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
Provisional Specification
(See section 10 and rule 13)
TITLE OF THE INVENTION
Wound core assembly in a gas filled test transformer


APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai
400030, Maharashtra, India, an Indian Company
INVENTORS
Anthony Lobo and Venkatasami Athikkan, both of Crompton Greaves Ltd, Condition Monitoring and Diagnostic Centre (CMDRC), CG Global R&D Centre, Kanjur Marg (East), Mumbai 400042, Maharashtra, India, both are Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention

The invention relates to core and coil assembly for a wound cored electric transformer, particularly this assembly preventing damage of core and coil as well as making the assembly a robust mechanical construction to withstand short circuit forces.
High voltage transformers are widely used for the transmission of electricity to increase the voltage of generated power or to decrease the transmission voltage down to low voltage levels for household or industrial applications. The coil structure in transformer comprises a low voltage coil surrounding a coil window and a high voltage coil surrounding the low voltage coil. The core structure in such a transformer comprises a core loop having a leg extending through the coil window. Should a short circuit occur on the load side of the transformer as a result of an equipment or cable failure, short-circuit currents, typically of high magnitude, will flow through the low voltage coil and produce high mechanical forces tending to collapse the low voltage coil onto the leg of the core loop.
In the traditional transformer having a core of silicon steel, the core leg has been able to resist such collapse of the surrounding low voltage coil without significant impairment. Such silicon steel core has sufficient stiffness and other properties to enable it to resist this mode of collapse without significant damage to the core. But in certain other types of transformers, the core does not have sufficient stiffness to resist such collapse of the surrounding coil without impairment. Although wound cored transformers are costly due to special process involved and have limited applications. However wound cored transformers offer low losses and excitation current.
3 0 MAR 2009
2

Accordingly the invention provides a core and coil assembly for a wound cored electric transformer.
Another object of the invention is to provide a core and coil assembly, which will prevent damage to coil and core assembly of transformer.
Yet another object of the invention to provide a core and coil assembly, which will give resistance to short circuit currents through coil structure.
The invention relates to core and coil assembly for a wound cored electric transformer, particularly this assembly prevent damage of core and coil as well as resistance to short circuit currents through coil structure.
In accordance with the present invention, the transformer core consists of a wound core. This core is wound on a winding machine with processes involved for annealing etc. The core is then cut in two halves to form a 'C' and the cut faces are machined so that when the two halves are fixed together to form a path the machined faces form a firm connection. The one end of the 'C' formation of both halves of core is passed through the coil. The other end of the core joins below the coil to form a complete loop. The bottom portion of the core rest on a base plate with insulation between the core & the base plate.
3 0 MAR 2009
3

The base plate has plurality support legs of square section type projections. The location of the support legs is such that two nos each are on either side of the 'C' core at suitable distance away from the centre (parting line of the 'C' core) and can provide insulation between the core face & the support leg to prevent direct contact. The height of the square section of the support legs is just enough to accommodate insulation between the top face of the support legs with core & the metal shield plate which fits on the four support legs which prevents the core from moving upwards. The screw connecting the support leg and the shield plate is insulated with a nylon bush on one side of the core so that it does not form a complete turn.
Two nos of support legs are located on the width of the core with a gap to provide insulation between the core & the support leg.
In accordance with the present invention, a steel band with insulation between the steel band & the core is passed above the core to firmly hold the two halves of the core in position and this steel band is arrested on either side of the core with the help of the two nos support legs along the width of the core. The core coil assembly is now complete for tanking.