DESC:NOVEL PERMANENT MAGNET ASSISTED SYNCHRONOUS RELUCTANCE ROTOR
TECHNICAL FIELD
[0001] The present invention relates to permanent magnet assisted synchronous reluctance rotors used in permanent magnet motors as prime movers for electric vehicles. Specifically, the double layer permanent magnet assisted synchronous reluctance rotor having design features to increase reluctance torque thereby reducing the need for permanent magnet content.

BACKGROUND
[0002] At present, the problem that the wide application of the synchronous reluctance motor is restricted is that the power factor is low and a large-capacity frequency converter is needed to be matched for driving
[0003] CN103280904A discloses a double-layer V-shaped built-in permanent magnet motor rotor for an electric automobile. Multiple groups of permanent magnet slots which are radially arranged in an inner layer and an outer layer are uniformly arranged on the iron core of the rotor at intervals along the circumferential direction; one or more V-shaped magnetized stripy magnetic steel is embedded in each permanent magnet slot. By virtue of the optimization of structures such as the angle of polar arc of inner-layer V-shaped magnetic steel, the included angle of outer-layer V-shaped magnetic steel, the width proportion of the inner-layer magnetic steel to the outer-layer V-shaped magnetic steel and the included angle of the outer layer forcipated permanent magnet slot and the outer-layer magnetic steel, the air-gap flux density waveform is more approximate to the sinusoidal distribution, the harmonic component is reduced, the air-gap field waveform of the motor is improved, the fundamental wave frequency of spline torque fluctuation is improved, the spline fundamental wave and the ultra harmonics torque amplitude value are reduced, the torque fluctuation caused by splines is reduced, and the synthesis torque fluctuation of the motor is greatly reduced; and meanwhile, the reluctance torque is obviously increased, the salient pole rate and flux weakening speed expanding capability of the motor are improved, a constant-power speed range wider than that of a surface-mounted permanent magnet motor can be obtained, and the driving requirement of electric and hybrid automobiles can be met.
[0004] WO20161889445A1 discloses a synchronous reluctance motor (1) assisted by permanent magnets comprises a stator (2) provided with stator windings (6), for generating a magnetic flux, which has a circular central seat (4) to house a cylindrical shaped rotor (3) suitable for being actuated in rotation about an axis of rotation, wherein the rotor (3) comprises internal slots (10), for housing respective permanent magnets (11), and wherein the internal slots (10) and the permanent magnets (11) are curvilinear shaped in order to optimise the magnetic interaction between the rotor (3) and the stator windings (6).

OBJECTS OF THE INVENTION
[0005] It The object of the invention is to remove the above drawbacks in the available technologies.
[0006] An object of the present invention is to provide a double layer permanent magnet assisted synchronous reluctance rotor having design features to increase reluctance torque thereby reducing the need for permanent magnet content.

SUMMARY
[0007] The present invention relates to permanent magnet assisted synchronous reluctance rotors used in permanent magnet motors as prime movers for electric vehicles. Specifically, the double layer permanent magnet assisted synchronous reluctance rotor having design features to increase reluctance torque thereby reducing the need for permanent magnet content. The present invention proposes elliptical shaped barrier profiles to hold magnets which will reduce q-axis flux and increases output torque.
[0008] In one embodiment, A permanent magnet assisted synchronous reluctance rotor comprising a rotor core (101), a plurality of inner slots (102), having an elliptical shape, radially formed on the rotor core, a plurality of outer slots (103), having an elliptical shape, radially formed on the rotor core, a plurality of permanent magnets (104) placed within the plurality of inner slots and the plurality of outer slots.
[0009] In another aspect of the invention, the permanent magnet assisted synchronous reluctance rotor, wherein each of the plurality of outer slots (103) are radially aligned with one of the plurality of inner slots (102).
[0010] In another aspect of the invention, The permanent magnet assisted synchronous reluctance rotor as, wherein the concave curve of the elliptical shape of the plurality of inner slots (102) and the plurality of outer slots (103) are facing outwards from the centre of the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows a top view of permanent magnet assisted synchronous reluctance rotor.
[0012] FIG. 2 shows a section of top view of permanent magnet assisted synchronous reluctance rotor.
[0013] FIG 3 shows a sectional view of the permanent magnet assisted synchronous reluctance rotor.

DETAILED DESCRIPTION
[0014] A synchronous motor is an AC electrical engine where the rotation of the shaft is at the same the frequency of the electrical supply. The synchronous motor comprises of a stator and a rotor where the rotor can have electromagnetic coils or permanent magnets. The stator which is made of electromagnetic coil windings are placed around the rotor which is mounted on the motor shaft.
[0015] Electromagnets are used as the stator of synchronous motors, creating a magnetic field that spins in time with the oscillations of the current. The rotor with permanent magnets or electromagnets rotates at the same rate as the stator field, resulting in the second synchronised rotating magnet field.
[0016] Reluctance motors have a rotor consisting of a solid steel casting with projecting (salient) toothed poles. To minimise torque ripple and to prevent the poles from all aligning simultaneously—a position that cannot create torque—there are typically fewer rotor poles than stator poles. When the poles are aligned with the (spinning) magnetic field of the stator, the size of the air gap in the magnetic circuit, and therefore the reluctance, is smallest, and grows with the angle between them. This produces a torque that pulls the rotor into alignment with the stator field's closest pole.
[0017] A permanent-magnet synchronous motor (PMSM) uses permanent magnets embedded in the steel rotor to create a constant magnetic field. The stator carries windings connected to an AC supply to produce a rotating magnetic field (as in an asynchronous motor). At synchronous speed the rotor poles lock to the rotating magnetic field. Permanent magnet synchronous motors are similar to brushless DC motors.
[0018] In one embodiment, a permanent magnet assisted synchronous reluctance rotor comprising a rotor core (101), a plurality of inner slots (102), having an elliptical shape, radially formed on the rotor core, a plurality of outer slots (103), having an elliptical shape, radially formed on the rotor core, a plurality of permanent magnets (104) placed within the plurality of inner slots and the plurality of outer slots.
[0019] In another aspect of the invention, the permanent magnet assisted synchronous reluctance rotor, wherein each of the plurality of outer slots (103) are radially aligned with one of the plurality of inner slots (102).
[0020] In another aspect of the invention, The permanent magnet assisted synchronous reluctance rotor as, wherein the concave curve of the elliptical shape of the plurality of inner slots (102) and the plurality of outer slots (103) are facing outwards from the centre of the rotor.
[0021] The elliptical shape of the plurality of inner slots (102) and the plurality of outer slots (103) is the inventive feature of the present invention. The elliptical shape helps in reducing the amount of permanent magnet required in producing the same torque.
[0022] The elliptical shape of the slots also known as the barrier profiles helps in reducing the q flux and increase the torque.
[0023] The associated angles a, ß, ?, d, ? determine the curvature of the elliptical shape and can be varied according to the rating of the motor and its intended application.
,CLAIMS:We claim:

1) A permanent magnet assisted synchronous reluctance rotor comprising:
a rotor core (101);
a plurality of inner slots (102), having an elliptical shape, radially formed on the rotor core;
a plurality of outer slots (103), having an elliptical shape, radially formed on the rotor core;
a plurality of permanent magnets (104) placed within the plurality of inner slots and the plurality of outer slots.

2) The permanent magnet assisted synchronous reluctance rotor as claimed in claim 1, wherein each of the plurality of outer slots (103) are radially aligned with one of the plurality of inner slots (102).

3) The permanent magnet assisted synchronous reluctance rotor as claimed in claim 1, wherein the concave curve of the elliptical shape of the plurality of inner slots (102) and the plurality of outer slots (103) are facing outwards from the centre of the rotor.

Dated this 30th day of September 2022

Rahul Salhotra
Agent for the Applicant [IN/PA-522]