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, 2005
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
Electric motor stator INVENTOR
Name : Joshi Ashish Kashinath
Nationality : Indian National
Address : Crompton Greaves Ltd
Corporate R&D and Quality, Industrial Design Centre, Kanjur Marg(E), Mumbai - 400042, Maharashtra, India
APPLICANTS
Name: CROMPTON GREAVES LIMITED
Nationality: Indian Company
Address: CG House, Dr Annie Besant Road, Prabhadevi,
Mumbai 400025, Maharashtra, India
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 INVENTION
This invention relates to an electric motor stator.
This invention also relates to a method of making the electric motor stator.
PRIOR ART
An electric motor comprises a stator comprising a stator body formed of laminations. Stator slots are punched out around the rotor shaft opening in the stator body. The pitch diameter circle of the stator slots (ie the diameter of the circle passing through the centre of the stator slots) is uniform. Due to the uniformity of the pitch circle diameter of the stator slots, the different stator winding conductors (primary or main winding and auxiliary or secondary winding conductors in the case of a single phase motor and primary, secondary and tertiary winding conductors in the case of a three phase motor) inserted in the stator slots project or protrude into the opening in the stator body for the rotor shaft of the motor at the overlapping at the intersections of the conductors. In order to facilitate insertion of the rotor shaft in the rotor shaft opening in the stator body, it is necessary to mechanically shape the overlapping conductors using mechanical shaper. Due to mechanical shaping, production time increases thereby reducing productivity and production efficiency of the motor. During mechanical
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shaping, there are chances of the insulation of the conductors being damaged. This will result in rejection and wastage of material and loss of material cost. In order to reduce overlapping of the conductors protruding into the opening for the rotor shaft in the stator body, it is known to reduce the cross sectional area of the conductors inserted in the stator slots. This results in under utilization of the stator slots and reduction of efficiency of the motor.
OBJECTS OF INVENTION
An object of the invention is to provide an electric motor stator, which practically eliminates protrusion of overlapping of the conductors into the opening in the stator body for insertion of the rotor shaft of the motor thereby eliminating mechanical shaping and reducing production time and increasing productivity and production efficiency of the motor and also eliminating wastage of material and loss of material cost.
Another object of the invention is to provide an electric motor stator, which allows optimum use of the stator slots for the conductors correspondingly increasing efficiency of the motor.
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Another object of the invention is a method of making an electric motor stator, which method practically eliminates protrusion of overlapping of the conductors into the opening in the stator body for insertion of the rotor shaft of the motor thereby eliminating mechanical shaping and reducing production time and increasing productivity and production efficiency of the motor and also reducing wastage of material and loss of material cost.
Another object of the invention is a method of making an electric motor stator, which method allows optimum use of the stator slots for the conductors correspondingly increasing efficiency of the motor.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an electric motor stator comprising a stator body made of laminations and at least two sets of stator slots in the stator body around the opening in the stator body for the rotor shaft of the electric motor, the two sets of stator slots describing two different pitch circle diameters, one set of stator winding conductors being inserted in one set of the stator slots and another set of stator winding conductors being inserted in the other set of stator slots so as to form motor stator comprising conductors staggered radially.
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According to an embodiment of the invention, the stator comprises two sets of stator slots describing two different pitch circle diameters, primary winding conductors of the motor being inserted in one set of the stator slots and secondary winding conductors of the motor being inserted in the other set of stator slots to form a single phase electric motor stator or secondary winding conductors and tertiary winding conductors of the motor being inserted in the other set of stator slots to form a 3-phase motor stator.
According to another embodiment of the invention, the stator comprises three sets of stator slots describing three different pitch circle diameters, primary winding conductors being inserted in one set of stator slots, secondary winding conductors being inserted in a second set of stator slots and tertiary winding conductors being inserted in a third set of stator slots to form a 3-phase motor stator.
According to the invention there is also provided a method of manufacturing an electric motor stator comprising forming a stator body with laminations and punching out at least two sets of stator slots around the opening in the stator body for the rotor shaft of the motor, the two sets of stator slots
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describing two different pitch circle diameters and inserting one set of stator winding conductors of the motor in one set of the stator slots and inserting another set of stator winding conductors of the motor in the other set of stator slots so as to form a motor stator comprising conductors staggered radially.
According to an embodiment of the invention, the method comprises punching out two sets of stator slots describing two different pitch circle diameters and inserting primary winding conductors of the motor in one set of the stator slots and secondary winding conductors of the motor in the other set of the stator slots to form a single phase electric motor stator or inserting secondary winding conductors and tertiary winding conductors of the motor in the other set of stator slots to form a 3-phase motor stator.
According to another embodiment of the invention, the method comprises punching out three sets of stator slots describing three different pitch circle diameters, inserting primary winding conductors of the motor in one set of stator slots, secondary winding conductors of the motor in a second set of
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stator slots and tertiary winding conductors of the motor in a third set of stator slots to form a 3-phase motor stator.
The following is a detailed description of the invention with reference to the accompanying drawings, in which:
Figs 1 and 2 are plan and isometric view of an electric motor stator body according to an embodiment of the invention, respectively;
Fig 3 is isometric view of the stator body of Figs 1 and 2 with the stator winding conductors inserted in the stator slots therein according to an embodiment of the invention;
Fig 4 is isometric view of the stator body of Figs 1 and. 2 with the stator winding conductors inserted in the stator slots therein according to another embodiment of the invention;
Figs 5 and 6 are plan and isometric view of an electric motor stator body according to another embodiment of the invention, respectively; and
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Fig 7 is isometric view of the stator body of Figs 5 and 6 with the stator winding conductors inserted in the stator slots therein according to an embodiment of the invention.
As illustrated in Figs 1 and 2 of the accompanying drawings, 2a is a stator body made of laminations. Two sets of stator slots 3a and 3b are punched out in the stator body around the opening 4 for the rotor shaft (not shown) of an electric motor (not shown). Stator slots 3 a describe a smaller pitch circle diameter 5a and the stator slots 3b describe a larger pitch circle diameter 5b. Primary winding conductors 6a and secondary winding conductors 6b are inserted in the stator slots 3a and 3b, respectively to form a single phase electric motor stator 1A as shown in Fig 3 of the accompanying drawings. It is understood that the winding conductors are interchangeable in the stator slots.
Alternatively, primary winding conductors 6a are inserted in stator slots 3a and secondary and tertiary winding conductors 6b and 6c respectively are inserted in the stator slots 3b to form a 3-phase electric motor stator IB as shown in Fig 4 of the accompanying drawings.
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As illustrated in Figs 5 and 6 of the accompanying drawings, 2b is a stator body made of laminations. Three sets of stator slots 3a, 3b and 3c are punched out in the stator body around the opening 4 for the rotor shaft (not shown) of a 3-phase electric motor (not shown). Stator slots 3a describe a small circle diameter 5a, stator slots 3b describe a larger pitch circle diameter 5b and stator slots 3c describe the largest pitch circle diameter 5c. The primary, secondary and tertiary winding conductors 6a, 6b and 6c are inserted in the stator slots 3 a, 3b and 3c respectively to form a 3-phase electric motor stator 1C as illustrated in Fig 7 of the accompanying drawings. It is understood that the winding conductors are interchangeable in the stator slots.
Due to the different pitch circle diameters of the stator slots, the different winding conductors are radially offset or staggered thereby eliminating projection or protrusion of the overlapping of the conductors at the intersections thereof into the opening for the rotor shaft in the stator body. Therefore, mechanical shaping of the conductors is eliminated and production time is increased and productivity and production efficiency of the motor are increased. As mechanical shaping has been eliminated, damage to the insulation of the conductors is eliminated and wastage of
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material and resultant loss of material cost are eliminated. Optimum use of the stator slots is made by accommodating maximum cross-sectional area of the conductors in the stator slots thereby increasing efficiency of the motor in which the stator is used.
The stator of the invention can be configured for a two phase or multiphase motor. An electric motor comprising the. stator of the invention is also within the scope of the invention. The scope of the invention should be construed and understood to be accordingly.
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We claim :
1. An electric motor stator comprising a stator body made of
laminations and at least two sets of stator slots in the stator body around the
opening in the stator body for the rotor shaft of the electric motor, the two
sets of stator slots describing two different pitch circle diameters, one set of
stator winding conductors being inserted in one set of the stator slots and
another set of stator winding conductors being inserted in the other set of
stator slots so as to form motor stator comprising conductors staggered
radially.
2. An electric motor stator as claimed in claim 1, which comprises two
sets of stator slots describing two different pitch circle diameters, primary
winding conductors of the motor being inserted in one set of the stator
slots and secondary winding conductors of the motor being inserted in
the other set of stator slots to form a single phase electric motor stator or
secondary winding conductors and tertiary winding conductors of the motor
being inserted in the other set of stator slots to form a 3-phase motor stator.
3. An electric motor as claimed in claim 1, which comprises three sets
of stator slots describing three different pitch circle diameters, primary
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winding conductors being inserted in one set of stator slots, secondary winding conductors being inserted in a second set of stator slots and tertiary winding conductors being inserted in a third set of stator slots to form a 3-phase motor stator.
4. A method of manufacturing an electric motor stator comprising forming a stator body with laminations and punching out at least two sets of stator slots around the opening in the stator body for the rotor shaft of the motor, the two sets of stator slots describing two different pitch circle diameters and inserting one set of stator winding conductors of the motor in one set of the stator slots and inserting another set of stator winding conductors of the motor in the other set of stator slots so as to form a motor stator comprising conductors staggered radially.
5. A method as claimed in claim 4 comprising punching out two sets of stator slots describing two different pitch circle diameters and inserting primary winding conductors of the motor in one set of the stator slots and secondary winding conductors of the motor in the other set of the stator slots to form a single phase electric motor stator or inserting
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secondary winding conductors and tertiary winding conductors of the motor in the other set of stator slots to form a 3-phase motor stator.
6. A method as claimed in claim 4 comprising punching out three sets of stator slots describing three different pitch circle diameters, inserting primary winding conductors of the motor in one set of stator slots, secondary winding conductors of the motor in a second set of stator slots and tertiary winding conductors of the motor in a third set of stator slots to form a 3-phase motor stator.

(Prita Madan)
of Khaitan & Co
Agent for the Applicants
Dated this 28th day of March 2006
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ABSTRACT
An electric motor stator comprising a stator body (2a) made of laminations and at least two sets of stator slots (3a and 3b) in the stator body around the opening (4) in the stator body for the rotor shaft of the electric motor. The two sets of stator slots describe two different pitch circle diameters (5a, 5b). One set of stator winding conductors (6a) is inserted in one set of the stator slots and another set of stator winding conductors (6b) is inserted in the other set of stator slots to form a motor stator (1A) comprising conductors staggered radially (Fig 3),