DESCRIPTION

The present invention relates to an electromagnetic coupling system for a lifter or electromagnetic plane and a method for managing failures in said system.

The invention has a preferred though non-exclusive application in the field of movement of materials in heavy industry, in particular in the field of lifting electromagnets and electromagnetic planes.

In the field of electromagnetic lifters, there are various machines, such as travelling cranes or cranes, which are intended for lifting and moving materials by means of one or more electromagnets by way of a magnetic field generated thereby .

Alternatively, the electromagnetic planes include an electromagnet which is capable of generating a magnetic field in order to maintain a component to be processed in a stable manner in contact with the plane itself (for example, by means of a milling machine) , preventing the movement thereof during the operation.

Typically, the electromagnet of those lifters or planes is provided with a plurality of windings which are excited by means of the same supply line.

The fact that those lifters move a substantial quantity of material, in the order of tons, makes them potentially dangerous for the integrity of other machines, as well as for the safety of the employees at work, who operate in the vicinity, that is to say, in the working space of the lifter itself .

In fact, when there occurs a malfunction, failure or rupture in the electromagnetic lifter which involves a lack of excitation of the electromagnet, for example, caused by incorrect handling of the lifter or the accidental striking of the electromagnet against the material which has yet to be lifted, the magnetic field which attracts the lifted material stops being generated with the resultant detachment and falling of that material into one or more zones of the working space of the lifter.

Similarly, a malfunction, a failure or rupture in an electromagnetic plane may give rise to a dangerous situation.

In fact, a sudden demagnetization of the electromagnetic plane may bring about the detachment of the component which is being processed and which is positioned on the plane itself. In the context of the safeguarding of the electromagnetic lifters, there are known systems including a plurality of sources of power supply for exciting the electromagnet .

For example, JP2004203503A describes a power supply system of an electromechanical lifter comprising both a current regulator for supplying an electromagnet with direct current and a plurality of sources of power supply with alternating current in order to provide the power supply for the above- mentioned current regulator. The plurality of sources of power supply with alternating current are connected in parallel to the power supply line of the current regulator so that, in the case of a failure at a power supply source, the electromagnet will be in each case excited by the remaining power supply sources.

However, that system does not provide for any measure for providing for any malfunctions or ruptures of the electromagnet or the respective supply line, those elements being greatly subjected to failures because of moving components of the lifter and as a result of the greater exposure to the material to be lifted.

Examples of common failures in the electromagnet are as follows :

• rupture of a connection of the winding;

• rupture of the supply line of the windings;

• loose terminal of the supply line of the windings;

• interruption of the winding;

• winding earthed and/or short circuit.

There are further known lifters with electromagnets having a plurality of windings excitable in an independent manner.

For example, JPH0933081A describes an electromagnet having a plurality of windings which are received inside a single iron core, the electromagnet being provided in such a manner that each winding can be controlled in terms of current in a manner dependent on the others .

However, that system does not address the problem of safeguarding the electromagnetic lifter if there occurs a failure in the electromagnet, and does not therefore provide a solution to that problem. JPH06227785 describes an electromagnetic coupling system wherein a system for controlling the failure is capable of increasing the energy at the side not involved in the failure, where the various lines are supplied by a single port.

The technical problem addressed by the present invention is therefore to provide an improved electromagnetic coupling system for a lifter or an electromagnetic plane, and a method for managing failures in that coupling system, which are configured to overcome all the disadvantages set out with reference to the cited prior art.

That problem is solved by means of an electromagnetic coupling system for a lifter or an electromagnetic plane and a method for managing failures in that electromagnetic coupling system in accordance with the main claims of the present patent application. Preferred embodiments of the invention are further described in the dependent claims.

The present invention is used in those electromagnetic coupling systems and/or electromagnetic transport systems which, for reasons of safety and/or continuity of operation, have to safeguard the constant operation of the electromagnet.

In particular, the system and the method according to the present invention allow the lifter or electromagnetic plane to be safeguarded in the event of failures in the electromagnet, preventing the interruption of the operation thereof and the dangerous detachment of the material, or the component being processed, which is connected thereto by means of magnetic attraction. In another embodiment, the present invention relates to those situations in which electromagnetic holders are used to lock and/or control the hazardous area safety doors, fire-safety doors, barriers and/or protection devices of the machines, etc., which are necessary to protect to the greatest possible extent humans from danger, failures, fires, machines in operation, affording access and/or evacuation of dangerous areas under given conditions.

Those electromagnets are currently constructed with a single winding, subject to the same problems described above.

For any failure in the electromagnetic holder, there is a risk of unlocking/allowing access or the introduction of a hand in moving parts with an uncontrolled risk.

In a simplified manner, the system according to the present invention is used in doors which have to remain locked in an open position and be closed in an automatic manner under given conditions (in the event of a failure in the electromagnetic holder they close without any request /reason) ; or in doors which have to remain locked in a closed position and be unlocked in an automatic manner under given conditions (in the event of a failure in the electromagnetic holder for locking the door which is usually locked "Closed" by an electromagnetic holder, it is released under abnormal conditions, allowing the exit and/or admission of person (s) in dangerous areas, etc.

In another embodiment of the invention, the system is used in guards /barriers /doors for secure zones. For example, the guard may have to be in a "Locked" position for machines in operation (access not afforded to the operator) ; or "Unlocked" for a closed machine (access afforded to the operator) . It is clear that, in the event of a failure in the locking electromagnetic holder, the barrier, door, guard, etc., are released, affording access which is not controlled to moving components, etc., in an unsafe manner and in any case not in accordance with the desired function.

The characteristics and additional advantages of the invention will be better appreciated from the detailed description of some embodiments thereof which are illustrated by way of non-limiting example in an electromagnetic coupling system for an electromagnetic lifter, with reference to the appended drawings, in which:

• Figure 1 is a schematic illustration of an embodiment of the system according to the invention;

• Figure 2 is a schematic illustration of another embodiment of the system according to the invention;

• Figure 3A is a schematic illustration of a first embodiment of the system according to the invention;

• Figure 3B is a schematic illustration of another embodiment of the system according to the invention;

• Figure 4 is a matrix for the control of the energy supplied by a control device to an electromagnet in the case of failures;

• Figure 5 is a schematic illustration of a second embodiment of the control device according to the invention;

• Figure 6 is another schematic illustration of a third embodiment of the control device according to the invention; and

• Figure 7 is another matrix for the control of the energy supplied by a control device to an electromagnet in the case of failures. With reference initially to Figure 1, an embodiment of an electromagnetic coupling system for an electromagnetic lifter, such as a bridge crane having an electromagnet, is generally designated 100.

The electromagnetic coupling system 100 comprises an electromagnet 1 which is engaged by means of a hook 2 with a winch 3 which is installed on a pulley block 4 which can slide on a guide 5, such as a beam or a track which is constituted by two parallel rails, by means of suitable wheels .

The electromagnet 1 includes two or more electrical windings 6a, 6b... which can be individually supplied by means of respective supply lines 7a, 7b, ... for the excitation of the electromagnet 1 itself.

With reference to Figure 1, the electromagnet 1 according to the invention is constructed by a single electronic element in which the electrical windings 6a, 6b... are wound on respective ferromagnetic cores.

With reference to Figure 2, wherein the coupling system for an electromagnetic lifter is generally designated 100, the electromagnet 1 according to the invention is constructed by the set of a plurality of separate electronic elements 1', 1'', 1''', 1'''', each electronic element 1', 1'', 1''', I ' ' ' ' comprising at least one electrical winding 6a, 6b... which is supplied by means of a respective supply line 7a, 7b... and which is wound on a respective ferromagnetic core. Each electronic element 1', 1'', 1''', ]_'''' therefore constitutes a portion of the electromagnet 1. Preferably, each electronic element 1', 1'', 1''', i'''' comprises at least two windings 6a, 6b which can be supplied individually by means of respective supply lines 7a, 7b.

In the different embodiments of the invention, for example, as shown in Figures 1 and 2, the electromagnetic system 100 further comprises a control device 9 which can be programmed in known manner or programmed so as to supply an energy quantity Ea, Eb to the various electrical windings 6a, 6b so that the excited electromagnet 1 generates a magnetic field with predefined operating intensity I.

The quantity of energy supplied by the control device 9 to the electromagnet 1 for generating the magnetic field with predefined operating intensity I is defined herein as the total energy ET.

In the context of the present invention, in the case of the coupling system for an electromagnetic lifter, the term "predefined operating intensity I" is intended to be understood to be the intensity of the magnetic field generated by the electromagnet 1 for which the electromagnet 1 is capable of attracting the material which is capable of magnetic attraction in order to lift it and move it towards a predetermined intended location. In the case of the coupling system for an electromagnetic plane, the term "predefined operating intensity I" is intended to be understood to be the intensity of the magnetic field generated by the electromagnet 1 for which the electromagnet 1 is capable of attracting a component to be processed in order to maintain it in a stable manner in contact with the work plane, that is to say, preventing the movement of the component during the processing thereof.

The value of the predefined operating intensity I of the magnetic field will therefore be a function of the operating conditions of the coupling system 100, such as, for example, the weight of the material to be lifted by means of the electromagnetic lifter or the stresses to which the component being processed on the electromagnetic plane is subjected.

Therefore, the quantity of energy Ea, Eb supplied by the control device 9 to the windings 6a, 6b for generating the magnetic field having predefined operating intensity I is a function of the operating conditions of the lifter 100.

As will be better explained below, the coupling system 100 comprises detection means 13 which are capable of detecting a failure involving one of the windings 6a, 6b, ... and/or one of the supply lines 7a, 7b, ...

In the present invention, the term "failure" is intended to be understood to be the establishment of an occurrence concerning a winding 6a, 6b... and/or a supply line 7a, 7b... so as to bring about a reduction in intensity of the magnetic field generated by the electromagnet 1 with respect to the predefined operating intensity I.

For example, the term "failure" is intended to be understood to be an interruption of the supply line 7a, 7b... of a winding 6a, 6b..., an interruption of the winding 6a, 6b... itself, the rupture of the connection between the terminals of the supply line 7a, 7b... and those of the winding 6a, 6b..., the rupture of the connection between the terminals of the supply line 7a, 7b... and those of the control device 9 or those of a connection line 70, or the interruption of a connection line 70 itself.

Furthermore, a failure may indicate the fact that a clamp for electrical connection between a terminal of the supply line 7a, 7b... and the terminal of the winding 6a, 6b... is loose or that a terminal of the winding 6a, 6b... is earthed, or that a short-circuit in the electromagnet 1 has been established.

With reference to Figure 3A, the control device 9 is provided to be connected by means of an input interface 10 to a supply source 11 which is intended for the supply of the windings 6a, 6b.

Preferably, the supply source 11 includes a plurality of energy sources which are mutually independent and which are connected to the input interface 10 in such a manner that a first energy source can supply energy to the control device 9 in an independent manner from a second energy source. For example, those sources may be connected in parallel to the input interface 10 so that a failure at a first energy source does not inhibit the supply of energy to the control device 9 by a second energy source.

Examples of energy sources are the electrical distribution network, accumulation systems for electrical energy, such as batteries, or machines for the production of electrical energy in situ.

The control device 9 is further provided to be connected by means of an output interface 12 to the supply lines 7a, 7b, 7c for supplying energy to the windings 6a, 6b, 6c by means of the energy supplied by the supply source 11.

The output interface 12 is therefore provided with a plurality of outlet ports, each port being provided in order to be connected to a separate supply line 7a, 7b... and/or to one or more connection lines 70, from which at least two supply lines 7a, 7b... extend in order to supply energy to the windings 6a, 6b....

In particular, the embodiment of the system 100 illustrated in Figure 3A, in which two supply lines 7a, 7b... are connected to respective mutually separate outlet ports of the output interface 12, allows a supply to the electrical windings 6a, 6b in an individual manner and independently of each other by means of the respective supply lines 7a, 7b.

In particular, a plurality of supply lines 7a, 7b... can be connected to respective mutually separate outlet ports of the output interface 12 so as to supply by means of the control device 9 the respective electrical windings 6a, 6b... in an individual manner and independently of each other.

Still with reference to Figure 3A, in a first embodiment of the invention the control device 9 is produced by an excitation unit 14 including a power unit 15 which is connected at the input to the power supply source 11 by means of the input interface 10 and at the output to the supply lines 7a, 7b... by means of the output interface 12 for the supply of energy to the windings 6a, 6b....

The power unit 15 may include a circuit for converting alternating current to direct current AC/DC, or a DC/DC conversion circuit in order to supply the windings 6a, 6b... with direct current.

A switch Q which is shown in exemplary form in Figure 6 may be interposed in the electrical line for connection between the supply source 11 and the excitation unit 14 in order to activate or to deactivate the excitation unit 14.

Furthermore, the excitation unit 14 includes a regulation unit 16 which is operatively connected to the power unit 15 and to the detection means 13 and which is capable of controlling the quantity of energy supplied by the power unit 15 to the windings 6a, 6b... which are connected thereto. Preferably, the excitation unit 14 is provided with a programming interface for loading in the store 18 of the regulation unit 16 a programme P for controlling the energy supplied by the power unit 15 to the windings 6a, 6b....

In other words, the regulation unit 16 is programmed so as to control the energy, such as power and/or current, which is supplied by the power unit 15 to the windings 6a, 6b... so that the electromagnet 1 generates a magnetic field having predefined operating intensity I.

In particular, the regulation unit 16 is programmed so as to control the occurrence of a failure which involves a winding 6a, 6b... and/or a supply line 7a, 7b, the failure being detectable by way of the detection means 13.

By way of example, the detection means 13 for a failure which involves one of the windings 6a, 6b... and/or one of the supply lines 7a, 7b... can be included in the excitation unit 14 and preferably comprise electronic sensors which are capable of detecting the value of one or more electrical magnitudes, such as current and voltage, and/or parameters relating to the operating state of the windings 6a, 6b... and/or the supply lines 7a, 7b....

The control of the occurrence of a failure by the regulation unit 16 (that is to say, by the control system 9), the construction and the operation of the detection means 13 and the detection of the above-mentioned failure will not be discussed in greater detail in the present document because they are known to the person skilled in the art.

In fact, the excitation unit 14 can be constructed by any electronic convertor which is provided with that functionality. Those devices are commonly commercially available, such as, for example, the convertor "CU400" which is produced by the company Elettronica Santerno S.p.a or the convertor "DCS800" produced by ABB.

Preferably, the nominal energy, that is to say, the power, the current or the nominal voltage, which can be supplied by the excitation unit 14 is equal to the total energy ET supplied by the control device 9 to the electromagnet 1 by the generation of the magnetic field having predefined operating intensity I.

The term "nominal energy which can be supplied by the excitation unit 14" is intended to be understood to be the energy which can be supplied by the excitation unit 14 for which the unit has been configured, constructed and tested and to which reference must be made in order to have the certainty of normal operation. The total energy ET supplied by the control device 9 to the electromagnet 1 is therefore subdivided into proportions between the windings 6a, 6b....

For example, if there are two windings 6a, 6b which are connected to the control device 9, the device can supply a first quantity of energy Ea equal to 50% of the total energy ET to the first winding 6a and a second quantity of energy Eb equal to the remaining 50% of the total energy ET to the second winding 6b.

According to a preferred embodiment of the invention, when a failure which involves a winding 6a, 6b... and/or a supply line 7a, 7b... is detected by the detection means 13, the control device 9 is capable of increasing the quantity of energy supplied to one or more windings 6a, 6b... which are not involved in that failure so as to compensate for a reduction in intensity of the magnetic field generated by the electromagnet 1 with respect to the predefined operating intensity I, that reduction being a result of the above- mentioned failure which involves a winding 6a, 6b... and/or a supply line 7a, 7b....

In other words, when a failure which involves a winding 6a, 6b... and/or a supply line 7a, 7b... is detected by the detection means 13, the control device 9 is capable of increasing the quantity of energy supplied to one or more windings 6a, 6b... which are not involved in that failure so that the intensity of the magnetic field generated by the electromagnet 1 is sufficient to ensure continuity of operation of the system 100.

The quantity of energy supplied to one or more windings 6a, 6b... not involved in the failure is increased with respect to the quantity of energy supplied thereto by the control device 9 for the generation of the magnetic field having predefined operating intensity I without any failures.

Preferably, the control device 9 is capable of increasing the quantity of energy supplied to all the windings 6a, 6b... which are not involved in that failure.

The term "winding which is involved in a failure" is intended to be understood so that the failure is established in the winding itself or in the respective supply line or connection line, that is to say, the winding is affected by or subjected to the failure. Accordingly, a winding is not involved in a failure when the winding itself, the respective supply line and the connection line do not have a failure, that is to say, the winding is not affected by or subjected to the failure.

According to another aspect of the invention, the control device 9 is programmed so as to compensate for the above- mentioned reduction in the intensity of the magnetic field for a predetermined time.

According to another aspect of the invention, the quantity of energy supplied to one or more windings 6a, 6b... not involved in the above-mentioned failure is increased so that the intensity of the magnetic field generated by the electromagnet 1 is at least equal to the predefined operating intensity I .

According to another aspect of the invention, in accordance with the specific configuration and construction characteristics of the electromagnetic system 100, the quantity of energy supplied to one or more windings 6a, 6b... not involved in the above-mentioned failure is increased so that the intensity of the magnetic field generated by the electromagnet 1 is sufficient to ensure continuity of operation of the system 100, that intensity of the magnetic field being able to be less (for example, by a predefined value) than the predefined operating intensity I. Those characteristics advantageously allow provision for a reduction in intensity of the magnetic field as a result of a failure and safeguarding of the electromagnetic coupling system 100, ensuring the continuity of operation thereof.

With reference to the coupling system for an electromagnetic lifter, that fact prevents the dangerous detachment and falling of the material being moved in one or more zones of the working space of the lifter, placing that material in a safe manner on the ground or on a suitable support surface.

For controlling the quantity of energy supplied by the control device 9 to the windings 6a, 6b... in the event of a failure which involves a winding 6a, 6b... and/or a supply line 7a, 7b..., the control device 9 provides a matrix M or an algorithm which is stored in the store 18 of the regulation unit 16.

Preferably, that supply of energy by the control device 9 to at least one winding 6a, 6b... which is not involved in the above-mentioned failure is prolonged by a predetermined time so as to ensure continuity of operation of the electromagnetic system 100. More preferably, the regulation unit 16 provides for energy not to be supplied to the winding 6a, 6b... which is subjected to the failure.

Figure 4 illustrates an example of the matrix M for an electromagnetic system 100 having two windings 6a, 6b which are supplied by respective supply lines 7a, 7b in which the control device 9 can supply a total energy ET to the electromagnet 1 for generating the magnetic field having a predefined operating intensity I.

As indicated, in the case of no failures being present, 50% of the total energy ET is supplied to the first winding 6a and the remaining 50% is supplied to the second winding 6b. If the first winding 6a is involved in a failure, the control device 9 provides for energy not to be supplied thereto and for 100% of the total energy ET to be supplied to the second winding 6b so that the electromagnet 1 continues to generate a magnetic field having predefined operating intensity I. Vice versa, if the second winding 6b is involved in a failure, the control device 9 provides for energy not to be supplied thereto and for 100% of the total energy ET to be supplied to the first winding 6a so that the electromagnet 1 continues to generate a magnetic field having predefined operating intensity I .

In an alternative embodiment of the invention to Figure 3A, illustrated here in Figure 3B, the electromagnetic coupling system 100 is provided with two supply lines 7a, 7b... which are connected to the same outlet port of the control device 9, that is to say, connected to the same outlet port of the above-mentioned output interface 12, in order to supply a quantity of energy to the respective electrical windings 6a, 6b....

In particular, more than two supply lines 7a, 7b... can be connected to the same outlet port.

In other words, the electrical windings 6a, 6b..., except for possible additional electrical components which are contained in the supply lines 7a, 7b..., are connected to each other in parallel with the control device 9.

In that case, that is to say, in the embodiment of the system 100 of Figure 3B, if a failure occurs which involves an electrical winding 6a, 6b... and/or a supply line 7a, 7b..., the quantity of energy supplied by the control device 9 to one or more electrical windings 6a, 6b... which are not involved in the failure is automatically increased so as to compensate for a reduction in intensity of the magnetic field generated by the electromagnet 1 with respect to the predefined operating intensity I, that reduction being a result of the above-mentioned failure.

The fact that the quantity of energy supplied to the windings 6a, 6b... which are not involved in the failure is automatically increased, that is to say, without the use of specific algorithms for controlling the energy supplied by the control device 9 and means for detecting failures, is a result of the specific configuration of the system 100.

In fact, with the supply lines 7a, 7b being connected to the same outlet port of the control device 9, the total energy ET supplied by the control device 9 to the electromagnet 1 is divided between the supply lines 7a, 7b in accordance with the electrical characteristics of the windings 6a, 6b.... Therefore, in the event of a failure which involves the winding 6a, such as, for example, an interruption of the respective supply line 7a, the entire quantity of energy supplied by the control device 9 will be automatically intended for the winding 6b not involved in the failure by means of the respective supply line 7b, consequently increasing the quantity of energy supplied to the winding 6b with respect to the quantity of energy supplied thereto when no failures are present.

In a second embodiment of the invention, with reference to Figures 5-6, the control device 9 comprises a plurality of above-described excitation units 14', 14'' and 14', 14'', 14''', respectively. Those excitation units 14', 14''... are provided in order to be operatively connected to each other by means of a communication channel Bl, B2.

Those excitation units 14', 14''... are operatively connected to each other by means of a communication channel Bl or Bl, B2.

Those connections between the excitation units 14', 14''... may be wired or of the wireless type.

Each excitation unit 14', 14''... can be connected at the input to the supply source 11 and at the output to the supply lines 7a, 7b... in order to supply a quantity of energy to the electrical windings 6a, 6b....

Each excitation unit 14', 14'', 14''' is connected to one or more respective windings 6a, 6b, 6c which can be individually supplied by means of respective supply lines 7a, 7b, 7c. With reference to that configuration, each excitation unit 14', 14'', 14''' is provided in order to control the energy to be supplied to the respective windings 6a, 6b, 6c so that the excited electromagnet 1 generates a magnetic field having predefined operating intensity I.

Preferably, each excitation unit 14', 14'', 14''' is capable of supplying a quantity of energy at least equal to the total energy ET to be supplied to the electromagnet 1 so that the electromagnet 1 generates an electromagnetic field having operating intensity I. Preferably, the nominal energy which can be supplied by the excitation unit 14 is equal to the total energy ET.

Preferably, the total of the energy supplied by the excitation unit 14', 14'', 14''' is equal to the above- mentioned total energy ET when the electromagnetic coupling system 100 does not have any failures.

With reference to the control of a failure by the control device 9, preferably the detection means 13 are also capable of detecting a failure, that is to say, a malfunction or rupture, of an excitation unit 14', 14'', 14''' and/or a failure, such as an interruption, in the respective electrical connection line which connects it to the supply source 11, those failures being capable of bringing about a reduction in intensity of the magnetic field generated by the electromagnet 1 with respect to the predefined operating intensity I .

The control of the occurrence of a failure detected by the detection means 13 can be carried out by the control device 9 by means of one or more of the regulation units 16 of the excitation units 14', 14'', 14'''.

By way of example, Figure 6 is a functional diagram of an electromagnetic coupling system 100 according to the invention, wherein that system 100 includes three excitation units 14', 14'', 14''' which are each connected to a different winding 6a, 6b, 6c of the electromagnet 1 by means of respective supply lines 7a, 7b, 7c.

With reference to Figure 7, without any failures the quantity of energy supplied by each excitation unit 14', 14'', 14''' is equal to a third of the total energy ET supplied by the control device 9 to the electromagnet 1.

If a failure is detected by the detection means 13, the regulation units 16 of the excitation units 14', 14'', 14''' provide for an increase in the quantity of energy supplied to the respective windings 6a, 6b, 6c which are not involved in that failure so as to compensate for the reduction in the intensity of the magnetic field generated by the electromagnet 1 with respect to the predefined operating intensity I .

Preferably, that energy supply is based on the above- mentioned matrix M, or algorithm, which is stored in the control device 9 and is prolonged for a predetermined time so as to ensure continuity of operation of the electromagnetic system 100.

The term "winding which is involved in a failure" is intended to be understood to mean that the failure is established in the winding itself, in the respective supply line or connection line, in the respective excitation unit 14', 14'', 14''' or in the electrical connection line thereof with respect to the supply source 11, that is to say, the winding is affected by or subjected to the failure. Consistently, a winding is not involved in a failure when the winding itself, the respective supply line or the connection line, the respective excitation unit 14', 14'', 14''' and the above- mentioned electrical connection line do not have a failure, that is to say, the winding is not affected by or subjected to the failure.

Figure 7 illustrates an example of a matrix M for a system 100 having three excitation units 14', 14'', 14''' which are operatively connected to each other. Each excitation unit 14', 14'', 14''' is provided so as to supply a quantity of energy El, E2, E3 to a respective winding 6a, 6b, 6c by means of a respective supply line 7a, 7b, 7c in such a manner that the control device 9 supplies a total energy ET to the electromagnet 1 for generating the magnetic field having predefined operating intensity I.

Each excitation unit 14', 14'', 14''' is further capable of supplying a quantity of energy equal to the above-mentioned total energy ET.

As indicated, in the case of failures not being present, the first, second and third excitation units 14', 14'', 14''' each supply a quantity of energy El, E2, E3 equal to 33% of the total energy ET to the first winding 6a, the second winding 6b and the third winding 6c, respectively.

When the first winding 6a is involved in a failure, the control device 9 provides for energy not to be supplied to that winding, for a quantity of energy Eb equal to 50% of the total energy ET to be supplied to the second winding 6b and for a quantity of energy Ec equal to the remaining 50% of the total energy ET to be supplied to the third winding 6c so that the electromagnet 1 continues to generate a magnetic field having predefined operating intensity I.

Vice versa, when the second winding 6b is involved in a failure, the control device 9 provides for energy not to be supplied to that winding, for a quantity of energy Ea equal to 50% of the total energy ET to be supplied to the first winding 6a and for a quantity of energy Ec equal to 50% of the total energy ET to be supplied to the third winding 6c so that the electromagnet 1 continues to generate a magnetic field having predefined operating intensity I.

In an embodiment of the invention, the system 100 is produced so that the nominal excitation energy of the windings 6a, 6b, 6c is less than the quantity of energy which can be supplied thereto by the control device 9 for generating a magnetic field having predefined operating intensity I if a failure is detected by the detection means 13.

In that case, one or more windings 6a, 6b, 6c which are not involved in that failure are supplied by a quantity of energy greater than the nominal excitation energy thereof which, therefore, leads to an over-supply for those windings with respect to the nominal excitation energy thereof, overheating them .

However, a suitable configuration of the system 100 will allow the supply of energy of the device 9 to those windings to be extended for a predetermined time so that it is possible to position the system 100 in a safe manner and in such a manner as to safeguard the electrical integrity of those windings, preventing damage thereto.

That construction advantageously allows the dimensions, the weight and the costs of the electromagnet 1 to be contained.

That solution is particularly suitable for high-power electromagnetic lifters or electromagnetic planes which are themselves owing to the construction particularly not subject to an over-supply of the windings.

It will be appreciated that the electromagnetic system according to the invention is capable of automatically controlling the supply of the electromagnet if a failure is established, thereby ensuring the excitation of the electromagnet for continuity of operation of the system itself .

It will further be appreciated that the electromagnetic coupling system to which the invention relates produces a system of redundancy of the supply for the electromagnet so as to ensure the excitation thereof in the event of failures.

Thus, the invention achieves the results set out by providing a number of advantages, including the fact that it is possible to safely position the material moved by an electromagnetic lifter in the event of a failure (in particular in the case of failures in the windings of the electromagnet or the respective supply lines), or for the detachment of the component which is being processed and which is positioned on an electromagnetic plane to be prevented .