EP1927121B1 - Method for determining contact erosion of an electromagnetic switching device, and electromagnetic switching device comprising a mechanism operating according to said method - Google Patents

Description

The invention relates to a method for determining the burnup of contacts of an electromagnetic switching device. In addition, the invention relates to an electromagnetic switching device with a device for determining the erosion of its contacts.

When switching an electromagnetic switching device on and off, arcs occur between the closing or opening contacts. These cause over time a burnout of the contacts. For the reliability of such a switching device, it is therefore important to know the extent of this burn, to conclude from it to the remaining life of the switching device and to avoid malfunctioning by timely replacement of the contacts can.

From the EP 0 694 937 B1 is a method for determining the burnup and thus the remaining life of contacts in switching devices known in which the measure of the contact erosion so-called contact pressure or through pressure is determined. This pressure is the distance traveled by the armature as an actuator of the switching movement between the beginning of the turn-off, ie the time in which the magnetic armature resting in the end position on a magnetic yoke detaches from this, and the time in which the Differentiate contacts. The timing of lifting of the armature from the yoke is measured with an auxiliary circuit in which the armature and the yoke form a switch which is closed when the armature and magnetic yoke touch.

Alternatively, it is for example from the EP 0 878 015 B1 known to determine the time of separation of the armature from the magnetic yoke of the magnetic drive by measuring the voltage across the magnetic coil of the magnetic yoke.

Furthermore, from the WO 03/054895 It is known to determine the burnup from closing times of the switching device, which in turn are determined from electrical variables.

From the DE 10260248 A1 Methods are known for determining the remaining life, in which a measurement of time intervals is made during the shutdown.

In both methods, to detect the time of lifting the contacts, a further auxiliary circuit is required, for example, a complex, galvanically decoupled with the aid of optocouplers from the main circuit auxiliary circuit which detects the occurrence of an arc voltage, which is formed by the forming arc when lifting.

Alternatively to the from the EP 0 694 937 B1 and EP 0 878 015 B1 known method, in which the turn-off is used to determine the burn-up or the remaining life, is from the WO 2004/057634 A1 a method and a device for determining the remaining life of a switching device known in which the change in the pressure during the switching, ie when closing the switch contacts by the magnetic drive, is measured. In this known device, a position sensor is arranged on the armature, which contains at least three positions markings, for example in the form of measuring contacts, with which the time course of the magnetic armature movement can be detected. The position determination of the magnet armature when closing the contacts is determined by calculation from the movement sequence of the magnet armature detected with the aid of these position markers. For this purpose, due to the small number of position marks, a simple algorithm is used on the assumption that between a time before closing the contacts and a Time, which is between the closing time of the contacts and the touchdown of the armature on the magnetic yoke, the anchor acceleration is constant. In practice, however, it has been found that with such an approach, the timing of closing the contacts can be determined only with low accuracy.

The invention is based on the object to provide a method for determining the erosion of contacts of an electromagnetic switching device, with an accurate determination of the time in which close the contacts, and thus an accurate determination of the contact erosion is possible. In addition, the invention is based on the object to provide an electromagnetic switching device with a device operating according to this method.

With regard to the method, the object is achieved according to the invention with a method having the features of claim 1. In this method, a time characteristic of the relative movement caused by an actuator between the contacts mechanical variable is measured during switching on, and it is by Evaluation of this time course determines the time at which close the contacts, and which is detected by the contacts or the distance traveled by the actuator from this point to its end position distance is at least indirectly detected and compared with a stored reference value.

The invention is based on the consideration that the time course of the relative movement is significantly changed at the time of closing the contacts due to the beginning at this time and the movement of the actuator decelerating high spring force of the contact spring, so that with an analysis of the time course of Movement the time of the meeting of the contacts can be safely determined immediately without the need for this an approximation model of the movement, as in the above-mentioned WO 2004/057634 A1 the case is.

The variable characterizing the movement can be made directly by measuring the speed or the acceleration of one of the contacts or both contacts. Alternatively, the speed of this relative movement causing and with at least one of the contacts mechanically coupled and actuated by an electromagnetic actuator actuator are measured.

The time course of the movement is measured with a mechanically coupled to the actuator sensor, whereby the measurement can be done with a measuring circuit which is galvanically decoupled from the switched circuit or the circuit of the magnetic drive.

The sensor is a displacement sensor, a speed sensor or an acceleration sensor.

If a speed sensor or an acceleration sensor is used as the sensor, the time of the contact closure can be determined particularly easily from its measuring signal. In order to obtain information about the distance covered in this case, their measuring signals must still be integrated simply or twice.

The object related to the electromagnetic switching device is achieved according to the invention with the features of claim 7, the advantages of which as well as the advantages of specified in the recited in this claim subclaims mutatis mutandis correspond to the advantages that are given to the characteristics of the respectively associated method claims ,

Figuren 1 bis 3

jeweils ein elektromagnetisches Schaltgerät in einer Prinzipdarstellung zu verschiedenen Zeitpunkten des Einschaltvorganges bei unverbrauchten Kontakten,

Figuren 4 bis 5

das elektromagnetische Schaltgerät zu verschiedenen Zeitpunkten des Einschaltvorganges nach einer Vielzahl von Schaltzyklen, wenn die Kontakte einen signifikanten Abbrand aufweisen,

Figuren 6 bis 9

jeweils Diagramme, in denen die Spannung über der Magnetspule und der durch sie flieβende Strom, die Magnetkraft und die Federkraft, der Abstand zwischen Magnetanker und Joch und die Geschwindigkeit des Magnetankers bzw. seine Beschleunigung jeweils gegen die Zeit aufgetragen sind, und

Figur 10 in

schematischen Darstellung ein Schaltgerät mit einer Einrichtung zur verbesserten Bestimmung des Abbrandes der Kontakte.

For further explanation of the invention reference is made to the drawing. Show it:

FIGS. 1 to 3

in each case an electromagnetic switching device in a schematic representation of different Times of switching on with unconsumed contacts,

FIGS. 4 to 5

the electromagnetic switching device at different times of the switch-on process after a plurality of switching cycles, when the contacts have a significant burnup,

FIGS. 6 to 9

respectively diagrams in which the voltage across the solenoid and the current flowing through it, the magnetic force and the spring force, the distance between the armature and yoke and the speed of the armature and its acceleration are plotted against time, and

FIG. 10 in FIG

schematic representation of a switching device with a device for improved determination of the erosion of the contacts.

According to FIG. 1 contains an electromagnetic switching device, in the example shown, a contactor, a magnetic yoke 2, on which two magnetic coils 4 are arranged for magnetic excitation. An armature 6 associated with the magnetic yoke 2 is spring-mounted by compression springs 8 in a housing 10 of the switching device which is illustrated only symbolically. Magnetic yoke 2, solenoid 4 and armature 6 form an electromagnetic drive of the switching device. The armature 6 is non-positively connected via a contact spring 12 with a movable contact bridge 14. The movable contact bridge 14 are associated with two fixed contact carrier 16. The magnet armature 6 forms the actuator of the magnetic drive for the relative movement between the contact bridge 14 and the contact carrier sixteenth

The contact bridge 14 and the fixed contact carrier 16 are each provided with contact pieces or contacts 18 which have a thickness D ₀ in the new state. The switch contact formed by the movable contact bridge 14 and the fixed contact carrier 16 is in open Position. In this switched-off state, the contacts 18 are at a distance S ₀ and the pole faces 20 and 60 of the magnetic yoke or the magnet armature 6 are located at a distance H.

When switching on the magnetic coils 4, the armature 6 is against the action of the compression springs 8 in the direction of the magnetic yoke 2 in motion, as illustrated in the figure by the arrows.

FIG. 2 now shows a situation in which the contacts 18 touch the first time, the armature 6 has thus covered a distance S ₀ . At this time, the pole faces 20, 60 are at a distance d ₀ = Hs ₀ . This distance d ₀ corresponds to the through-pressure of the switching device in unconsumed contacts 18. The further closing movement of the armature 6 is now against the action of the contact spring 12 and the parallel-connected compression spring 8. Since the spring force exerted by the contact spring 12 is significantly greater than that of the spring 8 exerted spring force, the force acting on the armature 6 spring force increases abruptly and causes a significant change in the course of the closing movement.

In the further course, the force acting on the armature 6 magnetic force is greater than the force exerted by the compression spring 8 and the contact spring 12 spring force, and the armature 6 can continue to move in the direction of the magnetic yoke 2 until finally, as in FIG. 3 is shown, rests in an end or rest position with its pole faces 60 on the pole faces 20 of the magnetic yoke 2.

In FIG. 4 is now shown a situation in which the contacts 18 are already significantly burned after a plurality of switching cycles, and only have a thickness D ₁ <D ₀ . Accordingly, the contact pieces 18 are in the off state at a distance s ₁ which is significantly greater than the distance s ₀ in the new state. If now the magnetic coils 4 are energized, ie the switch-on initiated, moves the armature 6 with increasing speed in the direction of the magnetic yoke 2, until after this distance s ₁ corresponding distance according to FIG. 5 touch the contacts 18 for the first time. This is the case at a distance d _{1 of} the pole faces 20, 60, for which likewise d ₁ = Hs ₁ . The figure can be seen now that this distance d ₁ , that is, the through pressure due to the small thickness D _{1 of} the contacts 18 is significantly reduced compared to the through-pressure in the new state.

In the diagram according to FIG. 6 is the current flowing through the solenoid current I (curve a) and applied to the solenoid clocked DC voltage U (curve b) plotted against the time t. In the example shown, it is a switching device with an example of the WO 2005/017933 A1 is controlled by known methods to adjust the closing speed by which the contacts on the one hand and the poles on the other hand, by controlling the acceleration of the armature. From this figure, it can be seen that the current I decreases steadily until the time t _k of closing the contacts in order to rise again at short notice from this point in time t _k . This increase is necessary in order to compensate for the suddenly increased spring force acting on the magnet armature from the time t _k by a correspondingly higher magnetic force.

This is clear in the diagram according to FIG. 7 to recognize. In this diagram, the magnetic force F _M (curve c) and the spring force F _s (curve d) is plotted against time t. At the time t _{k of} the contact closure, the spring force F _s increases abruptly. For a short time, this increase can not be compensated by the magnetic force. Only in the further course can the magnetic force again exceed the spring force.

In the diagram according to FIG. 8 the path s of the magnet armature (curve e) and its velocity v (curve f) are also plotted against time t. At the beginning of the switch-on process, the magnet armature (actuator) is located with its pole faces at a distance H from the pole faces of the magnetic yoke. The velocity v at which the magnet armature moves towards the magnetic yoke increases steadily after a certain time delay with an approximately constant acceleration. The reason for this is the above-mentioned control of the armature movement, which ensures that the speed of the magnet armature does not become too large. At the closing time t _k , ie after the armature and thus the contacts have covered a distance w = s, the speed v rapidly decreases to a minimum, and then due to the again increasing magnetic force F _M to the target value of about 0, 5 m / s increase. This breaking in of the speed v, which occurs due to the spring force F _s increasing by leaps and bounds, is a significant indication of the closing time t _{k of} the contacts. This closing time t _k is then the time t at which v (t + δt) <v (t). At the closing time t _k , the magnet armature is at a distance d from the magnetic yoke. This distance d corresponds to the existing pressure. The armature (actuator) lays back to its final position still a distance that corresponds to this distance d.

In Fig. 9 the acceleration b of the armature is plotted against time in a logarithmic scale. It can be seen from the curve g that the acceleration b rises rapidly to an approximately constant value and undergoes a sign change at the time of the contact closure due to the speed drop. This change of sign can be particularly easily recognized in an evaluation of the time course of the acceleration b and used to determine the closing time t _k .

In the FIGS. 6 to 9 Diagrams shown are used to exemplify the present when switching an electromagnetic switching device physical conditions. The in FIGS. 8 and 9 shown speed or sign change of acceleration also results when the electromagnetic switching device operated unregulated or by another control method becomes. If, with the aid of a suitable sensor, the speed v or the acceleration is detected either directly by a speed sensor or an acceleration sensor, the closing time t _k can be determined particularly easily from the curve of the latter. In principle, the closing time t _{k can} also be derived from a signal measured by a displacement sensor by differentiating it once or twice.

According to FIG. 10 is in a switching device according to the invention to the armature 6 directly a sensor 22 coupled, which may be designed as a speed sensor, acceleration sensor or displacement sensor. With this sensor 22, the relative movement of the contacts 18 is detected indirectly and evaluated in an evaluation device 25. In the evaluation, the time t _{k is} mediated by the change of the acceleration b or the collapse of the speed v. The remaining distance d (through-pressure) or the distance s covered up to this time t _k can be removed from the path-time course w (t) of the actuator (armature 6) immediately. In this case, the evaluation device 25 can also take over the differentiation or integration of the movement signal generated by the sensor 22.

Alternatively, a sensor 24 may be disposed on the movable contact bridge 14. In the case of a displacement sensor, the distances s ₀ and s ₁ can be measured directly. In the case of a speed sensor, the speed v can be determined directly as a function of time. In this case, the closing time t _{k is} the time when the movement ends and the speed v of the movable contact 18 becomes zero.

In the exemplary embodiment, the sensors 22, 24 are mechanically coupled to the moving parts-armature 6 or movable contact 18. Basically, however, non-contact sensors can be used, the distance of the relevant moving part to a fixed housing part.

If the time t _k of closing the contacts is known, depending on the sensor used, either the distance s traveled by the armature 6 and thus by the contacts 18 can be determined either directly or indirectly.

unter der Voraussetzung, dass sich der Abbrand D₀-D₁ auf die einander gegenüberliegenden Kontakte gleichmäßig verteilt. Mathematisch äquivalent hierzu kann auch aus der Wegstrecke s₁ der Abstand d₁ der Polflächen von Magnetjoch und Magnetanker berechnet werden. Dieser ergibt sich dann durch die Differenz aus dem gespeicherten Wert H für den Abstand der Polflächen im geöffneten Zustand und der zurückgelegten Wegstrecke mit $${\mathrm{d}}_{\mathrm{1}}=\mathrm{H}-{\mathrm{s}}_{\mathrm{1}}$$

Is for the example of Fig. 4 the distance s ₁ known, can be concluded by comparison with a stored reference value s ₀ directly on the burn D ₀ -D ₁ and thus also on the remaining life of the contacts. For the burn D ₀ -D ₁ , the relationship $${\mathrm{D}}_{\mathrm{0}}-{\mathrm{D}}_{\mathrm{1}}=\left({\mathrm{s}}_{\mathrm{1}}-{\mathrm{<figure-callout\; id="0"\; label="s"\; filenames="imgf0003.png"\; state="\{\{state\}\}">s</figure-callout>}}_{\mathrm{0}}\right)/0$$

provided that burnup D ₀ -D _{1 is} evenly distributed between the opposing contacts. Mathematically equivalent to this, the distance d _{1 of} the pole faces of the magnetic yoke and the magnet armature can also be calculated from the distance s ₁ . This is then given by the difference from the stored value H for the distance of the pole faces in the open state and the distance traveled with $${\mathrm{d}}_{\mathrm{1}}=\mathrm{H}-{\mathrm{s}}_{\mathrm{1}}$$

For the burn D ₀ -D ₁ then applies $${\mathrm{D}}_{\mathrm{0}}-{\mathrm{D}}_{\mathrm{1}}=\left({\mathrm{d}}_{\mathrm{0}}-{\mathrm{d}}_{\mathrm{1}}\right)/\mathrm{Second}$$

If the distance d ₁ measured directly as the distance traveled by the actuator (armature) from the time t _k to its final position, the burn D ₀ -D ₁ can be calculated directly with the above equation, if the distance d ₀ (pressure ) is stored as uncommitted contacts as a reference value.

Claims (2)

1. Method for determining the erosion of contacts (18) of an electromagnetic switching device, in which

   - during the switch-on operation, a mechanical variable (v, b, w), which characterizes the time profile of the relative movement, which is caused by an actuator, between the contacts (18), is measured,

   - the variable (v, b, w) is measured by a sensor (22), which is coupled mechanically to the actuator, wherein a velocity sensor, an acceleration sensor or a displacement sensor is used as the sensor (22),

   - the time (t_k) at which the contacts (18) close is determined by evaluating the time profile of the relative movement,

   - the distance (s, s₀, s₁, d, d₀, d₁) covered up to this time (t_k) by the contact(s) (18) or that covered from this time (t_k) by the actuator up to its end position is detected at least indirectly and is compared with a stored reference value.
2. Electromagnetic switching device with a device for determining the erosion of its contacts (18), with

   - a measuring device for measuring a mechanical variable (v, b, w), which characterizes the time profile of the relative movement, which is caused by an actuator, between the contacts (18), wherein the measuring device comprises a sensor (22), which is coupled mechanically to the actuator, for measuring the variable, and wherein the sensor (22) is a velocity sensor, an acceleration sensor or a displacement sensor,

   - an evaluation device for determining the time (t_k) at which the contacts close from the time profile of the relative movement and for at least indirectly detecting the distance (s, S₀, S₁, d, d₀, d₁) covered up to this time (t_k) by the contact (s) (18) or that covered from this time (t_k) by the actuator up to its end position, and for comparing this distance (s, s₀, s₁, d, d₀, d₁) with a stored reference value (s₀).

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