DESC:FIELD OF THE INVENTION
The present invention relates to an electrical switching device and more particularly to an electromagnetically operated switch like contactors, starters etc. These contactors are used for process control in industries. It can also be used for switching of lighting, heating, capacitive loads.

BACKGROUND OF THE INVENTION
Present technology in this area requires the switching between the coils to be done using a limit switch which operates when the contactor is switched on & the electromagnet pole faces mate. Thus the control supply is transferred from the pick up coil to the hold on coil. In another invention the switching is done using a solid state mechanism that uses a RC circuit for calculating the coil transition timings. Patents US5510951 & US5168418 discuss the above concepts.
The current technology which uses electronic switching of two coils in DC is very complex involving a large number of components and skilful programming. Switching using limits switch reduces the mechanical life of the device. This reduces its reliability and makes it difficult to manufacture.
The present invention uses a 555 timer instead of a RC circuit to calculate the transition time which increases the accuracy to a great extent. Instead of using a programmable timer to send continuous pulses to the pick up coil initially and then to the hold on coil, the present invention requires the timer to operate only once in one operation. So, the necessity of a controller is eliminated by using a simple timer, thus simplifying the circuit and improving the manufacturability and the reliability of the device.

OBJECTS OF THE INVENTION
One object of the invention is to overcome the disadvantages/drawbacks of the prior art.
A basic object of the present invention is to provide a solid state switching device/arrangement comprising a dual coil for operating a universal electrical switching device.
These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

In an aspect of the present invention, there is provided an arrangement for solid state switching of a dual coil for operating an electrical switching device, said arrangement comprising:
a rectifier means for rectifying input alternating signal to provide a rectified signal;
a filtering means for filtering said rectified signal;
a converter means for converting said filtered signal into a mono stable signal;
a deriver means for amplifying said mono stable signal/pulse;
a timer means for determining the time duration for energizing a pick up coil(s) and a hold on coil(s);
wherein a solid state switching device switches said mono stable signal from said pick up coil (s) to said hold on coil(s) for a predetermined time duration for facilitating to continue a contact (s) of a contactor in closed condition for operating said electrical switching device.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Fig 1 shows the block diagram of the entire circuit of the device/arrangement.
Fig 2 shows the basic working of the switching of dual coil using a MOSFET 3.
Fig 3 shows the detailed circuit.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numerals are used to depict the same or similar elements, features and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, present invention provides an arrangement for solid state switching of a dual coil for operating an electrical switching device.
Referring to fig 2, the basic working of the circuit can be stated as follows: The pickup coil 1 is energized by a solid state switching device, such as 3, till the contacts are closed. 3 remain on till the contactor picks up after which, only the hold on coil 2 is energized. This is achieved by the strategic placement of 3,
The supply to the coil may be AC or DC. When voltage fed across the terminals A1 and A3 is AC, it is rectified using full bridge rectifier 6 (Refer fig.1). The rectified waveform is filtered using an electrolytic capacitor 7. A surge suppressor 5 is used to protect the circuit from voltage spikes and then the voltage is converted to 12 V DC by a DC-DC converter circuit 8. The DC-DC conversion is done using a linear regulator comprising of a transistor where the voltage is dropped from around 220V to 12V. The 12 V is used for powering the timing circuit as well as . A mono-stable pulse is generated and fed to the MOSFET driver 10 which amplifies the signal to drive 3. As 1 is designed for a high NI value required to bring the contacts together, the contactor is switched on by energizing 1 for a predetermined duration. This is controlled by a timing circuit 9 (refer to fig 3), whose output is given to the gate of 3 which switches from low resistance 1 to the high resistance 2. After the pre determined time, 3 switches off. This shorts 2 and hence the contactor is now powered by the current flowing through 2. The NI generated in 2 is sufficient to keep the contactor in closed condition and due to its high resistance; the VA consumed is very less.
ADVANTAGES:
1) Electronic switching is more reliable than mechanical switching between two coils.
2) It is a simple circuit which does not require programming.
3) The switching timing is accurately controlled using a Analog timer.
4) The heat dissipation of the MOSFET will be minimum as it operates only once in a switching cycle & remains on for a very short time thus reducing both switching & on time losses.
5) Coil hold on VA is low.
6) Average power consumption is greatly reduced.
7) More mechanical life compared to limit switch transition mechanism. ,CLAIMS:1. An arrangement for solid state switching of a dual coil for operating an electrical switching device, said arrangement comprising:
a rectifier means for rectifying input alternating signal to provide a rectified signal;
a filtering means for filtering said rectified signal;
a converter means for converting said filtered signal into a mono stable signal;
a deriver means for amplifying said mono stable signal;
a timer means for determining the time duration for energizing a pick up coil(s) and a hold on coil(s);
wherein a solid state switching device switches said mono stable signal from said pick up coil (s) to said hold on coil(s) for a predetermine time duration for facilitating to continue a contact (s) of a contactor in closed condition for operating said electrical switching device.
2. The arrangement as claimed in claim 1, wherein said pick up coil(s) is energized for said pre determined time duration by said solid state switching device to close the contact (s) of said contactor.
3. The arrangement as claimed in claim 2, wherein after said pre determined time duration said solid state switching device is turned off and shorts said hold on coil (s) to keep said contact (s) in closed condition.
4. The arrangement as claimed in claim 1, wherein said deriver means is MOSFET Driver.
5. The arrangement as claimed in claim 1, wherein said pick up coil (s) having a low resistance for providing high NI value required to close the contact (s) of said contactor.

6. The arrangement as claimed in claim 1, wherein said hold-on coil (s) having a high resistance for providing a NI value required to continue said contact (s) in closed condition for operating said electrical switching device.
7. The arrangement as claimed in claim 1, wherein said timer means is powered by 12V signal from the converter to provide said mono stable signal output.
8. The arrangement as claimed in claim 1 and claim 7, wherein said timer means is an analog timer and the like.
9. The arrangement as claimed in claim 1, wherein said rectifier means is a full bridge rectifier and the like.
10. The arrangement as claimed in claim 1, wherein said filtering means is an electrolytic capacitor filter and the like.
11. The arrangement as claimed in claim 1, wherein said converter means is a DC-DC converter and the like.
12. The arrangement as claimed in claim 1 further comprising a surge suppressor for preventing said arrangement from voltage spike (s).
13. The arrangement as claimed in claim 1, wherein said solid state switching device operated once in a switching cycle.