JP2017108573A - Rotation detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation detection device which can surely detects a rotation exceeding a predetermined angle range.SOLUTION: The rotation detection device detects the presence or absence of the rotation of an electric motor 2. The electric motor 2 comprises a stator 22 having a winding 221, and a rotor 21. The inductance of the winding 221 changes according to the position of the rotor 21. A voltage output unit 1 applies an AC voltage of a higher harmonic to the electric motor 2. A current detection unit 4 detects an AC current flowing through the electric motor 2. A determination unit 32 determines that the electric rotates, if a difference amount of a width from a bottom value of the AC current to a peak value between a minimum value (Ipp_min) and a maximum value (Ipp_max) in a predetermined period is larger than a reference value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotation detection device.

  In Patent Document 1, for example, a method of detecting a lock by controlling an electric motor driving device that drives an electric motor is proposed. More specifically, the first rotation position of the electric motor is detected, and the electric motor drive device is controlled so that the electric motor is stopped at a stop position separated from the first rotation position by a predetermined angle. Thereafter, the second rotational position of the electric motor is detected, and whether or not the electric motor is properly rotated to the stop position is detected to detect the presence or absence of the lock.

Japanese Patent No. 4449290

  If it can be detected that the motor is rotating, it can be determined that the motor is not locked. It is also desired to detect rotation more simply.

  Accordingly, an object of the present invention is to provide a rotation detection device that can easily detect rotation.

  A first aspect of a rotation detection device according to the present invention includes a stator (22) including a winding (221) and a rotor (21), and an inductance (L) of the winding is the value of the rotor. A rotation detection device that detects the presence or absence of rotation of the electric motor (2) that changes depending on the position, a voltage output unit (1) that applies a harmonic AC voltage to the electric motor, and an alternating current that flows through the electric motor And the difference between the minimum value (Ipp_min) and the maximum value (Ipp_max) in a predetermined period of the width (Ipp) from the bottom value to the peak value of the alternating current, A determination unit (32) configured to determine that the electric motor is rotating when larger than a reference value;

  A second aspect of the rotation detection device according to the present invention is the rotation detection device according to the first aspect, wherein the difference amount is a ratio (RI) of the maximum value to the minimum value of the width, The reference value is a ratio (RL) of the maximum value (Lmax1) to the minimum value (Lmin1) of the inductance in a predetermined angle range.

  A third aspect of the rotation detection device according to the present invention is the rotation detection device according to the second aspect, wherein the angular range (A1, A11) is the rotor (21 when the inductance takes a peak value). ) Electrical angle.

  The 4th aspect of the rotation detection apparatus concerning this invention is a rotation detection apparatus concerning a 3rd aspect, Comprising: The said electrical angle is the center of the said angle range (A1).

  A fifth aspect of the rotation detection device according to the present invention is the rotation detection device according to the second aspect, wherein the angle range (A3) is an electrical angle of the rotor when the inductance takes a bottom value. Including.

  A sixth aspect of the rotation detection device according to the present invention is the rotation detection device according to the fifth aspect, wherein the electrical angle is the center of the angular range (A3).

  According to the first aspect of the rotation detection device of the present invention, rotation can be easily detected.

  According to the second aspect of the rotation detection device of the present invention, the reference value can be set according to the angle range.

  According to the third, fifth, and sixth aspects of the rotation detection device according to the present invention, rotation over an angular range can be detected more reliably.

  According to the 4th aspect of the rotation detection apparatus concerning this invention, the rotation over an angle range can be detected most reliably.

It is a figure which shows an example of a rotation detection apparatus roughly. It is a figure which shows roughly an example of an internal structure of a voltage output part. It is a figure which shows typically an example of the locus | trajectory of the electric current in a fixed coordinate. It is a figure which shows an example of an alpha-axis current typically. It is a figure which shows typically an example of the locus | trajectory of the electric current in a fixed coordinate. It is a figure which shows an example of an alpha-axis current typically. It is a figure which shows an example of an inductance typically. It is a figure which shows an example of an inductance typically. It is a figure which shows an example of an inductance typically. It is a flowchart which shows an example of operation | movement of a rotation detection apparatus. It is a figure which shows an example of an inductance typically.

<Configuration>
FIG. 1 is a diagram schematically showing an example of the configuration of the rotation detection device. The rotation detection device includes a voltage output unit 1, a control unit 3, and a current detection unit 4. The voltage output unit 1 outputs an AC voltage to the electric motor 2. The voltage output unit 1 is an inverter, for example. For example, a DC voltage is input to the voltage output unit 1. The voltage output unit 1 converts the input DC voltage into an AC voltage, and outputs the converted AC voltage to the electric motor 2.

  FIG. 2 is a diagram illustrating an example of the internal configuration of the voltage output unit 1. For example, the voltage output unit 1 is a three-phase inverter, and includes U-phase switching elements Sup and Sun, V-phase switching elements Svp and Svn, and W-phase switching elements Swp and Swn. The switching elements Sup, Sun are connected in series between the DC buses LH, LL via the output terminal Pu, and the switching elements Svp, Svn are connected in series between the DC buses LH, LL via the output terminal Pv. The switching elements Swp and Swn are connected in series between the DC buses LH and LL via the output terminal Pw. A DC voltage is applied to the DC buses LH and LL.

  When the switching elements Sup, Svp, Swp, Sun, Svn, Swn are appropriately controlled by the control unit 3, the voltage output unit 1 converts a DC voltage into, for example, a three-phase AC voltage, and outputs the three-phase AC voltage. Output from the ends Pu, Pv, Pw.

  The electric motor 2 includes a rotor 21 and a stator 22. The stator 22 has a winding 221. In the illustration of FIG. 1, a three-phase winding 221 is provided. That is, a three-phase electric motor 2 is shown. In the illustration of FIG. 1, one end of each phase winding 221 is connected to the output ends Pu, Pv, Pw, and the other ends are connected to each other. When a three-phase AC voltage is applied to the winding 221, a three-phase AC current flows, and the three-phase winding 221 applies a rotating magnetic field to the rotor 21.

  The rotor 21 has a permanent magnet, and the permanent magnet supplies a field magnetic flux to the stator 22. The rotor 21 rotates according to the rotating magnetic field applied from the stator 22. The electric motor 2 drives, for example, a compressor or a fan.

  Further, the electric motor 2 may rotate for a cause other than the rotating magnetic field from the stator 22. For example, when the external force is generated in the electric motor 2 in a state where the stator 22 does not apply the rotating magnetic field, the electric motor 2 may rotate. For example, when the electric motor 2 drives the fan, the electric motor 2 may be rotated by receiving external force from the fan due to wind. Alternatively, when the electric motor 2 drives the compressor, the electric motor 2 may rotate by receiving an external force from the compressor due to a differential pressure between the suction side low pressure and the discharge side high pressure.

  Since such rotation is not based on the output voltage of the voltage output unit 1, it is necessary to detect this rotation in order to know this rotation. The rotation detection device detects this rotation as will be described later.

  The electric motor 2 is, for example, a magnet-embedded electric motor and has reverse saliency. That is, the inductance of the winding 221 changes according to the rotational position of the rotor 21. Specifically, the q-axis component of the inductance (hereinafter also referred to as q-axis inductance) is larger than the d-axis component (hereinafter also referred to as d-axis inductance). The d-axis and the q-axis here are axes constituting a dq rotation coordinate system that rotates in accordance with the rotation of the rotor 21, and are orthogonal to each other in electrical angle. For example, the d axis is set in phase with the field magnetic flux. The q axis may advance by 90 degrees with respect to the d axis. As will be described later, this rotation detection device detects the rotation of the electric motor 2 due to an external force by utilizing the fact that the inductance changes according to the rotation position of the rotor 21.

  The current detection unit 4 detects an alternating current flowing through the winding 221. In the example of FIG. 1, three current detection units 4 are provided, and AC currents iu, iv, and iw flowing through the windings 221 are detected. Ideally, since the sum of the three-phase alternating currents iu, iv, and iw is zero, the two-phase alternating current may be detected, and the remaining one-phase alternating current may be calculated based on these. Further, a direct current flowing through the voltage output unit 1 may be detected, and this direct current may be detected as an alternating current based on the switching pattern of the voltage output unit 1. This detection method is also called a single shunt method.

  The control unit 3 includes an output control unit 31, a determination unit 32, and a calculation unit 33. Here, the control unit 3 includes a microcomputer and a storage device. The microcomputer executes each processing step (in other words, a procedure) described in the program. The storage device is composed of one or more of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), a rewritable nonvolatile memory (EPROM (Erasable Programmable ROM), etc.), and a hard disk device, for example. Is possible. The storage device stores various information, data, and the like, stores a program executed by the microcomputer, and provides a work area for executing the program. It can be understood that the microcomputer functions as various means corresponding to each processing step described in the program, or can realize that various functions corresponding to each processing step are realized. Further, the control unit 3 is not limited to this, and various procedures executed by the control unit 3 or various means or various functions implemented may be realized by hardware.

  The output control unit 31 controls the output voltage of the voltage output unit 1. For example, the output control unit 31 outputs switching signals to the switching elements Sup, Svp, Swp, Sun, Svn, and Swn, respectively, and controls the amplitude and frequency of the AC voltage output from the voltage output unit 1. Although the generation of such a switching signal is known, it can be generated as follows, for example. That is, a voltage command value for an AC voltage output from the voltage output unit 1 is generated as a sine wave, for example, and a switching signal is generated based on a comparison between the voltage command value and a triangular wave.

  The calculation unit 33 receives AC currents iu, iv, iw detected by the current detection unit 4. The calculation unit 33 performs a calculation that will be described in detail later based on the alternating currents iu, iv, and iw, and outputs the calculation result to the determination unit 32.

  As will be described in detail later, the determination unit 32 determines whether or not the electric motor 2 is rotated by an external force based on the calculation result from the calculation unit 33.

<Rotation detection>
The output control unit 31 causes the voltage output unit 1 to output a harmonic AC voltage. The harmonic AC voltage here refers to an AC voltage having a frequency that is high enough to prevent the stationary motor 2 from rotating. However, even in a state where such harmonic AC voltage is output, the electric motor 2 can be rotated by an external force.

  A harmonic alternating current flows through the winding 221 by the harmonic alternating voltage. FIG. 3 shows a schematic example of the current in a fixed coordinate system. The fixed coordinate system of FIG. 3 is configured by an α axis and a β axis that are orthogonal to each other in electrical angle. The fixed coordinate system is, for example, coordinates fixed to the stator 22, and the α axis is, for example, an axis set in phase with the magnetic flux generated by the U-phase winding 221.

  In the example of FIG. 3, a current trajectory is shown. FIG. 3 shows the current when the electric motor 2 is stationary, and the locus thereof is an ellipse. In the ellipse, the long axis indicates the rotational position of the rotor 21. Specifically, at the electrical angle, the rotor 21 is stationary so that the pole center (that is, the d axis) of the permanent magnet of the rotor 21 overlaps the long axis of the ellipse.

  When the electric motor 2 is stationary, the width Ipp from the bottom value to the peak value of the α-axis component of the current (hereinafter also referred to as α-axis current) is substantially constant. FIG. 4 schematically shows an example of the α-axis current. As shown in FIG. 4, the α-axis current changes in a sine wave shape with the passage of time, and its width Ipp is substantially constant.

  FIG. 5 shows a schematic example of a current when the electric motor 2 is rotating in a fixed coordinate system. If the electric motor 2 is rotating, the locus of current forms a plurality of types of ellipses having different major axis directions. Therefore, the width of the α-axis current varies between the minimum value Ipp_min and the maximum value Ipp_max. FIG. 6 schematically shows an example of the α-axis current. As shown in FIG. 6, the width of the α-axis current varies between the minimum value Ipp_min and the maximum value Ipp_max.

  The same applies to the β-axis current. That is, when the electric motor 2 is not rotating, the width of the β-axis current is substantially constant, and when the electric motor 2 is rotating, the width of the β-axis current varies with time. Hereinafter, the α-axis current will be described as a representative.

  As described above, the width of the α-axis current varies between the minimum value Ipp_min and the maximum value Ipp_max. Therefore, when the difference between the minimum value Ipp_min and the maximum value Ipp_max is larger than the reference value, it is determined that the electric motor 2 is rotating. As the difference amount, for example, a ratio RI of the maximum value Ipp_max to the minimum value Ipp_min can be employed.

  Next, each configuration for performing the above-described operation will be described. The calculation unit 33 performs known coordinate transformation on the detected alternating currents iu, iv, and iw to calculate an α-axis current. The calculating unit 33 calculates a maximum value Ipp_max and a minimum value Ipp_min of the width Ipp of the α-axis current in a predetermined period, and calculates the ratio RI based on these values. The calculation unit 33 outputs the calculated ratio RI to the determination unit 32.

  The determination unit 32 determines whether or not the ratio RI is larger than a reference value. This reference value is set in advance and stored in the storage unit, for example. Then, the determination unit 32 determines that the electric motor 2 is rotating when it is determined that the ratio RI is larger than the reference value.

  According to this, the rotation of the electric motor 2 can be easily detected based on the ratio RI. For example, unlike the present embodiment, it is also conceivable to detect the major axis of the current locus, detect the rotational position, and detect the rotation of the electric motor 2 based on the temporal change of the rotational position. However, when the electric motor 2 is rotating, the higher the rotational speed, the more difficult the elliptical current trajectory can be obtained, making it difficult to calculate the long axis. On the other hand, in the present embodiment, since the minimum value Ipp_min and the maximum value Ipp_max of the current width can be obtained even when the rotation speed increases, the rotation of the electric motor 2 can be easily detected.

<Reference value setting method>
By the way, this width Ipp is simply expressed by the following expression when the inductance of the winding 221 and the amplitude and frequency of the AC voltage output from the voltage output unit 1 are expressed as L, V, and f, respectively.

  The amplitude V and frequency f of the AC voltage are controlled to be constant. If the motor 2 is stationary, it can be considered that the inductance L is constant, so the current width Ipp is constant. This is consistent with FIG. 3 and FIG. On the other hand, when the electric motor 2 is rotating, the inductance L changes according to the rotation angle, so that it can be considered that the AC current width Ipp also changes over time.

  Therefore, based on the minimum value Ipp_min of the AC current width Ipp and the maximum value Ipp_max of the AC current width Ipp, it can be determined whether or not the motor 2 is rotating. Here, a ratio RI of the maximum value Ipp_max to the minimum value Ipp_min is considered. In view of the equation (1), this ratio RI is expressed by the following equation.

  Lmin indicates the inductance L when the width Ipp is equal to the maximum value Ipp_max, and Lmax indicates the inductance L when the width Ipp is equal to the minimum value Ipp_min. Therefore, a ratio RL of the maximum value Lmax to the minimum value Lmin of the inductance L will be considered as a reference value to be compared with the ratio RL.

  FIG. 7 is a diagram schematically showing an example of the inductance L. In FIG. In the example of FIG. 7, the fluctuation of the inductance L with respect to the electrical angle is shown. The inductance L varies along a sine wave, and one period is 180 degrees in electrical angle. In the illustration of FIG. 7, the inductance L when the electric motor 2 has reverse saliency is shown, and the q-axis inductance Lq is larger than the d-axis inductance Ld. The q-axis inductance Lq is the maximum value (peak value) of the sine wave, and the d-axis inductance Ld is the minimum value (bottom value) of the sine wave. The maximum value of the sine wave is also called the peak value.

  By the way, the maximum value Lmax of the inductance L when the electric motor 2 is rotated at the electrical angle with the angular width θth varies depending on the rotated angle range. In the illustration of FIG. 7, angular ranges A1 and A2 are shown. The angle range A1 is an angle range centered on an electrical angle when the inductance L takes a maximum value (peak value), and has an angular width θth of about 40 degrees, for example.

  For example, if the electric motor 2 rotates over the angle range A1, the inductance L changes from the minimum value Lmin1 to the maximum value Lmax1 in the angle range A1 with the rotation. According to the change of the inductance L, the width Ipp of the α-axis current also varies (see formula (1)). Therefore, the ratio RI in this rotation is represented by (Lmax1 / Lmin1).

  Although the angle width of the angle range A2 is the same as the angle width θth of the angle range A1, the angle range A2 does not overlap the angle range A1 in the illustration of FIG. The angle range A2 is, for example, a range in which the inductance L increases monotonously with an increase in electrical angle. When the electric motor 2 rotates over the angular range A2, the inductance L changes from the minimum value Lmin2 to the maximum value Lmax2 of the inductance L in the angular range A2 with the rotation. Therefore, the ratio RI in this rotation is represented by (Lmax2 / Lmin2). Hereinafter, the ratio of the inductance L in the angle range to the maximum value Lmax with respect to the minimum value Lmin is referred to as a ratio RL. From equation (2), the ratio RI is equal to the ratio RL.

  FIG. 7 shows the maximum value Lmax1 (= q-axis inductance Lq) and minimum value Lmin1 in the angle range A1, and the maximum value Lmax2 and minimum value Lmin2 in the angle range A2. As can be understood intuitively from FIG. 7 or from the following description, the ratio RL (= Lmax1 / Lmin1) in the angle range A1 is smaller than the ratio RL (= Lmax2 / Lmin2) in the angle range A2.

  As described above, it can be seen that even if the angular width θth is constant, the ratio RL is not constant and changes according to the angular range. That is, even if the electric motor 2 rotates by a certain angular width θth, the ratio RL at that time changes depending on from which rotational position the electric motor 2 has rotated.

  However, in the case of detecting rotation over approximately the angular width θth, the ratio RL in an arbitrary angular range having the angular width θth may be adopted as the reference value. That is, when the ratio RI of the current flowing through the electric motor 2 is larger than this reference value, the electric motor 2 is considered to rotate over the angular width θth. According to this, the reference value can be set according to the angular width. That is, a guideline for setting a reference value is shown.

  On the other hand, in order to more reliably detect the rotation over the angular width θth, it is desirable to employ a smaller value as the ratio RL in the angular range having the angular width θth. For example, the minimum value of the ratio RL is adopted as the reference value. If the motor 2 rotates over the angular width θth, the ratio RI (= RL) calculated at that time is always theoretically greater than the minimum value regardless of the position from which the motor 2 rotates. Therefore, when the ratio RI is larger than the reference value, it can be determined that the electric motor 2 is theoretically rotating at least over the angular width θth. Therefore, the minimum value of the ratio RL when the electric motor 2 rotates by the angular width θth is obtained.

  In conclusion, the minimum value of the ratio RL when the motor 2 rotates by the angle width θth is the ratio RL (= Lmax1 / Lmin1) in the angle range A1. In order to explain this, the angle ranges other than the angle range A1 are roughly divided into the following three types of angle ranges A11, A2 and A3. The angle widths of the angle ranges A11, A2, A3 are the same as the angle range θth as in the angle range A1. The angle range A11 includes a peak value of the inductance L (= q-axis inductance Lq), but is a range different from the angle range A1 (see FIG. 8). The angle range A2 is a range in which the inductance L changes monotonously with respect to the electrical angle (see FIG. 7). The angle range A3 is a range including the minimum value (bottom value) of the inductance L (see FIG. 9). However, in FIG. 9, since the electrical angle from 0 degree to 180 degrees is shown, the angle range A3 is shown divided into two. If the ratio RL in the angle range A1 is smaller than the ratio RL in the angle ranges A11, A2 and A3, the ratio RL in the angle range A1 is minimized.

  First, the magnitude of the ratio RL in the angle range A2 and the ratio RL in the angle range A1 will be described. In the angle range A2, the inductance L changes monotonously, whereas in the angle range A1, the inductance L has a convex shape. Moreover, since the inductance L exhibits a sine wave, the difference between the maximum value Lmax1 and the minimum value Lmin1 in the angle range A1 is small and the maximum value Lmax2 in the angle range A2 is small. The difference from the minimum value Lmin2 is large. Therefore, the ratio RL in the angle range A1 is smaller than the ratio RL in the angle range A2.

  Next, the magnitude of the ratio RL in the angle range A11 and the ratio RL in the angle range A1 will be described. In the illustration of FIG. 8, an example of the angle ranges A1 and A11 is shown. The maximum value Lmax11 of the inductance L in the angle range A11 is the peak value of the inductance L (= q-axis inductance Lq), similar to the maximum value Lmax1 of the inductance L in the angle range A1. On the other hand, the minimum value Lmin11 of the inductance L in the angle range A11 is smaller than the minimum value Lmin1 of the inductance L in the angle range A1. This is because the sine wave takes a waveform that is symmetrical with respect to the peak value. Therefore, the minimum value Lmin11 in the angle range A11 where the peak value is not located in the center is smaller than the minimum value Lmin1 in the angle range A1 where the peak value is located in the center. Since the maximum values Lmax1 and Lmax11 are the same and the minimum value Lmin11 is smaller than the minimum value Lmin1, the ratio RL in the angle range A1 is smaller than the ratio RL in the angle range A11.

  Next, the magnitude of the ratio RL in the angle range A3 and the ratio RL in the angle range A1 will be described. The ratio RL in the angle range A3 is minimum when the electrical angle when the inductance L takes the bottom value is located at the center of the angle range A3. Therefore, the angle range A3 where the bottom value of the inductance L is located at the center is considered here. In the illustration of FIG. 9, an example of the angle ranges A1 and A3 is shown.

  The ratio RL in the angle range A3 is expressed by (Lmin3 / Lmax3) using the maximum value Lmax3 and the minimum value Lmin3 (= q-axis inductance Lq) of the angle range A3. The difference ΔL between the maximum value Lmax1 and the minimum value Lmin1 of the inductance L in the angle range A1 is equal to the difference ΔL between the maximum value Lmax3 and the minimum value Lmin3 of the inductance L in the angle range A3. On the other hand, the minimum value Lmin1 of the inductance L in the angle range A1 is larger than the minimum value Lmin3 of the inductance L in the angle range A3. Therefore, the following formula is derived.

  As can be understood from the equation (3), the ratio RL in the angle range A1 is smaller than the ratio RL in the angle range A3.

  As described above, it can be seen that the ratio RL in the angle range A1 is smaller than all of the ratios RL in the angle ranges A11, A2, and A3, and the ratio RL is minimum in the angle range A1.

  Therefore, when the ratio RI of the current flowing through the motor 2 is larger than the minimum value of the ratio RL (ratio RL in the angle range A1), it is determined that the motor 2 is rotating at least in the electrical angle by the angular width θth. can do.

  Incidentally, the inductance L is a value obtained by adding a constant value (Lq + Ld) / 2 to a cosine wave having an amplitude (Lq−Ld) / 2 and one cycle of 180 degrees. Therefore, the minimum value of the ratio RL (the ratio RL in the angle range A1) is expressed as follows. However, the angular width θth is 180 degrees or less.

  FIG. 10 is a flowchart illustrating an example of the operation of the rotation detection device. This series of operations is started in a state where the voltage output unit 1 is not driving the electric motor 2, that is, in a state where an AC voltage for rotating the electric motor 2 is not output. First, in step ST1, the output control unit 31 controls the voltage output unit 1 to cause the voltage output unit 1 to output a harmonic AC voltage Vh. Next, in step ST <b> 2, the current detection unit 4 detects the alternating currents iu, iv, iw flowing through the electric motor 2. The detected alternating currents iu, iv, iw are input to the calculation unit 33. Next, in step ST3, the calculation unit 33 performs known coordinate transformation on the alternating currents iu, iv, iw to calculate an α-axis current. The calculating unit 33 calculates a maximum value Ipp_max and a minimum value Ipp_min of the width Ipp of the α-axis current in a predetermined period, and calculates a ratio RI (= Ipp_max / Ipp_min) as a first ratio based on these values. Next, in step ST4, the determination unit 32 determines whether or not the ratio RI is larger than a second ratio that is a predetermined threshold value. This threshold value is a ratio RL in the angle range A1, and is set in advance and stored in a storage unit or the like, for example.

  If it is determined that the ratio RI is greater than the threshold value, the determination unit 32 determines that the electric motor 2 is rotating in step ST5. When it is determined that the ratio RI is equal to or less than the threshold value, the determination unit 32 determines that the electric motor 2 is stationary in step ST6.

  As described above, according to the present rotation detection device, rotation exceeding the angular width θth can be detected more reliably.

  In the above example, the ratio RL in the angle range A1 is adopted as the reference value, but other angle ranges may be adopted. For example, as can be understood from the above description, the ratio RL in the angle range A11 including the electrical angle when the inductance L takes a peak value is smaller than the ratio RL in the angle range A2. Therefore, if the ratio RL in the angle range A11 is adopted as the reference value, the rotation over the angular width θth can be detected more reliably than in the case where the ratio RL in the angle range A2 is adopted as the reference value.

  Similarly, the ratio RL in the angle range A3 including the electrical angle when the inductance L takes the bottom value is smaller than the ratio RL in the angle range A2. Therefore, if the ratio RL in the angle range A3 is adopted as the reference value, the rotation over the angular width θth can be detected more reliably than in the case where the ratio RL in the angle range A2 is adopted as the reference value.

  The ratio RL in the angle range A3 including the electrical angle at the center when the inductance L takes the bottom value (hereinafter referred to as the angle range A31) is the angle range A3 including the electrical angle other than the center (hereinafter referred to as the angle range). Smaller than the ratio RL in (also referred to as A32). Therefore, if the ratio RL in the angle range A31 is adopted as the reference value, the rotation over the angular width θth can be detected more reliably than in the case where the ratio RL in the angle range A32 is adopted as the reference value.

  In the above example, the reverse saliency motor 2 is described, but the same applies to the saliency motor 2. The rotor 21 of the saliency electric motor 2 need not have a permanent magnet. In the saliency electric motor 2, the rotor 21 has a salient pole structure. The d axis is set to an axis along the salient pole direction of the rotor 21, for example.

  FIG. 11 schematically shows an example of the inductance L for the saliency electric motor 2. In the saliency, as shown in FIG. 11, the d-axis inductance Ld is larger than the q-axis inductance Lq. Even in this case, the above-described concept can be adopted. That is, when the current ratio RI is larger than the minimum value of the ratio RL, it can be determined that the electric motor 2 has rotated at least by the angular width θth. The minimum value of the ratio RL is the ratio RL in a predetermined angle range A4 with the electrical angle at which the inductance L takes the maximum value (peak value) as the center, as described above. However, in FIG. 11, since the electrical angle from 0 degree to 180 degrees is shown, the angle range A4 is shown divided into two. The minimum value of this ratio RL (ratio RL in angle range A4) can be expressed by the following equation.

  In the above example, the angle width θth is 180 degrees or less. However, when the angle width θth is 180 degrees or more, the maximum value (peak value) and the minimum value of the inductance L are included in the angle range. Both (bottom value) are included. Therefore, in this case, the ratio RL is constant regardless of the angle range. For example, in the motor 2 having the reverse saliency, the ratio RL is represented by (Lq / Ld), and in the saliency, the ratio RL is represented by (Ld / Lq). The ratio RL can also be described as a ratio exceeding 1 out of the ratio between the d-axis inductance Ld and the q-axis inductance Lq.

  In the above-described example, the α-axis current is described as an example, but the ratio RI may be a ratio of the maximum value to the minimum value of the width of the β-axis current. Alternatively, any of U phase, V phase, and W phase currents may be used.

  In the above example, although the ratio RI is employed as the difference amount, a difference (= Ipp_max−Ipp_min) between the maximum value Ipp_max and the minimum value Ipp_min may be employed. Since the amplitude V and the frequency f are known, the reference value can be set as {V / (π · f · Lmin) −V / (π · f · Lmax)} in view of the equation (1). The angle range may be set based on the same idea as described above. That is, although the angle ranges A1, A11, A2, A3 (A31, A32) may be employed, the reference value can be reduced by employing the angle ranges A11, A3 as compared to the case of employing the angle range A2. Therefore, it is easy to detect rotation. If the angle range A31 is employed, the reference value can be made smaller than when the angle range A32 is employed. If the angle range A1 is employed, the reference value can be minimized.

  In addition, the above-described various embodiments can be appropriately modified and omitted as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Voltage output part 2 Electric motor 4 Current detection part 21 Rotor 22 Stator 32 Judgment part 221 Winding

Claims (6)

Presence or absence of rotation of the electric motor (2), which includes a stator (22) including a winding (221) and a rotor (21), and the inductance (L) of the winding varies depending on the position of the rotor. A rotation detecting device for detecting
A voltage output unit (1) for applying a harmonic AC voltage to the electric motor;
A current detector (4) for detecting an alternating current flowing in the motor;
When the difference between the minimum value (Ipp_min) and the maximum value (Ipp_max) in a predetermined period of the width (Ipp) from the bottom value to the peak value of the alternating current is larger than a reference value, the electric motor A rotation detection device comprising: a determination unit (32) that determines that the rotation has occurred. The difference amount is a ratio (RI) of the maximum value to the minimum value of the width,
The rotation detection device according to claim 1, wherein the reference value is a ratio (RL) of a maximum value (Lmax1) to a minimum value (Lmin1) of the inductance in a predetermined angle range.   The rotation detection device according to claim 2, wherein the angle range (A1, A11) includes an electrical angle of the rotor (21) when the inductance takes a peak value.   The rotation detection device according to claim 3, wherein the electrical angle is a center of the angular range (A1).   The rotation detection device according to claim 2, wherein the angle range (A3) includes an electrical angle of the rotor when the inductance takes a bottom value.   The rotation detection device according to claim 5, wherein the electrical angle is a center of the angular range (A3).

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