The present invention relates to an improved, safe and inexpensive method of providing phase segregation between terminals of three phase flame proof terminal box, intended to be used in hazardous areas. More particularly, the inventions relates to development of phase segregated flame proof terminal box for giving power to three terminal of large rating A.C. induction motors say from 150 KW to 1100 KW.
BACKGROUND OF THE INVENTION :
A.C. induction motor requires either open terminal type (phases open) OR phase segregated type terminal box for providing power to the three phases. PSTB (phase segregated terminal box) is used for safety with lot of variety and different ratings from 150 KW to 5000 KW. Phase segregation means the terminal box has three distinct phase compartments. Till date BHEL manufactures flame proof motors only with open terminal type box, as flame proof phase segregated type terminal box is not yet developed.
As phase segregated boxes has high fault withstand capacity and safe in use, customer sometimes demands such boxes in flame proof motors as well. So it

was a definite need of the time to develop such box in order to enhance the industrial application specially in hazardous areas.
OBJECT OF THE INVENTION:
It is therefore an object of the invention to develop a flame proof terminal box having features of phase segregated compartments and which permit its use in flame proof A.C. induction motors for hazardous areas.
SUMMARY OF THE INVENTION:
According to the invention, a specially designed additional phase segregated part has been fitted inside open terminal type flame proof box, in order to transform the same into flame proof PSTB box with three distinct phase segregated compartments. The phase segregated flameproof box so produced is able to provide appropriate segregation between three terminals while maintaining required clearances and creepage distances as per latest standard IEC 60079-7. The open terminal type box is made of fabricated steel and additional phase segregated part is made of fiber reinforced plastic (FRP) material. Additional part is further sub-divided into three parts viz. bottom part, phase segregated part and top cover.

The invented additional segregated part is unique and its components can be easily produced by press molding with the help of metallic pattern. Also back-plate of existing open terminal type box has been modified in the newly developed box in order to accommodate additional segregated part without trouble. The present invention proposes the use of PSTB type flame proof terminal box in all motors intended to be used in hazardous areas and are meant to comply the mandatory requirement as per IS/IEC 60079-1.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure – 1: Shows schematic of existing open terminal type flame proof
box as per prior art.
Figure – 2: Shows image of existing open terminal type flame proof box
as per prior art.
Figure – 3: Shows schematic of back-plate of existing open terminal type
flame proof box as per prior art.
Figure – 4: Shows schematic of modified back-plate of newly developed
phase segregated flame proof terminal box as per new art.

Figure – 5: Shows schematic of newly invented phase segregated flame
proof terminal box with modified back-plate as per new art.
Figure – 6: Shows schematic of newly invented additional phase
segregated part assembly as per new art.
Figure – 7: Shows image of newly invented additional phase segregated
part as per new art.
Figure – 8: Shows schematic of newly invented phase segregated flame
proof terminal box with modified back-plate and newly invented additional phase segregated part as per new art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION:
As shown in schematic diagram of Fig.1 existing open terminal type flame proof box and back plate (A) is used for fixing of Terminals with insulator inside terminal box. Other major components of terminal box are Wrapper (B), Bottom wrapper (C), Front cover (D), Terminals with insulator (E) and Gland plate (F).
As shown in schematic diagram of Fig.4 modified Back plate (A1) of newly invented box. The modification has been done in order to relocate terminals with bushings (E).

As shown in schematic diagram of Fig.5 newly invented phase segregated flame proof terminal box with modified back-plate (A1). All other components like Wrapper (B), Bottom wrapper (C), Front cover (D), Terminals with insulator (E) and Gland plate (F) has been retained as per prior art.
As shown in schematic diagram of Fig.6 newly invented Additional phase segregated part assembly (P) which is made of FRP material. Additional part assembly consists of three sub-parts viz. Bottom cover (P1), Segregated or middle part (P2) and Top cover (P3).
As shown in schematic diagram of Fig.8 complete image of newly developed phase segregated type flame proof box with modified back-plate (A1) and newly invented Additional phase segregated part assembly (P), all other items of existing open terminal type terminal box have been retained as per prior art.

WE CLAIM
1) A phase segregated flame proof terminal box (PSTB) (1 ) for high tension
motors, characterized by suppressing fire generated within the box due to
electrical spark for loose connection, if any, comprising,
a) Back plate (A1)
b) Phase segregated part (P)
c) Wrapper (B)
d) Bottom wrapper (C)
e) Front cover (D)
f) Terminals with insulator (E)
g) Gland plate (F)

2) The PSTB as claimed in claim 1, wherein the back plate A1 disposed to relocate the terminals facilitating segregation, ease of connection and fitting the phase segregated part (P).
3) The PSTB as claimed in claim 1, wherein a phase segregated part (P), characterized by segregating the phases of electrical connection and eliminating chances of being shorted among themselves.

4) The Phase segregated part (P) as claimed in claim 3, wherein the bottom cover (P1) disposed to cover the bottom of the segregated part (P).
5) The Phase segregated part (P) as claimed in claim 3, wherein the middle part (P2) disposed at the middle to segregate the phases within part (P).
6) The Phase segregated part (P) as claimed in claim 3, wherein the top cover (P3) disposed to cover the top of the segregated part (P).
7) The phase segregated part (P) as claimed in claim 3 and its bottom cover (P1), middle part (P2) and top cover (P3) are made up of FRP (fiber reinforced plastic), characterized by better insulation, hardness and durability.