FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION


TITLE OF THE INVENTION
A high torque and low noise Full Pitched Winding Switched Reluctance Machine
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Ho mi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTOR
Naresh Vattikuti an Indian national
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention.


FIELD OF INVENTION
This invention relates to switched reluctance motor (SRM) and more particularly it relates to a full pitched winding switched reluctance machine having high torque and low noise.
BACKGROUND OF INVENTION
The use of variable reluctance SRM in variable speed applications is increasing because of the distinguishing features like its ability to operate under fault condition, low manufacturing cost, its suitability for operation in harsh environments and its competitive power density when compared to other conventional machines. However, this machine has limitations such as low torque to weight ratio, acoustic noise, vibration and torque ripple. As a result of these limitations use of a conventional SRM is limited to particular applications. Some of these limitations namely low power density, acoustic noise are mitigated in patent no. US00511096A. It is named as SEGMENTED SWITCHED RELUCTANCE MACHINE (SSRM) having a foil pitched winding. SSRM can give 40% higher torque than SRM for the same frame size. Again the utility of an SSRM are bound by limitations like higher winding resistance at high Diameter to Length (D/L) ratio machines and expensive manufacturing process. The rotor of the SSRM includes an isolated segment, to make it solid casting process is required. The conventional SRM is preferred in many applications due to its low manufacturing cost, but casting process of SSRM increases the manufacturing cost.
OBJECT OF INVENTION
• The main object of the present invention is to provide a full pitched winding switched reluctance Machine.
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• Another object of the present invention is to provide a full pitched winding switched reluctance machine which is suitable for space constrained application.
• Another object of the present invention is to provide a full pitched winding switched reluctance machine which reduces the acoustic Noise and make it suitable for low noise applications such as automotive and washing machine and AC compressors.
• Yet another object of the present invention is to provide a full pitched winding switched reluctance machine reduces the manufacturing cost.
• Yet another object of the present invention is to provide a new method of winding for full pitched winding switched reluctance machine which reduce the winding resistance.
BRIEF DESCRIPTION OF INVENTION
In accordance with the first embodiment of the present invention, a full pitched winding switched reluctance machine comprises; stator having plurality of radial outwardly projecting portion constituting stator poles, rotor having plurality of radial outwardly projecting portion constituting rotor poles, said stator and rotor are disposed co-axially around central rotating axis, said projecting portion of said stator is provided with rectangular slot which define yoke portion in the said stator and facilitate increased winding fill factor, said rotor having plurality of poles which are axed shaped facilitated with the help of punching operation, said stator is made of full pitched windings wounded around the circumference of said stator for low Diameter to length (D/L) ratio machines. The AP and AN forms one phase. Each phase consist of number of turn wound in series to form one phase. The inward coil of phase A is going to slot AP and outward coil of phase A is coming out from AN.
In accordance with the second embodiment of the present invention, a full pitched winding switched reluctance machine comprises; stator having plurality of radial outwardly projecting portion constituting stator poles, rotor having plurality of radial
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outwardly projecting portion constituting rotor poles, said stator and rotor are disposed co-axially around central rotating axis, said projecting portion of said stator is provided with rectangular slot which define yoke portion in the said stator and facilitate increased winding fill factor, and said rotor having plurality of poles which are axed shaped facilitated with the help of punching operation, said stator is made of full pitched windings which are wounded around the said yoke for better cooling and to reduce the winding resistance for high D/L ratio machines for high diameter to length (D/L) ratio machines. The one phase of winding consists of two series connected coils. For phase A, API and AN1 forms one coil and AP2 and AN2 forms second coil. The inward side of the first coil is going to API and coming out from AN1. The inward side of the second coil is going to AP2 and coming out from AN2. These two coils are connected in series to form one phase.
BRIEF DESCRIPTION OF DRAWINGS
Figure-01 shows the geometry of a full pitched winding switched reluctance machine (FPWSRM) in accordance with the first embodiment of the preset invention.
Figure-02 shows the rotor arrangement of full pitched winding switched reluctance machine (FPWSRM)
Figure-03 shows the geometry of full pitched winding switched reluctance machine (FPWSRM) in accordance with the second embodiment of the present invention.
Figure-04 shows the Aligned flux plot of a full pitched winding switched reluctance machine (FPWSRM) in accordance with the first embodiment of the present invention.
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Figure-05 shows the aligned flux plot of full pitched winding switched reluctance machine (FPWSRM) in accordance with the second embodiment of the present invention.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
Now referring to figure-01, In accordance with the first embodiment of the present
invention, a full pitched winding switched reluctance machine comprises; stator (1) having plurality of radial outwardly projecting portion constituting stator poles, rotor (2) having plurality of radial outwardly projecting portion constituting rotor poles, said stator (1) and rotor (2) are disposed co-axially around central rotating axis in housing, said projecting portion of said stator (1) is provided with rectangular slot (4) which define yoke portion (5) in the said stator and facilitate increased winding fill factor which is the ratio of Slot area to Winding area, said stator (1) is made of full pitched windings (3) which are wounded around the inner circumference of said stator (1) for low Diameter to length (D/L) ratio machines.
The said stator (1) comprises a pole shoe (6) to increase the pole angle provided in the
said stator.
The said rotor (2) comprises plurality of outwardly projecting portion constituting rotor
poles (7) to increase the pole angle of said rotor (2).
The said rotor poles (7) of said rotor (2) are axed shaped facilitated and configured with
the help of punching operation.
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Said stator (1) is made of full pitched winding and increased air gap contact Area due to increased Stator pole shoe (6) and Rotor pole (7) angles to increase the torque because of decrease in the reluctance seen by the said rotor (2) at each position.
The said rectangular slot (4) is provided in the outwardly projecting portion of the said stator to increase the coil filling factor.
Increased air gap area with increased said pole angle of the stator(l) and rotor (2) facilitates more flux to pass through the said yoke (5). The higher thickness of the said yoke (5) enables to produce the more flux for the same current and same number of turns in the winding (3).
The rectangular slot (4) is provided in the outwardly projecting portion of the said stator (1) to increase the fill factor of winding and also to constrain the flux to follow the said rectangular shape to reduce the iron weight. This not only reduces the iron weight, it also provides better cooling because of increased surface area of the machine.
Said rotor (2) is having axed shaped rotor poles (7) by providing plurality of air grooves (9) provided with the help of punching operation which reduces the manufacturing cost of the said rotor (2).
The said stator (1) having plurality of radial outwardly projecting portion also constitutes groove (10) in the circumference of said stator (1).
The AP and AN shown forms Phase A. BP and BN forms Phase B. CP and CN forms phase C. Each phase consist of number of turn wound in series to form one phase. The
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inward coil of phase A is going to slot AP and outward coil of phase A is coming out
from AN. This forms phase A winding (3).
The inward coil of phase B is going to slot BP and outward coil of phase B is coming out
from BN. This forms phase B winding (3).
The inward coil of phase C is going to slot CP and outward coil of phase C is coming out
from CN. This forms phase C winding (3). This type of winding (3) are used for low
diameter to length (D/L) ratio machines.
Now referring to Figure-2 which shows the rotor (2) in accordance with the present invention, said rotor (2) comprises plurality of radial outwardly projecting portion constituting the rotor poles (7) provided to increase the pole angle of said rotor (2).
The said rotor (2) also comprises high reluctance path (8) provided between each rotor poles (7) which enables the said rotor poles (7) to be integrally connected but magnetically isolated. This arrangement of said rotor is facilitated by punching operation, hence reduces the manufacturing cost of said rotor.
Now referring to Figure-03, In accordance with the second embodiment of the present invention, a full pitched winding switched reluctance machine comprises; stator (1) having plurality of radial outwardly projecting portion constituting stator poles, rotor(2) having plurality of radial outwardly projecting portion constituting rotor poles, said stator (1) and rotor (2) are disposed co-axially around central rotating axis in housing, said projecting portion of said stator (1) is provided with rectangular slot (4) which define yoke portion (5) in the said stator (1) and facilitate increased winding fill factor, said stator is made of full pitched windings (3) which are wounded around the said yoke(5) of said stator for better cooling and to reduce the winding resistance for high D/L ratio machines for high diameter to length (D/L) ratio machines.
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The said stator (1) comprises a pole shoe (6) to increase the pole angle provided in the
said stator.
The said rotor (2) comprises plurality of outwardly projecting portion constituting rotor
poles (7) to increase the pole angle of said rotor (2).
The said rotor poles (7) of said rotor (2) are axed shaped facilitated and configured with
the help of punching operation.
Said pole angle is increase by providing pole shoe (6) in the stator and providing axed
shaped poles (7) in rotor.
Wherein Said stator is made of full pitched winding and increased air gap contact Area due to increased Stator pole shoe (6) and Rotor pole (7) angles to increase the torque because of decrease in the reluctance seen by the said rotor at each position.
The winding arrangement wound around the said yoke (5) portion of said stator (1) is provided for high diameter to length (D/L) ratio machines. The said winding arrangement wound around the said yoke (5) portion of said stator also provides better cooling of the windings and reduces winding resistance and end winding copper weight.
Said rotor (2) having plurality of poles (7) which are axed shaped facilitated with the help of punching operation.
Since winding resistance depends on Diameter to Length (D/L) ratio for full pitched winding machine. If the D/L ratio is high, the end winding length increases and it will in turn increases the resistance and copper losses.
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Thus end winding length and winding turn is reduced t>y providing the wound of the winding (3) around the said yoke (5). This arrangement keeps the torque same and reduces the winding resistance.
The one phase of winding (3) consists of two series connected coils. For phase A, API and ANl forms one coil and AP2 and AN2 forms second Poil. The inward side of the first coil is going to API and coming out from ANl. The inward side of the second coil is going to AP2 and coming out from AN2.
For phase B, BP1 and BN1 forms one coil and Bf 2 and BN2 forms second coil. The inward side of the first coil is going to BP1 and corriing out from BN1. The inward side of the second coil is going to BP2 and coming out from BN2.
FOR ptase C, CTA and CNI iorms one coVi an6 and CVil farms, -serowi The inward side of the first coil is going to CP1 and coining out from CN1. The inward side of the second coil is going to CP2 and coming out from CN2. This type of winding (3) are used for High diameter to length (D/L) ratio machines.
Now referring to Figure-4 and 5, which shows the aligned flux paths of first and second embodiment of the inventions respectively. The flux path is shorter compared to conventional SRM because of Full Pitched Winding.
The nature of the flux path is same in both the embodiment of the inventions due to the different winding arrangement.
The rectangular slot (4) is provided in the outwardly projecting portion of the said stator (1) to increase the fill factor of winding and also to constrain the flux to follow the said rectangular shape to reduce the iron weight. This not only reduces the iron weight, it also provides better cooling because of increased surface area of the machine.
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Increased air gap area-with increased said pole angle of the stator and rotor facilitates more flux to pass through the said yoke (5). The higher thickness of the said yoke (5) enables to produce the more flux for the same current and same number of turns in the winding.
Said rotor (2) is having axed shaped rotor poles (7) by providing plurality of air grooves (9) provided with the help of punching operation which reduces the manufacturing cost of the said TOtoi (2).
The said rotor (2) also comprises high reluctance path (8) provided between each rotor poles (7) which enables the said rotor poles (7) to be integrally connected but magnetically isolated. This arrangement of said rotor is facilitated by punching operation, thus eliminates the casting process used for manufacturing rotor in prior art and hence reduces the manufacturing cost of said rotor.
The said stator (1) having pturatity of radial outwardYy projecting portion aVso cunstitates groove (10) in the circumference of said stator (1).
The acoustic noise depends on air gap contact area and yoke thickness. Higher yoke (5) thickness provided in the said stator (1) reduces the acoustic noise due to increase in the natural frequency of vibrations. For the same frame size, present invention, full pitched winding switch reluctance machine (FPWSRM) has higher efficiency. The power density of said full pitched winding switch reluctance machine (FPWSRM) is more. The tempetatate rise in full pitched binding swiiteh ieVac\2ffiee -trathhie (FPWSRM) is lowen due to the higher surface area.
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This present invention gives more torque for the same frame size. The advantage of the present invention are, Higher power density, High torque to weight ratio, High Efficiency and low acoustic Noise (Vibration) for the same frame size (same dimensions),Low manufacturing cost ,Lower winding resistance.
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The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof