CLIAMS:1. A solenoid actuator for an electrical switching device, said actuator comprising:
a moving plunger;
a solenoid assembly comprising a coil bracket, a magnetic coil, a magnetic core, a tripper, a spring,
wherein said moving plunger assembled in said solenoid assembly facilitates tripping in said electrical switching device during electrical fault condition(s), therefore providing protection to said electrical switching device.

2. The actuator as claimed in claim 1, wherein said moving plunger comprises a ring protruded at the top of said moving plunger for restricting the movement of said plunger, thereby providing protection to said spring from deformation.

3. The actuator as claimed in claim 1, wherein said moving plunger, said magnetic core and said coil bracket(s) providing a magnetic path.

4. The actuator as claimed in claim 1, wherein said spring maintaining the air gap between said moving plunger and said magnetic core.

5. The actuator as claimed in claim 1, wherein said coil bracket (s) having an extended part for holing said tripper.

6. The actuator as claimed in claim 1, wherein said tripper facilitating the tripping action in said electrical switching device for clearing fault.

7. The actuator as claimed in claim 1, wherein a magnetic force of attraction acts in between said moving plunger and said magnetic core due to the magnetic flux flowing in the magnetic path, when current in said magnetic coil increases from a pre-defined current value, therefore pulling said plunger in downward direction.

8. The actuator as claimed in claim 7, wherein the air gap created between said ring and said bracket at the top providing additional force for pulling said plunger in downward direction, therefore facilitating tripping in said electrical switching device.

9. The actuator as claimed in claim 1, wherein said spring is a compression spring placed essentially concentrically in between the moving plunger and the core.

10. The actuator as claimed in claim 1 or claim 9, wherein said spring is designed in such a way that its load value helps in maintaining the desired air gap between the plunger and the core at static condition.
,TagSPECI:TECHNICAL FIELD OF THE INVENTION
The present invention relates generally relates to electromagnetic solenoid coil. More particularly, present invention provides a fast stroking solenoid actuator for tripping mechanism of an electrical switching device, in particular a circuit breaker, a disconnector or a contactor to be used preferably in low voltage electrical systems.
BACKGROUND AND THE PRIOR ART
Electrical switching apparatus, such as circuit breakers, are employed in diverse capacities in power distribution systems, for example, to provide protection for electrical equipment from electrical fault conditions (e.g. without limitation, current overloads, short circuits, abnormal level voltage conditions). Therefore, the tripping action at the instant of fault of any circuit breaker is totally governed by the performance of its electromagnetic release system and the mechanism system. The electromagnetic system consists of a magnetic material solenoid core, an electrical current conductive coil, a moveable magnetic plunger and the coil bracket which held the coil assembly in its place. It is the action of the moving plunger which actuates the process of tripping in the mechanism. The force generated by the solenoid plunger is used to actuate the trip bar of the circuit breaker. So it is very important to generate optimum force required to trip the circuit breaker at desired current. With the size of the products getting optimized, it is important to optimize the design of magnetic actuators like solenoids to generated required force in minimum size. So the efficiency of magnetic system is of utmost important.

A typical electromagnetic solenoid has a coil placed in a solenoid core with a plunger which is acted upon by the magnetic force developed by the coil. Usually, the solenoid core includes a coaxial cylinder. The plunger has a rod which is received in the cylinder by spring engagement. The core, the plunger and the coil bracket are constructed from magnetic material such as soft magnetic iron.
When a current flows in the coil, magnetic flux is developed through a flux path. The flux path is along the core radially outward of the coil, flows through the air gap to the moving plunger, which is then received by the coil bracket and finally, radially back to the core across another air gap within the bracket between the plunger rod and the core.
Where the magnetic flux radially crosses the air gap in the coaxial bracket between the plunger rod and the solenoid core, a significant amount of magnetic force is lost. Since the rod is moved axially along the axis of the core, the radial flux does not contribute to any force to cause this movement. Therefore, only one half of the total available magnetic flux which is axial in the air gap between the end of the core and the plunger is being used to produce a magnetic force upon the plunger. Since magnetic force is proportional to the square of flux within the air gap, the loss of one-half of the total available magnetic flux results in the loss of three-fourths of the available force which may be obtained from such flux.

Some prior art documents provided here:
US5162767 discloses a high efficiency solenoid includes a magnetic material solenoid core, an electrical current conductive coil and a moveable magnetic plunger. The solenoid core has a first end portion, a first face disposed at the first end portion, a second end portion opposite the first end portion and a continuous channel disposed in the first face. The electrical current conductive coil disposed in the channel and arranged so that magnetic flux developed in response to a current in the coil forms a first magnetic pole on the first face interiorly of the channel and a second magnetic pole of opposite plurality on the first face exteriorly of the channel. The plunger has a surface and a facing coextensive relationship to the first face. The plunger is normally biased in a first position to space the surface from the first face to form a gap therebetween. There is no magnetic material which is received through a bore within the solenoid core. Therefore, the magnetic flux when present is bidirectional through the gap so that all magnetic flux exterior of the solenoid core develops a magnetic force substantial orthogonal to the surface to move the plunger to its second position, which is drawn towards the solenoid core reducing the gap.

Therefore, to overcome the disadvantages present in prior art, it would be highly desirable to construct a solenoid which utilizes all the flux crossing any air gap within the solenoid for developing useful force on the plunger. The present invention provides an improved and fast stroking solenoid actuator.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved and fast stroking solenoid actuator for tripping mechanism of an electrical switching device.
Another object of the present invention is to provide an improved solenoid actuator which utilizes all available magnetic flux, thereby providing high efficiency.
These and other advantages of the present invention will become readily apparent from the following detailed description read 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 a solenoid actuator for an electrical switching device, said actuator comprising:
a moving plunger;
a solenoid assembly comprises a coil bracket, a magnetic coil, a magnetic core, a tripper, a spring,
wherein said moving plunger assembled in said solenoid assembly facilitating tripping in said electrical switching device during electrical fault condition(s), therefore providing protection to 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.
Figure.1 illustrates a solenoid assembly.
Figure.2 (a) & (b) illustrates the front view of solenoid and side view of solenoid.
Figure.3 illustrates a moving plunger.
Figure.4 illustrates the general assembly of solenoid assembly placed inside a circuit breaker.
Figure.5 illustrates the plots of magnetic force developed vs. increasing current for the new modified moving plunger and the prior art plunger in solenoid.

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 numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE 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 a solenoid actuator for an electrical switching device.
The present invention relates to fast stroking solenoid plunger for a switching device. The moving plunger (3) is assembled in the solenoid assembly (shown in Fig 1). The solenoid assembly consists of the coil bracket (1), the magnetic coil (2), the core (4), the tripper (5) and the spring (6) as shown in Fig 2. In the present invention, an additional ring is protruding in the moving plunger as shown in Fig 3.
The moving plunger, the core and the coil bracket completes the magnetic path. The compression spring (6) is placed in between the moving plunger (3) and the core (4), with core at the base such that it is concentric to the core and the plunger. This spring is designed in such a way that its load value helps in maintaining the desired air gap between the plunger and the core at static condition. The magnetic coil (2) is for current carrying purpose. The coil bracket has an extended part which holds the tripper (5). This tripper mediates the trip command action into the mechanism part of the circuit breaker (Fig 4).
When current in the magnetic coil exceeds a certain value, magnetic force of attraction between the plunger and the core comes into picture as the magnetic flux flowing in the magnetic path becomes stronger. As the plunger moves downward overcoming the spring load, an additional pulling force acts on the plunger ring by the top face of the coil bracket. As distance decreases, the pulling force increases by around 10-15% times compared with the conventional plunger.

This plunger adds more path of less reluctance to the magnetic flux. In addition and most importantly it facilitates the pulling action of the core on the moving plunger by doubling the attractive force. First the plunger is pulled down by the core face in the air gap between the plunger and the core. Secondly the air gap between the top bracket and the ring part of the plunger also enhances the pulling action. As a result the plunger experiences a fast stroke of attractive force that immediately triggers the tripping signal onto the mechanism and the circuit breaker breaks the circuit for successful fault clearing action.
The graph shown in figure 5, plots the magnetic force developed vs. increasing current for the new modified moving plunger and the prior art plunger in solenoid.
ADVANTGES
· The plunger moves and hits the static plunger at a faster stroke.
· The rapid movement of the plunger ensures tripping at the moment of fault occurrence.
· Ring at the top ensures restriction in the movement of the plunger to required length and hence deformation in the spring can be avoided.
· Easy of assembly
· Ensures concentricity with the static plunger and the bracket
· Higher efficiency solenoid which fully utilizes all available flux