EP2537169A1

EP2537169A1 - Method and apparatus for switching off a switch

Info

Publication number: EP2537169A1
Application number: EP11700661A
Authority: EP
Inventors: Martin Paulus; Mathias Schmidt
Original assignee: EGO Elektro Geratebau GmbH
Current assignee: EGO Elektro Geratebau GmbH
Priority date: 2010-02-17
Filing date: 2011-01-19
Publication date: 2012-12-26
Also published as: CA2789206A1; WO2011101193A1; RU2012139171A; MX2012009197A; US20130048479A1; DE102010008755A1; CN102834883A; BR112012020376A2

Abstract

In a method for disconnecting a switching contact from a mating contact in a switch which switches alternating current, a short mechanical pulse is applied to the switch with a pulse direction for disconnecting the contacts with a phase angle of approximately 13° before a next or a following zero crossing of the current. To this end, a piezoactuator is provided on the mating contact. Said piezoactuator can also measure the applied contact force, so that the pulse is triggered, in addition to said phase angle, only at a very low contact force which tends towards zero.

Description

description

Method and device for switching off a switch

Field of application and state of the art

The invention relates to a method for switching off a switch or for separating a switching contact of a mating contact and a corresponding device, which thus preferably an arc-free switching off can be achieved.

When switching off switches or when disconnecting a switching contact of a mating contact, there is often the problem that in a still flowing stream, especially in an alternating current, an arc can occur, which can delay both the separation of the contacts and the contacts damaged. Especially with an alternating current, for example 50 Hz, an arc can always remain until the next zero crossing of the current through the small contact gap when disconnecting the contacts. This can be a maximum duration of almost 10 msec. Although a theoretical possibility is a force-loaded very fast turning off the switch or disconnecting the contacts, but this is still not achieved quickly enough in practice. An arc still occurs. This also applies to special switches, as they are known for example from DE 10 2006 057 260 A1. A kind of snap spring is to ensure here when exceeding a trigger point for a quick switching. Nevertheless, it can not be avoided that on average a prescribed arc with a duration of a few msec arises.

From DE 1096453 it is known to superimpose a constantly pulsating small additional force in phase with the current in a similar switch of the force acting on the switching contact and countercontact. Thus, turning off the switch may be effected approximately at the zero crossing of the current. But it has to be constantly applied the power.

From DE 1 1 13745 a similar switch is known. Here is spoken explicitly of vibrations, which should help to prevent sticking or welding of switching contact and mating contact.

Task and solution

The invention has for its object to provide an aforementioned method and a corresponding device with which problems of the prior art can be avoided and in particular a safe and low-wear method for switching and a corresponding switch can be achieved.

This object is achieved by a method having the features of claim 1 and a device having the features of claim 13. Advantageous and preferred embodiments of the invention are the subject of the other claims and are explained in more detail below. Some of the features below are described only for the method or only for the device. However, they should be independent of both the method and the apparatus. can. The wording of the claims is incorporated herein by express reference.

It is envisaged that the switch turns AC, advantageously with a frequency of 50/60 Hz at 100 to 400 volts and current to about 16A, so in the household or industrial. According to the invention with a angle or phase angle between 5 ° and 20 °, preferably between 10 ° to 18 °, more preferably about 13 °, before a zero crossing of the current, a mechanical impulse given to the switch or a contact. In particular, this pulse has a pulse direction for separating switching contact and mating contact, and the pulse is moving in the direction in which switching contact and mating contact separate from one another. This not only generally a lighter separation of switching contact and mating contact can be achieved. In the context of leading to the invention development has been found that at such an aforementioned phase angle, an impulse on the switch, the separation of switching contact and mating contact for independent switching leads exactly in the zero crossing of the load current. The mechanical inertia of the switch or the total delay of the system causes it, that a corresponding pulse just before the zero crossing of the current at a sufficiently small contact force, as occurs in the expected switching off the contact separates the contacts.

Is the applied contact force, the switch contact and mating contact pressed against each other, still sufficient or very large, so the short pulse can not align anything or the contacts remain connected. Only when a certain contact force threshold is exceeded and is triggered with the specified phase angle of the pulse, the separation of the contacts takes place at the next zero crossing of the current. A particularly advantageous phase angle found within the scope of the invention is about 13 °. With slower systems it can be a bit higher it may also be less in nimble or less sluggish systems, for example more in the direction of the aforementioned 5 ° or of the said 10 °. The determination of the correct phase angle is important because the time window for the timely triggering of the pulse is only about 100 seconds.

In a first simple embodiment of the invention it can be provided that with the said phase angle before each zero crossing a corresponding short pulse is given to the switch or a contact. If a switching or disconnection of the contacts then take place, the contacts are separated from one another at the time when the contact force is very low, or at the next half-wave, and the switch is opened. This opening is then carried out in accordance with the system tuned phase angle exactly in the zero crossing of the current and thus without arc. This is a simple embodiment of the invention, in which the constructive and metrological effort is limited. It must be taken into account that very often or in the closed state of the switch at each half-wave, the pulse must be triggered. Here, it sometimes comes in operation from time to time to the creation of an arc. However, the wear is still reduced to about 10% of what is usual without the invention according to this embodiment.

Improved or made even more accurate, the method in a fundamentally alternative embodiment, characterized in that in addition still the contact force is measured, advantageously permanently detected. For then it can be provided that such a pulse does not have to be triggered permanently or too frequently or has to be applied to the switch, but only if the contact force falls below a certain contact force threshold. Such a fall below is a sure sign that the switch should switch very soon or separate the switch contact from the mating contact. So can For example, be provided that the contact force threshold between 0.01 N and 0.03 N, advantageously about 0.02 N, is. Then it is usually expected that just the contact force continues to drop and at the next aforementioned phase angle between 5 ° and 20 ° or between 10 ° and 18 ° before a zero crossing of the current of the pulse is triggered, so then exactly at the next zero crossing switching contact and mating contact are separated from each other.

The phase angle is advantageously permanently detected, particularly advantageous with a known current detection. The detection of the current or the orientation of the switching time on the current curve has the advantage over the voltage curve that then, especially when switching inductive loads with phase shift fewer problems or less spark or arc development occurs. Here, the current detection is just more accurate. Because the usually thermal drive of such a switch is relatively slow, one has sufficient time to switch from several half cycles when the contact force has dropped below a certain value from which the pulse leads to the correct switching until the time when the contact force Without the provision of the invention, the switch would switch to normal and the arc would possibly be produced.

Special account you can wear the characteristic of the arc, if always switched so that the more stable or solid or heavier contact is anodic or positive with respect to the other contact. Usually, this is the mating contact, since it is also arranged on a stronger and thus the heat dissipating carrier better. As a result, it can be taken into account that in the event of a potentially occurring arc, the temperature and thus the damage is greater where the anodic contact is. At this more solid contact, the resulting heat can be better transported away.

Usually, in a snap-action switch mentioned above, the two contacts abut one another with a force of approximately 0.4 N to 0.6 N.

In an advantageous embodiment of the invention, the pulse is relatively short and may have a duration of a few msec. This can be, for example, at least 2 msec to 4 msec, advantageously 3 msec. Longer impulses bring no advantages, but have no negative effect.

A deflection of said pulse may also be in the range of a few μητι, advantageously about 15 μητι to 50 μητι. Particularly advantageously, a pulse has a deflection of about 30 μητι. The applied impulse force can be extremely low, advantageously less than 0.5 N, which accommodates a MEMS use.

A usable in an embodiment of the invention MEMS system may also have a corresponding switching logic, which is as it were capable of learning or adaptive. Thus, it can be detected whether, in fact, at a once set phase angle, the separation of the contacts takes place without an arc. Should changes or shifts occur here in the switch or overall system, then the phase angle can be readjusted in order to avoid arcing. Furthermore, it can even be provided here that is programmed into such a control that yet in large, but recurring distances an arc is selectively generated. This has the advantage that otherwise oxidized surfaces of the contacts are cleaned over time, so that therefrom positive effect. However, a frequency of one arc after 500 to 1,000 switching operations is likely to be sufficient here.

A named MEMS component can advantageously contain all functions, ie a piezoelectric element both as an actuator for the pulse and as a sensor for measuring the contact force. Likewise, a switching logic may be included. An energy supply is easily possible through an additional contact.

According to one embodiment of the invention, it is possible that the pulse acts on a switching drive, preferably a switching arm, which carries the switching contact, possibly also acts on the switching contact itself. Then the separation of switching contact and mating contact can be promoted directly.

In an alternative embodiment of the invention, the pulse can be made on the mating contact or a device carrying the mating contact, at least as long as this is not formed too massive or heavy or stiff compared to other switching. It is possible in an advantageous embodiment of the invention that an actuator that generates the pulse, applied directly to the mating contact. In a particularly preferred embodiment of the invention, such an actuator can even bear the mating contact or form the mounting base for it.

Advantageously, the invention is used in a switch which is thermally driven or by thermal expansion elements such as bimetal elements or the like, as described for example in the aforementioned DE 102006057260 A1, is triggered.

As an actuator can be advantageously used a magnetic, thermal or piezoelectric actuator. For the sake of simplicity and because of their robust design piezo actuators are preferred. In a further embodiment of the invention according to the aforementioned second fundamental alternative, an actuator can be used simultaneously for a contact force measurement between the switching contact and the mating contact, in particular with MEMS insert. For this purpose, an aforementioned piezoelectric actuator can be used particularly well, so that thereby the constructive as well as the control effort decreases. A MEMS chip could have the complete sensor system and the actuator as well as the evaluation and control for it as well as possibly adaptive control electronics.

Can be used, the invention or a switching device according to the invention generally in switches, particularly advantageous on the one hand with switches with snap springs, which are triggered thermally or by bimetals, for example according to EP 1569257 A, and on the other also in relays, in particular magnetic relay. Even there, the switching operations can be improved.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections and subheadings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings show: Fig .1 is a schematic representation of an inventive

Device with a combined actuator and sensor on the mating contact of a switch,

Fig. 2 is a representation of the time course of current and

Contact force and off with and without the invention.

Detailed description of the embodiments

The illustrated switching device 1 1 or the switch 12 has a switching contact 15 on a switching arm 14. This switching arm 14 is fixedly mounted on the left of a Schaltarmbasis 16. However, it may be formed by a trigger 18, which is, for example, a rod in a rod regulator, as it is known for example from EP 1569257 A. Alternatively, it may be the trigger of a solenoid relay, piezo device or MEMS. It can be seen that the trigger 18 presses down on the switching arm 14 for the purpose of triggering the scarf separation process.

In the closed position of the switch 12, the switching contact 15 is located at the top befindlichem switching arm 14 to a mating contact 20. Thus, current can flow through the contact pair. The mating contact 20 is mounted or fixed on a piezo-element 22, which in turn is arranged on a mating contact base 23. The piezo-element 22 forms the above-mentioned force sensor for detecting the contact force. Furthermore, it also simultaneously forms the actuator, which gives a mechanical impulse to the switch 12. For this purpose, the piezo element 22 is briefly activated. Since it is fixed in this direction due to its storage on the stable mating contact base 23, it gives its impulse to the overlying mating contact and in turn to the applied switching contact 15 on the switching arm 14 on. The switching behavior is described with reference to FIG. 2. There, on the one hand, the current is shown with a sinusoidal profile over the phase angle. For a frequency of 50 Hz, a full wave or its phase angle of 360 ° corresponds to a time of 20 msec.

Furthermore, FIG. 2 shows the contact force with which the switching contact 15 bears against the mating contact 20. It decreases in the example shown, which advantageously does not necessarily have to be linear. It can be seen that, as shown in dashed lines, the contact force is eventually zero or less than zero and then normally the switching arm 14, which is designed as a snap-in spring initially mentioned, moves so that it separates the switch contact 15 from the mating contact 20. Since, however, the current continues to flow here, or a distance from its next zero crossing, an arc lasting for several milliseconds is produced or would arise.

As has been described, with a current detection, not shown in Fig. 1, the phase angle of the current is permanently detected. The same applies to the measurement of the contact force between the switch contact 15 and mating contact 20 by means of the piezo-element 22. This contact force is reached in the example shown at about 0.02 N when the phase angle is a total of about 420 °, ie long before the next zero crossing. If then the time is detected in which the current has a phase angle of about 13 ° before a next zero crossing, so here the contact force has fallen again slightly below 0.02 N. A controller not shown can recognize both conditions as fulfilled and causes the piezo element 22 as an actuator to deliver a short pulse. This pulse is, as shown in Fig. 1, directed so that it causes the switching contact 15 on the switching arm 14 to disconnect the contacts or to open the switch 12. This is then done with a certain inertia or delay, especially due to the mechanical inertia, after a very short Time or just so that then in the zero crossing of the current, the contacts are disconnected. There is thus no annoying arc.

As can be seen from the dashed lines, otherwise, when the contact force becomes quite zero, one would switch at a time when the current is near its maximum. Then an approximately 4 msec lasting arc would result, which would have the aforementioned harmful consequences.

The piezo-element 22 as an actuator can produce a pulse with an aforementioned deflection of about 30 μητι and a force of a little less than 0.5 N. Its duration is for example 3 msec.

Claims

claims

1. A method for switching off a switch or for disconnecting a switching contact of a mating contact, wherein the switch alternating current, characterized in that with a phase angle between 5 ° and 20 ° before a next or subsequent zero crossing of the current to a mechanical impulse the switch is given, in particular with pulse direction for separating switching contact and mating contact.

2. The method according to claim 1, characterized in that the phase angle is about 10 ° to 18 °, preferably about 13 °.

3. The method of claim 1 or 2, characterized in that without measuring the contact force, a pulse is given with a phase angle between 5 ° and 20 ° before a next zero crossing of the current to the switch.

4. The method according to claim 1 or 2, characterized in that the contact force is measured permanently and at a falling below a contact force threshold between the switch contact and mating contact of about 0.01 N to 0.03 N and the phase angle between 5 ° and 20 ° of the pulse is triggered.

5. The method according to any one of the preceding claims, characterized in that only at every other half-wave of the current with a phase angle between 5 ° and 20 ° before the next zero crossing of the current, the mechanical pulse is applied to the switch, preferably the mechanical Pulse is then applied to the switch, if the mating contact or the non-moving contact when disconnecting the contacts would be anodic with respect to the cathodic other contact.

6. The method according to any one of the preceding claims, characterized in that the pulse has a duration of a few msec, preferably about 3 msec.

7. The method according to any one of the preceding claims, characterized in that the pulse has a deflection of about 15 μητι to 50 μητι, preferably about 30 μητι.

8. The method according to any one of the preceding claims, characterized in that the pulse acts on a switching contact carrying switching drive, preferably a switching arm, or on the switching contact itself.

9. The method according to any one of claims 1 to 7, characterized in that the pulse acts on the mating contact itself, wherein preferably an actuator for the pulse is applied directly to the mating contact.

10. The method according to any one of the preceding claims, characterized in that the pulse is triggered by means of an actuator which is designed as a magnetic, thermal or piezoelectric actuator.

1 1. The method according to any one of the preceding claims, characterized in that the actuator is formed simultaneously for a contact force measurement between the switch contact and mating contact.

12. The method according to any one of the preceding claims, characterized in that the phase angle of the current is permanently detected for accurate triggering.

13. A device for carrying out the method according to any one of the preceding claims, characterized in that it comprises a switch having a switching contact and a mating contact, which are mutually movable, wherein the switch comprises an actuator for generating a pulse with pulse direction along the separating direction of switching contact and mating contact, wherein the actuator acts on the mating contact or the switching contact or a switching contact bearing switching drive.

14. The apparatus of claim 13, characterized in that the actuator is designed as a piezoelectric actuator, wherein it is preferably formed simultaneously for a contact force measurement between the switch contact and mating contact, wherein in particular the actuator with the switching contact or the mating contact forms a structural unit or the Wearing contact or the mating contact carries.

15. The apparatus of claim 13 or 14, characterized in that the mating contact is relatively fixed or rigidly arranged on the switch and the switching contact is carried by a switching drive or switching arm, wherein a triggering device, preferably a thermal tripping device, rests on the switching drive ,