JP5326736B2 - Control device for three-phase AC motor - Google Patents

Description

  The present invention relates to a control device and a control method for a rotary magnet type three-phase AC motor, and more particularly to a control device and a control method for reducing a starting current at the time of starting the motor.

  2. Description of the Related Art A control device is known that controls an inverter and supplies a coil current to a rotary magnet type AC motor having a permanent magnet on a rotor and a coil on a stator. If an inverter is used, the frequency of the coil current and the energization phase can be controlled, and a control system such as a pulse width modulation system has been put into practical use. In order to ensure high controllability, not only the electric input is controlled according to the required torque required, but also the rotational position of the rotor and the coil current are sequentially detected and feedback controlled. . For example, in the biaxial theory described in Non-Patent Document 1, etc., the direction of the N pole of the permanent magnet on the rotor is the d axis, the direction rotated by an electrical angle of 90 degrees from the d axis is the q axis, Based on the rotational position, the three-phase coil current vector is converted into a two-axis current on the dq coordinate axis, the control amount is calculated by performing an operation on the dq coordinate axis, and the control amount on the three-phase region is converted by inverse conversion. Looking for.

  The operation control method using the biaxial theory includes maximum torque / current control, power factor 1 control, maximum efficiency control, and the like. Since each control method has advantages and disadvantages, the control method is usually selected in consideration of the application of the motor (p32 to 33 in Non-Patent Document 1, etc.). Of these, the maximum torque / current control is a control method in which the current phase that can maximize the generated torque is applied to the same effective coil current, and is effective when the current is limited. Has been.

Co-authored by Yoji Takeda et al., “Design and Control of Embedded Magnet Synchronous Motors”, Keibunsha, published in October 2001

  By the way, when a three-phase AC motor is controlled by the maximum torque / current control using the two-axis theory, a two-axis current is obtained from the required torque required for the motor and the rotational position of the rotor, and a three-phase converted from this is obtained. The coil current is uniquely determined. This maximum torque / current control method can minimize the effective current value that satisfies the required torque, but no special consideration has been given at the start. Therefore, depending on the rotational position of the rotor at the time of starting the motor, the instantaneous value of the starting current may be concentrated in one phase. In addition, if a condition where the starting torque itself is large or a condition where an inrush current is superimposed, an excessive starting current flows in one phase of the stator coil, which may cause damage due to heat generation. Further, current concentration in one phase also occurs in the inverter on the power supply side, so that the semiconductor power switch element may be damaged.

  Such a current concentration in one phase at the time of starting the motor and the risk of damage accompanying it cannot be avoided as long as the starting is performed according to the maximum torque / current control method. In addition, similar fears are included in other operation control methods.

  The present invention has been made in view of the above problems, and provides a motor control device and a control method capable of mitigating the concentration of a starting current in one phase when starting a rotary magnet type three-phase AC motor. Is a problem to be solved.

  The invention of a control device for a three-phase AC motor according to claim 1 that solves the above-described problem is characterized in that an inverter is controlled on the stator coil of a three-phase AC motor including a rotor having a permanent magnet and a stator having a stator coil. A control device for a three-phase AC motor for supplying a coil current, a position detection means for detecting the rotational position of the rotor, a current detection means for detecting the coil current, and a request required for the three-phase AC motor An operation control means for calculating a control output signal in accordance with a predetermined operation control system based on the torque and the detected rotational position and the coil current and sending it to the inverter, and a request for starting the three-phase AC motor Based on the detected starting position and the detected rotational position and coil current, instead of the predetermined operation control method, a three-phase starting current instantaneous Characterized in that it and a starting control means for sending to the inverter by calculating the control output signal in accordance with the starting current minimum satisfies control method for minimizing the maximum value in the values.

  According to a second aspect of the present invention, in the first aspect of the present invention, the start control unit includes a start current map in which the start current instantaneous value data condition that satisfies the start current minimum condition is used as parameters of the start torque and the rotational position. And the control output signal is calculated using the starting current map.

  According to a third aspect of the present invention, in the second aspect, the operation control unit and the start control unit perform an operation using a dq coordinate axis with reference to the direction of the permanent magnet on the rotor, and the start current map First, obtain a large number of relations between the current phase and effective value of a symmetrical three-phase coil current satisfying a specific starting torque, convert the current phase and effective value into a biaxial current value on the dq coordinate axis, The two-axis current value is inversely converted into the current phase of the three-phase coil current and the starting current instantaneous value under the condition that the rotor is at a specific rotational position, and the maximum value of the three-phase instantaneous starting current value is minimum. The current phase is determined as a specific current phase, and finally, a biaxial current value in the specific current phase is generated as a data set of the specific starting torque and the starting current instantaneous value at the specific rotational position. And wherein the door.

  According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, the predetermined operation control method is a maximum of energizing a current phase that can maximize a generated torque with respect to the coil current having the same effective value. It is a torque / current control system.

  The invention of a method for controlling an AC motor according to claim 5 that solves the above-described problem is a coil current obtained by controlling an inverter to the stator coil of a three-phase AC motor including a rotor having a permanent magnet and a stator having a stator coil. A detection step of detecting the rotational position of the rotor and the coil current, a required torque required for the three-phase AC motor, and the detected rotational position and coil An operation control step of calculating a control output signal in accordance with a predetermined operation control method based on the current and sending it to the inverter; and the rotational position detected when starting the three-phase AC motor and the required starting torque And based on the coil current, the maximum value among the three-phase starting current instantaneous values is minimized instead of the predetermined operation control method. And calculates the control output signal in accordance with the starting current minimum conditions are satisfied control method characterized by having a, a starting control step of transmitting to said inverter.

  In the invention according to claim 1, when starting the three-phase AC motor, instead of the operation control means according to a predetermined operation control method, the start control means minimizes the maximum value among the instantaneous values of the three-phase start currents. Start control is performed by a control method that satisfies the minimum start current condition. Therefore, the concentration of the starting current in one phase is relaxed, the maximum value among the instantaneous values of the three-phase starting current is reduced, and there is no possibility that the stator coil, the semiconductor power switch element of the inverter or the like is damaged.

  In the invention according to claim 2, the starting control means holds in advance the starting current instantaneous value data set that satisfies the starting current minimum condition in the starting current map. Therefore, the start control means can easily find the start current instantaneous value suitable for the start torque and the rotational position conditions on the start current map. Thereby, the calculation required time for calculating the control output signal is shortened, and the start control can be performed with a short cycle time.

  In the invention which concerns on Claim 3, a driving | running control means and a starting control means perform a calculation using a dq coordinate axis. Therefore, by using the three-phase / dq-axis conversion and the dq-axis / three-phase conversion together, it is possible to obtain a data set of the starting current instantaneous value that satisfies the starting current minimum condition at the specific starting torque and the specific rotational position. By repeating this procedure by changing the specific rotational position and further by changing the specific starting torque, it is possible to obtain a data set of instantaneous starting current values under all starting conditions and create a starting current map.

  In the invention according to claim 4, the predetermined operation control system that the operation control means follows is a maximum torque / current control system. Therefore, when starting the three-phase AC motor, the start control means calculates a control output signal according to a control method that satisfies the minimum start current condition instead of the maximum torque / current control method, and sends it to the inverter. The concentration of the starting current on one phase is alleviated, and the maximum value of the instantaneous values of the three-phase starting current is reduced.

  In the invention of the method according to claim 5, in place of the predetermined operation control method, the three-phase AC motor is controlled to start by a control method that satisfies the minimum starting current condition that minimizes the maximum value among the three-phase starting current instantaneous values. To do. Therefore, the concentration of the coil current at the time of starting is reduced in one phase, the maximum value among the instantaneous values of the three-phase starting current is reduced, and there is no possibility that the stator coil, the semiconductor power switch element of the inverter, etc. are damaged. .

It is a whole block diagram explaining the control apparatus of the three-phase alternating current motor of embodiment of this invention. It is a functional block diagram explaining a processing function of an electronic control unit part in a control device of an embodiment. It is a flowchart explaining the control flow of the three-phase alternating current motor using the control apparatus of embodiment. It is a figure explaining the image of the starting current map used with a control flow. It is an example of the torque-current characteristic diagram of a three-phase AC motor. It is a figure explaining the preparation procedure of a starting current map, (1) is a biaxial current value list, (2) is a three-phase starting current instantaneous value list.

  The form for implementing this invention is demonstrated with reference to FIGS. FIG. 1 is an overall configuration diagram illustrating a control device for a three-phase AC motor according to an embodiment of the present invention. As illustrated, the control device 1 of the embodiment controls a three-phase AC motor 91 and an inverter 92, and includes an electronic control device unit 2, a driver unit 3, a rotational position sensor 4, and two current sensors 5U. 5V. In the present invention, the sensors 4, 5 U, and 5 V are also considered as components of the control device 1.

  The three-phase AC motor 91 includes a rotor (not shown) having permanent magnets and a stator having stator coils U, V, and W connected in a star connection. There are no particular restrictions on the number of pole pairs of the permanent magnet, the connection of the coils U, V, and W and the number of poles. In order to energize the coil current to the three-phase AC motor 91, an inverter 92 and a DC power source 93 are arranged. The inverter 92 is controlled by three-phase pulse width control signals U 1, U 2, V 1, V 2, W 1, W 2 output from the driver unit 3 of the control device 1, and the DC voltage DV of the DC power supply 93 is intermittently connected to each coil. Applied to U, V, and W. A known circuit configuration can be used for the inverter 92.

  As position detecting means for detecting the rotational position of the rotor of the three-phase AC motor 91, a rotational position sensor 4 including a resolver 41 and an R / D converter 42 is provided. The resolver 41 detects a magnetic field formed in the permanent magnet on the rotor, and outputs a continuous analog quantity proportional to the magnetic field. The R / D converter 42 converts the output of the resolver 41 into a position signal θ corresponding to a digital electrical angle proportional to the rotational position, and outputs the position signal θ to the electronic control unit 2. In addition, two current sensors 5U and 5V are provided as current detection means for detecting coil currents IU and IV flowing in the U-phase and V-phase stator coils U and V. Further, a required torque TR required for the three-phase AC motor 91 is commanded to the electronic control unit 2 from a host controller (not shown).

  The electronic control unit 2 includes a control logic unit 21, a memory unit 22, an input unit 23, an output unit 24, and the like. The control logic unit 21 has a microcomputer, operates with software, and performs internal calculations on the dq coordinate axes that rotate with the rotor. The memory unit 22 stores a starting current map, which will be described later. The position signal θ, the coil currents IU and IV, and the required torque TR are input to the input unit 23. The output unit 24 outputs three-phase voltage commands u 1, u 2, v 1, v 2, w 1, w 2 to the driver unit 3.

  Next, detailed processing functions inside the electronic control unit 2 will be described with reference to FIG. FIG. 2 is a functional block diagram illustrating processing functions of the electronic control unit 2. The electronic control unit 2 includes functional units such as a rotation speed calculation unit 61, a three-phase / dq axis conversion unit 62, a torque / dq axis current conversion unit 63, a current control calculation unit 64, and a dq axis / three-phase conversion unit 65. It is configured. The electronic control unit 2 also serves as an operation control unit and a start control unit. The processing contents in the torque / dq axis current conversion unit 63 are different between the start control unit 63S and the operation control unit 63D, and the other functional units 61, 62, 64 and 65 perform common processing.

  The rotational speed calculation unit 61 obtains the rotational speed Rps of the rotor by time differentiation (difference) of the position signal θ of the rotational position sensor 4 and sends it to the torque / dq axis current conversion unit 63. First, the three-phase / dq axis converter 62 uses the coil currents IU and IV detected and transmitted by the current sensors 5U and 5V, and calculates the third-phase coil current IW because the current vector sum is zero. . Next, the coil currents IU, IV, IW in the three-phase region are converted into two-axis currents id, iq on the dq coordinate axis rotating together with the rotor by a conversion formula including the position signal θ, and sent to the current control calculation unit 64 To do.

  The torque / dq axis current conversion unit 63 obtains required two-axis currents idR and iqR based on the required torque TR and sends them to the current control calculation unit 64. At this time, if the rotational speed Rps of the rotor does not reach the preset minute rotational speed R0, it is determined that the engine is starting, and if it has reached, it is determined that the engine is operating, and the processing content is selected. At the time of start-up, the start control unit 63S obtains the requested biaxial currents idR and iqR from the start current map according to a control method that satisfies the minimum start current condition. During operation, the operation control unit 63D obtains the requested biaxial currents idR and iqR from the current phase that can maximize the generated torque according to the maximum torque / current control method. The processing contents at the time of start and operation in the torque / dq axis current converter 63 will be described in detail later.

  First, the current control calculation unit 64 obtains current deviations ed and eq by subtracting the biaxial currents id and iq based on the detection from the requested biaxial currents idR and iqR based on the command. Next, voltage instruction amounts vd and vq that are controlled so as to reduce the current deviations ed and eq are obtained on the dq coordinate axis and sent to the dq axis / three-phase conversion unit 65. The dq axis / three-phase conversion unit 65 reversely converts the voltage instruction amounts vd and vq into a three-phase region by a conversion formula including the position signal θ, and converts the three-phase voltage commands u1, u2, v1, v2, w1, w2 Is output to the driver unit 3.

  The driver unit 3 includes a pulse width modulation circuit as a main part, generates pulse width control signals U1 to W2 based on the three-phase voltage commands u1 to w2 commanded from the electronic control unit 2, and sends them to the inverter 92. To do. A known circuit configuration can be used for the driver unit 3.

  Next, the operation and processing contents of the AC motor control device 1 configured as described above according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flowchart for explaining a control flow of the three-phase AC motor using the control device 1 of the embodiment.

  In step S1 in the control flow of FIG. 3, first, a command for the required torque TR is input to the electronic control unit 2. Next, the coil currents IU and IV detected by the current sensors 5U and 5V are input to the electronic control unit 2 in step S2. The electronic control unit 2 automatically calculates the third-phase W-phase coil current IW because the current vector sum is zero. In step S <b> 3, the rotational position θ detected by the rotational position sensor 4 is input to the electronic control unit 2. In step S4, the rotation speed calculation unit 61 calculates the rotation speed Rps. In step 5, the three-phase / dq axis conversion unit 62 converts the three-phase coil currents IU, IV, and IW into biaxial currents id and iq on the dq coordinate axis.

  In the next step S6, the torque / dq-axis current converter 63 compares the rotational speed Rps with the minute rotational speed R0. If the engine is started, the process proceeds to step S7. If the engine is operating, the process proceeds to step S8. In step S7, the requested biaxial currents idR and iqR are obtained from the starting current map by the starting control unit 63S. FIG. 4 is a diagram for explaining an image of the starting current map stored in the memory unit 22 of the electronic control unit 2. As shown in the figure, the starting current map is obtained by mapping the current phase φ and the required biaxial currents idR and iqR that satisfy the starting current minimum condition in a tabular format using the starting torque TR and the rotational position θ as parameters. Therefore, the start control unit 63S can easily select the required biaxial currents idR and iqR that meet the conditions of the start torque (required torque) TR commanded at the start and the detected rotational position θ. Thereafter, the process proceeds to step S9.

  On the other hand, in step S8, the requested biaxial currents idR and iqR are obtained by the operation control unit 63D according to the maximum torque / current control method. FIG. 5 is an example of a torque-current characteristic diagram of the three-phase AC motor 91, and the maximum torque / current control method will be described using this diagram. In the drawing, the horizontal axis indicates the current phase φ (electrical angle) of the coil current with respect to the rotor of the three-phase AC motor 91, and the vertical axis indicates the output torque TQ of the motor 91. Further, the 10 graphs are measured characteristics using the coil current effective value I as a parameter of 50 Arms pitch. This characteristic shows a change in the output torque TQ when the current phase φ is changed while keeping the coil current effective value I constant, and the maximum output torque TQ is obtained at the peak of the mountain-shaped graph. I understand.

  Conversely, as illustrated in FIG. 5, the minimum current effective value Ix and current phase φx that satisfy the required torque TRx can be obtained, and this is the principle of the maximum torque / current control method. The effective current value Ix and the current phase φx obtained in the three-phase region are converted into required biaxial currents idR and iqR on the dq coordinate axis. Then, it merges to step S9.

  In step S9, the current control calculation unit 64 first subtracts the biaxial currents id and iq obtained in step 5 from the requested biaxial currents idR and iqR obtained in step S7 or step S8 to obtain current deviations ed and eq. Is required. Next, voltage instruction amounts vd and vq for controlling the current deviations ed and eq to be small are obtained on the dq coordinate axis. In step 10, the dq axis / three-phase conversion unit 65 reversely converts the voltage instruction amounts vd and vq into the voltage instruction amounts vU, vV and vW in the three-phase region, and further obtains three-phase voltage commands u1 to w2.

  In the final step 11, the driver unit 3 compares the three-phase voltage commands u 1 to w 2 with the internal reference triangular waveform, and generates pulse width control signals U 1 to W 2 that energize the former in a phase that exceeds the latter. , And sent to the inverter 92. Thereby, the inverter 92 is driven, and the DC voltage DV is intermittently applied to the coils U, V, and W.

  The processes from step 1 to step 11 described above are repeated at a predetermined cycle time. When starting the three-phase AC motor 91, since the rotational speed Rps of the rotor is initially zero, the start control unit 63S functions in step S7, and step S8 is not performed. Thereafter, when the rotational speed Rps of the rotor reaches the minute rotational speed R0, the operation control unit 63D functions in step 8 instead of step S7.

  Next, the procedure for creating the starting current map shown in FIG. 4 and used in step S7 will be described with reference to FIG. FIGS. 6A and 6B are diagrams illustrating a procedure for creating a starting current map, where (1) is a two-axis current value list and (2) is a three-phase starting current instantaneous value list. The starting current map is created by a first process of listing a large number of sets of two-axis current values idm and iqm that satisfy the required specific starting torque TRm, and determining the rotational position θn of the rotor and setting the two-axis current values idm and iqm to three. Phase conversion current instantaneous values IUmn, IVmn, IWmn are inversely converted, and a second process for obtaining a specific current phase φmn that minimizes the maximum value Imax among the instantaneous values IUmn, IVmn, IWmn, biaxial current in the specific current phase φmn A third process with values idmn, iqmn as the starting current map data set,

  In the first process, first, in the torque-current characteristic diagram of FIG. 5, a set of current phases φi and effective values Ii of symmetrical three-phase coil currents that satisfy the required starting torque TRm is listed without omission. Next, the set of current phase φi and effective value Ii is converted into biaxial current values idi and iqi on the dq axis, respectively. When the above procedure is performed, a biaxial current value list shown in FIG. 6A is obtained.

  In the next second process, first, the rotational position θn of the rotor is determined, and multiple sets of two-axis current values idi, iqi in the two-axis current value list are inversely converted into three-phase starting current instantaneous values IUi, IVi, IWi. To do. Thereby, a three-phase starting current instantaneous value list shown in FIG. 6B is obtained. Next, the maximum value Imax among the three-phase starting current instantaneous values IUi, IVi, and IWi is obtained for each current phase φi of each stage of the three-phase starting current instantaneous value list. Next, the maximum value Imax of each stage is compared in magnitude to find the minimum stage, and the current phase φi of that stage is set as the specific current phase φmn.

  In the third process, returning to the biaxial current value list of FIG. 6A, the biaxial current values idmn and iqmn in the specific current phase φmn are picked up. Then, as shown in FIG. 4, the specific current phase φmn and the biaxial current values idmn and iqmn are used as a data set of the starting current map at the starting torque TRm and the rotational position θn.

  Thereafter, by changing the rotational position θn of the rotor and repeating Step 2 and Step 3, a starting current map can be created under any rotational position θ condition. Furthermore, by changing the starting torque TRm and repeating Step 1 to Step 3, the starting current map of FIG. 4 corresponding to all starting conditions in which all starting torques TR and rotational positions θ are combined can be created.

  The above procedure eventually lists the combinations of the instantaneous values of the three-phase starting current that satisfy the required starting torque TRm and the rotational position θn of the rotor, and selects the combination that meets the minimum starting current condition. Will be.

  Next, the operation and effect of the control device 1 of the embodiment will be described by taking as an example the case of starting the three-phase AC motor 91 having the characteristics shown in FIG. As an example, let us consider a case where the required torque TR = TA (Nm) is commanded and started while the rotor is stopped at the rotational position θ = 30 °. In a conventional control device that does not include the start control unit 63S, control according to the maximum torque / current control method is performed even during start-up. That is, regardless of the rotational position θ = 30 ° of the rotor, the operating point B that minimizes the effective coil current value I is obtained on the line of output torque TQ = TA (Nm) in FIG. Subsequent processing is performed. The current phase φB at the operating point B is 28 ° and the effective value IB is 250 Arms. The converted three-phase starting current instantaneous values are IUB = −242A, IVB = −190A, IWB = 432A, and the maximum value ImaxB = IWB = 432A.

  On the other hand, according to the start control unit 63S using the start current map obtained in the present embodiment, the start is performed with the current phase φC = 15 ° and the current effective value IC = 266 Arms. The instantaneous values of the three-phase starting currents converted from this are IUC = −398A, IVC = 0A, IWC = 398A, and the maximum value ImaxC == IUC = IWC = 398A. That is, according to the present embodiment, the effective value of the coil current at the moment of starting increases from 250A to 266A, but the maximum value of the instantaneous current value is reduced by 8% from 432A to 398A. Therefore, the concentration of the starting current in one phase is alleviated, the current flowing through the stator coils U, V, W and the semiconductor power switch element of the inverter 92 is reduced, and stress such as heat generation is reduced and there is no possibility of being damaged.

  The ratio of the current instantaneous value reduction effect is 8% in the above example, and this ratio varies depending on the starting torque TRm and the rotational position θn.

  In the present embodiment, the start control unit 63S uses the start current map, so that it is not necessary to perform complicated calculation processing for start control, and the control flow of FIG. 3 can be repeated in a short cycle time. .

1: Control device for three-phase AC motor 2: Electronic control device unit 21: Control logic unit 22: Memory unit 23: Input unit 24: Output unit 61: Rotational speed calculation unit 62: Three-phase / dq axis conversion unit 63: Torque / Dq axis current conversion unit 63S: start control unit 63D: operation control unit 64: current control calculation unit 65: dq axis / three phase conversion unit 3: driver unit 4: rotational position sensor 5U, 5V: current sensor 91: three phase AC motor U, V, W: Stator coil 92: Inverter 93: DC power supply θ: Rotation position Rps: Rotational speed R0: Minute rotational speed IU, IV, IW: Coil current TR: Required torque, Starting torque idR, iqR: dq Requested biaxial current id on coordinate axis, iq: Two-axis current ed on coordinate axis, eq: Current deviation vd, vq: Voltage instruction amount u1, u2, v1, v2, w1, w2: Three-phase voltage commands U1, U2 , V1, V2, W1, W2: Pulse width control signal φ: Current phase TQ: Output torque I: Effective value of coil current

Claims (5)

A control device for a three-phase AC motor that controls an inverter and supplies a coil current to the stator coil of a three-phase AC motor including a rotor having a permanent magnet and a stator having a stator coil,
Position detecting means for detecting the rotational position of the rotor;
Current detection means for detecting the coil current;
Operation control means for calculating a control output signal in accordance with a predetermined operation control method based on the required torque required for the three-phase AC motor and the detected rotational position and the coil current, and sending the control output signal to the inverter;
When starting the three-phase AC motor, based on the required starting torque, the detected rotational position and the coil current, the maximum value among the instantaneous values of the three-phase starting current instead of the predetermined operation control method Starting control means for calculating the control output signal and sending it to the inverter according to a control method that satisfies the minimum starting current condition;
A control device for a three-phase AC motor, comprising:   2. The start control unit according to claim 1, wherein the start control means holds in advance a start current map that uses the start torque and the rotational position as parameters for the start current instantaneous value data set that satisfies the start current minimum condition. A control device for a three-phase AC motor, wherein the control output signal is calculated using a map.   3. The operation control unit and the start control unit according to claim 2, wherein the operation control unit and the start control unit perform calculation using a dq coordinate axis based on a direction of the permanent magnet on the rotor, and the start current map first satisfies a specific start torque. A large number of sets of relations between current phases and effective values of symmetrical three-phase coil currents are obtained, the current phases and effective values are converted into biaxial current values on the dq coordinate axis, and then the rotor is moved to a specific rotational position. Under certain conditions, the two-axis current value is inversely converted to the current phase of the three-phase coil current and the instantaneous value of the starting current, and the current phase that minimizes the maximum value of the three-phase instantaneous current values of the three phases is defined as the specific current phase And finally, a three-phase intersection is created by a procedure in which the two-axis current value in the specific current phase is used as the data set of the specific starting torque and the instantaneous value of the starting current at the specific rotational position. Motor controller.   The predetermined operation control system according to any one of claims 1 to 3, wherein the predetermined operation control system is a maximum torque / current control system for energizing a current phase capable of maximizing a generated torque with respect to the coil current having the same effective value. A control device for a three-phase AC motor. A control method for a three-phase AC motor in which a coil current is supplied by controlling an inverter to the stator coil of a three-phase AC motor including a rotor having a permanent magnet and a stator having a stator coil,
A detection step of detecting a rotational position of the rotor and the coil current;
An operation control step of calculating a control output signal in accordance with a predetermined operation control method based on the required torque required for the three-phase AC motor, the detected rotational position and the coil current, and sending the control output signal to the inverter;
When starting the three-phase AC motor, based on the required starting torque, the detected rotational position and the coil current, the maximum value among the instantaneous values of the three-phase starting current instead of the predetermined operation control method Starting control step of calculating the control output signal and sending it to the inverter according to the control method that satisfies the minimum starting current condition;
A control method for a three-phase AC motor, comprising:

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