WO2004057634A1

WO2004057634A1 - Method and device for determining the remaining service life of a switchgear

Info

Publication number: WO2004057634A1
Application number: PCT/DE2003/004173
Authority: WO
Inventors: Norbert Elsner; Reinhard Maier; Fritz Pohl; Bernhard Streich
Original assignee: Siemens Aktiengesellschaft
Priority date: 2002-12-20
Filing date: 2003-12-17
Publication date: 2004-07-08
Also published as: DE10260249A1; DE10260249B4; CN1745443A; EP1573761A1; EP1573761B1; CN100413004C; DE50307262D1

Abstract

In a switchgear, the switching contacts of a switchgear mechanism (100) are set to the on position or the off position, wherefore pressure is generated by the contact force spring in order to apply the pre-determined contact force in the on position. The service life of one such switchgear is determined by the erosion of switching contacts and by the mechanical wear of the switchgear mechanism. It is known that the switching contact erosion can be determined by detecting the change in pressure in the drive of the switchgear, According to prior art, the change in pressure is always measured during the switching-off process. According to the invention, the pressure change is detected during the switching-on process, and especially the mechanical wear of the switchgear can be simultaneously determined. The inventive device comprises a magnetic drive (100) consisting of an armature (110), a yoke (101) and magnetising coils (102, 102'), a position transmitter (120) being coupled to the magnetic armature (110) in a positively engaging manner.

Description

description

Method and device for determining the remaining service life of a switching device

The invention relates to a method for determining the remaining service life of a switching device according to the preamble of patent claim 1. In addition, the invention relates to an associated device according to the preamble of patent claim 10.

For the operational safety of switchgear, it is important to know the remaining service life of contact pieces in order to take timely maintenance measures, e.g. in the case of contactors, by exchanging the contacts to avoid malfunctions. Previously known methods evaluate the time sequence during the switch-off process. For contactors, especially air-riflemen, a method for detecting the remaining service life of contact erosion was developed, in which the erosion by measuring the time interval between armature opening - characterized by a characteristic peak in the coil voltage - and contact opening - characterized by the occurrence of a switching path voltage - the contact erosion and thus the Remaining life is measured.

EP 0 694 937 B1, in particular, protects the process for recording the change in through-pressure as a replacement criterion for contact erosion. Specific methods for use in switching devices are described in EP 0 878 016 B1, EP 0 878 015 B1 and EP 1 002 325 Bl. It is consistently based on the fact that the pressure changes during the switch-off process, ie when the switch contacts are opened, are recorded by an electromagnetic drive, from which the erosion of the switch contacts is determined and the remaining service life of the switching device is determined therefrom. Based on this, it is an object of the invention to provide a method and the associated device in which, in addition to the contact erosion, the wear of the switching device mechanism can also be taken into account under certain conditions. In addition, it is possible to monitor and control the switch-on movement with the recorded measured values.

The object is achieved in a method according to the preamble of claim 1 according to the invention by the characterizing feature. An associated device is specified in claim 10. Further developments of the method and the associated device are the subject of the dependent claims.

According to the invention, the changes in through-pressure are now recorded specifically during the switch-on process, i.e. when the switching contacts are closed by the magnetic drive. For the purpose of the associated device, a position sensor is coupled to the magnetic armature of the magnetic drive in the non-positive contact.

It is advantageous with the invention that not only the contact erosion can be taken into account as the variable that essentially determines the service life of the switching device, but also the wear of the device mechanism. This can be important if the switching device is specifically a vacuum contactor. While the contact stroke is relatively large (up to 10 mm) for air-riflemen and the play caused by the wear of the moving components of the device mechanics is negligible as a percentage, this can be a not insignificant quantity for vacuum-riflemen.

The latter is given by the fact that the contact stroke with vacuum switches compared to air switching devices is comparatively small (up to 2 mm), but due to the contact closing force caused by the application of force to the device mechanics and a force redirection and force transmission that can only be achieved via levers is generated, signs of wear at pivot points and the like can easily occur.

Further details and advantages of the invention result from the following description of the figures of exemplary embodiments with reference to the drawing in conjunction with the patent claims. Show it

1 shows a graphical representation for calculating the contact closing position during the switch-on process, FIG. 2 shows a magnetic drive for a switching device with a position sensor, FIG. 3 shows a specific design of the position sensor from FIG. 2 for determining individual position times,

FIG. 4 shows an arrangement for a concretized to FIG

Air contactor for determining contact closing positions x ₃ , x ₃ _new the position _times and Figure 5 is a flowchart for arithmetically determining the contact _{life of a switching device} .

The method described below for determining the remaining service life of switching contacts essentially consists in the temporal recording of predetermined, discrete positions of a magnet armature of a contactor drive and / or certain components of the switching device drive, and in determining the speed and (average) acceleration of the component to which the position measurement is made, at these predetermined positions. In addition, there is the measurement of the switch-on times of the switching contacts during their closing movement and the determination of the contact closing positions relative to the detected, discrete positions.

FIG. 1 shows schematically the path-time profile 1 of a component of the switching device, the path of which is identical to the contact path, the path of which is either via a constant constant factor or can be mathematically linked to the contact path via a predetermined function.

To determine the remaining service life, at least four points in time are recorded, one of which, for example t ₃ , represents the point in time at which the contact closes and the other, for example ti, t and t _{4, represent} position times of one or more position sensors. At least two of these times, for example ti and t ₂ , can be time values of two closely adjacent positions, from which a speed value of the component can be derived from the relationship v = (x ₂ -xι) / (t ₂ -tι) (1). Since the monitored component generally performs an accelerated movement during the switch-on process, an average value of a constant acceleration is determined in addition to the speed v for at least one time interval, for example Δt = t-tι or Δt = tt ₂ . The position of the closing contact can be determined for the contact closing time t ₃ from the determined values of the speed and the acceleration, as well as from the relative positions of the position transmitters to one another and their position times.

The still unknown contact closing position between the position x ₂ , which represents the end of the path interval for determining the speed, and the position x ₄ , which lies in the closing direction of the component after the contact closing position, is unknown. It can be seen that the closer the contact interval x ₃ can be determined, the more precisely the path interval between the positions x _x and x is chosen. Ideally, the positions xi and x should be selected so that they securely enclose the contact closing position, which changes due to wear of the contact and / or mechanics, but the path interval between them does not become significantly larger than the difference between the contact closing positions at the beginning and at the end of the contact life. There are several alternative methods for solving the position / time detection, for which the structure of the switching device drive is discussed:

A known magnetic drive for a switching device is shown in FIG. It consists in a known manner of, for example, an E-shaped magnetic yoke with magnetic coils and a magnetic armature.

In Figure 2, an associated switching device is specifically a contactor. This can be an air contactor but also a vacuum contactor, in the latter case the linkage of the drive to the moving contacts of the contactor is more complex.

In Figure 2, a magnet och 101, on which two solenoids 102 and 102 ^x sit for magnetic excitation. The pole faces of the magnetic yoke are designated 103 and 103 '. A magnet armature 110 is assigned to the magnet yoke 101, which armature is attracted by the magnet yoke when the magnet drive is excited by the magnet coils.

The full opening position of the magnet armature 110 is shown in FIG. A carrier 130 for a moving contact 141 is arranged on the magnet armature, the carrier 130 being movable in the vertical direction in FIG. 2. When the drive is switched on, the moving contact 141 is brought into the closed position to the fixed contact 151.

In the figure 2 is on the other facing the magnetic yoke

On the side of the magnet armature, a position sensor 120 is arranged in frictional contact with the magnet armature 110. The position transmitter 120 essentially serves to record specific positions at the time of the armature movement and is described in detail in the further figures. FIG. 3 shows the magnetic drive with a specific embodiment of a position sensor 120, the advantages of which lie in its simplicity, robustness and the precision in detecting the predetermined positions. As can be seen from FIG. 3, the number of positions that can be predetermined in terms of construction can be considerably higher than the minimum number of three positions, ie (i, x ₂ and x ₄ ). The position transmitter 120 is designed as a cylindrical rod, which is pressed against the magnet armature 110 by a spring 125 with moderate spring force and can be moved in an associated housing. In the switched-off state of the magnetic drive 100, the position transmitter 120 bears against the armature 110, as a result of which, when the armature 110 is switched on, the position transmitter is carried along and acceleration forces act on it, but no impact forces. The cylindrical surface of the position sensor is divided into several conductive and non-conductive surface sections in the axial direction. Since the outer diameter of all surface sections is identical and they adjoin one another without a joint, a smooth cylinder surface is obtained from electrically conductive and non-conductive sections alternating in the axial direction.

Such an electrically conductive section can e.g. be a highly conductive, metallic ring, the height of e.g. Can be 1mm or less. The position can be detected by electrically contacting external contact members with this metal ring.

In order to keep the mechanical wear due to abrasion between the contact members and the ring small, the contact can be realized by a rolling contact instead of by a sliding contact. An electrical measuring circuit is connected to this measuring contact, which derives a voltage signal (on / off) from the contact signal (on / off). If, for example, the momentary closing speed of the component is lm / s, the measuring contact supplies the 1 mm as it passes high. Metal ring points in time of the switching edges of the voltage signal, which have a time interval of 1 millisecond. A time signal can therefore be taken from each segment boundary of the surface sections. The position sensor 120 according to FIG. 3 thus supplies an alternating square-wave voltage signal which coincides in time with the conductivity signal generated at the measuring contact of the segmented cylinder jacket surface passing by.

FIG. 4 shows the contact apparatus 40 of an air contactor and the armature 110 with the position transmitter 120 on one side and the bridge girder 130 on the other side corresponding to FIG. 3. The movable part of the contact apparatus with its components is introduced on the bridge support 130. In detail, a contact bridge 140 with moving contacts 14, 14 'is attached to a spring housing 160 with counter bearing 161, the contact bridge 140 being supported against the bridge carrier 130 by a contact force spring 165 when the contacts are open. As a result of this arrangement, the moving contacts 141, 141 are movable relative to the fixed contacts 151, 151 ', which are fastened on contact carriers 150, 150', and can be brought into the open or closed position. The contact force spring 165 generates the contact force and the closed positions of the armature and contact bridge determine the pressure of the spring.

The geometrical relationships which determine the position instants ti to t result from FIG. 4, the same reference numerals as in FIG. 3 being used. Essential lent in this context to determine the encoder position x ₃ n _ew i ™ when new contacts and encoder position x ₃ in the working condition of the contacts. The placemarks xι (tι), x ₂ (t ₂ ) and x (t ₄ ) are also shown. The contacts are designed as contact rings 122 to 124 or 125, 125 'around the cylindrical position sensor 120. It may also be sufficient to coat the surface 121 of the position sensor 120. To determine the position of the contact when making contact, the speed between the closely adjacent positions xi and x ₂ and the average acceleration between xi and x _{4 are} required. The following applies:

v = (x ₂ -xι) / (t ₂ -tι: (1)

X ₄ -X ₁ = v * (t ₄ -t ₁ ) + 0.5 * b _m * (t ₄ -t ₁ )% (2.1) b _m = 2 / (t-tι) * ((X4-X1 ) / (t ₄ -tι) - (x ₂ -xι) / (t ₂ -tι)) (2.2)

This gives the contact closed position x ₃

X ₃ -X ₁ = v * (t ₃ -tι) + 0.5 * b _m * (t ₃ -tι) ² , (3.1)

X ₃ -X ₁ = (x ₂ -Xι) / (t ₂ -tι) * (t3-tι) + ((x ₄ -xι) / (t ₄ -tι) -

(x ₂ -xι) / (t ₂ -tι)) * (t ₃ -t ₁ ) ² / (t ₄ -t ₁ ). (3.2)

It can be seen that only the differences in the measured contact times ti and the known position values are required to calculate the change in the contact closing position. A spatial adjustment for the determination of absolute position values is therefore not necessary.

In the new state of the contacts with the position sensor, the measured values of the Component positions and the contact switch-on can be calculated to a path (x ₃ -xι) _newly on a microprocessor. Contact wear, possibly with mechanical wear, gives a current value of the travel (x ₃ -xχ) in switching operation.

The wear, for example in mm, is given by the difference between the calculated distances (x ₃ -xχ) - (x ₃ -xι) _n eu. In the case of contact burn-off, this difference corresponds to the decrease in through-pressure by reducing the contact piece thickness. If there is also a decrease in pressure through wear of mechanical, power-transmitting parts of the device drive, the mechanical, pressure-related decrease in pressure is included as part of the total decrease in pressure, since the contacts and the drive components are in positive contact during the accelerated switch-on movement. The computational procedure is illustrated in FIG. 5 using a flow chart. The individual steps 201 to 212 are largely self-explanatory: the times t ₂ , t ₃ and t ₄ are determined according to position 205 by starting and presetting switchgear encoder data corresponding to positions 201 and 202. From this, the output values x ₃ (t ₃ ) and xι (tχ) or their difference x ₃ -xι can be calculated according to the position. The difference (x ₃ -xι) new- (x ₃ -xι) results in the current change in print through according to position 210. According to position 211, the change in print through is correlated with the end of the service life of the contacts and when the specified conditions are fulfilled according to position 212 Program ended. If this is not the case, a return is made to position 203 and ti, t ₂ and t ₃ are determined anew in accordance with positions 204, 205. Positions 206 and 208 indicate test routines for averaging x ₃ -xι.

After reaching the end of the contact life and installing new contacts, the current value (x ₃ -xι) is _newly determined at the beginning of a new life cycle, which implicitly contains the current state of wear of the switchgear mechanism. This ensures a reliable assessment of contact wear in every subsequent life cycle.

A particularly advantageous further development of the procedure described above is a speed control of the drive: For speed-controllable drives, in particular contactor drives, which consist of a controllable, magnetic drive, the speed v measured with the position sensor can be used to iteratively drive the drive to a predetermined value Set speed or limit the speed to a specified range of values. For this purpose, the control parameters are set each time the drive is switched on with a predetermined parameter step in the direction of higher speed, as long as the speed is lower than the target value or is below the target range, or is set in the direction of lower speed as long as the speed is higher than the target value or is above the target range. This ensures that the contacts close at the specified speed after the speed setting has been reached.

An alternative to the procedure described above is obtained by determining two times t _Be gmn and t _Ende for the sequence of the switch-on process and the remaining service life calculated therefrom. The following mean: _Be g _mn = the point in time at which voltage is applied to the coil either - taking into account the phase position of the voltage to record the different development of forces or using a phase-controlled connection, which serves to bring about synchronism. t _end = detection of contact closure, for which purpose the switching path voltage is measured.

A particular advantage is that the method can be used on existing shooters. However, this requires the detection of the voltage form with an A / D converter or zero crossing detection at the control voltage.

To evaluate the Einschaltweges from the times t _Be g _ιnn and t _En d _{e is} the predetermined and empirically determinable path-time curve is taken of the magnetic drive according to FIG. 1 The change in the switch-on distance in the state of use with respect to the new state then provides a direct or proportional measure in the change in the contact piece thickness. Alternatively, the determination of two other points in time t _Be gi _nn and t _{the end} of the sequence of switch-on and calculated therefrom residual life. The measured variables are defined as follows: te _e gi _nn = time of contact closing, for which purpose the switching path voltage is measured. t _End = Detection of a waypoint, either when the magnet system closes, whereby the measurement is carried out, for example, by applying a voltage, the yoke-armature movement and a voltage zero value is measured, or a switch is attached to the magnet system or any waypoint.

A pressure value of the contact force spring is determined from the path-time curve of the magnetic drive, which is empirically predetermined in accordance with FIG. 1, and the wear-related change in pressure is determined from its change in the use state. The advantage of this method is the simple detection of the time stamps. However, a modification of the contactor structure and thus a new design may be necessary for the method.

In the case of the first alternative, the drive can be speed-controlled in an advantageous manner as follows: by means of several position rings on a position transmitter, it is possible to measure the path during armature movement and to achieve an almost constant speed for closing the switching device by controlling the magnetic force. This not only optimizes the switching movement, it also minimizes the wear-causing forces on the mechanically moving parts as much as possible.

Claims

claims

1. Method for determining the remaining service life of a switching device, with switching contacts which are brought into an on or off position by a switching device mechanism, a contact force or pressure being produced in order to apply a predetermined contact force in the on position, and the service life being caused by a switch contact erosion on the one hand and mechanical wear of the switchgear mechanism is determined on the other hand, and in particular the switch contact erosion takes place by detecting the change in pressure in the drive of the switchgear, characterized in that the change in pressure when the switchgear is switched on is detected and that the switch contact erosion on the one hand and the mechanical wear on the switchgear mechanism on the other hand by the Detection of the change in pressure can be determined when switching on.

2. The method according to claim 1, characterized in that a time determination of predetermined positions of the movable components of the switching device mechanics of the switching device is carried out for pressure detection.

3. The method according to claim 1, characterized in that the determination of the speed and / or the acceleration of movable components of the switching device mechanism on the one hand and a measurement of the switch-on times of the switching contacts during their closing movement is carried out for through-pressure detection.

4. The method according to any one of the preceding claims, characterized in that the speed of the movable components is regulated during the switch-on process.

5. The method according to any one of the preceding claims, characterized in that one or more position transmitters are present, with which at least three points in time are determined at three positions.

6. The method according to claim 5, characterized in that the closing speed of the / the contacts is determined from two of the positions and associated times.

7. The method according to claim 5, characterized in that the increase or decrease in the closing speed is determined from the third point in time of the third position.

8. The method according to any one of the preceding claims, characterized in that the contact position is calculated from the contact closing time.

9. The method according to claim 8, characterized in that the change in pressure is determined from the change in the contact position.

10. The device for performing the method according to claim 1 or one of claims 2 to 9, wherein the switching device is a contactor, in which the moving contacts by the magnet armature of a magnetic drive, which is formed from armature, yoke and magnetic coils, in the on or off position are brought, characterized in that a position transmitter (120) is non-positively coupled to the magnet armature (110).

11. The device according to claim 10, characterized in that on the position transmitter (120) ring contacts (122 to 124) are present for position.

12. The apparatus according to claim 11, characterized in that contact rollers (125) for position-dependent contacting are arranged on the position transmitter (120).

13. The apparatus according to claim 12, characterized in that the position sensor is designed as a cylindrical rod (120), the cylinder jacket surface (121) is divided in the axial direction into a plurality of conductive and non-conductive surface sections (122-124).

14. Device according to one of the preceding claims, characterized in that with the position transmitter from the contact closing time (t ₃ ) a relative position (x ₃ ) of the contact to the transmitter positions (x _lr x ₂ , x ₄ ) can be derived from their change a new value (X _{3 new} ) the contact _{erosion can be} determined.

15. The apparatus according to claim 14, characterized in that the remaining service life can be determined from the contact relative positions (x ₃ ) in the use state and in the new state (X _{3 new} ).

16. Device according to one of claims 10 to 15, characterized by means for calculating and displaying the remaining life of the switching device.

17. The apparatus according to claim 16, characterized in that the means comprise a computer, in the memory of which a path-time curve is stored.

18. The apparatus according to claim 17, characterized in that by detecting the start of the anchor movement (t _Be gi _nn ) when switching on and the contact closing time (t _end ) during the switching-on process, the closing path can be determined from the predetermined travel-time curve and that from a change in Closing path, the change in contact piece thickness can be calculated, the change in contact piece thickness corresponding to the erosion.

19. The apparatus according to claim 17, characterized in that from the change in the contact _closing time (t _Be g _ιnn ) and a time (t _En de) of a predetermined anchor position with the aid of the predetermined path-time curve can be determined a change in the pressure of the contact force spring can be derived.