JP2012223021A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device capable of reducing a magnetizing current for changing a magnetic force of a variable magnetic force magnet.SOLUTION: A variable magnetic force memory motor drive device 1 has a variable magnetic force memory motor 2 having a variable magnetic force magnet 41 whose magnetization characteristics Fimag vary. The magnetization characteristics Fimag of the variable magnetic force magnet 41 are specified. A magnetic flux target value φ* after magnetization is determined on the basis of a rotation number Nr of the variable magnetic force memory motor 2. An inverter 4 is controlled so as to apply a magnetizing current Id to the variable magnetic force magnet 41 on the basis of the magnetization characteristics Fimag and the magnetic flux target value φ*.

Description

  The present invention relates to a motor drive device that drives a motor using a variable magnetic force magnet that can change a magnetic force.

  2. Description of the Related Art In recent years, a motor drive device using a variable magnetic memory motor, which is expected to be highly efficient or output in a high speed region, has been proposed as a drive device for next-generation railways and electric vehicles. The rotor (rotor) of the variable magnetic force memory motor is embedded with a variable magnetic force magnet that can change the magnetic force by being magnetized. The magnetic force of the variable magnetic magnet is controlled by a magnetizing current output from an inverter that drives the motor. The motor drive device increases the magnetic force of the variable magnetic magnet in the low speed region, and decreases the magnetic force of the variable magnetic magnet in the high speed region. As a result, the variable magnetic force memory motor can be expected to improve the output in a high efficiency and high speed range.

Japanese Patent Application Laid-Open No. 07-336980 JP-A-08-009610 JP-A-2005-304204 US Pat. No. 6,800,077

  However, it is necessary to apply an excessive magnetization current in a short time for the magnetization of the variable magnetic force magnet. In order to flow an excessive magnetizing current, a high inverter output voltage corresponding to the excessive magnetizing current is required. If the inverter output voltage necessary for the magnetizing current cannot be secured, the magnetic force of the variable magnetic magnet cannot be changed. In such a case, the motor efficiency is lowered and the necessary torque cannot be secured.

  Accordingly, an object of an embodiment of the present invention is to provide a motor drive device capable of reducing a magnetizing current for changing the magnetic force of a variable magnetic magnet.

  A motor drive device according to an aspect of the present invention includes a synchronous motor including a variable magnetic magnet that is magnetized to change a magnetic force and change a magnetic characteristic, and a magnetization characteristic specifying unit that specifies the magnetization characteristic of the variable magnetic magnet And a magnetic flux target value determining means for determining a magnetic flux target value that is a target value of the magnetic flux of the variable magnetic magnet after magnetization based on the rotational speed of the synchronous motor, and the magnetization specified by the magnetization characteristic specifying means Based on the magnetic flux target value determined by the characteristics and the magnetic flux target value determining means, the magnetizing current determining means for determining the magnetizing current to flow to magnetize the variable magnetic force magnet, and the magnetizing current determining means Magnetizing current output means for outputting the magnetizing current to the synchronous motor.

The block diagram which shows the structure of the variable magnetic force memory motor drive device which concerns on embodiment of this invention. Sectional drawing which shows the structure of the rotor of the variable magnetic force memory motor which concerns on this embodiment. The characteristic view which shows the characteristic (BH characteristic) showing the correlation of the magnetic flux density B of the magnet used for the rotor which concerns on this embodiment, and the magnetic field H. FIG. The characteristic view which shows the correlation of the magnetic flux amount of the variable magnetic magnet which concerns on this embodiment, and a magnetization current. The block diagram which shows the structure of the magnetization management part which concerns on this embodiment. The graph which shows the correlation of the rotation speed and magnetic flux target value for determining the magnetic flux target value in the magnetic flux target value setting part which concerns on this embodiment. The graph which shows transition of the magnetization mode in the magnetization process which concerns on this embodiment. The graph figure which shows the change of the DQ-axis current command which concerns on this embodiment. The graph which shows the change of the various magnetic flux amount which concerns on this embodiment. The block diagram which shows the structure of the magnetic flux management part which concerns on this embodiment. The block diagram which shows the structure of the magnetization current instruction | command calculating part which concerns on this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a configuration diagram showing a configuration of a variable magnetic force memory motor drive device 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the rotor 40 of the variable magnetic force memory motor 2 according to the present embodiment. In the drawings, the same parts are denoted by the same reference numerals, detailed description thereof is omitted, and different parts are mainly described. In the following embodiments, the same description is omitted.

  The variable magnetic force memory motor drive device 1 includes a variable magnetic force memory motor 2, a rotor position detector 3, an inverter 4, a DC power source 5, a smoothing capacitor 6, a DC voltage detector 7, a motor current detector 8U, 8W and the control part 9 are provided.

  The variable magnetic force memory motor 2 is a permanent magnet synchronous motor in which a variable magnetic force magnet 41 that is a permanent magnet capable of changing a magnetic force is embedded in a rotor 40. The variable magnetic force magnet 41 is magnetized by the magnetization current Imag (d-axis current Id) input from the inverter 4, thereby changing the magnetic force. As a result, the magnetic flux of the variable magnetic force memory motor 2 changes. The variable magnetic force memory motor 2 is driven by AC power supplied from the inverter 4.

  The rotor position detector 3 detects a rotor phase θm indicating the rotational position of the rotor (rotor) 40 of the variable magnetic force memory motor 2. The rotor position detector 3 is a resolver, for example.

  The inverter 4 converts the DC power supplied from the DC power source 5 into three-phase AC power. The inverter 4 supplies the converted AC power to the variable magnetic force memory motor 2. The inverter 4 controls the variable magnetic force memory motor 2 by outputting AC power to the variable magnetic force memory motor 2.

  The DC power source 5 is connected to the DC side (input side) of the inverter 4. The DC power source 5 supplies DC power to the inverter 4.

  The smoothing capacitor 6 is connected to the DC side of the inverter 4. Smoothing capacitor 6 smoothes DC voltage Vdc input to inverter 4.

  The DC voltage detector 7 detects an inverter DC input voltage Vdc that is a voltage on the DC side of the inverter 4. The DC voltage detector 7 outputs the detected inverter DC input voltage Vdc to the control unit 9.

  The AC current detectors 8U and 8W detect motor currents Iu and Iw flowing from the inverter 4 to the variable magnetic force memory motor 2. AC current detector 8U detects motor U-phase current Iu. AC current detector 8W detects motor W phase current Iw. The AC current detectors 8U and 8W output the detected motor currents Iu and Iw to the control unit 9.

  The controller 9 detects the rotor phase θm detected by the rotor position detector 3, the inverter DC input voltage Vdc detected by the DC voltage detector 7, and the motor currents Iu and Iw detected by the AC current detectors 8U and 8W. Based on the above, the inverter 4 is controlled. The control unit 9 controls the variable magnetic force memory motor 2 by controlling the motor currents Iu and Iw output from the inverter 4.

  The structure of the rotor 40 will be described with reference to FIG. The arrows in FIG. 2 indicate the directions of the magnetic lines of force of the magnets 41, 42, and 43.

  The rotor 40 has a structure in which magnets 41, 42, and 43 are embedded in a rotor core 44. The rotor 40 includes eight magnetic pole portions 45 and eight iron magnetic pole portions 46 that generate reluctance torque. The rotor 40 rotates about the rotation shaft 51. The bearing 52 supports the rotating shaft 51. The magnetic pole portion 45 of one magnet includes one variable magnetic magnet 41, one fixed magnetic magnet 42, and two fixed magnetic magnets 43.

  The variable magnetic magnet 41 is a magnet that changes the magnetic force. Accordingly, the variable magnetic force magnet 41 is a magnet made of a material having a low coercive force. On the other hand, the fixed magnetic magnets 42 and 43 are magnets that are used while the magnetic force is substantially fixed. Accordingly, the fixed magnetic magnet 42 is a magnet made of a material having a high coercive force. The fixed magnetic magnet 42 is arranged in series with the variable magnetic magnet 41. The fixed magnetic magnet 42 is provided to supplement the magnetic force of the variable magnetic magnet.

  FIG. 3 is a characteristic diagram showing a characteristic (BH characteristic) representing a correlation between the magnetic flux density B and the magnetic field H of the magnets 41 to 43 used in the rotor 40 according to the present embodiment. A curve Cc shows the BH characteristic of the variable magnetic magnet 41. A curve Cv shows the BH characteristics of the fixed magnetic magnets 42 and 43.

  The BH characteristic of the variable magnetic magnet 41 is such that the change width Sc of the magnetic field H necessary for changing the magnetic flux density B from the upper limit to the lower limit is narrower than the width Si of the magnetic field H that changes with the magnetizing current Imag flowing from the inverter 4. The variable magnetic magnet 41 is made of a material having a low coercive force. Thereby, the variable magnetic force magnet 41 can be changed to an arbitrary magnetic flux density B by the magnetic field H generated by the magnetization current Imag flowing from the inverter 4.

  On the other hand, the BH characteristics of the fixed magnetic magnets 42 and 43 are larger than the width Si of the magnetic field H in which the change width of the magnetic field H necessary for changing the magnetic flux density B from the upper limit to the lower limit is changed by the magnetization current Imag flowing from the inverter 4. Very wide. The fixed magnetic magnets 42 and 43 are made of a material having a high coercive force as described above. Thus, the fixed magnetic magnets 42 and 43 can be hardly affected by the magnetization current Imag and hardly change the magnetic flux density B by the magnetic field H generated by the magnetization current Imag flowing from the inverter 4.

  FIG. 4 is a characteristic diagram showing the correlation between the amount of magnetic flux and the magnetizing current of the variable magnetic force magnet 41 according to the present embodiment.

  With reference to FIG. 4, the magnetization of the variable magnetic force magnet 41 will be described.

  When the maximum magnetizing current I5 is passed through the variable magnetic force magnet 41, the magnetic flux value of the variable magnetic force magnet 41 becomes the maximum magnetic flux value φ1. When the demagnetizing current I6 is supplied in this state, the magnetic flux value of the variable magnetic force magnet 41 is demagnetized to a magnetic flux value φ2 smaller than the maximum magnetic flux value φ1. When the magnetizing current I1 is supplied in this state, the magnetic flux value of the variable magnetic magnet 41 becomes the maximum magnetic flux value φ1 through the magnetizing path (magnetization characteristic) P1 at the position where the magnetic flux amount is maximum. In this state, when the maximum demagnetizing current I10 is passed, the magnetic flux value of the variable magnetic magnet 41 becomes the minimum magnetic flux value φ6. However, the variable magnetic force magnet 41 is not magnetized even when the magnetizing current I1 that has been magnetized in the previous state is supplied in the state of the minimum magnetic flux value φ6. Magnetization in this case is because the variable magnetic force magnet 41 is magnetized through the path P5 at the position where the amount of magnetic flux is minimized. Therefore, in the state after the minimum magnetic flux value φ6 is reached in this way, the magnetic flux value of the variable magnetic force magnet 41 becomes the maximum magnetic flux value φ1 by flowing the maximum magnetizing current I5.

  Here, it has been described that when the magnetic flux value of the variable magnetic force magnet 41 is increased after being demagnetized to the magnetic flux values φ2 and φ6, respectively, it passes through the paths P1 and P5, but is between the paths P1 and P5. The same applies to the case of passing through intermediate paths P2 to P4. That is, first, in order to demagnetize the magnetic flux value φ of the variable magnetic magnet 41 to the magnetic flux values φ3 to φ5, it is necessary to pass demagnetizing currents I7 to I9, respectively. Next, when demagnetizing the magnetic flux value of the variable magnetic force magnet 41 to the magnetic flux value φ3 to φ5 and then increasing the magnetic flux value to the maximum magnetic flux value φ1, it is necessary to pass the magnetizing currents I2 to I4, respectively. In this way, when flowing the magnetizing currents I2 to I4, the variable magnetic force magnet 41 is magnetized so as to pass through the paths P2 to P4, respectively.

  Therefore, in order to magnetize the variable magnetic magnet 41 so as to be the magnetic flux target value φ *, the control unit 9 needs to grasp which path (magnetization characteristic) P1 to P5 is used for magnetizing. Therefore, the magnetic flux management unit 21 of the control unit 9 manages the minimum magnetic flux value φmin that is an element for specifying such magnetization characteristics.

  The control unit 9 includes a magnetic flux management unit 21, a normal current command calculation unit 22, a command selection unit 23, coordinate conversion units 24 and 26, a current control unit 25, a PWM circuit 27, and a rotation speed calculation unit 28. A magnetization management unit 29, a magnetization current command calculation unit 30, and subtractors 33d and 33q.

  Here, the DQ axis coordinates will be described. The D axis on the DQ axis is an axis in the magnet magnetic flux direction and is an axis that does not act on the magnetic torque. The Q axis on the DQ axis is an axis orthogonal to the magnet magnetic flux direction (axis orthogonal to the D axis) and is an axis that acts on the magnetic torque.

  First, the configuration of the control unit 9 at normal time (when not magnetized) will be described.

  The magnetic flux management unit 21 performs arithmetic processing or management related to various magnetic fluxes based on the magnetic flux target value φ * and the magnetization mode MD input from the magnetization management unit 29. Specifically, the magnetic flux management unit 21 manages the magnetic flux target value φ *, the current magnetic flux value φn, and the minimum magnetic flux value φmin. Here, the current magnetic flux value φn is the current magnetic flux value of the variable magnetic magnet 41 managed by the magnetic flux management unit 21. The magnetic flux management unit 21 stores the minimum magnetic flux value at which the current magnetic flux value φn has decreased during operation as the minimum magnetic flux value φmin. The magnetic flux management unit 21 outputs the managed current magnetic flux value φn to the normal current command calculation unit 22 and the magnetization current command calculation unit 30. The magnetic flux management unit 21 outputs the managed magnetic flux target value φ * and the minimum magnetic flux value φmin to the magnetizing current command calculation unit 30.

  The normal current command calculation unit 22 receives the torque command Trq * and the current magnetic flux value φn managed by the magnetic flux management unit 21. The normal current command calculation unit 22 calculates a normal D-axis current command Id1 * and a normal Q-axis current command Iq1 * based on the torque command Trq * and the current magnetic flux value φn. The normal-time current command calculation unit 22 outputs the calculated normal DQ-axis current commands Id1 * and Iq1 * to the command selection unit 23. The normal-time current command calculation unit 22 outputs the calculated normal D-axis current command Id1 * to the magnetization current command calculation unit 31 of the magnetization-time current command calculation unit 30.

  The normal D-axis current command Id1 * is a command for controlling the D-axis current (magnetization current) Id that flows to the variable magnetic force memory motor 2 during normal operation. The normal Q-axis current command Iq1 * is a command for controlling the Q-axis current (torque current) Iq that flows to the variable magnetic force memory motor 2 during normal operation. That is, the Q-axis current command Iq1 * is a command for controlling the torque of the variable magnetic force memory motor 2.

  The command selection unit 23 switches the current commands Id * and Iq * between normal time and magnetization based on the magnetization mode MD output from the magnetization management unit 29. The magnetization mode MD is “0” during normal time, and “1” or “2” during magnetization. If the magnetization mode MD is “0”, the command selection unit 23 selects the normal DQ axis current commands Id1 * and Iq1 * as the current commands Id * and Iq *, and the magnetization mode MD is “non-zero”. If there is, the DQ axis current commands Id2 * and Iq2 * during magnetization are selected as the current commands Id * and Iq *. Here, since it is normal time, the command selection unit 23 selects the normal DQ axis current commands Id1 * and Iq1 *. The command selection unit 23 outputs the selected current commands Id * and Iq * to the subtracters 33d and 33q.

  The coordinate conversion unit 24 converts the motor currents Iu and Iw, which are phase currents detected by the AC current detectors 8U and 8W, into the DQ axis coordinate system DQ based on the rotor phase θm detected by the rotor position detector 3. Conversion to shaft currents Id and Iq. Note that the V-phase current not directly detected is calculated from the other two phase currents Iu and Iw. The coordinate conversion unit 24 outputs the calculated DQ axis currents Id and Iq to the subtracters 33d and 33q.

  The D-axis current command Id * output from the command selection unit 23 and the D-axis current Id calculated by the coordinate conversion unit 24 are input to the subtractor 33d. The subtractor 33d subtracts the D-axis current Id from the D-axis current command Id *. The subtractor 33 d outputs the difference ΔId of the subtracted D-axis current to the current control unit 25.

  The Q-axis current command Iq * output from the command selection unit 23 and the Q-axis current Iq calculated by the coordinate conversion unit 24 are input to the subtractor 33q. The subtractor 33q subtracts the Q-axis current Iq from the Q-axis current command Iq *. The subtractor 33q outputs the subtracted Q-axis current difference ΔIq to the current controller 25.

  The current control unit 25 uses the DQ axis voltage command Vd so that the difference ΔId, ΔIq of the DQ axis current calculated by the subtractors 33d, 33q is zero by a PI (proportional-plus-integral control) controller or the like. * And Vq * are calculated. The DQ axis voltage commands Vd * and Vq * are voltage commands in the DQ axis coordinate system for controlling the output voltage of the inverter 4. The current control unit 25 outputs the calculated DQ axis voltage commands Vd * and Vq * to the coordinate conversion unit 26.

  The coordinate conversion unit 26 uses the DQ axis voltage commands Vd * and Vq * calculated by the current control unit 25 based on the rotor phase θm detected by the rotor position detector 3 and voltage commands for each phase of the three-phase AC. Convert to Vu *, Vv *, Vw *. The three-phase AC voltage commands Vu *, Vv *, and Vw * are voltage commands for each phase of the three-phase AC for controlling the output voltage of the inverter 4. The coordinate conversion unit 26 outputs the calculated three-phase AC voltage commands Vu *, Vv *, Vw * to the PWM circuit 27.

  The PWM circuit 27 generates a gate signal GS for PWM (Pulse Width Modulation) control of the inverter 4 based on the three-phase AC voltage commands Vu *, Vv *, Vw * calculated by the coordinate conversion unit 26. For example, the PWM circuit 27 generates the gate signal GS by triangular wave comparison PWM or synchronous PWM. The PWM circuit 27 outputs the generated gate signal GS to the gate circuit of the inverter 4. Thereby, a three-phase AC voltage is output from the inverter 4 in accordance with the three-phase AC voltage commands Vu *, Vv *, Vw *. Thereby, the control unit 9 controls the driving of the variable magnetic force memory motor 2.

  Next, the configuration of the control unit 9 during magnetization will be described.

  The rotation speed calculation unit 28 calculates the rotation speed Nr [rpm] of the rotor 40 based on the rotor phase θm detected by the rotor position detector 3. The rotation number calculation unit 28 outputs the calculated rotation number Nr to the magnetization management unit 29.

  The magnetization management unit 29 includes a torque command Trq *, an inverter DC input voltage Vdc detected by the DC voltage detector 7, and a variable magnetic force magnet 41 determined by the magnetization current command calculation unit 31 of the magnetizing current command calculation unit 30. The magnetization characteristic Fimag at the time of magnetization and the rotation speed Nr calculated by the rotation speed calculator 28 are input.

  Here, the magnetization characteristic Fimg is a function indicating which of the path P1 to the path P5 shown in FIG. This function is determined by the minimum magnetic flux value φmin. Moreover, the magnetization characteristic Fimg at the time of magnetization is the magnetization characteristic Fimg that can be grasped when the magnetization process of the variable magnetic force magnet 41 is executed (at the time of calculating the D-axis current command (magnetization current command) Id2 * at the time of magnetization). is there.

  In the magnetizing current command calculation unit 31, in order to calculate the magnetizing current command (D-axis current command) Id2 *, it is necessary to determine the magnetization characteristic Fimag when the variable magnetic magnet 41 is magnetized, as described above. Therefore, the magnetization current command calculation unit 31 determines the magnetization characteristic Fimag based on the minimum magnetic flux value φmin managed by the magnetic flux management unit 21.

  The magnetization management unit 29 manages control for executing the magnetization of the variable magnetic force magnet 41. Specifically, it is determined whether or not to execute the magnetization process of the variable magnetic force magnet 41 based on the rotational speed Nr, the torque, the inverter DC input voltage Vdc, the magnetization characteristic Fimag during magnetization, or the like. When the magnetization management unit 29 determines to execute the magnetization process, the magnetization management unit 29 determines a magnetic flux target value φ * that is a target of the magnetic flux after magnetization of the variable magnetic force magnet 41. The magnetization management unit 29 generates a magnetization mode MD that represents the process of the magnetization process in order to execute the magnetization process. The magnetization management unit 29 outputs the magnetic flux target value φ * and the magnetization mode MD to the magnetic flux management unit 21. The magnetization management unit 29 controls the command selection unit 23 to switch the current command values Id * and Iq * from the normal DQ axis current commands Id1 * and Iq1 * to the DQ axis current commands Id2 * and Iq2 * during magnetization. The magnetization mode MD is output.

  FIG. 5 is a configuration diagram showing the configuration of the magnetization management unit 29 according to the present embodiment.

  The magnetization management unit 29 includes a magnetic flux target value setting unit 51, a previous value storage unit 52, a comparator 53, a selector 54, an OR circuit 55, a magnetic flux target value recording unit 56, and a magnetization mode sequence processing unit 57. And a magnetic flux reset processing unit 58.

  The magnetic flux target value setting unit 51 sets a magnetic flux target value φ0 *, which is a basic value of the magnetic flux target value φ *, based on the rotation speed Nr, the magnetization characteristic Fimag, and the inverter DC input voltage Vdc. The magnetic flux target value setting unit 51 sets the magnetic flux target value φ0 * so that the operation efficiency and output of the variable magnetic force memory motor 2 are superior. The magnetic flux target value setting unit 51 outputs the set magnetic flux target value φ0 * to the previous value storage unit 52, the comparator 53, and the selector 54.

  A method for setting the magnetic flux target value φ0 * will be described with reference to FIG. FIG. 6 is a graph showing the correlation between the rotational speed Nr for determining the magnetic flux target value φ0 * and the magnetic flux target value φ0 *.

  FIG. 6 shows an example in which the magnetic flux target value φ0 * is switched in three stages according to the rotation speed Nr. The magnetic flux target value setting unit 51 sets a magnetic flux target value φ * as the magnetic flux value φa in the low rotation range, the magnetic flux value φb in the middle rotation range, and the magnetic flux value φc in the high rotation range. Here, the magnetic flux values φa, φb, and φc have a relationship of φa> φb> φc. Therefore, the magnetic flux target value setting unit 51 sets the magnetic flux target value φ0 * that is smaller as the rotational speed is higher. The higher the rotation speed, the larger the back electromotive force due to the magnet magnetic flux, the copper loss due to the flow of the field weakening current may increase, and the iron loss occurs. For this reason, as shown in FIG. 6, at high rotation, the magnetic flux of the variable magnetic magnet 41 is reduced in terms of efficiency and output.

  When the magnetic force is changed (that is, magnetized), the output voltage of the inverter 4 needs to be higher than that in the normal operation in order to flow the magnetizing current Imag into the variable magnetic force memory motor 2. Further, the output voltage of the inverter 4 at the time of magnetization may be smaller in the case of demagnetization than in the case of magnetization. This is because when the demagnetization is performed, the negative D-axis current Id is caused to flow as the magnetization current Imag, so that the magnetic flux of the variable magnetic magnet 41 is canceled.

  Thus, from the difference in demand for the output voltage of the inverter 4 when magnetizing and demagnetizing, as shown in FIG. Has hysteresis characteristics. For example, when assuming application to an electric vehicle (EV), the variable magnetic force memory motor drive device 1 is designed so that the rotational speeds N4 and N6 to be demagnetized are as follows. The rotational speed N4 that demagnetizes from the magnetic flux value φa to the magnetic flux value φb is set to a rotational speed that is greater than or equal to traveling in the city. Further, the rotational speed N6 that demagnetizes from φb to φc is set to a rotational speed that is equal to or higher than normal high-speed traveling. Thereby, the operating efficiency of the variable magnetic force memory motor drive device 1 can be improved. In the variable magnetic memory motor drive device 1 designed in this way, it is difficult to increase the magnetism once demagnetized, and it is considered that the higher the magnetic flux value, the better the operation efficiency. .

  As described above, the magnetization characteristic Fimg of the variable magnetic force magnet 41 varies depending on the history of magnetization. Therefore, the magnetic flux target value setting unit 51 determines at which rotation speed Nr the magnetization can be increased according to the magnetization characteristic Fimag during magnetization. That is, in FIG. 6, the magnetic flux target values φa, φb, and φc do not depend on the magnetization characteristics Fimag at the time of magnetization, but the rotation speeds N1 and N2 to be increased are the magnetization characteristics Fimag at the time of magnetization, the inverter DC input voltage Vdc, And is determined according to the rotational speed Nr.

  Here, consider the case where the magnetic flux is increased to the magnetic flux target value φa. Based on the magnetization characteristic Fimg at the time of magnetization, the magnetization current Imag for increasing the magnetic flux to the magnetic flux target value φ * can be calculated from the inverse function of the function indicated by the magnetization characteristic Fimag. Here, if the electrical angular frequency corresponding to the rotational speed Nr is ω, the required voltage V1 * on the DQ axis can be determined as the output voltage of the inverter 4 as in the following equation.

Vd * = R × Id * −ω × Lq × Iq * + d / dt (Ld × Id *)
Vq * = R × Iq * + ω × Ld × Id * + ω × φ * + d / dt (Lq × Iq *)
V1 * = √ (Vd * × Vd * + Vq * × Vq *)
Here, “Vd *” is a D-axis voltage command, “Vq *” is a Q-axis voltage command, “Id *” is a D-axis current command, “Iq *” is a Q-axis current command, “R” is a resistance, “Ld” indicates D-axis inductance, and “Lq” indicates Q-axis inductance.

  On the other hand, the maximum output voltage of the inverter 4 on the DQ axis in the one-pulse mode can be expressed by the following equation using the inverter DC input voltage Vdc.

Vmax = √6 / π × Vdc
Here, a coefficient K (0 <K <1) for considering a voltage margin and a parameter error for securing the current control capability is set. The maximum output voltage V1 * max on the DQ axis is determined as follows using the coefficient K.

V1 * max = K × Vmax
Therefore, it is possible to determine the electrical angular frequency ω (that is, the rotation speed Nr) for increasing the magnetization on condition that V1 * max> V1 * is satisfied. Also, the characteristics for demagnetization can be calculated in the same manner.

  The previous value storage unit 52 is input with the magnetic flux target value φ0 * set by the magnetic flux target value setting unit 51. The previous value storage unit 52 stores a magnetic flux target value φ0 * obtained when the previous magnetization process was performed. Therefore, the previous value storage unit 52 stores the latest magnetic flux target value φ0 * when the magnetization process starts (or ends). The previous value storage unit 52 outputs the stored previous magnetic flux target value φ0 * to the comparator 53.

  The latest magnetic flux target value φ0 * set by the magnetic flux target value setting unit 51 and the previous magnetic flux target value φ0 * stored in the previous value storage unit 52 are input to the comparator 53. The comparator 53 outputs “1” to the selector 54 and the OR circuit 55 when the latest magnetic flux target value φ0 * is different from the previous magnetic flux target value φ0 *. That is, the comparator 53 outputs “1” when the magnetic flux target value φ0 * changes. The comparator 53 outputs “0” when the magnetic flux target value φ0 * has not changed.

  When the OR circuit 55 receives “1” from the magnetic flux reset processing unit 58 or the comparator 53, the OR circuit 55 outputs “1” to the magnetic flux target value recording unit 56 and the magnetization mode sequence processing unit 57. That is, the OR circuit 55 calculates a logical sum of signals input from the magnetic flux reset processing unit 58 and the comparator 53, respectively. When the OR circuit 55 outputs “1”, the magnetization request flag Frq indicating the start of the magnetization process becomes “1” (the magnetization request flag Frq is set).

  Upon receiving “1” from the comparator 53, the selector 54 selects the latest magnetic flux target value φ0 * set by the magnetic flux target value setting unit 51. Upon receiving “0” from the comparator 53, the selector 54 selects the maximum magnetic flux value φ1. In the characteristics shown in FIG. 6, the maximum magnetic flux value φ1 is the magnetic flux value φa. The selector 54 outputs the selected magnetic flux value to the magnetic flux target value recording unit 56 as the finally determined magnetic flux target value φ *.

  When “1” is input from the OR circuit 55, the magnetic flux target value storage unit 56 stores the magnetic flux target value φ * input from the selector 54. The magnetic flux target value storage unit 56 outputs the magnetic flux target value φ * to the magnetic flux management unit 21. Accordingly, when “0” is input from the OR circuit 55, the magnetic flux target value storage unit 56 outputs the magnetic flux target value φ * without storing it.

  When the magnetization mode sequence processing unit 57 receives “1” from the OR circuit 55 (the magnetization request flag Frq becomes “1”), the magnetization mode sequence processing unit 57 generates a magnetization mode MD representing the process of the magnetization process for performing the magnetization process. .

  With reference to FIGS. 7-9, the magnetization process which concerns on this embodiment is demonstrated. FIG. 7 is a graph showing the transition of the magnetization mode MD in the magnetization process. FIG. 8 is a graph showing changes in the DQ axis current commands Id * and Iq * in the magnetization process. FIG. 9 is a graph showing changes in the magnetic flux amounts φ *, φr, and φn in the magnetization process. Here, for convenience of explanation, it is assumed that the DQ axis currents Id and Iq that actually flow through the variable magnetic force memory motor 2 have the same changes as the DQ axis current commands Id * and Iq *.

  The magnetization mode MD is any one of “0” indicating the magnetization mode 0, “1” indicating the magnetization mode 1, and “2” indicating the magnetization mode 2. 7 to 9, the magnetization mode 0 is shown until time t1, the magnetization mode 1 is shown from time t1 to time t2, the magnetization mode 2 is shown from time t2 to time t3, and the magnetization mode 0 is shown after time t3.

  The magnetization mode 0 indicates a state where the magnetization process is not started. That is, the variable magnetic force memory motor drive device 1 is in a normal operation state. When the magnetization request flag Frq becomes “1”, the magnetization mode MD shifts from “0” to “1”.

  The magnetization mode 1 is a state in which the D-axis current (magnetization current) command Id * is gradually increased to the target value. In the magnetization mode 1, the variable magnetic force magnet 41 can be increased to the magnetic flux target value φ * by increasing the D-axis current command Id * to the target value. When demagnetizing the variable magnetic force magnet 41, the D-axis current command Id * is gradually reduced to the target value. On the other hand, the Q-axis current (torque current) command Iq * is controlled to a value for eliminating a torque discontinuity during magnetization or ensuring a voltage margin of the inverter output voltage for applying the magnetization current Imag. FIG. 8 shows control for ensuring a voltage margin. When the D-axis current command Id * reaches the target value, the magnetization mode MD shifts from “1” to “2”.

  The magnetization mode 2 is a mode for returning to normal operation. In the magnetization mode 2, the DQ axis current commands Id * and Iq * are asymptotic to the normal current command values Id1 * and Iq1 *, respectively. The normal Q-axis current (torque current) command value Iq * is adjusted to be constant (the torque is not changed) as the variable magnetic magnet 41 is magnetized (or demagnetized) before and after the magnetization process. . When the DQ-axis current commands Id * and Iq * are matched with the current command values Id1 * and Iq1 * at the normal time, the magnetization mode MD shifts from “2” to “0”. Thereby, the magnetization process is completed.

  The rotation speed Nr calculated by the rotation speed calculation section 28 is input to the magnetic flux reset processing section 58. The magnetic flux reset processing unit 58 determines whether or not to perform the magnetic flux reset processing based on various information such as the rotation speed Nr. When it is determined that the magnetic flux reset processing is to be performed, the magnetic flux reset processing unit 58 outputs “1” to the OR circuit 55. Thereby, a magnetic flux reset process is performed. Here, the magnetic flux reset process is a process for making the grasped magnetization characteristic Fimag accurate. Specifically, the control unit 9 causes the maximum magnetization current Imag (magnetization current I5 in FIG. 4) to flow to change the magnetic force of the variable magnetic force magnet 41 to the maximum magnetic flux φ1. In the magnetization process by the magnetic flux reset processing unit 58, the maximum magnetic flux value φ1 selected by the selector 54 becomes the magnetic flux target value φ * when the output of the comparator 53 is “0”.

  The condition for executing the magnetic flux reset process is that there is a high possibility that the accuracy of the magnetization characteristic Fimg grasped by the control unit 9 (or the minimum magnetic flux value φmin managed by the magnetic flux management unit 21) is lowered. This is the case. Specifically, the condition for executing the magnetic flux reset process corresponds to one of the following conditions.

(A) When the rotational speed Nr decreases from a predetermined value (for example, near zero) (b) When the rotational speed Nr increases from a predetermined value (c) When a predetermined time elapses without performing magnetic flux reset processing (d ) When the magnetization process is executed a predetermined number of times without performing the magnetic flux reset process In order to determine whether or not the condition (c) is satisfied, the time during which the magnetic flux reset process is not performed may be measured. Then, the magnetic flux reset process may be executed at predetermined time intervals. In addition to the above, the determination may be made based on the rotor temperature and the magnet temperature.

  FIG. 10 is a configuration diagram illustrating a configuration of the magnetic flux management unit 21 according to the present embodiment.

  The magnetic flux management unit 21 includes a comparator 61, a current magnetic flux value storage unit 62, and a minimum magnetic flux value calculation unit 63.

  The magnetic flux management unit 21 outputs the magnetic flux target value φ * input from the magnetization management unit 29 as it is.

  The current magnetic flux value storage unit 62 is inputted with a magnetic flux target value φ *. The comparator 61 determines whether or not the magnetization mode MD is “2”. When the magnetization mode MD becomes “2”, the comparator 61 outputs “1” to the current magnetic flux value storage unit 62. The current magnetic flux value storage unit 62 is inputted with a magnetic flux target value φ *. When “1” is input from the comparator 61, the current magnetic flux value storage unit 62 stores (updates) the magnetic flux target value φ * input at that time as the current magnetic flux value φn. The time when the magnetization mode MD shifts from “1” to “2” is when the magnetic flux value φr of the variable magnetic magnet 41 reaches the magnetic flux target value φ * as shown in FIG. 9 (time t2). The current magnetic flux value storage unit 62 outputs the stored current magnetic flux value φn.

  The minimum magnetic flux value calculation unit 63 manages the minimum magnetic flux value φmin. The minimum magnetic flux value calculation unit 63 includes a minimum value selection unit 64, a comparator 65, and a selector 66.

  The minimum value selection unit 64 selects the smaller one of the currently output minimum magnetic flux value φmin and the current magnetic flux value φn stored in the current magnetic flux value storage unit 62. The minimum value selector 64 outputs the selected magnetic flux value to the selector 66.

  The comparator 65 compares the current magnetic flux value φn stored in the current magnetic flux value storage unit 62 with the magnetic flux set value φs1. The comparator 65 outputs “1” when the current magnetic flux value φn is larger than the magnetic flux set value φs1. The comparator 65 outputs “0” when the current magnetic flux value φn is equal to or smaller than the magnetic flux set value φs1. Here, the magnetic flux set value φs1 is a magnetic flux value that is slightly smaller than the maximum magnetic flux value φ1, as shown in FIG. For example, the magnetic flux set value φs1 is 95% of the maximum magnetic flux value φ1.

  When “0” is input from the comparator 65, the selector 66 sets either the current minimum magnetic flux value φmin or the current magnetic flux value φn selected by the minimum value selector 64 as the minimum magnetic flux. Output as value φmin. When “1” is input from the comparator 65, the selector 66 outputs the preset maximum magnetic flux value φ1 as the minimum magnetic flux value φmin.

  Here, the reason why the selector 66 outputs the maximum magnetic flux value φ1 when “1” is input from the comparator 65 is to ensure the accuracy of the minimum magnetic flux value φmin. That is, when the current magnetic flux value φn is as close as possible to the maximum magnetic flux value φ1 (the magnetic flux value equal to or higher than the magnetic flux setting value φs1), the minimum magnetic flux value φmin is reliably set to the maximum magnetic flux value φ1.

  The magnetizing current command calculation unit 30 calculates the DQ axis current commands Id2 * and Iq2 * during magnetization. The magnetizing current command calculation unit 30 outputs the calculated magnetization DQ axis current commands Id2 * and Iq2 * to the command selection unit 23.

  The magnetizing current command calculation unit 30 includes a magnetization current command calculation unit 31 and a torque current command calculation unit 32.

  FIG. 11 is a configuration diagram showing a configuration of the magnetizing current command calculation unit 31 according to the present embodiment.

  The magnetization current command calculation unit 31 includes a magnetization characteristic setting unit 71 and an internal magnetization current command calculation unit 72.

  The minimum magnetic flux value φmin managed by the magnetic flux management unit 21 is input to the magnetization characteristic setting unit 71. The magnetization characteristic setting unit 71 determines the magnetization characteristic Fimag based on the minimum magnetic flux value φmin. The magnetization characteristic setting unit 71 outputs the determined magnetization characteristic Fimg to the magnetization current command calculation unit 72 and the magnetization management unit 29.

  Here, a method for determining the magnetization characteristic Fimg will be described.

  The magnetization characteristic Fimg is a function of the magnetization current (D-axis current) Imag and the magnetic flux φ of the variable magnetic force magnet 41. In general, the magnetization characteristic Fimag is a function such that φ = F (φmin, Imag). Therefore, by determining the minimum magnetic flux value φmin, the function F (Imag) is obtained in which the magnetic flux φ is obtained from the magnetization current Imag. This function becomes the magnetization characteristic Fimg.

  In addition, the magnetization characteristic Fimg depends on the magnet temperature. Therefore, in order to increase the accuracy of specifying the magnetization characteristic Fimag, the magnet temperature of the rotor 40 or the variable magnetic force magnet 41 may be detected or estimated, and the magnetization characteristic Fimag may be determined according to these temperatures.

  The internal magnetization current command calculation unit 72 includes a magnetization characteristic Fimg determined by the magnetization characteristic setting unit 71, a magnetic flux target value φ * managed by the magnetic flux management unit 21 (determined by the magnetization management unit 29), and magnetic flux management. The current magnetic flux value φn managed by the unit 21 and the normal D-axis current command Id1 * calculated by the normal current command calculation unit 22 are input.

  The internal magnetization current command calculation unit 72 performs the following calculation.

  First, the internal magnetization current command calculation unit 72 is based on the magnetization characteristic Fimg determined by the magnetization characteristic setting unit 71 and the magnetic flux target value φ * managed by the magnetic flux management unit 21 (determined by the magnetization management unit 29). Thus, a magnetization current command (D-axis current command) Id2 * necessary for magnetizing the variable magnetic magnet 41 to the magnetic flux target value φ * is calculated. The internal magnetizing current command calculating unit 72 calculates the magnetizing current command Id2 * based on the inverse function of the function F (Imag) indicating the magnetization characteristic Fimg.

  A method for realizing this calculation is, for example, as follows. The internal magnetization current command calculation unit 72 stores, in the magnetization characteristic setting unit 71, data in a table format representing the correspondence between the magnetic flux target value φ * and the magnetization current command Id2 * for each magnetization characteristic Fimg. The magnetization characteristic setting unit 71 determines the magnetization current command Id2 * with reference to the table of the determined magnetization characteristics Fimg. Alternatively, the internal magnetization current command calculation unit 72 stores a calculation procedure of the inverse function of the magnetization characteristic Fimg stored in advance. The internal magnetization current command calculation unit 72 calculates the magnetization current command Id2 * by substituting the magnetic flux target value φ * into the calculation procedure of this inverse function.

  Next, the internal magnetization current command calculation unit 72 generates the magnetization current command Id2 * necessary to obtain the magnetic flux target value φ * calculated as described above, the current magnetic flux value φn managed by the magnetic flux management unit 21, and Based on the normal D-axis current command Id1 * calculated by the normal-time current command calculation unit 22, the change amount of the magnetization current command Id2 * corresponding to the progress of the magnetization process as shown in FIG. 8 is calculated.

  The internal magnetization current command calculation unit 72 outputs the calculated magnetization current command Id2 * to the torque current command calculation unit 32 and the command selection unit 23.

  The torque current command calculation unit 32 receives the magnetization current command Id2 * calculated by the magnetization current command calculation unit 31, the torque command Trq *, and the current magnetic flux value φn managed by the magnetic flux management unit 21.

  Based on the magnetization current command Id2 *, the torque command Trq *, and the current magnetic flux value φn, the torque current command calculation unit 32 determines a torque current command Iq2 * corresponding to the progress of the magnetization process as shown in FIG. . The determination method of the torque current command Iq2 * in the magnetization process is for the purpose of eliminating the torque discontinuity or ensuring the voltage margin of the inverter output voltage for applying the magnetization current Imag (D-axis current Id). Determined by When the magnetizing current Imag is small, the torque current command Iq2 * is determined by the following equation so that the torque discontinuity is eliminated as much as possible.

Iq * 2 = T * / Pn / (Ld−Lq) / Id2 *
Here, Pn is the number of pole pairs, Ld is a D-axis inductance, and Lq is a Q-axis inductance.

  On the other hand, in order to allow magnetization in a high speed region, a margin of the inverter output voltage is necessary. For this purpose, the Q-axis current command Iq2 * is reduced so as to approach zero. Thereby, the margin of an inverter output voltage is securable.

  The torque current command calculation unit 32 determines the torque current command Iq2 * at the time of magnetization by selecting or combining these determination methods according to the use and purpose.

  According to the present embodiment, when partial demagnetization as shown in FIG. 4 is performed, the type in which the magnetization characteristic changes, in particular, the type in which the magnetization characteristic on the magnetizing side changes (magnetization characteristic variable type variable magnetic magnet). The magnetizing current command Id * suitable for the process of magnetizing to the desired magnetic flux target value φ * can also be determined for the variable magnetic force memory motor 2 in which the above is applied to the variable magnetic force magnet. Thereby, it is possible to control the magnetic force with high accuracy even for the variable magnetic memory motor 2 to which the variable magnetic magnet of variable magnetization characteristics is applied.

  Thus, by controlling the magnetic force of the variable magnetic force memory motor 2 to which the variable magnetic force magnet of variable magnetization characteristics is applied with high accuracy, a partial reduction can be achieved compared to the variable magnetic force memory motor to which the variable magnetic force magnet not of variable magnetic characteristics is applied. The magnetization current Imag when increasing the magnetization from the magnetism can be reduced. Thereby, it is possible to increase the magnetization even in a high speed region. Therefore, the motor efficiency of the variable magnetic force memory motor 2 can be improved.

  For example, when the variable magnetic force memory motor 2 is applied to an electric vehicle or the like, the magnetic force is minimized when traveling at high speed. On the other hand, it is not necessary to minimize the magnetic force when traveling in urban areas. Therefore, once the magnetic flux of the variable magnetic force memory motor 2 is partially demagnetized while traveling in an urban area, the magnetizing current Imag when increasing the magnetization thereafter can be reduced.

  Also, by providing the magnetic flux reset processing unit 58 in the magnetization management unit 29, the magnetization is magnetized to the maximum magnetic flux value φ1 when a predetermined condition is satisfied. The variable magnetic magnet 41 having a variable magnetization characteristic is characterized in that the magnetization characteristic Fimg changes depending on the magnetization history. For this reason, the minimum magnetic flux value φmin is managed. However, there is a possibility that the managed minimum magnetic flux value φmin may deviate from the actual value due to the control of the magnetizing current accuracy or magnet temperature change. In such a case, for example, when the magnetic force control that is considered to be optimal is aimed at the maximum efficiency, the optimality may be lost, resulting in a situation where the efficiency is deteriorated or the necessary torque is insufficient. . Therefore, by maximizing the magnetic force by the magnetic flux reset function of the magnetic flux reset processing unit 58, it is possible to reliably make the magnetization characteristic Fimag that may be uncertain to the maximum magnetic characteristic Fimag. Thereby, the variable magnetic force memory motor drive apparatus 1 can be maintained at high output and high output characteristics.

  Further, by reducing the magnetizing current Imag for magnetizing the variable magnetic force magnet 41, the rotational speeds N1 and N2 shown in FIG. 6 where magnetizing is performed can be shifted to the higher speed rotation side. In addition, since the inverter output voltage cannot be secured, it is possible to reduce the situation where the variable magnetic force magnet 41 cannot be magnetized (or demagnetized). Therefore, it is possible to reduce a situation such as a decrease in motor efficiency due to inability to magnetize or a lack of necessary torque. Therefore, the variable magnetic force memory motor drive device 1 can improve the operation efficiency.

  Although the rotor 40 of the variable magnetic force memory motor 2 has been described with the structure shown in FIG. 2, the structure of the variable magnetic force memory motor 2 is not limited to this structure. Any structure can be used as long as the motor can change the magnetic flux of the motor by changing the magnetic force of the permanent magnet, and the motor can meet the gist of the present embodiment.

  Further, in the present embodiment, the magnetization characteristic Fimag has been described as five stages in FIG. 4, but is not limited thereto. The magnetization characteristic Fimag may be any one of steps lower than five steps, more than five steps, or stepless. By storing functions or tables corresponding to the respective magnetization characteristics Fimg in the control unit 9 in advance, it is possible to realize the magnetization characteristics Fimg having the number of stages as described above.

  In addition, the case where the magnetic flux reset processing unit 58 of the magnetization management unit 29 resets the magnetic force of the variable magnetic force magnet 41 to the maximum magnetic flux φ1 (the magnetic flux value φa in FIG. 6) by flowing the maximum magnetizing current I5 has been described. However, the maximum demagnetization current I10 may be supplied to reset to the minimum magnetic flux φ6 (the magnetic flux value φc in FIG. 6).

  Further, in the present embodiment, the transition condition from the magnetization mode 1 to the magnetization mode 2 or the subsequent condition from the magnetization mode 2 to the magnetization mode 0 is set as the DQ axis current command Id *, Iq * (or DQ axis current Id, Iq). However, it may be determined based on time. That is, the transition to each magnetization mode is performed by time management by determining in advance the time until the DQ axis current commands Id *, Iq *, etc. reach the target value as a condition for transition to the next magnetization mode. Can do.

  In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Variable magnetic force memory motor drive device, 2 ... Variable magnetic force memory motor, 3 ... Rotor position detector 3, 4 ... Inverter, 5 ... DC power supply, 6 ... Smoothing capacitor, 7 ... DC voltage detector, 8U, 8W ... Motor Current detector, 9 ... control unit, 21 ... magnetic flux management unit, 22 ... normal current command calculation unit, 23 ... command selection unit, 24, 26 ... coordinate conversion unit, 25 ... current control unit, 27 ... PWM circuit, 28 ... rotational speed calculation unit, 29 ... magnetization management unit, 30 ... current command calculation unit during magnetization, 33d, 33q ... subtractor.

Claims (11)

A synchronous motor with a variable magnetic magnet that changes its magnetic properties by magnetizing it,
Magnetization characteristic specifying means for specifying the magnetization characteristic of the variable magnetic force magnet;
Magnetic flux target value determining means for determining a magnetic flux target value that is a target value of the magnetic flux of the variable magnetic magnet after magnetization based on the rotational speed of the synchronous motor;
Magnetization current determination means for determining a magnetization current to flow to magnetize the variable magnetic force magnet based on the magnetization characteristics specified by the magnetization characteristic specification means and the magnetic flux target value determined by the magnetic flux target value determination means When,
A motor drive device comprising magnetizing current output means for outputting the magnetizing current determined by the magnetizing current determining means to the synchronous motor. Minimum magnetic flux value storage means for storing a minimum magnetic flux value that is the smallest magnetic flux value of the variable magnetic magnet magnetized within a predetermined time;
The motor drive apparatus according to claim 1, wherein the magnetization characteristic specifying unit specifies the magnetization characteristic based on the minimum magnetic flux value stored in the minimum magnetic flux value storage unit. 3. A magnetic flux reset means for performing magnetization for resetting the variable magnetic magnet to a maximum magnetic flux or a minimum magnetic flux in order to improve the specific accuracy of the magnetization characteristic. The motor drive device described in 1. 4. The motor drive device according to claim 3, wherein the magnetic flux resetting unit magnetizes the resetting when the rotational speed of the synchronous motor is lower than a predetermined value. 4. The motor drive device according to claim 3, wherein the magnetic flux resetting unit magnetizes the resetting when the rotational speed of the synchronous motor increases from a predetermined value. 4. The motor drive device according to claim 3, wherein the magnetic flux resetting unit performs the magnetization for resetting when the magnetization of the variable magnetic force magnet is executed a predetermined number of times. 4. The motor drive device according to claim 3, wherein the magnetic flux resetting unit performs the magnetization for resetting when the magnetization for resetting is not performed within a predetermined time. 5. Torque current determining means for determining a torque current to flow so as to eliminate torque discontinuity of the synchronous motor, when outputting the magnetized current determined by the magnetized current determining means to the synchronous motor;
The motor drive device according to any one of claims 1 to 7, further comprising torque current output means for outputting the torque current determined by the torque current determination means to the synchronous motor. . When outputting the magnetizing current determined by the magnetizing current determining means to the synchronous motor, torque current determining means for determining a torque current to flow so as to ensure a voltage margin to be output to the synchronous motor;
The motor drive device according to any one of claims 1 to 7, further comprising torque current output means for outputting the torque current determined by the torque current determination means to the synchronous motor. . An inverter control device that controls an inverter that supplies AC power to a synchronous motor that includes a variable magnetic magnet that is magnetized to change magnetic force and change in magnetization characteristics,
Magnetization characteristic specifying means for specifying the magnetization characteristic of the variable magnetic force magnet;
Magnetic flux target value determining means for determining a magnetic flux target value that is a target value of the magnetic flux of the variable magnetic magnet after magnetization based on the rotational speed of the synchronous motor;
Magnetization current determination means for determining a magnetization current to flow to magnetize the variable magnetic force magnet based on the magnetization characteristics specified by the magnetization characteristic specification means and the magnetic flux target value determined by the magnetic flux target value determination means When,
An inverter control apparatus comprising: a magnetizing current control unit that controls to output the magnetizing current determined by the magnetizing current determining unit to the synchronous motor. A method for controlling a synchronous motor that controls a synchronous motor including a variable magnetic magnet that is magnetized to change a magnetic force and change a magnetization characteristic,
Identifying the magnetization characteristics of the variable magnetic magnet;
Determining a magnetic flux target value that is a target value of the magnetic flux of the variable magnetic magnet after magnetization based on the rotational speed of the synchronous motor;
Determining a magnetization current to flow to magnetize the variable magnetic magnet based on the identified magnetization characteristics and the determined magnetic flux target value;
Outputting the determined magnetizing current to the synchronous motor. A method for controlling a synchronous motor, comprising:

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