DESC:PERMANENT MAGNET SYNCHRONOUS RELUCTANCE MOTOR FOR ELECTRIC VEHICLE
CROSS REFERENCE TO RELATED APPLICTIONS
The present application claims priority from Indian Provisional Patent Application No. 202221040547 filed on 15/07/2022, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
Generally, the present disclosure relates to a permanent magnet synchronous reluctance motor. Particularly, the present disclosure relates to a permanent magnet synchronous reluctance motor with star-point connection outside stator assembly.
BACKGROUND
Recently, traction motors are increasingly being used due to adoption of electric vehicles. AC motors are one of the good options to serve as traction motor in electric vehicles due to their high performance and efficiency. The permanent magnet synchronous motor (PMSM) has a higher efficiency. However, their drawbacks include eddy current loss at high speed, and a reliability risk because of the possible breaking and demagnetization of magnets due to higher temperature. On the other hand, the reluctance motors (RM) can deliver high power density at low cost, making them attractive for electric automobile applications; however, these motors experience high torque ripple when operated at low speed, and subsequent noise due to torque ripple.
Permanent magnet Synchronous reluctance motor (PMSRM) comes out to be a viable option which combines the advantages of Permanent magnet synchronous motor (PMSM) and Reluctance motor (RM), thus delivering high power density, high efficiency, and wide speed regulation range, while maintaining low torque ripples and high reliability factor.
However, it is worth noting that, like the other motors, the stator of the permanent magnet synchronous reluctance motor will be subjected to heat produced due to ohmic losses occurring in the stator windings. These ohmic losses occurring in the stator winding is one of the major sources of heat being produced in the motor. Due to such heating, the motor magnets may experience various problems such as magnet demagnetisation or even magnet breakage. Moreover, a hotspot is generated at a centre point or neutral point of star connection or a star-point connection, which further deteriorate the motor. Hence, there lies a need to extract heat from stator winding, more importantly from the start-point connection of the stator winding. The process of heat extraction from the star-point comes out to be very complicated. In conventional ways, star-point cooling or stator winding cooling is performed using non-conductive cooling liquid which is very expensive and complicated. It further increases the repair and maintenance cost of the motor.
Therefore, there exists a need for permanent magnet synchronous reluctance motor with efficient heat extraction from the stator winding that overcomes the one or more problems associated with the conventional star-point connection permanent magnet synchronous reluctance motor as set forth above.
SUMMARY
An object of the present disclosure is to provide a permanent magnet synchronous reluctance motor with improved heat extraction from the motor winding.
In accordance with an aspect of the present disclosure, there is provided permanent magnet synchronous reluctance motor. The motor comprises a rotor assembly, a stator assembly, and a motor casing, wherein the motor casing comprises a first terminal box, a second terminal box, a front-end cover and a rear-end cover. The second terminal box comprises a star-point connection located outside the stator assembly.
The present disclosure provides a permanent magnet synchronous reluctance motor with increased heat extraction from the stator. Advantageously, the disclosed motor provides efficient heat extraction from the stator assembly due to the location of star-point connection outside the motor casing. Furthermore, the disclosed motor would be advantageous in terms of eliminating hotspots in the stator assembly. Advantageously, the disclosed motor can be subjected to various electrical testing and maintenance without opening the motor casing. Such configuration would improve the serviceability of the motor. Moreover, the disclosed motor is compact in size due to efficient utilization of the space inside the motor casing.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figure 1 illustrates an exploded view of a permanent magnet synchronous reluctance motor, in accordance with an embodiment of the present disclosure.
Figure 2a and 2b illustrates a front perspective view and a rear perspective view of rotor assembly, respectively, in accordance with an embodiment of the present disclosure.
Figure 3 illustrates an exploded view of a permanent magnet synchronous reluctance motor with star-point connection outside stator assembly, in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a motor of an electric vehicle and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the terms ‘electric motor’, ‘motor’, ‘permanent magnet synchronous reluctance motor’, ‘PMSR motor’, ‘IPM-SynRM’ and ‘PMSRM’ are used interchangeably and refer to electric motors capable of being implemented in an industrial or automobile application, such as on the work machine or other vehicle. The permanent magnet synchronous reluctance motor is a type of hybrid electric motor that combines the features of Permanent Magnet Synchronous Motor (PMSM) and Reluctance Motor (RM). The PMSRM has permanent magnets in the rotor, which generates a constant magnetic field, and the PMSRM relies on the principle of magnetic reluctance to create a rotating field within the motor. It would be appreciated that combination of technologies allows the PMSRM to achieve higher efficiency and better performance than other types of electric motors. In general, the stator of the PMSRM typically contains three-phase windings, which are used to generate alternating current that powers the electric motor. Typically, the rotor is made of iron or other magnetic materials, contains the permanent magnets that generate the magnetic field. It would be appreciated that the PMSRM can be modified to comprise active cooling system, such as a liquid cooling system. It would be appreciated that such cooling system would employ a coolant liquid circulating through the well-defined coolant flow paths (such as stator jackets) inside the motor to dissipate the heat generated by the electric motor during operation.
As used herein, the terms ‘electric vehicle’, ‘EV’, and ‘EVs’ are used interchangeably and refer to any vehicle having stored electrical energy, including the vehicle capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source. Additionally, it is to be understood that the ‘electric vehicle’ as used herein includes electric two-wheeler, electric three-wheeler, electric four-wheeler, electric pickup trucks, electric trucks and so forth.
As used herein, the terms ‘rotor’ and ‘rotor assembly’ are used interchangeably and refer to the rotating part of the motor which is typically made of iron or other magnetic materials. It contains the permanent magnets and the reluctance winding that generate the magnetic field used to drive the rotor. The rotor converts electrical energy supplied to the stator into mechanical energy.
As used herein, the terms ‘stator’ and ‘stator assembly’ are used interchangeably and refer to the stationary part of a motor which provides a magnetic field that drives the rotating armature. The stator may act as a field magnet.
As used herein, the term “motor casing” is used to refer to the outer body of a motor enclosure made of up aluminium, which holds the entire motor body. The motor casing provides mechanical support, protection, and insulation for the motor's electrical and magnetic components.
As used herein, the term “terminal boxes” is used to refer to specific enclosures or compartments located on the motor housing that house the electrical connections and terminals. The terminal boxes provide a convenient and organized means to connect the motor's windings to the external power supply and control system. The terminal boxes comprise a first terminal box and a second terminal box.
As used herein, the terms “front-end cover”, “rear-end cover” and “end cover” are used to refer to the protective component or enclosure that cover ends of the motor. “Front-end cover” and “rear-end cover” refers to the front-end and the rear-end of the motor casing structure respectively. It would be appreciated that the person skilled in the art would understand the front-end cover as motor casing structure fixed at the frontal end of the electric motor where a mechanical load is connected to the motor shaft of the electric motor. Similarly, the rear end cover should be understood as motor casing structure fixed at the rear end of the electric motor with reference to the connection of the load to the motor shaft of the electric motor.
As used herein, the term “motor shaft”, “shaft” and “rotor shaft” are used interchangeably and refer to a cylindrical rotating component of the motor that transmits mechanical power from the motor to the driven load. The motor shaft extends from the rotor and protrudes out of the motor casing.
As used herein, the terms “star-point”, “star-point connection” are used interchangeably and refer to a specific electrical configuration used for connecting the motor windings wherein the ends of the windings are connected together to form a common point connection or neutral point. Conventionally, the star-point is merged inside the windings. It is to be understood that in a three-phase winding comprising 3 phases as A, B and C, one end of each of the three winding sets (A, B, and C) is connected together at a common point, forming the star or neutral point. The other ends of the windings are connected to the power supply or control system. It would be appreciated that the star point connection creates a neutral point that has voltage potential close to zero because the voltages of the three winding sets, which are 120 degrees out of phase with each other, sum up to zero at the neutral point. The star-point connection advantageous in terms of voltage and current balance, reduced harmonic distortion, and better control of motor performance. It also simplifies the motor's electrical connection to the power supply and facilitates the use of standard three-phase electrical systems.
As used herein, the term “rotor stack” refers to rotor core that houses the components associated with the rotor of the motor.
As used herein, the term “cooling jacket” that surrounds the stator assembly to facilitate cooling and heat dissipation. The cooling jacket comprises spiral channels through which a cooling medium, such as air or a liquid coolant, flows to remove excess heat generated during motor operation.
Figure 1, in accordance with an embodiment describes a perspective view of a permanent magnet synchronous reluctance motor 100. The motor 100 comprises a rotor assembly 102, a stator assembly 104, and a motor casing 106, wherein the motor casing 106 comprises a first terminal box 108, a second terminal box 110, a front-end cover 112 and a rear-end cover 114. The second terminal box 110 comprises a star-point connection 116 located outside the stator assembly 104.
The present disclosure provides a permanent magnet synchronous reluctance motor 100 with increased heat extraction from the stator assembly 104. Advantageously, the disclosed motor 100 provides efficient heat extraction from the stator assembly 104 due to the location of star-point connection 116 outside the motor casing 106. Furthermore, the disclosed motor 100 would be advantageous in terms of eliminating hotspots from the stator assembly 104. Advantageously, the disclosed motor 100 can be subjected to various electrical testing and maintenance without opening the motor casing 106. Such configuration would improve the serviceability of the motor 100. Moreover, the disclosed motor 100 is compact in size due to efficient utilization of the space inside the motor casing 106.
Figure 2a and 2b, in accordance with an embodiment describes a front perspective view and a rear perspective view of the rotor assembly 102, respectively. The rotor assembly 102 comprises a motor shaft 118, a rotor stack 120 comprises a stack front-end and a stack rear-end, a plurality of magnets enclosed in the rotor stack 120, a pair of magnet stoppers 122a & 122b, a pair of rotor cir-clips 124a & 124b, and a pair of bearings 126a & 126b. It is to be understood that the stack front-end refers to an end of the rotor stack 120 located towards the front end of the motor casing 106. Similarly, the stack rear-end refers to an end of the rotor stack 120 located towards the rear end of the motor casing 106. Furthermore, the plurality of magnets are enclosed in the rotor stack 120. The plurality of magnets are crucially positioned in the rotor stack 120 to generate the magnetic field required for operation of the motor 100. The magnet stoppers 122a and 122b are placed over the magnets towards the stack front-end 120a and stack rear-end 120b, respectively, to securely hold the plurality of magnets in the intended position. Beneficially, the magnet stoppers 122a & 122b maintains the desired magnetic field configuration during the operation of the motor 100 by securely holding the plurality of magnets in the intended position. Furthermore, the pair of rotor cir-clips 124a & 124b are used to secure the rotor in place within the motor housing. It would be appreciated that the rotor cir-clips 124a & 124b are installed in grooves in the motor shaft 118, and exert a radial force to hold the rotor assembly 102 in place. Furthermore, the pair of bearings 126a & 126b support the rotor assembly 102 and allows free rotation of the same within the stator assembly 104.
In an embodiment, the pair of magnet stoppers 122a & 122b comprises a plurality of air fins configured to create turbulence in stagnant air between the rotor assembly 102 and the stator assembly 104. It is to be understood that during the operation of the motor 100, the rotation of the rotor assembly 102 would result in the rotation of the air fins located on the pair of magnet stoppers 122a & 122b. Beneficially, such rotation of the air fins would create turbulence in stagnant air between the rotor assembly 102 and the stator assembly 104 resulting in cooling of the rotor assembly 102.
In an embodiment, (referring to figure 1) the first terminal box 108 comprises electrical connections between the motor 100 and a power pack. As used herein, the term “power pack” refers to refers to multiple individual battery cells connected together to provide electrical energy for the operation of the motor 100. The power pack is designed to store electrical energy and supply it as needed to various devices or systems. Furthermore, the power pack may include additional circuitry, such as a battery management system (BMS), to ensure the safe and efficient charging and discharging of the battery cells. Beneficially, the first terminal box 108 ensures safety of electrical connections established between the motor 100 and the power pack.
In an embodiment, (referring to figure 1) the motor casing 106 comprises spiral fins 128 and wherein the spiral fins 128 are concentric to the motor shaft 118. Beneficially, the spiral fins 128 increase the surface area of the motor casing 106 leading to better cooling of the motor 100.
In an embodiment, (referring to figure 1) the motor 100 comprises a motor shaft position sensor 130, located on the front-end cover 112, wherein the motor shaft position sensor 130 comprises a sensor circuit 130a and a target fan 130b. As used herein, the terms “motor shaft position sensor”, “shaft position sensor”, and “position sensor” refers to a device used to determine the position and speed of the motor shaft 118 accurately. Beneficially, the motor shaft position sensor 130 provides feedback information to a motor control system, allowing for precise control of operation of the motor 100. It is to be understood that the position sensor 130 operates based on the principle of measuring angular displacement. The position sensor 130 detects the rotational movement of the motor shaft 118 and converts it into electrical signals that indicate the shaft's position relative to a reference point. Furthermore, the sensor circuit 130a stays stationary and the target fan 130b rotates with the motor shaft 118 to detect the position of the motor shaft 118. Specifically, in an embodiment, the target fan 130b is mounted on the motor shaft 118. Beneficially, the target fan 130b rotates with the motor shaft 118 and enable determination of position of the motor shaft 118. Furthermore, the position sensor 130 is located on the front-end cover 112. Beneficially, such location of the position sensor 130 on the front-end cover 112 would enable effective utilization of the available space in the motor 100. In an alternative embodiment, the position sensor 130 is located on the rear-end cover 114. Furthermore, it is to be understood that the sensor circuit 130a and the target fan 130b may be mounted in any order in front of each other as necessitated by the design of motor 100.
In an embodiment, (referring to figure 1) the motor 100 comprises a cooling jacket 132 placed between the motor casing 106 and the stator assembly 104. Specifically, the cooling jacket 132 comprises a spiral channel 134 concentric to the stator assembly 104, wherein the spiral channel 134 is configured to create a path for circulation of coolant. Beneficially, the cooling jacket 132 facilitates heat extraction from the stator assembly 104. It is to be understood that the coolant enters from one end of the spiral channel 134, travels through the spiral channel 134 absorbing heat from the stator assembly 104 and exits from another end of the spiral channel 134.
Figure 3, in accordance with an embodiment describes a perspective view of a permanent magnet synchronous reluctance motor 100 with the star-point connection 116 located outside the stator assembly 104. It is to be understood that to create the star-point connection 116, three ends of the 3-phase winding are fixed on a metal strip creating a neutral point inside the second terminal box 110. Beneficially, the star-point connection 116 located outside the stator assembly 104 enables efficient cooling of the stator assembly 104. Furthermore, the star-point connection 116 located outside the stator assembly 104 eliminates hotspots from the stator assembly 104. It is to be understood that the star-point connection 116 located outside the stator assembly 104 would result in uniform heating (without any hotspots) inside the stator assembly 104, thus, resulting in uniform cooling of the stator assembly 104 via the cooling jacket 132. Furthermore, the star-point connection 116 located outside the stator assembly 104 would create division of heat between inside and outside of the stator assembly 104.
In an embodiment, the second terminal box 110 is configured to provide direct access to the star-point connection 116. Furthermore, the second terminal box 110 may comprise a cap, which may be opened to physically access the star-point connection 116. Beneficially, such physical access to the star-point connection enables electrical testing of the motor winding without opening the motor casing 106. The electrical testing may include insulation resistance test, resistance measurement, efficiency measurement, harmonic analysis and so forth.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combination of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

,CLAIMS:WE CLAIM:
1. A permanent magnet synchronous reluctance motor (100), comprising:
- a rotor assembly (102);
- a stator assembly (104); and
- a motor casing (106), wherein the motor casing (106) comprises a first terminal box (108), a second terminal box (110), a front-end cover (112) and a rear-end cover (114),
characterized in that the second terminal box (110) comprises a star-point connection (116) located outside the stator assembly (104).
2. The motor (100) as claimed in claim 1, wherein the rotor assembly (102) comprises a motor shaft (118), a rotor stack (120) comprising a stack front-end and a stack rear-end, a plurality of magnets enclosed in the rotor stack (120), a pair of magnet stoppers (122a, 122b), a pair of rotor cir-clips (124a, 124b), and a pair of bearings (126a, 126b).
3. The motor (100) as claimed in claim 2, wherein the pair of magnet stoppers (122a, 122b) comprises a plurality of air fins configured to create turbulence in stagnant air between the rotor assembly (102) and the stator assembly (104).
4. The motor (100) as claimed in claim 1, wherein the first terminal box (108) comprises electrical connections between the motor (100) and a power pack.
5. The motor (100) as claimed in claim 1, wherein the motor casing (106) comprises spiral fins (128) and wherein the spiral fins (128) are concentric to the motor shaft (118).
6. The motor (100) as claimed in claim 1, wherein the motor (100) comprises a motor shaft position sensor (130), located on the front-end cover (112), wherein the motor shaft position sensor (130) comprises a sensor circuit (130a) and a target fan (130b).
7. The motor (100) as claimed in claim 6, wherein the target fan (130b) is mounted on the motor shaft (118).
8. The motor (100) as claimed in claim 1, wherein the motor (100) comprises a cooling jacket (132) placed between the motor casing (106) and the stator assembly (104).
9. The motor (100) as claimed in claim 8, wherein the cooling jacket (132) comprises a spiral channel (134) concentric to the stator assembly (104), wherein the spiral channel (134) is configured to create a path for circulation of coolant.
10. The motor (100) as claimed in claim 1, wherein the second terminal box (110) is configured to provide direct access to the star-point connection (116).