EP1417694B1 - Electromagnet arrangement for a switch - Google Patents

Abstract

An electromagnet system for a switch includes a main magnetic circuit including a magnet yoke and a magnet armature mechanically linked to a contact apparatus. At least one permanent magnet is disposed in the main magnetic circuit for generating a holding force for the magnet armature. A shunt circuit is provided parallel with the main magnetic circuit so that the permanent magnet is a magnetic energy source for the shunt circuit. The shunt circuit includes pole legs and a yoke arc of the magnet yoke. The magnet armature is capable of contacting the pole legs so as to close the shunt circuit. An excitation winding is provided for each of the pole legs for to generating a pull-in force for the magnet armature. The electromagnet system is magnetically dimensioned such that a minimum magnetomotive force of the excitation windings is sufficient for opening the electromagnet system.

Description

The invention relates to an electromagnet arrangement for a switch, in particular for a contactor, according to the preamble of the first claim.

The electrical and magnetic dimensioning of electromagnetic contactors is usually designed so that in the armature holding state, a low electrical power is applied (for example, DE 195 26 038 A1). This is already indicated because devices of this type are in the hold state for the longer period of operation. The energy consumption in the hold state has the disadvantage that the device heats up. Typically, one counts on power losses in the hold state of a few watts. For vacuum switching devices, significantly higher outputs must be provided. In view of the fact that contactors or switches are combined in large numbers in a control cabinet, there is a need to take active measures for heat dissipation.

The use of electronics has not brought any satisfactory improvement. Thus, known electronic solutions for electromagnet arrangements are to control the power requirement by pulse width modulation. As a result of this technique, as the power is reduced, ever narrower pulses must be generated in the circuit. With the narrowing of the pulses occur increasingly harmonics that pose problems in the electromagnetic shielding and compatibility.

A magnet arrangement with circuit arrangement for generating pulse sequences for regulating the power is shown, for example, in DE 39 10 810 A1 or in DE 195 26 038 A1.

There is known a magnet arrangement (US Pat. No. 4,020,433), in which a release device for the opening process of the magnetic circuit is described. The release device is designed such that a small current to flow through the excitation coils is sufficient to initiate the opening process.

It is the object of the invention to provide an electromagnet arrangement which is optimized for the holding operation.

The solution is reflected in the features of the main claim. Further developments can be found in the subclaims.

• ein aus einem, vorzugsweise U-förmigem Magnetjoch und einem Magnetanker gebildeten Hauptmagnetkreis,
• einem in Wirkverbindung mit dem Magnetanker stehenden Kontaktapparat des Schalters, und einen mit einer Rückstelleinrichtung beaufschlagten, vorzugsweise federbelasteten Magnetanker,
• mindestens einem im Hauptmagnetkreis angeordneten Permanentmagneten für die Erzeugung der Haltekraft für den Magnetanker und
• mindestens eine an mindestens einem Polschenkel, also am Magnetjoch angeordnete Erregerwicklung für die Erzeugung der Anzugskraft für den vom Magnetjoch getrennten Magnetanker. Die Elektromagnetanordnung wird elektronisch von einer zugehörigen Schaltungsanordnung angesteuert.

The magnet arrangement is based on the following structure:

• a main magnetic circuit formed of a preferably U-shaped magnetic yoke and a magnet armature,
• a contact device of the switch, which is in operative connection with the magnet armature, and a preferably spring-loaded magnet armature which is acted upon by a return device,
• at least one arranged in the main magnetic circuit permanent magnets for the generation of the holding force for the armature and
• at least one arranged on at least one pole leg, so the magnetic yoke excitation winding for the generation of the attractive force for the magnetic armature separated from the magnet yoke. The electromagnet arrangement is controlled electronically by an associated circuit arrangement.

The essence of the invention is that a bypass circuit is formed parallel to the main magnetic circuit, which is also closable via the magnet armature and the bypass circuit consists of the two pole legs and a second polflächenabgewandt arranged on the magnetic yoke yoke, which is interrupted by a remanence air gap.
Further advantageous embodiments are in the following:

The magnet arrangement (the magnetic yoke, the second yoke arc and the permanent magnet) is magnetically dimensioned so that the holding power - attracted to the magnet armature state - is applied solely by the permanent magnet without energizing the exciter winding.

The permanent magnet generates a first magnetic flux (MK1) through the pole legs and the armature and a second flux (MK2) through the second through the remanence flux splits. The absolute value of both power flows is given by the state of charge of the permanent magnet. The ratio of the power flows is determined by the sizing of the bypass circuit (including remanent air gap) and the distance of the armature. The first magnetic flux (MK1) ensures that the magnet armature is held firmly on the pole faces. This armature holding force acts on the spring force contrary, which opens the magnet assembly in the absence or reduced magnetic force. In this case, the armature moves against stops, not shown. The excess of the armature holding force, generated by the magnetic flux through the armature against the spring force is a measure of the susceptibility of the magnet assembly to external mechanical influences. To open the magnet assembly should be sufficient minimum flooding (smallest current through the excitation coils depending on the number of turns), whereby the first magnetic flux is weakened so far that the spring force is sufficient to lift the armature. With the said small excitation current, a magnetic flux is generated, which is opposite to the magnetic flux through the armature and the virtually lossless urges the first magnetic flux in the bypass circuit substantially.

To close the magnet arrangement, a quite large excitation current is used, which is sufficient in the maximum stroke of the magnet armature to overcome the spring force. As the magnet armature approaches the pole faces, the magnetic fluxes between the main and tributary circuits shift with the same magnetic energy.

The magnetic yoke is U-shaped and consists of two L-shaped halves with a longer pole leg and a shorter transverse leg, wherein each pole leg faces the contact surfaces of the magnet armature.

The permanent magnet is clamped in the middle between the transverse legs, whereby no welding is made. The second zygomatic arch is arranged parallel to the transverse legs.

The remanence air gap, whose width is on the order of 0.3 mm, may be air-filled or filled with a non-magnetic material.

The excitation winding of the magnet arrangement is connected to an energy store whose energy content is sufficient to release the magnet armature from the holding state. The energy store may be a storage capacitor or an inductor.

Preferably, the circuit arrangement is associated with a monitoring unit for controlling the voltage state of the energy store, so that the arrangement can be switched to another source of energy.

The advantage of the invention is that a circuit arrangement (preferably with pulse width modulation) for driving the exciter winding and for supplying the electrical energy for the excitation winding can be operated practically in 'stand-by mode'.

The EMC measures can be reduced because in the hold state, only the electrical energy for the idle power of the circuit must be provided. In comparable magnet arrangements is clocked in the hold state, whereby interference fields are unavoidable. The breaking capacity is minimal. The holding power is low and corresponds to the standby power of the control electronics. The design of the electronics is only determined by self-consumption. The magnetic circuit is energetically designed only for the situation 'magnet armature closing'. Preferably, the turn-off energy should be saved in the phase of the tightening process, for example by charging a capacitor during the tightening process.

The permanent magnet consists - as usual in comparable arrangements - of magnetically hard material, such as AlNico, which also Seitenerd connections are possible.

The advantage of the magnet arrangement is in particular that a small space requirement for the excitation coil is necessary, whereby a compact structure can be achieved.

The invention can also be used wherever the movement of the armature can be implemented in the form of a linear drive.

Figur 1:

die Magnetanordnung mit angezogenem Magnetanker,

Figur 2:

die Magnetanordnung mit abgehobenem Magnetanker und

Figur 3:

die Magnetanordnung als Zusammenbauzeichnung.

Further details and advantages of the invention will become apparent from the following, explained with reference to figures embodiment. Show it

FIG. 1:

the magnet arrangement with the armature attracted,

FIG. 2:

the magnet assembly with lifted magnet armature and

FIG. 3:

the magnet arrangement as an assembly drawing.

The magnetic yoke 10 has a U-shape and consists of two - with respect to the vertical axis of symmetry SA - symmetrical halves (in L-shape) with longer pole legs 11 and short transverse legs 12. The transverse legs are arranged against each other. Between the transverse legs, a permanent magnet 20 is supported. For this purpose, the ends of the transverse legs are formed with lugs 19, between which the permanent magnet is clamped during assembly. Contrary, comparable magnetic structures in which elaborate laser welding connections are made, this is an elegantly simple structure. 3 shows the assembly drawing, from which it can be seen that the magnet arrangement consists of laminated cores and are riveted on cover plates 80, resulting in the mechanical cohesion.

The magnet armature 60 consists of a plate-shaped body with laterally appended extensions 61. On the armature, which should preferably be linearly movable, a restoring force by at least one (not shown) spring (36) generated. The armature has an air gap or hub 18. An operative connection of the armature with a contactor of the switch or contactor is present, but not shown.

The magnetic yoke is formed in the usual form as a laminated core. Laterally, the transverse legs 12 opposite, mounting legs 41 are each arranged with a bore to which the magnet assembly can be mounted in a housing.

The first magnetic flux circuit MK1 is associated with a magnetic bypass circuit MK2, this is the pole yoke (11,12) available polflächenabgewandt. The bypass circuit is formed by two, parallel to the short transverse legs 12 second Jochbogenschenkel 24 (parallel leg). Transverse leg and Jochbogenschenkel are offset from each other by a groove, but otherwise they are a physical part of the magnetic yoke.

The pole legs 11 are each comprised of bobbins with exciter windings 30, 32. The magnetic flux that can be generated by the exciter windings 30, 32 overlaps in the air gap with the magnetic flux of the permanent magnet 20. During the tightening process, the two magnetic fluxes subtract in the bypass circuit.

The Jochbogenschenkel 24 each have a smaller cross section compared to the first transverse legs 12 and the armature

Functionally, however, during the tightening process, the highest magnetic flux density in the armature.

The Jochbogenschenkel are separated by a Remanenzluftspalt 25. The width of the remanence air gap is approx. 0.3 mm. With the cross sections of the Jochbogenschenkel and the width of the Remanenzluftspalts the ratios of the magnetic fluxes MK1 and MK2 are defined to each other.

Due to its magnetic energy, the permanent magnet generates a magnetic flux which is divided into the two magnetic flux circuits MK1 and MK2. The design of the magnet arrangement, in particular the strength of the permanent magnet is chosen so that in the holding state (magnet attracted, without applying the electrical excitation through the coils 30,32) of the armature is held securely on the yoke for all operating conditions.

This magnetic dimensioning ensures that in the holding position no magnetic energy must be supplied by the excitation coils; the holding force for the armature is applied solely by the permanent magnet. Thus, it is preferably achieved that the electrical power of an associated electronic circuit can be minimized, since essentially only the provision of the tripping energy has to be ensured. The low tripping energy can, for example, be provided sufficiently via a suitably dimensioned storage capacitor or an inductance whose energy content can also be monitored by the electronic circuit.

To move the armature from the holding position in the open position (which means, for example, the OFF position of a switch), it requires only a small amount of energy. This is supplied by the control electronics to the excitation windings 30, 32 whose magnetic flux weaken the flux defined by the pole faces so far that the holding force is overcome.

The flow changes accordingly and the main part of the magnetic energy is forced into the bypass circuit (yoke arc limb 24, remanence air gap 25). To switch off a storage capacitor can be used, as this an output of max. 1 Watt is sufficient. Such a capacitor has no appreciable power loss, so that in the electrical drive circuitry alone in the hold state an idle power in the order of much less than 1 watts must be provided.

The drive of the magnet assembly (closing the armature, drive excitation) is generated by a powerful coil current (for example, 100 msec with a power of 100 watts), which generates a magnetic flux opposite to that of the permanent magnet in the pole legs and also the spring force on the armature overcomes. As the magnet armature approaches the pole faces, the magnetic field in the magnetic circuit MK1 compresses. The magnetic bypass circuit MK2 contains only low magnetic energy.

After contact of the magnet armature with the pole faces (closing), the exciting current can be switched off, since - as shown - the holding force is done statically.

Claims (9)

1. Electromagnet arrangement for a switch, in particular for a contactor, comprising
   a main magnet circuit (MK1) formed by a magnet yoke (10) and a magnet armature (60) acted upon by a resetting means (36),
   a contact apparatus of the switch actively connected with the magnet armature (60),
   at least one permanent magnet (20) disposed in the main magnet circuit (MK1) for generating the holding force for the magnet armature (60),
   wherein a shunt circuit (MK2) is configured parallel to the main magnet circuit (MK1) and can also be closed via the magnet armature (60),
   wherein the shunt circuit (MK2) consists of two pole legs (11) and a yoke arc (24) is arranged on the magnet yoke (10) remote from the pole faces and is interrupted by a remanence air gap (25),
   a circuit arrangement configured to be operated in stand-by mode when the magnet armature contacts the pole legs for electronically activating the electromagnet arrangement,
   at least one exciting winding (30, 32) associated with a pole leg (11),
   wherein the attraction force for the magnet armature (60) separated from the magnet yoke (10) is generated by a magnetomotive force of the exciting winding(s) (30, 32), and
   the exciting winding(s) (30, 32) of the magnet arrangement are connected to at least one energy storage means, the energy content thereof being sufficient to release the magnet armature (60) from the held state,
   characterised in that a monitoring unit is associated with the circuit arrangement and monitors an energy content, sufficient for opening the magnet arrangement, of the at least one energy source so that in the case of an insufficient energy content there is a change-over to a second energy storage means.
2. Magnet arrangement according to claim 1, characterised in that the pole legs (11) forming the magnet yoke (10) are connected to one another via cover sheets (80).
3. Magnet arrangement according to any one of the preceding claims, characterised in that the magnet yoke (10) is U-shaped and consists of two L-shaped halves having a longer pole leg (11) and a shorter cross leg (12), in each case a pole leg (11) facing the contact surfaces of the magnet armature (60).
4. Magnet arrangement according to any one of the preceding claims, characterised in that the permanent magnet (20) is centrally disposed between the cross legs (12) and is held by clamping.
5. Magnet arrangement according to any one of the preceding claims, characterised in that the second yoke arc (24) is disposed parallel to the cross legs (12).
6. Magnet arrangement according to any one of the preceding claims, characterised in that the magnet arrangement is constructed as a magnet sheet system.
7. Magnet arrangement according to any one of the preceding claims, characterised in that the remanence air gap (25) is filled with a non-magnetic material.
8. Magnet arrangement according to any one of the preceding claims, characterised in that the permanent magnet (20) is clamped between the cross legs (12).
9. Magnet arrangement according to any one of the preceding claims, characterised in that the energy storage means is a storage capacitor or an inductor.

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