WO1997015061A1

WO1997015061A1 - Electromagnetic operating device

Info

Publication number: WO1997015061A1
Application number: PCT/SE1996/001341
Authority: WO
Inventors: Assad Abri; Robert Nordgren
Original assignee: Asea Brown Boveri Ab
Priority date: 1995-10-20
Filing date: 1996-10-21
Publication date: 1997-04-24
Also published as: SE9503688L; SE9503688D0; EP0876672A1

Abstract

An electromagnetic operating device with at least one operating unit. Each operating unit comprises one fixed and one movable magnet part. The fixed magnet part comprises a first magnetic pole (8) and a second magnetic pole (7). A first operating coil (11) is fixed to the first magnetic pole (8) and a second operating coil (10) is fixed to the second magnetic pole (7). The movable magnet part comprises an armature (2) which is adapted to be displaced along a circular path towards the first magnetic pole (8) by activation of the first operating coil (11) and towards the second magnetic pole (7) by activation of the second operating coil (10). The fixed magnet parts are integrated into a common iron core (20) and the movable magnet parts are fixed to a common rotary device (1), from which the movement is obtained.

Description

Electromagnetic operating device

TECHNICAL FIELD

The present invention relates to an operating device of the kind described in the preamble to claim 1 for operation of, for example, an electric switching device for medium or high voltage. An operating device of the kind described is designed to achieve, within a small volume, a very fast movement in two directions, generated with great force. The movement is utilized for operating, for example, a contact system associated with a circuit breaker.

BACKGROUND ART

For operation of medium-voltage or high-voltage circuit breakers, spring-operated devices and hydraulically and pneumatically operated devices are usually used. Such -operating devices normally comprise a large number of different parts, which entails a relatively high manufactu¬ ring cost. These operating devices are often bulky and require regular supervision and control.

Electromagnetic operating devices are primarily used in low- voltage circuit breakers. In small circuit breakers of such kind it is common for the attractive force of the electro¬ magnet to be combined with the force of a return spring, such that the movable contact system, upon breaking of the operating current, can be displaced in the opposite direction (breaking) . One problem with such an operating device is that the electromagnetic force to be able to perform an active movement (making) must overcome the return force exerted by the spring.

Electromagnetic operating device have also been used in older high-voltage circuit breakers of the type where the contact system is enclosed in a grounded oil-filled tank. In a known operating device of this kind, two separate opera¬ ting magnets are used for opening and closing, respectively. The magnets are connected to the contact system via a mechanism, composed of a plurality of arms, links and rods, which, by its relatively large weight and friction in all the rotary bearings of the mechanism, is slow in operation and energy demanding.

From US 3,900,822, a proportional, double-acting electro¬ magnet is previously known. It comprises a fixed circular magnet part with two operating coils and a movable magnet part with a coaxially displaceable armature. The fixed magnet part comprises a tubular magnetic core which is common to both coils and to which the sleeve-formed opera¬ ting coils are fixed, and a magnetic core which is applied at each end and which has the shape of a hollow frustum of a cone. The conical magnetic core forms a cylindrical space in which the armature can move and exhibits an annular air gap towards the circular magnetic core. By activating the magnet coils with different voltages, the common armature can be caused to move back and forth along a path coinciding with the axis of the fixed magnet part. The known electromagnet operates with a constant air gap, whereby the tendency of the armature to assume a position, where the magnetic flux lines across the armature are equal on both sides of the activated operating coil, is utilized. As far as produced force is concerned, the magnetic effect thus utilized cannot compare with a design where the magnetic field is oriented parallel to the direction of movement of the armature. A further problem with the known design is that, in case of a translatory movement, the entire mass of the armature must be accelerated, which entails a great inertial resistance.

SUMMARY OF THE INVENTION

The object of the present invention is to achieve an electromagnetic operating device of the kind stated in the preamble to claim 1, which is simpler, more reliable, lighter and less bulky than comparable known designs. In addition, the operating device is to be so designed that the energy losses due to friction etc. in the transmission between the armature and the operating system are minimized, and that higher operating acceleration and operating speed can be achieved. It shall also exert great force, in two directions, against the operating system during the whole movement. This is achieved according to the invention with an operating device which has the characteristic features stated in the characterizing part of claim 1. Advantageous embodiments are described in the characteristic features of the subsequent dependent claims.

According to the invention a rotary device comprising a number of rotationally symmetrically disposed iron armatures is arranged in an outer stationary iron core. To achieve a rotary movement, a pair of operating coils is arranged and fixed to the iron core at each armature. The rotary device may then rotate between two end positions where the magnetic pole surfaces of the armature make contact with that of the iron core. Between the pole surfaces air gaps arise, which - decrease during the movement in the active direction of movement. During the whole movement, the air gap is surrounded by the respective operating coil. During the rotary movement, an arm projecting at the armature will move into the operating coil, whereby the air gap decreases until the armature makes contact with the iron core.

The design of the operating device permits a large portion of the magnetic material to be utilized for achieving movement in both directions. During movement in each direc¬ tion of movement, the parts of the magnetic core and the armature, which are thus commonly utilized, return the magnetic field created by the activated coil in an external iron loop. In this way, the resistance to the magnetic flux is reduced. The magnetic flux through the coil thus increases and greater force can be achieved. The doubly utilized magnetic material thus results in a more slender design of an armature which, with a smaller mass, gives the same force as a conventionally designed armature. The smaller mass of the armature thus entails a faster movement process.

BAD ORIGINAL # By arranging the operating coil so as to surround the air gap between the poles of the armature and the iron core, an advantageous concentration of the magnetic flux is obtained. The magnetic field is thus oriented parallel to the arma- ture. The fixed poles are integrated with a common surround¬ ing iron core, which results in advantages such as improved mechanical stability, fewer parts, and a greater concentra¬ tion of the magnetic flux. The magnetic field outside a coil is thus returned in an external iron loop in the surrounding iron core such that the flux through the coil is further reinforced. The legs of the iron core can thus be designed more slender without deteriorating the concentration of the flux. In is way, a very fast and powerful movement can be achieved since the armature, by activation of an operating coil, is caused to be displaced towards the respective pole.

During a translatory movement of a body, the acceleration and hence the time of action for movement from one point to - another are determined by the mass of the body. During a rotary movement of a body, the time of action for a rotation from one position to another is determined by the moment of inertia of the body. The moment of inertia is dependent on the sub-masses included in the rotation and their distance from the centre of rotation. During a rotary movement, the moment of inertia can therefore be limited by reducing the masses included and bringing them closer to the centre. The operating device according to the invention is therefore, to create greater force and shorter time of reaction, adapted to influence (transfer the force to) the operating εystem by means of a rotary movement.

An operating device according to the present invention is preferably suited for single- or multi-pole operation of SF6 gas-insulated high-voltage circuit breakers. Through its compact design, the operating device can be advantageously integrated into the respective breaker pole to form a herme¬ tically closed, insulating gas-filled unit, where all the mechanical operations take place inside the unit. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail with reference to the accompanying drawings, wherein

Figure 1 shows a sketch of the principle of operation of an operating device according to the invention,

Figure 2 shows a cross section through an operating device with a rotary device with several armatures,

Figure 3 shows a view of and a cross section through an operating device with a rotary device with several armatures where, according to an advantageous embodiment, the rotary device is journalled axially displaced in relation to the iron core, and

- Figure 4 shows a view of and a cross section through an operating device with a rotary device with several armatures where, according to an advantageous embodiment, the armatures are placed closer to the centre.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An operating device according to the invention with one fixed magnet part and one movable magnet part is shown in Figure 1. The operating device is symmetrical around a vertical plane through the centre of the device. The movable magnet part comprises a rotary device 1 with a first arma¬ ture 2. The fixed magnet part comprises an upper magnetic core 3 and a lower magnetic core 4, between which the rotary- device is rotatable around an axis A perpendicular to the plane of the paper. A leg 12 projecting from the upper iron core 3 and a leg 13 projecting from the lower iron core 4 thus form a bearing for the rotary device 1. The operating device is shown in a position where the rotary device is rotated to a maximum in the counterclockwise direction. The first armature 2 has a magnetic counterclockwise pole 5, which makes contact with a magnetic first pole 7 arranged in the lower iron core 4. In the clockwise direction, the first armature 2 has a magnetic clockwise pole 6, which in the position shown is at a distance from a magnetic second pole 8 arranged in the upper iron core 3. Between the clockwise pole 6 of the armature and the second pole 8 of the upper iron core, there is an air gap 9. In a corresponding way, the rotary device has a second armature 2 ^■ with a magnetic counterclockwise pole 5' and a magnetic clockwise pole 6 which in a corresponding way make contact with, and form an air gap 9' with, respectively, a magnetic first pole 7' arranged in the upper iron core 3 and a magnetic second pole 8' arranged in the lower iron core 4, respectively.

For rotating the first armature in the counterclockwise direction, a first counterclockwise coil 10 is arranged fixed to the lower iron core 4 and surrounding the first pole 7, into which coil 10 the counterclockwise pole 5 of the first armature 2 may penetrate. In a corresponding way, a second counterclockwise coil 10' is arranged fixed to the upper iron core 3 and surrounding the first pole 7', into which coil 10' the counterclockwise pole 5' of the second armature 2" may penetrate. For rotation of the first arma- ture 2 in the clockwise direction, a first clockwise coil 11 is arranged at the upper iron core 3 and surrounding the second pole 8, into which coil 11 the clockwise pole 6 of the first armature 2 may penetrate. In a corresponding way, a second clockwise coil 11' is arranged fixed to the lower iron core 4 and surrounding the second pole 8 into which coil 11' the clockwise pole 6' of the second armature 2' may penetrate. For transferring the rotary movement into a translatory movement, the rotary device is provided with a crank 25.

To achieve a rotation in the clockwise direction, a circuit is connected to the first clockwise coil 11, which results in the creation of a magnetic field through the coil with a magnetic flux parallel to the axis of the coil. Between the clockwise pole 6 of the armature 2 and the second pole 8 of the upper iron core, a magnetic attractive force thus arises which strives to bring the two poles together.

The magnetic flux through the coil is reinforced by retur¬ ning the magnetic field outside the coil in an external loop via the lefthand half of the upper iron core 3, the projec¬ ting leg 12 of the upper iron core, the rotary device 1 and back into the first armature 2. In the same way, for the righthand part of the operating device, upon a simultaneous activation of the second clockwise coil 11', an attractive force arises between the clockwise pole 6' of the second armature 2' and the second pole 8' of the lower iron core. Also this attractive force is reinforced when the magnetic flux increases by returning the magnetic flux outside the coil back in a closed iron loop formed in a similar manner.

A counterclockwise rotation is achieved in a corresponding way by activation of the counterclockwise coils 10 and 10' . A magnetic flux thus arises between the counterclockwise poles 5, 5' of the armature 2 and the first poles 7, 7' of the iron cores. The magnetic flux is reinforced in the manner described above by returning the magnetic field lines in external iron loops. The reinforced magnetic flux thus tends to bring together, with great force, the counter¬ clockwise poles 5, 5" of the respective armature with the second poles 7, 7' of the respective iron core.

Figure 2 shows, according to the invention, an advantageous embodiment of an operating device, which is symmetrical in a vertical and a horizontal plane through the centre of the figure. Four armatures 2, 2', 2' 2' ' ^• are fixed to a rotary device, each armature having a clockwise pole 6 and a counterclockwise pole 5. A common iron core 20 is arranged surrounding all the armatures and comprising four legs 21, 22, 23 and 24 projecting towards the centre and four core portions 25, 25', 25" and 25 ' ' ' making contact with the respective armature with a minimum air gap. Each one of the respective legs comprises in the inner end a foot 26, 27, 28

BAD ORIGINAL and 29, which with minimum air gaps make contact with the rotary device 1. The iron core 20 comprises for each arma¬ ture 2 a first pole 7 with a counterclockwise coil 10 fixed to the iron core and a second pole 8 with a clockwise coil 11 fixed to the iron core.

When activating, for example, the clockwise coil 11, a magnetic field is created in the coil in parallel with the axis of the coil, the flux of the magnetic field being reinforced in the manner described above via an external magnetic field closed by an internal iron core. Thus, a closed magnetic field is created by leading the magnetic field from the clockwise pole 6 of the armature via the armature 2, the rotary device 1, the foot 26 back to the second pole 8 of the iron core. In the embodiment described, an external magnetic field closed by an external iron loop is also generated, which magnetic field reinforces the magnetic flux in the coil. Thus, a magnetic field is led - also from the clockwise pole 6 of the armature over to the iron portion 25, in the iron core 20 around the outside of the operating coil 11 to the leg 21 and back to the second pole 8. In this way, the force-generating magnetic flux is concentrated, with two external magnetic fields, between the clockwise pole 6 of the armature and the second pole 8 of the iron core, such that a very strong rotary movement can be obtained from the rotary device.

An advantageous embodiment of the operating device according to the invention is shown in Figure 3. The armatures 2, 2', 2" and 2' ' ' are here fixed to a rotary device 1, which, axially displaced, is journalled in the centre of the device. An internal iron core 30 integrated into the exter¬ nal iron core 20 is shaped with legs 31, 31', 31" and 31' ' ' projecting towards each armature 2, which legs form opposite poles to the core portions 25, 25 25" and 25' ' ' of the external core. Each armature 2 is operated with one counter¬ clockwise coil 10 and one clockwise coil 11. The magnetic field, which according to the above is led back in the armature and the rotary device, is here returned in the inner core 30 and its projecting legs 31. In this embodi¬ ment, the rotary device need not be made of magnetic mate¬ rial but only of a material which withstands the mechanical stresses. In this way, the moment of inertia is reduced in that the movable masses are reduced. The reduced moment of inertia results in a faster movement corresponding to the same force, which entails a shorter time of reaction.

Still another advantageous embodiment of the operating device according to the invention is shown in Figure 4. In the same way as described above regarding the device descri¬ bed in Figure 3, the armatures 2, 2', 2" and 2' ' ' are fixed to a rotary device 1, which, axially displaced, is journalled in the centre of the device. Each armature 2 is operated with a counterclockwise coil 10 and a clockwise coil 11. In the embodiment shown, the inner core is comple¬ tely excluded. This permits the armatures to be brought closer to the centre, whereby the moment of inertia is reduced. The absence of the inner core means that the main part of the magnetic flux has to be returned via the outer iron core 20 only. In order not to create a less concentra¬ ted magnetic flux through the operating coils, the outer iron core has been made thicker. However, a possible dis¬ advantage of a less concentrated magnetic flux through the operating coil is counterbalanced by the fact that the moment of inertia becomes smaller and that the coils can be made simpler and be provided with a stronger winding.

Although the design of the air gap can be arranged in a plurality of ways, it has proved that a design where the surfaces of the magnetic poles are oriented radially to the centre of the rotation is preferable. In this way, the con¬ centrating forces are directed in a direction tangential with the movement and thus create no transverse forces. By a radial orientation of the pole surfaces, also a maximum concentration of the magnetic flux lines across the air gap is obtained. In order completely to surround the air gap, the coils are wound on frames, the ends of which are orien¬ ted in a radial direction. The common iron core 20 comprising the legs 16, 17, 18 and 19 are shown in one piece in the figures. In an advantageous embodiment, however, the iron core is composed of a plura¬ lity of parts, which are fixed to each other like pieces of a jig-saw puzzle. In such an embodiment, the advantage is utilized of being able to mount the operating coils to the outer ring of the iron core in a simple manner and then locking them with the aid of the attachment of the legs.

Claims

1. An electromagnetic operating device with at least one operating unit composed of one fixed and one movable magnet part, wherein the fixed magnet part comprises a first opera¬ ting coil (11) fixed to a first magnetic core (3) and a second operating coil (10) fixed to a second magnetic core (4), and the movable magnet part comprises an armature (2) which is displaceable in two directions, characterized in that the armature (2) is adapted to move along a circular path towards the first magnetic core (3) by activation of the first operating coil (11) and towards the εecond magne¬ tic core (4) by activation of the second operating coil (10) and that an air gap (9) between the armature (2) and the magnetic core (8) of the activated coil decreases during the movement.

2. An operating device according to claim 1, characterized in that the armature (2) is fixed to a rotary device (1) .

3. An operating device according to claim 2, characterized in that the rotary device comprises at least two rotation¬ ally symmetrically placed armatures (2, 2 .

4. An operating device according to any of the preceding claims, characterized in that the first magnetic core (3) and the second magnetic core (4) are comprised in a common magnetic body (20) surrounding the armature.

5. An operating device according claim 4, characterized in that the surrounding magnetic body (20) is composed of sepa¬ rate partε, which are linked together so as to facilitate an asεembly.

6. An operating device according any of the preceding claims, characterized in that the air gap (9) between the armature (2) and the magnetic core (8) during the whole movement is surrounded by the activated operating coil (11) .

BAD ORIGINAL

7. An operating device according any of the preceding claims, characterized in that confronting pole surfaces of the armature (2) and the magnetic cores (3, 4) are oriented in a direction radial with respect to the circular movement.

8. An operating device according any of claims 2 and 3, characterized in that the rotary device (1) comprises a crank (25) for transferring the rotary movement into a translatory movement.

9 An electric switching device for high voltage with an operating device, characterized in that the electric switching device is provided with an operating device accor¬ ding to any of the preceding claimε.

10. A method for operation of an operating device with at least one operating unit composed of one fixed and one movable magnet part, wherein an armature (2) comprised in - the movable magnet part is brought to be displaced in two directions, characterized in that the armature (2) is displaced along a circular path towards a first magnetic core (3) when a first operating coil (11) fixed to the first magnetic core (3) is activated and towardε a second magnetic core (4) when a second operating coil (10) fixed to the second magnetic core (4) iε activated, and that the armature and the magnetic core of the operating coil which is acti¬ vated are arranged such that an air gap (9) present there¬ between decreaseε with the movement.