Electromagnetic switching device

A drive solenoid, a yoke, an armature and at least one contact are mounted in a housing of an electromagnetic switching device. The drive solenoid, yoke and armature are inductively intercoupled, in such a way that when an inrush current is applied to the drive solenoid, the armature can be displaced into a pickup position, thus directly or indirectly actuating the contact. The yoke and/or armature contain(s) pulverulent magnetic material.

This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP2004/006183 which has an International filing date of Jun. 8, 2004, which designated the United States of America and which claims priority on German Patent Application number DE 103 31 339.7 filed Jul. 10, 2003, the entire contents of which are hereby incorporated herein by reference.

FIELD

The present invention generally relates to an electromagnetic switching device. For example, it may relate to a contactor or a power circuit breaker, with a housing, a drive solenoid, a yoke, an armature and at least one contact,the drive solenoid, the yoke, the armature and the at least one contact being mounted in the housing,the drive solenoid, the yoke and the armature being inductively intercoupled, so that, when an inrush current is applied to the drive solenoid, the armature can be displaced into a pickup position,the displacement of the armature into the pickup position allowing the contact to be directly or indirectly actuated,the yoke containing pulverulent magnetic material.

BACKGROUND

Electromagnetic switching devices are known. By way of example, reference is made to EP-A-0 505 194.

Electromagnetic switching devices such as power circuit breakers and contactors contain magnetic drives which include a solenoid, a yoke and an armature. The yoke and the armature in this case consist of magnetizable material, for example iron sheets. If an inrush current is applied to the solenoid, a magnetic flux is produced in the yoke, exerts a force on the armature and picks it up. The armature is consequently displaced into a pickup position.

In the case of a contactor, the displacement of the armature has the effect that switching contacts connected to the armature are moved, and consequently main electrical contacts of the switching device are closed. Once application of the inrush current to the drive solenoid is completed, the armature is moved back into a starting position by restoring springs and, as a result, the contacts are opened.

In the case of power circuit breakers, magnetic trips in which a current to be monitored flows through the drive solenoid are used. If this current exceeds a predetermined value (that is to say the inrush current), the armature is displaced and, as a result, the breaker latching mechanism is actuated, which in turn brings about the opening of the contact.

In the prior art, the yoke and the armature include laminated cores which are produced from individual iron sheets that are connected to one another—for example by rivets. The production from individual metal sheets that are insulated from one another is necessary in this case in particular for the avoidance of eddy currents and associated eddy current losses.

In the prior art, it is disadvantageous in particular that, as a result of the sheeting, only limited degrees of freedom of form are possible and that the sheets can only be connected to the housing and actuating elements by appropriate fastening elements. The solenoid also has to be connected to the housing or the yoke by a separate insulating frame. Furthermore, in the prior art, the striking together of the yoke and armature has the effect of restricting the service life of the magnetic system.

It would be desirable for the yoke and the armature to be able to have any desired three-dimensional structures, which would make it possible for the magnetic circuits to be optimally configured. It should also be possible for the yoke, the drive solenoid and the housing to be connected to one another in a simple and low-cost way, in particular without additional fastening elements. Furthermore, there should be good thermal coupling, to allow any heat loss occurring to be dissipated and so-called hot spots to be avoided. Furthermore, the service life of the magnetic system should be just as long as the mechanical service life of the switching device.

SUMMARY

An object of at least one embodiment of the present invention is to develop an electromagnetic switching device in such a way that it may include, for example, at least one of these advantages.

The yoke and the drive solenoid are cast with each other by way of a permanently elastic casting compound to form a block. This is because that makes possible a simple, stable, durable and in particular low-cost connection of the yoke to the drive solenoid.

The pulverulent magnetic material may be, for example, a sintered material. Alternatively, it is possible for the pulverulent magnetic material to be mixed with a polymer compound, for example epoxy resin.

If the pulverulent magnetic material surrounds a soft iron core, a highly permeable material and/or a permanent magnet, a specifically directed flux guidance and/or bistable switching behavior can be achieved.

If a sensor which is inductively coupled to a conductor connected to the contact by way of a coupling element containing a pulverulent magnetic material is arranged in the housing, a sensor signal representative of the actual flow of current through the conductor can be determined in a simple way. The sensor may alternatively be formed as a magnetic field sensor or as a flux-change sensor.

If the sensor and the coupling element are cast with each other, the connection of the sensor to the coupling element is particularly durable and stable.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

According toFIG. 1, a contactor, as the example of an electromagnetic switching device, has a drive solenoid1. The drive solenoid1is inductively coupled to a yoke2and an armature3. If an inrush current I is applied to the drive solenoid1, the armature3is displaced into a pickup position, as indicated inFIG. 1by an arrow A. One result of this is that the contact4is actuated, to be precise is closed. Therefore, an electrical connection is established between conductors5connected to the contact4.

The drive solenoid1, the yoke2, the armature3and the contact4as well as the conductors5are mounted in a lower housing part6. The lower housing part6is detachably connected to an upper housing part7by way of fastening elements8, which are only schematically represented inFIG. 1. The lower housing part6and the upper housing part7together form a housing6+7of the electromagnetic switching device.

The construction described above for a contactor also applies in principle to the switching device formed as a power circuit breaker. The only difference is that, in the case of a power circuit breaker, the drive solenoid1is flowed through by a current to be monitored and the displacement of the armature3does not have the effect that a contact4is directly closed, but opened indirectly by actuation of a breaker latching mechanism. In this case, the electrical connection between the conductors5is therefore interrupted by the displacement of the armature3.

The construction of the electromagnetic switching device fromFIG. 1is now explained in more detail below in conjunction with the sequence ofFIGS. 2 to 5.

Firstly, the yoke2is produced in advance—seeFIG. 2. It consists of pulverulent magnetic material9or contains such material9. The pulverulent magnetic material9may be, for example, sintered material. The pulverulent magnetic material9may, however, also be a metallic powder which is mixed with a polymer compound, for example epoxy resin. As represented inFIG. 2, the yoke2may contain further elements10,11. For example, the yoke2may contain a permanent magnet10. In this way it is possible, for example, to achieve a bistable switching behavior of the switching device. However, the yoke2may also contain a soft iron core11or some other highly permeable material. In this case, a specifically directed flux guidance of the magnetic field in the yoke2is obtained. The elements10,11are surrounded at least on two sides, preferably at least on four sides, possibly even on all sides, by the pulverulent magnetic material9.

After producing the yoke2, the drive solenoid1is loosely applied to the yoke—seeFIG. 3. The drive solenoid1and the yoke2are then cast with each other—see FIG.4—by means of a permanently elastic casting compound12. The block of casting compound12is finally cast—see FIG.5—with a hard casting material13. The hard casting material13thereby forms at least part of the lower housing part6.

The casting with the hard casting material13has the effect of producing at the same time an intimate bond between the lower housing part6, the yoke2and the drive solenoid1by means of the permanently elastic casting compound12. The drive solenoid1, the yoke2and the lower housing part6are consequently cast with one another in a unitary manner by way of the casting compound12.

As can be seen fromFIG. 5, the fastening elements8for connecting the lower housing part6to the upper housing part7are arranged on the lower housing part6in the casting material13. Further fastening elements14are arranged in the casting material13. By way of these fastening elements14, the lower housing part6can be connected to a fastening surface15, which is only schematically indicated inFIG. 5.

The production of the yoke2using the pulverulent magnetic material9and the lower housing part6of the hard casting material13has been described above. However, the above statements concerning the yoke2and the lower housing part6can be applied in an entirely analogous way to the production of the armature3and the upper housing part7.

FIG. 6then shows an extension of the switching device ofFIGS. 1 to 5. According toFIG. 6, a sensor16is arranged in housing6+7. The sensor16is inductively coupled to one of the conductors5by way of a coupling element17. By analogy with the yoke2and the armature3, the coupling element17contains pulverulent magnetic material9or preferably even consists of such material. By way of the sensor16, consequently a sensor signal that is representative of the current flow through the conductor5can be directly sensed.

As indicated inFIG. 6, the sensor15may be formed for example as a solenoid16. In this case, the sensor16may be a flux-change sensor. It can therefore only be used in the case of alternating voltages or for detecting a switching operation. The sensor16may, however, also be formed as a magnetic field sensor, for example as a Hall sensor. In this case, the magnetic field as such, and consequently the current flow in the conductor5, can be sensed by way of the sensor16.

By analogy with the casting of the yoke2with the drive solenoid1, the sensor16is preferably also cast with the coupling element17, as schematically indicated inFIG. 6.

Consequently, entirely novel structures for the yoke2and the armature3, even for the entire electromagnetic switching device, can be realized in a simple way by way of the switching device according to at least one embodiment of the invention.