GB2574450A - Rotor, electric machine and vehicle - Google Patents
Rotor, electric machine and vehicle Download PDFInfo
- Publication number
- GB2574450A GB2574450A GB1809346.8A GB201809346A GB2574450A GB 2574450 A GB2574450 A GB 2574450A GB 201809346 A GB201809346 A GB 201809346A GB 2574450 A GB2574450 A GB 2574450A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rotor
- magnet
- axis
- air pocket
- magnet installation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
- H02K1/2766—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] having a flux concentration effect
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
- H02K2213/03—Machines characterised by numerical values, ranges, mathematical expressions or similar information
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Permanent Field Magnets Of Synchronous Machinery (AREA)
Abstract
A rotor (4, fig 1) for an electric machine (2, fig 1) comprising: a core 8 having an axis of rotation 10 and a plurality of magnetic poles 12 extending radially from the axis, each pole having an axis denoted as a d axis and at least one magnet installation slot 26, wherein the slot comprises a magnet accepting portion 42 having a first width W1 and at least one air pocket portion 44, 46, wherein the pocket has a second width W2 that is greater than the first width W1. The pocket may extend outwardly from the accepting portion towards a rotor periphery 14, wherein the pocket extends at an angle of less than 180° to the magnet accepting portion such that the magnet installation slot has a U or a V-form. The slot may comprise two air pockets extending outwardly from opposing sides of the magnet portion, wherein the two air pockets 50, 52 are of differing lateral areas. Each pole may comprises two or more rows 38, 40 of slots at differing radial distances from the axis of rotation, arranged symmetrically to form a U or V shape. The rotor core may comprise of magnetic laminations. The machine maybe used in an electric or hybrid vehicle powertrain.
Description
Description
Rotor, Electric Machine and Vehicle
The present disclosure relates to a rotor for an electric machine, an electric machine with the rotor and a vehicle including the electric machine.
An electric machine typically includes a rotor including a soft magnetic material and a stator which are separated by a gap allowing relative rotation. Electric current is passed through a coil which creates a magnetic field which interacts with the existing magnetic field causing the coil to rotate. The coil may be mounted on the rotor or the stator depending on the design of the electric motor. An electric machine may be used as a motor to produce rotational motion from an electrical power supply, or as a generator to produce an electric current from rotational motion.
The powertrain of a vehicle may include a battery alone to drive the drive train and propel the vehicle to provide a fully electric vehicle, or, in hybrid vehicles, the powertrain may include two or more energy sources, for example a combustion engine and an electric motor which may be used to drive the drivetrain and propel the vehicle. The hybrid vehicle may be a parallel hybrid or a series hybrid, for example with small combustion engine to drive the drivetrain in the event that the electric source, for example battery, is depleted. An electric machine in a hybrid vehicle may be used in both motor mode to drive the drivetrain and in generator mode, for example in regenerative braking, to produce an electric current which is used to charge the battery.
Electric machines with a high energy efficiency, high torque and high performance and a small size are desirable for various applications including electric vehicles and hybrid vehicles.
According to the invention, a rotor for an electric machine is provided which comprises a rotor core having an axis of rotation and a plurality of magnetic poles extending radially from the axis of rotation. Each magnetic pole has a d axis which denotes the axis of magnetic flux of the magnetic pole and one or more magnet installation slots. The magnet installation slot has a magnet accepting portion having a first width and at least one air pocket portion. The air pocket portion has a second width that is greater than the first width of the magnet accepting portion.
The magnet accepting portion is used to accommodate a permanent magnet so that at least one permanent magnet is buried within each magnetic pole of the rotor core. The permanent magnet may be secured within the magnet installation slot by an adhesive or mechanical clamping, for example. The air pocket portion or portions are in fluid communication with the magnet accepting portion so that the air pocket portion(s) and magnet accepting portion together form a single common slot in the rotor core. The air pocket portion or portions of the magnet installation slot remain unoccupied by the permanent magnet and any attachment means used to attach the permanent magnet in the magnet accepting portion of the magnet installation slot.
The rotor core is typically substantially cylindrical. Each of the plurality of magnetic poles is substantially identical and extends radially from the axis of rotation to the outer periphery of the rotor core and, therefore, has a radial extent. The rotor core also has a q axis which is positioned by an electric angle of 90° from the d axis and may be arranged between immediately adjacent magnetic poles.
The first width and the second width refer to the width of the magnet accepting portion and air pocket portion of the magnet installation slot in a common plane of the rotor core that is perpendicular to the axis of rotation. The first width refers to the shortest distance of the magnet accepting portion in the case of an elongate form, for example a substantially rectangular or arcuate form. The second width refers to the shortest distance of the air pockets portion in the case of an elongate form such as a rectangular or arcuate form.
The width of the air pocket portion can, therefore, be optimised independently of the width of the magnet accepting portion of the magnet installation slot. Consequently, the lateral size and shape of the air pockets as well as their position within the magnetic pole or the rotor can be optimised independently of the size, shape and position of the permanent magnets within the magnetic pole. This also enables the width of the rotor core between the magnet installation slots and between the magnet installation slots and the outer periphery of the rotor core to be optimised independently of the size and shape of the permanent magnet or magnets. Thus a rotor can be provided with the desired combination of properties, for example weight and size, mechanical strength and maximum torque, for a particular application .
The air pocket portion may extend outwardly to a greater radial extent from the magnet accepting portion towards an outer periphery of the rotor body. The air pocket portion may extend at an angle of less than 180° to the magnet accepting portion such that the magnet installation slot has a U form or a V form in plan view.
In some embodiments, the magnet installation slot includes a single air pocket portion which extends from the magnet accepting portion in the radial direction towards the outer periphery of the rotor body. In other embodiments, the magnet installation slot includes two pocket portions, each extending from opposing sides of the magnet accepting portion. Each air pocket portion may extend outwardly to a greater radial extent towards the outer periphery of the rotor body.
In embodiments, in which the magnet installation slot includes two pocket portions extending from opposing ends of the magnet accepting portion, the two air pocket portions associated with the common magnet accepting portion may be of differing lateral area. In some embodiments, the first one of the two air pocket portions may extend from the magnet accepting portion towards the d axis and the second of the two air pocket portions may extend radially outwards towards the outer periphery of the rotor body such that it has a distal end that is positioned at a greater radial distance from the axis of rotation that the magnet accepting portion.
In some embodiments, the magnet installation slot may cross the d axis and be symmetrically arranged about the d axis of the magnetic pole. In embodiments including two magnet installation slots, the two magnet installation slots may be arranged on either side of the d axis and symmetrically about the d axis without crossing the d axis of the magnetic pole.
In some embodiments, each magnetic pole of the rotor core includes two or more rows of magnet installation slots, whereby the two rows are arranged differing radial distances from the axis of rotation, of the rotor core. In embodiments including two or more rows of magnet installation slots, the outermost row with respect to the axis of rotation may include a first magnet installation slot which crosses the d axis and an inner row may include two or more magnet installation slots that are arranged symmetrically about the d axis, without crossing the d axis. In other embodiments, an outer row and one or more inner rows may each include a magnet installation slot that crosses the d axis. In other embodiments, the outer and inner rows may include two or more magnet installation slots that are arranged symmetrically about the d axis without crossing the d axis. The two magnet installation slots of a row may be arranged so as together they form a substantial V shape or U-shape in plan view.
In some embodiments, the air pocket portion of a magnet installation slot of an inner row extends from the magnet accepting portion outwardly towards the outer periphery or circumference of the rotor by a distance such that a portion of the air pocket is arranged at the same radial distance from the axis of rotation as an air pocket portion of a magnet installation slot of the outer row.
The rotor core may be made from a soft magnetic material and may comprise a plurality of soft magnetic laminations or sheets arranged in a stack having a stack direction that extends parallel to the axis of rotation. The soft magnetic lamination may be an iron silicon sheet, for example. The laminations or sheets may be secured together by adhesive, for example, to form the rotor core .
In use, the rotor includes one or more permanent magnets, whereby a permanent magnet is arranged in the magnet accepting portion of one or more of the magnet installation slots of each magnetic pole . The air pocket portion is unoccupied by the permanent magnet such that the second width of the air pocket portion, which is greater than the first width of the magnet accepting portion of the magnet installation slot, is unoccupied by the permanent magnet and thus provides an air pocket. The shape of the permanent magnet may correspond to the shape of the magnet accepting portion, for example bath tub or trapezoidal, or arcuate in plan view.
In some embodiments, at a region between the permanent magnet and the air pocket portion, the radially inward contour of the air packet portion pocket portion is arranged at a greater radial distance from the axis of rotation compared to a radial distance of a radially inward contour of the permanent magnet. In some embodiments, at a region between the permanent magnet and the air pocket portion, a radially inward long side of the air pocket is arranged at a greater radial distance from the axis of rotation compared to a radial distance of a radially inward long side of the permanent magnet. In these embodiments, the permanent magnet can be considered to be radially offset inwardly towards the axis of rotation with respect to the air pocket.
The invention also provides an electric machine, which may be operated as a motor or a generator, the electric machine comprising a stator and the rotor of any one of the embodiments described herein.
The invention also provides a vehicle comprising an electric powertrain, or hybrid powertrain, whereby the powertrain comprises the electric machine including the rotor of any one of the embodiments described herein. The powertrain of the vehicle includes a power source, which may be a source of electricity, for example a battery in the case of an electrically drive powertrain, or a battery and a combustion engine in the case of a series hybrid or a parallel hybrid vehicle.
The rotor according to the invention provides high performance and high torque with high energy efficiency. The topology maximises the reluctance torque component and ensures that the maximum torque can be generated with minimum phase current without compromising the machine's maximum power capability. The magnetic volume is minimised whilst ensuring robustness against the magnetisation and low resulting current during active short-circuit as well as fulfilling the mechanical stability of 5 the rotor up to the maximum allowed speed, including over-speed conditions .
In some embodiments, the rotor may be used in a 48 V starter generator, a 48 V electric traction drive with high power and high 10 energy efficiency for hybrid vehicles, small electric vehicles, plug-in hybrid electric vehicles or robot vehicles, such as people movers.
Embodiments of the invention will now be described with reference 15 to the accompanying drawings.
Figure 1 illustrates a schematic view of an exemplary electric machine with a rotor and a stator.
Figure 2a illustrates a view of a magnetic pole of a rotor for an electric machine according to a first embodiment.
Figure 2b illustrates a view of the magnetic pole of figure 2a with permanent magnets inserted in the rotor.
Figure 3 illustrates a view of a magnetic pole of a rotor for an electric machine according to a second embodiment.
Figure 4 illustrates a view of a magnetic pole of a rotor for electric machine according to a third embodiment.
Figure 5 illustrates a schematic view of a vehicle including an electric machine with a rotor according to any one of the embodiments described herein.
Figure 1 illustrates a schematic view of an exemplary electric machine 2 including a rotor 4 and a stator 6. The rotor 4 has a rotor core 8 having an axis of rotation 10 and a plurality of magnetic poles 12 which extend radially from the axis of rotation 10. The rotor 4 is arranged concentrically within the stator 6 and has a circumference or an outer periphery 14 that is spaced apart from an inner periphery 16 of the stator 6 by an air gap
18. The stator 6 has one or more windings 20 through which current can flow to produce a magnetic field.
The rotor 4 has a plurality of magnetic poles 12 which are substantially identical. Eight magnetic poles 12 are illustrated in Figure 1. However, the rotor is not limited to including eight magnetic poles and may include more or less than eight magnetic poles . Each magnetic pole 12 includes one or more slots 22 in which a permanent magnet 24 is situated. The slots 22 may be called magnet installation slots or magnet insertion slots. Each of the magnetic poles 12 of the rotor core 8 includes an axis denoted as the d axis. The d axis denotes the axis of magnetic flux for the permanent magnet or magnets 24 of each magnetic pole 12 and in some embodiments can be a centre axis of the magnetic pole 12.
The rotor 4 also has a q axis which is deviated from the d axis by an electrical angle of 90°. Each magnetic pole 12 has substantially the same topology and, therefore, the same number, shape and position of the permanent magnets 24 and associated slots 22.
The electric machine 2 may be used as in a motor or generator mode .
The rotor core 8 includes a soft magnetic material and, in some embodiments, may be formed in by a stack of soft magnetic laminations or sheets having a stack direction which extends parallel to the axis of rotation 10 and, therefore, out of the plane of the drawing. The laminations may be secured to one another, for example by an adhesive, to form the rotor core 8.
The arrangement of the magnet installation slot or slots 22 and therefore, the permanent magnets 24, within each magnetic pole 12 of the rotor core 8 can be selected and designed to improve the power density and torque produced by the electric machine 2.
Figures 2 to 4 illustrate embodiments and such arrangements for a single magnetic pole 12 of the rotor 4 and, in particular, illustrate embodiments of the magnet installation slots 22 in the rotor body 8 of the rotor 4. It is to be understood that each of the further magnetic poles of the rotor has the same arrangement. However, the rotor according to any one of the embodiments described herein is not limited to use in an electric machine having the design illustrated in Figure 1.
Figure 2a illustrates a view of one magnetic pole 12 of a plurality of substantially identical magnetic poles of a rotor core 8 according to a first embodiment. The rotor core 8 may be used in an electric machine, such as that illustrated in figure 1. Each magnetic pole 12 includes three magnet installation slots 26, 28,
30. Figure 2b illustrates a view of the magnetic pole 12 of the rotor core 8 with a permanent magnet 32, 34, 36 inserted in each of the magnet installation slots 26, 28, 30.
In the first embodiment, the magnetic pole 12 includes two rows 38, 40 of magnet installation slots. A first outer row 38 is positioned radially outwardly of a second inner row 40 with respect to the axis of rotation 10. A single magnet installation slot 26 is arranged in the outer row 38 which crosses the d axis and is arranged mirror symmetrically about the d axis. The second row 40 includes two magnet installation slots 28, 30 which are arranged symmetrically about and on either side of the d axis such that the magnet installation slots 28, 30 are spaced apart by a portion of the rotor body 8 at the d axis so that neither of the magnet installation slots 28, 30 crosses the d axis.
The magnet installation slot 26 of the outer row 38 includes a central magnet accepting or accommodation portion 42, which extends into a first air pocket 44 and a second air pocket 46 at opposing ends so that the air pockets 44, 46 are in fluid communication with the magnet accepting portion 42 and form a single slot or recess within the rotor core 8. The magnet accepting portion 42 has a width W1 and the each of the air pockets 44, 46 has a width W2 . The width W2 of the air pockets 44, 46 is greater than the width W1 of the magnet accepting portion 42. The magnet accepting portion 42 may be substantially straight and have a bathtub form. The air pockets 44, 46 extend outwardly from the magnet accepting portion 42 towards the circumference 14 of the rotor body 8 to a greater radial extent than the magnet accepting portion 42 and form an angle a (alpha) of less than 180° to the magnet accepting portion such that the magnet installation slot 26 can be considered to have a U-shaped form. The distal ends of the air pockets 44, 46 may be rounded. The air pockets 44, 46 have the same lateral size.
The magnet installation slots 28, 30 of the second row 40 have a mirror symmetrical arrangement about the d axis. The magnet installation slot 28 also includes a central magnet accepting portion 48 which extends into first air pocket 50 and a second air pocket 52 at opposing ends, whereby the first air pocket 50 extends towards the q axis and the second air pocket 52 extends towards the d axis. The magnet accepting portion 48 may be arranged at an inclined angle to the d axis which is less than 180° but more than 90°. The two magnet installation slots 28, 30 may together form a V-shape or a U shape. In this embodiment, the magnet accepting portion 48 is straight rather than curved so that a V-shape is formed. In this embodiment, the air pockets 50, 52 of the magnet installation slot 28 have differing lateral areas. In particular, the first air pocket 50 has a larger lateral area than the second air pocket 52. The first air pocket 50 extends from the magnet accepting portion 48 radially outwardly towards the circumference 14 of the rotor body 8. The first air pocket 50 has a length L2 such that a distal end of the first air pocket 50 is arranged at a radial distance from the axis of rotation 10 on which the air pockets 44, 46 of the magnet installation slot 26 of the outer row 38 are also positioned.
The second magnet installation slot 30 of the inner row 40 also includes a magnet accepting portion 48' with first and second air pockets 50' , 52' . The second magnet installation slot is a mirror image about the d axis of the first magnet installation slot 28 and is also mirror symmetrically arranged about the d axis with respect to the first magnet installation slot 28.
As can be seen in Figure 2b, the permanent magnets 32, 34, 36 have a lateral size and shape such that they can be accommodated in the magnetic accepting portion of the respective magnet installation slot 26, 28, 30. The permanent magnets 32, 34, 36 may be secured in the magnet accepting portion 42, 48, 48' of the respective magnet installation slot 26, 28, 30 by an adhesive or by clamping, for example. As can be seen in Figure 2b, the magnet accepting portions 42, 48, 48' of the magnet installation slots 26, 28, 30 each have a lateral size such that, when the permanent magnet is positioned in the magnet accepting portion 42, 48, 48' , the air pockets 44, 46, 50, 52, 50' , 52' of the magnet installation slots 26, 28, 30 remain unoccupied by the respective permanent magnets 32, 34, 36.
The permanent magnets 32, 34, 36 can be considered to be offset radially inward from the air pockets 44, 46, 50, 52, 50', 52' of the respective magnet installation slot 26, 28, 30 such that at the transition between the permanent magnet 32 and the air pockets 44, 46, the contour of the radially inward side of the air pockets 44, 46 is arranged at a greater radial distance from the axis of rotation 10 compared to a radial distance of radially inward contour of the permanent magnet 32 from the axis of rotation 10. An inwardly facing long side of the permanent magnet 32 is positioned at a smaller radial distance from the axis of the rotation 10 compared to the radial distance from the axis of rotation of the most inwardly positioned long side of the air pocket 44, 46.
The two layer design as illustrated in Figure 2 may be considered to be based on a bathtub design, with two V orientated magnet air pockets in the inner layer. All of the magnets are offset towards the inner radius, or axis of rotation, relative to the pattern of the air gap of the machine. The bridges formed by the material of the rotor next to the air gap of the machine are relatively large which, however, are not reduced significantly due to the layout of the air pockets and their rounded contour and enhance the mechanical stability of the rotor. The pattern of the air pockets is such that the air pocket has a width which is not the same width as the magnets and is not the same as the magnet accepting portion of the magnet installation slot. The width of the air gap is enlarged to the magnets and the magnet accepting portion in order to increase the magnetic resistance for the electromagnetic flux.
The topology of the rotor 4 with the permanent magnets in position in the magnet accepting portions of the slots may be used in an electric machine to maximise the reluctance torque component and ensure that the maximum torque can be generated with minimum phase current without compromising the machine's maximum power capability. The magnetic volume is minimised whilst ensuring robustness against the magnetisation and low resulting current during active short-circuit as well as fulfilling the mechanical stability of the rotor up to the maximum allowed speed, including over-speed conditions.
To summarise, according to the invention, at least one of the magnet installation slots of a magnetic pole of the rotor has an air pocket portion extending from a magnet accepting portion, or two air pocket portions extending from opposing ends of a magnet accepting portion, which have a second width which is greater than the first width of the magnet accepting portion. The first width and the second width lie in a common lateral plane of the rotor core, for example, at the surface of the rotor core. In some embodiments, the second width of the air pocket is the smallest dimension of the pocket which is unoccupied by the permanent magnet. The air pockets extend in a general radial direction outwardly from the permanent magnet and the magnet accepting portion of the slot towards the outer periphery of the rotor body.
The magnet installation slots of the rotor may have forms other than that illustrated in figure 2 and may be arranged in a single row or three or more rows, for example as illustrated in Figures 3 and 4.
Figure 3 illustrates a view of a magnetic pole 12' of a rotor 4' for an electric machine according to a second embodiment. In the second embodiment, each magnetic pole 12' includes a single magnet installation slot 26' which extends across and is symmetrical about the d axis. The magnet installation slot 26' has a central magnet accepting portion 42' and extends into an air pocket 44', 46' at opposing ends. In this embodiment, the magnet accepting portion 42' has a curved or arcuate shape having a width W1 which is less than the width W2 of each of the air pockets 44' , 46' . The non illustrated permanent magnet which is to be secured in the magnet accepting portion 42' has a shape and size corresponding to the magnet accepting portion and is also arcuate .
In some non illustrated embodiments, one or more further rows of magnet installation slots and their associated permanent magnets may be included, each of which has a form similar to that as the magnet installation slot 26', which are arranged radially inward of the magnet installation slot 26' and symmetrically about the d axis . Each of the magnet installation slots may cross the d axis .
Figure 4 illustrates a view of a magnetic pole 12'' of a rotor 4' ' for electric machine according to a third embodiment. In this embodiment, each magnetic pole 12' ' includes three rows 56, 58, 60 of magnet installation slots. The outer row 56 may include a magnet installation slot 26 as in the embodiment illustrated in figure 3 or in figure 2a. The two inner rows 58, 60 may each include two magnet installation slots 62, 64, 66, 68. The two magnet installation slots 62, 64 of the row 58 are arranged mirror symmetrically about the d axis such that each magnet installation slot 62, 64 does not cross the d axis. The magnet installation slots 66, 68 of the third row 60 may have a similar arrangement so that the two magnet installation slots 66, 68 of the third row 60 are arranged mirror symmetrically about the d axis such that each magnet installation slot 66, 68 does not cross the d axis.
The distance between the rows 56, 58, 60 may be the same or may be different.
Each of the magnet installation slots 26, 62, 64, 66, 68 includes a central magnet accepting portion 70 which extends into an air pocket 72, 74 at opposing ends of the magnet accepting portion 70. Each of the air pockets 72, 74 has a width W2 which is greater than the width W1 of the magnet accepting portion 70. In this embodiment, all of the magnet installation slots are substantially arcuate. However, different forms may be used within a magnetic pole. For example the magnet installation slot of the outermost row with respect to he axis of rotation may have a bath tub or trapezoidal form and the magnet installation slots of the inner rows with respect to the axis of rotation may be substantially arcuate.
Figure 5 illustrates a schematic view of a vehicle 100 including one or more electric machines 104 having the rotor according to any one of the embodiments described herein. The vehicle 100 includes one or more power sources such as a battery 102 which supply current to the electric motor 104. The electric machine 104 may be used to drive the drivetrain 106 and therefore the wheels 110 of the vehicle 102 to propel the vehicle 100.
In some embodiments, the vehicle 100 may be an electric vehicle including only a single power source 102, for example in the form of a battery. In this embodiment, the electric machine 104 alone is used to propel the vehicle.
In other embodiments, the vehicle 100 is a hybrid vehicle including two power differing power sources, for example a battery 102 and a combustion engine 108. The combustion engine 108 may be used alone to propel the vehicle 100 or may be used together with the electric motor to propel the vehicle. The combustion engine 108 may be used to provide rotational mechanical energy to the electric machine 104 which is used in a generator mode to charge the battery 104. The electric machine 104 is not limited to being used as part of the drivetrain of a vehicle. For example, the electric machine 104 may also be used as a starter motor for vehicle 100.
The rotor design of the embodiments described herein may be considered to be based on a bathtub design, with two V or U orientated magnet air pockets in an inner layer. All of the magnets are offset towards the inner radius, or axis of rotation, relative to the pattern of the air gap. The bridges formed by the material of the rotor next to the air gap of the machine are relatively large which, in the topology according to the embodiments described herein, does not reduce the due to the layout of the air pockets and rounded contour significantly but enhances the mechanical stability of the rotor. The pattern of the air pockets is such that the air pocket has a width which is not the same width as the magnets and the magnet accepting portion of the magnet installation slot. In particular, the width of the air gap is enlarged to the magnets in order to increase the magnetic resistance for the electromagnetic flux.
The electric machine including the rotor with permanent magnets may be used to generate a torque based on the permanent magnetic flux from the magnets and the reluctance of the motor. The topology of the rotor is a result of a multifunctional optimisation which may include considering the following parameters : maximising shaft torque, maximising shaft power, minimising phase current, minimising current ripple, minimising torque ripple, minimising loss, minimising magnet volume whilst ensuring robustness against the magnetisation and guaranteeing mechanical stability over the operating range.
The rotor may be used to produce a high power density and enhance energy efficiency. The rotor may be used in applications such as low-voltage, high-voltage and 48 voltage power supplies, hybrid and electrically driven vehicles, plug-in hybrid electric vehicles and electric machines, such as a permanent magnet synchronous machine.
References
| 2 4 | electric machine rotor | |
| 5 | 6 | stator |
| 8 | rotor core | |
| 10 | axis of rotation | |
| 12 | magnetic pole | |
| 14 | outer periphery of rotor | |
| 10 | 16 | inner periphery of stator |
| 18 | air gap | |
| 20 | winding | |
| 22 | slot | |
| 24 | permanent magnet | |
| 15 | 26 | magnet installation slot |
| 28 | magnet installation slot | |
| 30 | magnet slot | |
| 32 | permanent magnet | |
| 34 | permanent magnet | |
| 20 | 36 | permanent magnet |
| 38 | outer row | |
| 40 | inner row | |
| 42 | magnet accepting portion | |
| 44 | first air pocket | |
| 25 | 46 | second air pocket |
| 48 | magnet accepting portion | |
| 50 | first air pocket | |
| 52 | second air pocket | |
| 56 | outer row | |
| 30 | 58 | inner row |
| 60 | inner row | |
| 62 | magnet installation slot | |
| 64 | magnet installation slot | |
| 66 | magnet installation slot |
magnet installation slot magnet accepting portion air pocket air pocket
100 vehicle
102 battery
104 electric machine
106 drivetrain
108 combustion engine
110 wheel
Claims (15)
1. A rotor (4) for an electric machine (2) comprising:
a rotor core (8) having an axis of rotation (10) and a plurality of magnetic poles (12) extending radially from the axis of rotation (10), each magnetic pole (12) having an axis denoted as a d axis and at least one magnet installation slot (26), wherein the magnet installation slot (26) comprises a magnet accepting portion (42) having a first width (Wl) and at least one air pocket portion (44, 46), wherein the air pocket portion (44, 46) has a second width (W2) that is greater than the first width (Wl) of the magnet accepting portion (42) .
2. A rotor (4) according to claim 1, wherein the air pocket portion (44; 46) extends outwardly to a greater radial extent from the magnet accepting portion (42) towards an outer periphery (14) of the rotor (4).
3. A rotor (4) according to claim 1 or claim 2, wherein the air pocket portion (44; 46) extends at an angle of less than 180° to the magnet accepting portion (42) and towards the outer periphery (14) of the rotor (4) such that the magnet installation slot (26) has a U-form or a V-form.
4. A rotor (4) according to one of claims 1 to 3, wherein the magnet installation slot (26) comprises two air pocket portions (44, 46) extending from opposing sides of the magnet accepting portion (42) and extending outwardly to a greater radial extent towards the outer periphery (14) of the rotor (4).
5. A rotor (4) according to claim 4, wherein the two air pocket portions (50, 52) are of differing lateral area.
6. A rotor (4) according to one of claims 1 to 5, wherein each magnetic pole (12) comprises two or more rows (38, 40) of magnet installation slots (26; 28; 30) , the two or more rows (38, 40) arranged at differing radial distances from the axis of rotation (10).
7. A rotor (4) according to claim 6, wherein at least an outer row (38) comprises a first magnet installation slot (26) that crosses the d axis.
8. A rotor (4) according to claim 6 or 7, wherein an inner row (40) has two or more magnet installation slots (28, 30) that are arranged symmetrically about the d axis.
9. A rotor (4) according to claim 8, wherein the two magnet installation slots (28, 30) of the inner row are arranged to form a V-shape or a U shape.
10. A rotor (4) according to one of claims 7 to 9, wherein a first air pocket portion (50, 50' ) of the magnet installation slot (28, 30) of the inner row (40) extends outwardly towards the outer periphery (14) of the rotor (4) such that it is arranged at the same radial distance from the axis of rotation as an air pocket portion (44, 46) of a magnet installation slot (26) of the outer row (38).
11. A rotor (4) according to one of claims 1 to 10, wherein the rotor core (8) comprises a plurality of soft magnetic laminations arranged in a stack having a stack direction extending parallel to the axis of rotation (10).
12. A rotor (4) according to one of claims 1 to 11, further comprising a permanent magnet (32) arranged in the magnet
13.
14 .
15.
accepting portion (42) of the magnet installation slot (26), the air pocket portion (44, 46) being unoccupied by the permanent magnet (32), wherein the second width (W2) of the air pocket portion (44, 46) is unoccupied by the permanent magnet (32) .
A rotor (4) according to claim 12, wherein at a region between the permanent magnet (32) and the air pocket portion (44, 46) , a radially inward long side of the air pocket (44, 46) is arranged at a greater radial distance from the axis of rotation (10) compared to a radial distance of a radially inward long side of the permanent magnet (32).
An electric machine (2), comprising a stator (6) and the rotor (4) of one of claims 1 to 13.
A vehicle (100) comprising an electric or hybrid powertrain, the powertrain comprising the electric machine (104) of claim 14.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1809346.8A GB2574450A (en) | 2018-06-07 | 2018-06-07 | Rotor, electric machine and vehicle |
| PCT/EP2019/062714 WO2019233733A1 (en) | 2018-06-07 | 2019-05-16 | Rotor, electric machine and vehicle |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1809346.8A GB2574450A (en) | 2018-06-07 | 2018-06-07 | Rotor, electric machine and vehicle |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB201809346D0 GB201809346D0 (en) | 2018-07-25 |
| GB2574450A true GB2574450A (en) | 2019-12-11 |
Family
ID=62975509
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1809346.8A Pending GB2574450A (en) | 2018-06-07 | 2018-06-07 | Rotor, electric machine and vehicle |
Country Status (2)
| Country | Link |
|---|---|
| GB (1) | GB2574450A (en) |
| WO (1) | WO2019233733A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112467909A (en) * | 2020-11-30 | 2021-03-09 | 珠海格力电器股份有限公司 | Motor rotor, permanent magnet motor and electric automobile |
| CN112928842B (en) * | 2021-01-28 | 2022-05-03 | 重庆长安新能源汽车科技有限公司 | Rotor punching sheet, rotor, permanent magnet synchronous motor and vehicle |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050269888A1 (en) * | 2004-05-24 | 2005-12-08 | Denso Corporation | Internal permanent magnet rotor having improved configuration of magnetic flux barriers |
| US20100052455A1 (en) * | 2008-08-28 | 2010-03-04 | Teco-Westinghouse Motor Company | Permanent-Magnet (PM) Rotors and Systems |
| WO2016147946A1 (en) * | 2015-03-16 | 2016-09-22 | 株式会社 豊田自動織機 | Rotor for rotating electrical machine |
| WO2018095969A1 (en) * | 2016-11-24 | 2018-05-31 | Jaguar Land Rover Limited | Electric machine apparatus |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016073023A (en) * | 2014-09-26 | 2016-05-09 | 東芝三菱電機産業システム株式会社 | Permanent magnet type rotor and permanent magnet type synchronous rotary electric machine |
| GB201510273D0 (en) * | 2015-06-12 | 2015-07-29 | Jaguar Land Rover Ltd | Electric drive motor |
| JP6781536B2 (en) * | 2015-10-02 | 2020-11-04 | 東芝三菱電機産業システム株式会社 | Permanent magnet rotor and permanent magnet rotor |
-
2018
- 2018-06-07 GB GB1809346.8A patent/GB2574450A/en active Pending
-
2019
- 2019-05-16 WO PCT/EP2019/062714 patent/WO2019233733A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050269888A1 (en) * | 2004-05-24 | 2005-12-08 | Denso Corporation | Internal permanent magnet rotor having improved configuration of magnetic flux barriers |
| US20100052455A1 (en) * | 2008-08-28 | 2010-03-04 | Teco-Westinghouse Motor Company | Permanent-Magnet (PM) Rotors and Systems |
| WO2016147946A1 (en) * | 2015-03-16 | 2016-09-22 | 株式会社 豊田自動織機 | Rotor for rotating electrical machine |
| WO2018095969A1 (en) * | 2016-11-24 | 2018-05-31 | Jaguar Land Rover Limited | Electric machine apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| GB201809346D0 (en) | 2018-07-25 |
| WO2019233733A1 (en) | 2019-12-12 |
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