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
A compact vacuum circuit breaker
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Rajhans Rupesh Subhashrao of Crompton Greaves Ltd, S6 & Power quality Division, D2-MIDC, Waluj, Aurangabad 431 136, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention:

FIELD OF INVENTION
The invention relates to a compact vacuum circuit breaker comprising plurality of pole units having the metal end plates carrying the terminals encapsulated with a polycrete material.
BACKGROUND OF THE INVENTION
Vacuum circuit breakers are used to interrupt current flowing under faulted conditions by opening the circuit and extinguishing arcing using vacuum. A vacuum circuit breaker usually comprise a vacuum interrupter and metal plates carrying terminals. In the conventional vacuum circuit breakers, the vacuum interrupter and the live parts such as metal endplates carrying the terminals remain exposed. This necessitates wider spacing among the pole units of the circuit breaker in order to achieve phase to phase clearances. Such increased space requirement is not desirable from a design perspective as well as in view of the increased energy requirement due to such spacing and energy losses accompanying such wider spacing. Moreover, there is a likelihood of moisture ingression into the exposed interrupter resulting in flash over type failures. Also a compact design is recommended to achieve stable performance of the circuit breaker under unsymmetrical fault conditions.
Accordingly the invention provides a compact vacuum circuit breaker comprising plurality of pole units having the vacuum interrupter and the metal end plates carrying the


terminals encapsulated with polycrete material wherein the incoming and outgoing terminals of the circuit breaker are at a 180° phase shift to each other.
The circuit breaker of the invention is a multi-pole circuit breaker having encapsulated terminals. The polycrete material used to encapsulate the vacuum interrupter and the terminals of the circuit breaker is usually a polymer resin reinforced with a mineral filler. Advantageously, the encapsulant is a nanocomposite of a polymer resin and clay. The vacuum interrupters encapsulated in the polycrete gives an advantage of avoiding of moisture ingression and minimizing the flashover type failures during service.
The vacuum circuit breaker of the invention has the pole unit of the middle phase designed in such a way that the incoming and outgoing terminals are in 180° phase shift. Such an arrangement further facilitate phase to phase clearances and allows flexibility for external connections. The compact vacuum circuit breaker of the invention is especially suitable for outdoor applications and applications that require compact arrangements.