FIELD OF INVENTION:
The invention relates to a terminal box provided for rotating electrical
machines. More particularly the invention provides a 11KV phase segregated
terminal box without compound filing for rotating electrical machines.
BACKGROUND OF INVENTION:
Terminal box with phase segregation has been industry/ consultant's
requirement for termination of incoming power supply on HT motors in India.
In case of 11kV Motors, requirement of phase segregation is met by following
means:
a) By an existing Terminal box suitable for fault current of 26.2kA for 0.25
sees, at 11kV, Wherever, fault level of the supply bus is less than or
equal to 500 MVA.
b) By Phase Segregated Terminal Box (PSTB) (with compound filing), where
electrical joints are encapsulated in a compound in trifurcating box. This
box is suitable for fault current of 40kA at 11kV for 0.2 sec.
c) By Terminal box (TB) with insulated terminal from the proprietary make
(Elastimold, imported) having fault level current of 25kA for 0.17 sec.
Fig 1 shows the prior art of a terminal box assembly (01) where the motor end
connections are terminated to the dual terminal bushings per phase at back of
phase segregated terminal box (PSTB) chamber. The bushings (4) are connected
to insulating copper rod through flexible connectors. The overall size of the
terminal is approximately 540 X 850 X1625. There is no provision for special

protected opening. Further, phase segregation is provided by encapsulating
electrical joints by compound in trifurcating box (2). Customer cables are
connected to insulated copper rod in trifurcating box (2). The terminal box is
oversized and so there is difficulty in termination of customer cables (as shown
in Fig 2). In case of phase segregated terminal box with compound filling, the
motor winding terminal are isolated from each other through insulated and
steel barrier, but the bare joint connection of incoming cable of power supply to
motor terminal are exposed to each other by Air Isolation.
The industries require a high capacity Grid, fault current withstand of TB on
increasing trend and is at 40kA at 11kV for 0.2 sec. Terminal box with
compound filing to isolate all the three phase from each other is not acceptable.
Hence, the requirement to develop a Terminal Box meeting the above standards
is needed.
OBJECTS OF THE INVENTION;
An object of the invention is to provide a phase segregated terminal box for
11kV rotating machine.
Another object of the invention is to provide a phase segregated terminal box
for 11kV rotating machine without compound filing.
Another object of the invention is to provide a phase segregated terminal box
for 11kV rotating machine with direct termination.

Another object of the invention is to provide a phase segregated terminal box
for 11kV rotating machine of fault level capacity > 750 MVA/40kA for 0.2 sec.
A still further object of the invention is to provide a phase segregated box for
11kV rotating machine of reduced size.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig 1 shows a terminal box with compound filing according to prior art of the
invention.
Fig 2 shows a terminal box which is larger in size according to prior art of the
invention.
Fig 3 shows a phase segregated terminal box with direct termination according
an aspect of the invention.
Fig 4 shows a phase segregated terminal box of reduced size according to an
aspect of the invention.
DETAILED DESCRIPTION OF THE INVENTION:
The following description of the preferred embodiment is merely exemplary in
nature and is no way intended to limit the invention, its application or usage.
To provide clarity, the same reference number shall be used in the
accompanying drawings to identify similar elements.

To obviate the limitations of the existing prior art, a Phase Segregated Terminal
Box (PSTB) has been provided to meet the requirement of fault level withstand
capacity and phase segregation without the compound filling.
Fig 3 shows a terminal box assembly (301) designed in accordance to the
invention. The motor end connections are terminated to dual terminal
bushings (302) per phase at the back side of phase segregated terminal box
(PSTB) chamber. The terminal bushings (302) are directly connected to the
connector assembly (305). A protective opening (317) is provided at both sides
to interchange the winding terminals and also attend any sort of internal faults
without dismantling the terminal box from motor. Phase segregation is
provided by earthed metallic barriers forming distinct individual phase
fiberglass reinforced plastic (FRP) joint box (303). Electrical joints are made in
phase segregated terminal box (PSTB) chamber. Customer cables are connected
to connector assembly (305) at phase segregated terminal box (PSTB) chamber
(313) itself. The overall height of the terminal box is reduced in comparison to
the existing phase segregated terminal box with compound filing, hence, easier
termination of customer cables (314). The reduced size of the trifurcating box
(302) is shown in fig 4.
The invention is suitable for 4 runs of 3 core X 300 mm2- XLPE, Aluminium
Cables. Phase segregation is provided by earthed metallic barriers forming
completely distinct individual phase Fiberglass reinforced plastic (FRP)
compartments to restrict any air clearance to prevent electrical breakdown to
an earth to phase (315) and phase to phase (316) fault. The clearance and

distances in terminal box (TB) are kept more than the requirement of
hazardous area motors. (IS/ IE C60079-7).
The Terminal Box has been developed such that electrical joints between each
phases and customer cables are encapsulated within chambers isolated from
each other by fiberglass reinforced plastic (FRP) and steel barrier thus
maintaining phase segregation requirement.
The invention was tested at Central Power Research Institute for following test
to prove capability to with stand short time current and internal arc.
a) Three phase to ground internal arc test (symmetrical) (40kA for 0.2 sec at
11kV/762 MVA for 0.2 sec)
b) Single phase to ground internal arc test (symmetrical) (40kA for 0.2 sec
at 11kV/ 762 MVA for 0.2 sec)
c) Through fault current test at 44kA for 0.25 sec)
In first two tests an internal arc was created and 40kA current was passed for
0.2 sec. The explosion energy was released from pressure relief diaphragm with
no disintegration except for pressure relief diaphragm. In third test 44kA
current was passed for 0.25 sec with all the three terminals of TB shorted
together. There was no damage to the terminals and bushings.
This invention is described in detail with the best modes to carry out the
invention. It is intended to include any sort of modification that may occur to
any person skilled in the art so as they come within the scope of the invention.

WE CLAIM:
1. A Phase Segregated Terminal Box (PSTB) assembly (301) for rotating
electrical machine comprising;
- plurality of terminal bushings in direct connection with the connector
assembly (305).
- at least a motor end connection terminated to plurality of said
terminal bushings (302) per phase.
- protective opening (317) on both sides to allow interchanging of
winding terminals.
- means to extensively reduce fault which may occur in the terminal
windings.
- wherein the phase segregated terminal box is in direct termination
and devoid of compound filling within the said PSTB.
.2. A PSTB as claimed in claim 1, wherein the terminal box may be suitable
for 11 KV motors.
3. A PSTB as claimed in claim 1, wherein the said means of reducing fault
which may occur in the terminal winding is at least an earthed metallic
barrier forming distinct individual phase fiber reinforced plastic (FRP)
compartments.
4. A PSTB as claimed in claim 1, wherein the compact design of the said
terminal box enables accurate cable terminations.
5. A PSTB as claimed in claim 1, as disclosed herein are supported by the
accompanying drawings.
6. A PSTB suitable for termination for 4 runs of 3 core X 300 mm2. XLPE,
Aluminium Cables

ABSTRACT

A Phase Segregated Terminal Box (PSTB) assembly (301) for rotating electrical
machine comprising; plurality of terminal bushings in direct connection with
the connector assembly (305); at least a motor end connection terminated to
plurality of said terminal bushings (302) per phase; protective opening (317) on
both sides to allow interchanging of winding terminals; means to extensively
reduce fault which may occur in the terminal windings; wherein the phase
segregated terminal box is in direct termination and devoid of compound filling
within the said PSTB.