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
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A dual air-gap radial Flux Machine


APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400030, Maharashtra, India, an Indian Company
INVENTORS
Samsul Ekram and Deepak Gajanan Kamble, both of Crompton Greaves Ltd , APDTC, CG Global R&D Centre, Crompton Greaves Ltd., Kanjur (E), Mumbai 400042, Maharashtra, India, both are Indian Nationals


PREAMBLE TO THE DESCRIPTION
The following specification describes the invention

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This invention relates to a dual radial air-gap electric motor with reduce cogging torque.
In prior art various types of radial flux motor are available with skew in stator with dual or single rotor mechanism.
In a permanent magnet rotating machine such as an radial gap electric motor, a pair of rotors which is situated inside and outside of the stator or which sandwich the stator, and maintaining air gap there between. Permanent magnets are provided on the outer surface of the inner rotor and inner surface of the outer rotor facing the stator. The permanent magnets are arranged in such a way that their North and South poles alternate along the surface of the rotor. When electricity is supplied to the stator windings of the stator, a rotating magnetic field is created thereby rotating the rotor. In such radial gap electric motors, a rotational torque ripple called cogging torque is produced leading to vibration, noise and degraded performance of the controllability of the motor. Conventionally, such cogging torque is reduced by skewing the stator offset or skewed in the direction of the circumferential direction of the stator produce a skewing effect. Techniques for reducing the cogging torque are complicate to manufacture the motor. The amount of cogging torque being reduced in motors has always been insufficient with the conventional methods of theoretically deducing the appropriate skew angle of the stator. Skewing the permanent magnets to a skewing angle calculated by means of conventional techniques of theoretically deducing the skew angle do not take into account the effect of the skewing on the dynamic performance of the motor.
The dual air-gap machines are known for high' power density, high efficiency and
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compact construction. Normally magnet arrangement in both the rotors are as per total electrical degree with respect to number of pole.
In conventional motors, some of the drawbacks such as cogging torque in the machine arises due to the reluctance variation in rotor permanent magnet and the stator teeth.
To overcome the drawback and increase the efficiency of the motor, a cogging torque reduction technique is disclosed in the invention to reduce the machine cogging torque without disturbing the machine dynamic performance.
The symmetry hybrid skew angle in magnet and the asymmetry hybrid skew angle in magnet for the least cogging torque are the findings of the innovation.
An object of the invention is to provide a Substantial reduction on the cogging torque without disturbing the machine dynamic performance
Another object of the invention is to provide a symmetric as well as asymmetric hybrid skew in magnet which is compatible for any pole/slot ratio radial flux machine
Another object of the invention is to eliminate complexity in stator skew design and also eliminate complicated process for stator skew formation.
Another object of the invention is to provide a simple process of assembling skew magnet to reduce time & cost.
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A dual radial air-gap electric motor comprising a shaft centrally located with a motor housing, a stator sandwiched between pair of rotors with air-gap, one rotor being fitted at the shaft of the housing and the other rotor disposed with a cylindrical disc mechanically coupled with a central shaft, the rotors each comprising of a plurality of permanent magnets arranged in a skewed configuration.
In accordance to the present invention, wherein the motor housing comprises of" a main body and a closure for the main body.
In accordance to the present invention, wherein the permanent magnets on each of the rotor are symmetric skew to each other.
In accordance to the present invention, wherein the permanent magnets on each of the rotor are asymmetric skew to each other.
In accordance to the present invention, Hybrid skew angle in the magnet to reduce the cogging torque in radial flux machine without disturbing machine designed performance
In accordance to the present invention, a rotatable central shaft located with a motor housing, a rotor coupled with a central rotating shaft, rotor having a skew permanent magnets on inner as well as outer surface, rotor is sandwiched between pair of stators with air-gap, one stationary stator being mounted on the motor housing between the
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rotor and central shaft, other stationary stator is mechanically mounted on the motor housing between rotor and outer housing of the motor,.
In accordance to the present invention, a rotatable central shaft located with a motor housing, a rotor coupled with a central rotating shaft, rotor having a skew permanent magnets on outer surface, rotor is sandwiched between shaft and stator with air-gap, stationary stator being mounted on the motor housing between the rotor and outer housing of the motor.
In accordance to the present invention, a fixed central shaft located with a motor housing, rotor having a skew permanent magnets on inner surface, stator is sandwiched between shaft and rotor with air-gap, stationary stator being mounted on the motor shaft, rotor is mounted with rotating motor housing.
Dated this 18th day of March 2009