FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A trip coil assembly
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Sathe Chandrashekhar Manohar, Khedkar Parag Prabhakar. Joshi Himanshu Chandrakant and Sanas Ashok Haribhau, of Crompton Greaves Ltd, A-3, MIDC, Amabd, Nashik, Maharashtra, India, all Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a trip coil assembly. Particularly, the present invention relates to trip coil assembly using coils with a method of physical transposition for achieving identical magnetic flux and identical operating timings. The coils are physically wound over a bobbin such that both the coils are covering equal iron area.
BACKGROUND OF THE INVENTION
A trip coil assembly is a type of electromagnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases. Trip coil assembly comprises of a stationary iron core and moving iron core in the form of a magnetic circuit, possibly broken by a few narrow air gaps. This is because iron presents much low reluctance to the magnetic field than air. So a stronger field can be obtained if most of the magnetic field's path is within the core.
When an electric current is passed through the coil it generates a magnetic field that attracts the moving core through an air gap. Moving core assembly comprises of a moving iron core to which plunger is connected and a spring inside core. After energization, the moving core assembly attracted by the stationary iron core, it starts moving to complete its stroke against reluctance offered by an air gap. During the travel of the moving core assembly, plunger touches the trigger of the mechanism and starts pushing it further. At a certain time, trigger which was holding the trip spring load with

the help of trip holding latch de-latches and the trip spring energy gets released, thus the breaker contacts gets opened.
A coil is usually used as a trip/ close coil in circuit breakers for facilitating the tripping/closing of the circuit breaker through a plunger connected thereto. Upon energizing the tripping or closing coil, the plunger connected to the moving core is actuated to move away from the moving contacts of the circuit breaker, which are also connected thereto, to trip the circuit breaker.
Trip coil or a coil is made by a winding a conductor around a bobbin or a former and then encapsulating it in some electrically insulating medium. This insulating medium can be epoxy or similar material. This trip coil or a coil is having two terminals coming out of insulating material for electrical connections.
For a double trip/close coil, one coil is physically placed over another coil with some electrically insulating medium between them. The coil surrounds the iron core (stationary iron core and moving iron core). A cross-sectional diagram of a double trip coil assembly for circuit breaker operation used in the prior art is shown in Fig. 1.
From the Fig. 1 it is clear that the operating coill (1) surrounds larger the stationary iron core area (3) and lesser, the moving iron core area (4) by bridging the air gap (5). When supply is given to this coil, it produces magnetic field, which will complete its path through the air gap (5). It attracts the moving iron core (4) and thus lifts

the trip latch (not shown in figure) to perform opening operation of the circuit breaker. Thus, the opening time of this coil is faster. The operating coil2 (2) surrounds the larger moving iron core area and lesser the stationary iron core area. When supply is given to this coil, it produces magnetic field, which will complete its path through the air gap. As this coil is away from the stationary iron core (3), it will take some time to attract the moving iron core (4). Hence, the opening time of this coil (2) is more than that of operating coill (1).
It is very critical and important that the trip coil assembly should be healthy and conducting to cause instant tripping of the circuit breaker. Any delay in tripping of the circuit breaker can cause damage to the electrical load(s) and accidents. This will lead to increase in system instability.
Thus it is customary to provide an additional trip coil as a backup coil mounted on the same magnetic core, which will operate when primary trip coil fails to operate.
OBJECTIVES OF THE INVENTION
An objective of the invention is to provide a trip coil assembly which obviates the aforesaid drawbacks by providing an assembly which operates with identical operating time, which depends on the value of magnetic core flux.

DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the aforesaid and other objectives, according to the invention, a trip coil assembly for circuit breaker is disclosed, which comprises of two coils co-axially wound together wherein said two coils are separated from each other with a known insulating material such that said two coils have the same iron area and air gap area.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 2 illustrates the front view of the trip coil assembly.
Referring to the Figure 2, the present invention relates to a trip coil assembly for circuit breaker comprising of two coils (6 and 7) co-axially wound together wherein said two coils are separated from each other with a known insulating material (8). The two coils are placed in such a way such that the two operating coils have the same iron area and air gap area. Due to the above, the reluctance offered for flux establishment upon coil energization for the two coils will be the same, unlike the prior art shown inifig 1, where the operating coil 2 surrounds much of the air gap.

Because of identical flux production the operating times will be identical. Also, since both the operating coils are utilizing iron core area and air gap area identically, the power consumption of both the coils is same and lesser as compared to the trip coil disclosed in the prior art.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.

We claim:
1. A trip coil assembly for circuit breaker comprising of two coils co-axially wound together wherein said two coils are separated from each other with a known insulating material such that said two coils have the same iron area and air gap area.