JP2013198299A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device which can detect the magnetic pole position of a rotor with high accuracy by a simple method, over a wide operation range from a low speed time to a high speed time.SOLUTION: A switching element is operated so that a first switching state in which, when a motor 10 is energized from a first phase to a second phase, the first phase has electricity conducted to the high potential side input terminal of an inverter 12 and the second phase has electricity conducted to the low potential side input terminal of the inverter 12 and a second switching state in which the first phase has electricity conducted to the low potential side input terminal of an inverter 12 and the second phase has electricity conducted to the high potential side input terminal of the inverter 12 are alternately changed, as a voltage is applied to the motor 10. On the basis of detection of a zero-cross timing at which an induction voltage generated at a third phase terminal matches a reference voltage, on condition that it occurred in a period while the first switching state was on, the magnetic pole position of the rotor of the motor 10 is detected.

Description

  The present invention relates to a motor control device that applies a voltage to a three-phase motor having a q-axis inductance larger than a d-axis inductance by operating a switching element of a power conversion circuit.

  As a method of driving a brushless motor without a sensor, a method of applying a rectangular waveform voltage to each phase of the motor based on a zero cross timing at which an induced voltage induced in a stator coil matches a reference voltage is known. . In particular, when controlling the rotational speed, torque, and current of a motor, a PWM control method is known in which a rectangular wave voltage is applied by pulse width modulation (PWM).

  As one of the PWM control methods, among the three sets of upper and lower switching elements included in the three-phase power conversion circuit, the third phase upper and lower switching elements are turned off, the second phase lower switching elements are turned on, and the first phase There is a method (non-complementary PWM method) in which a voltage is applied by turning on and off the upper switching element. This method has a problem that it is difficult to detect the magnetic pole position of the rotor at a low speed when the duty ratio is small because the zero cross timing can be detected only during the period when the upper switching element of the first phase is turned on.

  On the other hand, as in Patent Document 1 and Patent Document 2, among the three sets of upper and lower switching elements included in the three-phase power converter circuit, the upper and lower switching elements of the third phase are kept off, The first state where the switching element is turned on and the lower switching element of the second phase is turned on and the second state where the lower switching element of the first phase is turned on and the upper switching element of the second phase is turned on are alternately switched There is a method of applying a voltage (complementary PWM method). In the complementary PWM method, when one of the upper and lower switching elements of each phase is turned on, the other is turned off.

Japanese Patent No. 4513863 JP2011-30385A

  In Patent Document 1, the timing at which the induced voltage appearing at the terminal of the third phase coincides with the reference voltage is defined as zero cross timing. However, Patent Document 1 does not consider changes in winding inductance due to changes in the magnetic pole position of the rotor. In an IPM motor or the like whose q-axis inductance is larger than the d-axis inductance, the inductance changes according to the magnetic pole position of the rotor. For this reason, the induced voltage appearing at the terminal of the third phase fluctuates up and down each time the switching element is switched between the first state and the second state. Therefore, there is a risk of erroneously detecting the magnetic pole position of the rotor.

  On the other hand, in Patent Document 2, the timing at which the difference between the terminal voltage of the third phase in the first state and the terminal voltage of the third phase in the second state becomes zero is defined as zero cross timing. In this detection method, when the voltage duty ratio is 100%, one of the switching states does not exist, and the zero cross timing cannot be detected. Therefore, when the voltage duty ratio is 100%, it is necessary to switch to a method of comparing the third phase voltage with the reference voltage. Even when the voltage duty ratio is close to 100%, the voltage is not stabilized due to so-called ringing, so the third-phase terminal voltage in the first state and the third-phase terminal voltage in the second state It is difficult to detect the timing when the difference becomes zero.

  The present invention has been made in view of the above circumstances. An object of the present invention is to provide a motor control device capable of detecting the magnetic pole position of a rotor with high accuracy by a simple method from a low speed to a high speed.

  In order to solve the above problem, the invention according to claim 1 applies a voltage to the motor by operating a switching element of a power conversion circuit connected to a three-phase motor having a q-axis inductance larger than a d-axis inductance. When the motor is energized from the first phase to the second phase of the motor, the first phase is connected to the high potential side input terminal of the power conversion circuit, and the second phase is connected to the power conversion circuit. A first switching state conducted to the low potential side input terminal, and the first phase conducted to the low potential side input terminal of the power conversion circuit and the second phase conducted to the high potential side input terminal of the power conversion circuit, respectively. Pulse width modulation means for operating the switching element to alternately switch between the second switching state and the second phase of the motor when the first phase is energized to the second phase. Position detecting means for detecting a magnetic pole position of a rotor included in the motor based on detection of a zero cross timing at which an induced voltage generated at a phase terminal matches a reference voltage, and the position detecting means includes the pulse width modulation. The magnetic pole position is detected on condition that the period is switched to the first switching state by means.

  According to the above configuration, the first switching state in which the first phase of the three-phase motor is electrically connected to the high potential side input terminal of the power conversion circuit and the second phase is respectively connected to the low potential side input terminal of the power conversion circuit; The motor is operated by operating the switching element to alternately switch between the second switching state in which the phase is conducted to the low potential side input terminal of the power conversion circuit and the second phase is conducted to the high potential side input terminal of the power conversion circuit. Current from the first phase to the second phase. Then, during the period of the first switching state, the magnetic pole position of the rotor is detected based on detection of zero timing at which the induced voltage generated at the third phase terminal of the motor matches the reference voltage.

  In the case of a motor having saliency, the winding inductance changes as the rotor magnetic pole position changes. Thereby, the induced voltage generated at the terminal of the third phase in the period of the first switching state fluctuates in a direction in which the difference from the reference voltage becomes larger than in the case of the motor having no saliency. On the other hand, the induced voltage generated at the terminal of the third phase in the period of the second switching state fluctuates in a direction in which the difference from the reference voltage becomes smaller than in the case of a motor having no saliency.

  Therefore, the zero-cross timing can be detected with high accuracy in the period of the first switching state in which the difference from the reference voltage is large. Therefore, by detecting the magnetic pole position of the rotor when it is in the period of the first switching state and not detecting the magnetic pole position of the rotor when it is not the period of the first switching state, from low speed rotation to high speed rotation The magnetic pole position of the rotor can be detected with high accuracy by a simple method.

The circuit diagram which shows a motor system. The timing chart which shows transition of a switching operation mode. The circuit diagram which shows a 1st switching state. The circuit diagram which shows a 2nd switching state. The graph which shows the change of an inductance. The figure which shows W phase terminal voltage (saliency-pole ratio = 1). The figure which shows W-phase terminal voltage (saliency-pole ratio> 1). The figure which shows W phase terminal voltage (at the time of low speed rotation). The figure which shows W phase terminal voltage (at the time of high speed rotation). The flowchart which shows the process sequence of sensorless drive control. Linking countermeasure diagram.

  An embodiment in which a motor control device is applied to a fan motor of a vehicle air conditioner will be described with reference to the drawings. First, an overall configuration of a motor system to which the motor control device according to the present embodiment is applied will be described with reference to FIG.

  The motor 10 is a three-phase IPM (Interior Permanent Magnet) motor in which a permanent magnet is embedded in a rotor and a coil is wound around a stator. The three phases of the stator are arranged at a pitch of 0 ° to an electrical angle of 120 ° in the order of the U phase, the V phase, and the W phase. The motor 10 is a sensorless motor that does not include a Hall element that detects the magnetic pole position of the rotor. A motor control device 20 described later detects the magnetic pole position of the rotor based on the zero cross timing of the induced voltage generated in each phase of the coil, and switches the energized phase of the motor 10.

  Each phase of the motor 10 is connected to an inverter 12 (power conversion circuit) that applies a voltage. The inverter 12 is a three-phase inverter, and a serial connection body of switching elements SW1 and SW2, a serial connection body of switching elements SW3 and SW4, and a serial connection body of switching elements SW5 and SW6 are connected in parallel. It is a bridge circuit. The upper arm side switching elements SW1, SW3 and SW5 are connected to the positive side (high potential side input terminal) of the battery 14, and the lower arm side switching elements SW2, SW4 and SW6 are connected to the negative side (low potential) of the battery 14. Side input terminal) and GND. Furthermore, a connection point that connects the switching element SW1 and the switching element SW2 in series, a connection point that connects the switching element SW3 and the switching element SW4 in series, and a connection point that connects the switching element SW5 and the switching element SW6 in series are: Each is connected to the U phase, V phase, and W phase of the motor. In addition, flywheel diodes D1 to D6 are connected in parallel to the switching elements SW1 to SW6, respectively.

  The upper arm side switching elements SW1, SW3, and SW5 are formed of P-channel MOS field effect transistors, and are closed (on) when a negative voltage is applied to each gate electrode from the motor control device 20. . On the other hand, the lower arm side switching elements SW2, SW4, and SW6 are composed of N-channel MOS field effect transistors, and are closed when a positive voltage is applied from the motor control device 20 to each gate electrode. The flywheel diodes D1 to D6 are configured as parasitic diodes of MOS field effect transistors.

  The motor control device 20 includes a position detection unit and a pulse width modulation unit, and operates the switching elements SW1 to SW6 to drive the motor 10 in a rectangular wave. Specifically, the magnetic pole position of the rotor is detected based on the zero cross timing. Then, based on the magnetic pole position of the rotor, the energized phase of the motor 10 is switched to rotate the rotor. Further, the motor control device 20 controls the rotation speed, torque, and current of the motor 10 by controlling the voltage applied to the switching elements SW1 to 6 by PWM. The motor control device 20 is configured by, for example, a dedicated control IC or a microcomputer.

  The zero cross timing used for detecting the magnetic pole position of the rotor is detected as the timing at which the induced voltage matches the reference voltage in the period in which the induced voltage appears in the terminal voltages Vu, Vv, Vw of each phase of the motor 10. Specifically, the terminal voltages Vu, Vv, and Vw of each phase are input to the + input terminals of the comparators 24 to 26, respectively, and the reference voltage is input to the − input terminals of the comparators 24 to 26. The timing at which the outputs of the comparators 24 to 26 are inverted is detected as the zero cross timing. Then, the switching elements SW1 to SW6 are operated so as to switch the energized phase at a timing delayed by a predetermined electrical angle (for example, 30 °) from the zero cross timing. The reference voltage is a voltage obtained by dividing the voltage (power supply voltage) of the battery 14 by the resistors R1 and R2 having the same magnitude. That is, the reference voltage is half the power supply voltage. Therefore, the reference voltage does not vary according to the induced voltage unlike the virtual neutral point voltage that is a voltage obtained by averaging the terminal voltages of the motor 10. The terminal voltages Vu, Vv, and Vw are set to voltages that fall within the power supply voltage range of the comparators 24 to 26 by the resistors Ru, Rv, and Rw, respectively, and are input to the comparators 24 to 26.

  FIGS. 2A to 2F show changes in the operation modes of the switching elements SW1 to SW6, respectively. FIGS. 2G and 2H show the zero-cross timing and the commutation (switching of energized phases) timing, respectively. As shown in the drawing, in one of the three phases of the inverter 12, both the switching elements on the upper arm side and the lower arm side are in an open state (off state). On the other hand, the other two phases are the first switching state in which the upper arm side switching element of one phase and the lower arm side switching element of the other phase are closed, the lower arm side switching element of one phase and the other The second switching state in which the upper arm side switching element of each phase is closed is alternately switched. In this case, when one of the upper and lower switching elements of each phase is closed, the other is opened. Hereinafter, it will be described in detail with reference to FIG. 3 and FIG.

  3 and 4 show a circuit during period A in FIG. In the period A, the motor 10 is energized from the V phase (first phase) to the U phase (second phase). In FIG. 3, SW3 and SW2 are closed, the V phase is on the positive side of the battery 14 (high potential side input terminal of the inverter 12), and the U phase is on the negative side of the battery 14 (low potential side input terminal of the inverter 12). The 1st switching state each conducted is shown. In this case, the V-phase terminal voltage Vv is the voltage VB of the battery 14 (more precisely, a value lower than the voltage drop between the source and drain of the switching element SW3). Further, the U-phase terminal voltage Vu becomes the ground potential GND (more precisely, the value of the voltage drop between the source and the drain of the switching element SW2 is higher than this). Note that the W phase (third phase) of the motor 10 connected to the open SW5 and SW6 is in a high impedance state. The motor control device 20 detects the magnetic pole position of the rotor based on the detection of the zero cross timing at which the induced voltage generated at the W-phase terminal, which is a non-energized phase, matches the reference voltage.

  FIG. 4 shows a case where the first switching state in FIG. 3 is switched to the second switching state in which SW1 and SW4 are closed. In the second switching state, the V phase is conducted to the negative side of the battery 14 (low potential side input terminal of the inverter 12) and the U phase is conducted to the positive side of the battery 14 (high potential side input terminal of the inverter 12). It becomes a state. At the time of this switching, an electromotive force that causes a current to flow from the V-phase to the U-phase is generated after switching the switching state due to the inductance of the coil in the same manner as before switching the switching state. For this reason, a current flows from SW4 to the V phase, and a current flows from the U phase to SW1. In this case, the V-phase terminal voltage Vv becomes the ground potential GND (more precisely, the value of the voltage drop between the source and drain of the switching element SW4 is lower than this). Further, the U-phase terminal voltage Vu is the voltage VB of the battery 14 (more precisely, a value about the amount of voltage drop between the source and drain of the switching element SW1). Note that the W phase is in a high impedance state, as in the first switching state.

  In the period A in FIG. 2, the first switching state in FIG. 3 and the second switching state in FIG. 4 are switched alternately. That is, when the motor 10 is energized from the first phase to the second phase, the first phase is conducted to the high potential side input terminal of the inverter 12 and the second phase is conducted to the low potential side input terminal of the inverter 12. The switching element is alternately switched between the switching state and the second switching state in which the first phase is conducted to the low potential side input terminal of the inverter 12 and the second phase is conducted to the high potential side input terminal of the inverter 12. Controlled by PWM signal. As a result, a voltage corresponding to the PWM signal is applied to the motor 10. In addition, there are 6 patterns of combinations of energized phases, which are switched every 60 ° to make a total of one cycle (electrical angle 360 °).

  Next, the fluctuation of the induced voltage that appears in the non-conduction phase will be described. FIG. 5 shows inductances Lu, Lv, and Lw of each phase of the motor 10 when the rotor rotates 360 degrees in the electrical direction from the U phase to the V phase. As shown in the figure, the inductances Lu, Lv, and Lw of each phase vary depending on the magnetic pole position of the rotor. Here, the direction of the magnetic flux generated by the magnetic poles of the rotor is set as the d axis, and the direction orthogonal to the d axis electrically and magnetically is set as the q axis. Then, in the motor 10 having saliency, the ratio (saliency ratio) Lq / Ld of the d-axis inductance Ld and the q-axis inductance Lq is greater than 1. Therefore, the inductances Lu, Lv, and Lw of each phase of the motor 10 vary according to the magnetic pole position of the rotor. In the case of a motor having no saliency (saliency ratio = 1), the inductances Lu, Lv, and Lw of each phase are constant regardless of the magnetic pole position of the rotor.

  FIG. 6 shows the induced voltage that appears at the terminal of the W phase (third phase) when the U phase (second phase) is energized from the V phase (first phase) of the motor having no saliency. In this case, the duty ratio in the first switching state is 55%, the duty ratio in the second switching state is 45%, the first switching state and the second switching state are alternately switched, and the current is supplied from the V phase to the U phase. Yes. As shown in the drawing, the induced voltage during the period in which the first switching state is switched and the induced voltage during the period in which the second switching state is switched are on the same curve. In other words, there is no change in the induced voltage between the period in which the first switching state is switched and the period in which the second switching state is switched.

  On the other hand, FIG. 7 shows the induced voltage that appears at the W-phase (third phase) terminal when the motor 10 having saliency is energized from the V-phase (first phase) to the U-phase (second phase). A broken line is an induced voltage when the salient pole ratio = 1. As shown in FIG. 5, Lu <Lv when the rotor position is 0 ° to 60 °, and Lu> Lv when the rotor position is 60 ° to 120 °. Also in this case, similarly to FIG. 6, the duty ratio in the first switching state is 55%, the duty ratio in the second switching state is 45%, and the first switching state and the second switching state are alternately switched to obtain the V phase. To the U phase.

  As shown in the drawing, the amplitude of the induced voltage during the period of switching to the first switching state has a larger amplitude than the induced voltage when the salient pole ratio = 1. That is, as compared with the case where the salient pole ratio = 1, the difference from the reference voltage increases. In contrast, the amplitude of the induced voltage during the period of switching to the second switching state is smaller than the induced voltage in the case where the salient pole ratio = 1. That is, the difference from the reference voltage is smaller than that in the case where the salient pole ratio = 1. In the first switching state, an induced voltage due to inductance Lv (first phase inductance) appears, and in the second switching state, an induced voltage due to inductance Lu (second phase inductance) appears. Therefore, in the case of a motor having saliency, the induced voltage varies each time the first switching state and the second switching state are switched.

  Further, the fluctuation of the induced voltage will be described in detail when the motor 10 rotates at a low speed and when the motor 10 rotates at a high speed. FIG. 8 shows the induced voltage that appears at the W-phase (third phase) terminal when the rotor of the motor 10 rotates at a low speed (1000 rpm). A curve with a large amplitude (solid line) is an induced voltage when current is supplied from the V phase (first phase) to the U phase (second phase) in the first switching state. A curve with a small amplitude (dashed line) is an induced voltage when a current is supplied from the V phase (first phase) to the U phase (second phase) in the second switching state. A broken line is an induced voltage when the salient pole ratio = 1.

  As shown in the figure, in the first switching state, the zero cross timing that matches the reference voltage is detected only when the position of the rotor is 60 °. However, in the second switching state, the zero cross timing is detected in addition to when the rotor position is 60 °. During low speed rotation, the induced voltage generated in the non-energized phase is small. In the second switching state, the difference between the induced voltage generated in the non-conduction phase and the reference voltage is particularly small. Therefore, the induced voltage and the reference voltage may coincide with each other at a timing other than the original zero cross timing. Therefore, if the magnetic pole position of the rotor is detected based on the detection of the zero cross timing during the period in which the second switching state is switched, there is a risk of erroneous detection. On the other hand, during the period of switching to the first switching state, the magnetic pole position of the rotor can be accurately detected based on the detection of the zero cross timing. Therefore, the magnetic pole position of the rotor is detected on the condition that the period is switched to the first switching state.

  Further, in FIG. 9, when the rotor of the motor 10 is rotating at a high speed (5000 rpm), the W phase (third phase) is applied when the U phase (second phase) is energized from the V phase (first phase). The induced voltage that appears at the terminals of. During low-speed rotation, the induced voltage generated in the non-energized phase is small, and there is a problem that erroneous detection may occur if the magnetic pole position of the rotor is detected during the period of switching to the second switching state. On the other hand, during high speed rotation, as shown in the figure, the induced voltage generated in the non-energized phase is large. Therefore, even during the period of the second switching state, the difference between the induced voltage and the reference voltage becomes large, and the magnetic pole position of the rotor can be detected with high accuracy. Therefore, at the time of high speed rotation, the magnetic pole position of the rotor is detected even during the period during which it is switched to the second switching state.

  Next, a processing procedure for sensorless drive control of the motor 10 will be described with reference to FIG. In the case of sensorless rectangular wave driving, since no induced voltage is generated at the time of starting, the magnetic pole position of the rotor cannot be detected based on the detection of the zero cross timing. Therefore, the rotor is first forcibly rotated and moved to a specific position.

  First, in S1, the switching elements SW1, SW4, and SW6 are turned on, and current flows from the U phase to the V phase and the W phase. If it does in this way, a south pole will arise in the 0-degree position of a stator, and a north pole will arise in the position which is 180 degrees apart from the south pole. The rotor is forcibly rotated by the magnetic pole generated in the stator. When this is performed once or twice, the rotor moves to a position where the N pole is 0 ° and the S pole is 180 ° corresponding to the magnetic pole position of the stator. In this way, the initial position of the rotor is determined.

  Subsequently, in S2, the switching elements SW3 and SW2 are turned on and energized from the V phase to the U phase. At this time, the W phase is in a high impedance state. If it does in this way, a south pole will arise in the position of the electrical angle 150 degrees of a stator, and a north pole will arise in the position of the electrical angle 330 degrees. Therefore, the rotor starts rotating in the direction from 0 ° to 150 ° (the direction from the U phase to the V phase).

  When the rotor rotates 60 electrical degrees, the induced voltage generated at the W-phase terminal coincides with the reference voltage. Therefore, the magnetic pole position of the rotor is detected as 60 ° at the timing when the induced voltage generated at the W-phase terminal coincides with the reference voltage (S3). Thereby, the initial detection of the magnetic pole position of the rotor is performed. The initial detection of the magnetic pole position of the rotor may be performed using another known method.

  Thereafter, normal sensorless driving is started (S4). Specifically, the energized phase is switched at a timing delayed by an electrical angle of 30 ° from the first detected magnetic pole position of 60 °, and a current flows from the W phase to the U phase. Then, the timing at which the induced voltage appearing in the V phase coincides with the reference voltage is detected as the zero cross timing, and the energized phase is switched at a timing delayed by an electrical angle of 30 °. Thus, the motor 10 is driven by sequentially switching energized phases in the switching operation mode shown in FIG. Here, the magnetic pole position of the rotor is detected on the condition that the period is switched to the first switching state.

  Next, it is determined whether or not the rotational speed of the rotor is faster than a predetermined rotational speed (S5). If the rotational speed of the rotor is equal to or lower than the predetermined rotational speed (N0), the magnetic pole position of the rotor is detected and sensorless driving is performed on the condition that the period is switched to the first switching state.

  On the other hand, when the rotational speed of the rotor is higher than the predetermined rotational speed (YES), the magnetic pole position of the rotor is not changed during the period of switching to the second switching state in addition to the period of switching to the first switching state. Detection is performed (S6).

  As shown in FIG. 11, ringing occurs when switching the switching element on the upper arm side and the switching element on the lower arm side. Therefore, in S4 and S6, when detecting the magnetic pole position, the magnetic pole position is not detected until a predetermined time has elapsed since the switching element was turned on. Thus, the process for controlling the motor 10 to perform sensorless driving is completed.

  The present embodiment described above has the following effects.

  In the case of the motor 10 having saliency, the inductances Lu, Lv, and Lw change as the magnetic pole position of the rotor changes. Thereby, the induced voltage generated at the terminal of the third phase in the period of the first switching state fluctuates in a direction in which the difference from the reference voltage becomes larger than in the case of the motor having no saliency. On the other hand, the induced voltage generated at the terminal of the third phase in the period of the second switching state fluctuates in a direction in which the difference from the reference voltage becomes smaller than in the case of a motor having no saliency.

  Therefore, the zero-cross timing can be detected with high accuracy in the period of the first switching state in which the difference from the reference voltage is large. Therefore, by detecting the magnetic pole position of the rotor when it is in the period of the first switching state and not detecting the magnetic pole position of the rotor when it is not the period of the first switching state, from low speed rotation to high speed rotation The magnetic pole position of the rotor can be detected with high accuracy by a simple method. In addition, since sensorless driving is possible from low speed rotation, noise can be suppressed.

  At the time of low speed rotation, since the induced voltage generated at the terminal of the third phase is small, if the magnetic pole position of the rotor is detected during the period of the second switching state, there is a risk of erroneous detection. However, during high-speed rotation, the induced voltage generated at the third phase terminal is large. Therefore, even in the period of the second switching state, the difference between the induced voltage generated at the third phase terminal and the reference voltage is large. Therefore, at the time of high speed rotation, the zero cross timing is detected with high accuracy even in the period of the second switch state. Therefore, at the time of high speed rotation, the magnetic pole position of the rotor is detected even during the period when the state is switched to the second switch state. Thereby, detection opportunities increase and the detection accuracy of the magnetic pole position of a rotor improves.

  -If the reference voltage is half the power supply voltage, the reference voltage is affected by the induced voltage compared to the case where the virtual neutral point voltage, which is the voltage obtained by averaging the terminal voltages of the motor 10, is used as the reference voltage. Will not fluctuate. Therefore, since the difference between the induced voltage generated at the third phase terminal and the reference voltage can be increased, the detection accuracy of the magnetic pole position of the rotor is improved.

  -Misdetection of zero cross timing can be suppressed by not detecting the magnetic pole position of the rotor during the period when the induced voltage generated at the third phase terminal is unstable due to linking.

  Furthermore, it is not limited to the said embodiment, For example, it can implement as follows.

  -You may make it detect the magnetic pole position of a rotor only in the period switched to the 1st switching state irrespective of the rotational speed of a rotor. When the rotor is rotating at a high speed, the position detection opportunities are reduced as compared with the above embodiment, but the magnetic pole position of the rotor can be detected with high accuracy even if the position detection is performed only during the period when the rotor is switched to the first switching state. .

  Although the position detection accuracy is lower than that in the above embodiment, the reference voltage may be the virtual neutral point voltage of the motor 10.

  ・ Even if the rotational speed of the rotor is higher than the predetermined rotation speed, if the voltage duty ratio is larger than the predetermined value, the magnetic pole position of the rotor is detected only during the period when the switching to the first switching state is performed. It may be. When the voltage duty ratio is close to 100%, the pulse width in the second switching state becomes very narrow. Therefore, since it is difficult to detect the magnetic pole position of the rotor during the second switching state, the position detection may not be performed.

  The motor 10 may employ an inset SPM motor as a motor having a d-axis inductance larger than the q-axis inductance. Further, an SPM motor in which the q-axis inductance is larger than the d-axis inductance due to the magnetic saturation of the stator may be adopted.

  DESCRIPTION OF SYMBOLS 10 ... Motor, 12 ... Inverter, 14 ... Battery, 20 ... Motor control apparatus, 24-26 ... Comparator.

Claims (6)

A motor control device that applies a voltage to the motor by operating the switching elements (SW1 to SW6) of the power conversion circuit (12) connected to the three-phase motor (10) whose q-axis inductance is larger than the d-axis inductance. 20)
When energizing from the first phase to the second phase of the motor, the first phase is conducted to the high potential side input terminal of the power conversion circuit, and the second phase is conducted to the low potential side input terminal of the power conversion circuit. And the second switching state in which the first phase is conducted to the low potential side input terminal of the power conversion circuit and the second phase is conducted to the high potential side input terminal of the power conversion circuit, respectively. Pulse width modulation means for operating the switching element to switch alternately;
When the second phase is energized from the first phase, the magnetic pole position of the rotor included in the motor based on the detection of the zero cross timing at which the induced voltage generated at the third phase terminal of the motor matches the reference voltage And position detecting means for detecting
The motor control device according to claim 1, wherein the position detection means detects the magnetic pole position on condition that the period is switched to the first switching state by the pulse width modulation means.   The position detection means detects the magnetic pole position even when the rotor is rotating faster than a predetermined rotation speed even during a period when the pulse width modulation means is switched to the second switching state. The motor control device according to 1. A motor control device that applies a voltage to the motor by operating the switching elements (SW1 to SW6) of the power conversion circuit (12) connected to the three-phase motor (10) whose q-axis inductance is larger than the d-axis inductance. 20)
When energizing from the first phase to the second phase of the motor, the first phase is conducted to the high potential side input terminal of the power conversion circuit, and the second phase is conducted to the low potential side input terminal of the power conversion circuit. And the second switching state in which the first phase is conducted to the low potential side input terminal of the power conversion circuit and the second phase is conducted to the high potential side input terminal of the power conversion circuit, respectively. Pulse width modulation means for operating the switching element to switch alternately;
When the second phase is energized from the first phase, the magnetic pole position of the rotor included in the motor based on the detection of the zero cross timing at which the induced voltage generated at the third phase terminal of the motor matches the reference voltage And position detecting means for detecting
The motor control device according to claim 1, wherein the position detection means detects the magnetic pole position only during a period when the pulse width modulation means is switched to the first switching state.   The motor control device according to claim 1, wherein the reference voltage is a voltage that is half of a power supply voltage.   5. The motor control device according to claim 1, wherein the position detection unit does not detect the magnetic pole position until a predetermined time elapses immediately after the switching element is turned on.   The motor control device according to claim 1, wherein the motor is an IPM motor in which a permanent magnet is embedded in the rotor.

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