EP2671243B1

EP2671243B1 - Electromagnetic relay, in particular for interruption of an electric circuit in the cases of differential circuit, and a switch comprising such relay

Info

Publication number: EP2671243B1
Application number: EP11813603.5A
Authority: EP
Inventors: Mitja Koprivsek; Anton Hamler; Matija Strehar; Mitja VOZEL
Original assignee: ETI Elektroelement dd
Current assignee: ETI Elektroelement dd
Priority date: 2011-02-04
Filing date: 2011-12-14
Publication date: 2015-02-25
Anticipated expiration: 2031-12-14
Also published as: SI23651A; SI23649A; WO2012105913A1; EP2671243A1; SI23649B; SI23651B; SI23650A

Description

The invention refers to an electromagnetic relay, which is used for the purposes of interrupting an electric circuit in the case of differential current between 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 create an electromagnetic relay, in particular a relay for a switch used in interrupting of an electric circuit in the case of differential current within the conductors thereof, in which despite to essentially simplified technology used in manufacturing thereof required magnetic properties could be achieved, so that the sensibility and reactiveness of such relay even by detecting extremely low differential currents could be assured. Correspondingly, a further purpose of invention is to improve a switch, in which such relay can be 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 triggering 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 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. A triggering needle is mounted on the coil.
A magnetic field, which is thanks to said permanent magnet permanently available 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 expresses tendency of rotating the armature around the pivot point and displacing it apart from the yoke of the coil together with displacing said triggering needle, which is rest on the armature. Maintaining the armature in its previously described position must be reliable just in order to prevent undesired triggering due to mechanical influences like 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 acts opposite to the previously mentioned magnetic field, and the effectiveness of the permanent magnet is correspondingly reduced, so that the force produced by the s-pring is then stronger than the magnetic force, upon which the armature is pivoted around its the pivot point, and the needle is triggered for the purposes of interrupting the electric circuit, in which the differential current is detected.
Such concept generally enables operating of the relay, but due to such concept and due to arrangement of the yoke and the armature including its pivot point, a relatively high magnetic density of the permanent magnet is required, which then in the practice leads to a relatively high power required for the purposes of triggering such relay, and which is normally between 120 and 150 µVA, and should preferably be essentially lower.
On the other hand, such concept leads to pretty undesired acting of forces. The magnetic force is namely acting at a relatively small distance apart from the pivot point, so that a relatively strong magnetic field must be established by the permanent magnet for the purposes of producing a sufficient magnetic force, and a relatively large difference of current is then required for the purposes of reducing said magnetic force, so that such switch is correspondingly insufficiently sensitive with respect to lower current differences.
In addition to that, manufacturing of such relay is extremely complicated from quite technological point of view and is connected with high risk of providing dimensions within the ranges, which are required for the purposes of regular operation. The yoke namely consists of two parts, which are welded to each other, wherein in the welded area the magnetic properties are difficultly maintained within a very narrow range. Moreover, a thin recess of approx. 50 µm has to be assured between the first arm of the L-yoke and the first arm of the S-yoke, which is filled with a diamagnetic film, wherein the manufacturing of such recess and finalization thereof in combination with problems related to the previously mentioned weld area leads to essential risk in respect to achieving each required characteristic of the final product
The present invention refers, on the one hand, 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 is formed by appropriate direct voltage or alternating voltage or combined voltage source together with at least one load, as well as by a phase conductor and a neutral conductor, which are connected to said source via the said switch, 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 said 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, via which said relay is electrically interconnected with a passive electronic circuit and indirectly also with a differential transformer which is intended for detection 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 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 switch includes a relay comprising a yoke, which is uniformly conceived and is 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, and 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,
and wherein furthermore the armature 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 pivotally interconnected with the yoke and comprises the first area, which is located in the one side of said pivot point and is adapted for simultaneously abutment towards all three arms of the yoke, as well as the second cantilevered area, which is located on the other side of said pivot point and protrudes away from the yoke and in which a spring is mechanically connected to the armature.

In a preferred embodiment of the switch in accordance with the present invention, 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, the armature is furnished with a supplemental protrusion, which is firmly attached thereto and protrudes at least approximately perpendicularly from its cantilevered portion, so that the spring is mechanically connected therewith.
Upon inserting said permanent magnet into the second arm of the yoke in such switch according to the invention, 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,
wherein by energizing the coil by means of a voltage on the connectors thereof an addition magnetic field is generated therein with a magnetic flux, which is acting in the opposite direction as the said first magnetic flux, by which at least the first magnetic flux of the permanent magnet in the first arm is then reduced i.e. at least essentially neutralized.

Said permanent magnet in the relay of the switch according to the invention is preferably 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 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 addition, the ratio between the first magnetic flux and the third magnetic flux in said relay of the switch according to the invention can be 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 preferably provides that the primary winding of the differential transformer comprises a single turn.
On the other hand, the invention also refers to a relay, which in the electrical context represents a resistance and inductivity of a coil, via which said relay is electrically interconnected with a passive electronic circuit and indirectly also with a differential transformer which is intended for detection 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 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 relay comprises a yoke, which is uniformly conceived and is 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 arc adjusted for the purposes of simultaneously abutment of said armature to all of them, and 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 a preferred embodiment of the relay in accordance with the present invention, 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, the armature is furnished with a supplemental protrusion, which is firmly attached thereto and protrudes at least approximately perpendicularly from its cantilevered portion, so that the spring is mechanically connected therewith.
Upon inserting said permanent magnet into the second arm of the yoke in such relay according to the invention, 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 according to the invention is preferably 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 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 addition, the ratio between the first magnetic flux and the third magnetic flux in said relay according to the invention can be 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.

An electric switch is schematically shown in Fig. 1, which is intended for interruption of an electric circuit as soon as a 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 due to corrosion e.g. injunctions where said conductors N, P arc 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 the 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 connecctors 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 appear, e.g. by damaging 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, by means of which then the switch S is deactivated (Fig. 1) and the electric circuit through the conductors N. P is interrupted.
The invention provides that 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 namely 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 triggered.
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 by occuring a differential electric current in the conductors N, P, by which a magnetic field i.e. the magnetic flux Φ₁ (Fig. 4) is generated within the coil L_R.
A mechanical concept of the relay 3 is shown in Figs. 2 - 4. In this, 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 a spring 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 triggering the switch S for the purposes of interrupting the electric circuit through the conductors N, P.
The yoke 31 is according to the invention 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. 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 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 said first arm 311extends 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 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 also 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 cantilever protruding apart from the third arm 313 of the yoke 31. A tension spring 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, the armature 33 is optionally furnished with a further appropriately rigid cantilever protrusion 3321, which is located on said second area 332 and preferably extends perpendicularly with respect to the armature 33 itself, by which 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. 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 a 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 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.
The relay 3 in accordance with the previously described mechanical concept can be despite to quite simple manufacturing technology extremely precisely manufactured 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, whereas 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.

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 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) 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) is uniformly conceived and is 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 (131, 132, 133), 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 (3) to all of them, and wherein
- the first arm (131) is adapted to receive the coil (L_R), which is mounted on it in such a manner that said first arm (131) extends throughout the coil (L_R) and is surrounded by the winding of the coil (L_R) extending along it;

- the second arm (132) 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 (131, 132, 133) of the yoke (31) and which is acting in a direction opposite to the force of said spring (34);

- the third arm (133) 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 (131, 132, 133) 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 (131, 132, 133) 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) is mechanically connected to the armature (33).
Relay according to Claim 1, 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 according to Claim 1 or 2, characterized in that the armature (33) is furnished with a supplemental protrusion (3221), which is firmly attached thereto and protrudes at least approximately perpendicularly from its cantilevered portion (332), so that the spring (34) is mechanically connected therewith.
Relay according to anyone of Claims 1 - 3, 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 (131, 132, 133) 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 (131) is then reduced i.e. at least essentially neutralized.
Relay according to anyone of Claims 1 - 4, characterized in that the permanent magnet (32) is designed in such a manner that upon inserting it into the area of said second arm (132) 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 (131, 132, 133), is greater than the torque produced by the force of the spring (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 (131), the torque produced by magnetic forces is reduced below the value of the torque produced by the force of the spring (34) acting to the armature (33).
Relay according to anyone of Claims 1 - 5, 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 for interruption of an electric circuit in the case of differential current, which comprises a relay (3) according to anyone of Claims 1 - 6 and is intended for integration into an electric circuit, which 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 (N) 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).
Switch according to Claim 7, 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).
Switch according to Claim 7 or 8, characterized in that the armature (33) is furnished with a supplemental protrusion (3221), which is firmly attached thereto and protrudes at least approximately perpendicularly from its cantilevered portion (332), so that the spring (34) is mechanically connected therewith.
Switch according to anyone of Claims 7 - 9, 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 (131, 132, 133) 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 (131) is then reduced i.e. at least essentially neutralized.
Switch according to anyone of Claims 7 - 10, characterized in that the permanent magnet (32) is designed in such a manner that upon inserting it into the area of said second arm (132) 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 (131, 132, 133), is greater than the torque produced by the force of the spring (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 (131), the torque produced by magnetic forces is reduced below the value of the torque produced by the force of the spring (34) acting to the armature (33).
Switch according to anyone of Claims 7 - 11, characterized in that the primary winding (N1) of the differential transformer (1) comprises a single turn.
Switch according to anyone of Claims 7 - 12, 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.