JP2014131373A - Permanent magnet synchronous machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve torque and efficiency in a permanent magnet synchronous machine to which a ferrite magnet is applied and a drive system using the machine.SOLUTION: A permanent magnet synchronous machine is a permanent magnet type motor comprising: a rotor having ferrite magnets arranged so as to configure a plurality of poles inside; and a stator arranged so as to have a predetermined gap between the stator and the rotator. The permanent magnet synchronous machine is configured so that a gap facing surface of each pole of the rotator has a shape having a salient to the side of the gap, a circumferential width of the salient is θp, and a part of the gap between the stator and the rotator in the θp is smaller than a part of the gap outside the θp; and is configured so that the electrical angle θp has relation of 80°<θp<135°.

Description

  The present invention relates to a permanent magnet synchronous machine and a drive system using the same.

  In the permanent magnet synchronous machine, an interior permanent magnet (hereinafter, IPM) structure in which a permanent magnet is embedded in a rotor is widely adopted. In IPM, reluctance torque can be used in addition to magnet torque, but in order to further increase the torque, the magnetic flux generation section on the rotor gap facing surface is increased, that is, the induced electromotive force waveform due to the magnetic flux is trapezoidal. It is effective to make it wavy.

  Patent Document 1 discloses a permanent magnet embedded rotor in which a housing hole for embedding a permanent magnet is convex radially inward so that the magnetic flux generation section can be increased. According to Patent Document 1, the induced electromotive force waveform is trapezoidal, and the torque can be increased by applying 120 ° energization control in accordance with the magnetic flux generation section.

Japanese Patent No. 4666726

  For permanent magnets embedded in permanent magnet synchronous machines having an IPM structure, ferrite magnets that are inexpensive and can be stably procured have begun to be adopted. However, since the holding force of the ferrite magnet is about 1/3 that of the neodymium magnet, it is necessary to increase the magnet thickness and cover the decrease in holding force. However, as a result, the inter-pole portion of the rotor-facing gap-facing surface becomes a magnetic flux-free section. For this reason, in the method of adjusting the magnet arrangement as in Patent Document 1, the magnetic flux generation section cannot be increased.

  Therefore, an object of the present invention is to enable improvement in torque and efficiency in a permanent magnet synchronous machine to which a ferrite magnet is applied and a drive system using the same.

  In order to achieve the above object, the present invention provides a "rotator having a stator having teeth around which a stator winding is wound and a magnetic body made of a rotor core, and being arranged through the stator and a gap. In a permanent magnet synchronous machine having a rotor, a plurality of magnet insertion holes arranged in the magnetic body, and a ferrite magnet embedded in each of the plurality of magnet insertion holes, the rotor includes the plurality of magnet insertions By forming a convex portion that protrudes toward the stator at a position corresponding to each of the holes, the gap between the convex portion and the teeth is larger than the gap between the outer peripheral portion other than the convex portions and the teeth. It is configured such that the relationship is 80 ° <θp <135 °, where θp is an electrical angle corresponding to the circumferential width of the convex portion ”.

  According to the present invention, it is possible to improve the torque and efficiency of the permanent magnet synchronous machine.

1 is a partial sectional view of one pole of a permanent magnet synchronous machine according to a first embodiment of the present invention; Magnetic flux density distribution diagram of gap by permanent magnet Teeth layout of concentrated winding 2-pole 3-slot series Explanatory drawing of the structure in 1st Example of this invention Explanatory drawing of the structure in 1st Example of this invention Effect diagram in the first embodiment of the present invention Explanatory drawing of the frequency-iron loss characteristic in 3rd Example of this invention Perspective view of 4-pole 6-slot three-phase motor

  An embodiment of the present invention will be described below with reference to the drawings. In the following description, the same symbols are attached to the same components. Their names and functions are the same, and duplicate descriptions are avoided. Further, in the following description, the inner rotor is targeted, but the effect of the present invention is not limited to the inner rotor, and can be applied to an outer rotor having a similar configuration. is there.

  FIG. 8 is a perspective view of a 4-pole 6-slot three-phase motor. A stator 9 is composed of a stator core 10 and a stator winding 12 wound around a tooth 11, and the rotor 1 is formed from the rotor core. The magnetic body is provided, and is disposed through a gap (gap) with the stator 9 and is rotatably held. The rotor 1 is composed of a rotor core 2 having a magnet insertion hole 4 and a permanent magnet 3 arranged so as to constitute four poles (number of pole pairs p = 2). The stator winding 12 is configured by sequentially arranging three-phase windings U, V, and W in the circumferential direction. The U-phase windings 12u1 and 12u2 connected in series are connected to the peak value I (this from the inverter). AC current iu) is supplied. The same applies to the V phase and the W phase, but the current phase of each phase is shifted by 120 ° in electrical angle.

  FIG. 1 shows a partial sectional view of one pole of a permanent magnet synchronous machine according to a first embodiment of the present invention. The present embodiment relates to a permanent magnet synchronous machine having an adder-type rotor 1 composed of permanent magnets arranged to form a plurality of poles. The rotor 1 has a plurality of magnet insertion holes 4 formed in a magnetic body so as to protrude radially inward, and permanent magnets 3 (not shown) are embedded in the respective magnet insertion holes 4. . The magnet insertion hole 4 and the permanent magnet 3 have two bending points in the circumferential direction per pole, and extend from the respective bending points to the direction perpendicular to the magnetization direction and toward the end of the pole. It is composed. In this embodiment, the permanent magnet 3 is a permanent magnet having a relatively low holding force and residual magnetic flux density, such as a ferrite magnet.

  The permanent magnet 3 may be configured to have a plurality of bending points and straight portions at three or more locations, or may be U-shaped. By adopting such a magnet shape, the surface area of the magnet magnetic flux generation surface is increased, and the cross-sectional area of the core of the permanent magnet 3 in the radial direction is increased, so that the reluctance torque can be actively utilized. . Further, the permanent magnet 3 may be integrally formed without being divided in the circumferential direction per pole, or a plurality of permanent magnets 3 may be arranged in the circumferential direction. Further, a plurality of parts may be divided in the axial direction, or may be formed integrally without being divided. The rotor core 2 may be composed of laminated steel plates stacked in the axial direction, may be composed of a dust core, or may be composed of amorphous metal.

  The gap facing surface per pole of the rotor core 2 is shaped to be convex toward the gap side, and this convex portion has a circumferential width corresponding to the electrical angle θp as shown in FIG. That is, the rotor 1 is formed with a convex portion that protrudes toward the stator 9 (that is, the teeth 11 side) at a position corresponding to each of the plurality of magnet insertion holes 4, and the circumferential width of the convex portion is an electrical angle. This corresponds to θp. By this convex portion, the gap between the convex portion and the tooth 11 is configured to be smaller than the gap between the outer peripheral portion other than the convex portion and the tooth 11. The gap 20 in the θp section is configured to be smaller than the gap 21 in the sections other than θp, and the θp is configured to have a relationship of 80 ° <θp <135 ° in electrical angle.

  With the above configuration, the fifth and seventh components of the induced electromotive force due to the magnetic flux can be increased, that is, even when a thick ferrite magnet is applied, a trapezoidal induced electromotive force waveform can be obtained, so that the torque is improved , Efficiency can be improved.

Below, the theoretical formulas of the fifth and seventh order components of the induced electromotive force are derived, and the principle of obtaining such effects will be described.
First, the magnetic flux density distribution Bpm (xr) of the gap by the permanent magnet 3 is as shown in FIG. Here, xr is the circumferential position (electrical angle, deg.) Of the rotor outer periphery. At this time, the spatial ν-order component of Bpm (xr) is expressed by the following equation.

When the rotor is rotating at the angular velocity ω1, the relationship between the stator coordinates xs and the rotor coordinates xr is
Therefore, the magnetic flux density distribution Bpm (xs) of the gap by the permanent magnet 3 viewed from the stator coordinate system is as follows.

In the expression (3), the spatial order ν of the gap magnetic flux density distribution by the permanent magnet 3 and the time order μ are equal, and both are expressed by μ.
Next, in the case of a concentrated winding 2-pole 3-slot series, the time μ-order component Φc, μ of the magnetic flux amount interlinked with the one-phase coil is −θt / 2 to θt / 2 as shown in FIG. It is obtained from the integration interval. Note that θt is an electrical angle corresponding to the teeth 11 as shown in FIG.
Where l: core shaft length

Therefore, the induced electromotive force waveform μ order component uc, μ due to the magnetic flux is expressed by the following equation.
Where Nc: number of coil turns

From the above, the amplitude ratio kμ of the μ-order component with respect to the fundamental wave component is expressed by the following equation.

  In the concentrated winding, since the electrical angle θt of the teeth 11 is 120 ° at the maximum, the relationship between θp and kμ at this time is obtained as shown in FIG. In FIG. 4, in a permanent magnet synchronous machine to which a ferrite magnet is applied, it is necessary to make the magnet thick, so that θp is often smaller than 160 °.

  From the equation (6), the theoretical maximum values of the fifth-order component and the seventh-order component are 0.200 and 0.143, respectively. By adopting a configuration in which the sum exceeds, the induced electromotive force waveform can be approximated to a trapezoidal waveform. For this purpose, it can be seen from FIG. 4 that θp is preferably 80 ° <θp <135 ° in electrical angle. Even when θp other than the above is adopted, it is possible to increase the sum of the fifth and seventh order components. However, for example, when θp = 30 °, the fundamental wave is clear as is clear from Equation (6). It can be said that it is unsuitable because the components are significantly reduced.

  FIG. 4 shows the case of θt = 120 °. However, even when θt = 90 °, the tendency is almost the same as shown in FIG. 5, and 80 ° <θp <135 °. It turns out that it is suitable. However, if θt is reduced, the fundamental wave component is reduced. Therefore, θt should be in the range of 90 ° <θt <120 °, and is preferably closer to 120 °. That is, the electrical angle θt corresponding to the circumferential width of the teeth 11 of the stator 9 is configured such that θp <θt and 90 ° <θt <120 °. In this embodiment, when the electrical angle corresponding to the circumferential width of each of the plurality of magnet insertion holes 4 is θm, the relationship θp <θm is established.

  FIG. 6 shows an induced electromotive force waveform at θp = 123 ° when the present invention is applied and a waveform at θp = 69 ° when not applied. From FIG. 6, it can be seen that a trapezoidal induced electromotive force waveform can be generated by setting θp = 123 °. Thereby, even when a thick ferrite magnet is applied, torque and efficiency can be improved.

  In this embodiment, the concentrated winding 2-pole 3-slot system is targeted, but the value of the sin second term shown in the equation (6) is different even for fractional slots such as the concentrated winding 4-pole 3-slot system. Thus, by setting 80 ° <θp <135 °, a trapezoidal induced electromotive force waveform can be generated in the same manner. In addition, a trapezoidal induced electromotive force waveform can be generated in the same manner by setting 80 ° <θp <135 ° for the distributed winding only by changing the value of the sin second term shown in Equation (6). .

  In this embodiment, a trapezoidal induced electromotive force waveform including fifth and seventh harmonic components can be generated by setting 80 ° <θp <135 °. Due to the influence of the fifth and seventh components, harmonic fifth and seventh components are also generated in the current waveform supplied from the inverter to the permanent magnet synchronous machine. Even in the 180 ° energization control, torque and efficiency can be improved.

  However, the magnitude of the fifth and seventh order components of the current waveform is smaller than the magnitude of the fifth and seventh order components of the induced electromotive force waveform due to the influence of the ratio of d and q axis inductance, so-called salient pole ratio. It may be difficult to generate a current waveform similar to the induced electromotive force waveform. In such a case, the current waveform energized from the inverter is a waveform that approximates the induced electromotive force waveform of the permanent magnet synchronous machine, or the torque is improved by applying a voltage pulse pattern that can generate the approximate waveform, Efficiency can be improved.

  In this embodiment, the induced electromotive force waveform is distorted in a trapezoidal waveform, and the current waveform is also distorted in a trapezoidal waveform. In such a case, although torque improvement and efficiency improvement can be achieved, a harmonic component of magnetic flux is generated by a current harmonic component, and this increases a harmonic component of iron loss.

  FIG. 7 shows the frequency-iron loss characteristics at 1.0 T of the electrical steel sheet 35A300 grade. It can be seen that the iron loss increases rapidly at frequencies higher than 300 Hz as a knick point. Therefore, in this embodiment, the fundamental wave frequency of the current flowing through the stator winding 12 of the permanent magnet synchronous machine is set to 300 Hz or less, so that the iron loss can be used within a small range.

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Rotor core, 3 ... Permanent magnet, 4 ... Magnet insertion hole, 9 ... Stator, 10 ... Stator iron core, 11 ... Teeth, 12 ... Stator winding 12, 20 ... θp section Gap, 21... Gap other than θp.

Claims (5)

A stator having teeth around which a stator winding is wound;
A rotor having a magnetic body composed of a rotor core, and a rotor disposed via a gap with the stator;
A plurality of magnet insertion holes arranged in the magnetic body;
In a permanent magnet synchronous machine having a ferrite magnet embedded in each of the plurality of magnet insertion holes,
The rotor is formed with a convex portion that protrudes toward the stator at a position corresponding to each of the plurality of magnet insertion holes, so that a gap between the convex portion and the teeth is other than the convex portion. It is configured to be smaller than the gap between the outer peripheral portion and the teeth,
A permanent magnet synchronous machine configured to satisfy a relationship of 80 ° <θp <135 °, where θp is an electrical angle corresponding to a circumferential width of the convex portion. In the permanent magnet synchronous machine according to claim 1,
The current waveform that is passed from the inverter to the permanent magnet synchronous machine is a waveform that approximates the induced electromotive force waveform of the permanent magnet synchronous machine, or a voltage pulse pattern that can generate the approximate waveform is applied. Permanent magnet synchronous machine. In the permanent magnet synchronous machine according to claim 1,
A permanent magnet synchronous machine configured to have a relation of θp <θm, where θm is an electrical angle corresponding to a circumferential width of each of the plurality of magnet insertion holes. In the permanent magnet synchronous machine according to any one of claims 1 to 3,
Permanent magnet, wherein the electrical angle corresponding to the circumferential width of the teeth of the stator is θt, and θp <θt and 90 ° <θt <120 °. Synchronous machine. In the permanent magnet synchronous machine according to any one of claims 1 to 3,
A permanent magnet synchronous machine characterized in that a fundamental wave frequency of a current applied to the stator winding of the permanent magnet synchronous machine is 300 Hz or less.