GB2156156A

GB2156156A - Electromagnetic switch arrangement

Info

Publication number: GB2156156A
Application number: GB08506347A
Authority: GB
Inventors: Konstantin Kelaiditis
Original assignee: Hager Electro GmbH and Co KG
Current assignee: Hager Electro GmbH and Co KG
Priority date: 1984-03-15
Filing date: 1985-03-12
Publication date: 1985-10-02
Also published as: GB2156156B; FR2561435A1; GB8506347D0; DE3409513A1

Abstract

In an electromagnetic switching arrangement an armature is actuated by two coils (12) and (13) switched in series and arranged concentrically around it. The inner coil (12) has a smaller resistance, the outer coil (13) a high resistance. In the first part of its movement the armature closes contacts (45) which by-pass the coil 13 so that a very much stronger current flows in the coil (12) and the armature receives great mechanical energy on its further path. At the end of the armature movement the current flow through the coils (12) and (13) is interrupted by opening further contacts (11). With coils in parallel contacts are closed during first part of armature movement to bring the second coil into use. <IMAGE>

Description

SPECIFICATION Electromagnetic arrangement, in particular in switchgear The invention relates to electromagnetic arrangements, in particular in switchgear, of the type in which an armature is moved by a current-carrying coil when a threshold value of the current intensity is exceeded.

Arrangements of this type are known for many purposes, in which the movement of the armature is always used in some way or other. Its use is widespread for switchgear such as circuit breakers, contactors, relays, other switches and so forth.

A basic problem with these arrangements is the ratio between the threshold value at which they operate and the speed with which its movement then occurs, or the energy which they make available for the purpose they have to serve. This ratio, which is moreover unfavourable for specific purposes, is usually impaired even more by the production of the cohesion required for the armature until the threshold value is attained by means of a spring. The spring is then tightened further during the movement of the armature and consequently progressively impairs this movement.

So as to have the force holding the armature until the threshold value is attained subsequently eliminated, the construction 6f the armature as iron-clad magnets with a permanently magnetic core which produces the cohesion is known. However such an iron-clad magnet is an expensive precision part, and furthermore a spring is nevertheless used in some way, in particular to bring back the armature.

A still unpublished proposal, which forms the content of German patent application P 33 35 465, represents a further step towards the improvement of the mentioned ratio.

However, despite all these efforts, the power and energy which an armature can develop in the electromagnetic arrangements under consideration remain limited until now.

The object of the invention is to increase the power and energy of such an electromagnetic arrangement.

According to the invention, such an electromagnetic arrangement is characterised by an appliance for producing an increased magnetic flux acting on the armature, said appliance being activated by a first part of the armature movement.

With this solution the electromagnetic arrangement is aligned on the one hand to the threshold value and on the other hand to the production of power and energy without any prejudice on either side.

The possibilities for implementing the invention are extremely varied.

The appliance for producing a higher magnetic flux acting on the armature can, for example, supply a higher voltage to an available coil or switch in a further coil or increase the conductivity of the magnetic circuit.

The supply of a higher voltage is, for example, possible by eliminating a resistor, i.e. by by-passing the resistor, by switching over to another voltage source or by switching to an energy store, which can also be a capacitor.

An increase in the magnetic conductivity is, for example, possible by eliminating a magnetic resistor in the magnetic circuit, i.e. by closing a gap in the soft iron core generally provided.

A combination of such different possibilities is also conceivable.

The appliance can be activated by a switch, but also in a different way. A sliding contact can be cancelled via a resistor or another receiver so that it is progressively eliminated, or via a transistor. The transistor can also be controlled by changing its basic current.

These possibilities of activating the appliance for producing an increased magnetic flux partially represent this appliance itself as well.

In accordance with a preferred embodiment of the invention the said appliance comprises a second coil with a higher resistance switched in series with the coil and arranged concentrically around the first coil and a switch in a lead by-passing this so that the switch is closed with the first part of the armature movement.

The second coil then, together with the first, limits the current flowing in this until the arrangement is actuated. If the threshold value of the current is exceeded and has then actuated the arrangement, the total resistance of the arrangement is limited to that of the first coil by the immediate by-passing of the second coil of higher resistance switched in series with the first coil. In this now flows a relatively strong current, from which the armature can develop a relatively large amount of mechanical energy. From this point of view the coil is also arranged as the inner coil of the two concentric coils.

According to another embodiment of the invention, the said appliance has two coils switched in parallel and arranged concentrically and, in the lead of the inner coil, a switch, so that the switch is closed in the first part of the armature movement.

The inner coil is then switched in here. This preferably has a lower resistance than the other.

This arrangement has the advantage that both coils are available to produce energy for the armature movement.

Which of the two embodiments is the more favourable depends on the circumstances.

Also the importance of the mechanical implementation may be a decisive factor.

The armature could also be constructed of many parts with an auxiliary armature only for actuating the said switch.

In the drawings exemplified embodiments of the invention are shown.

Figure 1 shows a circuit breaker with an electromagnetic arrangement in accordance with the invention.

Figure 2 shows a section from Fig. 1 in another position of the circuit breaker.

Figure 3 shows a section from Fig. 2 in a further position of the circuit breaker.

Figure 4 to Figure 6 show wiring diagrams of other electromagnetic arrangements.

Through the circuit breakers represented in Fig. 1 to 3 runs a main current path 1, in which are arranged a thermal tripping device 2 responding to excess current, a magnet mechanism 3 responding to short circuit and a disconnecting point 4 actuated by the thermal tripping device 2 (not shown) and by the magnet mechanism 3.

The magnet mechanism 3 and the disconnecting point 4 are bypassed by a secondary current path 5. In this are arranged an electric resistor 6 of 0.1 to 5, for example, or even up to 10 Ohm for rated voltage intensities of 6-100 A, another thermal tripping device 7 and a second disconnecting point 8. Behind the disconnecting points 4 and 8 branches another current path 9 via another magnet mechanism 10 and a third disconnecting point 11 the further circuit 9 leads through an inner coil 1 2 of 10 Ohm, for example, and then through an outer coil 13 of 100 Ohm, for example. The disconnecting point 11 is formed by a a swivelling contact arm 1 6 and a sliding contact piece 1 7 with which the contact arm 1 6 works.Between the two coils branches off at 14 a bypass lead 1 5. It leads via a disconnecting point 45 and then again joins the further current path 9 at 46. The disconnecting point 45 is formed by a swivelling contact arm 47 and a sliding contact piece 48.

The thermal tripping device 2 acts via a locking cam, not shown, on the second disconnecting point 8. This disconnecting point, which is also not shown, is mechanically coupled with the disconnecting point 4 so that the disconnecting point 4 can open and close independently from the second disconnecting point 8, but when the second disconnecting point 8 opens it also opens The further thermal tripping device 7 also acts via the mentioned locking cam on the second disconnecting point 8.

Also the magnet mechanism 3 and the further magnet mechanism 10 act on the disconnecting point 4. The third disconnecting point 11 is coupled with the disconnecting point 4 so that the one opens when the other closes. These connections are mechanically implemented as follows: The further magnet mechanism 10 and a tension spring 1 9 act in different directions of rotation on a two-arm lever 21 stored at 20, which at one of its ends bear a contact piece 23 working with a contact piece 22 stored at a spring swivel arm. The contact pieces 22 and 23 represent the disconnecting point 4.

At its other end the lever 21 is provided with a notch element 24. This acts with a ratchet 25 which is fitted at one end of a further twoarm lever 27 stored at 26, on which the magnet mechanism 3 acts against the force of the tension spring 28 in the direction of the tripping. A bar 29, fixed at both its ends, extends from the notch element 24 to the contact arm 16. A tension spring 30 only fastens the armature 32 of the magnet mechanism 3 in its inactive initial position, while a tension spring 31 pulls the armature 33 of the magnet mechanism 10 into its initial position and at the same time draws the contact arm 47 into its initial position via a bar 49 and a pressure spring 34 in the normal operating position of the arrangement shown in Fig. 2 determines the contact force between the contact pieces 22 and 23 at the disconnecting point 4.In this position the notch element 24 is held by the ratchet 25.

When the disconnecting point 4 is closed (Fig. 2), the normal current flow passes via the main current path 1. The simultaneous current flow via the secondary current path 5, in which the disconnecting point is also closed, is insignificant because of the resistor 6. The further current path 9 is interrupted by the open disconnecting point 11.

If a short circuit occurs (Fig. 1), the magnet mechanism 3 tightens with the then very much stronger current and moves the lever 27; the ratchet 25 is tripped. The tension spring 19 pulls the lever 21 and deviates it until it touches a cam 35 of the armature 33.

The disconnecting point 4 opens. The disconnecting point 11 is closed via the bar 29.

By opening the disconnecting point 4 the main current path is immediately interrupted.

A considerably reduced current flows on via the secondary current path 5. The further current path 9 is, despite its disconnecting point 11 being closed, almost dead as a result of the drop in potential owing to the short circuit.

If, for example, the short circuit lies in the lead section between the available circuit breaker and a circuit breaker connected at the outlet side, then, after a certain time period for which it is designed, the thermal tripping device 7 actuates the mentioned locking cam and thereby also opens the disconnecting point 8. The disconnection by the circuit breaker is now complete and final.

If the short circuit is behind a circuit breaker connected at the outlet side, this generally acts more or less simultaneously with the magnet mechanism 3, but in any case long before the thermal tripping device 7, and cuts off the short circuit point. Conse quently the voltage at the entrance to the further current path 9 rises. In this there now occurs a current of such intensity that it operates the magnet mechanism 10 and attracts the lever 21.With the associated swivelling of the contact arm via the bar, as soon as the contact arm reaches the sliding contact piece (Fig. 3) and consequently closes the fourth disconnecting point 45, the outer coil 1 3 in the magnet mechanism 10 is bypassed: at the branch 14 the current takes the path without resistance through the by-pass lead 1 5. As a result the current intensity in the inner coil 1 2 is raised, and consequently the force exerted on the armature 33. On its further path the armature 33 now receives enough energy to shut the disconnecting point 4 by tightening the tension spring 34 and to engage the notch element 24 on the ratchet 25, during which the ratchet 25 has to be pushed aside by tightening the tension spring 28 of the notch element 24, sliding on this.The lever 27 with the ratchet 25 was returned to its initial position immediately after opening the disconnecting point 4 together with the armature 32 as a result of the pull on the tension spring 28.

The disconnecting point 11 is then opened again. The further current path 9 and the further magnet mechanism 10 are dead. The tension spring 31 pulls back the armature 33 and also opens the disconnecting point 45.

Consequently the normal condition of the circuit breaker is produced again. All consuming devices connected at the outlet side other than that in whose branch the short circuit occurs are furthermore live.

If excess current occurs, the thermal tripping device 2 operates and trips the mentioned locking cam. This opens the disconnecting point 8, which in turn opens the disconnecting point 4 via the further mentioned couplings which are not shown. In this case too the disconnection by the circuit breaker is complete and final.

Such couplings are known from German Offenlegungsschrift 33 1 6 230, as is the basic principle of the circuit breaker described.

The circuit diagrams shown in Fig. 4 and 5 correspond to the arrangement shown in Fig.

1 to 3. In Fig. 4 there is merely a modification in the arrangement of the disconnecting points. In Fig. 4 and 5 the inner coil 1 2 and the outer coil 1 3 are again found, and in Fig.

4 disconnecting points 11 and 45 as well. In Fig. 5 the disconnecting point or the switch 37 corresponds to the disconnecting point 11 and the disconnecting point or switch 39 to the disconnecting point 45. The arrangement according to Fig. 5 has the advantage that the switch 37 is protected.

The coils 40 and 41 shown in Fig. 6 are switched in parallel. The coil 40 corresponds to the inner coil 12 and the coil 41 to the outer coil 1 3 insofar as these are regarded as inner and outer coils of the magnet mechanism 10 and the coil 41 serves to operate the magnet mechanism and the coil 40 serves to supply more energy for the work of the armature after the mechanism is actuated. For these different purposes the coil 41 could, for example, have 1 30 Ohm and the coil 40 could, for example, have 20 Ohm. The switches 42 and 43 in Fig. 6 correspond to the disconnecting points 11 and 45 in that the former switches in the magnet mechanism under consideration and the latter is actuated after the operation of the magnet mechanism and switches over to a lower resistance in this.

Claims

1. An electromagnetic arrangement for switchgear, of the type in which an armature is moved by a current-conducting coil when a threshold value of the current intensity is exceeded, characterised by an appliance (12-15 or 40) for producing an increased magnetic flux acting on the armature, said appliance being activated (45 or 43) by the first part of the armature movement.

2. An arrangement according to Claim 1, characterised in that the said appliance has a resistor (13) switched in series with the coil (12) and a switch (45) in a lead (15) bypassing the resistor (13) so that the switch (45) is closed with the first part of the armature movement.

3. An arrangement according to Claim 2, characterised in that the resistor is a second coil (13) of higher resistance, preferably arranged concentrically around the first (12).

4. An arrangement according to Claim, characterised in that the said appliance has two coils (40; 41) switched in parallel, preferably in concentric arrangement, and in the lead of one coil (40), preferably the inner one, the appliance has a switch (43) so that the switch (43) is closed with the first part of the armature movement.

5. An electromagnetic arrangement, constructed, arranged and adapte to operate substantially as herein before described with reference to, or as shown in, the accompanying drawings.

6. Switchgear incorporating an electromagnetic arrangement as claimed in any one of the preceding claims.