FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A sensing system for sensing field current of generators, and generators, thereof
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Khatua Satyaranjan, of Crompton Greaves Ltd, machine (M7) Division, D-5 Industrial Area, MPAKVN, Mandideep-462046, Madhya Pradesh, India; an Indian National.
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 the field of synchronous generators.
Particularly, this invention relates to a sensing system for sensing field current of generators, and generators, thereof.
Brief description of Innovation:
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.
Synchronous machines mechanically rotate a permanent magnet assembly or an electromagnet (with slip rings) assembly in synchronism with the current in the active winding set for useful torque production according to Lorentz Relation.
Field current refers to exciting current or current in a field winding. An automatic voltage control device controls the field current to keep output voltage constant.
For sensing the field current of the generators a special arrangement of carbon brushes, holders and spindles are provided to protect the Generator. According to the existing prior art generators, and arrangements, the sensing system was a separate part in the generator. For providing that arrangement,

additional hub along with insulation was required at the exciter cover so that the sensing of the field circuit which is physically rotating is possible.
The problem in the earlier arrangement was that a lot of additional components were involved. These additional components, when arranged / assembled, extended beyond the generator assembly and required the provisioning of a hub beyond the generator body. This made the generator larger, expensive, and complicated.
Objects of the Invention:
An object of the invention is to provide a generator without a hub, said generator having a system for sensing field current.
Yet another object of the invention is to provide a generator with a field current sensing system, said generator being a relatively smaller generator.
Still another object of the invention is to provide a generator with a field current sensing system, said generator being a relatively inexpensive generator.
Summary of the Invention:
According to this invention, there is provided a sensing system for sensing field current of generators, said sensing system comprises: rotating rectifier unit characterized, in that, a slip ring and brush assembly for sensing field current are located at said rotating rectifier unit.

According to this invention, there is provided a generator with a sensing system for sensing field current of said generators, said generator comprises:
a. shaft protruding from said generator, said generator having rotating parts
housed in an exciter frame;
b. rotating rectifier unit placed lateral to said exciter frame characterized, in
that, a slip ring and brush assembly for sensing field current are located at
said rotating rectifier unit; and
c. exciter cover adapted to house said rotating rectifier unit, slip ring and
brush assembly.
Typically, said generator includes a stud adapted to couple said rectifier unit with said exciter cover for support.
Brief Description of the Accompanying Drawings:
Figure 1 illustrates a schematic of the generator and field current sensing system of the prior art.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates a schematic of the generator with field current sensing system,
Detailed Description of the Accompanying Drawings:
Figure 1 illustrates a schematic of the generator and field current sensing system of the prior art.

There is a shaft (1) which protrudes from the generator. The generator has rotating parts which are enclosed in the housing defined by the exciter frame (2). On its lateral side, a rotating rectifier unit (3) is placed. Output from the generator is given to the rotating rectifier assembly in order to obtain a rectified output of power. There is an exciter cover (4) to house this rotating rectifier unit. Co-axial to the generator, and extending beyond the rotating rectifier unit (3), is the slip ring unit (8) inside a slip ring cover (6) which forms the lateral-most end of the hub. This co-axial slip ring assembly houses a slip ring and brush assembly (7). Reference numeral 5 refers to the stud which couples the slip ring unit (8) to the exciter cover (4). Field current is sensed from this brush assembly (7).
According to this invention, there is provided a sensing system for sensing field current of generators, and generators, thereof.
Figure 2 illustrates a schematic of the generator with field current sensing system.
In accordance with an embodiment of this invention, there is provided a hub-less generator. Similar to the prior art, there is a shaft (1) which protrudes from the generator. The generator has rotating parts which are enclosed in the housing defined by the exciter frame (2). On its lateral side, a rotating rectifier unit (3) is placed. In this invention, the brush assembly (7) (of a slip ring) is located at the rectifier unit (3), which is housed by the exciter cover (4), thereby eliminating the need for an extended slip ring and an extended

hub beyond the exciter cover (4). A stud (5) couples the rectifier unit (3) with the exciter cover (4) for support.
Rectifier unit (3) will be used as a hub for providing insulation and slip ring on which the brush arrangement can be provided.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A sensing system for sensing field current of generators, said sensing
system comprising:
rotating rectifier unit characterized, in that, a slip ring and brush assembly for sensing field current are located at said rotating rectifier unit.
2. A generators with a sensing system for sensing field current of said
generator, said generator comprising:
a. shaft protruding from said generator, said generator having rotating
parts housed in an exciter frame;
b. rotating rectifier unit placed lateral to said exciter frame characterized,
in that, a slip ring and brush assembly for sensing field current are
located at said rotating rectifier unit; and
c. exciter cover adapted to house said rotating rectifier unit, slip ring and
brush assembly.
3. A generator as claimed in claim 2 wherein, said generator includes a stud
adapted to couple said rectifier unit with said exciter cover for support.