with the pulse generated by the phase comparator. To determine the phase angle of the control voltage, which is preferably recorded continuously, the phase comparator is connected to a phase output of the switching device, to which one of the phases of the three-phase network is connected.

The advantages achieved with the invention consist in particular in that by delay and thus by targeted Influencing the switching-on process of an electromagnetically actuated switching device, in particular a contactor, which is controlled by alternating current, on the one hand avoids the synchronization effect by using its specific properties and on the other hand reduces the total erosion of the main contacts. A change in both the main circuit to be switched by the main contacts and the switching device itself is avoided.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. In it show:

1 shows a basic circuit diagram of a switching device with an arrangement for reducing the contact erosion, FIG. 2 shows the closing time dependent on the switch-on command angle in an angle / time diagram,

3 shows in an angle / speed diagram the closing speed dependent on the switch-on command angle, FIG. 4 shows in an angle / time diagram the lift-off time dependent on the switch-on command angle of main contacts of the switching device,

5 shows in an angle / angle diagram the closing angle of the main contacts which is dependent on the switch-on command angle, and

6 shows in a further diagram the relative bounce charge dependent on the switch-on command angle.

Corresponding parts are provided with the same reference symbols in all figures.

1 shows a contactor as a switching device 1 with three main contact arrangements, hereinafter referred to as main contacts K1 to K3, whose immovable contact elements Kla, K2a and K3a, on the one hand, have phase connections 2 of a three-phase network

L1, L2, 3, N and on the other hand connected to a load 3. The movable contact elements Klb, K2b and K3b of the main contact clocks K1 to K3 are actuated by a common magnet system with a magnet coil 4. The magnetic coil 4, with which the main contacts K1 to K3 are mechanically coupled, is connected via a control line 5 on the one hand to the phase connection 2 of the phase conductor L3 and on the other hand to the connection 2 of the neutral conductor N. In the control line 5 there is a switch 6 for actuating the magnet coil 4 and thus for actuating, ie for switching the magnet system of the switching device 1 on and off.

An evaluation element A _L3 , A _h2 , A _{LI is assigned} to each main contact K1 to K3 to determine the contact wear of the respective main contact K1 to K3. Each of these Auswerteglieder Ar _.3, A _L2, A _L1 is the one hand, via a measuring line 7, the voltage Uι, U _2, U ₃ U about the respective main contact Kl to K3 and via measurement lines 8, the control or coil voltage _S at the Solenoid 4 supplied. Using these voltages U _1; U ₂ , U ₃ and U _s , the evaluation _elements A _rj3 , A _L2 , A _h χ carry out a time interval measurement and thus determine the current erosion values Δm ₁ , Δm ₂ , Δm _{3 of} the main contacts Kl to K3, ie the respective thickness of the remaining contact pads the main contacts Kl to K3.

From the current burn-up values Δmι, Δm ₂ , Δrr- ₃ determined in this way, a function block 9 is used in a function block 9 to determine a B. according to a so-called max-index function, the main contact Kl, K2 or K3 with the greatest erosion is determined. By means of a memory module 10 in which three preferred switch-on command angles Ψκι in a table. Ψκ ₂ .Ψκ _{3 are} stored, the relevant command _angle Ψ _κv for the following switching process is taken and forwarded to a phase _comparator 11.

The phase comparator 11 continuously compares the phase angle Ψ of the coil or control voltage U _s with the preferred command angle Ψ _K v and, if they match, outputs a short pulse S which is, for example, approximately 100 μs long. For this purpose, the phase comparator 11 is connected via a control line 12 to the connection 2 of the neutral conductor N and to one of the phase connections 2, in the exemplary embodiment phase L3, of the three-phase network. In the phase comparator 11, the polarity of the coil voltage U _{Ξ is} not taken into account, so that the pulses S are output at intervals of half a network period T / 2. The pulse S is fed to an input Ei of a flip-flop 13, at whose further input E an external switching command, ie the external switch-on command ES, is pending. The output side connected to the switch 6

With the pulse S present at the input Ei, the flip-flop 13 takes over the switching command ES present at the input E ₂ and thus initiates the switch-on process via the delay-free switch 6.

The derivation of the preferred command angle Ψ _v from the switching behavior of the electromagnetically actuated switching device or contactor 1 is described in more detail below with reference to FIGS. 2 to 6. The switch-on process of a 37kW contactor verified by measurements is used as an example.

2 shows the closing time t _{s which is} dependent on the switch-on command angle Ψ _κ . This gives the time from the application of the control or coil voltage U _s to the contact of the contact elements

Kla to K3b of the main contacts Kl to K3. The switch-on command angle Ψ _κ is the phase angle related to the phase position of the sinusoidal control or protective coil voltage U _s . It can be seen from the curve that the closing time t _s, which is dependent on the switch-on command angle Ψ _{κ, is} not constant, but is subject to a fluctuation of more than 10 ms. At a network frequency of 50 Hz, this corresponds to an angle ψ _κ of more than 180 °.

For Ψ _κ = n ^■ 180 °, with ne N, the switching time t _{s is} minimal. The reason for this is that when the almost exclusively inductive contactor or solenoid 4 is switched on, there is a maximum males transient DC element is caused, which results in a higher attraction force. With a constant switch-on command angle Ψ _κ , the closing time t _{s is subject to} almost no statistical fluctuations. Knowing the command angle Ψ _κ, the closing time t _s and thus the closing time of the main contacts K1, K2, K3 can thus be determined very precisely. It is essential that the closing time t _{s of} all three main contacts K1, K2, K3 is constant, but the closing angle related to the respective mains voltage in the three main contacts K1, K2, K3 at one

Switching process is offset by 120 ° due to the phase shift in the three-phase system.

3 shows the closing speed v _s dependent on the switch-on command angle inkel, ie the speed at which the main contacts K1, K2, K3 meet. Just like the closing time t _s , the closing speed v _{s is} dependent on the switch-on command angle Ψ _κ . In contrast to the closing time t _s , however, the course of the closing speed v _{s is} significantly dependent on the structural conditions of the respective contactor or switching device 1, so that generally valid statements cannot be made in practice. In addition, the closing speed v _{s is} subjected to statistical scatter at a constant switch-on command angle Ψ _κ , which is evident from the error band determined in accordance with the measured standard deviation. Nevertheless, the closing speed v _{s of} all three main contacts K1, K2, K3 is approximately the same, which is reflected in the single graph.

4 shows the lift-off time t dependent on the switch-on command angle Ψ _κ _from all three main contacts K1, K2, K3 during the so-called switch-on bounce. The withdrawal_2 duration t _ab is the accumulated time during which the main contacts K1, K2, K3 are again separated from one another after the first contact. Here, a light arc relevant for the burnup is gene between the contact elements la to 3b of the main contacts Kl to K3.

A comparison of the graphs according to FIGS. 3 and 4 shows a clear relationship between the closing time t _s and the lifting time t _ab . Therefore causes a high closing speed v _s also a comparatively long Abhebedauer _from out. Therefore, as well as from simple considerations of elastic collision and to the spring-mass systems can in averaging over many circuits with the same closing speed v _s for all three main contacts Kl to K3 are also approximately the same Abhebedauer t be assumed _from. This can be done through the relationship

express, where C is a switching device-specific constant.

In addition to the closing speed v _s and thus the lifting time t _ab , the amount of the flowing current i during the bounce lifting of the main contacts K1 to K3 is also important for the burnup. It can be assumed that the erosion is proportional to the integral of the arc current i over time. In addition, the arc current i is usually potentiated with a contact-specific constant k according to the relationship:

Δm are the contact erosion and C ^v and k in particular of the properties of the main contact Kl to K3, z. B. its geometry and material, dependent constants.

Although the first contact of the contact elements la to 3b of the main contacts K1 to K3 takes place almost simultaneously in the absolute, temporal scale, it is the particular one Mains voltage-related electrical closing angles of the main contacts K1, K2, K3 are not the same, but are also offset by 120 ° due to the voltages offset by 120 ° in the three-phase system. This relationship is illustrated in FIG. 5, in which the closing angles standardized to 360 ° in the three main contact arrangements K1, K2, K3 are shown as a function of the switch-on command angle Ψ _κ . The course shown in FIG. 5 can be formulated using the closing time t _s with the aid of the following equations, the activation of the contactor or magnetic coil 4 being coherent with the outer or phase conductor L3 and a clockwise three-wire system on the main contacts K1, K2, K3 is switched:

ΨSLI = (ΨK + ^f ' ^{(Ψ /} ° • 360 ° + 240 °) mod 360 ° T ΨS 2 = (ΨK + - ^^ - 360 ° + 120 °) mod 360 °

T

ΨsL3 = (Ψκ - ^^ - 360 ° mod 360 ° T

T is the network period with a period of 20 ms as a rule. Ψ _s is the closing angle related to the respective phase or phase line Ll, L2, L3. Mod 360 ° denotes the modulus operator, the application of which gives the remainder of the division when divided by 360 °. For example, an angle of 540 ° = 1.5 • 360 ° and a division by 360 ° would result in a factor of 1.5. The numerical remainder of 0.5 would result in a division remainder of 180 °.

It follows from this that although the lifting time t is approximately the same _from the main contacts K1 to K3, the current flowing in these lifting operations is in principle different. As an approximation, the following can be used for the flowing current in the main contact arrangements Kl, K2, K3 during the bounce removal:

iu = C " ^• sin (Ψκ + ^^ • 360 ° + 240 °) T in = C "• sin (V. 360 ° + 120 °)

iu = C "• sin (Ψκ 4- ^l Ϊ. 3 ₆ o °) r

C "is a constant dependent on the load 3 to be switched and the mains voltage.

Thus, the main contacts Kl, K2, K3, two processes are at the burnup involved, namely on the one hand each have the same for all the main contacts Kl to K3 Abhebedauer _t, and on the other hand for all i main contacts Kl to K3 respectively different height of the arc current. This is also evident from the experimentally determined course of the relative bounce charge Q of the three main contacts K1, K2, K3 which is dependent on the switch-on command angle Ψ _{κ and is} shown in FIG. The relative bounce charge Q is the actual bounce charge related to the effective value of the nominal current.

In the dependence of the relative bounce charge Q on the switch command angle Ψ _κ shown in FIG. 6, the control voltage U _{s is} in turn coherent with the outer or phase conductor L3. In addition, the mean value of the three relative impact charges Q is drawn in there in the form of a line marked with crosses. This line marked with crosses has minima in the range around Ψ _κ = 50 ° and Ψ = 85 °, which are clearly below the average value of the bounce charge Q. The areas around these minima are therefore potential areas for preferred switch-on command angles Ψ _κ .

This means that the preferred switch-on _{command angles are} Ψ _Ki = 55 ° for the phase conductor L1, Ψ _κ2 = 80 ° for the phase conductor L2 and Ψ _κ3 = 65 ° for the phase conductor L3. The reason for this is that for these switch-on command angles Ψ _κ the relative bounce charge Q of an assigned main contact Kl.K2.K3 each has a local minimum and also the mean value of the bounce charges Q of all three main contacts K1, K2, K3 is lower than the average is. The control phase is changed so that the control or coil voltage Us phase-synchronized z. B. to phase or external line Ll, the preferred switch-on command angle Ψ _κ are to be _rotated accordingly.

Overall, the switching on of an alternating current driven, electromagnetically operated contactor 1 is influenced by utilizing its specific properties in such a way that on the one hand the switching synchronization effect is avoided and on the other hand the erosion of the main contacts K1, K2, K3 is reduced overall.

Claims

claims

1. A method for reducing the contact erosion of a switching device (1), in which a switch-on command (ES) for the electromagnetic actuation of its main contacts (Kl to K3) to initiate a switching process until the phase angle (Ψ) of the control voltage is reached ( U _s ) of a command angle (Ψ _V ) related to the magnet system (4) coupled to the main contacts (Kl to K3) is delayed, which is assigned to the main contact (K1, K2, K3) with the currently most severe erosion.

2. The method according to claim 1, in which the current erosion of each main contact (K1, K2, K3) is determined by a time interval measurement during a switch-off process.

3. The method as claimed in claim 2, in which the time interval between a separation of a magnet system (4) serving for electromagnetic actuation of the main contacts (K1, K2, K3) and the separation of the main contacts (K1, K2, K3) is recorded ,

4. The method according to any one of claims 1 to 3, in which, if the command angle (Ψ _Kv ) assigned to the main contact (K1, K2, K3) with the currently greatest burn-off corresponds to the phase angle (Ψ) of the continuously detected control voltage (U _s ) of the magnet system (4) a pulse (S) for initiating the switching process is generated.

5. Device for performing the method according to one of claims 1 to 3, with a number of evaluation elements (A _Ln ) for determining the erosion of each main contact (Kl, K2, K3) of the switching device, - with a memory chip (10) in which a number of on the phase angle (Ψ) of a control voltage (O) for a Magnetic system (4) of the switching device (1) related command angles (Ψ _R V) is stored, and with a phase comparator (10), which is based on a comparison of the command angle assigned to the main contact (K1, K2, K3) with the currently strongest erosion (Ψ _K v) with the phase angle (Ψ) of the detected control voltage (U _s ) of the magnet system (4) generates a pulse (S) to initiate the switching process.

6. The device according to claim 5, with a flip-flop (13) connected downstream of the phase comparator (13) which, with the pulse (S) generated by the phase comparator (11), sends the switch-on command (ES) to a control line (5) of the magnet system (4 ) arranged switch (6) passes.

7. The device according to claim 5 or 6, wherein the phase comparator (10) for determining the phase angle (Ψ) of the continuously detected control voltage (U _s ) with a phase output connected to one of the phases (L1, L2, L3) of a three-phase network ( 2) of the switching device (1) is connected.

8. Device according to one of claims 5 to 7, in which each evaluation element (A _Ln ) on the one hand via a measuring line (7) for detecting the voltage (U _n ) across the respective main contact (Kl, K2, K3) and on the other hand with a measuring line (8) for detecting the control voltage (U _s ) of the magnet system (4) is connected.

9. Device according to one of claims 5 to 8, with a function _block connected to the evaluation elements (A _Ln )

(9) to determine the main contact (Kl, K2, K3) with the currently strongest erosion.

10. Device according to one of claims 5 to 8, wherein the pulse train (T / 2) of the pulse from the phase comparator (11) generated pulse (S) corresponds to half a network period.