HK1135239B - Electric motor - Google Patents

Description

Electric machine

Technical Field

The invention relates to an electric machine as defined in claim 1 and a method for manufacturing an electric machine as defined in claim 8.

Background

Electric motors are used to convert electrical energy into mechanical energy. In motors of conventional construction, certain basic components can be distinguished, such as a rotor fitted to rotate, a rotor spindle, a stationary stator, bearings and end shields. The rotor is supported by bearings. Typically, a small air gap is left between the rotor and the stator.

The rotary operation of polyphase alternating current motors, such as polyphase synchronous and asynchronous motors, is based on a magnetic field rotating within the machine. The multi-phase stator windings are formed in such a way that when sinusoidal voltages are fed into the phase windings-the voltages fed into the phases have a phase shift of 360/n degrees between them, where n is the number of phases-the current flowing in the stator windings generates a circulating magnetic field in the air gap of the machine, which interaction with the magnetic field of the rotor windings causes the rotor to rotate. In synchronous machines, the magnetic field of the rotor windings is typically generated by permanent magnets or by direct current fed into the rotor field windings. In asynchronous machines, the excitation of the rotor windings is generally achieved via voltages and currents induced in the rotor windings by the magnetic flux generated by the stator currents.

The flux density distribution in the air gap should be as sinusoidal as possible. The rotational movement of the rotor is generated by the action of the sinusoidal fundamental of the flux density, but in practice the magnetic field acting in the machine also contains harmonics, i.e. harmonic components of the fundamental.

The harmonics of the magnetic flux density create an additional force component between the stator and the rotor. In addition, the magnitude of the torque fluctuates (torque ripple) and additional losses occur in the motor.

Harmonic components are generated in the air gap flux density due to both the winding discontinuities on the stator and rotor circumferences and the variation of the permeance in the air gap. The stator windings are typically densely packed in slots and coil sets such that the magnetomotive force generated by the windings in the air gap is not distributed sinusoidally. Variations in the permeance in the air gap are caused, for example, by possible stator and rotor slotting, open poles (open poles) and magnetic saturation. The harmonics of the motor field can be divided into harmonics generated by the rotor and harmonics generated by the stator.

The windings of an electrical machine are conventionally distributed windings in which the coils of different phases are arranged in an interleaved manner such that the area defined by each coil also contains the coil sides of the other phases. Specification US6581270 describes a stator manufacturing method in which the coil sides are distributed in slots in the pole area of the machine. Since the coil sides of the same phase are located at a large distance from each other in the pole area, the end windings are long. A large proportion of the conductor material used in the windings of the machine is not utilized, since the end windings do not generate torque but rather cause losses and require space. Furthermore, since the end windings of different phases cross each other in such a structure, the risk of short-circuiting between the coils increases. The end windings thus require additional insulation. The diffraction work for preparing such windings also involves several operations and often has to be done manually.

Motors provided with conventional distributed windings are also bulky and heavy due to the long end windings and the fact that the coils of the windings are typically distributed in many slots within the pole pair region. This is disadvantageous, especially in the case of motors for elevators, as elevators are increasingly constructed with machine solutions in which the machine is placed between the guide rails and the elevator shaft wall. Therefore, the large size and weight of the motor is a disadvantage.

In recent years, much research has been conducted to develop dense fractional slot windings as they provide solutions to some of the problems associated with conventional windings. In a dense winding, the coil sides of the same coil are placed in adjacent slots. Thus, the end windings are shorter and do not take up as much space as in conventional windings.

One problem with dense windings is that, since the number of slots reserved for the windings per pole of the machine is less than in conventional machines, the magnetomotive force generated by the windings in the air gap deviates significantly from a continuous sinusoidal pattern and thus contains more harmonics than in conventional windings. These harmonics generate both torque ripple and eddy currents in the motor.

Specification US6894413 discloses a generator in which the rotor is magnetized by permanent magnets and the stator has a dense fractional slot winding. In this specification, the rotor diameter is determined by the following equation:

D≥0.00045×P_out

wherein D represents the rotor diameter and P_outRepresenting the power produced by the generator. Thus, for example, the rotor of a 5KW generator has a diameter of at least 2.25 m. This is therefore a rather large multi-pole and slow-turning generator, which can be used as e.g. a wind generator. In this description, the harmonic components of the generator output voltage are also determined for some different geometrical combinations. This specification discloses that these combinations can be used to reduce these harmonics, since according to this specification they cause eddy currents and thus power losses in the generator. This specification also discloses the concept of: rotors can be assembled from thin laminated steel plates to reduce eddy currents, and such concepts are also disclosed: the rotor may be made of a single piece of iron but the iron block is divided into several sections to minimize eddy current losses.

In an effort to eliminate torque ripple caused by dense windings, small notches, for example, are employed. Such a solution is disclosed at least in the specification US 6882080. According to this specification, small notches reduce torque ripple, but this solution has the disadvantage that it is difficult to make windings on the finished motor frame. Specification JP3451263 proposes a solution in which the phase conductors are wound around the poles before the motor is assembled. This involves a new working phase in the motor assembly, delaying the production of the motor and increasing the manufacturing costs.

Disclosure of Invention

The object of the invention is to achieve an electrical machine in which the torque ripple caused by a dense fractional slot winding with respect to the fundamental torque wave is reduced. It is a further object of the invention to disclose an electric machine of construction which improves manufacturability compared to the prior art. A further object of the invention is to disclose an advantageous method of manufacturing the electrical machine.

The motor of the invention is characterized by what is disclosed in the characterization part of claim 1. The method of the invention is characterized by what is disclosed in the characterization part of claim 8. Other embodiments of the invention are characterized by what is disclosed in the other claims.

Embodiments of the invention are also presented in the description part and drawings of the present application. The inventive content disclosed in the application can also be defined in other ways than is done in the claims below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or in respect of advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts. Within the framework of the basic inventive concept, features of different embodiments of the invention can be applied in conjunction with other embodiments.

The present invention relates to an electrical machine having a dense fractional-slot winding and to a method for making a dense fractional-slot winding. The motor of the invention may be used to drive a people mover such as an elevator, a tractor, an escalator, a conveyor belt or conveyor rollers in a factory or warehouse, or some other conveying device for conveying people or goods. The motor of the present invention can also be used as a driving motor of a vehicle such as an electric car or a train.

The drive motor for a conveyor according to the invention comprises at least a stator, a rotor and an air gap therebetween. In the motor of the present invention, the stator and/or the rotor includes slots constituted by slot bottoms and slot openings, and teeth between the slots, and the stator and/or the rotor has a dense winding fitted therein. The dense winding is a fractional slot winding with a maximum slot number of 0.5, which characterizes the corresponding slot per pole and phase. The slot width of the motor slot on the side facing the air gap is at least 75% of the slot bottom width and at most 125% of the slot bottom width. In connection with the present invention, the slot bottom width refers to the maximum slot width that can be filled by the winding and the slot insulation. When the width of the slot increases to at least 75% of the slot bottom width in the case of dense windings, it can be established mathematically and experimentally that the torque ripple of the machine with respect to the torque fundamental wave is reduced to a considerably lower level than in the case of a half-open slot narrower than this. Motor torque and torque ripple are produced by the combined action of all pole pairs of the motor. With the motor parameters proposed in the present invention, the torque ripple of the motor is reduced, while the fundamental wave of the torque remains almost unchanged. The frequency of the torque fundamental wave refers to the electrical frequency of the machine, i.e., the rotational frequency of the magnetic flux in the stator and rotor. The electrical frequency is obtained by multiplying the mechanical rotational frequency of the motor by the number of pole pairs of the motor.

In the electric machine according to the invention the fractional-slot winding is a dense two-layer winding, fitted in a slot with open slot openings to allow the winding to be fitted in the slot relatively easily.

In a preferred embodiment of the invention, the slot bottom width is constant with respect to the slot length, and the winding thus effectively fills the slot.

In a preferred embodiment of the invention, the motor winding comprises n phase windings, at least one of which comprises only one continuous conductor fitted as a coil set to facilitate mechanical winding with the coil set.

In the electric machine according to the invention the rotor and/or stator winding is a fractional slot winding, the number of slots being 2/5.

In an embodiment of the invention, the aforementioned electric machine is a permanent magnet synchronous machine.

In the electric machine according to the invention, the rotor is permanently magnetized, the rotor magnets are placed on the surface of the rotor and the shields of the magnets are preferably made of glass fiber laminate (glass fiber laminate) to reduce eddy current losses. However, the shield of the magnet may also be made of other materials with low magnetic field permeability, such as stainless steel or plastic.

The aforementioned motor according to the invention can also be an elevator motor. In this case the motor of the invention can be installed as part of an elevator system and can be used to move an elevator car in an elevator shaft. The traction sheave of the elevator can also be fitted in conjunction with the rotor of the elevator motor. The traction sheave can be fixed to the rotor, for example by means of special fasteners, or it can be implemented as a fixed part of the rotor.

In an elevator system the motor according to the invention is fitted in the elevator shaft between the elevator car and the guide rails, but the motor can also be placed elsewhere in the elevator shaft or in the machine room. Furthermore, the motor of the invention can be used both in elevator systems without counterweight and in elevator systems provided with a counterweight.

The motor of the invention can be either an axial magnetic line machine or a radial magnetic line machine. In axial flux machines, the flux passes through the air gap of the machine in a direction substantially parallel to the axis of rotation of the machine, whereas in radial flux machines, the flux passes through the air gap substantially in the radial direction of the machine.

In a preferred embodiment of the invention, the stator and/or the rotor comprise a winding form to facilitate the production of the motor windings.

The inventive concept also includes a method for manufacturing a drive motor for a conveyor apparatus.

In the method according to the invention for manufacturing a drive motor for a conveyor, the motor comprising a stator, a rotor and an air gap therebetween, in which motor the stator and/or the rotor comprises slots consisting of a slot bottom and a slot opening, and teeth between the slots. In the method according to the invention, the slot is embodied such that its width on the side facing the air gap is at least 75% and at most 125% of the width of the slot bottom. Further, a dense fractional-slot winding fits within the slots, the winding having a maximum slot count of 0.5.

The method according to the invention involves making an n-phase dense fractional slot winding. The winding comprises m basic winding portions, and each phase winding comprises an equal number m of coil pairs. In this method, a first phase winding of the electrical machine is wound with a continuous conductor to form a coil assembly, preferably by using a coil winding machine, by: first and second coils of a phase winding are wound to form a first coil pair around two adjacent teeth, third and fourth coil windings are wound to form a second coil pair around two adjacent teeth, and a distance between the first and second coil pairs in the winding is adapted to be equal to a conductor length determined by a length b of a basic winding portion, which forms a front end conductor. The coil winding machine may be a rotary shaft assembly to which the conductor is attached and then wound to form the final coil. In accordance with the method of the present invention, a coil winding machine may be used to simultaneously wind all of the coils of a phase winding of an electrical machine with a continuous conductor to form a coil assembly. Since the coil assembly is made of a continuous conductor and the coils in the same coil assembly are thus electrically connected together, it is not necessary to separately connect the coils to each other, which is both labor and time efficient.

According to a preferred embodiment of the invention, the first phase winding of the electrical machine is further wound to form a coil assembly, such that the pairs of coils 1, 2, 1, m-1, m of the first phase winding are fitted in the coil assembly in sequence in an order determined by the sequence numbers of the pairs of coils, in such a way that the distance between each two successive pairs of coils in the winding is adapted to be equal to a conductor length determined by the length of the basic winding portion, said conductor length forming the front end conductor.

In a preferred embodiment of the invention, the phase windings of all n phases of the machine are wound in the same way as the phase winding of the first phase of the machine to form the coil groups.

In the method according to the invention, the two coils of the first coil pair of the first phase winding of the electrical machine are fitted as a coil pair in the first basic winding part in adjacent slots around the first and second teeth in such a way that the adjacent coil sides of the coils are placed in the same slot, the phase current flowing through the first coil around the first tooth and the phase current flowing through the second coil around the second tooth flow in opposite directions, and a slot insulator is fitted in conjunction with the coil sides of the first and second coils fitted in the same slot in such a way that the slot insulator is held between the slot bottom, the side walls and the coil sides. The slot insulator may also consist of two separate slot insulators fitted in combination with two coil sides in the same slot, respectively, such that the slot insulator is held between the slot bottom, side walls and coil sides, and two slot insulators are held between the coil sides to improve the insulation between the coil sides.

In the method according to the invention, the two coils of the first coil pair of the second phase winding of the electrical machine are fitted in mutually adjacent slots in the first basic winding part in the same way as the two coils of the first coil pair of the first phase winding, so that the phase currents in the first coil pair of the first phase winding and the first coil pair of the second phase winding flow in opposite directions, the first coil pair of the first phase winding and the first coil pair of the second phase winding are fitted side by side, so that the coil sides that are closest to each other are fitted in the same slot, and the slot insulation is fitted in combination with the coil sides placed in the same slot, so that the slot insulation is held between the slot bottom, the side walls and the coil sides.

In the method according to the invention, first coil pairs of motor phases 1, 2, 1, n are fitted side by side in the first basic winding portion in the order of the photographs, so that the coil pairs of the phases with successive order are fitted side by side in the same way as the first coil pairs of the first and second phase windings of the motor.

In the method according to the invention, the second coil pair of the first phase of the electrical machine is fitted into the slot in the second basic winding portion in the same way as the first coil pair of the first phase, so that the edgemost and adjacent coil sides in the first and second basic winding portions are fitted into the same slot, and a length of conductor determined by the length of the basic winding portion is left between the first and second coil pairs of the first phase to form an end winding. The second coil pair of the second phase of the motor is fitted into the slots in the second basic winding portion in the same way as the second coil pair of the first phase.

In a preferred method according to the invention, pairs of coils of the phases 1, 2., n-1, n of the motor are fitted in slots in the second basic winding part in the same way as in the first basic winding part.

In the method according to the invention, pairs of coils are fitted in the basic winding parts 1, 2, m-1, m in the same way as in the first and second basic winding parts, so that pairs of phase wound component coils are placed in each basic winding part in an order determined by the order number of the phases, the basic winding parts with successive order numbers are fitted side by side in the same way as in the first and second basic winding parts, and both coil sides are fitted in each slot.

In the method according to the invention, a slot closure insulator is fitted in the slot covering the coil sides, so that the slot closure insulator is in contact with the slot insulator over the entire length of the slot.

According to the invention, it is also possible to wind the coil pairs in parallel. Furthermore, in connection with or after the winding operation, the coil pairs may also be fitted in a special winding frame, which may be fitted together with the motor slots and teeth.

The solution of the invention provides the advantage that the torque ripple of the motor is significantly reduced when the slot width is at least 75% of the slot bottom width. The torque fundamental remains substantially unchanged. This is advantageous when the conveying appliance is driven by the drive motor according to the invention, since torque fluctuations are a disadvantage in the operation of conveying appliances such as elevators and impair the ride comfort thereof, leading to vibrations and noise. The vibrations appear as vibrations at the characteristic frequency of the elevator mechanism and as limited oscillations, which causes the system to oscillate even if the excitation frequency is not the same as the characteristic frequency of the elevator mechanism. The vibrations also cause wear and reduce the service life of the mechanism of the conveying device.

A notch may be considered substantially open when the width of the notch is at least 75% of the width of the slot bottom. This also facilitates the winding of the machine. The windings can be prepared into the final coil before being fitted in place, since the slots are both substantially open, and the windings can be fitted in place on the final rotor and/or stator. Second, according to the method of manufacture described in the present invention, motor phase windings can be mechanically wound into coils from a single continuous conductor, such as by using a coil winding machine, which facilitates the winding operation and reduces the manufacturing cost of the motor.

Due to the disclosed dense fractional slot winding, the number of pole pairs in the machine is significantly increased compared to conventional distributed windings, wherein conductors of different phases are placed in the slots such that each two adjacent slots contain coil sides of different phases. At the same time, the proportion of end windings in the machine is reduced, which reduces the amount of copper material required for the windings in the machine. This also leads to a significant reduction in the price of the motor. Furthermore, the size of the motor is reduced, which is required in the case of motors used in elevators, especially if the elevator motor is placed in the elevator shaft.

The insulation required for the end windings is also reduced since there are not as many crossovers between the end windings of the machine as in the older distributed winding machines. As the cross-over between the end windings is reduced, the risk of winding breakage is reduced and the reliability of the machine is improved.

The winding according to the invention comprises a non-predetermined number of phases, but in the embodiments described below, a three-phase winding is illustrated by way of example. This winding has the advantage that when the winding is wound in a star-like configuration, the separate neutral conductor does not have to be connected to the neutral point, since it can then be arranged that the neutral conductor does not carry current.

Drawings

Figure 1 shows an axial flux machine according to the present invention, provided with a dense fractional-slot winding;

fig. 2 shows a section of a part of a stator rim according to the invention in a flattened manner;

fig. 3 shows a part of a stator rim according to the invention seen perpendicularly to the air gap direction;

FIG. 4 shows a scale plot of torque ripple of the motor with respect to the slot width;

figure 5 shows an axial flux machine according to the present invention.

Detailed Description

In the examples described below, the invention is elucidated by means of a three-phase machine, in which the stator is provided with a dense fractional-slot winding and the rotor is provided with permanent magnets. In this embodiment of the invention the coils comprised by the phase windings are wound in series, but they may also be wound in parallel.

Fig. 1 shows an axial-flux machine stator (axial-flux machine stator) provided with a dense fractional-slot winding. The stator comprises slots 4 and teeth 5. The coils are wound around the teeth to form a dense winding in such a way that the coil sides 31 of the same coil are placed in mutually adjacent slots. In this way, the end windings 38 are kept short, since they extend only between two adjacent slots. Coils 1 and 2 constitute a first coil pair of the first phase, and coils 6 and 7 constitute a second coil pair of the first phase. The figure shows the distance 3 between the first and second coil pairs. This distance is also the size of the basic winding portion. Also shown in the figure is a front conductor 8 connecting the first coil pair 1, 2 and the second coil pair 6, 7 of the first phase to each other. In fig. 1, the coils comprise only one conductor loop, but they may also have a larger number of conductor loops. In the machine according to this figure, the width 9 of the slot bottom is constant over the entire length of the slot to ensure that the coil fills the slot as efficiently as possible.

Fig. 2 shows a part of a stator rim according to the invention drawn in an unfolded manner. The motor has a substantially open slot with a width 10 of at least 75% of the slot bottom width 9. First and second coils 1 and 2 of a first phase are fitted in the slots around two adjacent teeth to constitute a coil pair 1, 2 such that the direction of flow of phase current around a tooth 11 surrounded by the coil 1 is opposite to the direction of flow of current around a tooth 12 surrounded by the coil 2. In each slot, two coil sides are fitted. Slot insulators 13 fit into the slots such that the slot insulators are held between the sides of the coil and the bottom and side walls of the slot.

Fig. 3 shows a part of a stator rim according to the invention seen perpendicularly to the air gap direction. The coils of the first phase are fitted in series to form a coil group such that successive pairs 1, 2 of coils of the same phase; 6. 7 are arranged at a mutual distance 3 determined by the basic winding parts. Two successive coil pairs are connected to each other by a front conductor 8, the front conductor 8 having a length equal to the size of the basic winding portion 3. The first phase is made up of only one coil set by fitting the coil pairs in series in such a way that the two coil pairs 1, 2 and 6, 7 have already been fitted. In each basic winding portion 3, 15, a coil pair is fitted in an order determined by the sequence numbers of the phase windings, so that the number of coil pairs is equal to the number of basic winding portions. The first phase winding 14 is wound from a single continuous conductor to facilitate mechanical winding. The direction of phase current flowing into the motor phase winding in the first coil of the first coil pair of the first phase is indicated by arrow 20, while the direction of flow of phase current in the second coil of the first coil pair of the first phase is indicated by arrow 21. Similarly, the direction of phase current flowing into the motor phase winding in the first coil of the first coil pair of the second phase is represented by arrow 22, while the direction of phase current flow in the second coil of the first coil pair of the second phase is represented by arrow 23. According to the drawing, the directions of phase currents in the first coil pair of the first and second phases are arranged opposite to each other. It can also be seen from the figure that the direction 20, 21 of the phase current in the second coil pair 6, 7 of the first phase is opposite to the direction of the phase current in the first coil pair of the first phase. In the coil according to fig. 3, two conductor loops are fitted, but the number of conductor loops may also differ from this.

The coil pairs of all three phases of the electric machine illustrated in fig. 3 are arranged next to one another on the stator with a sequential number in such a way that the current directions in the coil pairs of different phases are opposite to one another in the same way as in the coil pairs of the first and second phase.

Fig. 4 shows the fluctuation of the motor torque with respect to the torque fundamental wave as a function of the slot width 17. In FIG. 4, T_rippleRepresenting motor torque ripple, and T1 represents the torque fundamental. Accordingly, |_dRepresents the slot width and l represents the slot bottom width. Curve 33 represents the plot of the torque ripple in the case of a dense fractional-slot winding, while curve 34 represents the plot of the torque ripple in the case of a conventional distributed winding, in which the phase winding is distributed over several slots in the pole region. In the case of conventional windings, the torque ripple increases with increasing slot width. In the case of a dense fractional slot winding, the torque ripple is initially small with closed slots, then increases with increasing slot width until it begins to drop again when the slot width increases beyond a certain value 18. According to the invention, the torque ripple drops significantly from the value at point 18 when the slot width is at least 75% of the slot bottom width 19. Such slots are also substantially open and the motor windings can be mounted in such slots after the stator has been brought into its final shape.

Fig. 5 shows a radial-flux motor in which the stator 24 has a dense fractional-slot winding and the rotor 25 has permanent magnets 27. The number of slots of the machine refers to the number of stator slots 4 per phase and pole. Since the machine according to fig. 5 has 12 stator slots, 3 phases and 10 poles, the number of slots will be 2/5.

Appendix 1 shows the simulation results for the motor according to the invention. These simulations were performed with the width ratio of the stator slot 10 and the slot bottom 9 being 50% and 100%.

Fig. 6 shows the simulation results for an electric machine in which the ratio of the width of the stator slot 10 and the slot bottom 9 is 50%. The upper graph shows the motor torque ripple as a function of time, while the lower graph shows the torque spectrum (torque spectrum). The 6 th and 12 th harmonics of the torque can be read from the plot of the torque spectrum.

Fig. 7 accordingly shows the simulation results for an electric machine, in which the ratio of the widths of the stator slot 10 and of the slot bottom 9 is 100%.

According to fig. 6, when the width ratio of the slot 12 and the slot bottom 9 of the stator of the simulated motor is 50%, the peak-to-peak magnitude of the torque fluctuation is 0.75% of the fundamental torque, and according to fig. 7, when the width ratio of the slot and the slot bottom is increased to 100%, the peak-to-peak torque fluctuation is reduced to 0.36% of the fundamental torque. In fig. 6 and 7, the torque harmonic spectrum is determined using the electrical frequency of the motor as the fundamental frequency of the torque.

The invention can be used e.g. in an electric motor used in an elevator system to drive an elevator car. The motor can be placed either in the elevator shaft or in the machine room. However, the invention is not limited to individual applications, but can be used in a generic electrical machine. Another advantageous application which is worth mentioning in addition is an escalator drive machine.

It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, in which the invention has been described by way of example, but that various variations and different embodiments of the invention are possible within the scope of the inventive concept defined in the appended claims.

Claims (10)

1. A permanent magnet synchronous machine for a conveying apparatus, comprising at least a stator (24), a rotor (25) and an air gap (26) therebetween, in which machine the stator and/or rotor comprises slots (4) consisting of slot bottoms (9) and slot mouths (10) and teeth (5) between the slots, and wherein the stator and/or rotor has dense windings (1, 2, 6, 7) fitted in the slots, the dense windings being fractional slot windings with a maximum number of slots of 0.5, and the width of the slot mouths (10) facing the air gap being at least 75% of the width of the slot bottoms (9) and at most 125% of the width of the slot bottoms (9), characterized in that the machine is an axial flux machine with a permanently magnetized rotor (25) on the surface of which rotor magnets (27) are mounted, and the shield (28) of the magnet is made of a glass fiber laminate to reduce eddy current losses, the slot bottom width being constant relative to the slot length.

2. An electric machine according to claim 1, characterized in that the fractional-slot winding is a two-layer dense winding, and that the winding is fitted in a slot (4) with open notches to allow the winding to fit more easily in the slot.

3. An electric machine as claimed in claim 1 or 2, the windings of which comprise n-phase windings, characterized in that at least one phase winding (14) comprises only one continuous conductor fitted as a coil group to facilitate mechanical winding of the coil group.

4. An electric machine according to any of claims 1-2, characterized in that said windings of said rotor (25) and/or stator (24) are fractional slot windings, the number of slots of which is 2/5.

5. An electric machine according to any of claims 1-2, characterized in that the electric machine is an elevator motor.

6. A method of manufacturing a permanent magnet synchronous motor for a conveying apparatus, said motor comprising a stator (24), a rotor (25) and an air gap (26) therebetween, in the machine, the stator and/or the rotor comprises slots (4) consisting of a slot base (9) and a slot opening (10) and teeth (5) between the slots, in the method, the slot opening (10) facing the air gap is formed such that its width is at least 75% of the width of the slot bottom (9) and at most 125% of the width of the slot bottom (9), and in which method a dense fractional-slot winding with a maximum slot number of 0.5 is fitted in the slots, it is characterized in that the motor is made into an axial magnetic line machine and is provided with a permanent magnetized rotor (25), a rotor magnet (27) is arranged on the surface of the rotor, and the shield (28) of the magnet is made of a fiberglass laminate to reduce eddy current losses.

7. Method according to claim 6, characterized in that the winding produced in said method is an n-phase dense fractional slot winding with m basic winding parts (3), each phase winding comprising an equal number of m coil pairs (1, 2), and in that said method comprises the steps of:

a. winding a first phase winding (14) of the electrical machine with a continuous conductor to make a coil assembly, preferably by using a coil winding machine, in the following manner: -winding a first (1) and a second (2) coil of said phase winding to form a first coil pair around two adjacent teeth (11, 12), -winding a third (6) and a fourth coil (7) to form a second coil pair around two adjacent teeth, and-the distance between the first and second coil pairs in the winding is adapted to be equal to a conductor length determined by the length of said basic winding part (3), said conductor length forming a front end conductor (8).

8. The method of claim 7, further comprising the steps of:

b. winding a first phase winding (14) of the electrical machine as a coil group according to step a by sequentially fitting the coil pairs 1, 2.. m-1, m of a first phase winding of the coil group in an order determined by the sequence numbers of the coil pairs in such a way that the distance between two successive coil pairs (1, 2; 6, 7) of the windings is adapted to be equal to a conductor length determined by the length of the basic winding portion (3), said conductor length forming a front end conductor (8);

c. winding n phase windings of the motor in the same manner as the first phase (14) of the motor to form coil groups according to steps a and b;

d. fitting two coils of a first coil pair (1, 2) of a first phase winding (14) of an electric machine in a first basic winding part (3) in adjacent slots around first and second teeth (11, 12) in such a way that adjacent coil sides (31) of said coils are placed in the same slot, the direction (20) of the phase current flowing through the first coil around the first tooth and the direction (21) of the phase current flowing through the second coil around the second tooth are opposite to each other, and a slot insulator (13) is fitted in conjunction with the coil sides of the first and second coils placed in the same slot in such a way that said slot insulator is held between the slot bottom, side walls and coil sides;

e. according to step d, in the same way as the two coils of the first coil pair of the first phase winding, the two coils (29, 30) of the first coil pair of the second phase winding (35) of the motor are fitted in adjacent slots in the first basic winding part in such a way that the directions of phase currents in the first coil pair (20, 21) of the first phase winding and the first coil pair (22, 23) of the second phase winding are opposite to each other, the first coil pair (1, 2) of the first phase winding and the first coil pair (29, 30) of the second phase winding are fitted in parallel in such a way that the coil sides closest to each other are fitted in the same slot, and a slot insulator (13) engages the coil sides in the same slot in such a way that the slot insulator is held between the slot bottom, the side walls and the coil sides;

f. first coil pairs of the motor phases 1, 2, n-1, n in the first basic winding portion are fitted side by side in the order of the pictures in such a way that the coil pairs of the phases with successive orders are fitted side by side in the same way as the first coil pairs of the first (1, 2) and second (29, 30) phase windings of the motor according to steps d and e.

9. The method of claim 8, further comprising the steps of:

g. according to step d, in the same way as the first coil pair (1, 2) of the first phase, the second coil pair (6, 7) of the first phase of the motor is fitted in the slot in the second basic winding portion (15) in such a way that the most adjacent coil sides of the first and second basic winding portions (3, 15) fit in the same slot and the conductor length determined by the length (3) of the basic winding portion is between the first and second coil pairs of the first phase as the front conductor (8);

h. fitting a second coil pair (36, 37) of a second phase of the motor in slots in a second primary winding portion in the same way as the second coil pair (6, 7) of the first phase according to steps d and e;

i. the coil pairs of the motor phases 1, 2,., n-1, n are fitted in the second basic winding part according to steps d, e and f in the same way as the first basic winding part (3) according to the order of the phases.

10. The method of claim 9, further comprising the steps of:

j. fitting coil pairs in the basic winding parts 1, 2, 1, m-1, m in the same way as in the first and second basic winding parts (3, 15) according to steps d, e, f, g, h, i in such a way that a phase winding coil pair is placed in the basic winding parts in an order determined by the order number of the phase, the basic winding parts with successive order numbers are fitted side by side according to step g and both coil sides are fitted in the slots;

k. a slot closing insulator (32) is fitted in the slot to cover the coil side so that the slot closing insulator is in contact with the slot insulator (13) over the entire slot length.