Magnetic Pole Initial Position Detection Device and Magnetic Pole Position Detection Device

Abstract

The present invention provides a direct magnetic pole initial position detection device and a magnetic pole position detection device. The magnetic pole initial position detection device for detecting the magnetic pole initial position of the rotor of a synchronous motor includes: a DC excitation command generation unit that generates a first command for causing a constant excitation current with a fixed current phase to a first phase to flow through the synchronous motor; a torque zero determination unit that determines whether the torque generated on the rotor of the synchronous motor is zero when the excitation current based on the first command flows through the synchronous motor; and a magnetic pole initial position acquisition unit that acquires the magnetic pole initial position of the rotor of the synchronous motor based on the actual position of the rotor near the time point when the torque is determined to be zero by the torque zero determination unit, the number of pole pairs of the synchronous motor, and the excitation phase in the DC excitation based on the first command.

Description

Technical Field

[0001] The present invention relates to a magnetic pole initial position detection device and a magnetic pole position detection device. Background Art

[0002] In a synchronous motor, a dq coordinate control system is used, and a current is caused to flow through an appropriate exciting phase winding according to the magnetic pole position of the rotor, thereby generating an expected torque. There are synchronous motors having a magnetic pole position sensor such as an encoder for detecting the magnetic pole position of the rotor and synchronous motors without a magnetic pole position sensor in synchronous motors.

[0003] Among them, in the case of a synchronous motor without a magnetic pole position sensor, magnetic pole position detection processing is performed each time the power supply of the synchronous motor is turned on (started), and the initial position of the magnetic pole (hereinafter, referred to as "magnetic pole initial position") is detected, and the rotation of the synchronous motor is controlled based on the magnetic pole position with this magnetic pole initial position as a reference. As a detection method of the magnetic pole initial position, for example, there is the following direct current excitation method: a constant excitation current is caused to flow while fixing the current phase on the synchronous motor, and the finally stopped position is set as the magnetic pole initial position.

[0004] For example, a drive circuit for a brushless motor is known, which is characterized by including: an energization unit that energizes a drive coil with an exciting current to cause the stator to generate a rotating magnetic field; a rotor having a permanent magnet that is rotationally driven by the rotating magnetic field; an encoder that outputs two-phase pulse-shaped rotation signals with a phase deviation according to the rotation of the rotor; a rotational speed detection unit that detects the rotational angular velocity of the rotor based on the number of rotation signal pulses per unit time and detects the rotation direction of the rotor based on the rotation signal; a logic operation unit that controls the energization of the drive coil to stop after a fixed time and calculates the initial position of the rotor through the output of the rotational speed detection unit; and a counter that inputs the rotation signal and calculates the rotation amount from the initial position of the rotor to the current position, wherein the logic operation unit determines the current rotor position based on the initial position of the rotor and the rotation amount until the current position (for example, refer to Japanese Patent Laid-Open No. 2-276492).

[0005] For example, a control device for a permanent magnet synchronous motor is known. In the control device for the permanent magnet synchronous motor in a permanent magnet synchronous motor that is controlled based on a variable voltage and a variable frequency output from a power conversion device and a mechanical device driven by the permanent magnet synchronous motor, a braking device that keeps the mechanical device stopped is released. Regardless of the rotational position of the permanent magnet synchronous motor, when the torque generated by the motor when a predetermined armature current flows is substantially balanced with the load torque, the pole phase of the permanent magnet synchronous motor is estimated based on the armature current and the load torque or based on the armature current (for example, refer to Japanese Patent Laid-Open No. 2000-78878).

[0006] For example, an initial pole estimation device for an AC synchronous motor is known. It is provided in an AC synchronous motor control device and is characterized by including: a speed control unit that calculates a command torque (command current) based on a command speed; and a current control unit and a PWM power conversion device that drive the AC synchronous motor according to the command torque (command current). Among them, there are: a speed deviation calculation unit that calculates a speed deviation by subtracting the detected speed from the command speed generated by a command speed pattern generation unit; a speed gain control unit that multiplies the speed deviation by a speed gain to calculate a command torque (command current); a mode interval determination unit that performs a determination process of a mode interval (a first cycle interval and a second cycle interval) based on the command speed; a mode switch that switches to either the first cycle interval or the second cycle interval according to the result of the mode interval determination unit; a data acquisition speed interval determination unit that determines whether the command speed is in a data acquisition speed interval when the first cycle interval is selected; a first command torque calculation unit (first command current calculation unit) that calculates first command torque data (first command current data) based on the command torque (command current) in the determined data acquisition speed interval; a data acquisition speed interval determination unit that determines whether the command speed is in the data acquisition speed interval when the second cycle interval is selected; a second command torque calculation unit (second command current calculation unit) that calculates second command torque data (second command current data) based on the command torque (command current) in the determined data acquisition speed interval; and an estimated initial pole calculation unit that calculates an estimated initial pole position using the information of the first command torque data (first command current data) and the second command torque data (second command current data) (for example, refer to Japanese Patent Laid-Open No. 2001-157482). Summary of the Invention

[0007] In the detection process of the initial position of the magnetic poles in the DC excitation mode, for example, a synchronous motor is DC-excited at magnetic pole 0 degrees, and the rotor of the synchronous motor is waited to stop. Then, the synchronous motor is DC-excited at magnetic pole 90 degrees, and the position after stopping is obtained as the initial position of the magnetic poles. In this way, the time from the start of DC excitation of the synchronous motor to the stop of the rotor of the synchronous motor is very long, and it takes a long time to obtain the initial position of the magnetic poles. In particular, in a synchronous motor such as a synchronous motor with a hydrostatic bearing, where the friction is very small and the acceleration performance is high, it sometimes takes several minutes to obtain the initial position of the magnetic poles. Therefore, the following technology is desired: in the magnetic pole position detection process in the DC excitation mode, the initial position of the magnetic poles of the rotor of the synchronous motor can be obtained in a short time.

[0008] According to one aspect of the present disclosure, an initial magnetic pole position detection device for detecting the initial position of the magnetic poles of the rotor of a synchronous motor includes: a DC excitation command generation unit that generates a first command that causes a constant excitation current with a fixed current phase to flow through the synchronous motor; a torque zero determination unit that determines whether the torque generated on the rotor of the synchronous motor is zero when the excitation current based on the first command flows through the synchronous motor; and an initial magnetic pole position acquisition unit that acquires the initial position of the magnetic poles of the rotor of the synchronous motor based on the actual position of the rotor near the time point when the torque is determined to be zero by the torque zero determination unit, the number of pole pairs of the synchronous motor, and the excitation phase in the DC excitation based on the first command.

[0009] In addition, according to another aspect of the present disclosure, the magnetic pole position detection device includes a magnetic pole position update unit that outputs the magnetic pole position of the rotor of the synchronous motor in which the initial position of the magnetic poles detected by the initial magnetic pole position detection device is initialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The object, features, and advantages of the present invention can be made more clear by describing the following embodiments in association with the drawings. In the drawings:

[0011] Figure 1 is a block diagram showing an initial magnetic pole position detection device according to the first embodiment of the present disclosure.

[0012] Figure 2A and Figure 2B is a diagram illustrating the behavior of the rotor of a synchronous motor when a constant excitation current with a fixed current phase is continuously flowed through the synchronous motor, Figure 2A is a diagram illustrating the time course of the speed and position of the rotor, Figure 2B is an enlarged view in the time axis direction of Figure 2A the diagram.

[0013] Figure 3 This is a diagram showing the relationship between the dq coordinate system related to a synchronous motor and the dq coordinate system related to a motor control device for controlling the synchronous motor.

[0014] Figure 4A and Figure 4B This is a diagram explaining the magnitude of the exciting current that flows to obtain the initial position of the magnetic poles of a synchronous motor with significance.

[0015] Figure 5 This is a diagram showing an example of the relationship between the temperature of a permanent magnet provided in a synchronous motor and the magnetic flux density of the main magnetic flux of the synchronous motor.

[0016] Figure 6 This is a diagram explaining the magnetic pole initial position acquisition process in the first embodiment of the present disclosure, and is a diagram showing an example of the acceleration of the rotor of a synchronous motor, the speed of the rotor of the synchronous motor, and the actual position of the rotor of the synchronous motor.

[0017] Figure 7 This is a flowchart showing the operation process of the magnetic pole initial position detection device according to the first embodiment of the present disclosure.

[0018] Figure 8 This is a block diagram showing a motor control device according to the first embodiment of the present disclosure, which includes a magnetic pole position detection device having a magnetic pole initial position detection device.

[0019] Figure 9 This is a block diagram showing the structure of the magnetic pole initial position detection device according to the second embodiment of the present disclosure.

[0020] Figure 10 This is a flowchart showing an exciting current phase determination process for determining an exciting phase used for magnetic pole initial position detection.

[0021] Figure 11 This is a graph showing the relationship between the phase of the exciting current and the torque in the case of a synchronous motor having no significance.

[0022] Figure 12 This is a diagram for explaining the relationship between the phase of the exciting current and the rotation direction of the rotor. Detailed Embodiment

[0023] Hereinafter, a direct current exciting type magnetic pole initial position detection device and a magnetic pole position detection device according to an embodiment of the present disclosure will be described with reference to the drawings. Throughout the drawings, corresponding structural elements are given common reference numerals. To make understanding easier, the scales of these drawings are appropriately changed. The ways shown in the drawings are examples for implementation and are not limited to the illustrated embodiments.

[0024] First Embodiment

[0025] Figure 1 It is a block diagram showing a magnetic pole initial position detection device according to a first embodiment of the present disclosure.

[0026] As Figure 1 shown, the magnetic pole initial position detection device 1 for detecting the magnetic pole initial position of the rotor of the synchronous motor 2 in the present embodiment includes a DC excitation command generation unit 11, a torque zero determination unit 12, a magnetic pole initial position acquisition unit 13, a rotor actual position acquisition unit 14, and a storage unit 15.

[0027] The DC excitation command generation unit 11 generates a command (hereinafter, also referred to as a first command) for causing a constant excitation current with a fixed current phase (hereinafter, also referred to as a first phase) to flow through the synchronous motor 2. The command generated by the DC excitation command generation unit 11 is sent to the current control unit 33 (see Figure 8 ) within the motor control device 1000 for controlling the drive of the synchronous motor 2. The current control unit 33 within the motor control device 1000 generates a voltage command based on the command received from the DC excitation command generation unit 11 and the current feedback transformed with a fixed current phase, and the power conversion unit 35 applies a voltage to the synchronous motor 2 according to the received voltage command, thereby generating a constant excitation current with a fixed current phase. Using this excitation current as a drive source, the rotor of the synchronous motor 2 vibrates in the rotational direction, and the vibration gradually decays and finally stops.

[0028] When a constant excitation current based on the first command generated by the DC excitation command generation unit 11 flows through the synchronous motor 2, the torque zero determination unit 12 determines whether the torque generated by the rotor of the synchronous motor 2 is zero (0). In addition, since there are multiple time points (timings) when the torque is zero in the rotor vibrating in the rotational direction until the rotor completely stops, there are many opportunities for torque zero determination in the torque zero determination unit 12 until the rotor completely stops. Among the multiple torque zero determination opportunities, the closer the torque zero determination opportunity is to the start time point of the DC excitation command for the synchronous motor 2 generated by the DC excitation command generation unit 11, the shorter the time required to complete the acquisition process of the magnetic pole initial position of the rotor of the synchronous motor 2 by the magnetic pole initial position acquisition unit 13 from the start time point of the DC excitation command for the synchronous motor 2 generated by the DC excitation command generation unit 11. For example, it is most preferable that the torque zero determination unit 12 detects the first generated torque zero after the DC excitation command generation unit 11 starts generating the DC excitation command for the synchronous motor 2 and notifies the magnetic pole initial position acquisition unit 13 of the detection result (i.e., the torque zero determination).

[0029] The magnetic pole initial position acquisition unit 13 acquires the initial magnetic pole position of the rotor of the synchronous motor 2 based on the position of the rotor of the synchronous motor 2 (actual rotor position) near the time point when the torque is determined to be zero by the torque zero determination unit 12, the number of pole pairs of the synchronous motor 2, and the excitation phase in the DC excitation.

[0030] The actual rotor position acquisition unit 14 acquires the position of the rotor of the synchronous motor 2, that is, the actual rotor position, from the sensor 51 provided in the synchronous motor 2.

[0031] The storage unit 15 stores information related to the number of pole pairs of the synchronous motor 2. The storage unit 15 is composed of, for example, a non-volatile memory such as an EEPROM (registered trademark) that can be electrically erased and recorded, or a random access memory such as a DRAM or SRAM that can perform high-speed reading and writing.

[0032] Here, refer to Figures 2A - 2B and Figure 3 to explain the principle of acquiring the initial magnetic pole position of the rotor of the synchronous motor 2 based on the actual rotor position at the time point when the torque generated by the rotor of the synchronous motor 2 is zero or at a time point near it.

[0033] Figure 2A and Figure 2B are diagrams showing the behavior of the rotor of the synchronous motor when the current phase is fixed and a constant excitation current continuously flows through the synchronous motor. Figure 2A is a diagram showing the time course of the speed and position of the rotor. Figure 2B is a diagram that magnifies Figure 2A in the time axis direction. In Figure 2A and Figure 2B , the solid line shows the time course of the actual rotor position of the synchronous motor 2, and the dashed-dotted line shows the speed (rotational angular velocity) of the synchronous motor 2. When the current phase is fixed and a constant excitation current continuously flows through the synchronous motor 2, as shown in Figure 2A and Figure 2B , the rotor of the synchronous motor 2 vibrates in the rotational direction. The vibration of the synchronous motor 2 gradually decays, and the rotor finally stops.

[0034] Figure 3 is a diagram showing the relationship between the dq coordinate system related to the synchronous motor and the dq coordinate system related to the motor control device for controlling the synchronous motor. Let the coordinate axes of the dq coordinate system related to the synchronous motor be d m and q m , and let the coordinate axes of the dq coordinate system related to the motor control device for controlling the synchronous motor be d c and q c . In addition, let the deviation amount of the d-axis between the coordinate systems (that is, the coordinate axis d m and the coordinate axis dc Let the formed angle be θ. In addition, the deviation amount θ is also the deviation amount of the q-axis between the coordinate systems (i.e., the angle formed by the coordinate axis q m and the coordinate axis q c ).

[0035] Let the constant exciting current with the current phase fixed at 0 degrees in the dq coordinate system related to the motor control device be I e . At this time, the exciting current I e is shown as in Equation (1) in the dq coordinate system related to the synchronous motor.

[0036]

[0037] When the number of pole pairs of the synchronous motor 2 is set to pp, the main magnetic flux is set to Φ, the d-phase inductance is set to L d , the q-phase inductance is set to L q , in the synchronous motor with significance, when the exciting current I e flows, the torque T r is shown as in Equation (2).

[0038] T r = pp·{Φ - (L q - L d )·I dm}·I qm

[0039] = pp·{Φ - (L q - L d )·I e ·cosθ}·(-I e ·sinθ)

[0040] …(2)

[0041] In addition, in a non-significant synchronous motor (i.e., a synchronous motor without significance), the d-phase inductance L d is equal to the q-phase inductance L q . Therefore, when the exciting current I e flows in the non-significant synchronous motor, the torque T r is obtained by transforming Equation (2) and shown as in Equation (3).

[0042] T r = pp·Φ·(-I e ·sinθ)…(3)

[0043] When the current phase is fixed and a constant exciting current continuously flows through the synchronous motor, as Figure 2A and Figure 2BAs shown, the rotor of the synchronous motor vibrates in the rotational direction, and the vibration gradually decays and finally stops. When the rotor of the synchronous motor is in the final stop position, the stop position of the rotor matches the excitation phase, and the deviation θ between the coordinate systems becomes zero. While the excitation current continuously flows in the synchronous motor and the rotor vibrates in the rotational direction, the deviation θ changes every moment. Although "sinθ" is included in Equations (2) and (3), "sinθ" becomes zero when the deviation θ is zero, and thus the torque T r becomes zero. In other words, when the torque T r is zero, "sinθ" in Equations (2) and (3) is zero, that is, the deviation θ can become zero. Therefore, when the current phase is fixed and a constant excitation current continuously flows into the synchronous motor, the time point when the detected torque T r becomes zero is detected, and based on the actual position of the rotor at this time point, the initial position of the magnetic pole is obtained.

[0044] However, in the case of a synchronous motor with saliency, depending on the magnitude of the excitation current I e ,"{Φ - (L q - L d )·I e ·cosθ}" in Equation (2) becomes zero when θ is other than zero, that is, the torque Tr shown in Equation (2) may become zero. That is to say, in the case of a synchronous motor with saliency, even when the torque T r is zero, the deviation θ is not necessarily zero. Therefore, when applying this embodiment to a synchronous motor with saliency, it is necessary to flow an excitation current I q - L d )·I e ·cosθ}" is not zero. On the other hand, in the case of a non-salient synchronous motor, Equation (3) shows the deviation θ, so the torque T e becoming zero is not limited to when the deviation θ is zero. Therefore, when applying this embodiment to a non-salient synchronous motor, it is not necessary to set an upper limit value for the constant excitation current I r with a fixed current phase. e Here, refer to

[0045] and Figures 4A - 4B and Figure 5 to describe the magnitude of the excitation current I e that should flow to obtain the initial position of the magnetic pole of a synchronous motor with saliency.

[0046] Figure 4A and Figure 4B are diagrams showing the magnitude of the excitation current flowing to obtain the initial position of the magnetic pole of a synchronous motor with saliency. In Figure 4AIn [diagram], the horizontal axis shows the deviation amount θ, and the vertical axis shows the torque T r . In Figure 4B , the horizontal axis shows the deviation amount θ, and the vertical axis shows the value obtained by dividing the formula for generating torque by the q-phase current. Additionally, in Figure 4A and Figure 4B , the double-dashed line shows the excitation current I e for the case of 30 Arms, the single-dashed line shows the excitation current I e for the case of 60 Arms, and the solid line shows the excitation current I e for the case of 80 Arms. Furthermore, Figure 4A and Figure 4B show that the magnitude of the excitation current I e is always an example.

[0047] In the case where the excitation current I e is 30 Arms and 60 Arms, as Figure 4A shows, the torque T r becomes zero only when the deviation amount θ is zero. In contrast, in the case where the excitation current I e is 80 Arms, not only when the deviation amount θ is zero, but also around "-44 degrees", the torque T r becomes zero. Thus, in the case where the excitation current I e is 80 Arms, the state where the torque T r becomes zero when the deviation amount θ is other than zero is due to a negative region in the value obtained by dividing the formula for generating torque by the q-phase current, as Figure 4B shows. Therefore, when applying this embodiment to a salient synchronous motor, in all cases where the deviation amount θ is other than zero, it is necessary to set the torque T r shown in formula (2) to be positive (i.e., greater than zero) for the excitation current I e . The following is the specific situation.

[0048] When applying "T r >0" and "θ≠0" to formula (2) and rearranging, the inequality (4) is obtained.

[0049] Φ - (L q - L d )·I e ·cosθ>0…(4)

[0050] In the inequality (4), "-1≤cosθ≤1" holds, so the inequality (5) is obtained from the inequality (4).

[0051] Φ - (L q - L d )·I e >0…(5)

[0052] When arranging inequality (5), inequality (6) is obtained.

[0053]

[0054] Therefore, when applying this embodiment to a salient synchronous motor, the constant excitation current I with a fixed current phase e should be set to a magnitude that satisfies inequality (6). In this embodiment, when the synchronous motor for obtaining the initial position of the magnetic pole is a salient synchronous motor, the DC excitation command generation unit 11 generates an excitation current I that is less than the upper limit value "Φ / (L q -L d )" and flows to the synchronous motor 2. e command.

[0055] In addition, the main magnetic flux Φ decreases as the temperature of the permanent magnet provided in the synchronous motor 2 rises. Therefore, the upper limit value of the excitation current I can also be set in consideration of the assumed temperature rise of the permanent magnet during the drive of the salient synchronous motor 2. Here, with reference to e explain the magnitude of the excitation current I that should flow to obtain the initial position of the magnetic pole in consideration of the temperature rise of the permanent magnet of the salient synchronous motor. Figure 5 e magnitude.

[0056] Figure 5 Figure 5 is a diagram showing the relationship between the temperature of the permanent magnet provided in the synchronous motor and the magnetic flux density of the main magnetic flux of the synchronous motor. In Figure 5 , the horizontal axis shows the temperature of the permanent magnet provided in the synchronous motor 2, and the vertical axis shows the ratio of the magnetic flux density when the magnetic flux density is set to 100% at 20°C of the permanent magnet. In addition, The values shown are just examples and can also be other values. For example, when the highest temperature of the permanent magnet assumed during the drive of the salient synchronous motor 2 is 160 degrees, in such a way that even when the permanent magnet is at 160 degrees, the deviation θ is outside zero and torque is generated and is not zero, considering the magnetic flux Φ min (minimum magnetic flux density) at the assumed highest temperature of the permanent magnet of the synchronous motor 2, the excitation current I e is restricted. That is, inequality (7) can be obtained from inequality (6).

[0057]

[0058] Therefore, when applying this embodiment to a salient synchronous motor, considering the assumed temperature rise of the permanent magnet during the drive of the synchronous motor, the constant excitation current I with a fixed current phase can also be​e Set to a magnitude that satisfies inequality (7). In this case, the DC excitation command generation unit 11 generates a command for causing an excitation current I that is less than the upper limit value "Φ min / (L q -L d )" to flow to the synchronous motor 2. e

[0059] Next, refer to Figure 2A and Figure 2B to describe the torque zero determination process of the torque zero determination unit 12.

[0060] As Figure 2A and Figure 2B show, when the current phase is fixed and a constant excitation current continuously flows to the synchronous motor 2, the rotor of the synchronous motor 2 vibrates in the rotational direction. The vibration of the synchronous motor 2 gradually decays, and the rotor finally stops. During the vibration of the rotor of the synchronous motor 2 in the rotational direction, the torque T r becomes zero at the time point when the polarity of the acceleration of the rotor of the synchronous motor 2 changes from positive to negative or from negative to positive. In addition, it is shown that the speed of the synchronous motor 2 is maximum (extreme) at the time point when the polarity of the acceleration of the synchronous motor 2 changes from positive to negative, and the speed of the synchronous motor 2 is minimum (extreme) at the time point when the polarity of the acceleration of the synchronous motor 2 changes from negative to positive. Therefore, in the present embodiment, the torque zero determination unit 12 obtains the acceleration of the synchronous motor 2 (of the rotor), and determines the time point when the polarity of the acceleration of the synchronous motor 2 changes as the time point when the torque is zero. In addition, the torque zero determination unit 12 obtains the speed of the synchronous motor 2 (of the rotor), and determines the time point when the speed of the synchronous motor 2 is maximum or minimum as the time point when the torque is zero. The acceleration of the synchronous motor 2 can be obtained by performing a second-order differentiation on the actual rotor position obtained by the rotor actual position acquisition unit 14. In addition, the speed of the synchronous motor 2 can be obtained by performing a first-order differentiation on the actual rotor position obtained by the rotor actual position acquisition unit 14. The differential calculation process of the actual rotor position can be executed in the torque zero determination unit 12, or can be executed in the rotor actual position acquisition unit 14 or in a further other processing unit.

[0061] Next, refer to Figure 6 to describe the magnetic pole initial position acquisition process of the magnetic pole initial position acquisition unit 13.

[0062] Figure 6 is a diagram for explaining the magnetic pole initial position acquisition process in the embodiment of the present disclosure. In Figure 6 ​In it, an exemplary additional reference numeral 61 is assigned to the acceleration of the rotor of the synchronous motor, an exemplary additional reference numeral 62 is assigned to the speed of the rotor of the synchronous motor, and an exemplary additional reference numeral 63 is assigned to the actual position of the rotor of the synchronous motor.

[0063] The magnetic pole initial position acquisition unit 13 acquires the magnetic pole initial position of the rotor of the synchronous motor 2 based on the actual position of the rotor near the time point when the torque T r is determined to be zero by the torque zero determination unit 12, the number of pole pairs of the synchronous motor 2, and the excitation phase in the DC excitation. In the illustrated example, when the sampling period of the actual position of the rotor acquired by the actual rotor position acquisition unit 14 is set to T s , after the actual rotor position acquisition unit 14 acquires the actual position of the rotor at time 0, it then acquires the actual position of the rotor at time T s . It is considered that the polarity of the acceleration a of the rotor of the synchronous motor 2 changes from positive to negative (i.e., the acceleration a of the rotor is zero-crossing) at time T0 between time 0 and time T s . Let the acceleration of the rotor of the synchronous motor 2 at time 0 be A0, the speed of the rotor be V0, the actual position of the rotor be P0, and the acceleration of the rotor of the synchronous motor 2 at time T s be A1, the speed of the rotor be V1, and the actual position of the rotor be P1. In addition, let the actual position of the rotor at time T0 be P e . In the illustrated example, the value obtained by multiplying the deviation during the period from the actual position P r of the rotor at time T0 when the torque T e is zero to the actual position P1 of the rotor at time T s by the number of pole pairs of the synchronous motor 2 and adding the excitation phase in the DC excitation corresponds to the magnetic pole initial position of the rotor of the synchronous motor 2. That is, in the sampling interval of the actual position of the rotor acquired by the actual rotor position acquisition unit 14, the two sampling time points that delimit the sampling interval including the time point when the torque T r is determined to be zero by the torque zero determination unit 12, namely time 0 and time T s , the time interval contains the time point when the torque T r is determined to be zero. In the present embodiment, in the sampling interval of the actual position of the rotor acquired by the actual rotor position acquisition unit 14, the two sampling time points that delimit the sampling interval including the time point when the torque T r is determined to be zero (in the Figure 6 example, time 0 and time T sAny time point between them is regarded as the "time point when the torque is judged to be zero", and it is expressed as the "vicinity" of the time point when the torque is judged to be zero. That is to say, if the "vicinity of the time point when the torque is judged to be zero" exists in the time interval between two sampling time points that delimit the sampling interval including the time point when the torque T is judged to be zero by the torque zero judgment unit 12, it can also be any time point. Here, the actual position P of the rotor at this time point is calculated. r For the example of the calculation method of the actual position P of the rotor, several examples are given below. e Regarding the actual position P of the rotor e

[0064] In the first method of calculating the actual position P of the rotor e the actual position P of the rotor is calculated as follows. e

[0065] The acceleration a of the rotor of the synchronous motor 2 at time t is shown as in Equation (8).

[0066]

[0067] Therefore, substituting t = T0 and a(T0) = 0 into Equation (8) for the moment T0 when the acceleration of the rotor of the synchronous motor 2 changes from positive to negative, it is shown as in Equation (9).

[0068]

[0069] At this time, the actual position of the rotor also increases monotonically approximately proportionally. Therefore, the torque T r is zero at the time point, that is, the actual position P of the rotor at the time point when the polarity of the acceleration a of the rotor of the synchronous motor 2 changes from positive to negative (that is, the acceleration a of the rotor is at zero crossing) is shown as in Equation (10). e

[0070]

[0071] In the first method of calculating the actual position P of the rotor e the magnetic pole initial position acquisition unit 13 calculates the actual position of the rotor according to Equation (10).

[0072] In the second method of calculating the actual position P of the rotor e the actual position P of the rotor is calculated as follows. e

[0073] In the interval including the time point when the torque T r is judged to be zero by the torque zero judgment unit 12, the change in the rotor speed of the synchronous motor 2 is small. Therefore, when the speed of the rotor of the synchronous motor 2 is regarded as a constant speed V0, the torque T r ​​​​The actual rotor position P at the time point of zero e is shown as in Equation (11).

[0074]

[0075] At the actual rotor position P e in the second method of the calculation process, the magnetic pole initial position acquisition unit 13 calculates the actual rotor position according to Equation (11).

[0076] At the actual rotor position P e in the third method of the calculation process, the actual rotor position P is calculated as follows e .

[0077] The actual rotor position increases monotonically in approximate proportion, so the midpoint of the sampling interval of the actual rotor position is regarded as the torque T r at the time point of zero, the torque T r at the time point of zero, the actual rotor position P e is shown as in Equation (12).

[0078]

[0079] At the actual rotor position P e in the third method of the calculation process, the magnetic pole initial position acquisition unit 13 calculates the actual rotor position according to Equation (12).

[0080] The magnetic pole initial position acquisition unit 13 uses the torque T calculated through the calculation process in any one of the first to third methods r at the time point T0 when the actual rotor position P is zero e , the torque T r after becoming zero until the next sampling time point T s the actual rotor position P1 at this time and the number of pole pairs pp of the synchronous motor 2, and calculates the magnetic pole initial position according to Equation (13).

[0081] θ = pp · (P1 - P e ) + excitation phase...(13)

[0082] At the magnetic pole initial position detected by the magnetic pole initial position detection device 1, the magnetic pole position counter (not shown) is initialized, and thereafter the value obtained by multiplying the increment pulse amount per sampling period (= P n - P n-1 ) by the number of pole pairs is added to the magnetic pole position counter.

[0083] Figure 7 is a flowchart showing the operation process of the magnetic pole initial position detection device according to the embodiment of the present disclosure.

[0084] In step S101, the DC excitation command generation unit 11 generates a first command for causing a constant excitation current with the current phase fixed to a first phase to flow through the synchronous motor 2. The current phase (first phase) is fixed to, for example, 0 degrees. The first command generated by the DC excitation command generation unit 11 is sent to the current control unit in a motor control device (not shown) for controlling the drive of the synchronous motor 2. The current control unit in the motor control device generates a voltage command based on the command received from the DC excitation command generation unit 11 and the current feedback transformed with a fixed current phase, and a power conversion unit (not shown) applies a voltage to the synchronous motor 2 according to the received voltage command, thereby generating a constant excitation current with the current phase fixed.

[0085] In step S102, the magnetic pole initial position detection device 1 determines whether the rotor of the synchronous motor 2 rotates. If it is determined in step S102 that the rotor of the synchronous motor 2 rotates, the process proceeds to step S103, and if it is not determined that the rotor of the synchronous motor 2 rotates, the process proceeds to step S105.

[0086] In step S103, when a constant excitation current based on the command generated by the DC excitation command generation unit 11 flows through the synchronous motor 2, the torque zero determination unit 12 determines whether the torque generated by the rotor of the synchronous motor 2 is zero. For example, the torque zero determination unit 12 determines the time point when the polarity of the acceleration of the synchronous motor 2 changes as the time point when the torque is zero. Additionally, for example, the torque zero determination unit 12 determines the time point when the speed of the synchronous motor 2 is maximum or minimum as the time point when the torque is zero. If it is determined in step S103 that the torque is zero, the process proceeds to step S104, and if it is determined that the torque is not zero, the process returns to step S102.

[0087] In step S104, the magnetic pole initial position acquisition unit 13 acquires the magnetic pole initial position of the rotor of the synchronous motor 2 based on the actual position of the rotor of the synchronous motor 2 near the time point determined by the torque zero determination unit 12 to have zero torque, the number of pole pairs of the synchronous motor 2, and the excitation phase in the DC excitation.

[0088] When it is not determined in step S102 that the rotor of the synchronous motor 2 rotates, in step S105, the DC excitation command generation unit 11 generates the following command: a constant excitation current flows through the synchronous motor 2 with a current phase that is 90 degrees different from the current phase (for example, 0 degrees) set in step S101. Thus, when it is not determined in step S102 that the rotor of the synchronous motor 2 rotates, the reason for deviating the current phase by 90 degrees and flowing the constant excitation current again is that when the current phase set in step S101 is already near the initial position of the rotor poles, even if the excitation current flows, the rotor of the synchronous motor 2 will not perform a vibratory action, so that the initial position of the poles cannot be correctly obtained. Therefore, this situation is avoided.

[0089] In step S106, the pole initial position detection device 1 determines whether the rotor of the synchronous motor 2 rotates. When it is determined in step S106 that the rotor of the synchronous motor 2 rotates, it proceeds to step S103. When it is not determined that the rotor of the synchronous motor 2 rotates, it proceeds to step S107.

[0090] When it is not determined in step S106 that the rotor of the synchronous motor 2 rotates, the rotor of the synchronous motor 2 may be in a certain constrained state such as being fixed by a fastener. Therefore, the pole initial position detection device 1 issues an alarm and stops its operation.

[0091] Figure 8 It is a block diagram of the motor control device 1000 including the pole position detection device 100 having the pole initial position detection device 1, which shows an embodiment of the present disclosure.

[0092] The pole position detection device 100 includes the pole initial position detection device 1 and the pole position update unit 41. The motor control device 1000 includes the pole position detection device 100, the speed control unit 31, the current command generation unit 32, the current control unit 33, the dq three-phase conversion unit 34, the power conversion unit 35, the three-phase dq conversion unit 36, and the speed acquisition unit 37.

[0093] The speed control unit 31 generates a torque command T cmd according to the speed command ω m and the speed ω of the rotor of the synchronous motor 2 acquired by the speed acquisition unit 37 cmd .

[0094] The current command generation unit 32 generates a d-axis current command I cmd and a q-axis current command I m according to the torque command T dc and the speed ω of the rotor of the synchronous motor 2 acquired by the speed acquisition unit 37 qc .

[0095] The three-phase dq conversion unit 36 performs three-phase dq conversion on the three-phase current I output from the power conversion unit 35 according to the magnetic pole position detected by the magnetic pole position detection device 100, and outputs the d-axis current I u 、I v 、I w and outputs the d-axis current I d and the q-axis current I q to the current control unit 33.

[0096] During normal motor control, the current control unit 33 generates a d-axis voltage command V dc and a q-axis voltage command V qc based on the d-axis current command I d and the q-axis current command I q , as well as the d-axis current I dc and the q-axis current I qc . Additionally, during magnetic pole initial position detection, the current control unit 33 generates a d-axis voltage command V d =I e , I q =0) based on the DC excitation command output from the DC excitation command generation unit 11 of the magnetic pole initial position detection device 1, to generate a d-axis voltage command V dc and a q-axis voltage command V qc for allowing a constant excitation current with a fixed current phase to flow.

[0097] The dq three-phase conversion unit 34 performs dq three-phase conversion on the d-axis voltage command V dc and the q-axis voltage command V qc according to the magnetic pole position detected by the magnetic pole position detection device 100, and outputs the three-phase voltage commands V uc 、V vc 、V wc to the power conversion unit 35.

[0098] The power conversion unit 35 is constituted by, for example, an inverter (three-phase inverter) of a full-bridge circuit including semiconductor switching elements, and controls the on and off of the semiconductor switching elements according to the received three-phase voltage commands V uc 、V vc 、V wc and outputs the three-phase current I u 、I v 、I w for driving the synchronous motor 2.

[0099] The pole position updating unit 41 within the pole position detection device 100 initializes the pole position counter at the pole initial position output from the pole initial position detection device 1 (the pole initial position acquisition unit 13 thereof). After the initialization of the pole position counter, the pole position updating unit 41 adds the value obtained by multiplying the increment pulse amount by the number of pole pairs to the pole position counter and outputs the pole position.

[0100] In addition, the above-mentioned DC excitation command generation unit 11, torque zero determination unit 12, pole initial position acquisition unit 13, rotor actual position acquisition unit 14, speed control unit 31, current command generation unit 32, current control unit 33, dq three-phase conversion unit 34, three-phase dq conversion unit 36, speed acquisition unit 37, and pole position updating unit 41 can be constructed, for example, by a software program method or by a combination of various electronic circuits and software programs. For example, in the case of constructing these by a software program method, the arithmetic processing device within the motor control device 1000 is operated according to the software program, whereby the functions of the above-mentioned respective units can be realized. In addition, the DC excitation command generation unit 11, torque zero determination unit 12, pole initial position acquisition unit 13, rotor actual position acquisition unit 14, speed control unit 31, current command generation unit 32, current control unit 33, dq three-phase conversion unit 34, three-phase dq conversion unit 36, speed acquisition unit 37, and pole position updating unit 41 can also be realized as a semiconductor integrated circuit in which a software program for realizing the functions of the respective units is written.

[0101] Second Embodiment

[0102] Hereinafter, the pole initial position detection device 1A according to the second embodiment of the present disclosure will be described. The pole initial position detection device 1A is equivalent to a modified example of the pole initial position detection device 1 in the first embodiment. Figure 9 is a block diagram showing the structure of the pole initial position detection device 1A. The pole initial position detection device 1A, as a structural element for realizing the function of the DC excitation command generation unit 11 according to the first embodiment, includes a first command generation unit 11A, an excitation phase determination unit 16, and a second command generation unit 11B. The first command generation unit 11A has the function of generating the following first command, which was described as the function of the DC excitation command generation unit 11 in the first embodiment: causing a constant excitation current with the current phase fixed to the first phase to flow through the synchronous motor 2. The second command generation unit 11B generates a command (hereinafter, also referred to as the second command) for causing a constant excitation current with the current phase fixed to an arbitrarily set second phase to flow through the synchronous motor 2. The excitation phase determination unit 16 determines the rotation direction of the synchronous motor 2 and the speed command (ω cmd)'s rotation direction so that the synchronous motor 2 rotates in the same direction as the speed command (ω cmd ), the first phase for generating the first command is determined. With this configuration, the direction in which the rotor rotates due to the DC excitation of the first command generated by the first command generation unit 11A can be made to coincide with the rotation direction of the rotor based on the speed command (ω cmd ), and the transition from the magnetic pole initial position detection operation to the speed control can proceed smoothly, thereby enabling the time to reach the commanded speed to be shortened. Hereinafter, the above function of the magnetic pole initial position detection device 1A according to the second embodiment will be described.

[0103] The following is an outline of the detection operation of the magnetic pole initial position of the magnetic pole initial position detection device 1A according to the second embodiment. First, the second command generation unit 11B causes the synchronous motor 2 to perform DC excitation with the current phase of an arbitrarily set second phase (θ0). The DC excitation in this case may also be for an extremely short time. As a result, the rotor starts to rotate from the initial position in the direction corresponding to the DC excitation of the current phase of the second phase. Next, the excitation phase determination unit 16 obtains the relationship between the excitation phase (second phase) at this time and the rotation direction of the rotor. Based on this relationship, the excitation phase determination unit 16 determines the first phase for generating the first command so that the rotation direction (polarity) of the rotor according to the first command is the same as the rotation direction (polarity) of the speed command (ω cmd ). The first command generation unit 11A generates the first command using the excitation phase (first phase) determined by the excitation phase determination unit 16. When performing DC excitation according to the first command generated by the first command generation unit 11A, the magnetic pole initial value is obtained by the operations of the torque zero determination unit 12 and the magnetic pole initial position acquisition unit 13. In this case, after the first command generation unit 11A starts issuing the first command to the synchronous motor 2, the torque zero determination unit 12 detects the first torque zero generated and notifies the detection result to the magnetic pole initial position acquisition unit 13. When the magnetic pole initial position is obtained, the speed control is transferred to the synchronous motor 2 according to the speed command (ω cmd ).

[0104] Figure 10This is a flowchart showing the process (hereinafter referred to as the excitation phase determination process) performed by the magnetic pole initial position detection device 1A (mainly the second command generation unit 11B and the excitation phase determination unit 16) for determining the excitation phase (first phase) used to detect the magnetic pole initial position. First, the magnetic pole initial position detection device 1A confirms the value of the variable 'STAGE' (step S1). Since the value of the variable 'STAGE' is initialized to zero at the start of this process, it is first determined that 'STAGE' = 0 when step S1 is executed, and the process proceeds to step S2. In step S2, the magnetic pole initial position detection device 1A obtains the rotor position (θ m0 ) at the start of this process from the rotor actual position acquisition unit 14 and stores it, and updates the variable 'STAGE' to 1.

[0105] Next, the second command generation unit 11B substitutes the value of an arbitrarily set current phase θ0 (second phase) into the variable Θ for setting the current phase of the DC excitation e and generates a second command. The second command is sent to the current control unit 33 of the motor control device 1000, and DC excitation is performed according to the second command (step S3). In step S4, the value of the variable 'STAGE' is confirmed. Currently, 'STAGE' = 1, so the process proceeds to step S5. In step S5, the magnetic pole initial position detection device 1A determines whether the rotor rotates. As a result, when the rotor rotates (S5: "Yes"), the excitation phase determination unit 16 determines whether the rotation direction (polarity) of the rotor is the same as the rotation direction (polarity) based on the speed command (ω cmd ) (step S7). As a result, when the rotation direction of the rotor is the same as the rotation direction based on the speed command (S7: "Yes"), the excitation phase determination unit 16 substitutes the value of the current phase θ0 set in step S3 into the variable Θ for generating the first command w (step S8).

[0106] In addition, when the rotation direction of the rotor is not the same as the rotation direction based on the speed command (ω cmd ) (S7: "No"), the excitation phase determination unit 16 substitutes the value obtained by adding 180 degrees to the current phase θ0 into the variable Θ w (step S9). Here, adding the value obtained by adding 180 degrees to the current phase θ0 to the variable Θ w is because the rotation direction of the rotor in the DC excitation based on the excitation phase (Θ w ) is set to the opposite direction of the rotation direction of the rotor in the case of DC excitation based on the current phase θ0. The position of the rotor at the current time point is the rotor position (θ stored in step S2 at the start of the process m0) Before that, the phase for advancing the rotor by a corresponding amount is added to the variable Θ w and set as the exciting phase (first phase) for generating the final first command (step S10). Specifically, in step S10, the variable Θ is determined as follows w .

[0107] Θ w = Θ w + pp(P c - θ m0 )

[0108] Here, Pc: Current position of the rotor

[0109] pp: Number of pole pairs

[0110] When the exciting phase (Θ w ) for generating the first command is determined in this way, the exciting phase determination unit 16 sends the determined exciting phase (Θ w ) to the first command generation unit 11A and updates the variable 'STAGE' to 3 indicating the completion of the process (step S11). When the variable 'STAGE' is updated to 3 in step S11, it is determined in step S1 that the variable 'STAGE' is 3, and this exciting phase determination process ends. The determined exciting phase (Θ w ) is used to generate the first command in the first command generation unit 11A, so that the rotation direction of the rotor in the DC excitation for the magnetic pole initial position detection operation can be made consistent with the rotation direction of the rotor based on the speed command (ω cmd ).

[0111] When it is determined in step S5 that the rotor is not rotating, the magnetic pole initial position detection device 1A performs DC excitation by adding a current phase Θ e that is 90 degrees to the current phase θ0 (step S6). Here, when it is determined in step S5 that the rotor is not rotating, it is the case where the current phase θ0 is near the magnetic pole initial position (phase) of the rotor. Therefore, to avoid this situation, DC excitation is performed with the current phase Θ e obtained by adding 90 degrees to the current phase θ0. In step S6, the variable 'STAGE' is updated to 2. When the variable 'STAGE' is updated to 2 in step S5 and the process returns to step S1, it is determined that the variable 'STAGE' is 2, and the process proceeds to step S4. In this case, when it is determined in step S4 that the value of the variable 'STAGE' is 2, the process proceeds to step S12.

[0112] In step S12, as the current phase Θ eThe result of direct current excitation is used to determine whether the rotor is rotating. As a result, when it is determined that the rotor is rotating (S12: "Yes"), the rotation direction (polarity) of the rotor is determined (step S13). As a result, when it is determined that the rotation direction of the rotor is the positive direction (S13: '+'), the current phase θ0 set in step S3 represents the initial position (phase) of the magnetic pole. In this case, the value obtained by adding the phase corresponding to the movement of the rotor after starting this process to the current phase θ0 is obtained by the following formula (Θ w ) and set as the initial position of the magnetic pole (step S14).

[0113] Θ w = θ0 + pp(P c - θ m0 )

[0114] In addition, when it is determined in step S13 that the rotation direction of the rotor is the negative direction (S13: '-'), the value obtained by adding 180 degrees to the current phase θ0 set in step S3 represents the initial position (phase) of the magnetic pole. In this case, the value obtained by adding the phase corresponding to the movement of the rotor after starting this process to the value obtained by adding 180 degrees to the current phase θ0 is obtained by the following formula (Θ w ) and set as the initial position of the magnetic pole (step S15).

[0115] Θ w = θ0 + 180 degrees + pp(P c - θ m0 )

[0116] In step S16, the Θ w obtained in step S14 or S15 is determined as the initial position of the magnetic pole, and the variable 'STAGE' is updated to 3 to complete this excitation phase determination process. In this case, this excitation phase determination process is ended, and the generation of the first instruction by the first instruction generation unit 11A and the detection of the initial position of the magnetic pole based on the first instruction are not performed. The Θ w obtained in step S14 or S15 is regarded as the initial position of the magnetic pole output from the magnetic pole initial position detection device 1 to the magnetic pole position update unit 41.

[0117] Here, it is explained that when direct current excitation is performed on the current phase Θ e obtained by adding 90 degrees to the current phase θ0, the initial position of the magnetic pole can be determined through steps S14 and S15 according to the rotation direction of the rotor. Determining that the rotor does not rotate in step S5 means that the current phase θ0 is the same as the phase of the initial value of the magnetic pole or differs from the phase of the initial position of the magnetic pole by 180 degrees. In step S6, direct current excitation is performed with the current phase θ0 + 90 degrees and the rotation state of the rotor is considered. As referred toFigure 3 Explanation: The rotation of the rotor means the situation of the deviation θ between the excitation phase ( e at 0 degrees in the case of Figure 3 excitation current I) and the pole position, that is, the situation of generating the torque shown in formulas (2) and (3). Here, consider the non-significant situation (formula (3)). Figure 11 It is a graph showing the torque generated by the deviation θ between the excitation phase and the pole position according to formula (3). As Figure 11 shown, within the range where the deviation θ between the excitation phase and the pole position is positive (0 to 180 degrees), the torque is obtained as a negative value, and within the range where θ is negative (0 to -180 degrees), the torque is obtained as a positive value.

[0118] In this case, as Figure 12 shown, when the pole position (phase) exists in the first quadrant and the second quadrant with respect to the coordinate system where the excitation current I e is set to the phase of 0 degrees on the d c axis, the rotor rotates in the negative direction, and when the pole position (phase) is in the third quadrant and the fourth quadrant, the rotor rotates in the positive direction. Here, when noting that the positive direction of the phase is around the left side of Figure 12 , it can be understood that in the DC excitation of the current phase (θ0 + 90 degrees), the rotation direction of the rotor is judged as positive (S13: '+') when the initial pole position is 90 degrees in the negative direction with respect to the current phase (θ0 + 90 degrees) (that is, the position of the current phase θ0). In addition, in the DC excitation of the current phase (θ0 + 90 degrees), the rotation direction of the rotor is judged as negative (S13: '-') when the initial pole position is 90 degrees in the positive direction with respect to the current phase (θ0 + 90 degrees) (that is, the position obtained by adding 180 degrees to the current phase θ0). Therefore, in step S14, the value (Θ w ) obtained by adding the phase corresponding to the rotor movement to the current phase θ0 can be determined as the initial pole value, and in step S15, the value (Θ w ) obtained by adding the phase corresponding to the rotor movement to the value obtained by adding 180 degrees to the current phase θ0 can be determined as the initial pole value.

[0119] Returning to Figure 10 the explanation, in step S12, it is judged that the rotor does not rotate when the synchronous motor 2 is in a constrained state or the power line is disconnected. Therefore, in this case, the pole initial position detection device 1A issues an alarm and updates the variable 'STAGE' to 3 to stop this process.

[0120] As described above, according to the second embodiment, the direction in which the rotor rotates due to the DC excitation of the first command generated by the first command generation unit 11A can be made to coincide with the rotation direction of the rotor based on the speed command (ω cmd ), and the transition from the magnetic pole initial position detection operation to the speed control can be smoothly performed.

[0121] According to an embodiment of the present disclosure, it is possible to implement a DC excitation type magnetic pole initial position detection device that can obtain the magnetic pole initial position of a synchronous motor rotor in a short time, and a magnetic pole position detection device including the same.

[0122] The embodiments of the present invention have been described above. However, those skilled in the art will understand that various modifications and changes can be made without departing from the scope disclosed in the following technical solutions.

Claims

1. A device for detecting the initial position of magnetic poles, which detects the initial position of the magnetic poles of the rotor of a synchronous motor. The device for detecting the initial position of magnetic poles is characterized in that it comprises: a DC excitation command generation unit that generates a first command which causes a constant excitation current with a fixed current phase at a first phase to flow through the synchronous motor; a torque zero determination unit that determines whether the torque generated on the rotor of the synchronous motor is zero when the excitation current based on the first command flows through the synchronous motor; and a magnetic pole initial position acquisition unit that acquires the initial position of the magnetic poles of the rotor of the synchronous motor based on the actual position of the rotor near the time point when the torque zero determination unit determines that the torque is zero, the number of pole pairs of the synchronous motor, and the excitation phase in the DC excitation based on the first command. Until the rotor stops, the torque zero determination unit determines that the torque is zero at the time point when the polarity of the acceleration of the synchronous motor changes.

2. The device for detecting the initial position of magnetic poles according to claim 1, characterized in that It further includes: a rotor actual position acquisition unit that acquires the position of the rotor from a sensor provided in the synchronous motor; and a storage unit that stores information related to the number of pole pairs of the synchronous motor.

3. A device for detecting the initial position of magnetic poles, which detects the initial position of the magnetic poles of the rotor of a synchronous motor. The device for detecting the initial position of magnetic poles is characterized in that it comprises: a DC excitation command generation unit that generates a first command which causes a constant excitation current with a fixed current phase at a first phase to flow through the synchronous motor; a torque zero determination unit that determines whether the torque generated on the rotor of the synchronous motor is zero when the excitation current based on the first command flows through the synchronous motor; and a magnetic pole initial position acquisition unit that acquires the initial position of the magnetic poles of the rotor of the synchronous motor based on the actual position of the rotor near the time point when the torque zero determination unit determines that the torque is zero, the number of pole pairs of the synchronous motor, and the excitation phase in the DC excitation based on the first command. Until the rotor stops, the torque zero determination unit determines that the torque is zero at the time point when the speed of the synchronous motor is maximum or minimum.

4. The device for detecting the initial position of magnetic poles according to claim 3, characterized in that It further includes: a rotor actual position acquisition unit that acquires the position of the rotor from a sensor provided in the synchronous motor; and a storage unit that stores information related to the number of pole pairs of the synchronous motor.

5. The magnetic pole initial position detection device according to claim 2 or 4, characterized in that, It is determined that the actual position of the rotor near the time point when the torque is zero is the position of the rotor at any time point between two sampling time points that delimit the sampling interval including the time point when the torque is determined to be zero by the torque zero determination unit in the sampling interval of the position of the rotor acquired by the rotor actual position acquisition unit.

6. The magnetic pole initial position detection device according to any one of claims 1 to 4, characterized in that, In the case where the synchronous motor is a synchronous motor with significance, the DC excitation command generation unit generates, as the first command, a command for causing the excitation current less than a predetermined upper limit value to flow through the synchronous motor.

7. The magnetic pole initial position detection device according to claim 6, characterized in that, When the magnitude of the main magnetic flux of the above synchronous motor is set to Φ and the d-phase inductance is set to L d and the q-phase inductance is set to L q the above predetermined upper limit value is set based on the following formula:

8. The magnetic pole initial position detection device according to any one of claims 1 to 4, characterized in that, The DC excitation command generation unit includes: a second command generation unit that generates a second command for causing a constant excitation current with a current phase fixed to an arbitrarily set second phase to flow through the synchronous motor; an excitation phase determination unit that, based on the rotation direction of the synchronous motor when the excitation current based on the second command flows through the synchronous motor and the rotation direction with respect to the speed command of the synchronous motor, determines the first phase for generating the first command in such a manner that the synchronous motor rotates in the same direction as the rotation direction of the speed command according to the first command; and a first command generation unit that generates the first command using the current phase of the first phase determined by the excitation phase determination unit.

9. A magnetic pole position detection device, characterized in that, It includes a magnetic pole position update unit that outputs the magnetic pole position of the rotor of the synchronous motor in which the magnetic pole initial position detected by the magnetic pole initial position detection device according to any one of claims 1 to 8 is initialized.

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