EP2718953B1

EP2718953B1 - Electromagnetic relay with improved yoke, in particular a relay for interruption of electric circuit in the case of diffferential current, and switch comprising such relay

Info

Publication number: EP2718953B1
Application number: EP12762094.6A
Authority: EP
Inventors: Mitja Koprivsek; Mitja VOZEL; Matija Strehar; Anton Hamler
Original assignee: ETI Elektroelement dd
Current assignee: ETI Elektroelement dd
Priority date: 2011-06-06
Filing date: 2012-06-04
Publication date: 2015-09-30
Anticipated expiration: 2032-06-04
Also published as: WO2012169975A1; EP2718953A1

Description

The invention relates to a mechanism for activating an electromagnetic relay, which is intended to interrupt an electric circuit in the case of differential current in a phase conductor and a neutral conductor.
In accordance with the International patent Classification, such invention belongs to electricity and in such context to basic electric elements, namely to relays and switches, which include a permanent magnet and which are intended to protect electric circuits. Optionally, such invention can also refer to construction details of electromagnetic relays.
The purpose of the invention is to improve a reliability of operating a relay and consequently also of a switch comprising such relay, despite to essential simplified manufacturing of components thereof. Such yoke should namely be created in such manner that manufacturing thereof could be essentially simplified than manufacturing of yokes for relays according to state of the art, by which extremely strict requirements in view of accuracy should be eliminated, by which also a reliability of operation of the relay as such could be essentially improved. The purpose of the invention is simultaneously also improvement of a switch for interruption of electric circuit in the case of differential current, in which such relay is integrated.
An electromagnetic relay is described in EP 0 508 052 B1 and consists of a casing, within which an electromagnetic inductive coil is placed and is due to actuating at a low electric power electrically interconnected with a phase conductor and a neutral conductor via a passive electronic circuit and an electric transformer. A yoke is placed within a core of said coil and is connected with a so-called L-yoke comprising a first arm, which extends in a direction of said yoke of the coil, and a second arm, which extends perpendicular in a direction away from the coil. A further S-yoke is foreseen adjacent to said L-yoke and consists of a central region as well as of two arms. The first arm of said S-yoke extends parallel with said first arm of the L-yoke, while the central region of the S-yoke extends perpendicular with respect to said first arm and in a direction away from the coil. The second arm of said S-yoke extends parallel with respect to the first arm and at a distance apart from the coil. A permanent magnet is inserted between the second arm of said L-yoke and the central region of the S-yoke. An armature is placed over the coil and the second arm of the S-yoke, and is supported in a pivot point, which is located on the second arm of the S-yoke on the side opposite to the yoke of the coil. The coil is therefore with respect to said pivot point in the area of its one end portion supported by means of the yoke of the coil, while on its other end portion it is connected with a tension spring, which is on the other hand attached to said casing. An actuating needle is mounted on the coil.
A magnetic field, which is thanks to said permanent magnet constantly present within such relay, maintains the armature in its position where it abuts the yoke of the coil and also the second arm of the S-yoke against the force of the spring, which results in tendency of rotating the armature around the pivot point and displacing it apart from the yoke of the coil together with displacing said actuating needle, which is rest on the armature. Maintaining the armature in its previously described position must be reliable just in order to prevent undesired actuating due to mechanical influences, e.g. due to vibrations or the like. Whenever the electric circuit is operating regularly and the current in the phase conductor is equal to the current in the neutral conductor, the differential current does not exist, and the permanent magnet produces a force, which is stronger than the force produced by the spring, by which the armature is maintained in the described position. In the case of differential current between the phase conductor and the neutral conductor, another magnetic field is generated within the coil, which starts acting opposite to the previously mentioned magnetic field, and the effectiveness of the permanent magnet is correspondingly reduced, so that the force produced by the spring is then stronger than the magnetic force, upon which the armature is pivoted around its pivot point, and the actuating needle is triggered for the purposes of interrupting the electric circuit, in which the differential current is detected. Manufacturing of such relay is of quite technological reasons extremely complicated and also connected with high risk of achieving each required accuracy.
Moreover, a yoke is described in EP 0 829 895 , which is intended to cooperate with a permanent magnet and is formed of two parts consisting of high-permeable ferromagnetic material, which are welded to each other and are arranged at a pre-determined distance with respect to each other. At least in the area of welding, it is extremely difficult to assure each required magnetic properties within a very narrow range, which is however unavoidable required for the purposes of a correct functioning. Namely, a very narrow air-gap is foreseen between two planar surfaces of both parts of said yoke, the thickness of which should normally be less than 50 µm, and in accordance with EP 786 789 less than 40 µm. Each required magnetic characteristics can be achieved only when said width of the air-gap does not differ from said value for more than 10 - 20%, which practically means that both parts must be machined, assembled and interconnected in an extremely precise manner, where the admissible tolerance i.e. variation of the width of the gap shall be less than 5 µm, which is in practice extremely difficult to achieve, and in a mass production the risk of declaring a plurality of practically finished products as irregular and throwing them out is pretty high, since such irregular products do not meet requirements and cannot enable regular functioning. In such yoke, which was accurately manufactured and met all requirements during the previously mentioned stage, the width of said air-gap can also be subsequently amended during insertion into a relay or a switch, or during the use of the relay as such, which results in irregularities in operation of the relay and consequently of the complete switch.
Manufacturing and finalization of said gap is described in EP 0 984 477 and is extremely complicated due to a required preciseness of the width of said gap, which is however of crucial importance with respect to magnetic properties of a relay and indirectly also of the complete switch, and is moreover also connected with problems related to welding and relatively high risk of achieving each required performances of the final product. Namely, a method is proposed in the previously mentioned EP 0 984 477 , according to which both parts of the yoke are separately manufactured and upon that assembled, wherein by approaching to each other the capacity is measured in order to determine appropriate width of the gap, by means of which subsequently each required magnetic property of the relay may be achieved. As soon as said parts are located in appropriate position relative to each other, welding thereof takes place. This practically means that said approaching of parts, defining each appropriate width of the gap and then welding of said parts is successively repeated for each particular products, which is time consuming and expensive. Besides, the gap may upon said welding still be amended due to thermal extensions or any other influences, which can be measured and controlled after that, but such practically finalized product can then only be rejected as irregular and thrown away.
Moreover, due to the concept and arrangement of said yoke in the known relays, a relatively high level of magnetizing of a permanent magnet is required, which consequently results in a relatively high actuating threshold, which is in practice between 120 and 150 µVA, and which should from quite practical reasons preferably be set as low as possible.
In addition to said problems with assuring permeability of the yoke by means of said gap between both parts of the yoke, such state of the art concept of the yoke is not optimal even in the sense of action of forces, which also impacts efficiency and reliability of such relay during its operation. When considering the pivot point of the armature and the elastic force generated by a spring, the magnetic force is namely acting at a relatively small lever, so that relatively strong magnetic force needs to be generated by means of a relatively strong magnetic field of the permanent magnet, and compensation of such strong magnetic force is then possible only in the case of a relative high differential current, so that the switch is less sensitive with respect to small current differences.
In principle, each required strength of the permanent magnet could generally be reduced by using some less powerful spring. Less powerful magnet would be able to activate the relay and to pivot the armature away from the permanent magnet even in the case of smaller differential current. Consequently, the elastic force of the spring would be lower, and pivoting of the armature around its pivot point would be slow and less reliable, and impact force of the armature towards the actuating needle would be weak, so that the efficiency and reliability of such relay during the operation is then questionable.
The present invention refers to a switch for interruption of an electric circuit in the case of differential current, which is intended for integration into an electric circuit, which formed by appropriate direct voltage or alternating voltage or combined voltage source together with at least one load as well as with a phase conductor and a neutral conductor, which are connected to said source via the said switch, wherein such switch comprising

a differential transformer, in which its primary winding is formed by the phase conductor and the neutral conductor extending through a core thereof, and its secondary winding comprises two electric connectors;
a passive electronic circuit, comprising two pairs of connectors, between which a capacitor is serial connected to other parallel connected components and is adapted to be energized by means of electric voltage, which is induced in the secondary winding of the transformer, since said circuit is by means of its first pair of connectors electrically interconnected with the connectors of said secondary winding of said transformer;
a relay, which in the electrical context represents a resistance and inductivity of a coil with electric connectors, via which the relay is electrically interconnected with the second pair of connectors of the a passive electronic circuit for the purposes of energizing the coil by means of the voltage of said serial connected capacitor, wherein said relay in the mechanical contexts consists of a yoke, which comprises said inductive coil and a permanent magnet for providing a desired magnetic flux in the area of said yoke, as well as of an armature, which is pivotally interconnected with said yoke in a pivot point and is, depending on energizing the coil, either by means of said permanent magnet rest onto said yoke, or is by means of a force of a spring pivoted away from the yoke towards the actuating mechanism, which is located at appropriate distance apart from the yoke and is intended for activation of the switch in the sense of interrupting the electric circuit through said conductors.

In accordance with the invention, said yoke consists of two plate-like and apart from each other arranged parts consisting of high-permeable ferromagnetic material, which are each per see adapted to cooperate with a permanent magnet and between which a layer is inserted, which consists of composite material with relative permeability in the range 3 ≤ µ ≤ 15, wherein the thickness of said layer (310) is 0,1 to 1,0 mm.
In one of possible embodiments, said layer of composite material consists of powder particles of high-permeable material, the size of which amounts several nanometers up to several micrometers, which are interconnected by means of a binding on the basis of epoxy resins, wherein both parts of the yoke are connected to each other by means of said binding, which contain s said particles of high-permeable material.
Regarding the material, said powder particles can consist of alloy on the basis of iron and nickel.
In accordance with a further aspect of the invention, a position of the pivot point of rotating the armature relative to the yoke is defined within the area between the coil and the elastic force of the spring, and simultaneously, said armature is firmly interconnected with a projection, with which each disposable spring cooperates, wherein said projection is created in such manner that by pivoting the armature around its pivot point apart from the yoke, the orthogonal distance between the pivot point of the armature and the elastic force of the spring is increasing from its initial value up to its maximal value.
Said spring is formed by a pair of tension helical springs, which are intended to generate each required force and corresponding torque and which extend parallel to each other, and are on the one hand connected with each other by simultaneously resting on said projection of the armature and on the other hand each per se attached to a base of the yoke.
The switch according to the invention comprises a relay with a yoke, which is formed by two plate-like parts which are separated from each other by means of said layer consisting of low-permeable material, and which are each per se cut or punched out of a plate or a strip consisting of steel or any other metallic alloy with pre-determined magnetic properties and comprises three arms, which are spaced apart from each other and protrude towards the armature, wherein their lengths are adjusted for the purposes of simultaneously abutment of said armature to all of them, wherein

the first arm is adapted to receive the coil, which is mounted on it in such a manner that said first arm extends throughout the coil and is surrounded by the winding of the coil extending along it;
the second arm is adapted to receive a permanent magnet, which permanently generates a magnetic flux and consequently a magnetic force, which is required for the purposes of abutment of the armature towards the said arms of the yoke and which is acting in a direction opposite to the force of said spring;
the third arm is intended to support the armature and to provide a pivot point, around which the armature can be pivoted from its first position of abutment towards said arms of the yoke to its second position, in which it abuts the actuating mechanism, which is located at appropriate distance apart from the yoke,

In one of possible embodiments of said switch, said permanent magnet is wedge-like shaped and is adapted for inserting into a wedge-shaped trapezoidal recess in the second arm of the yoke, which is converging away from the first arm. Besides, said armature is furnished with a projection, which is firmly connected therewith and protrudes away from the pivot point, and by which a spring is mechanically interconnected.
Said switch is further improved thanks to inserting said permanent magnet into the second arm of the yoke, by which a magnetic field is generated, which in the case, when the coil on the first arm is not energized and the armature is simultaneously abutting all three arms of the yoke, consists of

the first magnetic flux, which extends throughout the permanent magnet, the second arm of the yoke, the armature and through the first arm of the yoke towards the permanent magnet;
the second magnetic flux, which extends throughout the permanent magnet, the second arm of the yoke, the armature and through the third arm of the yoke back towards the permanent magnet; and
the third magnetic flux, which extends throughout the permanent magnet, the second arm of the yoke and through the third arm of the yoke back towards the permanent magnet,

Said permanent magnet in the relay of the switch can be designed in such a manner that upon inserting it into the area of said second arm of the yoke in the case, when the coil is not energized, the torque produced by magnetic force due to at least the first magnetic flux in the area of the first arm of the yoke with respect to the pivot point of the armature, which is simultaneously abutting all three arms, is greater than the torque produced by the force of the spring acting on the armature, while on the contrary, when the coil is energized by means of voltage produced by the passive electronic circuit and the additional fourth magnetic flux is generated, which is acting opposite to at least the first magnetic flux of the permanent magnet in the first arm, the torque produced by magnetic forces is reduced below the value of the torque produced by the force of the spring acting to the armature.
Moreover, the ratio between the first magnetic flux and the third magnetic flux in the relay of the switch is determined in advance by means of defining the shape and dimensions of the recess and/or of each permanent magnet, which is insertable therein.
Furthermore, an embodiment is also foreseen, where the primary winding of the differential transformer in the switch comprises a single turn.
On the other hand, the invention also refers to a relay, which is in particular intended to be integrated into a switch used for the purposes of interrupting an electric circuit in the case, when a difference between electric current in conductors occurs, wherein such relay in the electrical context represents a resistance and inductivity of a coil, via which the relay is electrically interconnected with a passive electronic circuit and indirectly also with a differential transformer intended for indication of a differential electric current in the area of said conductors, so that in the case of difference between currents in said conductors due to the voltage generated in the differential transformer and in the passive electronic circuit a corresponding magnetic flux is generated in said coil, and wherein such relay in the mechanical contexts consists of a yoke, which is mounted in a base and comprises said inductive coil and a permanent magnet for providing a desired magnetic flux in the area of said yoke, as well as of an armature, which is pivotally interconnected with said yoke in a pivot point and is, depending on energizing the coil, either by means of said permanent magnet rest onto said yoke, or is by means of a force of a spring pivoted away from the yoke towards the actuating mechanism , which is located at appropriate distance apart from the yoke and is intended for activation of the switch in the sense of interrupting the electric circuit through said conductors.
In accordance with the invention, the yoke consists of two plate-like and apart from each other arranged parts consisting of high-permeable ferromagnetic material, which are each per see adapted to cooperate with a permanent magnet and between which a layer is inserted, which consists of composite material with relative permeability in the range 3 ≤ µ ≤ 15, wherein the thickness of said layer amounts 0,1 to 1,0 mm.
On one of possible embodiments of such relay, said layer of composite material consists of powder particles of high-permeable material, the size of which amounts several nanometers up to several micrometers, which are interconnected by means of a binding on the basis of epoxy resins, wherein both parts of the yoke are connected to each other by means of said binding, which contain s said particles of high-permeable material. Said powder particles can consist of alloy on the basis of iron and nickel.
An accordance with a further embodiment of the invention, said relay is conceived in such manner that the position of the pivot point of rotating the armature relative to the yoke) is defined within the area between the coil and the elastic force of the spring, and simultaneously, said armature is firmly interconnected with a projection, with which each disposable spring cooperates, wherein said projection is created in such manner that by pivoting the armature around its pivot point apart from the yoke, the orthogonal distance between the pivot point of the armature and the elastic force of the spring is increasing from its initial value up to its maximal value.
Said spring can be formed by a pair of tension helical springs which are intended to generate each required force and corresponding torque and which extend parallel to each other, and are on the one hand connected with each other by simultaneously resting on said projection of the armature and on the other hand each per se attached to a base of the yoke.
Consequently, the relay according to the invention comprises a yoke, which is formed by two plate-like parts which are separated from each other by means of said layer consisting of low-permeable material, and which are each per se cut or punched out of a plate or a strip consisting of steel or any other metallic alloy with pre-determined magnetic properties and comprises three arms, which are spaced apart from each other and protrude towards the armature, wherein their lengths are adjusted for the purposes of simultaneously abutment of said armature to all of them, wherein

In one of the embodiments of the relay according to the invention, the permanent magnet is wedge-like shaped and is adapted for inserting into a wedge-shaped trapezoidal recess in the second arm of the yoke, which is converging away from the first arm. The armature is furnished with a projection which is firmly connected therewith and protrudes away from the pivot point, and by which a spring is mechanically interconnected.
Correspondingly, in such relay upon inserting said permanent magnet into the second arm of the yoke a magnetic field is generated, which in the case, when the coil on the first arm is not energized and the armature is simultaneously abutting all three arms of the yoke, consists of

In the present relay, the permanent magnet is designed in such a manner that upon inserting it into the area of said second arm of the yoke in the case, when the coil is not energized, the torque produced by magnetic force due to at least the first magnetic flux in the area of the first arm of the yoke with respect to the pivot point of the armature, which is simultaneously abutting all three arms, is greater than the torque produced by the force of the spring acting on the armature, while on the contrary, when the coil is energized by means of voltage produced by the passive electronic circuit and the fourth magnetic flux is generated, which is acting opposite to at least the first magnetic flux of the permanent magnet in the first arm, the torque produced by magnetic forces is reduced below the value of the torque produced by the force of the spring acting to the armature. In this, the ratio between the first magnetic flux and the third magnetic flux is determined in advance by means of defining the shape and dimensions of the recess and/or of each permanent magnet, which is insertable therein.
The invention will be described in more detail on the basis of an embodiment, which is presented in the accompanying drawing, wherein

Fig. 1 is a schematically shown electric switch with integrated relay according to the invention;
Fig. 2 is a relay in its opened state;
Fig. 3 is a relay in its opened state, wherein the coil is not energized; and
Fig. 4 is a relay in its closed state by energizing the coil and just prior to opening the relay i.e. prior to transition into a state according to Fig. 2.
Fig. 5 is a front view of a closed relay with integrated mechanism for pivoting of an armature for the purposes of activation of a actuating needle;
Fig. 6 is a top view of the relay according to Fig. 5;
Fig. 7 is an orthogonal left view of the relay according to Fig. 5;
Fig. 8 is an orthogonal right view of the relay according to Fig. 5;
Fig. 9 is the relay according to Fig. 8 in a cross-section along the plane IX - IX;
Fig. 10 is the relay according to Fig. 8 in a cross-section along the plane IX - IX in its opened state; and
Fig. 11 is a schematically shown two-part yoke of an improved relay according to the invention and in accordance with Figs. 2 - 10;

An electric switch is schematically shown in Fig. 1, which is intended for interruption of an electric circuit as soon as differential current would occur between a phase conductor P and a neutral conductor N, which can e.g. arise due to mechanical damage of at least one of said conductors N, P, or also due to corrosion e.g. in junctions where said conductors N, P are connected.
Said switch S can be integrated into each electric circuit together with at least one load 4 and essentially consists of a differential transformer 1, a passive electric circuit 2 and a relay 3 according to the invention. Said differential transformer 1 consists of a primary winding N1, which is formed by a neutral conductor N and the phase conductor P which extend throughout a core, as well as by a secondary winding N2, which is by means of its connectors 11, 12 electrically interconnected with connectors 21', 22' of said passive electronic circuit 2, which comprises a still further pair of connectors 21", 22", with which the relay 3 according to the invention is electrically interconnected by means of its connectors 30', 30".
In the shown embodiment, the passive electronic circuit 2 comprises two parallel connected diodes D₁ and D₂, a capacitor C_p which is parallel connected therewith, and a further capacitor C_s, which is serial interconnected with said diodes D₁, D₂ and the previously mentioned capacitor C_p.
In the context of the previously mentioned electric circuit, said relay 3 is formed by serial interconnected coil L_R and resistance R_R, while its mechanical concept and the operation will be detailed described later-on.
As soon as the switch S is integrated into a desired electric circuit, and the conductors N, P extending through the core are supplied with the electric voltage, during the regular operation the electric current in the neutral conductor N should generally be equal to the electric current in the phase conductor P. Whenever an irregularity appears, e.g. due to damage on at least one of said conductors N or P, the difference between said electric currents in both conductors N, P and consequently also in the primary winding N1 of the differential transformer 1, where the number of turns is 1, so that the voltage is induced in the secondary winding N2 of said differential transformer 1, to which then the passive electronic circuit 2 is exposed, which is electrically interconnected with said secondary winding N2. This leads to energizing of the capacitor C_s of the passive electronic circuit 2, which is re-polarized during the next semi-period of differences between the electric current in the phase conductor P and the neutral conductor N, which results in a correspondingly strong current impulse through the coil L_R of the relay 3, by which in such situation the actuating mechanism 5 is triggered (Fig. 2), by means of which then the switch S is deactivated (Fig. 1) and the electric circuit through the conductors N. P is interrupted.
As mentioned, the primary winding N1 of said differential transformer 1 consists of a single turn. On such a basis, the sensibility of the relay 3 is essentially improved, since in such single turn in the primary winding N1 of the differential transformer 1 just a minor difference between the electric currents in the conductors N and P is then able to induce in the secondary winding N2 a sufficiently high electric voltage for the purposes of generating an impulse in said passive electronic circuit 2, by which the relay 3 can then be actuated.
As mentioned, in the context of electricity, said relay 3 requires just a conductivity and resistance R_R of the coil L_R. Said coil L_R having the resistance R_R is electrically interconnected with the passive electronic circuit 2, in which a voltage impulse is generated under certain conditions, namely when differential electric current in the conductors N, P would occur, by which a magnetic field i.e. the magnetic flux Φ₁ (Fig. 4) would be generated within the coil L_R.
A mechanical concept of the relay 3 is shown in Figs. 2 - 10. In this (Figs. 2 - 4), the relay 3 essentially consists of a yoke 31, on which said inductive coil L_R is placed and via its connectors 30', 30" electrically interconnected with the said passive electronic circuit 2, and furthermore of a permanent magnet 32 as well as of an armature 33, which is pivotally around a pivot point 333 attached to said yoke 31 and by means of at least one spring 34, in this particular case by means of a pair of tension springs 34', 34", pivotable at least in the area between said yoke 31 and the actuating mechanism 5, which is located at appropriate distance apart from said yoke 31 and is intended for mechanical actuating the switch S for the purposes of interrupting the electric circuit through the conductors N, P.
The yoke 31 consists of two parts 31', 31", each of them is uniformly conceived and is made of a plate consisting of steel or any other metallic alloy having pre-determined magnetic properties, and may be quite precisely manufactured by means of cutting or punching the plate or a strip consisting of previously mentioned material, which may lead to essential benefits in particularly in the mass production. Both parts 31', 31" are separated from each other by means of a layer 310 consisting of material having low permeability. In this, the previously mentioned yoke 31 comprises three arms 311, 312, 313, which are spaced apart from each other and all protrude in the same direction towards the armature 33 and are moreover with respect to their length adapted for simultaneously abutting the armature, wherein the first arm 311 is adapted to receive said coil L_R, the second arm 312 is adapted to receive a permanent magnet 32, and the third arm 313 is adapted for establishing a required interconnection between the yoke 31 and the armature 33 at least in the previously mentioned pivot point 333.
The coil L_R is placed on the first arm 311 of the yoke 31 such that the first arm 311 extends throughout the passage within the coil L_R and is therefore surrounded by the winding of the coil L_R extending along it.
In order to enable mounting of a permanent magnet 32, said second arm 312 is furnished with a wedge-like trapezoidal recess 3121, which converges in a direction apart from the first arm 311 and into which said permanent magnet 32 is then inserted. Said magnet 32 is maintained within said recess due to its own magnetism, and is therefore upon insertion and without any other supplemental interconnection with the yoke 31 thanks to the previously described shape of the recess 3121 positioned in a quite satisfactory manner.
The third arm 313 is essentially intended to support the armature 33 and comprises a pivot point 333, around which the armature 33 can be pivoted relatively to the yoke 31 at least in the area between its first position of simultaneous abutment towards all three arms 311, 312, 313 of the yoke 31 and its second position of abutment the actuating mechanism 5, which is located at appropriate distance apart from the yoke 31 (Fig. 2) and apart from the pivot point 33, and is adapted to interrupt the electric through the conductors N, P whenever appropriate, and in particular when the differential electric current occurs.
The armature 33 is generally uniformly conceived and is made of a plate or a strip or a wire or any other rolled semi-product of a hot or cold formed preform consisting of steel or any other metallic alloy having pre-determined magnetic properties, and is moreover adapted for simultaneously abutment towards all three arms 311, 312, 313 of the yoke 31, wherein the pivot point 333, around which the armature 33 is allowed to swivel relatively to the yoke 31, is arranged on the third arm 313 of the yoke 31. By taking into consideration said pivot point 333, the armature 33 comprises two areas 331, 332, namely the first area 331 which is adapted to be rest on said three arms 311, 312, 313 of the yoke 31, and the second area 332 in the form of a cantilever protruding apart from the third arm 313 of the yoke 31. A t least one tension spring 34, 34', 34" is mechanically interconnected with the armature 33 in said second area 332 thereof in order to generate a permanent force due to tendency of rotating the armature 33 apart from the yoke 31 i.e. towards the actuating mechanism 5. For the purposes of attachment of said spring 34, 34', 34", the armature 33 is optionally furnished with a further appropriately rigid cantilever protrusion 3321, optionally in the form of a protrusion 330 attached to the armature 33 (Figs. 5 - 10), which is located on said second area 332. Consequently, the lever between the pivot point 333 of the armature 33 and the force of the spring 34 can be additionally extended and adjusted to each required conditions.
When the coil L_R is via both connectors 30', 30" electrically interconnected with said passive electronic circuit 2, and the permanent magnet 32 is inserted within the recess 3121, the armature 33 can be pivoted around the pivot point in order to assure simultaneous abutment thereof towards all three arms 311, 312, 313 of the yoke 31.
As shown in Fig. 3, the permanent magnet 32 generates a first magnetic flux Φ₁ throughout the magnet 32, the second area 312, the armature 33 and the first arm 311 of the yoke 31, and also a second magnetic flux Φ₂ throughout the permanent magnet 32, the second arm 312, the armature 32 and the third arm 313 of the yoke 31. In such a state of the relay 3, the coil L_R is not energized by the voltage of the passive electronic circuit 2, and the armature 33 is pressed towards the arms 311, 312, 313 of the yoke 31 by means of the force resulting from said magnetic flux Φ₁, Φ₂ and acting opposite with respect to said force of the tension spring 34, 34', 34". The majority of torque, by which the armature 33 is pressed towards the yoke 31, results from the force, which is generated by the first magnetic flux Φ₁ through the first arm 311 of the yoke 31 and which is located at larger distance apart from the pivot point 333. Said torque results from the magnetic forces, by which, depending on the density of the magnetic field of the permanent magnet 32 and/or the coil L_R, the yoke 31 adheres the armature 33 in the area of its arms 311, 312, 313, and can be therefore appropriately adjusted among others also by means of determining each desired cross-sections of the arms 311, 312, 313 of the yoke 31.
The ratio between the first magnetic flux Φ₁ and the third magnetic flux Φ₃ can be determined in advance by means of defining appropriate shape and dimensions of the recess 3121 and/or of the permanent magnet 32, which is insertable therein.
As soon as differential current occurs in the conductors N, P, voltage is generated on the connectors 30', 30" thanks to the differential transformer 1 and the passive electronic circuit 2, which has already been described, so that the magnetic field i.e. the fourth magnetic flux Φ₄ is generated within the coil L_R, which is acting opposite to the previously mentioned first magnetic flux Φ₁ of the permanent magnet 32 extending through the first and the second arm 311, 312 of the yoke 31. Consequently, the magnetic force generated by the first magnetic flux Φ₁ of the permanent magnet 32 is herewith eliminated, and the torque adhering the armature 33 towards the yoke 31 is reduced below the value of the torque, by which the force of the tension spring 34, 34', 34" insists in rotating the armature 33 around the pivot point 333 in a direction apart from the yoke 31 i.e. towards the actuating mechanism 5. In such situation, due to energizing the coil L_R and thanks to the fourth magnetic flux Φ₄ generated therein, the armature 33 is swiveled around the pivot point 333 into a position according to Fig. 2 in order to abut the actuating mechanism, upon which the electric circuit through the conductors N, P is interrupted by the switch S, wherein the third magnetic flux Φ₃ still persists through the permanent magnet 32, the second arm 312 and the third arm 313 of the yoke 31 (Fig. 1). The switch S, which is during the regular operation of the electric circuit through the conductors N, P closed, is in Fig. 1 merely for illustrative purposes shown in its opened state upon interrupting said electric circuit, which essentially corresponds to the position of the armature 33 as soon as said armature 33 abuts the actuating mechanism 5.
Thanks to described mechanical concept of the relay 3 and in particular of its yoke 31, such relay 3 can be despite to quite simple manufacturing technology manufactured in an extremely precise manner within each pre-determined range of dimensions, which is of a crucial importance with respect to magnetic properties, which are required for the purposes of reliable operation thereof, wherein due to improved sensibility and reactivity of the relay 3 in the case of differential current also the reliability of the complete switch S, in which it is integrated together with each corresponding conductors N, P, in comparison with the existing switches may be essentially improved.
In accordance with one of the embodiments of the invention, the armature 33 is supported on the yoke 31 in a pivot point 333 on the third arm 313, which is located at maximal distance apart from the coil L_R. The armature 33 is furnished with a projection 330, by which actually a cantilever portion 332 and the extension 3321 are replaced and which is adapted for clamping i.e. resting the spring 34, 34', 34" which is used for pressing the armature 33 towards the yoke 31, or respectively for pivoting the armature 33 apart from the yoke 31. With respect to said pivot point 333, the projection 330 of the armature 33 is created in such manner that on the one hand by resting the armature 33 on the yoke 31 (Fig. 9) an orthogonal distance Δ₁ between the elastic force of the spring 34, 34', 34" and the pivot point 333 of the armature 33 is relatively short, but on the other hand, as soon the armature 33 starts pivoting apart from the yoke 31, said distance starts increasing up to its final value Δ₂, which is essentially longer than said initial distance Δ₁. Consequently, the torque produced by acting of the elastic force of the spring 34, 34', 34" towards the armature 33 is permanently increasing, when the armature 33 is pivoted in a direction apart from the yoke 31.
This means however on the one hand, that the torque, which is generated by the elastic force of the spring 34, 34', 34" and the belonging lever Δ₁, when in the closed state of the relay 3 the armature 33 is resting on the yoke 31, is relatively small, so that initial pivoting of the armature 33 in a direction apart from the yoke 31 can be performed by means of relatively weak magnetic field. Later-on, during the pivoting of the armature 33, the lever of the elastic force of the spring 34, 34', 34" is increased from the value Δ₁ to Δ₂., by which also the torque produced by the elastic force of spring 34, 34', 34". Consequently, pivoting of the armature 33 is then quicker, and in addition to that, the impact of the armature 33 towards the actuating mechanism is correspondingly stronger. Those skilled in the art shall no doubt understand that interrupting of each circuit by means of the relay is much quicker, and on the other hand also reliability of actuating mechanism 5 is much higher.
Moreover, thanks to such concept of the relay and also of a switch S comprising such relay 3, the orthogonal distance between the pivot point 333 of the armature 33 and the elastic force of the spring 34, 34', 34" is essentially shorter, when compared with the state of the art switches or relays, and consequently, the magnetic force of the permanent magnet 32 can be reduced, and consequently, also the power of the coil L_R as required for actuating, can be essentially reduced.
An embodiment according to Figs. 5 to 10 proposes a pair of tension helical springs 34', 34" which are intended for generating each required force and corresponding torque and which extend parallel to each other and are on the one hand connected with each other by simultaneously resting on said projection 330 of the armature 33, and on the other hand each per se attached to a base 35 of the yoke 31 of the relay 3.
The previously exposed problem is however essentially solved by means of improved concept of the yoke 31 of the relay 3. In accordance with the invention, the yoke 31 consists of two plate-like and apart from each other arranged parts 31', 31" consisting of high-permeable ferromagnetic material, which are each per see adapted to cooperate with a permanent magnet 32 and between which a layer 310 is inserted, which consists of a composite material with relative permeability in the range 3 ≤ µ ≤ 15, wherein the thickness of said layer 310 is 0,1 to 1,0 mm.
Said composite layer 310 is preferably formed of powder particles of high-permeable material, the size of which amounts several nanometers up to several micrometers, and which preferably consist of an iron/nickel alloy, in particular of the so-called permenorm. Said particles are interconnected by means of a binding on the basis of epoxy resins, optionally araldite. The invention further provides that both parts 31', 31" of the yoke 31 are connected to each other by means of said binding, which includes said particles of high-permeable material, by which a problematic welding of parts 31', 31" of the yoke 31 is definitively avoided. Due to elimination of said welding, the probability of thermal extensions and varying the distance between both parts 31', 31" is essentially reduced, and reliability of the process of manufacturing a yoke 31 as well as of functioning of the relay and also the switch S during the use is essentially improved.
Contrary to the state of the art relays, where said air-gap is available between both parts 31', 31" of the yoke 31, and is filled exclusively by air with relative permeability equal 1, the invention provides filling said gap with a layer 310 of a low-permeable composite material, by which the distance between both parts 31', 31" can be essentially enlarged. Such measure therefore enables to avoid a very narrow area of still admissible errors in said distance between parts 31', 31", which in the state of the art relays amounts several micrometers at maximum. Those skilled in the art will no doubt understand that manufacturing and assembling of parts with accuracy ±0,1 mm is much more simple than manufacturing and assembling of parts with accuracy ±5 µm.
Functioning of the relay 3 and/or the switch S depends on magnetic characteristics, which are directly correlated with the distance between said parts 31', 31" of the yoke 31. Due to the presence of said layer 310 between both parts 31', 31", the distance between both parts 31', 31" can be essentially longer, and the influences of each potential discrepancies with regard to each theoretically optimal distance between said parts 31', 31" of the yoke 31, which in the practice can never be completely avoided, are herewith correspondingly reduced.
As a consequence, regardless to essentially simplified methods of manufacturing of the yoke 31, a distribution of distances between each two parts 31', 31 " of each finalized yokes 31 is much more concentrated, and besides, also assembling of said parts 31', 31" is simplified. In addition to improvement of reliability of the manufacturing process as such, also reliability of operating such switches S and relays 3 with integrated such improved yokes 31 is essentially improved.

Claims

Relay (3), which is in particular intended to be integrated into a switch (S) used for the purposes of interrupting an electric circuit in the case, when a difference between electric current in conductors (N, P) occurs, wherein such relay (3) in the electrical context represents a resistance (R_R) and inductivity of a coil (L_R), via which the relay (3) is electrically interconnected with a passive electronic circuit (2) and indirectly also with a differential transformer (1) intended for indication of a differential electric current in the area of said conductors (N, P), so that in the case of difference between currents in said conductors (N, P) due to the voltage generated in the differential transformer (1) and in the passive electronic circuit (2) a corresponding magnetic flux (Φ₄) is generated in said coil (L_R), and wherein such relay (3) in the mechanical contexts consists of a yoke (31), which is mounted in a base (35) and comprises said inductive coil (LR) and a permanent magnet (32) for providing a desired magnetic flux (Φ₁, Φ₂, Φ₃) in the area of said yoke (31), as well as of an armature (33), which is pivotally interconnected with said yoke (31) in a pivot point (333) and is, depending on energizing the coil (L_R), either by means of said permanent magnet (32) rest onto said yoke (31), or is by means of a force of a spring (34 34', 34") pivoted away from the yoke (31) towards the actuating mechanism (5), which is located at appropriate distance apart from the yoke (31) and is intended for activation of the switch (S) in the sense of interrupting the electric circuit through said conductors (N, P),
characterized in that the yoke (31) consists of two plate-like and apart from each other arranged parts (31', 31") consisting of high-permeable ferromagnetic material, which are each per see adapted to cooperate with a permanent magnet (32) and between which a layer (310) is inserted, which consists of composite material with relative permeability in the range 3 ≤ µ ≤ 15, wherein the thickness of said layer (310) is 0,1 to 1,0 mm.
Relay (3) according to Claim 1, characterized in that said layer (310) of composite material consists of powder particles of high-permeable material, the size of which amounts several nanometers up to several micrometers, which are interconnected by means of a binding on the basis of epoxy resins, wherein both parts (31', 31") of the yoke (31) are connected to each other by means of said binding, which contain s said particles of high-permeable material.
Relay (3) according to Claim 1 or 2, characterized in that said powder particles consist of alloy on the basis of iron and nickel.
Relay (3) according to anyone of Claims 1 to 3, characterized in that it is conceived in such manner that the position of the pivot point (333) of rotating the armature (33) relative to the yoke (31) is defined within the area between the coil (L_R) and the elastic force of the spring (34, 34', 34"), and in that said armature (33) is firmly interconnected with a projection (330), with which each disposable spring (34, 34', 34") cooperates, wherein said projection (330) is created in such manner that by pivoting the armature (33) around its pivot point (333) apart from the yoke (31), the orthogonal distance (Δ₁, Δ₂,) between the pivot point (333) of the armature (33) and the elastic force of the spring (34, 34', 34") is increasing from its initial value (Δ₁) up to its maximal value (Δ₂).
Relay (3) according to Claim 4, characterized in that said spring (34, 34', 34") is formed by a pair of tension helical springs (34', 34") which are intended to generate each required force and corresponding torque and which extend parallel to each other, and are on the one hand connected with each other by simultaneously resting on said projection (330) of the armature (33) and on the other hand each per se attached to a base (35) of the yoke (31).
Relay (3) according to Claim 4 or 5, characterized in that it comprises a yoke (31) which is formed by two plate-like parts (31', 31") which are separated from each other by means of said layer (310) consisting of low-permeable material, and which are each per se cut or punched out of a plate or a strip consisting of steel or any other metallic alloy with pre-determined magnetic properties and comprises three arms (311, 312, 313), which are spaced apart from each other and protrude towards the armature (33), wherein their lengths are adjusted for the purposes of simultaneously abutment of said armature (33) to all of them, and wherein
- the first arm (311) is adapted to receive the coil (L_R), which is mounted on it in such a manner that said first arm (311) extends throughout the coil (L_R) and is surrounded by the winding of the coil (L_R) extending along it;

- the second arm (312) is adapted to receive a permanent magnet (32), which permanently generates a magnetic flux and consequently a magnetic force, which is required for the purposes of abutment of the armature (33) towards the said arms (311, 312, 313) of the yoke (31) and which is acting in a direction opposite to the force of said spring (34, 34', 34");

- the third arm (313) is intended to support the armature (33) and to provide a pivot point (333), around which the armature (33) can be pivoted from its first position of abutment towards said arms (311, 312, 313) of the yoke (31) to its second position, in which it abuts the actuating mechanism (5), which is located at appropriate distance apart from the yoke (31),
and in that the armature (33) is uniformly conceived and is made of a plate or a strip or a wire or any other rolled semi-product of a hot or cold formed preform consisting of steel or any other metallic alloy having pre-determined magnetic properties, and is in the pivot point (333) pivotally interconnected with the yoke (31) and comprises the first area (331), which is located in the one side of said pivot point (333) and is adapted for simultaneously abutment towards all three arms (311, 312, 313) of the yoke (31), as well as the second cantilevered area (332), which is located on the other side of said pivot point (333) and protrudes away from the yoke (31) and in which a spring (34, 34', 34") is mechanically connected to the armature (33).
Relay (3) according to Claim 6, characterized in that the permanent magnet (32) is wedge-like shaped and is adapted for inserting into a wedge-shaped trapezoidal recess (3121) in the second arm (312) of the yoke (31), which is converging away from the first arm (311).
Relay (3) according to Claim 6 or 7, characterized in that the armature (33) is furnished with a projection (320) which is firmly connected therewith and protrudes away from the pivot point (333), and by which a spring (34, 34', 34") is mechanically interconnected.
Relay (3) according to anyone of Claims 6 to 7, characterized in that upon inserting said permanent magnet (32) into the second arm (312) of the yoke (31) a magnetic field is generated, which in the case, when the coil (L_R) on the first arm (311) is not energized and the armature (33) is simultaneously abutting all three arms (311,312, 313) of the yoke (31), consists of
- the first magnetic flux (Φ₁), which extends throughout the permanent magnet (32), the second arm (312) of the yoke (31), the armature (33) and through the first arm (311) of the yoke (31) towards the permanent magnet (32);

- the second magnetic flux (Φ₂), which extends throughout the permanent magnet (32), the second arm (312) of the yoke (31), the armature (33) and through the third arm (311) of the yoke (31) back towards the permanent magnet (32); and

- the third magnetic flux (Φ₃), which extends throughout the permanent magnet (32), the second arm (312) of the yoke (31) and through the third arm (313) of the yoke (31) back towards the permanent magnet (32),
wherein by energizing the coil (L_R) by means of a voltage on the connectors (30'. 30") thereof an addition magnetic field is generated therein with a magnetic flux (Φ₄), which is acting in the opposite direction as the said first magnetic flux (Φ₁), by which at least the magnetic flux (Φ₁) of the permanent magnet (32) in the first arm (311) is then reduced i.e. at least essentially neutralized.
Relay (3) according to anyone of Claims 6 to 9, characterized in that the permanent magnet (32) is designed in such a manner that upon inserting it into the area of said second arm (312) of the yoke (31) in the case, when the coil (L_R) is not energized, the torque produced by magnetic force due to at least the first magnetic flux (Φ₁) in the area of the first arm (131) of the yoke (31) with respect to the pivot point (333) of the armature (32), which is simultaneously abutting all three arms (311, 312, 313), is greater than the torque produced by the force of the spring (34, 34', 34") acting on the armature (33), while on the contrary, when the coil (L_R) is energized by means of voltage produced by the passive electronic circuit (2) and the additional magnetic flux (Φ₄) is generated, which is acting opposite to at least the first magnetic flux (Φ₁) of the permanent magnet (32) in the first arm (311), the torque produced by magnetic forces is reduced below the value of the torque produced by the force of the spring (34, 34', 34") acting to the armature (33).
Relay (3) according to anyone of Claims 6 to 10, characterized in that the ratio between the first magnetic flux (Φ₁) and the third magnetic flux (Φ₃) is determined in advance by means of defining the shape and dimensions of the recess (3121) and/or of each permanent magnet (32), which is insertable therein.
Switch (S) for interruption of an electric circuit in the case of differential current, which is intended for integration into an electric circuit, which is formed by appropriate direct voltage (DC) or alternating voltage (AC) or combined (AC/DC) voltage source together with at least one load (4) as well as with a phase conductor (P) and a neutral conductor (N), which are connected to said source via the said switch (S), such switch (S) comprising
- a differential transformer (1), in which its primary winding (N1) is formed by the phase conductor (P) and the neutral conductor (P) extending through a core thereof, and its secondary winding (N2) comprises two electric connectors (11, 12);

- a passive electronic circuit (2), comprising two pairs of connectors (21', 22' and 21", 22"), between which a capacitor (C_s) is serial connected to other parallel connected components (C_p, D₁, D₂) and is adapted to be energized by means of electric voltage, which is induced in the secondary winding (N2) of the transformer (1), since said circuit (2) is by means of said connectors (21', 22') electrically interconnected with the connectors (11, 12) of said secondary winding (N2) of said transformer (1); and

- a relay (3) according to anyone of Claims 1 - 11.
Switch (S) according to Claim 12, characterized in that the primary winding (N1) of the differential transformer (1) comprises a single turn.