DESC:TECHNICAL FIELD
[0001] The present disclosure relates generally to any electrical switching device, and more particularly to an electromagnetically operated switching device such as a contactor, starter, among others that can be used for switching of lighting, heating, and capacitive loads.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] The present disclosure relates to switchgears, and more particularly to electromagnetically actuated circuit controlling devices such as contactors. European patent application 376 493 describes a control circuit that allows high current during the pick-up phase, which high current is then reduced to holding current after the closing operation. German patent no. 30 47 488 A1, on the other hand, describes, in addition to a coil current controller, a Hall probe that is arranged in the yoke. One of the existing methods use fixed timing during the pick up pulse duration, which consumes higher energy as the energy supplied is unregulated and independent of the actual position of the electromagnet. Another method regulates the pick up pulse duration by sensing the contact closing instant. Sensing the contact closing instant is a challenge and is often inaccurate due to arcing taking place between the contacts. Similarly, sensing the magnet closing instant can also be done for controlling the pick up pulse duration. However, this method requires modification of the electromagnet system and placement of hall sensor for tracing magnet movements.
[0004] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0005] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0006] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0007] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0008] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE PRESENT INVENTION
[0009] It is an object of the present disclosure to provide a method of controlling excitation given to an electromagnet with the help of input current feedback mechanism.
[0010] It is an object of the present disclosure to provide a coil-based actuator for medium and low voltage applications that can be easily adapted to a wide number of intended applications.
[0011] It is an object of the present disclosure to provide a coil-based actuator for medium and low voltage applications having a simplified design, maintaining at the same time the performances and the reliability needed for the intended applications.
[0012] It is an object of the present disclosure to provide a control system for medium and low voltage applications that can cover broad operational ranges, in terms of voltages and currents.
[0013] It is another object of the present disclosure to provide a control system for medium and low voltage applications that is protected against over-voltages and over-currents.
[0014] It is another object of the present disclosure to provide a control system for medium an low voltage applications in which the integrity and continuity of the coil and the associated driving electronics can be detected and checked.
[0015] It is another object of the present disclosure to provide a control system for medium and low voltage applications with reduced manufacturing and installation costs.
[0016] It is an object of the present disclosure to provide an improved electromagnetically actuated circuit controlling device that reduces contact bounce and lengthens lifespan of a switching device.

SUMMARY
[0017] The present disclosure relates generally to any electrical switching device, and more particularly to an electromagnetically operated switching device such as a contactor, starter, among others that can be used for switching of lighting, heating, and capacitive loads.
[0018] In an aspect, the present disclosure provides a control system for controlling voltage fed to coil of an electromagnetic contactor, wherein the control system can include a bridge rectifier that is configured to receive AC/DC control supply, wherein the bridge rectifier converts the supply to DC input, a PWM module that is operatively coupled to the bridge rectifier and configured to chop down the DC input, wherein the chopped down DC input is fed into the coil of the electromagnetic contactor.
[0019] The control system can further include a microcontroller that can be configured to generate a control signal for the PWM module, wherein the control signal can be varied by the microcontroller based on input from a current sensor that is configured to sense the DC input received from the bridge rectifier for being fed to the electromagnetic coil.
[0020] In another aspect, based on the input from the current sensor, the microcontroller can decide duty ratio of PWM supplied to the PWM module, and wherein the duty ratio can form part of the control signal. In yet another aspect, the duty ratio can be adjusted by varying frequency or time of PWM signal to keep voltage across the electromagnetic coil constant with respect to signature of the DC input fed into the coil.
[0021] In another aspect, based on the input from the current sensor, the microcontroller can decide timing of PWM supplied to the PWM module, wherein the timing can form part of the control signal.
[0022] In yet another aspect, when current profile the coil starts raising again, voltage across the coil can be reduced to a predefined hold-on voltage to keep the contactor in hold-on position.
[0023] Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learnt by practice of the invention. The aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0025] FIG. 1 shows an exemplary block diagram of an electronic coil drive that is used for controlling voltage fed to coil of an electromagnetic contactor in accordance with an embodiment of the present disclosure.
[0026] FIG. 2 shows an exemplary waveform of current drawn by the coil during the closing phase of the electromagnetic accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0027] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0028] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0029] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0030] The present disclosure provides an improved electromagnetically actuated circuit controlling device which, in comparison to prior art devices, substantially reduces contact bounce and lengthens the lifespan of the contactor.
[0031] FIG. 1 shows an exemplary block diagram 100 of an electronic coil drive that can be used for controlling voltage fed to coil of an electromagnetic contactor in accordance with an embodiment of the present disclosure. FIG. 1 illustrates AC/DC control supply 102 that can be fed to a bridge rectifier 104, which converts the signal into DC. The DC input can then be chopped down using a PWM module 106, and then be fed into an electromagnetic coil 108. In an aspect, control signal for the PWM module 106 can be generated by a microcontroller 110, which can vary its output on the basis of input from the current sensor 112 that is configured to sense the DC input current to the electromagnetic coil 108. According to one embodiment, based on the feedback signal from the current sensor 112, the microcontroller 110 can decide the duty ratio of the pulse-width modulation (PWM) supplied to the PWM module 106. The duty ratio can be adjusted either by varying the frequency or the time of the PWM signal to keep the voltage across the coil 108 constant with respect to the signature of the coil input current.
[0032] FIG. 2 depicts the relationship among the coil excitation current profile 202, contact closing 204, and magnet closing during the closing movement of the switching device. When the coil supply voltage 206 is given, the excitation current 202 starts to increase. The movable armature starts moving as soon as it gains sufficient ampere-turns to make the closing movement. This reduces the air gap thereby increasing the inductance of the electromagnetic system. Therefore, the excitation current starts to decrease until the end of the travel distance of the movable armature i.e. magnet closing. After this moment, the air gap and the inductance no longer vary and the excitation current increases again.
[0033] In an aspect, method and control circuit relate to a contactor with DC excitation or AC excitation, which can then be converted into DC internally and fed to the coil. By giving DC to the coil, movable contact of the contactor can be pulled at a high velocity to make contact with the stationary contact. When the contacts mate, the movable contact tends to bounce due to high velocity of the movable contact at which it strikes the fixed contact. The bouncing in turn leads to more arcing, which causes much wear and tear in the contacts and reduces the lifetime of the contactor. The contact velocity can then be controlled based on the signature of coil input current during the electromagnet closing movement. In order to optimize the switching function, an intelligent contactor with current feedback system is considered. In the pick-up process, the coil voltage is unchanged until the input current reaches its peak. Once the current profile starts drooping, it is understood that the moving contact starts moving towards fixed contact at great velocity. At that time, duty cycle of the PWM module is adjusted and the voltage that appears across the coil is reduced at phases. Consequently, second bounce of the contacts when moving magnet makes contact with fixed magnet also reduced greatly.
[0034] The method is depicted in the above block diagram of FIG. 1, where the rectified AC input is fed to the coil through a PWM modulator 106. The PWM modulator 106 is controlled by microcontroller 110, which receives the feedback from the input current sensor 112, and decides the duty ratio and the associated timing. In an aspect, the microcontroller110 can include a re-writable non-volatile area that can be used to store parameters and this area can be used to store the switching threshold. Consequently, with the help of the feedback system, the intelligent contactor can greatly reduce the kinetic energy of the contactor’s movable parts during its pick-up process, thereby reducing contact erosion and extending the contact life. When the current profile starts raising again, voltage across the coil is reduced to a predefined hold-on voltage required enough to keep the contactor in hold-on position, thereby reducing the energy consumption of the contactor at right instant.
[0035] In an aspect, the present method and architecture optimizes energy supplied to the magnet during the pick-up phase of the contactor. Furthermore, voltage across the coil can be adjusted according to the coil excitation current signature through PWM. Furthermore, impact on the magnet system during pick-up can considerably be reduced.
[0036] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
[0037] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claim.
[0038] In the foregoing description, numerous details are set forth. It will be apparent, however, to one of ordinary skill in the art having the benefit of this disclosure, that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, to avoid obscuring the present invention.
[0039] Some portions of the detailed description have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
[0040] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “computing”, “comparing”, “determining”, “adjusting”, “applying”, “creating”, “ranking,” “classifying,” or the like, refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
[0041] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should therefore be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

ADVANTAGES OF THE PRESENT INVENTION
[0042] The present disclosure provides a method of controlling excitation given to an electromagnet with the help of input current feedback mechanism.
[0043] The present disclosure provides a coil-based actuator for medium and low voltage applications that can be easily adapted to a wide number of intended applications.
[0044] The present disclosure provides a coil-based actuator for medium and low voltage applications having a simplified design, maintaining at the same time the performances and the reliability needed for the intended applications.
[0045] The present disclosure provides a control system for medium and low voltage applications that can cover broad operational ranges, in terms of voltages and currents.
[0046] The present disclosure provides a control system for medium and low voltage applications that is protected against over-voltages and over-currents.
[0047] The present disclosure provides a control system for medium an low voltage applications in which the integrity and continuity of the coil and the associated driving electronics can be detected and checked.
[0048] The present disclosure provides a control system for medium and low voltage applications with reduced manufacturing and installation costs.
[0049] The present disclosure provides an improved electromagnetically actuated circuit controlling device that reduces contact bounce and lengthens lifespan of a switching device.
,CLAIMS:1. A control system (100) for controlling voltage fed to coil (108) of an electromagnetic contactor, said control system comprising:
a bridge rectifier (104) that is configured to receive AC/DC control supply (102), wherein the bridge rectifier (104) converts said supply to DC input;
a PWM module (106) operatively coupled to the bridge rectifier (104) and configured to chop down the DC input, wherein the chopped down DC input is fed into the coil (108) of the electromagnetic contactor;
a microcontroller (110) that is configured to generate a control signal for the PWM module (106), wherein the control signal is varied by the microcontroller (110) based on input from a current sensor (112)that is configured to sense the DC input received from the bridge rectifier (104) for being fed to the electromagnetic coil (108).

2. The control system (100) of claim 1, wherein based on the input from the current sensor (112), the microcontroller (110) decides duty ratio of PWM supplied to the PWM module (106), and wherein said duty ratio forms part of the control signal.

3. The control system (100) of claim 2, wherein the duty ratio is adjusted varying frequency or time of PWM signal to keep voltage across the electromagnetic coil (108) constant with respect to signature of the DC input fed into the coil (108).

4. The control system (100) of claim 1, wherein based on the input from the current sensor (112), the microcontroller (110) decides timing of PWM supplied to the PWM module (106), and wherein said timing forms part of the control signal.

5. The control system (100) of claim 1, wherein when current profile the coil (108) starts raising again, voltage across the coil (108) is reduced to a predefined hold-on voltage to keep the contactor in hold-on position.