JP7140961B2 - motor drive - Google Patents

Description

The present disclosure relates to motors using permanent magnets.

2. Description of the Related Art A technique for changing the magnetic flux density of a permanent magnet using a current flowing through the motor is known (for example, Patent Document 1).

JP 2010-259195 A

In Patent Document 1, prior to magnetization of the permanent magnets, it is determined whether or not the phase of the rotor is within a predetermined range. The present disclosure facilitates an irreversible increase in the residual magnetic flux density of the permanent magnets of the motor.

A motor driving device (10) is a device for driving motors (1A, 1B). The motors (1A, 1B) have a residual magnetic flux density (Br) and field elements (11A, 11B) having permanent magnets (111, 112) that generate a field magnetic flux (φr), and an alternating current first A current (I1) flows to generate an alternating magnetic field, and a second current (I2) flows to generate a changing magnetic field that is a magnetic field that irreversibly changes the residual magnetic flux density. and an armature (12) rotated relative to the field element by the alternating magnetic field.

A first aspect of a motor drive device (10) includes an AC power supply (2) for supplying the first current and the second current to the armature winding, and the field magnet for the AC power supply. The second current is supplied to the electric machine in a first state in which a phase difference between a magnetic flux vector representing the magnetic flux (φr) and a magnetic field vector representing the modified magnetic field is within a range in which the residual magnetic flux density is irreversibly increased by the modified magnetic field. A control unit (4) for supplying the first current to the armature winding after supplying the current to the armature winding.

A second aspect of the motor drive device (10) is the first aspect thereof, wherein the control section (4) supplies the AC power supply (2) with a third current that provides the first state. Between the period (0 to t1) in which (I3) flows and the period (t2 to t3) in which the second current (I2) flows, a non-energization period of a predetermined period (t1 to t2) is provided.

A third aspect of the motor drive device (10) is the first aspect thereof, wherein the control section (4) supplies the AC power supply (2) with a third current that provides the first state. The second current (I2) is caused to flow immediately after (I3) is caused to flow.

A fourth aspect of the motor drive device (10) is the first aspect thereof, wherein the motors (1A, 1B) are provided in the refrigeration circuit (9) and serve as compressors for compressing the refrigerant (F). The refrigerating circuit includes an evaporator (94), a condenser (92), and an expansion mechanism (93) through which the refrigerant circulates, and the evaporator, the condenser, the expansion mechanism, and the compressor. The first state is obtained by controlling the pressure difference, which is the difference between the pressure of the refrigerant discharged from the compressor and the pressure of the refrigerant sucked into the compressor, by any one of them.

The present disclosure facilitates an irreversible increase in the residual magnetic flux density of the permanent magnets of the motor.

1 is a sectional view showing the structure of a motor to which the technique described in this embodiment can be applied; FIG. 1 is a sectional view showing the structure of a motor to which the technique described in this embodiment can be applied; FIG. FIG. 10 is a cross-sectional view showing the structure of another motor to which the technology described in this embodiment can be applied; FIG. 10 is a cross-sectional view showing the structure of another motor to which the technology described in this embodiment can be applied; 4 is a vector diagram showing field magnetic fluxes before and after magnetization processing; FIG. FIG. 4 is a vector diagram showing a modified magnetic field; FIG. 4 is a vector diagram showing a modified magnetic field; FIG. 4 is a vector diagram showing a modified magnetic field; FIG. 4 is a vector diagram showing a desirable range for the first state; 1 is a block diagram illustrating the configuration of a motor drive device together with its periphery; FIG. Fig. 4 is a graph showing waveforms of current and its amplitude; Fig. 4 is a graph showing waveforms of current and its amplitude; 4 is a flowchart illustrating processing of the embodiment; Fig. 4 is a graph showing waveforms of current and its amplitude; Fig. 4 is a graph showing waveforms of current and its amplitude; 3 is a block diagram illustrating the configuration of a refrigeration circuit; FIG. 3 is a block diagram showing the internal configuration of the condenser together with its surroundings; FIG. 4 is a graph showing a magnetization curve of a permanent magnet;

1 and 2 are cross-sectional views showing the structure of a motor 1A to which the technology described in this embodiment can be applied. The cross section is perpendicular to the rotation axis J of the motor 1A.

The motor 1A has a field element 11A and an armature 12. FIG. The field element 11A has a core 110 and permanent magnets 111,112. 1 and 2 illustrate a configuration in which the permanent magnets 111 and 112 are embedded in the core 110, and the motor 1A is illustrated as a so-called embedded magnet type synchronous motor, but it may be a surface magnet type synchronous motor. . FIG. 1 illustrates a field element 11A having two pole pairs, in which four permanent magnets 112 are arranged. Permanent magnets 111 are arranged on both sides of one permanent magnet 112 in the circumferential direction about the rotation axis J. As shown in FIG. That is, in FIG. 1, one permanent magnet 111 and two permanent magnets 112 sandwiching it in the circumferential direction are provided in one magnetic pole of the field element 11A.

The field magnetic flux φr applied to the armature 121 is a composite of the field magnetic fluxes generated by the permanent magnets 111 and 112, respectively. Permanent magnets 111 and 112 have residual magnetic flux densities Br1 and Br2 (see also FIG. 18 described later), respectively. The permanent magnets 111 and 112 forming one magnetic pole of the field element 11A can be collectively understood as a permanent magnet having a residual magnetic flux density Br.

An opening 113 is opened in the core 110 parallel to the rotation axis J, and a shaft (not shown) is fixed to the opening 113 .

The armature 12 includes armature windings 121 and teeth 122 , and the armature windings 121 are wound around the teeth 122 . A plurality of teeth 122 may be connected by a back yoke (not shown) on the side opposite to the field element 11A. The teeth 122 are annularly arranged around the field element 11A. Six teeth 122 are provided in FIGS. 1 and 2, and a so-called four-pole, six-slot configuration is exemplified as the configuration of the motor 1A.

In FIGS. 1 and 2 , the armature winding 121 is concentrated winding and provided on the teeth 122 , but the armature winding 121 may be distributed winding. 1 and 2 illustrate the case where the motor 1A has a so-called inner rotor type configuration, it may have an outer rotor type configuration.

An alternating current I1 (not shown in FIGS. 1 and 2; see FIGS. 11, 12, 14, and 15 to be described later) flows through the armature winding 121 to generate an alternating magnetic field (not shown in FIGS. 1 and 2). occurs. The armature 12 is rotated relative to the field element 11A by the alternating magnetic field. For example, the armature 12 is fixed to another member (not shown), and the field element 11A rotates around the rotation axis J.

A current I2 (not shown in FIGS. 1 and 2; see later-described FIGS. 11, 12, 14 and 15) flows through the armature winding 121 to generate a modified magnetic field H2 (see FIG. 2). The changing magnetic field H2 is a magnetic field that irreversibly changes the residual magnetic flux density Br. For example, the residual magnetic flux density Br1 is irreversibly increased by the changing magnetic field H2, and the residual magnetic flux density Br2 is not irreversibly increased by the changing magnetic field H2. For example, the coercive force Hc2 of the permanent magnet 112 is greater than the coercive force Hc1 of the permanent magnet 111 (see also FIG. 18 described later).

When the motor 1A is driven at a high rotational speed, the residual magnetic flux density Br1, and thus the residual magnetic flux density Br, is irreversibly changed (specifically, irreversibly reduced; hereinafter referred to as "demagnetization processing"), and reversed. Electromotive force is reduced. For example, after the motor 1A is driven at a high rotational speed, if it is not necessary to drive the motor 1A at a low rotational speed, the motor 1A may stop while the reduced residual magnetic flux density Br is maintained due to the demagnetization process. be.

Before starting the motor 1A, it is desirable to increase the residual magnetic flux density Br by the modified magnetic field H2 in order to increase the torque when starting the motor 1A. Specifically, it is desirable to irreversibly increase the residual magnetic flux density Br1 (specifically, an irreversible increase; hereinafter referred to as "magnetization treatment").

1 and 2 both show the positional relationship between the field element 11A and the armature 12 before starting the motor 1A and before performing the magnetization process. However, FIG. 1 also shows the modified magnetic field H2 employed in the magnetization process for convenience of explanation.

The structure shown in FIGS. 1 and 2 exemplifies the case where the permanent magnet 112 and the pair of permanent magnets 111 are line-symmetrical in one magnetic pole. Specifically, a structure that is symmetrical with respect to a straight line in the radial direction centered on the rotation axis J and passing through the center of the permanent magnet 112 in the circumferential direction is exemplified. If the residual magnetic flux densities Br1 of the pair of permanent magnets 111 are equal, the field magnetic flux φr is generated along the straight line.

In FIG. 1, the direction M schematically indicates the phase of the field magnetic flux φr before the magnetization process (the phase in the electrical angle; the same shall apply hereinafter) as a geometric angle. Direction D is schematically shown as a direction in which, when a magnetic field is applied in that direction, a magnetic field is generated in the same direction as the direction in which the magnetization directions of the permanent magnets are aligned to the maximum. The directions M and D are shown to coincide because of the symmetry described above.

Generally, the positional relationship between the field element 11A and the armature 12 before the magnetization process is unknown. Therefore, depending on this positional relationship, applying the changing magnetic field H2 may reduce the residual magnetic flux density Br1.

Therefore, the positional relationship between the field element 11A and the armature 12 is in a state (hereinafter referred to as "first A technique for applying the modified magnetic field H2 will now be described. Processing for obtaining the first state is hereinafter referred to as “preprocessing”.

In FIG. 1, a magnetic field (hereinafter referred to as a "pretreatment magnetic field") H3 for keeping the positional relationship between the field element 11A and the armature 12 within the above-described predetermined range is applied to the field element 11A and the armature 12 before application of the magnetic field H3. is shown together with the positional relationship with. In FIG. 1, the phase difference δ, which is the difference between the phase of the field magnetic flux φr and the phase of the pretreatment magnetic field H3, is schematically shown as a geometric angle. However, since the angle appears as a mechanical angle in FIG. 1, the phase difference .delta./Pn (Pn: number of pole pairs (here, 2)) is shown.

The magnitude of the pretreatment magnetic field H3 is desirably smaller than the magnitude of the change magnetic field H2 from the viewpoint of performing the magnetization process appropriately.

The field element 11A having a positional relationship with such a phase difference δ is moved by applying the pretreatment magnetic field H3. The pretreatment magnetic field H3 is generated by a current I3 (not shown in FIGS. 1 and 2, see later-described FIGS. 11, 12, 14, and 15) flowing through the armature winding 121. FIG.

FIG. 2 shows the first state after the pretreatment magnetic field H3 has been applied. The phase difference δ becomes 0 by preprocessing. FIG. 2 also shows the modified magnetic field H2. Here, the residual magnetic flux density Br1 of the pair of permanent magnets 111 in one magnetic pole decreases evenly in the demagnetization process and increases evenly in the magnetization process. The case where D and M are kept consistent is exemplified.

If the permanent magnets 111 and 112 are thus symmetrical in one magnetic pole, the directions D and M will match even before and after the magnetization process. can.

Next, the case where there is no such symmetry will be described. 3 and 4 are sectional views showing the structure of another motor 1B to which the technology described in this embodiment can be applied. The cross section is perpendicular to the rotation axis J of the motor 1B.

The motor 1B has a field element 11B and an armature 12. FIG. The difference between the motor 1B and the motor 1A is the difference between the field element 11B and the field element 11A. The difference between the field element 11B and the field element 11A is the number and arrangement of the permanent magnets 111 and 112 provided in one magnetic pole.

In the field element 11B, permanent magnets 111 and 112 are alternately arranged in the circumferential direction. Therefore, in one magnetic pole, the permanent magnets 111 and 112 are provided adjacently one by one. Therefore, if the permanent magnet 111 is not magnetized after being demagnetized, the phase of the field magnetic flux φr differs from the direction D by the phase difference θ. 3 and 4, the phase difference .theta. is schematically shown as a geometrical angle between the directions M and D. In FIG. However, since the angles appear as mechanical angles in FIGS. 3 and 4, the phase differences .delta./Pn and .theta./Pn (Pn: number of pole pairs (here, 2)) are shown.

As in FIG. 1, FIG. 3 shows the pretreatment magnetic field H3 together with the positional relationship between the field element 11B and the armature 12 before its application. FIG. 4 shows the positional relationship between the field element 11B and the armature 12 after the pretreatment and before the magnetization treatment, together with the modified magnetic field H2.

The phase difference .delta. becomes 0 by the pretreatment, but the phase difference .theta. is maintained before the magnetization treatment. Although this is the same in FIGS. 1 and 2, it was a special case where the phase difference θ is 0, so it did not appear clearly.

In this way, if there is no symmetry between the permanent magnets 111 and 112 in one magnetic pole, the directions D and M remain inconsistent before and after the magnetization process, so the pretreatment magnetic field H3 makes the first state one. cannot be determined to In other words, the first state depends on the residual magnetic flux densities Br1 and Br2 before the magnetization process.

However, in the first state, since the phase difference .theta. is within a predetermined range, the residual magnetic flux density Br1 is not reduced even if the modified magnetic field H2 is used. The maximum value of the phase difference θ can be obtained from the structure of the field element 11B including the magnetic characteristics of the permanent magnets 111 and 112 (magnetization curves including residual magnetic flux densities Br1 and Br2). Therefore, the magnitude of the modified magnetic field H2 required for the magnetization process can also be obtained from the maximum value and the magnetic properties of the permanent magnet 111 .

FIG. 5 is a vector diagram showing the field magnetic flux before and after the magnetization process. However, the directions M and D are shown as phases instead of geometric positions (the same applies to other vector diagrams). A field flux φm with an irreversibly reduced residual flux density Br and a field flux φM with an irreversibly increased residual flux density Br are shown. The magnitude of the field magnetic flux φm is smaller than the magnitude of the field magnetic flux φM.

In FIG. 5, it is assumed that the field flux .phi.m is the field flux .phi.m in which the residual flux density Br has decreased the most, and the field flux .phi.M is the field flux .phi.M in which the residual flux density Br has increased the most. When the direction D matches the phase of the field magnetic flux φM, the phase difference θo between the field magnetic fluxes φm and φM is the maximum value of the phase difference θ described above.

In FIG. 5, the field magnetic flux φr is the field magnetic flux φm in the state before the motor 1 (which collectively refers to the motors 1A and 1B; the same shall apply hereinafter). expressed. As described above, the fact that the direction D and the phase of the field magnetic flux φM match is expressed by adopting the phase of the field magnetic flux φM as the direction D.

6 and 7 are vector diagrams showing the modified magnetic field H2. The magnitude of the magnetic field required to increase the residual magnetic flux density Br1 can be set in advance from the magnetization characteristics of the permanent magnet 111. FIG. The magnitude of this magnetic field is set to the magnitude of the component H2M in the direction D of the modified magnetic field H2.

Since the actual phase difference θ is not detected and the precalculated phase difference θo is known, if the phase of the modified magnetic field H2 is set between the phases of the field magnetic fluxes φm and φM, the required modified magnetic field H2 size is minimal. The magnitude |H2| of the change magnetic field H2 required at this time is expressed by |H2M|/tan(θo/2) using the magnitude |H2M| of the component H2M.

FIG. 7 shows the case where the actual phase difference θ is 0, and the directions D and M match. This corresponds to the case where the permanent magnets 111 and 112 in one magnetic pole are arranged with line symmetry as shown in FIGS. Even in this case, it is clear that the magnetization necessary for increasing the residual magnetic flux density Br1 can be performed with the changing magnetic field H2 of the magnitude of |H2M|/tan(θo/2).

FIG. 8 is a vector diagram showing how the direction of the modified magnetic field H2 is varied. Even if the phase difference θ is anywhere from 0 to θo, the phase of the field magnetic flux φr after the magnetization process is the phase of the field magnetic flux φM (indicated by the direction D2) and the phase of the field magnetic flux φm (indicated by the direction D1 (indicated by ). Thus, the modified magnetic field H2, whose magnitude is |H2M|/tan(θo/2), is the range between the magnetic field H21 with the phase indicated in the direction D1 and the magnetic field H22 with the phase indicated in the direction D2. If it fluctuates over R4, the magnetization process can be performed.

However, from the viewpoint of not moving the position of the field element 11, it is desirable to set the frequency at which the changing magnetic field H2 alternates so high that the motor 1 cannot rotate.

1 to 4 do not show directions that geometrically indicate the phase of the changing magnetic field H2. In FIG. 4 as well, the directions M and D respectively indicate the phase of the field magnetic flux φr before the magnetization process and the above-described direction D. However, in FIG. does not necessarily geometrically represent the relationship between the phase of the modified magnetic field H2 and the phase of the field magnetic flux φr before the magnetization process. The same is true for the geometrical relationship between the direction D and the arrow that schematically indicates the modified magnetic field H2.

In this embodiment, the position of the field element 11 is kept within a predetermined range. Therefore, there is no need to determine whether the position of the field element 11 is within a predetermined range or not, and the irreversible increase in the residual magnetic flux density Br of the permanent magnets 111 and 112 is facilitated.

1 to 4 illustrate the case where the phase difference δ becomes 0 due to the pretreatment magnetic field H3. In this case, the position of the field element 11 immediately before the magnetization process is uniquely determined by the direction M indicating the phase of the field magnetic flux φr before the magnetization process.

However, as the first state, the position of the field element 11 does not necessarily require such uniqueness. It is sufficient that an irreversible increase in the residual magnetic flux density Br is obtained by the modified magnetic field H2.

FIG. 9 is a vector diagram showing a desirable range for the first state. A direction D, a direction M1 indicating the phase of the field magnetic flux φm when the residual magnetic flux density Br decreases the most, and a direction M2 indicating the phase of the field magnetic flux φM when the residual magnetic flux density Br increases the most show.

The magnitude of the phase range that can be magnetized by the changing magnetic field H2 is π in terms of phase difference. A region R1 is a desirable range of the phase of the field magnetic flux φr after the pretreatment, assuming that the residual magnetic flux density Br before the magnetization treatment has already increased the most. A region R2 is a desirable range of the phase of the field magnetic flux φr after pretreatment, assuming that the residual magnetic flux density Br before the magnetization treatment is the lowest value.

It is unknown what value the residual magnetic flux density Br has before the magnetization process. Therefore, the phase of the field magnetic flux φr after preprocessing exists in the phase section represented by the directions M1 and M2. Therefore, the phase of the field magnetic flux φr desirable as the first state obtained by the pretreatment is in the range of the region R0 where the regions R1 and R2 overlap.

Here, the case where the direction M1 leads the direction M2 is illustrated, and the region R0 in this case changes from the phase lagging (π/2−θo) with respect to the direction D to the direction The range is (π-θo) up to a phase that is π/binary with respect to D.

It should be noted that the component in direction D of the modified magnetic field H2 illustrated in the vector diagram of FIG. 6 has magnitude |H2M|. This component can thus be viewed as the magnetic field vector H2M representing the modified magnetic field. Considering this together with the fact that the range of the region R0 can be indicated with reference to the direction D, the first state can be explained as follows using a vector indicating the field magnetic flux φr. can:
A state in which the phase difference between the magnetic flux vector indicating the field magnetic flux φr and the magnetic field vector H2M indicating the modified magnetic field is within a range in which the residual magnetic flux density Br is irreversibly increased by the modified magnetic field.

Then, the magnetization process is performed in such a first state. After performing the magnetization process, an alternating magnetic field for driving the motor 1 is generated.

From the viewpoint of preventing the residual magnetic flux density Br from being irreversibly reduced by the magnetic field indicated by the magnetic field vector H2M, the phase of the magnetic field vector H2M is shifted from the phase delayed by π/2 with respect to the direction D to the direction D to a phase leading by π/2.

The field magnetic flux φr may advance with the phase θo1 with respect to the direction D due to the arrangement of the permanent magnets 111 and 112 and variations in their magnetization states. In this case, the phase of the magnetic field vector H2M changes from the phase lagging by π/2 with respect to the magnetic flux vector indicating the field magnetic flux φr to (π/2-θo1 ) to the leading phase.

FIG. 10 is a block diagram illustrating the configuration of the motor drive device 10 together with its periphery. A motor drive device 10 drives the motor 1 . The motor drive 10 supplies the motor 1, more precisely the armature winding 121, with a current ia. Current ia includes currents I1, I2 and I3 described above.

The motor drive device 10 has an AC power supply 2 , a rectifier circuit 3 and a control section 4 . The control unit 4 causes the AC power supply 2 to supply the current ia to the armature winding 121 in a manner to be described later. The rectifier circuit 3 converts the AC voltage Vi into a DC voltage Vdc. FIG. 10 illustrates a case where the AC voltage Vi is supplied from an AC power supply 8 outside the motor drive device 10 .

FIG. 10 illustrates a case where AC power supply 2 is an inverter that converts DC voltage Vdc to AC voltage Vac. An AC voltage Vac is applied to the motor 1 . For example, if the motor 1 is a three-phase motor, the AC voltage Vac is a three-phase AC voltage and the current I1 is a three-phase AC current.

A control signal G controls the operation of the AC power supply 2 . A control signal G is generated by the control unit 4 and output to the AC power supply 2 . The control unit 4 generates the control signal G using the command value ω* of the rotation speed ω of the motor 1 and the measurement results of the DC voltage Vdc and the current ia. Generally, the generation of the control signal G and the control of the operation of the inverter by the control signal G are well-known techniques, so details thereof will be omitted.

Motor 1 drives load 91 . For example, load 91 is a compressor that compresses refrigerant. The motor 1 can also be included in the compressor.

11 and 12 are graphs showing the waveforms of the current ia and its amplitude |ia|, respectively, with the horizontal axis representing time t. The amplitude |ia| can be understood as the value of the envelope of the waveform of the current ia.

FIG. 11 shows the currents I1, I2 and I3 and their respective amplitudes |I1|, |I2| and |I3| as the breakdown of the current ia. Amplitudes |I1|, |I2|, and |I3| can be understood as values of envelopes of respective waveforms of currents I1, I2, and I3. In FIG. 11, the waveform is shown with the current ia as the current for each phase. FIG. 12 shows the amplitudes |I1|, |I2|, and |I3| as the breakdown of the amplitude |ia|.

The current I3 is exemplified as a current that causes the motor 1 to be DC-excited. The time t is based on the time when the current I3 starts to flow (time 0). Current I3 ceases to flow at time t1. The flow of the current I3 generates the pretreatment magnetic field H3, and the first state described above is obtained.

Since the pretreatment magnetic field H3 is not an alternating magnetic field here, the first state is maintained even after the current I3 stops flowing at time t1. However, since the field element 11 is moved by the pretreatment magnetic field H3, the first state may not be maintained if the motor 1 rotates due to inertia resulting from this movement. Therefore, considering the rotation of the motor 1 due to inertia, it is desirable that the current I3 is supplied for a longer period of time.

After the time t1, the current I2 flows from the time t2 to the time t3, and the magnetization process is performed. The amplitude |I2| reaches the threshold ia0. The threshold value ia0 is the value of the amplitude |I2| required to set the magnitude of the modified magnetic field H2 to the magnitude required for the magnetization process. FIG. 11 illustrates a case where the current I2 is similar to DC excitation and the three-phase current does not alternate. However, when the changing magnetic field H2 fluctuates as illustrated in FIG. 8, the three-phase current may alternate.

After time t3 and after time t4, current I1 flows and an alternating magnetic field is generated. A section is shown here in which the amplitude |I1| increases, and the magnitude of the alternating magnetic field also increases in this section.

FIGS. 11 and 12 illustrate the case where the amplitude |ia| becomes zero from time t1 to time t2 and from time t3 to time t4. Providing such a non-energization period is desirable from the viewpoint of suppressing heat generation of the AC power supply 2 and the motor 1 .

FIG. 13 is a flow chart illustrating the processing of this embodiment. The control unit 4 causes the AC power supply 2 to perform the steps of the flowchart. First, step S1 is executed (see the period from time t0 to t1 in FIGS. 11 and 12). Step S1 is the above-described preprocessing, and thereby obtains the above-described first state. After execution of step S1, a no-energization period (equivalent to the period from time t1 to t2 in FIGS. 11 and 12) is provided in step S2, and magnetization processing is performed in step S3 (see FIGS. 11 and 12). corresponding to the period from time t2 to t3).

After step S3 is executed, a non-energization period (corresponding to the period of time t3 to t4 in FIGS. 11 and 12) is provided in step S4, and then a process for generating an alternating magnetic field ("alternating magnetic field generation process") is performed in step S5. (tentative name) is performed (see FIGS. 11 and 12 after time t4).

However, steps S2 and S4 may be omitted and the no-energization period may not be provided. This is desirable from the viewpoint that it is not necessary to consider the rotation of the motor 1 due to inertia after preprocessing.

14 and 15 are graphs showing waveforms of the current ia and its amplitude |ia|, respectively, and the horizontal axis represents time t. FIGS. 14 and 15 show the case where no non-energization period is provided before and after the magnetization process unlike the case shown in FIGS. 11 and 12. FIG.

The time t is based on the time when the current I3 starts to flow (time 0). Current I3 rises until time t5, and then maintains amplitude |I3| until it stops flowing at time t4. A pretreatment magnetic field H3 is generated by the flow of the current I3, and the first state described above is obtained.

Here, the time t2 to time t3 during which the current I2 flows and the magnetization process is performed is provided between the time t5 and the time t4. After time t4, current I1 flows and an alternating magnetic field is generated. A section is shown here in which the amplitude |I1| increases, and the magnitude of the alternating magnetic field also increases in this section.

The current I3 flowing before time t2 is understood as a current for pretreatment, but the current I3 flowing after time t3 need not be understood as a current for pretreatment. This is because at time t3, the magnetization process has already been performed and the field magnetic flux φM has been obtained.

On the other hand, as described above, there are cases where the field magnetic flux φM is already obtained before the pretreatment, and in this case the pretreatment magnetic field H3 does not interfere with the magnetization process. Therefore, the current I3 that flows after the time t3 also does not interfere with the field magnetic flux φM after the magnetization process.

As described above, the pretreatment magnetic field H3 can be obtained by applying the current I3 for direct-current excitation of the motors 1A and 1B. This DC excitation may be performed so as to generate the pretreatment magnetic field H3 in the direction of one phase, or may be performed by switching the direction. For example, it is assumed that the motors 1A and 1B are three-phase AC motors of U-phase, V-phase, and W-phase, and the phase of the modified magnetic field H2 is matched with the phase of the W-phase. In this case, the DC excitation may be performed only by the W phase, or the DC excitation may be performed in the order of the U phase, the V phase, and the W phase. In either case, the phase of the field magnetic flux φr coincides with the phase determined by the DC excitation of the W phase, so it is easy to obtain the first state.

Of course, it is not necessary to match any one of the U-phase, V-phase, and W-phase as the phase of the modified magnetic field H2. Therefore, it is not necessary to match the phase of the current I3 with any one of the U-phase, V-phase and W-phase. Therefore, the current I3 may be an alternating current and the pretreatment magnetic field H3 may be an alternating magnetic field. In this case, the modified magnetic field H2 is adopted such that the phase of the field magnetic flux φr obtained by the pretreatment magnetic field H3 at the end of the pretreatment is within the range of the region R0 described above.

In this case, it is desirable to set the alternating frequency of the pretreatment magnetic field H3 low so that the motors 1A and 1B rotate.

Next, a technique for obtaining the first state without using the pretreatment magnetic field H3 will be described. For example, if the load 91 is a compressor, the position of the field element 11 depends on the mechanical conditions of the compressor. Taking the case of a piston type compressor as an example, the position at which the piston stops can be mentioned as a mechanical condition of the compressor.

The position of the field element 11 is determined by the position where the piston stops. Therefore, the first state is obtained by determining the position at which the piston stops. The position at which the piston stops can be determined by controlling the pressure difference, which is the difference between the pressure of the refrigerant discharged from the compressor and the pressure of the refrigerant sucked into the compressor. That is, the first state is obtained by controlling the pressure difference described above.

FIG. 16 is a block diagram illustrating the configuration of the refrigerating circuit 9. As shown in FIG. The refrigerating circuit 9 includes a compressor as a load 91, a condenser 92, an expansion valve 93, and an evaporator 94, and refrigerant F circulates through these in this order. The compressor sucks refrigerant F from a suction port 911 , compresses it, and discharges it from a discharge port 912 . Both the condenser 92 and the evaporator 94 can be realized by heat exchangers.

The expansion valve 93 functions as an expansion mechanism that adjusts the extent to which the refrigerant F is expanded. Therefore, by adjusting the degree of opening of the expansion valve 93, the above pressure difference can be controlled, thereby obtaining the first state.

The opening of the expansion valve 93 is adjusted by the control signal K1. The control signal K1 can be generated by techniques commonly used to control the refrigeration circuit 9. FIG. Here, the case where the control signal K1 is generated by the pressure adjustment circuit 5a is exemplified. A case where the pressure adjustment circuit 5a is provided in the motor drive device 10 is exemplified.

The controller 4 causes the pressure regulating circuit 5a to generate the control signal K1 and apply it to the expansion valve 93 in step S1. After that, the control unit 4 causes the AC power supply 2 to flow the current I2 to the armature winding 121 for the magnetization process in step S3.

Condenser 92 and evaporator 94 may control the above pressure difference. This is because the degree to which the refrigerant F condenses or evaporates affects the above-described pressure difference.

FIG. 17 is a block diagram showing the internal configuration of the condenser 92 together with its surroundings. Condenser 92 has heat exchanger 921 and fan 922 . Fan 922 has its air volume adjusted by control signal K2. The control signal K2 can be generated by techniques commonly used to control the refrigeration circuit 9. FIG. Here, the control signal K2 is generated by the pressure regulation circuit 5b. A case where the pressure adjustment circuit 5b is provided in the motor drive device 10 is exemplified.

The controller 4 causes the pressure regulating circuit 5b to generate the control signal K2 and supply it to the fan 922 in step S1. After that, the control unit 4 causes the AC power supply 2 to flow the current I2 to the armature winding 121 for the magnetization process in step S3.

The pressure differential mentioned above may be controlled by the compressor itself. That is, any one of the evaporator 94, the condenser 92, the expansion valve 93, and the compressor controls the pressure difference, thereby obtaining the first state. Thus, the first state is obtained without the current I3.

The control unit 4 includes, for example, a microcomputer and a storage device. The microcomputer executes each processing step (in other words, procedure) described in the program. The storage device can be composed of one or more of various storage devices such as ROM (Read Only Memory), RAM (Random Access Memory), and rewritable nonvolatile memory (EPROM (Erasable Programmable ROM), etc.). . The storage device stores various information and data, stores programs executed by the microcomputer, and provides a work area for executing the programs. The microcomputer can also be understood to function as various means corresponding to each processing step described in the program, or to realize various functions corresponding to each processing step. Moreover, the control unit 4 is not limited to this, and various procedures executed by the control unit 4, various means to be realized, or a part or all of various functions may be realized by hardware.

FIG. 18 is a graph showing magnetization curves of the permanent magnets 111 and 112. FIG. The magnetic field H is plotted on the horizontal axis, and the magnetic flux density B is plotted on the vertical axis. Curves L11 and L12 are magnetization curves of the permanent magnets 111 and 112, and curves L11 and L12 are magnetization curves of the permanent magnets 111 and 112, respectively.

A curve L11 indicates the magnetization curve after the magnetization process, and a curve L12 indicates the magnetization curve after the demagnetization process. The residual magnetic flux densities Br1 of the permanent magnet 111 are shown as residual magnetic flux densities Br1M and Br1m (<Br1) corresponding to the curves L11 and L12, respectively. The residual magnetic flux density Br2 of the permanent magnet 112 is also shown.

Note that the permanent magnet 112 is not essential in this embodiment. This is because the irreversible increase in the residual magnetic flux density Br does not presuppose the presence of the permanent magnet 112 having a residual magnetic flux density Br2 that does not irreversibly increase.

As described above, the motor drive device 10 is a device that drives the motors 1A and 1B. Motors 1A and 1B have a field element 11 and an armature 12 . The field element 11 has permanent magnets 111 and 112 . The permanent magnets 111 and 112 collectively have a residual magnetic flux density Br.

The armature 12 has armature windings 121 . An alternating current I1 flows through the armature winding 121 to generate an alternating magnetic field. A current I2 flows to generate a modified magnetic field H2. The armature 12 rotates relative to the field element 11 by the alternating magnetic field. The changing magnetic field H2 is a magnetic field that irreversibly changes the residual magnetic flux density Br.

The motor drive device 10 includes an AC power supply 2 and a control section 4 . The AC power supply 2 supplies currents I1 and I2 to the armature winding 121 . The control unit 4 causes the AC power supply 2 to supply the current I2 to the armature winding 121 in the first state, and then supplies the current I1 to the armature winding 121 .

In this manner, there is no need to determine whether the position of the field element 11 is within a predetermined range, and the irreversible increase in the residual magnetic flux density Br of the permanent magnets 111 and 112 is facilitated. Furthermore, an irreversible decrease in the residual magnetic flux density Br is prevented.

The first state may be achieved by a pretreatment magnetic field H3 generated by current I3. For example, the control unit 4 applies current I3 to the AC power supply 2 during a period (corresponding to time 0 to t1 in FIGS. 11 and 12) and current I2 (corresponding to time t2 to t3 in FIGS. 11 and 12). ), a non-energized period of a predetermined period (corresponding to times t1 to t2 in FIGS. 11 and 12) is provided. Such a non-energization period is desirable from the viewpoint of suppressing heat generation of the AC power supply 2 and the motor 1 .

Alternatively, the control unit 4 may cause the AC power supply 2 to flow the current I2 immediately after the current I3 is flowed (time t2). Such continuous supply of the currents I3 and I2 is desirable from the viewpoint that it is not necessary to consider the rotation of the motor 1 due to inertia after preprocessing. Even when it is used for driving a compressor, the rotation of the motor 1 due to the pressure difference between the pressure of the refrigerant F at the discharge port 912 and the pressure of the refrigerant F at the suction port 911 of the compressor is taken into consideration. It is also desirable from the point of view that it can be omitted. Of course, as shown in FIGS. 14 and 15, after the current I2 is supplied, the current I3 may be supplied again from time t3.

The motor 1 may be employed to drive a compressor that is provided in the refrigeration circuit 9 and compresses the refrigerant F. The refrigerating circuit 9 includes an evaporator 94 through which a refrigerant F circulates, a condenser 92 and an expansion valve 93 . The first state may be obtained by controlling the aforementioned pressure differential by any one of evaporator 94, condenser 92, expansion valve 93, and compressor. Thus, the first state is obtained without the current I3.

Although the embodiments have been described above, it will be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the claims. The various embodiments and variants described above can be combined with each other.

Reference Signs List 1, 1A, 1B Motor 2 AC power supply 4 Control unit 9 Refrigeration circuit 11A, 11B Field magnet 12 Armature 94 Evaporator 92 Condenser 111, 112 Permanent magnet 121 Armature winding Br Residual magnetic flux density F Refrigerant H2 Altered magnetic field H2M Magnetic field vector I1, I2, I3 Current φr Field magnetic flux

Claims (6)

field elements (11A, 11B) having permanent magnets (111, 112) having residual magnetic flux density (Br) and generating field magnetic flux (φr);
An armature winding through which a first alternating current (I1) flows to generate an alternating magnetic field, and a second current (I2) flows to generate a changing magnetic field, which is a magnetic field that irreversibly changes the residual magnetic flux density. (121) for driving a motor (1A, 1B) having an armature (12) rotated relative to the field element by the alternating magnetic field,
an AC power supply (2) that supplies the first current and the second current to the armature winding;
A first state in which a phase difference between a magnetic flux vector representing the field magnetic flux (φr) and a magnetic field vector representing the modified magnetic field is within a range in which the residual magnetic flux density is irreversibly increased by the modified magnetic field with respect to the AC power supply. a control unit (4) for supplying the second current to the armature winding and then supplying the first current to the armature winding ;
The control unit (4) controls the AC power supply (2) for a predetermined period (t3 A motor driving device (10) which provides a no-energization period from t4) and causes the first current (I1) to flow after the first time . The control unit (4) supplies the AC power supply (2) with a period (0 to t1) during which the third current (I3) for obtaining the first state is supplied and the second current (I2) is supplied. 2. The motor driving device (10) according to claim 1, wherein a non-energized period of another predetermined period (t1 to t2) is provided between the period (t2 to t3). field elements (11A, 11B) having permanent magnets (111, 112) having residual magnetic flux density (Br) and generating field magnetic flux (φr);
An armature winding through which a first alternating current (I1) flows to generate an alternating magnetic field, and a second current (I2) flows to generate a changing magnetic field, which is a magnetic field that irreversibly changes the residual magnetic flux density. an armature (12) having (121) and rotated relative to said field element by said alternating magnetic field;
A device for driving a motor (1A, 1B) having
an AC power supply (2) that supplies the first current and the second current to the armature winding;
A first state in which a phase difference between a magnetic flux vector representing the field magnetic flux (φr) and a magnetic field vector representing the modified magnetic field is within a range in which the residual magnetic flux density is irreversibly increased by the modified magnetic field with respect to the AC power supply. a control unit (4) for supplying the second current to the armature winding and then supplying the first current to the armature winding; and
with
The control unit (4) causes the AC power supply (2) to flow the second current (I2) immediately after flowing the third current ( I3 ) for obtaining the first state. a motor drive (10). field elements (11A, 11B) having permanent magnets (111, 112) having residual magnetic flux density (Br) and generating field magnetic flux (φr);
An armature winding through which a first alternating current (I1) flows to generate an alternating magnetic field, and a second current (I2) flows to generate a changing magnetic field, which is a magnetic field that irreversibly changes the residual magnetic flux density. an armature (12) having (121) and rotated relative to said field element by said alternating magnetic field;
A device for driving a motor (1A, 1B) having
an AC power supply (2) that supplies the first current and the second current to the armature winding;
A first state in which a phase difference between a magnetic flux vector representing the field magnetic flux (φr) and a magnetic field vector representing the modified magnetic field is within a range in which the residual magnetic flux density is irreversibly increased by the modified magnetic field with respect to the AC power supply. a control unit (4) for supplying the second current to the armature winding and then supplying the first current to the armature winding; and
with
The motors (1A, 1B) are provided in the refrigeration circuit (9) and employed to drive a compressor that compresses the refrigerant (F),
The refrigeration circuit includes an evaporator (94) through which the refrigerant circulates, a condenser (92), and an expansion mechanism (93),
difference between the pressure of the refrigerant discharged from the compressor and the pressure of the refrigerant sucked into the compressor by any one of the evaporator, the condenser, the expansion mechanism, and the compressor; A motor drive (10) wherein said first state is obtained by controlling a pressure differential of . field elements (11A, 11B) having permanent magnets (111, 112) having residual magnetic flux density (Br) and generating field magnetic flux (φr);
An armature winding through which a first alternating current (I1) flows to generate an alternating magnetic field, and a second current (I2) flows to generate a changing magnetic field, which is a magnetic field that irreversibly changes the residual magnetic flux density. an armature (12) having (121) and rotated relative to said field element by said alternating magnetic field;
A device for driving a motor (1A, 1B) having
an AC power supply (2) that supplies the first current and the second current to the armature winding;
A first state in which a phase difference between a magnetic flux vector representing the field magnetic flux (φr) and a magnetic field vector representing the modified magnetic field is within a range in which the residual magnetic flux density is irreversibly increased by the modified magnetic field with respect to the AC power supply. a control unit (4) for supplying the second current to the armature winding and then supplying the first current to the armature winding; and
with
The control unit (4) supplies the AC power supply (2) with the third current (I3) for obtaining the first state during the period (t2 to t3) in which the second current (I2) is supplied. A motor driving device (10) provided during a period (0 to t4) and causing said first current (I1) to flow immediately after said third current (I3) is passed. The motor drive device (10) according to claim 3 or 5, wherein the motors (1A, 1B) are provided in a refrigeration circuit (9) and employed to drive a compressor that compresses a refrigerant (F). .

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