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 rotating electric machine
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
Inventor
Khatua Satyaranjan, Crompton Greaves Limited, Machines 7 Division (M7), D-5, Industrial Area, MPAKVN, Mandideep - 462046, Madhya Pradesh, 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 rotating electric machine.
BACKGROUND OF THE INVENTION
A rotating electric machine like electric motor includes a stator and a rotor rotatable about the stator. The stator comprises a cylindrical magnetic material body having a plurality of stator slots formed along the circumference thereof in a radially spaced apart relationship. The stator slots are generally circular, semi-circular or square shaped and have stator windings inserted therein. In order to reinforce the stator slots and render them mechanically strong, non-magnetic material wedges are inserted in the stator slots. The wedges are usually made of non-magnetic material such as epoxy and are generally one piece construction. In order to locate the wedges in the stator slots, each of the stator slots is formed with a pair of wedge locator grooves at opposite faces thereof. The wedge locator grooves are directly opposite to each other and the centre line of the wedge locator grooves lies along the pitch circle diameter (PCD) of the stator slots. Therefore, the wedge locator grooves of adjacent stator slots are disposed close to each other and the space or surface area between the wedge locator grooves of adjacent stator slots is restricted. As a result, the surface area for flow of flux between adjacent stator slots is reduced and the flux density and core loss increase thereby reducing the power output of the motor. The mechanical strength of the stator is also reduced and the stator may break or get damaged over a period of time thereby reducing the life of the stator. Due to the single piece construction of the wedges, insertion of the wedges in the stator slots requires considerable effort and is inconvenient and difficult to carry out.
31 MAR 2009
2

OBJECTS OF THE INVENTION
An object of the invention is to provide a rotating electric machine which has reduced
flux density and core loss and increased power output.
Another object of the invention is to provide a rotating electric machine which is mechanically strong.
Another object of the invention is to provide a rotating electric machine which is simple in construction and easy and convenient to make.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a rotating electric machine including a stator comprising a cylindrical magnetic material body having a plurality of stator slots along the circumference thereof in a radially spaced apart relationship and a pair of wedge locator grooves corresponding to each of the stator slots provided at opposite faces of each of the stator slots and non-magnetic material wedges inserted in each of the stator slots and located in the corresponding wedge locator grooves and stator windings inserted in the stator slots, wherein each pair of wedge locator grooves of each of the stator slots lie offset with each other such that the tangent to each pair of wedge locator grooves of each of the stator slots makes equal angles with the pitch circle diameter of the stator slots and the wedges each comprises three pieces inserted in each of the stator slots and corresponding wedge locator grooves.

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3 1 MAR 2009

The following is a detailed description of the invention with reference to the accompanying drawings, in which:
Fig I is a cut section isometric view of a stator of an AC induction motor according to an embodiment of the invention without the wedges and stator windings; and
Fig 2 is a scrap end view of the stator of Fig 1.
As illustrated in Figs 1 and 2 of the accompanying drawings, the stator 1 of an AC induction motor (not shown) comprises a magnetic material cylindrical body 2 having a phirah'ty of stator starors 3 along the circumference thereof in a racfially spaced apart relationship. Each of the stator slots comprises a pair of wedge locator grooves 4 at opposite faces thereof. The wedge locator grooves are offset with each other such that the tangent 5 to each pair of wedge locator grooves makes equal angles, preferably 15° to 45° with the pitch circle diameter 6 of the stator slots. Wedges of three piece construction are inserted in each of the stator slots and corresponding wedge locator grooves. Stator windings (not shown) are also inserted in the stator slots. Because of the offset between corresponding wedge locator grooves of each of the stator slots, there is offset between the wedge locator grooves of adjacent stator slots and the space or surface area between the wedge locator grooves of adjacent stator slots is increased. As a result, there is increased surface area for flow of flux between the windings in adjacent stator slots and the flow density and core loss are reduced thereby increasing the power output of the motor. The mechanical strength of the stator is also increased. Damage to the stator is reduced and life of the stator is increased. Because of the three piece construction of the wedges, insertion of the
4 3 1 MAR 2009

wedges in the stator slots and the corresponding wedge locator grooves is also easy and convenient and the construction of the motor is simplified. The motor need not be AC induction motor. The invention is applicable to any other electric motor or rotating electric machine like generator or alternator comprising a stator.
3 1 MAR 2009

We claim :
1) A rotating electric machine including a stator comprising a cylindrical magnetic material body having a plurality of stator slots along the circumference thereof in a radially spaced apart relationship and a pair of wedge locator grooves corresponding to each of the stator slots provided at opposite faces of each of the stator slots and non-magnetic material wedges inserted in each of the stator slots and located in the corresponding wedge locator grooves and stator windings inserted in the stator slots, wherein each pair of wedge locator grooves of each of the stator slots lie offset with each other such that the tangent to each pair of wedge locator grooves of each of the stator slots makes equal angles with the pitch circle diameter of the stator slots and the wedges each comprises three pieces inserted in each of the stator slots and corresponding wedge locator grooves.
2) The rotating electric machine as claimed in claim 1, which is an AC induction motor.
3) The rotating electric machine as claimed in claim 1 or 2, wherein the tangent to each pair of wedge locator grooves of each of the stator slots makes equal angles of 15 to 45° with the pitch circle diameter of the stator slots.