JP2013051763A - Permanent magnet type rotating electrical machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement increased torque in a low speed rotation range and increased output and improved efficiency in a middle/high speed rotation range.SOLUTION: The permanent magnet type rotating electrical machine includes: a stator 12 having a stator core 16 and armature windings 18; and a rotor 14 having a rotor core 24 rotatable relative to the stator, and a plurality of permanent magnets 3, 4a, 4b embedded to form a plurality of magnetic poles 7, and during operation, magnetizes at least one of the permanent magnets constituting the magnetic pole of the rotor via a magnetic field generated by a current flowing through the armature windings to thereby irreversibly change a flux content of the permanent magnet. The plurality of permanent magnets forming the magnetic pole include a variable intensity magnet 3 having an irreversibly variable flux content, and a fixed intensity magnet 4a arranged in series with the variable intensity magnet in terms of a magnetic circuit for forming the magnetic pole and having a fixed flux content, and the fixed intensity magnet 4a has a larger product of a coercive force and a magnetization direction thickness than that of the variable intensity magnet 3 fully within a maximum use temperature range.

Description

  Embodiments described herein relate generally to a permanent magnet type rotating electrical machine in which a permanent magnet for a field is embedded in a rotor.

  In general, there are two types of permanent magnet type rotating electrical machines. They are a surface magnet type permanent magnet type rotating electrical machine in which a permanent magnet is attached to the outer periphery of a rotor core, and an embedded permanent magnet type rotating electrical machine in which a permanent magnet is embedded in a rotor core. An embedded permanent magnet type rotating electrical machine is suitable as the variable speed drive motor.

  In the permanent magnet type rotating electrical machine, the interlinkage magnetic flux of the permanent magnet is always generated with a constant strength, so that the induced voltage (back electromotive voltage) by the permanent magnet increases in proportion to the rotational speed. Therefore, when the variable speed operation is performed from low speed to high speed, the induced voltage by the permanent magnet becomes extremely high at high speed rotation. When an induced voltage by a permanent magnet is applied to an electronic component such as an inverter and exceeds its withstand voltage, the electronic component breaks down. For this reason, it is conceivable to perform a design in which the amount of magnetic flux of the permanent magnet is reduced so as to be equal to or lower than the withstand voltage, but in that case, the output and efficiency in the low speed region of the permanent magnet type rotating electrical machine are reduced.

  When performing variable speed operation close to constant output from low speed to high speed, the interlinkage magnetic flux on the right of the permanent magnet is constant, so the rotating electrical machine voltage reaches the upper limit of the power supply voltage in the high-speed rotation range, and the current required for output flows. Disappear. As a result, the output is greatly reduced in the high-speed rotation region, and further, variable speed operation cannot be performed over a wide range up to high-speed rotation.

  Recently, as a method for expanding the variable speed range, a low coercive force permanent magnet (hereinafter referred to as a variable magnetic force magnet) whose magnetic flux density is irreversibly changed by a magnetic field generated by a stator winding current, and a variable magnetic force. A high coercivity permanent magnet (hereinafter referred to as a fixed magnet), which has a coercivity more than twice that of the magnet, is arranged. A technique has been proposed in which a variable magnetic magnet is magnetized with a magnetic field generated by an electric current so as to reduce the magnetic flux, thereby adjusting the total amount of flux linkage.

  This permanent magnet type rotating electrical machine has an excellent characteristic that the amount of interlinkage magnetic flux of the variable magnetic force magnet can be greatly changed from the maximum to 0 by the d-axis current of the rotor, and the magnetization direction can be changed in both forward and reverse directions. On the other hand, when magnetizing the variable magnetic force magnet, a large magnetizing current is required, and the inverter for driving the electric motor needs to be enlarged.

  In particular, due to the characteristics of the permanent magnet, a large magnetizing current is required in the case of increasing the magnetism than in the case of demagnetization. However, the permanent magnet type rotating electrical machine has a configuration in which two types of magnets are magnetically arranged in parallel. For this reason, a large magnetic field is required for magnetizing the variable magnetic force magnet 3 due to the influence of the interlinkage magnetic flux of the fixed magnetic force magnet 4.

  As a technique for solving such a problem, a magnetic pole of a rotor is formed using two or more kinds of permanent magnets having a product of a coercive force and a magnetization direction thickness different from those of other permanent magnets. Arranged in series on the magnetic circuit, and with respect to the two or more types of permanent magnets arranged in series, among the two or more types of permanent magnets, magnetize a permanent magnet having a large product of coercive force and magnetization direction thickness. A permanent magnet with a small product of coercive force and magnetization direction thickness is magnetized among two or more types of permanent magnets arranged in series by a magnetic field that is arranged in parallel on the circuit and generated by the current of the armature winding. Thus, a technique for irreversibly changing the amount of magnetic flux of a permanent magnet constituting the magnetic pole has been proposed.

JP 2006-280195 A JP 2008-048514 A JP 2010-124608 A JP 2010-130859 A JP 2009-072021 A

  In the above-described conventional permanent magnet type rotating electric machine, the two types of permanent magnets are arranged in series in terms of magnetic circuits, so that the magnetization direction dimension becomes thinner than the permanent magnets arranged in parallel in terms of magnetic circuits. . In addition, NeFeB permanent magnets are usually used for permanent magnets with a large product of coercive force and magnetization direction thickness, but it is known that their magnetic properties deteriorate at higher temperatures. For example, it is designed to prevent irreversible demagnetization at the rated current of the rotating electrical machine.

  However, in a variable magnetic motor that irreversibly changes the amount of magnetic flux of a permanent magnet, the magnet is magnetized by passing a current that exceeds the rated current of a normal rotating electrical machine, and the magnet and magnetic circuit change the amount of magnetic flux irreversibly. The permanent magnets that are arranged in series with each other and that do not cause an irreversible change are subjected to a large magnetic field as with the permanent magnets that change irreversibly. Furthermore, since the thickness in the magnetization direction is set to be thin, NdFeB permanent magnets whose magnetic properties deteriorate at high temperatures cause irreversible demagnetization during magnetization at high temperatures, reducing the total amount of magnetic flux generated from the rotor. As a result, the output of the rotating electrical machine is reduced.

  The present invention has been made in view of the above points, and its problem is that it enables variable speed operation in a wide range from low speed to high speed, and high torque in the low speed rotation range and high output in the middle / high speed rotation range, An object of the present invention is to provide a permanent magnet type rotating electrical machine capable of improving efficiency.

According to the embodiment, a permanent magnet type rotating electrical machine includes a stator core, a stator having an armature winding attached to the stator core, and a rotor core provided rotatably with respect to the stator. And a rotor having a plurality of permanent magnets embedded in the rotor core to form a plurality of magnetic poles, and during operation, the magnetic poles of the rotor are made by a magnetic field generated by a current flowing through the armature winding. A permanent magnet type rotating electrical machine that magnetizes at least one of the constituting permanent magnets and irreversibly changes the amount of magnetic flux of the permanent magnet,
The plurality of permanent magnets forming the magnetic pole are arranged in series with the variable magnetic force magnet that can irreversibly change the amount of magnetic flux and the magnetic circuit for forming the magnetic pole, and the amount of magnetic flux is fixed. The product of the coercive force and the magnetization direction thickness is greater than the product of the coercivity and the magnetization direction thickness of the variable magnetic magnet over the entire range within the maximum operating temperature range. It is characterized by being large.

FIG. 1 is a cross-sectional view showing a permanent magnet type rotating electric machine according to a first embodiment. FIG. 2 is an enlarged sectional view showing a part of a rotor and a stator of the permanent magnet type rotating electric machine. FIG. 3 is a diagram showing the action of the variable magnetic magnet and the fixed magnetic magnet 4a during magnet magnetization in the rotating electrical machine. FIG. 4 is a conceptual diagram of a demagnetization curve of a permanent magnet. FIG. 5 is a diagram showing a change in operating point of a low coercive force magnet and magnetic characteristics of a typical magnet. FIG. 6 is a cross-sectional view of the rotating electrical machine showing the operation of the short-circuit coil. FIG. 7 is an enlarged cross-sectional view illustrating a part of a rotor and a stator of a permanent magnet type rotating electric machine according to a second embodiment. FIG. 8 is an enlarged cross-sectional view showing a part of a rotor and a stator of a permanent magnet type rotating electric machine according to a third embodiment.

  Various embodiments will be described below with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. In addition, each drawing is a schematic diagram for promoting the embodiment and its understanding, and its shape, dimensions, ratio, etc. are different from the actual device, but these are considered in consideration of the following description and known techniques. The design can be changed as appropriate.

(First embodiment)
FIG. 1 shows an embedded permanent magnet type rotating electrical machine 10 according to the first embodiment, and FIG. 2 is an enlarged sectional view showing a magnetic pole portion.
As shown in FIGS. 1 and 2, the rotating electrical machine 10 is configured as an inner rotor type rotating electrical machine, for example, and has an annular, here cylindrical, stator 12 supported by a fixed frame (not shown) and a fixed A rotor 14 that is rotatably supported on the inner side and coaxially with the stator is provided.

  The stator 12 includes a cylindrical stator core 16 and an armature winding 18 embedded in the stator core. The stator core 16 is configured by laminating a large number of magnetic materials, for example, annular electromagnetic steel plates, in a concentric shape. A plurality of slots 20 extending in the axial direction are formed in the inner peripheral portion of the stator core 16, whereby the inner peripheral portion of the stator core 16 has a large number of stator teeth 21 facing the rotor 14. Is configured. The armature windings 18 are embedded in the plurality of slots 20.

  As shown in FIGS. 1 and 2, the rotor 14 includes a rotating shaft 22 that is rotatably supported at both ends by bearings (not shown), and a cylindrical rotor fixed to a substantially central portion in the axial direction of the rotating shaft. It has an iron core 24 and a plurality of permanent magnets embedded in the rotor iron core, and is arranged coaxially with a slight gap inside the stator 12.

  The rotor core 24 is configured as a laminated body in which a large number of magnetic materials, for example, annular magnetic steel sheets, are laminated concentrically. The rotor core 24 has an easy magnetization axis (portion where magnetic flux easily passes) d and a hard magnetization axis (portion where magnetic flux does not easily pass) q extending in the radial direction or radial direction of the rotor core, respectively. The q axis and the q axis are formed alternately in the circumferential direction of the rotor core 24 and at a predetermined phase. The rotary electric machine 10 of the present embodiment has been described in the case of eight poles and has eight d-axes, but can be similarly applied to other pole numbers.

  In the rotor core 24, two magnet embedded holes 6a are formed on both sides of each d axis, and one magnet embedded hole 6b is formed on each d axis. Each magnet embedding hole 6a, 6b extends through the rotor core 24 in the axial direction. The two magnet embedding holes 6a formed on both sides of each d-axis are arranged in a substantially V shape, for example, when viewed in a plane orthogonal to the central axis of the rotor core 24. Here, the inner peripheral end of the magnet embedding hole 6 a is adjacently opposed across the d-axis, and the outer peripheral end is positioned away from each other along the circumferential direction of the rotor core 24. The magnet embedding hole 6b extends perpendicular to the d-axis and is provided adjacent to the inner peripheral side ends of the two magnet embedding holes 6a.

  The permanent magnet is a permanent magnet 3 (hereinafter referred to as a variable magnetic force magnet) having a small product of coercive force and magnetization direction thickness, and a permanent magnet (hereinafter referred to as a fixed magnetic magnet) having a large product of coercive force and magnetization direction thickness. 4a and 4b.

  The two fixed magnetic magnets 4 b are inserted into the magnet embedding holes 6 a and embedded in the rotor core 24. The other fixed magnetic magnet 4 a is inserted into the magnet embedding hole 6 a and embedded in the rotor core 24. The variable magnetic force magnet 3 is inserted into the magnet embedding hole 6 a and embedded in the rotor core 24. The variable magnetic force magnet 3 is arranged in close contact with the fixed magnetic force magnet 4a in the magnet embedding hole 6a.

  Each permanent magnet 3, 4 a, 4 b is, for example, formed in an elongated bar shape having a rectangular cross section, and has a length substantially equal to the axial length of the rotor core 24. Each permanent magnet 3, 4 a, 4 b is embedded over almost the entire length of the rotor core 24.

  The two fixed magnetic magnets 4b located on both sides of the d-axis are arranged side by side in a substantially V shape. The two fixed magnetic magnets 4 b are magnetized so that the magnetization directions are opposite in the circumferential direction of the rotor core 24. The fixed magnetic magnet 4a and the variable magnetic magnet 3 are arranged orthogonal to the d axis. The fixed magnetic magnet 4a and the variable magnetic magnet 3 are magnetized so that the magnetization directions are the same, and are magnetized in a direction parallel to the d-axis here.

  By arranging the plurality of permanent magnets 3, 4 a, 4 b as described above, the regions on each d-axis form the magnetic pole 7 in the outer peripheral portion of the rotor core 24, and the regions on each q-axis are the portions between the magnetic poles. 11 is formed.

  A cavity is formed at the ends of the variable magnetic magnet 3 and the fixed magnetic magnets 4a and 4b so that the magnetic flux passing through the rotor core 24 passes through the portions of the variable magnetic magnet 3 and the fixed magnetic magnets 4a and 4b in the thickness direction. 6 is provided. The magnetic pole 7 of the rotor core 24 is formed so as to be surrounded by one variable magnetic magnet 3 and three fixed magnetic magnets 4a and 4b. The central axis direction of the magnetic pole 7 of the rotor core 24 is the d axis, and the central axis direction between the magnetic poles is the q axis.

  The variable magnetic force magnet 3 can be a ferrite magnet, an alnico magnet, or an SmCo-based magnet with a small coercive force. The fixed magnetic magnet 4a is a SmCo magnet having a high coercivity, and the fixed magnetic magnet 4b is an NdFeB magnet or the same SmCo magnet as the fixed magnetic magnet 4a. In the present embodiment, the coercivity of the ferrite magnet is 300 kA / m, and the coercivity of the SmCo permanent magnet and the NdFeB magnet having high coercivity is 1500 kA / m.

  In this embodiment, the variable magnetic force magnet 3 uses a ferrite magnet, and the fixed magnetic force magnet 4a is always within the full range of the maximum operating temperature of the rotating electrical machine, for example, 0 to 150 ° C. Also, a magnet having a large coercive force, for example, an SmCo-based magnet is used. Here, since the magnetization direction thickness of the fixed magnetic force magnet 4a and the variable magnetic force magnet 3 are substantially equal, the fixed magnetic force magnet 4a has a product of the coercive force and the magnetization direction thickness over the entire range within the maximum operating temperature range. It is larger than the product of the coercive force and the magnetization direction thickness of the variable magnetic magnet 3. The SmCo magnet is an SmCo (Fe · Cu · Zr) magnet, for example, an Sm iron Co magnet, a rare earth / iron / nitrogen magnet, or an SmFeN magnet with increased iron distribution and reduced Co distribution ( Samarium, iron-nitrogen, elementary magnets, etc.).

  The variable magnetic magnet 3 and the fixed magnetic magnet 4a are superposed in the magnetization direction of each magnet to constitute one magnet. That is, the variable magnetic force magnet 3 and the fixed magnetic force magnet 4a have the same magnetization direction and are magnetically arranged in series with respect to the magnetic circuit for forming the magnetic pole. The magnets stacked in series are arranged in the rotor core 24 at a position where the magnetization direction is the d-axis direction (here, approximately the radial direction of the rotor).

  On the other hand, the fixed magnetic magnet 4b is disposed on both sides of the magnet in which the variable magnetic magnet 3 and the fixed magnetic magnet 4a are stacked in series at a position where the magnetization direction is the d-axis direction. The two fixed magnetic magnets 4b constitute a parallel circuit on the magnetic circuit with respect to the permanent magnets 3 and 4a stacked in series. That is, on the magnetic circuit for forming the magnetic poles, the fixed magnetic force magnet 4a is arranged in series with the variable magnetic force magnet 3, and the fixed magnetic force magnet 4b is arranged in parallel.

  As shown in FIG. 2, all or a part of the magnetic flux flowing outside the surface perpendicular to the magnetization direction of the variable magnetic force magnet 3 embedded in the rotor core 24 when viewed from the outer peripheral surface side of the rotor core 24. Is provided with a short-circuit coil 8. At this time, the short-circuit coil 8 is arranged so as to be perpendicular to the central axis in the q-axis direction. The short-circuit coil 8 is composed of a ring-shaped conductive member, and is mounted so as to be fitted into a hole provided at a position on the edge of the cavity 6 provided in the rotor core 24 and the q-axis direction iron core substantially on the q-axis line. To do. It is also possible to manufacture by casting a conductive member melted at a high temperature into the hole of the rotor core 24. The short-circuit coil 8 is provided in a magnetic path portion excluding the variable magnetic force magnet 3.

  The short-circuit coil 8 generates a short-circuit current by a magnetic flux generated when a d-axis current is passed through the armature winding 18 of the stator 12. It is preferable that the short-circuit current flowing in the short-circuiting coil 8 flows within 1 second with such strength that the magnetization of the variable magnetic magnet 3 to be irreversibly changed, and then attenuates 50% or more within 1 second. Further, if the inductance value and the resistance value of the short-circuiting coil 8 are set to such values that a short-circuit current that changes the magnetization of the variable magnetic force magnet 3 flows, the efficiency is good.

  An induced current is induced in the short-circuit coil 8 by the magnetizing current flowing in the armature winding 18 of the stator 12, and a magnetic flux penetrating the short-circuit coil 8 is formed by the induced current. In addition, the magnetization direction of the variable magnetic force magnet 3 is irreversibly changed by the magnetization current flowing through the armature winding 18.

  That is, for the variable magnetic force magnet 3 and the fixed magnetic force magnet 4a, during operation of the rotating electrical machine 10, the variable magnetic force magnet 3 is magnetized by a magnetic field generated by the d-axis current, and the amount of magnetic flux is irreversibly changed. In that case, the torque of the rotating electrical machine 10 is controlled by the q-axis current while the d-axis current for magnetizing the variable magnetic force magnet 3 is supplied.

  Further, the magnetic flux generated by the d-axis current causes the interlinkage magnetic flux of the armature winding 18 generated by the current (the total current obtained by combining the q-axis current and the d-axis current) and the variable magnetic force magnet 3 and the fixed magnetic force magnets 4a and 4b. The interlinkage of the entire armature winding composed of the amount, that is, the magnetic flux generated in the armature winding 18 by the total current of the rotating electrical machine and the magnetic flux generated by the two or more kinds of permanent magnets 4a, 4b on the rotor 14 side. The amount of magnetic flux is changed almost reversibly.

  In the present embodiment, the variable magnetic force magnet 3 is irreversibly changed by a magnetic field generated by an instantaneous large d-axis current. In this state, operation is carried out by continuously supplying a d-axis current in a range where little or no irreversible demagnetization occurs. At this time, the d-axis current acts to adjust the terminal voltage by advancing the current phase.

  Further, an operation control method is performed in which the polarity of the variable magnetic force magnet 3 is reversed with a large d-axis current to advance the current phase. Thus, since the polarity of the variable magnetic force magnet 3 is reversed by the d-axis current, even if a negative d-axis current that reduces the terminal voltage is passed, the variable magnetic force magnet 3 is not demagnetized but increased. Become. That is, the magnitude of the terminal voltage can be adjusted without demagnetizing the variable magnetic force magnet 3 with a negative d-axis current.

  In a general magnet motor, since the polarity of the magnet is not reversed, there is a problem that the magnet is irreversibly demagnetized when the d-axis current is increased by advancing the current phase. However, in this embodiment, the variable magnetic force magnet 3 It is possible to advance the phase by reversing the polarity of.

(Basic action)
Next, the operation of the rotating electrical machine according to the first embodiment will be described.
In the present embodiment, a magnetic field is formed by passing a pulsed current having an energization time of an extremely short time (about 0.1 ms to 100 ms) through the armature winding 18 of the stator 12, and a magnetic field is applied to the variable magnetic force magnet 3. Make it work. A pulse current that forms a magnetic field for magnetizing the variable magnetic force magnet 3 is a d-axis current component of the armature winding 18 of the stator 12.

  If the thicknesses of the two types of variable magnetic magnet 3 and fixed magnetic magnet 4a are substantially equal, the change in the magnetization state of the permanent magnet due to the applied magnetic field due to the d-axis current varies depending on the magnitude of the coercive force. That is, the change in the magnetization state of the permanent magnet due to the working magnetic field can be estimated by the product of the coercive force and the thickness of the permanent magnet. In the present embodiment, the coercive force of the variable magnetic magnet (ferrite magnet) 3 is 300 kA / m, and the coercive force of the fixed magnetic magnet (SmCo magnet) 4a is 1500 kA / m. The permanent magnets 3 and 4a have the same magnet thickness in the magnetization direction of 5 mm. The magnetomotive force required for magnetization is estimated by the product of the magnetic field required for magnetization and the thickness of the permanent magnet. If the 90% magnetization magnetic field of the ferrite magnet is about 600 kA / m, the magnetomotive force required for magnetization is 600 kA / m × 5. X0.001 = 3000A. On the other hand, if the 90% magnetization magnetic field of the SmCo magnet is about 3000 kA / m, the magnetomotive force required for magnetization is 3000 kA / m × 5 × 0.001 = 15000 A.

  The magnetomotive force required to change the magnetic force of the ferrite magnet that is the variable magnetic magnet 3 is about 20% of that of the SmCo magnet that is the fixed magnetic magnet 4a. Therefore, the magnetic force of the SmCo magnet can be maintained unchanged with a current that can change the magnetic force of the ferrite magnet. Thus, when these magnets are combined in series to form a magnet, the total flux linkage of the permanent magnet can be adjusted by maintaining the magnetic force of the SmCo magnet as a base and changing the magnetic force of the ferrite magnet.

  First, a negative d-axis current that generates a magnetic field in a direction opposite to the magnetization direction of the magnet is applied to the armature winding 18 in a pulsed manner. If the magnetic field in the magnet changed by the negative d-axis current becomes 300 kA / m or more, the coercive force of the ferrite magnet is 300 kA / m, so that the magnetic force of the ferrite magnet is irreversibly greatly reduced. On the other hand, since the coercive force of the SmCo magnet is 1500 kA / m, the magnetic force does not decrease irreversibly. As a result, when the pulsed d-axis current becomes zero, only the ferrite magnet is demagnetized, and the amount of interlinkage magnetic flux by the magnet of the entire magnetic pole can be reduced.

  Next, a positive d-axis current that generates a magnetic field in the same direction as the magnetization direction of the permanent magnets 3, 4 a is passed through the armature winding 18. A magnetic field necessary for magnetizing the variable magnetic magnet (ferrite magnet) 3 is generated. If the magnetic field in the variable magnetic force magnet 3 changed by the positive d-axis current is 600 kA / m, the demagnetized variable magnetic force magnet 3 is magnetized to generate a maximum magnetic force. On the other hand, since the coercive force of the fixed magnetic magnets (SmCo magnets) 4a and 4b is 1500 kA / m, the magnetic force does not change irreversibly. As a result, when the pulsed positive d-axis current becomes zero, only the variable magnetic force magnet 3 is magnetized, and the amount of flux linkage by the magnets of the entire magnetic pole can be increased. This makes it possible to return to the original maximum flux linkage.

  As described above, an instantaneous magnetic field caused by the d-axis current is applied to the variable magnetic magnet (ferrite magnet) 3 and the fixed magnetic magnets (SmCo magnets) 4a and 4b, thereby irreversibly changing the magnetic force of the variable magnetic magnet 3. Thus, it is possible to arbitrarily change the total flux linkage of the permanent magnets of the entire magnetic pole.

  In this case, the variable magnetic force magnet 3 is magnetized so that the magnetic flux of the permanent magnet of the magnetic pole is added at the time of the maximum torque of the permanent magnet type rotating electric machine, and at a light load with a small torque or in the middle speed rotation range and the high speed rotation range. The variable magnetic force magnet 3 is magnetized by a magnetic field generated by an electric current to reduce the magnetic flux. Further, when the rotor 14 reaches the maximum rotation speed in a state where the amount of interlinkage magnetic flux is minimized by irreversibly changing the permanent magnet of the magnetic pole, an induced electromotive force generated by the permanent magnet is an inverter that is a power source of the rotating electrical machine 10. It is below the withstand voltage of electronic components.

(Operation of series arrangement)
The operation of the two types of variable magnetic magnets 3 and fixed magnetic magnets 4a magnetically arranged in series will be described in detail.
Fig.3 (a) is a figure in the case of obtaining the maximum amount of flux linkage before demagnetization. In this case, since the magnetization directions of the two types of variable magnetic magnet 3 and fixed magnetic magnet 4a are the same, the magnetic fluxes of both permanent magnets 3 and 4a are added together to obtain the maximum amount of magnetic flux.

  FIG. 3B shows a state at the time of demagnetization, and the armature winding 18 generates a magnetic field in a direction opposite to the magnetization direction of both the variable magnetic magnet 3 and the fixed magnetic magnet 4a from the d-axis direction. A negative d-axis current is applied to the armature winding in a pulse manner. If the magnetic field in the magnet changed by the negative d-axis current becomes 175 kA / m, the coercive force of the variable magnetic magnet 3 (ferrite magnet) is 300 kA / m, so the magnetic force of the variable magnetic magnet 3 is irreversibly. Decrease significantly. In this case, the magnetic field from the fixed magnetic field magnet 4a laminated on the variable magnetic field magnet 3 is applied to the variable magnetic field magnet 3, which cancels out the magnetic field applied from the d-axis direction for demagnetization. For this reason, a larger magnetizing current is required, but the magnetizing current for demagnetization is smaller than that at the time of magnetizing, so the increase in magnetizing current is small.

  FIG. 3C shows a state in which the magnetic force of the variable magnetic force magnet 3 in a reverse magnetic field is reduced by a negative d-axis current. Although the magnetic force of the variable magnetic force magnet 3 is irreversibly significantly reduced, the magnetic force is not irreversibly lowered because the coercive force of the fixed magnetic force magnet 4a (SmCo magnet) is 1500 kA / m. As a result, when the pulsed d-axis current becomes zero, only the variable magnetic force magnet 3 is demagnetized, and the amount of interlinkage magnetic flux by the entire magnet can be reduced.

  FIG. 3D shows a state in which the magnetic force of the variable magnetic force magnet 3 in the reverse magnetic field is magnetized in the reverse direction by the negative d-axis current, and the interlinkage magnetic flux by the entire magnet is minimized. If the magnitude of the negative d-axis current generates a magnetic field of 600 kA / m necessary for magnetizing the variable magnetic force magnet 3, the demagnetized variable magnetic force magnet 3 is magnetized to generate a magnetic force. Occur. In this case, since the magnetization directions of the two types of variable magnetic magnet 3 and fixed magnetic magnet 4a are opposite, the magnetic fluxes of both permanent magnets are subtracted, and the magnetic flux is minimized.

  FIG. 3E shows a state in which a magnetic field is generated in order to reduce the magnetic force of the variable magnetic magnet 3 whose polarity is reversed by a negative d-axis current. A positive d-axis current that generates a magnetic field in the magnetization direction of the fixed magnetic force magnet 4 a is applied to the armature winding 18 in a pulsed manner. The magnetic force of the variable magnetic magnet 3 in which the polarity of the magnetic field in the magnet changed by the positive d-axis current is reversed is irreversibly greatly reduced. In this case, the magnetic field from the fixed magnetic magnet 4a stacked on the variable magnetic magnet 3 is added to the magnetic field generated by the magnetizing current (a biased magnetic field acts on the variable magnetic magnet 3 from the fixed magnetic magnet 4a). Demagnetization of the variable magnetic force magnet 3 is easily performed.

  FIG. 3F shows a state in which the magnetic force of the variable magnetic magnet 3 whose polarity is reversed by a magnetic field due to a positive d-axis current is reduced. The magnetic field generated by the fixed magnetic force magnet 4a is also added to the magnetic field generated by the positive d-axis current that irreversibly decreases the magnetic force of the variable magnetic force magnet 3. Therefore, even when a large magnetizing current is usually required, an increase in the magnetizing current can be suppressed by the action of the fixed magnetic magnet 4a.

  FIG. 3G shows a state in which the variable magnetic force magnet 3 is magnetized in the reverse direction (polarity is reversed again) by the positive d-axis current, and the linkage flux of the entire magnet is maximized. Since the magnetization directions of the variable magnetic magnet 3 and the fixed magnetic magnet 4a are the same, the magnetic fluxes of both permanent magnets are added together to obtain the maximum amount of magnetic flux.

  FIG. 4 is a conceptual diagram of a demagnetization curve common to permanent magnets. The coercive force of a permanent magnet changes depending on its temperature, and the coercive force tends to decrease as the temperature increases. In rare earth permanent magnets with high magnetic flux density, NdFeB magnets use Dy elements to suppress the decrease in coercive force, but the coercivity reduction rate due to the temperature rise of the permanent magnet is 1.5% of that of SmCo magnets. It will be about double. Dy element is a very valuable material with limited country of origin among rare earths. If the amount of Dy element used is reduced, the difference becomes more than twice. For example, a typical NdFeB magnet has a coercive force at 20 ° C. of 1500 ka / m, whereas at 150 ° C., the coercive force decreases to 500 kA / m. On the other hand, in a typical SmCo magnet, the coercive force at 20 ° C. is 1500 kA / m, whereas at 150 ° C., the coercive force decreases only to 1150 kA / m.

  Therefore, when an NdFeB magnet having a large coercive force drop is used as the fixed magnetic force magnet 4a, if the rotor core 24 or the fixed magnetic force magnet 4a magnetizes the variable magnetic force magnet 3 in a high temperature state, the coercive force of the variable magnetic force magnet is 300 kA / With respect to m, the coercive force of the fixed magnetic magnet 4a in a high temperature state is at a level equivalent to 500 kA / m. Since the magnetic field of about twice the holding force is required to increase / decrease the variable magnet, the fixed magnet 4a, which should not be irreversibly demagnetized by the increase / decrease of the variable magnet, is irreversibly demagnetized and all magnets are generated. The amount of magnetic flux decreases and the performance of the rotating electrical machine decreases.

  According to this embodiment, as the magnet of the fixed magnetic force magnet 4a, a permanent coercive force that always maintains a coercive force larger than the coercive force of the variable magnetic force magnet 3 within the maximum operating temperature of the rotating electrical machine 10, for example, in the range of 150 ° C. A magnet is used. For example, as the fixed magnetic magnet 4a, an SmCo permanent magnet that is less affected by a decrease in coercive force due to temperature is used. As a result, even when the rotor core 24 or the fixed magnetic magnet 4a is magnetized in a high temperature state, the variable magnetic magnet 3 and the fixed magnetic magnet 4a have a large difference in coercive force even if the magnetization direction thickness is the same. The fixed magnetic magnet 4a is not irreversibly demagnetized. Therefore, it is possible to easily perform magnetization in a high temperature state.

(Operation of variable magnetic magnet)
Next, the operation of the variable magnetic force magnet 3 will be described. FIG. 5 is a graph showing magnetic characteristics (relationship between coercive force and magnetic flux density) of typical magnets such as an NdFeB magnet, a ferrite magnet, an alnico magnet, a Samacoba (SmCo) magnet, and a low coercivity Samacoba magnet. . Among these, in this embodiment, the NdFeB magnet is used as the fixed magnetic magnet 4b, the SmCo magnet is used as the fixed magnetic magnet 4a, the ferrite magnet, the alnico magnet is used as the variable magnetic magnet 3, and the SmCo magnet (samarium cobalt magnet is set with a weak coercive force). ) Can be used. In another embodiment, the ferrite magnet 3 may be used as the variable magnetic magnet 3, the SmCo magnet may be used as the fixed magnetic magnet 4a, and the NdFeB magnet may be used as the fixed magnetic magnet 4b.

  Even if the variable magnetic force magnet 3 has a low coercive force, the variable magnetic force magnet 3 has a high magnetic flux density when only the variable magnetic force magnet 3 is in a state. However, when the fixed magnetic force magnet 4b is magnetically arranged in parallel, the variable magnetic force magnet 3 is variable by its action. The operating point of the magnetic magnet 3 is lowered, and the magnetic flux density is lowered. On the other hand, in the state in which the variable magnetic magnet 3 and the fixed magnetic magnet 4a are stacked in series, the operating point of the magnet of the variable magnetic magnet 3 is increased by the action of the fixed magnetic magnet 4a, and the magnetic flux density is increased.

  That is, the operating point of the Alnico magnet or SmCo magnet, which is a magnet having a low coercive force and a high magnetic flux density, is on the high magnetic flux density side (A and B in FIG. 5) when only the variable magnetic force magnet 3 is used. In a state where the magnets 4b are arranged in parallel, the magnetic flux decreases to the low magnetic flux density side (A ′, B ′ in FIG. 5). However, in the state where the variable magnetic force magnet 3 and the fixed magnetic force magnet 4a are stacked in series as in the present embodiment, the direction of the magnetic field of the fixed magnetic force magnet 4b arranged in parallel and the fixed magnetic force magnet 4a arranged in series. Are opposite directions, the two magnetic fields cancel each other, and the operating point of the variable magnetic force magnet 3 moves to the high magnetic flux density side (A ″, B ″ in FIG. 5).

  As can be seen from this graph, when an Alnico magnet or SmCo magnet is used alone as the variable magnetic force magnet 3, in order to lower the magnetic flux density from the operating points A and B, the coercive force can only be overcome. It is necessary to generate a magnetic field by the d-axis current of the armature winding 18 as a magnetic force, and a large d-axis current is required.

  However, as in the present embodiment, the fixed magnetic magnets 4b and 4b magnetically arranged in parallel with the variable magnetic path magnet 3 and the fixed magnetic magnets 4a arranged in series are used for the variable magnetic magnet 3. Since the operating point moves to A ″ in the figure, the magnetic flux density decreases abruptly by only slightly changing the strength of the magnetic field. Due to this, the d-axis current of the armature winding When the magnetic force of the variable magnetic force magnet 3 decreases due to the reverse magnetic field, the change in the magnetic flux density can be increased. Therefore, the amount of flux linkage by the entire permanent magnet arranged in the magnetic pole is increased by a small d-axis current. Can be changed.

  Since the ferrite magnet has a larger coercive force than the alnico magnet, the magnetizing current required when the polarity is reversed in the direction of increasing the flux linkage of the permanent magnet is increased. However, in this embodiment, the magnetic force can be reversed with a small magnetization current by the action of the fixed magnetic magnets 4a arranged in series.

  This point is the same when the ferrite magnet shown in FIG. 5 is used as the variable magnetic force magnet 3, and there is no abrupt change like the alnico magnet or the SmCo magnet, but compared with the case where the ferrite magnet is used alone, Since the operating point C ″ is lowered, the magnetic flux density can be lowered with a small d-axis current.

(Action of short circuit coil)
The operation of the short-circuit coil 8 will be described with reference to FIG.
The variable magnetic magnet 3 and the fixed magnetic magnets 4a and 4b are embedded in the rotor core 24 to constitute a magnetic circuit. Therefore, the magnetic field generated by the d-axis current described above acts not only on the variable magnetic force magnet 3 but also on the q-axis core portion of the rotor core 24. Originally, the magnetic field generated by the d-axis current is performed in order to change the magnetization of the variable magnetic force magnet 3.

  Therefore, the magnetic field generated by the d-axis current may be prevented from acting on the iron core portions corresponding to the q-axis of the rotor core 24 on both sides of the variable magnetic force magnet 3 and concentrated on the variable magnetic force magnet 3. In the present embodiment, the short-circuit coil 8 is disposed on the q-axis portion of the rotor core 24. The short-circuit coil 8 is disposed so as to surround a portion other than the variable magnetic force magnet 3. When the magnetic field generated by the d-axis current acts on the q-axis equivalent portion of the rotor core 24, an induced current that cancels the magnetic field flows through the short-circuit coil 8. Therefore, the magnetic field caused by the d-axis current and the magnetic field caused by the short-circuit current act on the q-axis equivalent portion of the rotor core 24, and the magnetic field hardly increases or decreases. Furthermore, the magnetic field due to the short-circuit current also acts on the variable magnetic force magnet 3 and is in the same direction as the magnetic field due to the d-axis current.

Therefore, the magnetic field that magnetizes the variable magnetic force magnet 3 is strengthened, and the variable magnetic force magnet 3 can be magnetized with a small d-axis current. Further, the portion corresponding to the q-axis of the rotor core 24 is not affected by the d-axis current due to the short-circuit coil, and the magnetic flux hardly increases, so that the magnetic saturation of the armature core due to the d-axis current can be reduced.

According to the permanent magnet type rotating electrical machine 10 configured as described above, the following effects can be obtained.
(1) Since the coercive force of the fixed magnetic magnet arranged in series with the variable magnetic force magnet with respect to the magnetic circuit for constituting the magnetic pole of the rotor is extremely high, even if the rotor or permanent magnet is magnetized in a high temperature state, The fixed magnet can be prevented from being irreversibly demagnetized, and a decrease in output due to magnetization at a high temperature can be prevented.

(2) Since the increase in magnetizing current at the time of magnetizing can be suppressed, there is no need to increase the size of the inverter for driving the permanent magnet type rotating electrical machine, and the current inverter can be used as it is to improve the operation efficiency. It becomes.

(3) Total interlinkage magnetic flux generated from a composite magnet including the variable magnetic magnet 3 and the fixed magnetic magnet 4 arranged in series in a magnetic circuit by irreversibly changing the variable magnetic magnet 3 with the d-axis current. The amount can be adjusted over a wide range.

(4) The adjustment of the total interlinkage magnetic flux of the permanent magnet makes it possible to adjust the voltage of the rotating electrical machine over a wide range, and the magnetization is always weakened by performing a pulse-like current in an extremely short time. Since it is not necessary to continue the flow, the loss can be greatly reduced. Further, since it is not necessary to perform the flux-weakening control as in the prior art, harmonic iron loss due to the harmonic magnetic flux does not occur. As described above, the rotating electrical machine according to the present embodiment enables high-output, wide-range variable speed operation from low speed to high speed, and high efficiency in a wide operation range.

(5) Regarding the induced voltage due to the permanent magnet, the variable magnetic force magnet 3 can be magnetized with a negative d-axis current to reduce the total interlinkage magnetic flux of the permanent magnet. And the reliability is improved.

(6) In a state where the rotating electrical machine is rotated with no load, the total magnetic flux linkage of the permanent magnet can be reduced by magnetizing the variable magnetic force magnet 3 with a negative d-axis current. As a result, the induced voltage is remarkably lowered, and there is almost no need to constantly apply a weak magnetic flux current for lowering the induced voltage, thereby improving the overall efficiency. In particular, when the rotating electric machine of the present embodiment is mounted on a commuter train that has a long coasting operation time, the overall driving efficiency is greatly improved.

Next, a permanent magnet type rotating electrical machine according to another embodiment will be described.
In the embodiments described below, the same parts as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

(Second Embodiment)
FIG. 7 is a cross-sectional view showing a part of the rotor and the stator in the permanent magnet type rotating electric machine according to the second embodiment. According to the second embodiment, as shown in FIG. 7, in the rotor core 24, two magnet embedded holes 6a are formed on both sides of the d-axis so as to be substantially V-shaped. A fixed magnetic force magnet 4b is embedded in the outer peripheral portion of each magnet embedded hole 6a, and a variable magnetic force magnet 3 and a fixed magnetic force magnet 4a are embedded in series in a magnetic circuit manner in the inner peripheral portion. An insulating plate 5 is embedded between the variable magnetic magnet 3, the fixed magnetic magnet 4a, and the fixed magnetic magnet 4b.

  The insulating plate 5 is disposed on a plane parallel to the magnetization directions of the variable magnetic magnet 3 and the fixed magnetic magnet 4a, and magnetically insulates the variable magnetic magnet 3 and the fixed magnetic magnet 4a from the fixed magnetic magnet 4b. The fixed magnetic magnet 4 b is arranged in parallel with the variable magnetic magnet 3 on the magnetic circuit for constituting the magnetic pole 7. The variable magnet 3, the fixed magnet 4 a, the insulating plate 5, and the fixed magnet 4 b constitute a composite magnet 9. The two composite magnets 9 are arranged in a V shape with the fixed magnetic force magnet 4 b as the outer diameter side with respect to the d-axis, which is substantially the central axis of the magnetic pole 7, and constitute the magnetic pole 7 of the rotor 14. The fixed magnetic magnet 4a arranged in series with the variable magnetic magnet 3 uses a magnet having a coercivity higher than that of the variable magnetic magnet, for example, an SmCo-based magnet, at all times within the maximum operating temperature range of the rotating electrical machine. ing.

  In the second embodiment configured as described above, the variable magnetic force magnet 3 is disposed in the magnetic pole 7, and the fixed magnetic force magnet 4a is disposed in series with the variable magnetic force magnet 3 in a magnetic circuit manner. Since the fixed magnetic magnets 4b are arranged in parallel in a circuit, the basic configuration is the same as that of the first embodiment described above. For this reason, the amount of magnetic flux of the permanent magnet can be irreversibly changed by magnetization, and high-efficiency operation is possible. In addition, by using the SmCo rare earth magnet as the fixed magnetic force magnet 4a, magnetization can be performed even in a high-temperature operation state. Further, problems such as irreversible demagnetization of the fixed magnetic force magnet 4a due to magnetization in a high temperature state do not occur. Furthermore, by using a plurality of magnets as an integrated composite magnet 9, the assembly of the rotating electrical machine is facilitated, and the number of processing of the magnet embedding holes 6a of the rotor core 24 can be reduced.

(Third embodiment)
FIG. 8 is a cross-sectional view showing a part of the rotor and the stator in the permanent magnet type rotating electric machine according to the second embodiment. According to the second embodiment, as shown in FIG. 8, in the rotor core 24, two magnet embedded holes 6a are formed on both sides of the d-axis so as to be substantially V-shaped. The fixed magnetic magnet 4b is embedded in the inner peripheral side portion of each magnet embedding hole 6a, and the variable magnetic magnet 3 and the fixed magnetic magnet 4a are embedded in series in a magnetic circuit manner in the outer peripheral portion. An insulating plate 5 is embedded between the variable magnetic magnet 3, the fixed magnetic magnet 4a, and the fixed magnetic magnet 4b.

  The insulating plate 5 is disposed on a plane parallel to the magnetization directions of the variable magnetic magnet 3 and the fixed magnetic magnet 4a, and magnetically insulates the variable magnetic magnet 3 and the fixed magnetic magnet 4a from the fixed magnetic magnet 4b. The fixed magnetic magnet 4 b is arranged in parallel with the variable magnetic magnet 3 on the magnetic circuit for constituting the magnetic pole 7. The variable magnet 3, the fixed magnet 4 a, the insulating plate 5, and the fixed magnet 4 b constitute a composite magnet 9. The two composite magnets 9 are arranged in a V shape with the fixed magnetic force magnet 4 b as the inner diameter side with respect to the substantially central d-axis of the magnetic pole 7, and constitute the magnetic pole 7 of the rotor 14. The fixed magnetic magnet 4a arranged in series with the variable magnetic magnet 3 uses a magnet having a coercivity higher than that of the variable magnetic magnet, for example, an SmCo-based magnet, at all times within the maximum operating temperature range of the rotating electrical machine. ing.

  Also in the third embodiment configured as described above, the same effects as those of the second embodiment described above can be obtained. Furthermore, by arranging relatively weak magnets of the composite magnet 9 at positions on both sides with respect to the outer shape side, that is, the center of the magnetic pole 7, in the air gap portion between the rotor 14 and the stator 12, The directional magnetic flux density distribution becomes a distribution closer to a sine wave than the convex magnetic pole central portion, and the harmonic iron loss can be reduced.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
For example, the permanent magnet type rotating electrical machine is not limited to the inner rotor type, and may be an outer rotor type. The number of magnetic poles, the size, the shape, and the like of the rotor are not limited to the above-described embodiments, and can be variously changed according to the design. Further, the arrangement of the permanent magnets in the rotor core is not limited to the V shape, and for example, the permanent magnets may be arranged in a tangential direction of the concentric circle with the rotation center of the rotor core.

  In the permanent magnet that forms the magnetic pole, the permanent magnet is defined by the product of the coercive force and the thickness in the magnetization direction. Therefore, even if the magnetic poles are formed of the same type of permanent magnet and are formed so as to have different magnetization direction thicknesses, the same operation and effect can be obtained.

  During operation of the rotating electrical machine, the permanent magnet was magnetized by a magnetic field generated by a pulsed d-axis current for a very short time to irreversibly change the amount of magnetic flux of the permanent magnet, and the phase was advanced with respect to the induced voltage of all the magnets. It is good also as a structure which energizes current continuously and changes the amount of flux linkage of the armature winding which arises with an electric current and a permanent magnet. That is, if the amount of magnetic flux of the permanent magnet is reduced by the pulse current and the current phase is further advanced, magnetic flux generated by the current in the opposite direction to the magnetic flux is generated. Terminal voltage can be reduced. Note that advancing the current phase is equivalent to flowing a negative d-axis current component.

  In such current phase advance control, when the current phase is advanced, a d-axis current flows, the magnet is demagnetized, and the amount of magnetic flux is somewhat reduced. However, since the magnetic field is greatly demagnetized by the pulse current, there is an advantage that the reduction of the magnetic flux amount is small in proportion.

3 ... variable magnetic magnet, 4a, 4b ... fixed magnetic magnet, 6a ... magnet embedding hole,
8 ... Short-circuit coil, 10 ... Rotating electric machine, 12 ... Stator, 14 ... Rotor, 16 ... Stator iron core,
18 ... armature winding, 20 ... slot, 22 ... rotating shaft, 24 ... rotor core

Claims (6)

A stator having a stator core and an armature winding attached to the stator core;
A rotor core provided rotatably with respect to the stator, and a rotor having a plurality of permanent magnets embedded in the rotor core to form a plurality of magnetic poles,
During operation, a permanent magnet type rotation that irreversibly changes the amount of magnetic flux of the permanent magnet by magnetizing at least one of the permanent magnets constituting the magnetic pole of the rotor by a magnetic field generated by the current flowing through the armature winding An electric machine,
The plurality of permanent magnets forming the magnetic pole are arranged in series with the variable magnetic force magnet that can irreversibly change the amount of magnetic flux and the magnetic circuit for forming the magnetic pole, and the amount of magnetic flux is fixed. The product of the coercive force and the magnetization direction thickness is greater than the product of the coercivity and the magnetization direction thickness of the variable magnetic magnet over the entire range within the maximum operating temperature range. A permanent magnet type rotating electrical machine characterized by being large. A stator having a stator core and an armature winding attached to the stator core;
A rotor core provided rotatably with respect to the stator, and a rotor having a plurality of permanent magnets embedded in the rotor core to form a plurality of magnetic poles,
During operation, a permanent magnet type rotation that irreversibly changes the amount of magnetic flux of the permanent magnet by magnetizing at least one of the permanent magnets constituting the magnetic pole of the rotor by a magnetic field generated by the current flowing through the armature winding An electric machine,
The plurality of permanent magnets forming the magnetic pole are arranged in series with the variable magnetic force magnet that can irreversibly change the amount of magnetic flux and the magnetic circuit for forming the magnetic pole, and the amount of magnetic flux is fixed. The fixed magnetic magnet includes a SmCo-based magnet or a rare earth / iron / nitrogen-based magnet whose coercive force is larger than the coercive force of the variable magnetic magnet in the entire range within the maximum operating temperature range. A permanent magnet type rotating electrical machine characterized by being an SmFeN-based magnet (samarium / iron-nitrogen / elemental magnet).   The permanent magnet type rotating electric machine according to claim 1 or 2, wherein the variable magnetic magnet and the fixed magnetic magnet that form the magnetic pole are arranged so as to overlap each other in the magnetization direction.   The plurality of permanent magnets forming the magnetic pole include other fixed magnetic magnets that are arranged in parallel with the variable magnetic magnet with respect to the magnetic circuit for forming the magnetic pole and fix the amount of magnetic flux. The permanent magnet type rotating electrical machine according to any one of the above.   The permanent magnet type rotating electrical machine according to claim 3 or 4, wherein the variable magnetic magnet and the fixed magnetic magnet are arranged on a central axis of the magnetic pole, and the magnetization direction is along the central axis direction.   The plurality of permanent magnets forming the magnetic pole include another fixed magnetic magnet that is arranged in parallel with the variable magnetic magnet with respect to the magnetic circuit for forming the magnetic pole and fixes the amount of magnetic flux. The magnetic magnet and the other fixed magnetic magnet are arranged side by side with an insulator to form a composite magnet, and the composite magnet is disposed on both sides of the central axis of the magnetic pole, respectively. The permanent magnet type rotating electric machine described.

Images