Claims:CLAIMS
We claim:

1. An improved rotor (A) of an line start permanent magnet synchronous motor made of aluminium die casting;
characterized in that
is provided with plurality of inverted “T” orientation permanent magnets (8) positioned on the rotor body symmetrically around a shaft (2) in specified slots made on the rotor body; and
additional plurality of slots (3) are incorporated in the rotor body between the permanent magnets (8) to reduce torque pulsation, improve flux distribution on rotor surface area and improve the saliency ratio thereby improving the efficiency of the motor.

2. The improved motor as claimed in claim 1, wherein eight interior permanent magnets (8) are positioned on the rotor body symmetrically around a shaft (2) in specified slots made on the rotor body.

3. The improved motor as claimed in claim 1, wherein the additional slots (3) incorporated in the rotor body between the permanent magnets (8) are round in shape.

4. The improved rotor as claimed in claim 1, wherein said additional slots (3)are distributed symmetrically around said shaft (2).

5. The improved rotor as claimed in claim 1, wherein the efficiency of said motor increases by 1.5 to 2.0 percentage points.

6. The improved rotor as claimed in claim 1, wherein said rotor (A) is adapted to save about 15-20 % copper and steel laminations in its manufacture process.

7. The improved rotor as claimed in claim 1, wherein said rotor (A) is adapted to fit frame sizes from 100L to 200L of standard induction motors.

8. The improved rotor as claimed in claim 1, wherein said rotor (A) is adapted to fit frame sizes from 100L to 200L of standard induction motors.
9. The improved rotor as claimed in claim 1, wherein said rotor (A) is manufactured in an output range of 1.5 kW to 30 kW.

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V.G PARELKAR
Advocate,(Reg. No. MAH 324/1982)
Partner,
V. A.ASSOCIATES.
Duly Constituted Attorney.
vaassociatesip@gmail.com
022-26160737
Patent Attorney’s Code: IN/PA- 469
Dated: ___ December, 2018.

, Description:INTERIOR MAGNET ROTORS WITH MODIFIED MAGNET CONFIGURATION FOR REDIRECTING FLUX AND IMPROVING EFFICIENCY OF LINE START PERMANENT MAGNET SYNCHRONOUS MOTORS TO IE5 LEVEL.
FIELD OF THE INVENTION
The present invention relates in general to line start permanent magnet motors, and more particularly to interior magnet rotors with modified magnet configuration for redirecting flux and improving overall efficiency of line start permanent magnet synchronous motors.
BACKGROUND AND PRIOR ART
Conventional induction motor or asynchronous motor are AC electric motor in which the electric current in the rotor needed to produce torque that is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor's rotor can be either wound type or squirrel-cage type. An induction motor can be used as an induction generator, or it can be unrolled to form a linear induction motor which can directly generate linear motion.
The Line Start Permanent Magnet Synchronous Motor (LSPMSM) combines a permanent magnet rotor that allows higher motor efficiency during synchronous operation, and an induction motor squirrel cage rotor for starting the motor by connecting it directly to an a.c. source.
The fact that the magnetizing field is generated by the permanent magnets means that no magnetizing current is drawn from the line finally leading to a much higher power factor in full load operation and lower losses in the stator winding. The LSPMSM can replace the common induction motor in many applications, including variable torque applications (fans and pumps driving) and constant torque applications, due to their known torque-speed characteristic.
IE4 efficiency levels have been achieved in LSPMSM’s. IE4 represents the highest energy efficiency whilst IE1 represents the least energy efficiency. In other words, the higher the class number, the higher the motor efficiency. Although there are continuous efforts in improving the design of these motors for redirecting flux, there is need in the industry for LSPMSM motors for higher running efficiency of IE5 levels combined with increased starting torque. The present invention seeks to overcome the drawback of the prior art.
OBJECTS OF THE INVENTION
Accordingly, the primary object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor with efficiency levels of IE5.
Another object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor having improved starting torque.
Yet another object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor with modified magnet configuration for redirecting flux.
Yet another object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor that eliminates the need of multiple drives to increase the efficiency.
Yet another object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor which offers savings in materials and costs.
A further object of the invention is to provide a Line Start Permanent Magnet Synchronous Motor in the same frame size as a standard induction motor with IE5 levels of efficiency, making replacement of old inefficient motors very easy.
How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation.
SUMMARY OF THE INVENTION
An improved rotor of an LSPMS motor is made of aluminium die casting. It is provided with eight interior permanent magnets arranged in an inverted “T” orientation, on the rotor body wherein said permanent magnets are symmetrically arranged around a shaft in specified slots made on the rotor body. Additional round slots are incorporated in the rotor body between the magnets to divert flux and increase efficiency of the motor, by which the efficiency of the motor increases by 1.5 to 2.0 percentage points, i.e. losses reduce by 23 to 25%, so as to achieve IE5 levels.
The rotor saves about 15-20 % copper and steel laminations in its manufacture
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings:-
Figure 1 is a end view of the rotor of an LSPMS motor according to the present invention.
Figure 2 is a photographic end view of the rotor shown in figure 1.
Figure 3 is a photographic side view of the rotor shown in figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Having described the main features of the invention above, a more detailed and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.
In all the figures, like reference numerals represent like features. Further, the shape, size and number of the devices shown are by way of example only and it is within the scope of the present invention to change their shape, size and number without departing from the basic principle of the invention.
Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”, “above” or “below” , “right hand side”, “left hand side” and similar terms , this is strictly referring to an orientation with reference to the apparatus , where the base of the apparatus is horizontal and is at the bottom portion of the figures. The number of components shown is exemplary and not restrictive and it is within the scope of the invention to vary the shape and size of the apparatus as well as the number of its components, without departing from the principle of the present invention.
All through the specification including the claims, the technical terms and abbreviations are to be interpreted in the broadest sense of the respective terms, and include all similar items in the field known by other terms, as may be clear to persons skilled in art. Restriction or limitation if any referred to in the specification, is solely by way of example and understanding the present invention.
Indian patent application no.201621011601A relates to an improved LSPMS rotor, said motor is made of aluminium die casting. It is provided with four interior permanent magnets positioned on the rotor body symmetrically around a shaft in specified slots made on the rotor body. Additional slots are incorporated in the rotor body to create high reluctance paths which improve the efficiency of the motor, by which the efficiency of the motor increases by 0.5 to 1.5 percentage points so as to achieve IE4 levels.
Present invention is an improvement of the aforementioned patent application, wherein it discloses plurality of inverted “T” shaped configuration of magnets to improve the magnetic flux distribution on rotor surface area and plurality of slots to increase saliency in the rotors of Line start permanent magnet motors. The shape and location of the magnets are modified such that it aids in redirecting flux and improves the efficiency of the motor to IE5 levels.

The present invention discloses eight interior permanent magnets arranged in an inverted “T” shaped configuration, on the rotor body wherein said permanent magnets are symmetrically arranged around a shaft in specified slots made on the rotor body. Additional round slots are incorporated in the rotor body between the magnets that increase the saliency ratio in the rotor and increase efficiency of the motor, by which the efficiency of the motor increases by 1.5 to 2.0 percentage points so as to achieve IE5 levels. Power factor is almost unity, leading to further reduction in line current.
The rotor as disclosed in the present invention saves about 15-20 % copper and steel laminations in its manufacture as compared to a conventional IE5 motor. In many cases it is not even possible to achieve IE5 levels in a line start induction motor.
The rotor as disclosed in the present invention, fits frame sizes from 100L to 200L of standard induction motors, making replacement of old inefficient motors very easy. Fig. 1 illustrates an end view of the rotor of an LSPMS motor according to the present invention. Referring to figure 1, the improved rotor (A) of an LSPMS motor is made of aluminium die casting. An arrangement of the interior magnets inside the rotor discloses a central shaft (2), wherein said central shaft (2) is surrounded with plurality of magnets. Further said plurality of magnets are eight interior permanent magnets (8) that are arranged in an inverted “T” shaped configuration, on the rotor body wherein said permanent magnets (8) are symmetrically arranged around a shaft (2) in specified slots made on the rotor body. The improved rotor (A) additional has round slots (3) that are incorporated in the rotor body between the magnets to divert flux and increase the saliency ratio in the Q and D axis (not shown). The increase in saliency ratio thereby improves the motor efficiency and reduces the torque pulsations.
The slots (3), incorporated in the rotor body reduces torque pulsation, improve flux distribution on rotor surface area and improve the saliency ratio, the net effect of which improves the efficiency of the motor by 1.5 to 2.0 percentage points, depending upon the output rating. Due to this improvement, IE5 levels of efficiency as per IEC 60034-30-2 are achieved. These slots (3) are also distributed symmetrically around the axis of the rotor.
Further in order to concentrate the magnetic flux lines and force the magnetic flux in the desired directions, the magnet shape has been changed to an inverted ‘T’ with a round flux redirecting slots which increase the saliency ratio in the rotor, located as shown in fig.1. This reduces the power drawn from the power supply lines and improves the power factor.

It is surprisingly found in the present invention that maximum magnetic flux achieved at the rotor surface is due to the inverted “T” shaped configuration of the interior permanent magnets.

Fig.1 further discloses Location of special arrangement of inverted ‘T’ shaped magnets for a 26 slot 4 Pole motor.

Figure 2 and Fig. 3 are photographic end view and side view of the rotor shown in figure 1 respectively. Fig.2, like wise denotes the geometric arrangement of inverted “T” shaped configuration of the interior permanent magnets as disclosed in the Fig.1. The T shaped slots as disclosed in the present invention are designed such that normal aluminium pressure die casting of the rotor is not affected, thus keeping the usual rotor manufacturing process the same. Thus keeping the manufacturing cost at the lowest.

The present invention also leads to material and cost savings. In order to achieve similar increase in efficiency, about 15-20 % more copper and steel laminations would have had to be added in its manufacture according to prior art practices. In many cases it is not even possible to achieve IE5 levels in a line start induction motor.
This invention makes it possible to achieve high motor efficiencies in the same frame size as a standard induction motor of the prior art, making replacement of old inefficient motors very easy.

Motors according to the present invention have been designed and made in the output range from 1.5 kW to 30 kW in frame sizes from 100L to 200L.
Advantages:
The main non-limiting advantages of the invention are listed below.
- It improves the efficiency of the LSPMS motors by 1.5 to 2.0 percentage points, i.e. losses reduce by 23 to 25%, over IE4 levels, depending upon the output rating.
- IE5 levels of efficiency as per IEC 60034-30- 2are achieved by these motors.
- It leads to material and cost savings, by about 15-20 % of copper and steel laminations. In many cases it is not even possible to achieve IE5 levels in a line start induction motor.
- This invention makes it possible to achieve high motor efficiencies in the same frame sizes as standard induction motors available in the market, making replacement of old inefficient motors very easy.
- These motors can be made in the output range from 1.5 kW to 30 kW in frame sizes from 100L to 200L.

The present invention has been described with reference to some drawings and a preferred embodiment purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.