CN113629903A

CN113629903A - High-speed permanent magnet motor

Info

Publication number: CN113629903A
Application number: CN202110914410.7A
Authority: CN
Inventors: 王凤翔
Original assignee: Shanghai Tongci Special Motor Technology Co ltd; Shanghai Tongji & Nanhui Hi Tech Park Co ltd
Current assignee: Shanghai Tongci Special Motor Technology Co ltd; Shanghai Tongji & Nanhui Hi Tech Park Co ltd
Priority date: 2021-08-10
Filing date: 2021-08-10
Publication date: 2021-11-09

Abstract

The invention discloses a high-speed permanent magnet motor, which comprises a machine shell, a stator core and a rotor, wherein the machine shell is arranged around the outer side of the stator core, the stator core is arranged around the rotor, the stator core consists of a plurality of external teeth, a yoke and a plurality of internal teeth, each external tooth and each internal tooth are aligned and distributed on two sides of the yoke, one end of each external tooth is positioned on the yoke, the other end of each external tooth is adjacent to the machine shell, the other end of each internal tooth is adjacent to the rotor, an external groove is formed between every two adjacent external teeth, an internal groove is formed between every two adjacent internal teeth, a stator winding coil is wound on the yoke, the two ends of the stator winding coil are respectively positioned in the external groove and the internal groove, and the stator winding is not filled with the external groove and the internal groove, so that the residual spaces of the external groove and the internal groove respectively form an axial external ventilation channel and an axial internal ventilation channel for heat dissipation. The high-speed permanent magnet motor has the advantages of good heat dissipation performance, small loss and less heat productivity.

Description

High-speed permanent magnet motor

Technical Field

The present invention relates to permanent magnet motors, and more particularly to a high speed permanent magnet motor.

Background

The high-speed motor has high rotating speed and high power density, and the structural size of the high-speed motor is far smaller than that of a medium-low speed motor with the same output power, so that the material can be effectively saved. The high speed motor may be directly connected to the prime mover or load, eliminating the need for a conventional mechanical transmission, thereby reducing noise and improving transmission system efficiency. The application fields of high-speed motors are more and more extensive, such as high-speed grinding machines and other processing machines, high-speed flywheel energy storage systems, high-speed centrifugal compressors and blowers adopted in natural gas delivery and sewage treatment, and high-speed generators driven by gas turbines used in distributed power supply systems. The permanent magnet motor has the advantages of high force energy density, high efficiency, brushless performance and the like, and is the main structural form of the high-speed motor.

However, high speed and high power density pose new challenges for the design of high speed permanent magnet motors: (1) high speed rotation requires sufficient strength and rigidity of the motor rotor. The strength characteristics of the rotor material limit the outer diameter of the permanent magnet rotor, while the stiffness requirements of rotor dynamics limit the length of the rotor. When the outer diameter of the rotor and the effective length of the iron core are not changed, how to shorten the length of the rotor meets the requirement of the dynamic characteristic of the rotor, and the method becomes one of key technologies of the design of a high-speed permanent magnet motor; (2) the high power density and the reduction of loss density and heat dissipation area of the high-speed permanent magnet motor are brought, how to reduce the loss of the rotor and adopt an effective heat dissipation mode to ensure that the permanent magnet rotor does not lose magnetism due to overheating is another key technology for designing the high-speed permanent magnet motor.

For example, chinese publication No. CN 203086307U discloses a permanent magnet synchronous motor with a ventilation structure in the prior art. In order to solve the heat dissipation problem of the rotor and the stator, the patent adopts the technical scheme that a non-magnetic material baffle is arranged between permanent magnets along the axial direction of a rotor rotating shaft and used for fixing the axial positions of the permanent magnets and enabling the permanent magnets in the axial direction to have certain intervals, namely, air channels are formed between the permanent magnets which are spaced in the axial direction in the radial direction; radial vent holes communicated with the air duct between the permanent magnets are radially formed in corresponding positions of the magnetic steel grooves and the magnetism isolating sleeves corresponding to the lower part of the air duct between the permanent magnets; the rotor rotating shaft is a hollow rotating shaft; the hollow rotating shaft is internally provided with axial vent holes with two through ends, and is also provided with a plurality of rows of radial vent holes along the axial direction of the rotating shaft, the radial vent holes of the hollow rotating shaft are distributed at equal intervals in each row in the axial direction of the rotating shaft, and are distributed at equal angles in each row in the radial direction of the rotating shaft; the axial vent hole of the hollow rotating shaft is communicated with the radial vent hole of the hollow rotating shaft; the radial vent hole of the magnetism isolating sleeve corresponds to and is communicated with the radial vent hole of the hollow rotating shaft; the stator core is also provided with through radial ventilation holes, and the positions of the radial ventilation holes correspond to the ventilation channels between the permanent magnets. And fans are respectively arranged on two sides of two end faces of the rotor, the wind directions of the fans at the two ends of the rotor are opposite, wind covers are arranged at two end parts of the stator coil and above the fans at the two sides of the rotor, and the wind covers are fixedly connected to the base. ". However, the structure of the permanent magnet synchronous motor is complex and is not suitable for a high-speed permanent magnet motor.

The invention provides a new design scheme of a stator core and a winding of the high-speed permanent magnet motor aiming at the key technology of the high-speed permanent magnet motor design, and the feasibility and the effectiveness of the stator core and the winding are verified through a prototype.

Disclosure of Invention

The invention aims to provide a high-speed permanent magnet motor which not only meets the requirements of high speed and high power density, but also has the characteristic of excellent heat dissipation performance. In order to achieve the purpose of the invention, the invention adopts the following technical scheme.

A high-speed permanent magnet motor comprises a machine shell, a stator core and a rotor, wherein the machine shell is arranged around the outer side of the stator core, the stator core is arranged around the rotor, the stator core is composed of a plurality of external teeth, a yoke and a plurality of internal teeth,

wherein each outer tooth and each inner tooth are aligned on both sides of the yoke with one end thereof being located on the yoke, the other end of the outer tooth being adjacent to the casing, the other end of the inner tooth being adjacent to the rotor,

an outer groove is formed between every two adjacent outer teeth, an inner groove is formed between every two adjacent inner teeth,

the stator winding coil is wound on the yoke, the two ends of the stator winding coil are respectively positioned in the outer groove and the inner groove, and the outer groove and the inner groove are not filled with the stator winding coil, so that the residual spaces of the outer groove and the inner groove respectively form an axial outer ventilation channel and an axial inner ventilation channel for heat dissipation.

Further, the yoke has a ring-shaped radial cross section.

Furthermore, the radial cross section of each external tooth is T-shaped and has the same area, the cross section area of one end of each T-shaped external tooth connected with the yoke is small, and the cross section area of one end of each T-shaped external tooth adjacent to the shell is large.

Further, the radial cross section of each internal tooth is rectangular and has the same area.

Further, the outer teeth are equal in number to the inner teeth, and the outer grooves are equal in number to the inner grooves.

Further, the radial height of the outer teeth is smaller than the radial height of the inner teeth, and the radial depth of the outer grooves is smaller than the radial depth of the inner grooves.

Further, the stator core is an integral structure formed by laminating electrical steel sheets.

Furthermore, the stator core is a two-pole structure and is a three-phase winding.

Further, the rotor includes a permanent magnet fixed to a rotor core, a sheath for sealing the permanent magnet, and a fastening member for integrally connecting the rotor core and the rotating shaft.

Furthermore, the casing further comprises a left end cover and a right end cover which are respectively arranged at two ends of the high-speed permanent magnet motor, and a left bearing and a right bearing which are used for supporting the rotating shaft are arranged in the left end cover and the right end cover.

Further, the case is made of a non-magnetic material having a good heat conductive property.

The invention has the beneficial effects that:

1. the high-speed permanent magnet motor adopts the back-wound stator winding, and the connection between the winding coil sides of different slots is not through the axial end part of a stator core, but the direct connection between the radial inner slot and the radial outer slot, so that the axial end part length of the stator winding coil of the traditional motor and the total length of a high-speed motor rotor are greatly shortened, which is very important for increasing the rigidity of the high-speed motor rotor. Because of the limitation of material strength, the conventional high-speed motor generally adopts a thin and long rotor, and meanwhile, in order to reduce high-frequency eddy current and hysteresis loss in a stator core, a 2-pole structure is generally selected for the high-speed motor. The connection mode of the stator winding of the traditional high-speed motor leads the winding end part to be very long, so the thin and long rotor is also lengthened, the rigidity of the rotor and the critical rotating speed are reduced, and the stable operation of the high-speed motor is very unfavorable. The stator of the high-speed permanent magnet motor adopts the back winding type winding, and the problem can be effectively solved.

2. The high-speed motor has small volume and high power density because the electromagnetic power of the motor is in direct proportion to the counter potential of the winding and further in direct proportion to the rotating speed of the motor, and when the power and the voltage of the motor are not changed, the number of turns required by the winding after the rotating speed is increased is reduced in inverse proportion to the rotating speed, so that the volume of the high-speed motor is reduced and the high power density is obtained by reducing the number of turns of the winding. The leakage inductance of the motor winding is proportional to the square of the number of winding turns, and a reduction in the number of winding turns results in a high speed motor with very little winding leakage inductance. The high-speed motor is generally powered by a frequency converter, a series of higher harmonics exist in the output voltage of the frequency converter, and the leakage inductance of a winding is small, so that the higher harmonics cannot be filtered, and a larger harmonic component exists in the winding current of the high-speed motor, high-frequency loss is generated in a stator core and a winding of the motor, and eddy current loss is generated in a permanent magnet rotor by a higher harmonic magnetic field, so that the high-frequency loss becomes a main source of rotor loss and heating. For this reason, a filter needs to be externally connected between the inverter and the high-speed motor. The stator core of the high-speed permanent magnet motor adopts a stator core with an inner groove and an outer groove respectively arranged on the radial inner side and the radial outer side, and windings inside and outside the inner coilEdgeAre respectively arranged in the inner slot and the outer slot, and the edge of the winding coil does not exceed the openings of the inner slot and the outer slot, namely has a certain distance with the openings of the inner slot and the outer slot, and provides a magnetic field generated by the winding currentA certain leakage flux path, thereby increasing the leakage inductance of the winding. The winding structure of the invention effectively increases the leakage inductance of the winding, replaces an external filter reactor, and plays a role in inhibiting the high-frequency harmonic current of the stator winding, thereby reducing the loss and the heat generation of the high-speed permanent magnet rotor.

3. The stator core of the invention does not fill the inner slot and the outer slot through the stator winding coil, and the edge of the winding coil has a certain distance from the openings of the inner slot and the outer slot, so that the parts of the inner slot and the outer slot which are not wound with the winding coil form an axial ventilation channel, and the stator and the rotor of the high-speed motor solve the problem of heat dissipation. In a traditional high-speed motor, due to the high-speed rotation of a rotor, ventilation and heat dissipation measures cannot be taken on the rotor of the high-speed motor, heat generated by the rotor needs to cross an air gap and is dissipated out through a stator core, and therefore the permanent magnet rotor is overheated due to the fact that a heat transfer path is too long and the heat transfer effect is poor. The high-speed permanent magnet motor is mainly used for heat dissipation of the permanent magnet rotor and simultaneously takes away a small part of heat of the stator winding and the stator core by arranging the axial inner ventilation channel near the opening of the inner groove of the stator core close to the air gap. And meanwhile, an axial external ventilation channel is arranged near the opening of the outer slot of the shell and used for radiating the stator winding and the stator core.

4. The heat dissipation of the stator winding of the traditional high-speed motor mainly utilizes a conductor arranged in a slot to firstly transfer the heat generated by the winding to a stator core in a heat conduction mode, and then the heat is transferred to the outside of the motor from the stator core in an air cooling or water cooling mode. According to the traditional motor winding structure, the winding end parts are located at the two axial ends of the stator core, the winding end parts are long and are suspended in the air to be in non-contact with the stator core, the heat generated by the winding end parts needs to be dissipated outwards through the conductors located in the slots and then the iron core, the heat dissipation of the winding end parts is difficult, and the temperature rise is high. The high-speed permanent magnet motor adopts the back-wound winding, and the winding end parts which are positioned at the two axial ends of the iron core and suspended in the air are changed to be placed in the radial slots of the iron core, so that the contact conduction heat dissipation area between the winding and the iron core is increased, the inner and outer coil sides of the stator winding can directly carry out convection heat dissipation through the inner and outer ventilation channels, and the heat dissipation capability of the stator winding and the iron core can be effectively improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the embodiments and the drawings in the prior art, and it is obvious that the drawings described below are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive work.

Figure 1 schematically illustrates one embodiment of a radial cross-sectional view of a high-speed permanent magnet machine of the present invention.

Fig. 2a is a radial cross-sectional view of a stator core of the high-speed permanent magnet machine shown in fig. 1.

Fig. 2b schematically shows the winding of the back-wound winding of the stator of the high-speed permanent magnet motor according to the invention.

Fig. 3a schematically shows a conventional motor stator winding.

Figure 3b schematically shows the back-wound winding of the stator of the high-speed permanent magnet machine of the present invention.

Detailed Description

In the description of the present invention, the term "back-wound winding" means that the stator core of the high-speed permanent magnet motor of the present invention employs a stator core having inner and outer slots respectively disposed at the radial inner and outer sides thereof, and the winding coils are wound in such a manner that both sides of each coil are respectively disposed in the inner and outer slots of the stator core back to back.

In the description of the present invention, "axial direction" refers to a direction in which a rotor rotation shaft of a motor is located, and "radial direction" refers to a direction perpendicular to the axial direction, or a direction in which diameters or radii of a designated sub-core and a designated rotor core are located.

In the description of the present invention, the number of the "plurality of outer teeth" and the "plurality of outer teeth" may be set by those skilled in the art according to the actual needs of the motor. The number of the external teeth and the internal teeth is related to the number of poles and phases of the motor stator winding, the power of the motor and the inner diameter of the stator core, and the relationship is as follows: the more the number of poles and phases, the more the number of external teeth and internal teeth; the larger the motor power and the inner diameter of the stator core, the larger the number of external teeth and internal teeth. For a common medium-small power three-phase two-pole high-speed permanent magnet motor, the number of the external teeth and the number of the internal teeth can be 12, 18, 24, 30, 36 and the like. In one embodiment of the present invention, the number of the outer teeth and the outer teeth is 12 each.

In the high-speed permanent magnet motor of the present invention, it is preferable that each of the internal teeth is of a uniform cross section and the yoke is of a ring shape of a uniform cross section, so that the magnetic field distribution in the stator core is equalized to reduce iron loss.

In the high-speed permanent magnet motor of the present invention, it is preferable that the magnetic flux densities of the inner teeth of the stator and the yoke part are close to each other.

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained below with the accompanying drawings.

Fig. 1 shows a radial cross-section of a high-speed permanent magnet machine 1 according to the invention, from which it can be seen that the high-speed permanent magnet machine 1 has a machine housing 10, a stator core 20 and a rotor 30. Wherein the housing 10 is located outside the stator core 20 and surrounds the stator core 20, i.e. the housing 10 is located immediately outside (outer circumferential surface) the stator core 20, and the stator core 20 is arranged around the rotor 30, i.e. the rotor 30 is located inside the stator core 20, adjacent to the inside (inner circumferential surface) of the stator core 20.

The stator core 20 is composed of a plurality of external teeth 21, a plurality of internal teeth 22, and a yoke 23. In the example shown in fig. 1, the number of the external teeth 21 and the internal teeth 22 is 12, respectively, and they are arranged on both sides of the yoke 23 in alignment. One end of the external teeth 21 and one end of the internal teeth 22 are located on the yoke 23, respectively, and the other end of the external teeth 21 and the other end of the internal teeth 22 are adjacent to the housing 10 and the rotor 30, respectively. An outer groove 24 is formed between every two adjacent outer teeth 21, an inner groove 25 is formed between every two adjacent inner teeth 22, and openings of the outer groove 24 and the inner groove 25 are respectively located on an outer circumferential surface and an inner circumferential surface of the stator core 20 and are distributed on both sides of the yoke 23 in a one-to-one correspondence. Each outer tooth 21 has a T-shaped radial cross section and the same area. The wider end of the T-shaped external teeth 21 is a portion of the outer circumferential surface of the stator core 20, and the narrower end thereof is connected with the yoke 23. Each of the inner teeth 22 has a rectangular radial cross section and the same area. One end of the rectangular internal teeth 22 is a part of the inner circumferential surface of the stator core 20, and the other end is connected with the yoke 23. The outer groove 24 between each two of the T-shaped external teeth 21 has a can shape with a small opening and a large middle and bottom, and the opening of the can-shaped outer groove 24 is located on the outer circumferential surface of the stator core 20. The inner groove 25 between the two rectangular inner teeth 22 has a shape of a conical flask with a small opening and a large bottom, and the opening of the conical inner groove 25 is located on the inner circumferential surface of the stator core 20. The yoke 23 has a ring-shaped radial cross section.

The stator winding coil 26 is wound on the yoke 23 with both ends thereof positioned in the outer and

inner slots

24 and 25, respectively, and the winding coil 26 does not fill the outer and inner slots 24 and 25 (the positions where about 1/5 remain in the outer and

inner slots

24 and 25, respectively, are empty). The outer edge 261 of the stator winding coil 26 is distanced from the opening of the outer slot 24 on the outer circumferential surface, so that the part of the outer slot 24 between the outer edge 261 of the stator winding coil and its opening is empty, forming an axial ventilation channel 27. The inner edge 262 of the stator winding coil 26 is spaced from the opening of the inner circumferential surface of the inner slot 25 such that the portion of the inner slot 25 between the inner edge 262 of the stator winding coil and the opening thereof is hollow to form the axial inner air path 28. Thus, the outer edge 261 and the inner edge 262 of the stator winding coil are directly convected to dissipate heat through the axially outer air path 27 and the axially inner air path 28, respectively, and the heat dissipating capacity of the stator winding and the core can be effectively improved. And, the outer edge 261 and the inner edge 262 of the stator winding coil are respectively positioned in the outer slot 24 and the inner slot 25 of the stator core, so that the leakage inductance of the winding coil is increased, the high-frequency harmonic current of the stator winding is restrained, and the additional loss and the heat generation generated by the high-frequency harmonic current of the high-speed permanent magnet motor are reduced.

Fig. 2a shows the arrangement of the stator winding coils 26 of the high-speed permanent magnet machine 1 of fig. 1 in the outer slots 24 and the inner slots 25 of the stator core 20. For convenience of illustration, the three-phase winding coils 26 in the 12 outer slots 24 and the 12 inner slots 25 are labeled a1, a2, -a1, -a2 and B1, B2, -B1, -B2, and C1, C2, -C1, -C2, respectively, in this figure.

Fig. 2b shows the winding pattern of the stator winding coil of the two-pole three-phase winding permanent magnet motor with the stator core shown in fig. 2a having 12 inner slots and 12 outer slots. The figure takes an A-phase winding as an example and schematically illustrates the winding and connection modes of the A-phase winding coil in the A1, A2, -A1 and-A2 inner and outer slots shown in figure 2 a. It can be seen that the winding directions of the coils in the a1 and a2 slots are consistent, the winding directions of the coils in the-a 1 and-a 2 slots are also consistent, but the winding directions of the coils in the a1 and a2 slots are opposite to the winding directions of the coils in the-a 1 and-a 2 slots, so that the total back electromotive force of the phase a winding (between the terminals a and-a in fig. 2 b) is superposed but not cancelled after the four coils a1, a2, -a1 and-a 2 are connected in series.

Fig. 3a shows a schematic view of the structure of the stator winding of a conventional electric machine. Where 10 'denotes a casing, 20' denotes a stator core, 26 'denotes a stator winding, and 40' denotes a rotating shaft, it can be seen from this figure that the coils in the stator slots in a conventional motor are axially closed at the ends of the stator core. The heat dissipation of the stator winding of the traditional high-speed motor mainly utilizes a conductor arranged in a slot to firstly transfer the heat generated by the winding to a stator core in a heat conduction mode, and then the heat is transferred to the outside of the motor from the stator core in an air cooling or water cooling mode. The winding end parts in the traditional motor winding structure are positioned at two axial ends of a stator core, the winding end parts are long and are suspended in air to be in non-contact with the stator core, the heat of the winding end parts needs to be dissipated outwards through conductors positioned in a slot and then the iron core, the heat dissipation of the winding end parts is difficult, and the temperature rise is high.

Fig. 3b shows a schematic diagram of the structure of the back-wound stator winding of the high-speed permanent magnet machine 1 according to the invention, where 10 denotes the casing, 20 denotes the stator core, 26 denotes the stator winding and 40 denotes the shaft, from which it can be seen that the winding coils in the stator slots are closed at the yoke of the stator core. As can be seen from the comparison between fig. 3a and fig. 3b, the back-wound winding of the present invention changes the winding ends of the conventional motor, which are located at the two axial ends of the stator core and suspended in the air, into the radial slots of the core, and the axial end length of the winding is greatly shortened compared with the axial end length of the winding coil of the conventional motor, so that the total length of the rotor can be reduced and the rigidity of the rotor of the motor can be improved. In addition, the contact conduction heat dissipation area between the winding and the stator core is increased, the inner coil side and the outer coil side of the stator winding can directly conduct convection heat dissipation through the inner ventilation channel and the outer ventilation channel, and the heat dissipation capacity of the stator winding and the core is effectively improved.

The stator core can be formed by laminating ultrathin high-frequency low-loss electric steel sheets.

The high-speed permanent magnet motor of the present invention further includes a rotating shaft 40, as shown in fig. 1, the rotor 30 includes a permanent magnet fixed on a rotor core, a sheath for sealing the permanent magnet, and a fastener for connecting the rotor core and the rotating shaft as a whole.

The high-speed permanent magnet motor also comprises a casing, the casing is arranged at the main part of the casing at the periphery of the stator core, and the casing also comprises a left end cover and a right end cover which are respectively arranged at two ends of the high-speed permanent magnet motor, and a left bearing and a right bearing which are used for supporting the rotating shaft are arranged in the left end cover and the right end cover. The casing is made of non-magnetic conductive material (such as aluminum alloy) with good heat conductivity, which not only can improve the heat dissipation capability of the casing, but also more importantly, the magnetic isolation function of the casing is utilized to ensure that the magnetic flux generated by the rotor with the permanent magnet does not enter the external teeth 21 of the stator core, and the external teeth 21 of the stator core only bear the external slots 24 and the windings for supporting the stator core and can not cause the leakage of the rotor magnetic flux.

In operation, magnetic flux generated by one pole of the rotor having permanent magnets crosses the air gap and enters the stator core 20 through the internal teeth 22 of the corresponding stator core below the pole, and then returns to the rotor through the yoke 23 of the stator core and through the internal teeth 22 of the corresponding stator core below the other pole.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A high-speed permanent magnet motor comprising a housing, a stator core and a rotor, the housing being arranged around the outside of the stator core, the stator core being arranged around the rotor, characterized in that the stator core is composed of a plurality of external teeth, a yoke and a plurality of internal teeth,

wherein each outer tooth and each inner tooth are aligned on both sides of the yoke with one end thereof located on the yoke, the other end of the outer tooth being adjacent to the housing, the other end of the inner tooth being adjacent to the rotor,

the stator winding coil is wound on the yoke, both ends of the stator winding coil are respectively positioned in the outer slot and the inner slot, and the stator winding coil does not fill the outer slot and the inner slot, so that the residual spaces of the outer slot and the inner slot respectively form an axial outer ventilation channel and an axial inner ventilation channel for heat dissipation.

2. A high speed permanent magnet machine according to claim 1, wherein the radial cross section of the yoke is annular.

3. The high-speed permanent magnet motor of claim 1, wherein each outer tooth has a T-shaped radial cross section and the same area, and the cross sectional area of the end of each T-shaped outer tooth connected to the yoke is small and the cross sectional area of the end adjacent to the casing is large.

4. A high speed permanent magnet machine according to claim 1, wherein each inner tooth is rectangular in radial cross section and of the same area.

5. The high-speed permanent magnet machine of claim 1, wherein the outer teeth are equal in number to the inner teeth, and the outer slots are equal in number to the inner slots.

6. A high speed permanent magnet machine according to claim 1, wherein said stator core is a unitary structure of laminated electrical steel sheets.

7. The high-speed permanent magnet machine of claim 1 wherein the rotor comprises permanent magnets fixed to a rotor core, a sheath for sealing the permanent magnets, and fasteners integrally connecting the rotor core to the shaft.

8. The high-speed permanent magnet motor according to claim 1 or 2, wherein the casing further comprises a left end cover and a right end cover respectively disposed at two ends of the high-speed permanent magnet motor, and a left bearing and a right bearing for supporting the rotating shaft are disposed in the left end cover and the right end cover.

9. The high speed permanent magnet machine of claim 1, wherein the machine housing is made of a non-magnetic material having good thermal conductivity.