WO2017076447A1

WO2017076447A1 - An electromagnet device

Info

Publication number: WO2017076447A1
Application number: PCT/EP2015/075780
Authority: WO
Inventors: Alfred NILSSON; Gunnar Johansson
Original assignee: Abb Schweiz Ag
Priority date: 2015-11-05
Filing date: 2015-11-05
Publication date: 2017-05-11

Abstract

The present invention relates to an electromagnet device (1 ) for a switching apparatus, the electromagnet device comprising a coil (4) arranged to generate a magnetic flux through a magnetic circuit (M. M') when it is excited, a magnet yoke (2) having two lateral legs (20, 20') and an elongated base (22) including a central portion (24), and an armature (3) including a central leg (32) with a free end facing the central portion of the magnet yoke and is movable along a movement axis of the armature between a rest/open position and a working/closed position when operating the switching apparatus. The armature further comprises two arms (30, 30'), each of the arms (30, 30') including a portion (34, 34') extending along the movement axis (Y-axis) of the armature (3) towards the magnet yoke (2) such that, when the armature (2) is moving from the open position to the closed position, each of the extended portions (34, 34') moves in parallel adjacently along a corresponding lateral leg (20, 20') and a single working gap (40) is formed the free end of the central leg (32) of the armature (3) and the central portion (24) of the magnet yoke (2).

Description

AN ELECTROMAGNET DEVICE

FIELD OF THE INVENTION

The present invention relates to an electromagnet device for a switching appa- ratus. Such a switching apparatus may be used for controlling an electrical power of an electrical device, for example a motor, a heating apparatus, a lighting apparatus, or a capacitor bank. The present invention particularly relates an electromagnet device intended to be used for long displacement strokes.

BACKGROUND

An electromagnet device is used to operate (open or close) a contact system of a switching apparatus, wherein the contact system comprises a movable contact and a stationary contact. Such an electromagnet device includes an excitation coil for generating a magnetic field, a fixed magnet yoke and a movable magnet armature connected to the movable contact. The movable magnet armature is movable between a rest/open position and a working/closed position. During a transition period from the open position to the closed position, a working air gap is formed between the fixed magnet yoke and the mov- able magnet. It is known that more than one working air gap, for example E- shaped electromagnet device, may partly result in power loss due to a harsh decrease of a magnetic force and is therefore difficult to achieve a long displacement stroke. US 2003/0189474 A1 discloses a DC electromagnet system includes a fixed U-shaped magnet yoke and a movable, rod-shaped armature is guided in its displacement stroke by guide devices, the free end of the armature being directed toward the central web of the magnet yoke. A single working air gap is formed between the free end of the armature and the centre of the central web. The ends of the yoke legs extend to the proximity of the armature and are separated from the armature, each forming a parasitic air gap. SUMMARY OF THE INVENTION

The object of the present disclosure is to provide an improved electromagnet device to achieve long stroke operations efficiently.

The present disclosure provides an electromagnet device as defined in the preamble of claim 1 . The armature of the electromagnet device armature further comprises two arms, each including a portion extending along the movement axis of the armature towards the magnet yoke such that when the arma- ture is moving from the open position to the closed position, each of the extended portions moves in parallel adjacently to a corresponding lateral leg and a single working gap is formed between the free end of the central leg of the armature and the central portion of the magnet yoke. During a transition from the open position to the closed position, a constant air gap is formed between each of the extended portion of the arms of the armature and the respective lateral leg of the magnet yoke. Since the extended portions move in parallel adjacently to the lateral legs, the formed constant air gap is narrow and constant compared to the air gap between the free end of the central leg of the armature and the central portion of the magnet yoke so that it is can be negligible. Thus a single effective working air gap is achieved, which minimises a power loss at a long displacement stroke.

At a closed position, the magnet yoke and the armature are essentially in con- tact with each other so that the constant air gap is excluded from the magnetic circuit.

The extended portions and lateral legs may be constructed in different ways to exclude the constant air gap at a closed position. Preferably, each of the ex- tended portions of the arms is arrange at the end of each of the arms and at a closed position, each of the arms of the armature and the respective lateral leg are essentially in contact with each other so that the constant air gap is excluded from the magnetic circuit.

According to one embodiment of the invention, each of the extended portions of the armature is in parallel with the respective lateral leg of the magnet yoke to maintain the constant air gap.

According to another embodiment of the invention, each of the extended portion of the arms has a length longer than a distance between the open position and the closed position.

According to yet another embodiment of the invention, the shortest distance of the working air gap is inclined at an angle with respect to the movement axis of the armature during at least part of the transition from the open position to closed position.

Furthermore, the central portion protrudes upward to the free end of the central leg of the armature so that the single working air gap is formed between the protruded central portion and the free end of the central leg.

Preferably, the single working air gap formed between the central leg of the armature and the central portion of the magnet yoke includes a trapezoid shape. Alternatively, the single working air gap formed between the central leg of the armature and the central portion of the magnet yoke includes a wedge shape.

The angled single working air gap enables a closer distance between the free end of the armature and the central portion of the magnet yoke and conse- quently decrease the working air gap and maintains magnetic force. According to one embodiment of the invention, the coil is wound around a bobbin. The bobbin is arranged to be inserted downward into a profile formed by the magnet yoke and the armature during an assembling process. At least one of the magnet yoke and the armature are made of stacked sheets of metal material.

To achieve a well-balanced force between the armature and the magnet yoke, the magnet yoke and the armature are designed symmetrically with respect to the movement axis of the armature.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

Fig. 1 a-b show a front and a perspective views of an electromagnet device, according to a first example of the invention.

Fig. 2a and 3a show magnetic flux paths through the magnetic circuits at an open position and closed position of the first example of Figs. 1 a-b.

Fig. 2b-f show five other examples of the invention and corresponding magnetic circuit at an open position. Figs. 3b-f show the magnetic flux path through the magnetic circuit at a closed position of each of the examples of Figs. 2b-f.

Figs. 4a-d show four profiles of working air gaps, according further examples of the invention, where each of the working gaps includes either a wedge shape or a trapezoid shape. Fig. 5a shows an exploded view according to the example of the invention as shown in 1 a-b, wherein a bobbin is inserted downward to the magnet yoke.

Fig. 5b shows a partial perspective of the example as shown in 5a, wherein the magnet yoke is anchored/attached on the bottom of the bobbin via a rod.

Fig. 6 shows a comparison diagram wherein a magnet strength at a longer stroke is improved by the configuration of the single wedge-shaped working air gap according to the invention.

Figs. 7a-b show a partial perspective and cross sectional views of a switching apparatus having a main movable contact and stationary contact, wherein the main movable contact is actuated by the electromagnet device via a main contact carrier.

Fig. 8 shows an inner perspective view of a cover for the switching apparatus of Figs. 7a-b.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art.

A number of variations of an electromagnet device for a switching apparatus will be described herein. The switching apparatus may be any of contactor, circuit breaker, or switch-disconnector. With reference to figures 1 a-b and 6, an electromagnet device 1 for a switching apparatus comprises comprising a coil 4, a magnet yoke 2 and an armature 3. The coil is arranged to for energizing the magnet yoke 3 and the armature 2 and, a magnetic field/circuit is formed therethorugh. An electronic circuit (not shown in the figures) may be arranged for controlling electric power supplied to the coil 4. In this example the coil is further wound around a bobbin 5. The bobbin 5 is arranged to anchor the magnet yoke 2 via a rod 6, to hold the coil winding and guide the armature 3 during its displacement stroke. The magnet yoke 2 is U-shaped and is fixedly connected to the switching apparatus and is arranged to be cooperated with the armature 3. It further includes two lateral legs 20, 20' and an elongated base 22 including a central portion 24. The armature 3 includes a central leg 32 with its free end facing the central portion 24 of the fixed magnet yoke 2. The armature 3 is further connected to a movable contact of the switching apparatus via a contact bridge for actuating the movable contact and is movable along a movement axis, in this example represented by a Y-axis, of the armature 3 between a rest/open position and a working/closed position when operating the switching apparatus. In this example, the armature 3 is T-shaped and further comprises two arms 30, 30'. Each of the arms 30, 30' includes a portion 34, 34' extending along the Y-axis towards the magnet yoke 2.

In its displacement stroke, meaning that when the armature 3 is moving from an open position to a closed position, an electric power is supplied to the coil that further energizing the fixed magnet yoke 2 and the armature 3 so that the armature 3 is attracted then moves to the fixed magnet yoke 2 to take up a working/closed position. When taking the closed/working position, the extended portion 34, 34' is arranged to move essentially in parallel with and proximity to a corresponding lateral leg 20, 20' so that an air gap 42, 42' is formed therebetween. The parallel arrangement between the extended portion 34, 34' and the lateral legs 20, 20' enables the air gap constant; while the proximity ensure a narrow air gap. Therefore, this constant narrow air gap 42, 42' can be negligible, which results that a single effective working gap 40 is formed the free end of the central leg 32 of the armature 3 and the central portion 24 of the magnet yoke 2. The central portion 24 protrudes upward to the free end of the central leg 32 of the armature 3 so that the single working air gap is formed between the protruded central portion and the free end of the central leg.

Because a magnetic force is inversely proportional to the squared distance of an air gap, the number of air gaps will drastically decreases the magnetic force. Thus, a single working gap will significantly decrease the magnetic force/strength loss, particularly at a longer stroke.

Having the central portion 24 extended towards the armature 3, rather than the opposite direction, makes the electromagnet device more compact since it does not need to increase a total height of the magnet. Thus, a manufacturing cost will be decreased since there is no demand to increase the size/dimension of such an electromagnet device in a long stroke application in order to decrease loss of magnet forces.

Preferably, each of the extended portions 34, 34' has a length longer than a distance between the open position and the closed position, i.e. a stroke distance to establish the constant air gaps. Moreover, the extended portion 34, 34' is not as the same thickness as the lateral leg 20, 20', preferably thinner than the latter.

With reference to Figure 1 b, at least one of the magnet yoke and the armature are made of stacked sheets of metal material. Preferably, all portions of both the fixed magnet yoke 2 and the armature 3 are designed to be symmetric with respect to the Y-axis. With reference to Figures 4a-d, during its placement stroke i.e. at least part of the transition from the open position to closed position, the shortest distance of the working air gap is inclined at an angle a with respect to the Y-axis. The angled air gap further increases the magnet force/strength for longer strokes. Preferably, the formed working air gap includes a trapezoid shape or a wedge shape. Both profiles are symmetrical with respect to the Y-axis to ensure cancellation of sideward directed forces thus to improve stability. Having a wedge-shaped or trapezoid shape single working air gap significantly improves magnet strengths at longer strokes comparing with an existing T-shaped magnet. This has been confirmed by measurement data shown in the diagrams of Figure 6, wherein the dotted line presents one example of the invention; while the straight solid line presents the T-shaped magnet. However, it should be understood that other shaped profiles of the working air gap may be possible, for example, a teeth profile or a curve profile.

Figures 2a and 3a show a configuration of the electromagnet device in an open position and a closed position respectively, according to a preferred ex- ample of the invention.

In this example, each of the extended portions 34, 34' of the arms 30, 30' is arrange at the end of each of the arms. At the open position as shown in Figure 2a, there is a constant narrow air gap between each of the extended por- tions 34, 34' and the corresponding lateral leg 20, 20', which lead magnetic circuit M, M' from the extended portion to the lateral leg due to the fact that the magnetic flux of a magnetic circuit will go a path that has a least resistance, thus meaning a shortest air path. The magnetic circuit consists of two halves M, M' that are symmetrical with respect to the Y-axis. Thus, each half of the magnet circuit M, M' comprises a constant air gap 42, 42'. At a closed position as shown in Figure 3a, the inner surfaces 38, 38' of the arms 30, 30' of the armature 3 is essentially in contact with the end surface 28, 28' of the respective lateral leg 20, 20', thus the constant air gap 42, 42' between the extended portion 34, 34' and the lateral lag 20, 20' is excluded from the magnetic circuit M, M'. Simultaneously, the horizontal surfaces 36, 36' of the free end of the central leg of the armature and the horizontal surfaces 26, 26' of the central portion of the magnet yoke is contact with each other and lead the magnetic flux path when the electromagnet.

Figures 2b-f and 3b-f show other five possible configurations of the extended portions in relation to the lateral lags at an open position and a closed position respectively.

In Figure 2b and 3b, the extended portion 134, 134' is not arranged at the end of each of the arms 130, 130' of the armature 103, rather at a distance to the end of each of the arms 130, 130', which allows the extended portions 134, 134' move along inner side of the corresponding lateral lag 120,120' and a constant air gap 142, 142' is formed therebetween. At a closed position as shown in Figure 3b, the inner surfaces 138, 138' of the arms 130, 130' of the armature 103 is essentially in contact with the end surface 128, 128' of the re- spective lateral leg 120, 120', thus the constant air gap 142, 142' between the extended portion 134, 134' and the lateral lag 120, 120' is excluded from the magnetic circuit M, M'. Simultaneously, the horizontal surfaces 136, 136' of the free end of the central leg of the armature and the horizontal surfaces 126, 126' of the central portion of the magnet yoke is essentially contact with each other and lead the magnetic flux path when the electromagnet.

In the examples shown in Figures 2c-d and 3c-d, at closed position, the contact is made between the elongated base 222, 322 and the end of the extended portion 234, 334. The difference between the examples shown in Figures 2c and 2d is that the lateral legs 220, 320 of the magnet yoke 202, 302 are arranged differently in relation to the ends of the elongated base. Therefore the extended portions 234, 334 of the armature 203, 303 move either along inner side or outer side of the lateral legs 220, 320. In figures 2c and 3c, each of the lateral legs 220, 220' is arranged at a distance to the end of the elongated base 222 to allow the extended portions 234, 234' moves along the outer side of the corresponding lateral legs 220, 220'. In Figures 2d and 3d, each of the lateral legs 320, 320' is arranged at the ends of the elongated base 322 to allow the extended portions 334, 334' to move along the inner side of the lateral leg when taking a working/closed position. In the examples shown in Figures 2e-f and 3e-f, each of the lateral legs 420, 420'; 520, 520' further includes a shoulder portion 423, 423'; 523, 523'. At the closed position, each of the extended portions 434, 434'; 534, 534' of the armature 403, 503 is essentially contact with the corresponding shoulder portion 423, 423'; 523, 523' of the lateral legs 420, 420'; 520, 520' so that the constant air gaps 442, 442'; 542, 542' are excluded from the from magnetic circuit M, M'. Alternatively, shoulder portions may be arranged on extended portions of an armature so that, at the closed position, each of the lateral legs of the magnet yoke is essentially contact with the corresponding shoulder portion of the extended portions to exclude constant air gap from the from magnetic circuit M, M'.

Figure 5a shows that bobbin 5 is arranged to be assembled vertically. During an assembling process, the bobbin 5 is first inserted downward into an inner space formed by the lateral legs 20, 20' and the central portions 24 of the magnet yoke 2. The magnet yoke 2 is further anchored on the bottom of the bobbin 5 via a rod 6 as shown in Figure 5b. Furthermore, the bobbin 5 is arranged to guide the armature 3 during its displacement stroke through a cavity.

Figure 7a and 7b show a switching apparatus 1 -1 with a parallel double break and make structure. The switching apparatus comprises two stationary main contacts 1 -50, 1 -50' and two stationary arcing contacts 1 -20, 1 -20', each of the stationary arcing contacts 1-20, 1-20' being positioned in parallel with a corresponding stationary main contact 1-50, 1-50'. In this example, each of the stationary arcing contacts 1-20, 1-20' is attached a stationary main contact 1-50, 1-50'. Furthermore, each of the stationary arcing and main contacts 1-20, 1- 20'; 1-50, 1-50' are aligned with the corresponding movable arcing and main contacts 1-30; 1-40. Each of the movable main and arcing contacts 1-30; 1-40 includes two arms, each including two contact tips 1-32, 1-32'; 1-42, 1-42' to be in contact with corresponding contact tips 1 -22, 1 -22'; 1-12, 1 -12' of the corresponding stationary main and arcing contacts 1-50, 1-50'; 1-20, 1-20', which thus enable double contacting points connected in series for each of the arcing and main contacts when a contact is made. The main movable contact 1-40 is actuated by an electromagnet device 1-10 according to the present invention via a main contact carrier 1-60. The arc movable contact 1-30 is attached to an arc contact carrier 1-70 that is actuated by an actuating means.

With a further reference to Figure 8, the switching apparatus 1-1 further comprises a base 1-200 and a cover 1-100. A damping element 1-110 is attached to the inside of the cover 1-100 for damping a hard and sudden force on the contact carriers caused by an opening operation. In this example, there are four damping elements 1-110 attached to the cover 1 -100.

Claims

1 . An electromagnet device (1 ) for a switching apparatus, the electromagnet device comprising

- a coil (4) arranged to generate a magnetic flux through a magnetic circuit (M. M') when the coil (4) is excited,

- a magnet yoke (2) having two lateral legs (20, 20') and an elongated base (22) including a central portion (24), and

- an armature (3) including a central leg (32) with a free end facing the central portion of the magnet yoke and is movable along a movement axis of the armature between a rest/open position and a working/closed position when operating the switching apparatus,

characterized in that the armature further comprises

- two arms (30, 30'), each of the arms (30, 30') including a portion (34, 34') extending along the movement axis (Y-axis) of the armature (3) such that,

- when the armature (2) is moving from the open position to the closed position, each of the extended portions (34, 34') moves in parallel adjacently along a corresponding lateral leg (20, 20') and a single working gap (40) is formed between the free end of the central leg (32) of the armature (3) and the central portion (24) of the magnet yoke (2).

2. Electromagnet device of claim 1 , wherein, at a closed position, the magnet yoke (2) and the armature (3) are essentially in contact with each other so that a constant air gap (42, 42') formed between each of the extended portions (34, 34') of the arms (30, 30') of the armature (3) and the respective lateral leg (20, 20') of the magnet yoke (2) is essentially excluded from the magnetic circuit (M, M').

3. Electromagnet device of claim 2, wherein each of the extended portions (34, 34') of the arms is arrange at the end of each of the arms (30, 30') and, at a closed position, each of the arms (30, 30') of the armature (3) and the respec- tive lateral leg (20, 20') are essentially in contact with each other so that the constant air gap is excluded from the magnetic circuit.

4. Electromagnet device of claim 1 , wherein each of the extended portions (34, 34') of the armature (3) is positioned in parallel with the respective lateral leg

(20, 20') of the magnet yoke (2).

5. Electromagnet device of claim 1 , wherein each of the extended portion has a length longer than a distance between the open position and the closed posi- tion.

6. Electromagnet device of claim 1 , wherein the central portion (24) protrudes upward to the free end of the central leg of the armature so that the single working air gap (40) is formed between the protruded central portion (24) and the free end of the central leg (32).

7. Electromagnet device of claim 1 , wherein, during at least part of the transition from the open position to closed position, the shortest distance of the working air gap is inclined at an angle (a) with respect to the movement axis of the armature.

8. Electromagnet device of claim 7, wherein the formed working air gap includes a trapezoid shape.

9. Electromagnet device of claim 7, wherein the formed working air gap includes a wedge shape.

10. Electromagnet device of any of the previous claims, wherein the coil (4) is wound around a bobbin (5) to be inserted downward into a profile formed by the magnet yoke and the armature during an assembling process.

1 1 . Electromagnet device of any of previous claims, wherein at least one of the magnet yoke (2) and the armature (3) are made of stacked sheets of metal material.

12. Electromagnet device of any of previous claims, wherein both the fixed magnet yoke (2) and the armature (3) are symmetric with respect to the movement axis (Y-axis) of the armature.