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
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A two piece insulator support block for a resin cast transformer
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Lobo Anthony Marcel, Crompton Greaves Limited, High Voltage & Insulation Laboratory, CG Global R&D Center, Kanjur Marg (East), Mumbai 400042, Maharashtra, 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 a two piece insulator support block for a resin
cast transformer.
This invention also relates to a method of manufacturing a two piece insulator support block for a resin cast transformer. This invention also relates to a resin cast transformer comprising the above support block.
BACKGROUND OF THE INVENTION
A resin cast transformer is used in power supply and distribution systems and comprises resin cast low voltage (primary) and high voltage (secondary) windings mounted over a magnetic material core and held between a top frame and a bottom frame. In order to ensure smooth and proper functioning of the transformer it is essential that the spacing between the windings is maintained and the windings are electrically isolated from each other and also from the frames of the transformer. US 6806803 discloses insulator support blocks for maintaining the spacing between the windings and electrically isolating the windings from each other and from the frames of the transformer. A plurality of insulator support blocks are located between the top frame and the upper end of the windings and between the bottom frame and the lower end of the windings. Each of the support blocks comprises a base portion formed
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with a recess at one surface thereof for a clamping bolt to be engaged therein and with a spacer projection integrally at the opposite face thereof. The spacer projections of the support blocks extend into the spacing between the windings so as to maintain the spacing between the windings and to electrically isolate them. The windings are electrically isolated from the frames by the base portions of the support blocks. The support blocks are manufactured by casting a castable insulator material such as epoxy resin and the spacer projections are formed by extensive machining. Because of the single piece or integral construction of the support blocks and extensive machining involved, manufacture of the support blocks is time consuming and labour oriented and cumbersome to carry out. As a result productivity is reduced and cost of manufacture is increased. Also there is wastage of material due to extensive machining. Separate support blocks also may be required for windings of different dimensions thereby further increasing cost and inventory.
OBJECTS OF THE INVENTION
An object of the invention is to provide a two piece insulator support
block for a resin cast transformer, which support block is simple in construction, easy and convenient to manufacture, reduces the manufacturing time and is cost effective.
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Another object of the invention is to provide a two piece insulator support block for a resin cast transformer, which support block can be common for windings of different dimensions and further reduces manufacturing time, cost and inventory.
Another object of the invention is to provide a two piece insulator support block for a resin cast transformer, which support block reduces wastage of material.
Another object of the invention is to provide a method of manufacturing a two piece insulator support block for a resin cast transformer, which method is simple, easy and convenient to carry out and reduces manufacturing time and is cost effective.
Another object of the invention is to provide a method of manufacturing a two piece insulator support block for a resin cast transformer, which method reduces wastage of material.
Another object of the invention is to provide a resin cast transformer comprising the above support block.
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DETAILED DESCRIPTION OF THE INVENTION According to the invention there is provided a two piece insulator support block for a resin cast transformer, the support block comprising a base portion formed with a recess at one face thereof for locating a clamping bolt to be located therein and an engaging slot at the opposite face thereof and a spacer projection having an engaging end profiled corresponding to the engaging slot and fitted in the engaging slot.
According to the invention there is also provided a method of manufacturing a two piece insulator support block for a resin cast transformer, the method comprising casting a base portion with a castable insulator material, the base portion having a recess formed at one face thereof for a clamping bolt to be located therein and an engaging slot at the opposite face thereof, the method further comprising machining a spacer projection of an insulator material to form an engaging end profiled corresponding to the engaging slot and fitted in the engaging slot.
According to the invention there is also provided a resin cast transformer comprising resin cast low voltage and high voltage windings mounted over a magnetic material core and held between a top frame and a bottom frame and a plurality of two piece insulator support blocks located between the top frame and the corresponding upper end of the
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windings and between the bottom frame and the corresponding lower end of the windings, the support blocks each comprising a base portion formed with a recess at one face thereof for a clamping bolt to be located therein and an engaging slot at the opposite face thereof and a spacer projection having an engaging end profiled corresponding to the engaging slot and fitted therein, the base portion electrically isolating the windings from the top and bottom frames and the spacer projections extending into the space between the windings in order to hold the windings in position and to electrically isolate the windings from each other.
The following is a detailed description of the invention with reference to the accompanying drawings, in which :
Fig 1 is an isometric view of the two piece insulator support block for a resin cast transformer according to an embodiment of the invention from one face thereof;
Fig 2 is a crosssectional view of the support block of Fig 1 at line A-A in Fig 1;
Fig 3 is an isometric view of the support block of Fig 1 from the opposite face thereof; and
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Figs 4, 5 and 6 are elevation, plan and side view of a resin cast transformer comprising the support blocks of Figs 1 to 3, respectively.
The support block 1 as illustrated in Figs 1 to 3 of the accompanying drawings comprises a base portion 2 formed with a recess 3 at one face thereof and a dove tail profiled engaging slot 4 at the opposite face thereof. 5 is a spacer projection having an engaging end 6 profded corresponding to the dove tail profiled engaging slot and fitted in the engaging slot. The base portion is cast with a castable insulator material such as epoxy resin. The spacer projection is made of an insulator material such as fibre glass cut to size and machined to form the engaging end. Since the base portion is cast and machining is required only for the engaging end of the spacer projection manufacturing time and labour are reduced, productivity is increased and there is substantial cost benefit. Wastage of material due to machining is also substantially reduced. The support blocks of the invention also can be advantageously used as common support blocks for windings of different dimensions. This further reduces manufacturing time, cost and inventory.
The resin cast transformer 7 as illustrated in Figs 4 to 6 of the accompanying drawings comprises a plurality of support blocks 1 of
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Figs 1 to 3 located between the top frame 8 and corresponding upper end of the resin cast primary and secondary windings 9a and 9b, respectively and between the bottom frame 10 and corresponding lower end of the primary and secondary windings. The core of the transformer, lifting lugs of the transformer and support brackets for the support blocks are marked 11, 12 and 13, respectively. The clamping bolts 14 for the support blocks extend into the recesses at the said one faces of the support blocks. The spacer projections extend into the space 15 between the primary and secondary windings. The base portions of the support blocks electrically isolate the frames and the windings. The spacer projections extending into the space between the windings maintain the spacing between the windings and also electrically isolate the windings from each other.
It is to be clearly understood that the base portion and the spacer projection can be made of any other electrically insulating material and that the engaging slot and the engaging end of the spacer projection need not be dove tail. They can have any other geometry. Such variations of the invention are obvious to those skilled and are to be construed and understood to be within the scope of the invention.
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We claim :
1) A two piece insulator support block for a resin cast transformer, the support block comprising a base portion formed with a recess at one face thereof for locating a clamping bolt to be located therein and an engaging slot at the opposite face thereof and a spacer projection having an engaging end profiled corresponding to the engaging slot and fitted in the engaging slot.
2) The support block as claimed in claim 1, wherein the engaging slot at the opposite face of the base portion and the engaging end of the spacer projection are dove tail profiled.
3) A method of manufacturing a two piece insulator support block for a resin cast transformer, the method comprising casting a base portion with a castable insulator material, the base portion having a recess formed at one face thereof for a clamping bolt to be located therein and an engaging slot at the opposite face thereof, the method further comprising machining a spacer projection of an insulator material to form an engaging end profiled corresponding to the engaging slot and fitted in the engaging slot.
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4) The method as claimed in claim 3, wherein the engaging slot at the opposite face of the base portion and the engaging end of the spacer projection are dove tail profiled.
5) A resin cast transformer comprising resin cast low voltage and high voltage windings mounted over a magnetic material core and held between a top frame and a bottom frame and a plurality of two piece insulator support blocks located between the top frame and the corresponding upper end of the windings and between the bottom frame and the corresponding lower end of the windings, the support blocks each comprising a base portion formed with a recess at one face thereof for a clamping bolt to be located therein and an engaging slot at the opposite face thereof and a spacer projection having an engaging end profiled corresponding to the engaging slot and fitted therein, the base portion electrically isolating the windings from the top and bottom frames and the spacer projections extending into the space between the windings in order to hold the windings in position and to electrically isolate the windings from each other.
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6) The transformer as claimed in claim 5, wherein the engaging slot at the opposite face of the base portion and the engaging end of the spacer projection are dove tail profiled.
Dated this 13th day of August 2008

(Jose M A)
ofKhaitan&Co
Agent for the Applicants