JP2014023338A - Permanent magnet motor and drive method for the same, and control device for the permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive method for a permanent magnet motor, the permanent magnet motor device, and a control device for the permanent magnet motor, capable of quickly raising a temperature of a magnet to prevent permanent demagnetization of the magnet without causing torque pulsation nor noise.SOLUTION: In a drive method for a permanent magnet motor, a ferrite magnet is used for one of a rotor and a stator, and for the other of the stator and the rotor, a permanent magnet motor provided with a coil supplied with an AC current is driven by controlling a d-axis current component and a q-axis current component on the basis of vector control. In the drive method for the permanent magnet motor, the d-axis current component and the q-axis current component are calculated on the basis of an operation state of the permanent magnet motor, and a magnet temperature in the permanent magnet motor is calculated. When the calculated temperature is lower than a predetermined value, the d-axis current component is added so as to magnetize the magnet, and then, the permanent magnet motor is operated.

Description

  The present invention relates to a permanent magnet motor, and more particularly to a technique for preventing permanent demagnetization of a magnet of a permanent magnet motor using a ferrite magnet.

  One factor that determines the maximum current that can be passed to a permanent magnet motor is the demagnetization of the permanent magnet. In a permanent magnet motor, depending on the magnet material used by the motor and its shape, if an armature current exceeding the maximum current determined by the motor structure is applied, irreversible demagnetization occurs in the magnet and the current is returned to a small value again. However, there is a problem that the magnetic flux of the demagnetized magnet does not recover to the initial value. Here, this state is called “permanent demagnetization”. In particular, a motor using a ferrite magnet has a property that the coercive force of the magnet decreases as the temperature decreases. For this reason, since the armature current that causes permanent demagnetization decreases as the temperature decreases, the possibility of permanent demagnetization increases when handled in the same way as high temperatures or temperatures during normal operation. For this reason, it is necessary to take measures to prevent the magnet from causing permanent demagnetization at low temperatures.

  Therefore, conventionally, in order to prevent permanent demagnetization, for example, in Patent Document 1 below, a heating element is provided in the motor, and the heating element is operated at a low temperature to prevent the motor temperature from becoming low. The equipment to do is introduced. Further, in this document, it is also described that the motor is heated by passing a small current that does not rotate the motor in the armature winding instead of the heating element. In Patent Document 2 below, a method is described in which a high-frequency current is passed through the armature winding to quickly heat the motor. Furthermore, in the following Patent Document 3, it is described that when the temperature is lower than the set temperature, the value of the current flowing through the motor is limited.

JP 62-81951 A Japanese Patent Laid-Open No. 9-275696 JP 2004-187339 A

  However, the above-described conventional technology has the following problems. That is, in the method described in Patent Document 1, a heating element must be provided separately in order to increase the temperature of the motor. Further, in the method of passing an armature current without providing a heating element and making the current so small that the motor does not rotate, the loss is small because the current is small. Therefore, in practice, it is difficult for the motor to increase in temperature with such a small current. Moreover, in the method described in Patent Document 2, since a high-frequency current is passed, there is a problem that depending on the frequency, unnecessary torque pulsation is generated in the motor or noise is generated from the motor. The method described in Patent Document 3 does not raise the temperature of the motor itself, so is not suitable for preventing permanent demagnetization at low temperatures, which is related to the present invention, and limits the current value. Therefore, there is a problem that the generated torque is also limited.

  The present invention has been made in view of the above-described problems in the prior art, and the object of the present invention is to rapidly increase the temperature without generating torque pulsation or noise, so that the ferrite magnet can be used even in a low temperature environment. A permanent magnet motor capable of preventing permanent demagnetization, a method for driving the permanent magnet motor, and a control device for the permanent magnet motor are provided.

  In order to achieve the above object, according to the present invention, first, a ferrite magnet is used for one of a rotor or a stator, and the other stator or the rotor is provided with a winding to which an alternating current is supplied. A method of driving a permanent magnet motor for driving a motor by controlling a d-axis current component and a q-axis current component based on vector control, wherein the d-axis current command is based on an operating state of the permanent magnet motor. A component and the q-axis current command component, and the temperature of the permanent magnet motor is obtained. When the obtained temperature is lower than a predetermined value, the d-axis current command component is added to magnetize the magnet. Thus, a method for driving a permanent magnet motor for operating the permanent magnet motor is provided.

  In the present invention, in the driving method of the permanent magnet motor described above, it is preferable to flow the d-axis current component for increasing the magnet in the operation preparation stage or the stop stage of the permanent magnet motor. It is preferable to change the addition command to be added to the d-axis current command component according to the determined motor temperature predetermined value.

  In addition, according to the present invention, in order to achieve the above-described object, a permanent magnet using a ferrite magnet for one of the rotor and the stator and provided with a winding for supplying an alternating current to the other stator or the rotor. A permanent magnet motor comprising a motor and a motor drive current supply device for supplying an alternating current to the winding provided in the permanent magnet motor, wherein the motor drive current supply device is a d-axis current based on vector control. A control device for controlling the component and the q-axis current component, and the control device adds the d-axis current command component when the temperature is lower than a predetermined value based on the temperature of the permanent magnet motor. A permanent magnet motor configured as described above is provided.

  According to the present invention, the permanent magnet motor described above further includes a sensor for detecting and obtaining the temperature of the motor, or means for estimating and obtaining the temperature of the motor. Preferably, it further includes means for obtaining an addition command to be added to the d-axis current component based on the temperature of the motor obtained by the sensor or the temperature estimating means. And it is preferable that the permanent magnet motor apparatus described above is utilized as a power source of a machine tool or a servo press apparatus.

  Further, according to the present invention, in order to achieve the above object, a ferrite magnet is used for one of the rotor and the stator, and the vector control is performed for the permanent magnet motor provided with the other stator or the rotor. A control device for a permanent magnet motor that controls the alternating current supplied to the winding based on the d-axis current component and the q-axis current component based on the vector control. An inverter device to be generated; a control device for determining the d-axis current command component and the q-axis current command component based on an operating state of the permanent magnet motor; and means for determining a magnet temperature of the motor In the control device for a permanent magnet motor provided, the control device adds the d-axis current command component when the magnet temperature of the permanent magnet motor is lower than a predetermined value. Controller for a permanent magnet motor that is configured is provided as.

  In the present invention, in the permanent magnet motor control apparatus described above, the means for obtaining the magnet temperature of the motor is preferably a temperature sensor provided in the motor, or the loss of the motor It is preferable to obtain the magnet temperature of the motor based on the temporal transition of the motor or based on the operation pattern of the motor.

  According to the present invention described above, a permanent magnet motor capable of preventing permanent demagnetization of a ferrite magnet even in a low temperature environment, a driving method thereof, and a control device for the permanent magnet motor are provided. When the applicable range of the magnet motor can be greatly expanded, an extremely excellent effect is exhibited.

It is a control block diagram which shows the permanent magnet motor which becomes one embodiment (Example 1) of this invention, and its control apparatus. It is a figure which shows an example of the relationship between the input (temperature T) and the output (addition command (DELTA) Id *) in the (DELTA) Id calculating part in the control apparatus of the said permanent magnet motor. It is a block diagram which shows the more detailed structural example of the correction process part in the control apparatus of the said permanent magnet motor. It is a control block diagram for implement | achieving the process of this invention in the control apparatus of the said permanent magnet motor. It is a figure which shows an example of the limit value produced | generated by the limiter calculating part shown in the said FIG. It is a flowchart for showing the detail of the control action in the control apparatus of the said permanent magnet motor. FIG. 7 is a flowchart showing details of control for executing control to actively flow a large d-axis current for speeding up the temperature rise of the motor during the operation shown in FIG. 6. It is a control block diagram of the control apparatus of the permanent magnet motor which becomes other embodiment (Example 2) of this invention. It is a section of the rotor and stator of a permanent magnet motor for explaining the basic principle of the present invention. It is a vector diagram of the armature current for demonstrating the basic principle of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, the basic principle of the present invention will be described with reference to the attached FIG. 9 and FIG.

  FIG. 9 is a diagram for illustrating the basic principle of the present invention, and in the drawing, shows a cross section of the motor of a permanent magnet motor of a rotor and a stator for approximately one pole pair.

  An N-pole magnet 501 and an S-pole magnet 502 are installed on the rotor surface, and a conductor 503 is wound as distributed windings in the stator slots as U, V, and W-phase windings. . Although the physical shape of the rotor and the stator is cylindrical, this figure is for explaining the principle of the present invention, and is described in a straight line here.

  FIG. 9A shows a state during normal operation. The magnetic flux of the magnet indicated by the solid line flows from the N pole of the magnet through the stator around which the armature winding is wound toward the S pole of the magnet. On the rotor side, the opposite side (shaft side) of the N pole magnet is the S pole, and the opposite side of the S pole magnet is the N pole, so that the magnetic flux also flows from N to S on the rotor side.

  Next, when a current is passed through the armature winding, a magnetic flux is generated as shown by the broken line in the figure. The magnetic flux of the magnet and the magnetic flux of the armature winding are alternately in 90 ° phase. In a motor having a surface magnet (SPM) structure, when the magnetic flux of the magnet and the magnetic flux of the armature winding are in a phase relationship of 90 °, the largest torque is output for the same current. In the case of the illustrated armature winding magnetic flux, a torque is generated that moves the rotor to the right, and the rotor moves to the right. If the magnetic flux of the armature winding is reversed, that is, if the direction of current is reversed, the torque direction is switched and the rotor moves to the left.

  Here, the influence of the magnetic flux by the armature winding at the magnet end will be observed. As shown in the figure, the A part of the magnet 501 is demagnetized by receiving the magnetic flux in the direction opposite to the magnet magnetic flux by the magnetic flux of the armature winding, and the B part of the magnet 502 is also demagnetized by the magnetic flux of the armature winding. . That is, in the magnet, the downstream end of the movement of the rotor is demagnetized. The ratio of demagnetization is larger toward the end side. For this reason, the demagnetization at the magnet end increases as the armature current increases. When the armature current exceeds a certain value, in other words, when the external magnetic field exceeds the refraction point of the magnet BH characteristic, permanent demagnetization occurs. That is, irreversible demagnetization occurs in which the magnetic flux of the magnet does not return to the original even when the current is returned to zero.

  As already described, in the ferrite magnet, the coercive force of the magnet becomes smaller as the temperature becomes lower, so that the A part and B part of the magnet are more likely to be permanently demagnetized as the temperature becomes lower. That is, there is a possibility that permanent demagnetization will not occur even if a large current is applied to generate a large torque at a high temperature, even if the same current is applied at a low temperature. Thus, in a ferrite magnet having a small coercive force, consideration must be given to permanent demagnetization at the end of the magnet as the temperature decreases.

  FIG. 9B is a diagram illustrating the principle of the present invention that prevents permanent demagnetization at low temperatures. As shown in the figure, the magnetic flux of the armature winding is phase-shifted as shown in FIG. That is, the phase of the current is maintained so that a positive d-axis current flows. As can be seen from the figure, the magnetic flux component of the armature winding that demagnetizes the magnet is greatly reduced in the A portion of the magnet 501 and the B portion of the 502, and is difficult to be demagnetized. That is, demagnetization of the magnet is prevented by flowing a positive d-axis current component that increases the magnet's magnet.

  This principle is shown in the attached FIG. 10 as a vector diagram of the armature current on the dq axis. In normal operation, as shown in FIG. 10A, the armature current Ia is a q-axis component that contributes to torque. On the other hand, when the temperature is low, as shown in FIG. 10B, a positive d-axis component for magnetizing the magnet is passed. The method of flowing the d-axis current is called field control. As the field control, the maximum torque control for increasing the torque with an embedded magnet (IPM) motor, or for operating the motor in a high-speed range in either SPM or IPM. Field weakening control is known, and in both cases, a negative d-axis current is passed. In general, in a magnet motor, positively flowing a positive d-axis current is not utilized.

  A control block of a permanent magnet motor device for preventing permanent demagnetization of a ferrite magnet, including a permanent magnet motor using a ferrite magnet and its driving device, according to the basic principle of the present invention described above is shown in FIG. . This control block is an example constituting a speed control system, and the drive system itself is a method already known as vector control of a permanent magnet motor.

  A permanent magnet motor 11 having a ferrite magnet mounted on a rotor is driven by an inverter 12 as a motor drive current supply device. The power source side of the inverter 12 includes an AC power source 14, a power source converter 15, and an energy storage device 16. The AC voltage of the AC power supply 14 is converted into a DC voltage by the power supply converter 15, and the energy storage device 16 composed of a capacitor is charged via the DC bus 17 and the DC voltage is applied to the inverter 12. With this configuration, instantaneous energy is supplied from the energy storage device 16 to the load of the motor 11, and the facility capacity of the AC power supply 14 is reduced. This device is characterized by including an energy storage device. A power supply device having such a configuration, that is, a power converter, an energy storage device, an inverter connected by a DC bus, and supplying instantaneous energy of a motor load from the energy storage device is, for example, a servo press device (for example, a special No. 2007-331023).

  The encoder 13 detects the rotational position of the permanent magnet motor 11. This detection signal is input to the speed control unit 102. Then, the speed control unit 102 operates according to the deviation between the speed command from the speed command unit 101 and the rotational speed signal obtained from the rotational position signal from the encoder 13 and outputs a torque command signal. The torque command signal is input to the Id / Iq calculation unit 103 that commands the d-axis and q-axis current components. The Id / Iq calculation unit 103 performs calculation for generating d and q axis current commands Id * and Iq * according to the torque command. For example, in an embedded magnet (IPM) motor, a maximum torque calculation is performed to command a current component that maximizes the torque of the permanent magnet motor 11 in response to a torque command, and the current of each component is commanded. The d-axis current command Id * at this time is a minus command.

  As will be described later, the adder 154 corrects the command value of the d-axis current command Id *. As will be described later, the limit value processing unit 161 limits the maximum value (absolute value) of the q-axis current command Iq *. The Id / Iq current control unit (Id / IqACR) 104 is a d / q after coordinate conversion obtained from the actual current command for each of the d-axis / q-axis and the current detection value of the current detector 107 via the coordinate conversion unit 107. It works according to the deviation from the detected shaft current value and outputs a voltage command for the d / q axis. This signal is converted into a voltage command for each phase of UVW by the coordinate conversion unit 105 and input to the PWM control unit 108. Thus, PWM control is executed by the inverter 12, and the motor current is controlled in accordance with the current command.

  Since this control method is well known as vector control of a permanent magnet motor, its detailed description is omitted here. At this time, it is also well known that the Id / Iq current control unit 104 performs non-interference control between the d-axis and the q-axis. In addition, FIG. 1 shows an example in which operation is performed with a speed command, but it is also well known that a position control system is provided above the speed control system, and operation with a rotational position command is possible.

  Next, a control block for preventing permanent demagnetization at low temperatures, which is a feature of the present invention, will be described. In the example of FIG. 1, control blocks 151 to 154 are added, whereby a d-axis current command correction signal is calculated. The temperature detector 151 detects the magnet temperature of the permanent magnet motor 11. As this temperature, for example, a temperature sensor 111 is installed in the motor 11, and the temperature of the magnet is detected from the temperature in the motor. The ΔId calculation unit 152 performs a calculation according to the detected temperature, and calculates an addition command ΔId * for flowing a positive d-axis current when the temperature of the magnet is low. That is, the current component in the direction in which the magnet is increased is commanded. In this example, since the temperature of the motor is detected by the temperature sensor 111, which is used as the magnet temperature, the magnet temperature can be detected, and permanent demagnetization of the magnet can be reliably prevented. Here, the magnet temperature is obtained as the motor temperature by the temperature sensor installed in the motor, but instead of this, for example, a temperature sensor may be installed in a part of the magnet and obtained directly. It will be possible.

  An example of outputting a d-axis current addition command ΔId * in the calculation by the ΔId calculation unit 152 is shown in FIG. As shown in this figure, when the temperature of the motor (more strictly speaking, it is the magnet temperature, but is hereinafter collectively referred to as “motor temperature” or simply “temperature”) is lower than a predetermined value. , A positive addition current ΔId * is commanded. More specifically, at a temperature T2 or higher, the d-axis added current is zero, and when the temperature is lower than T2, the added value of the d-axis current is added. The added value increases as the temperature decreases, and the motor temperature is lower than T1. In this case, the added value is ΔId1. Since the added value is a positive d-axis current, it is a magnetizing component that does not demagnetize the magnet. In addition, since the d-axis current hardly participates in the torque, a large current can be passed as the d-axis current. That is, ΔId1 can be set as large as possible. Therefore, the temperature of the motor can be raised quickly. The temperature conditions and the magnitude of the command current are determined not only by the characteristics of the magnet material, but also by the structure of the motor and how it is used, the ambient environment, the motor operating conditions, the torque application method, the specifications of the inverter that drives the motor, etc. .

  ΔId1 is not limited to a fixed value, but may be a value that can be changed depending on other conditions. For example, if ΔId1 set for low speed operation is given during high speed operation, the induced voltage of the motor may increase excessively. In such a case, ΔId1 may be set to a smaller value according to the speed, that is, as the speed increases.

  Here, returning to FIG. 1 described above, the addition value ΔId * from the ΔId calculation unit 152 is input to the correction processing unit 153, where it is corrected to the correction command ΔId **. Although the addition command ΔId * itself has little influence on the torque, if the q-axis current command Iq * increases to generate torque during actual operation, the magnet is easily demagnetized by this current component. The correction processing unit 153 is a process for preventing such demagnetization of the magnet, and further corrects the positive d-axis current in the increasing direction in accordance with the q-axis current command Iq *. That is, it is difficult to generate demagnetization of the magnet, thereby preventing permanent demagnetization.

  FIG. 3 shows a specific example of the correction processing unit 153 described above. The coefficient calculation unit 1531 determines the rate at which the addition command ΔId *, which is the output from the ΔId calculation unit 152, increases according to the absolute value of the q-axis current command Iq *. When Iq * is zero (0), the ratio is 1. When the absolute value of Iq * is larger than this, the ratio is larger than 1. The multiplication unit 1532 performs a calculation for correcting the addition value ΔId * and outputs a correction value ΔId **. The output from the multiplying unit 1532 is added to the d-axis current command Id * by the adding unit 154, and becomes an actual d-axis current command.

  According to the control block that operates the permanent magnet motor having the above-described configuration, the demagnetization of the magnet can be reduced even in an operation state in which the motor outputs a large torque at a low temperature, and the irreversible demagnetization is reduced. Prevent it from occurring.

  Furthermore, according to the above-described control block, when the q-axis current flows to generate torque, the magnet is easily demagnetized, and thus the q-axis current is limited according to the temperature. That is, the limiter processing unit 161 in FIG. 1 performs further processing for preventing demagnetization.

  FIG. 4 is a control block diagram for realizing the further processing. The limiter value calculator 1611 calculates a limit value that limits the q-axis current according to the motor temperature detected by the temperature detector 151. When the temperature is equal to or lower than a predetermined value, the q-axis current is limited, and the limit value is decreased as the motor temperature is lower. An example of the limit value generated by the limiter calculation unit 1611 is shown in FIG. When the temperature is T11 or less, the q-axis current is limited to L1 or less, the limit value gradually increases as the temperature becomes higher than T11, and when the temperature is T12 or more, the limit value becomes L2. Here, the limit value L2 is an originally required limit value of the q-axis current that is unrelated to the temperature state of the motor. That is, it is not a value that limits the q-axis current from the viewpoint of the motor temperature.

  The limiter unit 1612 limits the actual q-axis current value by the limit value from the limiter value calculation unit 1611. That is, if the absolute value of the q-axis command Iq * from the Id / Iq calculation unit 103 is within the limit value, it passes as it is, and if it exceeds the limit value, it is limited to a plus or minus limit value. According to this process, the q-axis current that demagnetizes the magnet is suppressed according to the temperature, so that torque limitation is imposed, which may cause a slight hindrance to the operation. However, permanent demagnetization is surely prevented. It becomes possible to do.

  Now, in the control block configuration of FIG. 1 described above, an initial stage in which the power is turned on in order to operate a device (that is, a load (not shown)) driven by the motor 1 will be described. At this stage, the capacitor of the energy storage device 16 is not charged. Therefore, a capacitor is charged for operation, but a predetermined time is required to charge the capacitor. This time is a so-called operation preparation stage, and the operation for driving the motor is not performed at this stage. At this time, if a d-axis current addition command (ΔId *) is output from the start of charging and a current is supplied, the temperature of the motor can be increased even at this time (that is, the operation preparation stage). It is possible to further increase the temperature of the.

  The output of the d-axis current addition command in the operation preparation stage described above will be described in detail below with reference to the control flow shown in FIG. First, when preparation for operation is started (S101), charging of the capacitor of the energy storage device 16 is started by the power converter 15 (S102). Next, it is determined whether or not the motor temperature is lower than a predetermined value (S103). The motor temperature is obtained from the temperature detector 151. Here, the predetermined temperature is a temperature at which permanent demagnetization occurs when a current is supplied to the motor to output torque. If the temperature of the motor is higher than this predetermined temperature (“No” in S103), at this stage, current is not supplied to the motor, but only charging of the capacitor is performed (transition to S106).

  On the other hand, if the temperature of the motor is lower than the predetermined value (“Yes” in S103), an operation of flowing the d-axis current is performed with the motor stopped. First, the torque command is set to zero (0) (S104). At this time, the q-axis current command Iq * is zero (0). If the q-axis current is zero (0), no torque is generated in the motor even if the d-axis current flows in principle. In addition, since this state is an operation preparation stage before the actual operation of moving the motor, if the brake that stops the device is mounted on the servo press, for example, as a device (load) driven by the motor, it is safe. In order to ensure the above, it is preferable that the brake is applied.

  Then, the PWM signal is supplied to turn on the inverter 12, and as shown in FIG. 2, a d-axis current addition command (ΔId *) corresponding to the motor temperature is set, and the d-axis current is allowed to flow through the motor (S105). . Since the motor preparation stage is in a state where the motor is stopped, the current flowing through the armature of the motor at this time is a direct current. Furthermore, in order to ensure that the motor is never rotated, a device for preventing the current phase from changing, for example, fixing a position signal from the encoder 13 in the coordinate conversion units 105 and 107 shown in FIG. May be taken.

  The d-axis current given here may be given as an addition command (ΔId *) that is larger than the d-axis current addition command shown in FIG. Since only the d-axis current flows while the motor is stopped, the torque generated in principle is zero (0), and therefore it is possible to flow a relatively large current. That is, since a large current can be passed, the motor temperature can be further increased. Moreover, as described above, this current is a plus component that does not demagnetize the magnet.

  Thus, when the energy storage device 16 is charged, the voltage of the DC bus 17 gradually increases. At this time, as described above, the d-axis current is also supplied to raise the temperature of the motor. When a predetermined time elapses from the start of charging (S106), the DC bus voltage rises to a predetermined value, and charging is completed (S107). Then, a d-axis current addition command (ΔId *) corresponding to the motor temperature at this time is set (S108), and the actual operation for driving the motor is started from the operation preparation stage (S109).

  Note that the control flow shown in FIG. 6 described above is not only in the operation preparation stage of the device (that is, a load, such as a servo press), but the device is in operation, but the motor is in a stopped state. It can also be applied to cases. When the motor is stopped, that is, when the torque is zero (0), a larger d-axis current may be actively supplied in order to increase the temperature of the motor.

  FIG. 7 is a control flow for executing a control in which a large d-axis current for positively increasing the temperature of the motor is actively supplied during the operation of the apparatus described above. In this control flow, first, it is determined whether or not the motor temperature is higher or lower than a predetermined value (S201). As a result, if the temperature of the motor is higher than the predetermined temperature (“No” in S201), the process ends without generating a command for adding the d-axis current.

  On the other hand, if the motor temperature is lower than the predetermined value (“Yes” in S201), it is next determined whether or not the motor is stopped (S202). As a result, if not stopped (“No” in S202), a d-axis current addition command (ΔId *) corresponding to the motor temperature is calculated (S205). The addition command is output in the same manner as described above with reference to FIG.

  On the other hand, if the motor is stopped (“Yes” in S202), it is determined whether the torque command is zero (0) (S203). If the torque command is not zero (0) (“No” in S203), the torque is output and stopped and held, so the calculation shown in S205 is performed.

  That is, if the motor is stopped and the torque command is zero (0) (“Yes” in S203), since it is the same state as step S105 in FIG. 6, only the d-axis current is actively supplied. That is, a larger positive d-axis current is output as an addition command (ΔId *) (S204). Thus, since the motor is stopped and only the d-axis current is allowed to flow when the torque is zero (0), a relatively large current can be allowed to flow.

  Of course, this method is effective even during operation, but it is particularly effective for an apparatus that does not have an energy storage device and starts operation immediately after the power is turned on as shown in FIG. That is, since the motor is stopped at the stage of starting operation, a relatively large d-axis current can be flowed aiming at such a stopped state, so that the temperature rise of the motor can be accelerated.

  Further, according to the control method shown in FIG. 6 or FIG. 7 described above, since the d-axis current is allowed to flow before the actual operation of moving the motor is started, or the d-axis current is allowed to actively flow when stopped, the motor is considerably The temperature can be raised. That is, the motor winding is actively used in place of the heater, and the condition that leads to permanent demagnetization can be considerably eliminated during actual operation of moving the motor. Thus, the present embodiment is preferably implemented in a motor that is used as a power source in a machine tool or a servo press device.

  In the above-described embodiment, the method of controlling the motor separately for the d-axis current and the q-axis current (orthogonal coordinate method) has been described. However, the present invention is not limited to this, and FIG. As described in the above principle, it is needless to say that the control can be carried out by a broad vector control method (polar coordinates) in which the control is performed based on the concept of phase shifting of the current, that is, the control is divided into the magnitude and phase of the current. Alternatively, the control may be performed so that the positive d-axis current component is substantially increased at a low temperature by another control method. Furthermore, although the permanent magnet motor 11 has been described as a motor of a ferrite magnet, other magnet materials whose coercive force decreases as the temperature becomes lower may be used similarly to the ferrite magnet. In the present invention, magnets having this property are collectively referred to as “ferrite magnets”.

  Next, Embodiment 2 which is another embodiment of the present invention will be described below with reference to FIG. Unlike the first embodiment, this embodiment is characterized in that the motor temperature is not directly detected but estimated. Also in this embodiment, the same parts shown in FIG. 1 are given the same numbers.

  By the way, especially a machine tool and a servo press apparatus operate the motor 11 by an operation command. That is, an operation command such as an operation pattern within one stroke of the press machine is output from the operation command unit 201. The position calculation unit 202 calculates a rotational position command every moment according to the operation command from the operation command unit 201. Further, the position / speed control unit 203 calculates a working speed command according to the deviation between the position command from the position calculation unit 202 and the position signal from the encoder 13, and further, the speed / speed control unit 203 calculates the speed based on the speed command and the position signal from the encoder 13. A signal is obtained and a torque command for commanding the torque of the motor 11 is output according to these deviations. The subsequent operation is the same as in the first embodiment.

  Next, the temperature estimation unit 204 that is a feature of the present embodiment will be described. The temperature estimation unit 204 estimates the motor temperature from the operating state by the method described below. The ΔId calculation unit 152 performs a calculation according to the temperature estimated by the temperature estimation unit 204, and calculates an addition command ΔId * for flowing a positive d-axis current when the magnet temperature is lower than a predetermined value. The addition signal is input to the correction processing unit 153, and a correction command ΔId ** is output from the correction processing unit 153. Then, the output of the correction processing unit 153 is input to the addition unit 154, and the d-axis current command is corrected. The correction operation is the same as in the first embodiment.

<Motor temperature estimation method 1>
Since the motor loss is determined by the current flowing through the motor and the motor rotation speed, the motor temperature can be estimated from these temporal transitions. That is, since the copper loss, the iron loss, and the mechanical loss are obtained as a function of the detected Id and Iq values and the rotational speed (obtained from the rotational position signal of the motor), the motor loss can be known. From the time transition of these losses, the temperature rise of the motor is determined in consideration of the temperature time constant determined from the motor cooling system. The temperature estimation unit 204 receives Id, Iq, and the detected speed value (see the broken line in the figure). The calculation of the motor temperature rise in the temperature estimation unit 204 can be calculated from a theoretical or experimental calculation formula, or can be calculated using a map having the detected value as a function.

  That is, by the above calculation, the motor temperature increase due to the operating state is calculated, and the motor temperature can be estimated. In the case of air cooling, the absolute motor temperature should be the temperature of the air that is input to cool the motor, or the equivalent outside temperature, and in the case of water cooling, measure the water temperature entering the water cooling section. Thus, the motor temperature is estimated as the sum of the temperature rise and the input temperature.

  In the above estimation, the detected values of Id and Iq and the detected value of the rotational speed are used, but equivalent values may be used. For example, instead of these detection values, those command values can be used.

<Motor temperature estimation method 2>
Moreover, the driving | running pattern from the driving | operation instruction | command part 201 can be memorize | stored and motor temperature can also be estimated from this time transition. In particular, in a machine tool or a servo press device, it is possible to know at what rotation speed and torque the operation pattern is used, so the heat generation of the motor can be calculated. That is, the temperature state of the motor is estimated in consideration of the temporal transition from the start of operation. If the motor is stopped, the time after the stop is also taken into account. A signal from the operation command unit 201 is input to the temperature estimation unit 204 (one-dot chain line in the figure). The method for estimating the absolute temperature of the motor in consideration of the ambient temperature is the same as in <Method 1>.

  Thus, in this embodiment, since the motor temperature is obtained by estimation, it is not necessary to provide a sensor for temperature detection in the motor, that is, the installation of the sensor itself can be omitted, and the apparatus can be manufactured at a lower cost. This has the advantage that the wiring of the detector from the motor can be omitted.

  As described in detail above, according to the present invention, when the magnet temperature of the motor is low, a positive d-axis current is passed, thereby preventing demagnetization without affecting the output torque. Is possible. The above-described embodiments are merely examples, and for example, a part of them can be simplified, or methods that can be used among the embodiments can be mutually used.

  DESCRIPTION OF SYMBOLS 11 ... Permanent magnet motor, 12 ... Inverter, 13 ... Encoder, 14 ... AC power supply, 15 ... Power supply converter, 16 ... Energy storage device, 17 ... DC bus, 101 ... Speed command part, 102 ... Speed control part, 103 ... Id / Iq calculation unit, 104 ... Id / Iq current control unit, 105, 107 ... coordinate conversion unit, 106 ... current detection unit, 108 ... PWM control unit, 151 ... temperature detection unit, 152 ... ΔId calculation unit, 153 ... correction processing , 154... Adder, 161... Limiter processor, 1531... Coefficient calculator, 1532 .. Multiplier, 1611... Limiter value calculator, 1612.

Claims (10)

A ferrite magnet is used for one of the rotor and the stator, and a permanent magnet motor provided with a winding to which an alternating current is supplied to the other stator or the rotor, a d-axis current component and a q-axis current based on vector control. A method of driving a permanent magnet motor driven by controlling components,
Based on the operating state of the permanent magnet motor, the d-axis current command component and the q-axis current command component are obtained,
Find the magnet temperature in the permanent magnet motor,
When the obtained temperature is lower than a predetermined value, the permanent magnet motor is operated by adding the d-axis current command component so that the magnet is magnetized.   The method for driving a permanent magnet motor according to claim 1, wherein the d-axis current component for magnetizing the magnet is supplied in an operation preparation stage or a stop stage of the permanent magnet motor. Driving method of permanent magnet motor.   3. The method of driving a permanent magnet motor according to claim 2, wherein an addition command added to the d-axis current command component is changed according to the determined motor temperature predetermined value. Driving method. A permanent magnet motor main body provided with a winding for supplying an alternating current to the other stator or the rotor while using a ferrite magnet for one of the rotor or the stator,
A permanent magnet motor comprising a motor drive current supply device for supplying an alternating current to the winding provided in the permanent magnet motor body;
The motor drive current supply device includes a control device that controls a d-axis current component and a q-axis current component based on vector control,
The controller is configured to add the d-axis current component based on the temperature of the permanent magnet motor when the temperature is lower than a predetermined value.   5. The permanent magnet motor according to claim 4, further comprising a sensor for detecting and obtaining the temperature of the motor, or means for estimating and obtaining the temperature of the motor. Permanent magnet motor.   6. The permanent magnet motor according to claim 5, further comprising means for obtaining an addition command to be added to the d-axis current component based on the temperature of the motor obtained by the sensor or the temperature estimating means. A permanent magnet motor characterized by that.   The permanent magnet motor according to any one of claims 4 to 6, wherein the permanent magnet motor is used as a power source of a machine tool or a servo press device. A permanent magnet that uses a ferrite magnet for one of the rotor and stator and controls the alternating current supplied to the winding based on vector control for a permanent magnet motor having a winding for the other stator or rotor A motor control device,
An inverter device that generates an alternating current supplied to the windings by a d-axis current component and a q-axis current component based on the vector control;
A control device for obtaining a d-axis current command component and a q-axis current command component based on the operating state of the permanent magnet motor;
In a control device for a permanent magnet motor comprising means for determining the magnet temperature of the motor,
The controller is configured to add the d-axis current command component when the magnet temperature of the permanent magnet motor is lower than a predetermined value.   9. The control apparatus for a permanent magnet motor according to claim 8, wherein the means for obtaining the magnet temperature of the motor is a temperature sensor provided in the motor.   In the control device for a permanent magnet motor according to claim 8, the means for obtaining the magnet temperature of the motor is based on a temporal transition of the loss of the motor or based on an operation pattern of the motor. A control device for a permanent magnet motor, characterized in that it determines the magnet temperature of the motor.

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