GB2088137A - Magnetomechanical converter - Google Patents

Abstract

A magnetomechanical converter for a relay comprises an armature (5), a unit containing magnets (1, 2) for generating a magnetic field of variable intensity and means (3, 4) for varying the intensity of the generated magnetic field. An even number of magnets (1, 2) are so disposed as to create magnetic circuits which operate against one another and are closed externally of the magnets. The armature (5) is of a non-energized soft magnetic material and may be flexible or spring-urged. In other arrangements the armature is centrally pivoted. <IMAGE>

Description

SPECIFICATION Magnetomechanical converter The invention relates to a magnetomechanical converter for relays, which comprises an armature, a unit containing magnets for generating a magnetic field of variable intensity and means for varying the intensity of the generated magnetic field, wherein the armature and the generating unit are movable relatively to one another. An object of the present invention is to provide a magnetomechanical converter which ensures variable adjustment of an external circuit with great accuracy over a wide range of supply currents and voltages. It is a further object of the invention to provide a magnetomechanical converter which can operate with direct current as well as with an alternating current supply and can be used particularly for constructing power relays of high sensitivity and accuracy.

For the solution of different problems related to security, signalling, communication and many other fields relays are widely used in electrical technology. Relays are usually of two basic types, namely electromagnetic relays and polarized relays. Each of these relays constitutes a magnetomechanical converter for converting the energy of a magnetical field into mechanical energy for generating a mechanical movement.

Each relay comprises at least an armature and a unit for generating a magnetic field, wherein the armature and the generating unit are movable relatively to one another.

An electromagnetic relay comprises a pot magnet stator and an armature which is movably guided thereabout and may be coupled with a spring. The armature generally consists of softiron or of other soft magnetic material. The stator forms an electromagnet, whose energizing coil is wound on a column of the pot. At the moment when the current reaches a predetermined value, the magnetic field being generated by the coil induces the armature to move. This movement may be used to achieve a switching operation. The electromagnetic relay can be supplied by a direct current or by an alternating one. The accuracy of operating is about 20% and this value can be increased to 3% for electromagnetic relays of highest quality, i.e. for protection relays.

Protection relays, which have to be produced by very accuract processing from carefully selected materials, are relatively expensive.

If the protection relays (e.g. for protection against fire, for protection of property) have to have a high accuracy of operation, they are usually connected with electronic regulating systems. As is well-known, however, this has disadvantages, because the electronic circuits have to work together with power circuits and the junction may be in some cases too expensive.

The main characteristic of a polarized relay lies in the fact that it operates as soon as a current appears in its energizing coil. Operating will be caused by any current and not only by a current of predetermined value. The basic type of polarized relay contains a movable armature situated between the north and the south poles of a magnetic stator. Either the stator or the armature consists of an electromagnet and the other element is produced from a hard magnetic material. The electromagnet should be energized by a direct current. (A polarized relay, when supplied by an alternating current, cannot be used for protection, e.g. the electric bell represents this kind of polarized "relays.) The armature of a relay, when the relay is at a standstill rests on one of the poles.If a direct current flows through the relay, the polarity of the poles in the electromagnet will be interchanged with one another and therefore the armature will change its position, moving towards the other pole. This movement may also be used to provide switching operations. To control the current intensity at which the relay will operate a well-known possibility lies in the use of a spring. However, the accuracy of such springmoved constructions is low. If accurate control is to be achieved, the parts of the relay have to be processed with high precision and the materials for them must be carefully selected.

In the prior art a special kind of relay is known, namely the TR/S 43 type produced by the German company Siemens. This relay, which has been widely used in telegraphy, is really composed of two polarised relays. The two electromagnets are so situated that when a current is flowing through them, their north and south poles are lying against one another. The armature is to be found between the electromagnets and consists of a long flattened permanent magnet polarized parallel to the flat area. The plane of polarization lies parallel or approximately parallel to a plane containing the north and the south poles of an electromagnet.

When the relay is at a standstill and after operation the armature contacts one of the poles to decrease dispersion of the magnetic flux. The direct current flowing in the electromagnets causes the interchange of the polarity of their poles and therefore the armature will move from one pole to the other. If the dispersion of the magnetic flux were not so strong, this relay would provide very good operation, but the dispersion disturbs its operation and as a result nowadays this type of relay has almost completely fallen out of the use.

The common characteristic of the above described relays lies in the use of closed magnetic circuits for decreasing the magnetic flux dispersion to a low level. In these relays operation is ensured by energizing either the electromagnet of the stator or the armature and by the interaction between the armature and the stator. For decreasing the magnetic flux dispersion the magnetic circuits are so constructed that the magnetic field lines lie in the parts of the magnetic circuit.

A further common characteristic of the known relays and a further limit on their use follows from the unfavourable value of their resetting ratio. It is most desirable for the relay to return to the start position immediately the value of the current has decreased below the tripping value. The resetting ratio of known relays, however, never exceeds about 80%, instead of the desired 100%. Even this value of 80% can be reached only in specially constructed protection relays produced from selected materials by high accuracy processing.

Common relays are characterized by a much lower value of the resetting ratio than the above mentioned.

By using contactors, thyristors and other similar elements better operating conditions can be ensured for relays. This has disadvantages, however, because the use of circuits of different current intensities gives rise to problems, as is known. Further, the weak current unit has to be provided with an effective protection system against the disturbing influence coming from the power circuits.

An object of the invention is to provide a magnetomechanical converter for operating with high accuracy at a well-defined current value, ensuring a high value of the resetting ratio. It is desired also to create a magnetochemical converter which can give a high moment on a shaft.

The invention is based on the perception that in contrary to the known solutions the poles of the same signs of two magnets can be used for creating a very effective, sensitive magnetomechanical converter of great accuracy.

In the art there is a prejudice which dictates that in devices having at least two energized magnets the poles of the same sign should not lie opposite to one another, because this leads to a high dispersion of the magnetic flux. We propose, however, the use of at least two magnets, with the magnetic poles of the same sign lying opposite to one another with an interspace to form respective non-closed magnetic circuits operating against one another, the armature being located in this interspace. The proposed solution which is completed by at least two non-closed magnetic circuits, provides the possibility of constructing very effective switch units and relays. The armature is produced from a soft magnetic material (of high relative magnetic permeability).

A further perception is that the movement of the armature may also be caused by regulating the intensity of the magnetic field between the opposite poles. If the armature is placed near to one of the poles and the intensity of the magnetic field around the opposite pole is increased, at a defined intensity value the armature will reversely magnetized and move, under the repelling influence of the first pole and under the pulling influence of the second one, very fast to the latter.

The soft magnetic material can be magnetized any number of times with a desired frequency, and therefore the number of the position changes of the armature is practically unlimited.

According to the present invention there is provided a magnetomechanical converter comprising at least one armature, a unit containing magnets for generating a magnetic field of variable intensity, and means for varying the intensity of the generated magnetic field, the armature and the generating unit being movable relatively to one another, wherein the generating unit has an even number of magnets for producing magnetic circuits operating against one another and closed externally of the magnets, the armature being situated between the magnets and being formed of a non-energized soft magentic material having a relative magnetic permeability greater than 1.2.

The magnets of the generating unit may, for example, comprise permanent magnets, with or without energizing coil, or a soft-iron core with an energizing coil.

In a preferred embodiment of the magnetomechanical converter a resilient return member is coupled either with the armature or with the generating unit and the standstill of the resilient return member responds to the standstill of the armature.

In another preferred embodiment at least two of the magnets of the magnetomechanical converter are situated in pairs, having at least one of the poles of the same sign N, S in opposite position to one another.

For limiting the relative movement of the armature and of the generating unit a stop dog may be built in. The stop dog, which may be constructed in the form of a pole shoe, is preferably coupled with a unit for regulating its position.

The armature can be formed, for example, e.g.

from ferromagnetic or ferrimagnetic material.

In an especially preferred embodiment of the magnetomechanical converter at least two of the magnets are situated along a circular line and at least one of them is movable on the circular line.

The relative movement of the armature and of the unit for generating the magnetic field can be regulated with a high degree of accuracy: the tripping current is well-defined, highly reproducible and accurately regulable. When it is necessary, the resetting ratio can be selected either to have a predetermined value or, preferably to have a value near to 100%. By using the magnetomechanical converter of the invention a relay can be built which, after reaching the defined value of current, operates with a high accuracy, seiectively, and giving a high start moment. Using the moment a relay can be built which immediately operates as a mechanical switch unit.

In comparison with the known devices the magnetomechanical converter of the present invention is of much simpler construction and can therefore be made inexpensively. The converter can be supplied by direct as well as by alternating current of any frequency and is not sensitive to changing the space positions.

In the accompanying drawings: FIG. 1 is a diagram illustrating the basic principle of the magnetomechanical converter of the present invention; FIG. 2 shows schematically a relay equipped with a magnetomechanical converter of the present invention and with a temperature sensing element; FIG. 3 shows schematically a magnetomechanical converter for current limiting; FIG. 4 shows a time-diagram of different magnetomechanical converters; FIG. 5 shows a cross-section A-A of a magnetomechanical converter shown in FIG. 6; FIG. 6 shows schematically a magnetomechanical converter equipped with a magnetic shunt; FIG. 7 shows schematically a relay for current limiting, equipped with two symmetrical magnetic circuits; FIG. 8 shows schematically a relay equipped with two external sensing elements which are coupled in a differential circuit;; FIG. 9 shows schematically a magnetomechanical converter equipped with a permanent magnet and with a soft-iron core having an energizing coil; and FIG. 10 shows schematically a magnetomechanical converter having magnets situated along a circular line.

The basic principle of the magnetomechanical converter according to the invention will now be explained with reference to FIG. 1. Two poles 28, 29 of the same sign, marked by N, are situated oppositely to one another in a unit for generating a variable magnetic field. An armature 31 is located in a space defined between the poles 28, 29. The armature 31 lies in an initial position near to the pole 28. In this position of the converter the magnetic field consists of two parts around the poles 28, 29, and the parts are separated by an imaginary dead line 30. If the intensity of the magnetic field around the pole 29 increases, the dead line 30 will move nearer to the pole 28 and at a defined value of the intensity the armature 31 will reversely magnetized by regrouping its magnetic domain structure.The remagnetized armature will be pulled by the pole 29. The regrouping will result in an interchange of the magnetic poles of the armature 31 and consequently in generating a pull between the armature 31 and the pole 29. In this way a relative movement of the armature 31 and the poles 28, 29 can be achieved.

During the regrouping of the magnetic domain structure the dead line 30 is continually being displaced in the direction of the pole 28, and therefore the pulling influence of the pole 28 is decreasing. At a well-defined value of the field intensity the situation will occur where the repelling and pulling influences of the poles in the armature are equal. At the next moment a further change of the magnetic field intensity will cause the change of the position of the armature 31 to the pdle 29. The value of magnetic field intensity at which the change in position occurs may be defined with a high degree of accuracy.

A preferred embodiment of the magnetomechanical converter of the invention uses a resilient return member, whose standstill responds to the standstill of the moving element, e.g. of the armature 31. By using such a member the movement of the armature 31 will not occur immediately the magnetization of the armature poles is reversed. The parameters of the member should, of course, be so defined, that the movement of the armature will be caused when it is needed. The definition of the member parameters is well-known to those skilled in the art.

To achieve the basic principle described above relative movement of the armature 31 and of the magnetic poles 28, 29 is necessary. It is therefore possible also to fix the armature and move the generating unit.

The different characteristics of the operation of electromagnetic relays, polarized relays, and relays provided with a magnetomechanical converter according to the invention can be analyzed according to FIG. 4, on the basis of the corresponding time diagrams.

The time diagram of the generating current is shown in trace I. Electromagnetic relays operate in response to this current according to a time diagram shows as trace II, and polarized relays according to a time diagram shows as trace Ill. In this case the electromagnetic relay indicated the lack of current by the logical level 0 and indicates by the logical level L any value which is different from zero. The polarized relay indicates the nonnegative values of the current by the logical level L, and the negative values by the logical level 0 or conversely.

On time diagram lit would be necessary properly to show a curve being not provided through the corners. On the basis of such a curve the above discussed disadvantages of the known relays can be still better understood.

If the current value changes according to trace IV, the magnetomechanical converter of the invention operates according to trace V. The armature of the converter remains in one position up to reaching the accurate value 1, and the changed position remains up to increasing the current value to 12. The values 11 and 12 can be regulated for example by regulating the,length of a stop dog or by changing the distance between the poles.

The following examples show, by way of illustrating, some embodiments of the invention.

EXAMPLE 1 Figure 2 shows a relay for temperature regulation which uses the magnetomechanical converter of the invention. This relay comprises permanent magnets 1 and 2 provided with respective energizing coils 3 and 4. The N poles of the permanent magnets 1 and 2 are situated oppositely to one another. The energizing coils 3 and 4 are wound on corresponding soft-iron cores, corming respective pole shoes of the permanent magnet. The winding directions of the energizing coils 3 and 4 are the same, providing a very effective method of regulating the intensity of the magnetic field involving an increasing magnetic current density in one of the magnets and a decreasing magnetic current density in the other magnet. On this basis a very sensitive regulating system may be constructed.

A movable armature 5 is situated in the interspace between the N poles of the permanent magnets 1 and 2, being secured in a mounting 6.

The armature 5, which has been produced from a soft magnetic material, preferably soft iron, is of a flexibie material and it lies initialiy in a position nearer to the N pole of the permanent magnet 1.

The armature 5 is supported by a stop dog 7, whose effective length is regulatable by being provided with a screw. By increasing the intensity of the magnetic field around the permanent magnet 2 the magnetic domain structure of the armature 5 will be progressively reversely magnetized. At a defined value of the magnetic field intensity the armature 5 will start to move in the direction of the permanent magnet 2.

A series circuit is formed by the energizing coils 3 and 4, a direct current supply source 9, and a sensing element 8.

The sensing element 8 can be an element which has a resistance which is dependent on a temperature to be controlled. An increasing temperature results in a decreasing current intensity and an increasing intensity of the magnetic field of the energizing coils 3 and 4. The increased magnetic field intensity of the energizing coil 3 will cause a decrease in the magnetic field intensity of the permanent magnet 1, and at the same time the magnetic field intensity of the permanent magnet 2 will be increased by the energizing coil 4. A well-defined current value, corresponding to a well-defined temperature, the increasing magnetic field intensity around the magnet consisting of the permanent magnet 2 and of the energizing coil 4 causes regrouping of the magnetic domain structure of the armature 5.This regrouping causes a pull between the armature 5, movement of the armature being limited by the stop dog 10.

A decrease of the temperature will result in a reverse process.

By changing the position of the stop dogs 7 and 1 0 the operating points of the relay can be regulated without any difficulty.

The relay can be connected with an external circuit in known manner common way, the movement of the armature 5 providing a switching action.

EXAMPLE 2 Figure 3 shows a current limiting relay which uses an embodiment of the magnetomechanical converter according to the invention and comprises, two soft-iron cores 11, 12. On the softiron cores 11, 12 are wound energizing coils 1 3 and 14 with different numbers of turns. The energizing coils 13 and 14 have terminals 18 such that the oppositely situated poles will be of the same signs N and/or S. Between the soft-iron cores 11, 12 is situated a ferromagnetic armature 1 5 which is pivotal around a shaft 1 6 coupled with a spring 1 7. The spring 1 7 is advantageously so prestressed that the armature 1 5 touches but is not supported by the stop dog 7 of regulatable length.The energizing coils 1 3 and 14 are coupled in series with one another and with the circuit to be controlled through the terminals 1 8. By selecting a weak spring 1 7 accurate regulatability of the resetting ratio may be ensured and the spring force will be advantageously exploited.

In consequence of the different numbers of turns the intensity of the magnetic field generated by energizing coil 14 will increase more quickly than the intensity of the magnetic field generated by the energizing coil 1 3. At a defined value of the current intensity the armature 1 5 will start to move in the direction of the soft-iron core 14. This movement can be used in known manner to make a mechanical or electrical connection.

EXAMPLE 3 In the construction shown in Figures 5 and 6 the soft-iron cores 11 and 1 2 are provided with energizing coils 1 9 and 20 in a similar way as in Example 2. The energizing coils 19 and 20 have equal numbers of turns and are connected in series. Between the opposed N poles and S poles of the soft-iron cores 11 and 12 are situated an armature 22 and a magnetic shunt 21. The armature is pivotal around a shaft 16 and is supported by a spring 17. The magnetic shunt 21 comprises a semi-circular element inflected in a screwthread-like manner. The magnetic shunt can be mounted rotatably on a shaft 23 independently from the armature 22.

An external circuit can be connected in series with the energizing coils 1 9 and 20 via the terminals 1 8. In the initial position and up to a well-defined current value the magnetic shunt 21 pulls the armature 22 to itself.

At the moment the generating current reaches a well-defined value the magnetic domain structura of the magnetic shunt 21 will be regrouped and the armature 22 will change its position under the repelling power of the magnetic shunt 21. Regulation of the operating value of the magnetomechanical converter is possible by changing the measures and the position of the magnetic shunt 21. The magnetic shunt acts to screen the magnetic field of the soft-iron cores 11, 1 2 and thus ensure different power action between the units generating equal magnetic fields.

EXAMPLE 4 Figure 7 shows a current limiting relay which uses four soft-iron cores 11, 12, 111, 112 and four energizing coils 13, 14, 1 13,1 14 with pairs of different numbers of turns on the soft-iron cores. The armature 22 is pivotally mounted on a shaft 16 situated in the middle part of the magnetomechanical converter, between the softiron cores 11,12,111,1 12.Theshaft shaft supported by a weak spring 1 7 in a similar way to that described in connection with the Example 2.

The energizing coils 14 and 1 14, have an equal number of turns to one another, and the coils 1 3, 113 have an equal number of turns to one another.

In its initial position the armature 22 is supported by the spring 17 and touches the stop dog 7. An increase of the generating current supplied via the terminals 1 8 will cause a change in the position of the armature 22, which will then be supported by the stop dog 10.

EXAMPLE 5 Figure 8 shows a relay having a differential circuit, for signalizing a defined level of a parameter to be controlled, for example temperature or intensity of light. The soft-iron cores 11 and 12 have similar energizing coils 24 and 25 for generating a ground level of the magnetic field intensity, and are further provided with similar energizing coils 26 and 27 for generating a working level of the magnetic field intensity. The energizing coils 26 and 27 are connected in series with one another, with the sensing elements 8 and 81, and connected with a supply source 9 through the sensing elements 8 and 81. The armature 1 5 can move between the stops 7 and 10 under the influence of the current flowing in the energizing coils.

EXAMPLE 6 Figure 9 shows a relay for sensing a voltage level. The relay has a magnetomechanical converter comprising a permanent magnet 1 and a soft-iron core 1 2 having an energizing coil 14. The current of the energizing coil 14 will have an intensity proportional to the voltage to be controlled and at a well-defined value of the voltage the position of the armature 1 5 will be changed. In the initial position the armature 15 is supported by a stop dog 7 and is pivotal around a shaft 1 6.

EXAMPLE 7 Figure 10 shows a relay for achieving mechanical switching where a high movement is required. This relay has movable and fixed magnets situated along a circular line. The movable magnets 33, 35 can be coupled with a central shaft not shown in FIG. 10. Between the movable magnets 33, 35 and corresponding fixed magnets 34, 36 is situated an armature 31 and/or 32. The armature 31, 32 may be of regulatable position. The regrouping of the magnetic domain structure of the armature(s) 31, 32 will result in a movement of the movable magnets 33, 35 in the direction of the armature(s) and this movement can be achieved with a high moment on the shaft or along the circular line.

To summarise the main advantages of the converter according to the invention and embodiments thereof are as follows: (a) At a well-defined value of the energizing current the parts of the converter change their relative positions. This value can be regulated for tripping current as well as for returning to the initial position. The relative movement is achieved with a great sensitivity as regards the moment of reaching the values of the current, and there is the possibility of having a high moment on a shaft.

This moment can be used to achieve mechanical connecting, as well as to give a sure electrical contact.

(b) The converter renders possible the construction of simple and cheap relays. Relays of great reliability can be produced using simple, traditional technological equipment.

(c) The converter can work in a very wide domain of the parameters which includes values ranging from mA, mV up to kA, kV. The converter can be supplied by alternating current of any frequency as well as by direct current and it can be used in any space position without disturbing its operation.

(d) A relay containing the converter can be used in all practical applications where relays having special regulating units or special circuits have been previously used. For example the following applications may be mentioned: (i) As primary relays in electrical power networks, in which protection has to be achieved with a high degree of accuracy; (ii) As limit detectors in security technical units in which an accurate and reliable detection of the reaching of a limit is desired for example in mining, in the fabrication of plastics, in the chemical industry, in closed technological spaces); (iii) In protection units; (iv) In signalizing units for detecting a given number of r.p.m.; (v) As a fuse in relays of high connecting speed and accuracy; (vi) In mills for signalling unacceptable changes in the thickness of rolled sheet iron or other metal; ; (vii) On railways, for example for block-systems; (viii) In self-acting fire-extinguishers; (ix) In photometry; (x) For selecting a ball in the ball bearing industry; (xi) In protection systems for cranes; (xii) In control units for lift systems.

Claims (23)

1. A magnetomechanical converter comprising at least one armature, a unit containing magnets for generating a magnetic field of variable intensity, and means for varying the intensity of the generated magnetic field, the armature and the generating unit being movable relatively to one another, wherein the generating unit has an even number of magnets for producing magnetic circuits operating against one another and closed externally of the magnets, the armature being situated between the magnets and being formed of a non-energized soft magnetic material having a relative magnetic permeability greater than 1.2.

2. A magnetomechanical converter according to claim 1, wherein the generating unit comprises a permanent magnet.

3. A magnetomechanical converter according to claim 1 or 2, wherein the generating unit comprises a permanent magnet provided with an energizing coil.

4. A magnetomechanical converter according to any one of claims 1 to 3, wherein the generating unit comprises a soft-iron core provided with an energizing coil.

5. A magnetomechanical converter according to any one of claims 1 to 4, wherein a resilient return member is coupled with the armature or with the generating unit and the standstill of the resilient return member responds to the standstill of the coupled eiement.

6. A magnetomechanical converter according to any one of claims 1 to 5, wherein at least two of the magnets are situated in pairs, having at least one of the poles of the same sign in opposite position to one another.

7. A magnetomechanical converter according to any one of claims 1 to 5, further comprising a stop member for limiting the relative movement of the armature and of the generating unit.

8. A magnetomechanical converter according to claim 7, wherein the stop member is provided with means for regulating its position.

9. A magnetomechanical converter according to claim 7 or 8, wherein the stop member constitutes a pole shoe.

10. A magnetomechanical converter according to any one of claims 1 to 9, wherein the armature is formed of a ferromagnetic material.

11. A magnetomechanical converter according to any one of claims 1 to 9, wherein the armature is formed of a ferrimagnetic material.

12. A magnetomechanical converter according to any of claims 1 to 11, wherein the generating unit has an even number of magnets arranged in pairs and having the poles of the same sign in opposition to one another.

13. A magnetomechanical converter according to any of claims 1 to 12, wherein the generating unit has an even number of soft-iron cores provided in pairs with respective energizing coils.

1 4. A magnetomechanical converter according to claim 13, wherein the said pairs comprise respective energizing coils of different inductions.

1 5. A magnetomechanical converter according to any preceding claim, wherein the armature is flexible.

1 6. A magnetomechanical converter according to any one of claims 1 to 14, wherein the armature is rotatably mounted on a shaft.

1 7. A magnetomechanical converter according to claim 16, wherein the shaft is coupled to a tension spring.

1 8. A magnetomechanical converter according to any preceding claim, wherein the armature is coupled with a magnetic shunt.

1 9. A magnetomechanical converter according to claim 18, wherein the magnetic shunt is pivotally mounted on a shaft independent from the armature.

20. A magnetomechanical converter according to any of claims 1 to 14, wherein generating unit contains at least two magnets situated along a circular line, and at least one of them is movable on the said circular line.

21. A magnetomechanical converter according to claim 20, wherein two magnets are movable and two magnets are fixed and at laast one armature is located in the spaces between the magnets.

22. A magnetomechanical converter according to claim 20 or 21, wherein the armature is coupled with a unit for regulating its position.

23. A magnetomechanical converter substantially as herein described with reference to Figure 2, Figure 3, Figures 5 and 6, Figure 7, Figure 8, Figure 9, or Figure 10, of the accompanying drawings.