JP7497695B2 - Motor Control Device - Google Patents

Description

The present invention relates to a motor control device that starts a motor without a sensor.

Conventionally, in devices that start a motor without a sensor, synchronous operation is performed at the beginning of startup without estimating the rotor position, and then the system transitions to steady operation in which the rotor position is estimated. For example, a method has been proposed in which a phase adjustment section is provided at motor startup to ensure a transition from synchronous operation in which the rotor position is not estimated to vector control in which the rotor position is estimated (see, for example, Patent Document 1). In addition, a method has been proposed in which, if the rotor is rotating in the reverse direction due to an external force at motor startup, the rotor is started in the reverse direction, the rotor is pulled in, and then the rotor is rotated in the forward direction (see, for example, Patent Document 2).

For example, the outdoor unit of an air conditioner has a heat exchanger, a fan for the heat exchanger (hereinafter sometimes referred to as the "outdoor unit fan"), and a motor that rotates the outdoor unit fan (hereinafter sometimes referred to as the "fan motor"). The outdoor unit fan motor rotates together with the outdoor unit fan as the outdoor unit fan rotates idly in response to external forces such as wind before the fan motor is started (i.e. while the fan motor is stopped). When the outdoor unit fan rotates idly in the forward direction, the fan motor also rotates in the forward direction, and when the outdoor unit fan rotates in the opposite direction to the forward direction, i.e. in the reverse direction, the fan motor also rotates in the reverse direction.

Patent No. 6003143 Patent No. 3731105

When a fan motor is rotating in reverse due to strong winds, it becomes highly loaded, and the rotating magnetic field and the rotor become out of sync during synchronous operation at the start of startup, and the motor is prone to stopping (losing synchronism). In such cases, a startup voltage higher than normal must be applied to prevent loss of synchronism. However, fan motors do not frequently become highly loaded at startup. For this reason, if the startup parameters of a fan motor, such as the startup voltage, are designed to meet high-load conditions, there are many cases where a voltage higher than the voltage required for startup is applied to the fan motor, resulting in a problem of reduced energy efficiency of the fan motor.

The present invention was made with a focus on the previously unsolved problems, and aims to provide a motor control device that can improve energy saving during motor startup.

In order to achieve the above object, a motor control device according to one aspect of the present invention is characterized by comprising: a load detection unit that detects a load applied to a sensorless synchronous motor; a synchronous voltage setting unit that sets a second voltage command, which is a voltage command for driving the synchronous motor based on an input first voltage command; a drive unit that drives the synchronous motor according to the second voltage command input from the synchronous voltage setting unit; a ranking generation unit that stores combinations of a startup voltage and the load that start the synchronous motor and generates a ranking of the startup voltages based on the frequency of successful startup of the synchronous motor; and a startup voltage selection unit that selects the startup voltage to be used during startup processing of the synchronous motor based on the load detected by the load detection unit and the ranking generated by the ranking generation unit, and outputs the voltage command of the selected startup voltage to the synchronous voltage setting unit as the first voltage command.

According to one aspect of the present invention, it is possible to improve energy saving when starting a motor.

1 is a schematic configuration diagram illustrating an example of a motor control device according to an embodiment of the present invention. FIG. 11 is a block diagram showing an example of a transfer function of a phase adjustment process. FIG. 4 is a diagram illustrating an example of the relationship between the load and the rotation speed of a fan motor. FIG. 4 is a diagram showing an example of a starting current waveform of a fan motor. 11 is a graph showing an example of a correspondence relationship between an index and a start-up voltage. FIG. 11 is a diagram showing an example of the structure of the frequency of successful start-up of the fan motor stored in combination with a load in a ranking generation unit provided in the motor control device according to one embodiment of the present invention. FIG. 13 is a diagram showing an example of a histogram in which start-up voltages at which a fan motor is successfully started are expressed by index. FIG. 13 is a diagram showing an example of a ranking of indexes generated by a ranking generation unit. 4 is a flowchart showing an example of the operation of the motor control device according to the embodiment of the present invention. 5 is a flowchart showing an example of a start-up process for reverse rotation in the operation of a motor control device according to an embodiment of the present invention. 5 is a flowchart showing an example of a normal rotation start-up process in the operation of a motor control device according to an embodiment of the present invention. 11 is a graph showing an example of changes in the rotation speed of the fan motor and the voltage applied to the motor when start-up is successful during normal start-up. 11 is a graph showing an example of changes in the rotation speed of the fan motor and the voltage applied to the motor when start-up fails during normal start-up;

In the following detailed description, certain specific configurations are described to provide a complete understanding of the embodiments of the present invention. However, it is clear that other embodiments can be implemented without being limited to such specific configurations. In addition, the following embodiments do not limit the invention according to the claims, but include all combinations of the characteristic configurations described in the embodiments.

<Configuration of the motor control device>
An embodiment of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same parts are given the same reference numerals. Here, a case will be described in which a motor control device according to the present invention is applied to a sensorless synchronous motor control device for a fan motor M. The fan motor M is a motor that drives an outdoor unit fan of an air conditioner, and is a sensorless synchronous motor with multiple phases, for example, three phases.

FIG. 1 is a configuration diagram showing an example of a motor control device 1 according to an embodiment of the present invention.
1, the motor control device 1 includes a synchronous voltage setting unit 3 that sets voltage vectors Vu, ^Vv, Vw (an example of a second voltage command, described in detail below) that are voltage commands for driving a fan motor (an example of a sensorless synchronous motor) M based on an input voltage command (an example of a first voltage command) V* for a motor applied voltage. The synchronous voltage setting unit 3 includes a calculation unit 30, a voltage output unit 40, an integration unit 50, and a first conversion unit 60, which will be described in detail below.

The motor control device 1 also includes a drive unit 10 that drives the fan motor M in response to the voltage vector (Vu, Vv, Vw) input from the synchronous voltage setting unit 3. The drive unit 10 drives the fan motor M, for example, by supplying three-phase AC signals U, V, and W to the fan motor M. The internal configuration of the drive unit 10 will be described later.

The motor control device 1 also includes a detection unit 20 that detects at least two sets of current amplitudes. Specifically, the detection unit 20 includes a U-phase/W-phase current detection circuit (hereinafter also simply referred to as a current detection circuit) 21 that detects the motor current flowing through the U-phase and W-phase stator coils of the fan motor M. The current detection circuit 21 detects the amplitude of the U-phase motor current (hereinafter also simply referred to as the U-phase current) Iu and the amplitude of the W-phase motor current (hereinafter also simply referred to as the W-phase current) Iw. The amplitudes of the U-phase current Iu and W-phase current Iw detected by the current detection circuit 21 are input to an A/D converter 21a provided in the motor control device 1. The amplitudes of the U-phase current Iu and W-phase current Iw, which are analog signals, are AD-converted by the A/D converter 21a into digital signals that can be controlled by a computer, and are supplied to a calculation unit 30 provided in the synchronization voltage setting unit 3.

The calculation unit 30 converts the current vector (Iu, Iw) in a fixed coordinate system (UVW coordinate system) when the drive unit 10 drives the fan motor M into a current vector (Iγ, Iδ) in a rotating coordinate system (γ-δ coordinate system). The rotating coordinate system (γ-δ coordinate system) has a δ axis and a γ axis that intersect with each other. The calculation unit 30 calculates an estimated angular velocity ωe' of the rotating magnetic field that makes the γ component of the current vector in the converted rotating coordinate system zero. Specifically, the calculation unit 30 includes a second conversion unit (three-phase to two-phase converter (UVW/γ-δ)) 31 and a speed estimation processing unit 32.

The second conversion unit 31 receives the detected value of the amplitude of the U-phase current Iu and the detected value of the amplitude of the W-phase current Iw from the current detection circuit 21. The second conversion unit 31 converts a current vector (Iu, Iw) in a fixed coordinate system (UVW coordinate system) into a current vector (Iγ, Iδ) in a rotating coordinate system (γ-δ coordinate system) by, for example, the following equations (1) and (2). Note that, if a driver 12 (described in detail later) provided in the drive unit 10 includes a shunt resistor, the current may be detected from the shunt resistor instead of the current detection circuit 21.
Iγ
= (√2) {Iu × cos(θe' + π/6) - Iw × sin(θe')}
… (1)
Iδ
=-(√2){Iu × sin(θe' + π/6) + Iw × cos(θe')}
… (2)

The second conversion unit 31 outputs the γ component of the current vector in the converted rotating coordinate system (γ-δ coordinate system), i.e., the γ-axis current Iγ, to the speed estimation processing unit 32, and outputs the δ component of the current vector, i.e., the δ-axis current Iδ, to the voltage output unit 40.

The speed estimation processing unit 32 receives the γ-axis current Iγ from the second conversion unit 31. The speed estimation processing unit 32 calculates an estimated angular velocity ωe', which is an estimate of the angular velocity ωe of the rotating magnetic field that makes the γ-axis current Iγ zero, according to the received γ-axis current Iγ. The speed estimation processing unit 32 supplies the calculated estimated angular velocity ωe' to the integration unit 50 and the voltage output unit 40.

Figure 2 is a block diagram showing the transfer function of the phase adjustment process executed by the speed estimation processing unit 32. The speed estimation processing unit 32 multiplies the γ-axis current Iγ by a coefficient Ki using a multiplier 32a, and multiplies the γ-axis current Iγ by a coefficient Kp using a multiplier 32b. Furthermore, the speed estimation processing unit 32 integrates the output of the multiplier 32a using an integrator 32c, and adds the output of the integrator 32c and the output of the multiplier 32b using an adder 32d to calculate the estimated angular velocity ωe'.

At this time, in order to converge the estimated angular velocity ωe′, Vd (=Vγ) is calculated using the estimated angular velocity ωe′. An appropriate value of the γ-axis voltage Vγ is given by the following equation (3).
Vγ=−ωe′·Lq·Iδ … (3)
In equation (3), Lq is the q-axis inductance value, and Iδ is a substitute value. In other words, when the estimated angular velocity ωe′ converges, the phase difference between the d-axis and the γ-axis also converges to zero, and the γ-δ value is used instead of the dq value.

In the speed estimation processing unit 32, the γ-axis current Iγ on the control axis γ-δ axis is PI controlled to adjust the rotation speed so that the γ-axis current Iγ becomes 0 [A], and the γ-δ coordinate axis approaches the d-q coordinate axis. Specifically, the δ-axis voltage Vδ is set to a constant value, and the γ-axis current Iγ is input to the speed estimation processing unit 32 to obtain an estimated angular velocity ωe'. The estimated angular velocity ωe' is integrated by an integrator 51 to obtain an estimated rotation angle θe'. The γ-axis voltage Vγ is applied by equation (3) in the estimated voltage output unit 42 (see FIG. 1) described later, and the fan motor M converges to an appropriate operating state as optimal synchronous operation at a rotation speed balanced by the δ-axis voltage Vδ and the load.

Returning to FIG. 1, the voltage output unit 40 provided in the synchronous voltage setting unit 3 estimates the γ component Vγ of the voltage vector on the rotating coordinate system (γ-δ coordinate system) based on the estimated angular velocity ωe' calculated by the calculation unit 30. At the same time, the voltage output unit 40 sets the δ component Vδ of the voltage vector on the rotating coordinate system (γ-δ coordinate system) to a predetermined value. Specifically, the voltage output unit 40 has a fixed voltage output unit 41 to which a voltage command V ^* of the motor applied voltage is input, and an estimated voltage output unit 42 to which the estimated angular velocity ωe' and the current vector Iδ are input. The fixed voltage output unit 41 sets the δ component Vδ of the voltage vector to a predetermined value (for example, a fixed value), and outputs the value to the first conversion unit 60 as the δ-axis voltage command Vδ ^* .

For example, when starting the fan motor M, the voltage output unit 40 sets the γ-axis voltage command Vγ ^* to 0 and the δ-axis voltage command Vδ ^* to a predetermined value (e.g., a fixed value) as the starting voltage to start driving the fan motor M. Although details will be described later, the motor control device 1 can control the acceleration operation of the fan motor M in the starting process of the fan motor M, taking into consideration the load applied to the fan motor M before the starting process. For this reason, in this embodiment, the δ-axis voltage command Vδ ^* of the starting voltage preset in the fixed voltage output unit 41 is set to the minimum value required for starting, thereby improving energy saving. The motor control device 1 adjusts the angular velocity of the rotating magnetic field so that the δ-axis voltage command Vδ ^* that generates this torque and the load are appropriately balanced.

The estimated voltage output unit 42 receives the estimated angular velocity ωe' from the velocity estimation processing unit 32, and receives the δ-axis current Iδ from the second conversion unit 31 of the calculation unit 30. The estimated voltage output unit 42 estimates a γ-component Vγ of the voltage vector using the estimated angular velocity ωe' and the δ-axis current Iδ, and outputs the estimated value to the first conversion unit 60 as a γ-axis voltage command Vγ ^* .

The integrator 50 provided in the synchronization voltage setting unit 3 integrates the estimated angular velocity ωe' to obtain the estimated rotation angle θe'. Specifically, the integrator 50 has an integrator 51. The integrator 51 integrates the estimated angular velocity ωe' of the rotating magnetic field to calculate the estimated rotation angle θe', which is an estimate of the phase angle θe of the rotating coordinate system that rotates together with the rotating magnetic field. The integrator 51 outputs the calculated estimated rotation angle θe' to the first conversion unit 60 and the calculation unit 30, respectively.

A first conversion unit 60 provided in the synchronous voltage setting unit 3 converts the voltage vector in the rotating coordinate system (γ-δ coordinate system) estimated by the voltage output unit 40 into a voltage vector in a fixed coordinate system (UVW coordinate system) using the estimated rotation angle θe′ obtained by the integration unit 50. Specifically, the first conversion unit 60 has a two-phase to three-phase converter (γ-δ/UVW) 61. The two-phase to three-phase converter 61 receives a γ-axis voltage command Vγ ^* and a δ-axis voltage command Vδ ^* , i.e., a voltage vector (Vγ, Vδ) in the rotating coordinate system (γ-δ coordinate system) from the voltage output unit 40. The two-phase to three-phase converter 61 receives the estimated rotation angle θe′ from the integration unit 50. The two-phase to three-phase converter 61 converts a voltage vector (Vγ, Vδ) in a rotating coordinate system (γ-δ coordinate system) into a voltage vector (Vu, Vv, Vw) in a fixed coordinate system (UVW coordinate system), for example, using the following equations (4) to (6):

Vu
= (√(2/3)) {Vγ × cos(θe′) − Vδ × sin(θe′)}
… (4)
Vv
= (√(1/2) × Vγ + √(1/6) × Vδ) × sin(θe′)
+ (√(1/2) × Vδ-√(1/6) × Vγ) × cos(θe′)
… (5)
Vw
= (√(1/6) × Vδ - √(1/2) × Vγ) × sin(θe′)
−(√(1/6)×Vγ+√(1/2)×vδ)×cos(θe′) …(6)

The two-phase to three-phase converter 61 outputs the voltage vector (Vu, Vv, Vw) in the fixed coordinate system (UVW coordinate system) in the converted rotating coordinate system (γ-δ coordinate system) to the drive unit 10. Note that although equations (4) to (6) are equations for three-phase demodulation, the two-phase to three-phase converter 61 may also perform two-phase modulation to increase the voltage utilization rate.

The driving unit 10 drives the fan motor M so that the fan motor M operates with a voltage corresponding to the voltage vector converted by the first conversion unit 60. Specifically, the driving unit 10 has a PWM converter 11 and a driver 12. The PWM converter 11 receives a voltage vector (Vu, Vv, Vw) in a fixed coordinate system (UVW coordinate system), i.e., a U-phase voltage command Vu ^* , a V-phase voltage command Vv ^* , and a W-phase voltage command Vw ^* (each of which is an example of a second voltage command) from the first conversion unit 60. The PWM converter 11 converts the U-phase voltage command Vu ^* , the V-phase voltage command Vv ^* , and the W-phase voltage command Vw ^* into PWM signals and supplies them to the driver 12. As a result, the PWM converter 11 drives the fan motor M via the driver 12.

The driver 12 receives the PWM signal from the PWM converter 11. The driver 12 has, for example, multiple switching elements (not shown), and performs power conversion by switching the multiple switching elements at a predetermined timing according to the PWM signal, and drives the fan motor M by supplying the generated three-phase AC signals U, V, and W to the fan motor M.

As shown in FIG. 1, the motor control device 1 includes a step-out determination unit 70. The step-out determination unit 70 includes a smoothing processing unit 71 and a comparator 72. The smoothing processing unit 71 includes a rectifying unit 71a and a low-pass filter unit (LPF) 71b. The rectifying unit 71a receives a signal representing the amplitude of, for example, the U-phase current Iu of the current detection circuit 21, performs full-wave rectification or half-wave rectification, and outputs the signal to the low-pass filter unit 71b. The low-pass filter unit 71b receives the rectified signal from the rectifying unit 71a, performs low-pass filtering, extracts the current amplitude or effective value, and outputs the signal to the comparator 72. The comparator 72 receives the amplitude signal, which is the output of the smoothing processing unit 71, at its positive input terminal, and a threshold voltage (hereinafter also simply referred to as the threshold) Vth is input to the negative input terminal of the comparator 72.

Here, a method for setting the voltage value of the threshold voltage Vth of the comparator 72 will be described. In the speed estimation processing unit 32, the γ-axis current Iγ on the control axis γ-δ axis is PI controlled to adjust the rotation speed so that the γ-axis current Iγ becomes 0 [A], and the phase difference between the γ-δ coordinate axis and the d-q coordinate axis approaches zero. At this time, if the phase of the γ-δ coordinate axis can be brought closer to the phase of the d-q coordinate axis, the amplitude of the U-phase current Iu gradually decreases so that the minimum current required for the load flows. However, if the rotating magnetic field and the rotor cannot be synchronized and a loss of synchronization occurs, the amplitude of the U-phase current Iu does not decrease, and the fan motor M eventually stops. As a result, since no induced voltage is generated, the U-phase current Iu becomes Iu = (applied voltage) / (magnitude of winding resistance of the fan motor M). Therefore, by detecting the magnitude of the current after this phase adjustment, it is possible to determine that the motor starts normally when the current is small, and that a start-up failure due to loss of synchronization occurs when the current is large.

When the control unit 80 determines that the synchronous operation has been successful, it switches the operation mode of the fan motor M from the startup operation mode to the steady operation mode. When the control unit 80 determines that the synchronous operation has failed, it attempts to restart the fan motor M by changing the startup voltage, and if it is not determined that the synchronous operation has been successful even after a predetermined number of restart attempts, it determines that the fan motor M has failed and notifies the failure by generating an alarm, etc.

As shown in FIG. 1, the motor control device 1 includes a load detection unit 90 that detects the magnitude of the load (hereinafter also simply referred to as "load") applied to the fan motor M at startup. The load detection unit 90 includes a rotation detection unit 91 that detects the direction of rotation and the number of rotations of the fan motor M before the fan motor M is started. The load detection unit 90 includes a startup load detection unit 92 that detects the load based on the current flowing through the fan motor M when the fan motor M is successfully started.

Before starting the fan motor M, the rotation detection unit 91 detects the rotation direction of the fan motor M when it is idling (hereinafter, sometimes referred to as the "idling direction") and the rotation speed of the fan motor M when it is idling (hereinafter, sometimes referred to as the "idling rotation speed"), and outputs the detected idling direction and idling rotation speed to the control unit 80. For example, the rotation detection unit 91 detects the idling direction and idling rotation speed using the induced voltages of the U, V, and W phases of the fan motor M. For example, if the rising edge detected next to the rising edge of the induced voltage of the U phase is the rising edge of the induced voltage of the V phase, the rotation detection unit 91 determines that the idling direction is the forward direction, and if the rising edge detected next to the rising edge of the induced voltage of the U phase is the rising edge of the induced voltage of the W phase, the rotation detection unit 91 determines that the idling direction is the reverse direction. In addition, since the period of the induced voltage of the fan motor M becomes smaller as the idling speed increases, the rotation detection unit 91 detects the idling speed based on the period of the induced voltage of the U phase, for example.

Then, the control unit 80 performs forward rotation synchronous operation when it determines that the fan motor M is rotating in the forward direction based on the idling rotation speed and idling direction of the fan motor M. On the other hand, the control unit 80 performs reverse rotation synchronous operation when it determines that the fan motor M is rotating in the reverse direction based on the idling rotation speed and idling direction of the fan motor M.

With the above configuration, when the idling direction is the forward direction, the current is reset after performing a positioning current application process to position the rotor, and then the angular velocity ωe' of the rotating magnetic field that makes the γ-axis current Iγ zero is estimated, and synchronous operation processing is performed. As a result, when the fan motor M rotates, a signal consisting of the amplitude of the U-phase current Iu detected by the current detection circuit 21 is input to the out-of-step determination unit 70, and the amplitude signal after smoothing is compared with the threshold voltage Vth. In the control unit 80, when it is determined that the synchronous operation is successful based on the comparison result between the amplitude signal and the threshold voltage Vth, the operation mode of the fan motor M is switched from the startup operation mode to the normal operation mode. On the other hand, when it is determined that the synchronous operation has failed, a restart is attempted. And when the synchronous operation is not successful every time even after a predetermined number of restart attempts, a fault notification is issued. This allows the user to recognize that the fan motor M has failed. On the other hand, when the idling direction is the reverse direction, the reverse synchronous operation is performed, and then the forward synchronous operation is performed.

The relationship between the load and pre-start rotation speed in fan motor M has the characteristics shown in Figure 3, for example. In Figure 3, the horizontal axis is the rotation speed [rpm] before start, and the vertical axis is the load. As shown in Figure 3, when starting in the forward direction from a state in which the motor is rotating in reverse due to headwind, the load is large, and the higher the rotation speed during reverse rotation, the larger the load. Conversely, when starting from a forward rotation state, the higher the rotation speed, the smaller the load.

The wind blowing on the fan motor M is a load not only before the fan motor M is started, but also during the startup process of the fan motor M. For this reason, the magnitude of the current flowing through the fan motor M after phase adjustment changes depending on the magnitude of the load applied to the fan motor M, even if the rotation speed of the fan motor M is the same. If the load applied to the fan motor M is large, the current flowing through the fan motor M also increases, and if the load applied to the fan motor M is small, the current flowing through the fan motor M also decreases. The reason why the magnitude of the current flowing through the fan motor M changes depending on the load applied to the fan motor M, even if the rotation speed of the fan motor M is the same, is because the torque required to rotate the fan motor M changes.

Figure 4 shows an example of the current waveform (starting current waveform) of the U-phase current Iu when the fan motor is started. Figure 4(a) shows an example of the current waveform of the U-phase current Iu when a load is applied to the fan motor (loaded) during the fan motor start-up process, which rotates in the reverse direction at a rotation speed of 348.7 rpm. Figure 4(b) shows an example of the current waveform of the U-phase current Iu when no load is applied to the fan motor (no load) during the fan motor start-up process. Both Figures 4(a) and 4(b) show the current waveform of the U-phase current Iu when the fan motor is rotated at a rotation speed of 200 rpm after the phase adjustment period (after start-up).

The "non-energized section" in FIG. 4 indicates the section in which the fan motor is in a non-energized state before starting. The "synchronous operation section" in FIG. 4 indicates the section for accelerating the fan motor to a rotation speed at which a sufficient induced voltage can be obtained. The "phase adjustment section" in FIG. 4 indicates the section for matching the phase difference between the γ-δ coordinate system and the d-q coordinate system. The "mode transition section" in FIG. 4 indicates the section in which the operation mode of the fan motor is transitioned from the synchronous operation mode to the vector control operation mode. The "normal operation section" in FIG. 4 indicates the section in which the fan motor is driven in the vector control operation mode by speed and torque control based on the mechanical angular velocity command value input from outside the motor control device. The horizontal axis in FIG. 4 indicates time [s], and the vertical axis in FIG. 4 indicates U-phase current [A]. Also, in FIG. 4, the passage of time is shown from left to right.

As shown in Figures 4(a) and 4(b), when comparing the magnitude of the current in the mode transition section after phase adjustment, even though the fan motor is controlled to rotate at the same rotational speed, the current amplitude of the U-phase current Iu is larger when the fan motor is under load (loaded state) than when the fan motor is not under load (unloaded state). Although not shown, the V-phase current and W-phase current flowing through the fan motor also have larger current amplitudes when the fan motor is under load than when it is unloaded, similar to the U-phase current Iu. Therefore, at least one of the U-phase current, V-phase current, and W-phase current in the mode transition section after phase adjustment can be detected, and the load on the fan motor can be detected based on the detected current.

As shown in FIG. 1, the motor control device 1 according to this embodiment has a load detection unit 92 in the load detection unit 90 that can detect the load applied to the fan motor M from the current flowing through the fan motor M. More specifically, the load detection unit 92 uses the amplitude of the U-phase current Iu input from the current detection circuit 21 to calculate the absolute value of the amplitude or the average value of the effective value of the U-phase current Iu. The load detection unit 92 uses the amplitude of the U-phase current Iu at the time when a predetermined time has elapsed during the mode transition period after phase adjustment in the startup process of the fan motor M to calculate the absolute value of the amplitude or the average value of the effective value. The load detection unit 92 also stores the absolute value of the amplitude of the U-phase current Iu or the average value of the effective value based on the amplitude in association with the value of the load applied to the fan motor M. The load detection unit 92 acquires the value of the load associated with the calculated average value and outputs the acquired load value to the control unit 80 as the load at the startup of the fan motor M.

As shown in Fig. 1, the motor control device 1 includes a ranking generation unit 81 that stores combinations of start-up voltages for starting the fan motor M and loads applied to the fan motor M, and generates a ranking of the start-up voltages based on the frequency of successful start-up of the fan motor M. The motor control device 1 also includes a start-up voltage selection unit 82 that selects a start-up voltage to be used during start-up processing of the fan motor M based on the load detected by the load detection unit 90 and the rankings generated by the ranking generation unit 81, and outputs a voltage command for the selected start-up voltage to the synchronous voltage setting unit 3 as a voltage command V ^* for the motor application voltage. The ranking generation unit 81 and the start-up voltage selection unit 82 are provided as functional blocks provided in the control unit 80, for example. Specific configurations of the ranking generation unit 81 and the start-up voltage selection unit 82 will be described below.

The ranking generation unit 81 converts a predetermined starting voltage into an index and manages it in order to generate a ranking of starting voltages based on the frequency of successful starting of the fan motor M. FIG. 5 is a graph showing an example of the correspondence between the indexes stored in the ranking generation unit 81 and the starting voltages. The horizontal axis of the graph in FIG. 5 indicates the index, and the vertical axis of the graph in FIG. 5 indicates the starting voltage. The starting voltages V0, V1, V2, V3, V4, V5, V6, V7, ..., Vx (x is 0 or a natural number) are each preset to a predetermined value. The starting voltages V0, V1, V2, V3, V4, V5, V6, V7, ..., Vx are associated with the indexes Id0, Id1, Id2, Id3, Id4, Id5, Id6, Id7, ..., Idx, respectively. In this embodiment, the starting voltages V0 to Vx are set so that the adjacent voltage values are equally spaced. For this reason, in this embodiment, the start-up voltages V0 to Vx and the indexes Id0 to Idx correspond to each other in a linear relationship. The start-up voltages V0 to Vx and the indexes Id0 to Idx are not limited to a linear correspondence, and may be associated in other ways as long as the start-up voltages and the indexes correspond to each other in a one-to-one relationship.

The ranking generation unit 81 also stores in advance multiple loads applied to the fan motor M, and holds the frequency of the startup voltage that successfully started the fan motor M for each of the multiple loads, for example in a matrix structure. Figure 6 is a diagram showing an example of the structure of the startup voltage frequency stored in combination with the load applied to the fan motor M.

As shown in FIG. 6, the ranking generating unit 81 stores, for example, loads L _-y , ..., L _-1 , L ₀ , L ₊₁ , ..., L _+y (y is 0 or a natural number) as loads applied to the fan motor M when the fan motor M is successfully started. The "load L _-y " shown in FIG. 6 indicates the maximum load at which the fan motor M rotates in the reverse direction. In other words, the "load L _-y " corresponds to the "maximum load" shown in FIG. 3. The "load L _+y " shown in FIG. 6 indicates the minimum load at which the fan motor M rotates in the forward direction. In other words, the "load L _+y " corresponds to the "minimum load" shown in FIG. 3. The "load L ₀ " shown in FIG. 6 indicates a state in which the fan motor M does not rotate, that is, no load. In other words, the "load L ₀ " corresponds to "0" shown in FIG. 3. The "load L _-1 " shown in FIG. 6 indicates a load at which the fan motor M rotates in the reverse direction, which is one level larger than no load. 6 indicates a load that rotates the fan motor M in the forward direction and is one level higher than no load. In this manner, the ranking generating unit 81 sets "y×2+ ₁ " loads as the loads applied to the fan motor M.

The ranking generation unit 81 associates the frequency (hereinafter sometimes referred to as "success frequency") of the start-up voltage at which the fan motor M was successfully started (hereinafter sometimes referred to as "successful start-up voltage") with the loads L _-y to L _+y , and stores the combination in an updateable manner. "SF _{_0} " in FIG. 6 indicates the success frequency at start-up voltage V0. "SF _{_1} " in FIG. 6 indicates the success frequency at start-up voltage V1. "SF _{_2} " in FIG. 6 indicates the success frequency at start-up voltage V2. "SF _{_x} " in FIG. 6 indicates the success frequency at start-up voltage Vx.

As shown in FIG. 6, the ranking generating unit 81 stores success frequencies SF _{_0} to SF _{_x} at startup voltages V0 to Vx for each load L _−y to L _+y in an updateable manner. In an initial state where the fan motor M has never been successfully started, a ranking is generated in advance in ascending order of startup voltage. When updating the success frequencies of the stored successful startup voltages, the ranking generating unit 81 updates any one of all success frequencies of the stored successful startup voltages based on the load value input from the startup load detecting unit 92 and the signal level of the output signal input from the comparator 72. When updating the success frequencies of the successful startup voltages, the ranking generating unit 81 also refers to the voltage command of the startup voltage stored in a predetermined storage area of the control unit 80. The voltage command of the startup voltage stored in a predetermined storage area of the control unit 80 is a voltage command of the acceleration voltage (details of which will be described later) output by the startup voltage selecting unit 82 to the synchronization voltage setting unit 3 at the start of a phase adjustment section (details of which will be described later) in the startup process of the fan motor M. When the ranking generating unit 81 determines that the signal level of the output signal input from the comparator 72 is a LOW level and the fan motor M has been successfully started (not out of step), it selects a load corresponding to the load value input from the starting load detecting unit 92 from among the loads L _-y to L _+y . The ranking generating unit 81 selects a starting voltage corresponding to the value of the voltage command of the starting voltage stored in a predetermined storage area of the control unit 80 from among the success frequencies SF _{_0} to SF _{_x} combined with the selected load, and increases the value of the success frequency at the selected starting voltage by 1. In this way, the ranking generating unit 81 updates the success frequencies SF _{_0} to SF _{_x} of the starting voltage during the starting process of the fan motor M. When the ranking generating unit 81 updates the success frequencies SF _{_0} to SF _{_x} , the control unit 80 erases the voltage command of the starting voltage stored in the predetermined storage area.

For example, assume that at the start of a phase adjustment period (details to be described later) in the startup process of the fan motor M, the startup of the fan motor M with a load L _+y applied thereto is successful by an acceleration voltage equivalent to the startup voltage Vx. In this case, the signal level of the output signal input from the comparator 72 becomes a LOW level, so the ranking generation unit 81 determines that the startup of the fan motor M is successful, and selects a load L _+y from among the loads L _-y to L _+y that is the same as the load value input from the startup load detection unit 92. Furthermore, the ranking generation unit 81 increases by 1 the value of the success frequency SFx corresponding to the startup voltage Vx among the success frequencies SF _{_0} to SF _{_x} combined with the selected load L _+y . In this way, the ranking generation unit 81 updates the success frequencies SF _{_0} to SF _{_x} of the startup voltages.

In the update process of the success frequencies SF _{_0} to SF _{_x} , if there is no load among the loads L _-y to L _+y that has the same value as the load input from the startup load detection unit 92, the ranking generation unit 81 selects from the loads L _-y to L _+y a load that has a value closest to the load value input from the startup load detection unit 92. In addition, in the update process of the success frequencies SF _{_0} to SF _{_x} , if there is no startup voltage among the startup voltages V0 to Vx that has the same value as the voltage command for the startup voltage stored in a predetermined storage area of the control unit 80, the ranking generation unit 81 selects from the startup voltages V0 to Vx a startup voltage that has a value closest to the value of the voltage command.

Incidentally, the control unit 80 may have an upper limit on the capacity of the storage area. In this case, the ranking generation unit 81 may set a limit value on the values that can be set as the success frequencies SF _{_0} to SF _{_x} . For example, when a load that reaches the limit value occurs among the success frequencies SF _{_0} to SF _{_x} stored in combination with any of the loads L _-y to L _+y , the ranking generation unit 81 may reduce (for example, _halve ) the values of all the success frequencies SF _{_0} to SF _{_x} combined with the load by a predetermined value. Furthermore, the ranking generation unit 81 may adjust only the success frequencies SF _{_0} to SF _{_x} corresponding to the load combined with the success frequency that reaches the limit value among the loads L -y to L ₊ y. Furthermore, the ranking generation unit 81 may adjust all the stored success frequencies SF _{_0} to SF _{_x} when a success frequency that reaches the limit occurs.

In this way, the ranking generation unit 81 updates any one of all the set success frequencies SF_0 to _{SF_x} when it determines that the fan motor M has been successfully started based on the signal level of the output signal input from the comparator 72. On the other hand, when the ranking generation unit 81 determines that the fan motor M has not been successfully started (out-of-step state) based on the signal level of the output signal input from the _comparator 72, it does not update any of the success frequencies _{SF_0} to _{SF_x} even if a load value is input from the starting load detection unit 92.

When the ranking generation unit 81 updates the success frequencies _{SF_0} to _{SF_x} , it also updates the ranking of the successful start-up voltages. To update the ranking of the successful start-up voltages, the ranking generation unit 81 updates a histogram that represents the successful start-up voltages as indexes, and updates the ranking of the indices using the updated histogram. Since the indexes are associated with the start-up voltages (see FIG. 5), the ranking of the start-up voltages that successfully started the fan motor can be updated by updating the ranking of the indices based on the histogram.

Fig. 7 is a diagram showing an example of a histogram in which starting voltages V0 to Vx that successfully started the fan motor M are represented by indexes Id1 to Idx. The histogram is generated by a ranking generation unit 81. The ranking generation unit 81 generates the histogram by linking it to each of the loads L _-y to L _+y (see Fig. 6) stored in advance. The horizontal axis of the histogram shown in Fig. 7 indicates the indexes Id0 to Idx, and the vertical axis of the histogram shown in Fig. 7 indicates the frequency of successful start voltages (i.e., success frequency).

When the ranking generation unit 81 updates the success frequency, it selects a load combined with the updated success frequency from among the loads L _-y to L _+y , and increases by 1 the frequency of the index representing the start-up voltage corresponding to the updated success frequency among the indexes Id0 to Idx of the histogram linked to the selected load. This allows the ranking generation unit 81 to update the histogram linked to the load combined with the updated success frequency. For example, when the success frequency SF _{_4} combined with the load L _+y is updated, the ranking generation unit 81 selects the load L _+y , and increases by 1 the frequency of the index Id4 corresponding to the start-up voltage V4 among the indexes Id0 to Idx of the histogram linked to the selected load L ₊ y. In this way, the ranking generation unit 81 can update the histogram linked to the selected load L _+y .

The ranking generating unit 81 generates a ranking of the starting voltages V0 to Vx that successfully start the fan motor M using the indexes Id1 to Idx based on a histogram in which the starting voltages V0 to Vx that successfully start the fan motor M are represented by the indexes Id1 to Idx. FIG. 8 is a diagram in which the ranking generating unit 81 generates a ranking of the success frequency of the starting voltages V0 to Vx that successfully start the fan motor M using the indexes Id1 to Idx. The ranking generating unit 81 generates the ranking for each of the loads L _−y to L _+y (see FIG. 6) that are stored in advance. The horizontal axis in FIG. 8 indicates the frequency of the starting success voltage (i.e., the success frequency), and the vertical axis in FIG. 8 indicates the indexes Id0 to Idx. FIG. 8 also shows the ranking based on the histogram shown in FIG. 7.

As shown in FIG. 8, the ranking generation unit 81 uses a histogram represented by the indexes Id1 to Idx to rearrange the indexes Id1 to Idx in descending order of success frequency to generate a ranking of the startup voltages V0 to Vx that successfully started the fan motor M. For indexes with the same success frequency, the ranking generation unit 81 ranks the index with the smaller startup voltage higher. For example, if the success frequencies of indexes Id1 and Id2 are the same, the ranking generation unit 81 ranks index Id1, which is associated with a lower startup voltage, higher than index Id2 (see FIG. 5).

In this way, the ranking generation unit 81 can rank the starting voltages with a high probability of successfully starting the fan motor M for each load L _-y to L _+y at the time of starting the fan motor M. In addition, the ranking generation unit 81 can update the ranking of successful start-up voltages every time the start-up of the fan motor M is successful.

As will be described in detail later, the motor control device 1 can use the ranking of start-up voltages generated by the ranking generation unit 81 to start the fan motor M at a start-up voltage that is predicted to be the minimum required depending on the load applied to the fan motor M when the fan motor M is started. This allows the motor control device 1 to improve energy conservation when starting the fan motor M.

Next, the start-up voltage selection unit 82 that selects the start-up voltage used during the start-up process of the fan motor M based on the ranking of the start-up voltages generated by the ranking generation unit 81 will be described. The start-up voltage selection unit 82 calculates the load (hereinafter, sometimes referred to as the "pre-start load") applied to the fan motor M before starting the fan motor M based on the idling direction and the idling rotation speed input from the rotation detection unit 91 (see FIG. 1) provided in the load detection unit 90. The start-up voltage selection unit 82 stores a correspondence relationship between the pre-start load of the fan motor M and the loads L _-y to L _+y at the time of successful start-up of the fan motor M. Based on this correspondence relationship, the start-up voltage selection unit 82 determines the load at the time of successful start-up corresponding to the calculated pre-start load from among the loads L _-y to L _+y . The start-up voltage selection unit 82 refers to the ranking of the start-up voltages associated with the loads determined from among the loads L _-y to L _+y , and selects an index that is ranked higher. The start-up voltage selection unit 82 selects a start-up voltage corresponding to the selected index based on the correspondence between the indexes and the start-up voltages stored in the ranking generation unit 81. Although details will be described later, the start-up voltage selected by the start-up voltage selection unit 82 is used as an acceleration voltage for accelerating the fan motor M during the start-up process of the fan motor M.

In this way, the start-up voltage selection unit 82 selects a higher ranked start-up voltage. This allows the start-up voltage selection unit 82 to select a start-up voltage associated with an index that has a high success frequency for the load applied to the fan motor M before the fan motor M starts to start (i.e., immediately before the start-up starts). This allows the motor control device 1 to start the fan motor M with the minimum necessary start-up voltage that has a high probability of successful start-up, depending on the load applied to the fan motor M.

The start-up voltage selection unit 82 outputs the selected voltage command for the start-up voltage as a voltage command V ^* for the motor application voltage to the synchronous voltage setting unit 3. The voltage command V ^* for the motor application voltage input from the start-up voltage selection unit 82 is input to a fixed voltage output unit 41 of a voltage output unit 40 provided in the synchronous voltage setting unit 3.

<Processing in the motor control device>
Next, an example of a processing procedure of the motor control device 1 when starting the fan motor M will be described with reference to FIGS. 1 and 5 to 8 as well as the flowcharts shown in FIGS.

When the motor control device 1 shown in FIG. 1 starts to start the fan motor M, as shown in FIG. 9, in step S1, the load applied to the fan motor M (see FIG. 1) before the start of the fan motor M (i.e., immediately before the start of the fan motor M) is detected, and the process proceeds to step S2. Here, "before the start of the fan motor M (i.e., immediately before the start of the fan motor M)" refers to a period after the motor control device 1 is powered on and before a drive signal is input to the fan motor M. In step S1, for example, the control unit 80 (see FIG. 1) detects the load applied to the fan motor M immediately before the start of the fan motor M based on the rotation direction and the number of rotations of the fan motor M input from the rotation detection unit 91 (see FIG. 1) provided in the load detection unit 90 immediately before the start of the fan motor M. The control unit 80, for example, activates the start voltage selection unit 82 (see FIG. 1) to detect which of the loads L _-y to L _+y (see FIG. 6) the load applied to the fan motor M immediately before the start of the fan motor M corresponds to. The control unit 80 also stores the detected load value in a predetermined storage area.

Next, in step S2, the start-up voltage selection unit 82 selects a start-up voltage and proceeds to processing in step S3. The start-up voltage selection unit 82 selects a start-up voltage based on the load detected in step S1, the ranking of start-up voltages generated by the ranking generation unit 81 (see FIG. 8), and the correspondence between the start-up voltage and the index stored in the ranking generation unit 81 (see FIG. 5). The control unit 80 stores the value of the start-up voltage selected by the start-up voltage selection unit 82 in a specified memory area.

Next, in step S3, the control unit 80 determines the idling direction of the fan motor M based on the input from the rotation detection unit 91. If the control unit 80 determines that the fan motor M is not rotating forward (reversely), (No), it proceeds to processing in step S4. On the other hand, if the control unit 80 determines that the fan motor M is rotating forward (Yes), it proceeds to processing in step S5 without executing processing in step S4.

Next, in step S4, the reverse rotation start-up process is executed, and the process proceeds to step S5. In the reverse rotation start-up process, the synchronous operation of the fan motor M is controlled while the fan motor M continues to rotate in reverse, the phase of the fan motor M is stabilized, and then the fan motor M is caused to operate in reverse. The detailed processing of the reverse rotation start-up process will be described later.

Next, in step S5, the normal rotation startup process is executed, and the process proceeds to step S6. In the normal rotation startup process, the synchronous operation of the fan motor M is controlled while maintaining normal rotation, and the phase of the fan motor M is stabilized. The detailed processing of the normal rotation startup process will be described later.

Next, in step S6, the control unit 80 executes an out-of-step determination, and proceeds to processing in step S7. As described above, the control unit 80 determines whether the fan motor M is out of step using the signal level of the output signal of the out-of-step determination unit 70 (see FIG. 1), which is based on the comparison result between the voltage of the amplitude signal based on the amplitude of the U-phase current Iu input from the current detection circuit 21 (see FIG. 1) and the threshold voltage Vth.

Next, in step S7, the control unit 80 determines whether or not the fan motor M has been successfully started. If the control unit 80 determines in step S6 that the fan motor M is not out of step, it determines that the fan motor M has been successfully started (Yes) and proceeds to processing in step S8. On the other hand, if the control unit 80 determines in step S6 that the fan motor M is out of step, it determines that the fan motor M has not been successfully started (No) and proceeds to processing in step S12.

Next, in step S8, the control unit 80 controls the ranking generation unit 81 (see FIG. 1) to detect the load when the fan motor M was successfully started, and proceeds to the process of step S9. Specifically, in step S8, the ranking generation unit 81 detects a load from among the loads L _-y to L _+y that corresponds to the load value input from the starting load detection unit 92 (see FIG. 1) provided in the load detection unit 90.

Next, in step S9, the control unit 80 controls the ranking generation unit 81 to execute processing such as updating the histogram in which the successful start-up voltage is represented by an index, and proceeds to processing in step S10. If it is determined in step S7 that the start-up is successful, the start-up voltage selected in step S2 becomes the successful start-up voltage at which the fan motor M is successfully started. Therefore, in step S9, the ranking generation unit 81 updates the value of the success frequency corresponding to the start-up voltage selected in step S2 among the success frequencies SF _{_0} to SF _{_x} combined with the loads detected in step S8 from among the loads L _-y to L ₊ y. In addition, the ranking generation unit 81 updates the histogram of the index associated with the loads detected in step S8 from among the loads L _-y to L _+y . In addition, the ranking generation unit 81 updates the ranking of the success frequencies of the successful start-up voltages generated from the updated histogram.

Next, in step S10, the control unit 80 transitions the operation mode of the fan motor M from an operation mode in which the rotor position is not estimated (synchronous operation mode) to an operation mode in which the rotor position is estimated (vector control operation mode (hereinafter sometimes referred to as "vector control mode")), and drives the fan motor M in the vector control mode. After driving the fan motor M in the vector control mode, the control unit 80 transitions to the processing of step S11.

Next, in step S11, the control unit 80 continues driving in the vector control mode in step S10 and performs normal operation by driving the fan motor M with vector control. This ends the start-up process of the fan motor M executed by the motor control device 1.

On the other hand, if it is determined that the fan motor M has not been successfully started (No in step S7), in step S12, the control unit 80 increments the startup process count, which is the number of times the startup process is repeated until the startup of the fan motor M is successful and is stored in a specified memory area, by 1, and proceeds to step S13. The startup process count is stored in a specified memory area of the control unit 80.

Next, in step S13, the control unit 80 determines whether the number of startup processes updated in step S12 is equal to or less than the maximum number of times to repeat the startup process of the fan motor M. The control unit 80 presets a maximum number of times (maximum number) that the startup process can be executed again if startup of the fan motor M fails. If the control unit 80 determines that the number of startup processes updated in step S12 is equal to or less than the preset maximum number (Yes), it proceeds to processing of step S14. On the other hand, if the control unit 80 determines that the number of startup processes updated in step S12 is not equal to or less than the preset maximum number (greater than the maximum number) (No), it proceeds to processing of step S16.

Next, in step S14, the control unit 80 selects an index of a ranking with the same number as the number of startup processes updated in step S12 (for example, the second index if the startup is the second time), and proceeds to processing in step S15. Specifically, the control unit 80 acquires a ranking of the success frequency of successful startup voltages generated based on a histogram of indexes linked to loads detected from among the loads L _-y to L _+y in step S8. The control unit 80 selects an index of a ranking with the same number as the number of startup processes updated in step S12 from the acquired rankings. The startup voltage selection unit 82 selects a startup voltage associated with the index selected by the control unit 80 from among the startup voltages V0 to Vx, and updates the value of the startup voltage stored in a predetermined storage area to the value of the selected startup voltage.

Next, in step S15, the control unit 80 determines whether or not the fan motor M was rotating in the forward direction immediately before the start of the fan motor M. If the load linked to the ranking acquired in step S14 is any of the loads L ₀ to L _+y , the control unit 80 determines that the fan motor M was rotating in the forward direction (Yes), and proceeds to the process of step S5. As a result, the motor control device 1 executes the forward rotation startup process (step S5) using the startup voltage set in step S14, and starts the fan motor M again.

On the other hand, if the load linked to the ranking acquired in step S14 is any one of the loads L _-y to L _-1 , the control unit 80 determines that the fan motor M was not rotating in the forward direction (No), and proceeds to the process of step S4. As a result, the motor control device 1 executes the reverse rotation start-up process (step S4) using the start-up voltage set in step S13, and starts the fan motor M again.

In this way, the control unit 80 (more specifically, the start-up voltage selection unit 82) changes and selects the start-up voltage based on the ranking when the start-up of the fan motor M fails, and attempts to restart the fan motor M. If the restart of the fan motor M is determined to be successful in step S7, the control unit 80 proceeds to the process of step S8. In addition, the ranking generation unit 81 resets the number of start-up processes stored in a specified memory area in step S9.

If it is determined in step S13 that the number of startup processes is greater than a preset maximum number of times, in step S16, the control unit 80 determines that the fan motor M is faulty because the fan motor M has not been successfully started even after repeating the startup process of the fan motor M the maximum number of times. The control unit 80 issues a fault notification, such as by generating an alarm, and ends the startup process of the fan motor M.

Next, an example of the reverse rotation start process (step S4) in the start-up process of the fan motor M will be described with reference to FIG. 10.

10, when the reverse rotation start-up process is started, first, in step S41, synchronous operation in the reverse direction (hereinafter, sometimes referred to as "reverse rotation synchronous operation") is started, and the process proceeds to step S42. In step S41, the control unit 80 sets to initial values the voltage value of the reverse rotation start-up voltage Vgs ^* (see FIG. 13) for starting rotation of the fan motor M in the reverse direction, the value of the reverse rotation start-up rotation speed ω ^* ges (see FIG. 13), and the like.

Next, in step S42, the fan motor M is operated in reverse synchronous operation, and the process proceeds to step S43. In the reverse synchronous operation in step S42, the control unit 80 drives the fan motor M so that the reverse rotation start voltage Vgs ^* converges to the acceleration voltage V ^* gh (see FIG. 13) during the reverse synchronous operation. The start voltage selection unit 82 outputs the voltage command of the start voltage selected in step S2 or step S14 to the synchronous voltage setting unit 3 (see FIG. 1) as the voltage command of the acceleration voltage V ^* gh during the reverse rotation during the reverse synchronous operation. Also, the control unit 80 drives the fan motor M so that the reverse rotation start rotation speed ω ^* ges converges to the acceleration rotation speed ω ^* geh during the reverse rotation.

The reverse synchronous operation in step S42 is performed for a predetermined time T2g (see FIG. 13) that is determined in advance by experiment. After the reverse synchronous operation starts, the control unit 80 monitors whether the elapsed time has reached the predetermined time T2g, and constantly determines whether the current time is within the reverse synchronous operation section T12. If the control unit 80 determines that the current time is within the reverse synchronous operation section T12, it continues the reverse synchronous operation. On the other hand, if the control unit 80 determines that the current time is not within the reverse synchronous operation section T12, it determines that the predetermined time has elapsed (i.e., the elapsed time has reached the predetermined time T2g), ends the reverse synchronous operation, and proceeds to step S43.

Next, in step S43, the control unit 80 executes a phase adjustment process, and proceeds to the process of step S44. In step S43, the control unit 80 controls the fan motor ^M so that the rotation speed converges from the acceleration rotation speed ω ^* geh to the rotation speed ωe' (see FIG. 1) at which the γ-axis current Iγ can be made zero, while maintaining the acceleration voltage Vgh*.

The phase adjustment process in step S43 is performed for a predetermined time T3g (see FIG. 13) that is determined in advance by experiment. The control unit 80 monitors whether the elapsed time has reached the predetermined time T3g, and constantly determines whether the current time is within the phase adjustment interval T13. If the control unit 80 determines that the current time is within the phase adjustment interval T13, it continues the phase adjustment process. On the other hand, if the control unit 80 determines that the current time is not within the phase adjustment interval T13, it determines that the predetermined time has elapsed (i.e., the elapsed time has reached the predetermined time T3g), ends the phase adjustment process, and proceeds to step S44.

Next, in step S44, the control unit 80 transitions the operation mode of the fan motor M from the synchronous operation mode to the vector control mode, controls the fan motor M to rotate at a constant rotation speed, and transitions to processing in step S45. As the control unit 80 controls the fan motor M to rotate at a constant rotation speed, it also controls the motor applied voltage to be constant.

Next, in step S45, the control unit 80 executes synchronous operation (hereinafter sometimes referred to as "reverse synchronous operation") to reverse the rotation direction of the fan motor M from the reverse direction to the forward direction, and proceeds to the processing of step S5 (see FIG. 9). Specifically, the control unit 80 controls the fan motor M to gradually decelerate the rotation speed, reverse the rotation direction from the reverse direction to the forward direction, and perform synchronous operation in the forward direction. This ends the reverse rotation start-up process.

Next, an example of the normal rotation start process (step S5) in the start-up process of the fan motor M will be described with reference to FIG. 11.

As shown in Fig. 11, when the normal rotation start-up process is started, first, in step S51, synchronous operation in the normal rotation direction (hereinafter, sometimes referred to as "normal rotation synchronous operation") is started, and the process proceeds to step S52. In step S51, which is executed following the process of step S45 (see Fig. 10), the control unit 80 continues the normal rotation synchronous operation in step S45 (see Fig. 10). On the other hand, in step S51, which is executed following the process of step S3 (see Fig. 9), the control unit 80 sets the voltage value of the normal rotation start-up voltage Vs ^* (see Fig. 12) and the value of the normal rotation start-up rotation speed ω ^* es (see Fig. 12) to initial values, which are used to start the fan motor M in the normal rotation direction.

Next, in step S52, the fan motor M is operated in forward rotation synchronous operation, and the process proceeds to step S53. In the forward rotation synchronous operation in step S52, the control unit 80 drives the fan motor M so that the start-up voltage during forward rotation converges to the acceleration voltage. In step S52, which is executed after the process of step S45, the control unit 80 outputs a predetermined voltage command, which is set in advance as a voltage command for the acceleration voltage V ^* sh (see FIG. 13) during forward rotation after the reverse synchronization operation, to the synchronization voltage setting unit 3. Furthermore, the control unit 80 drives the fan motor M so that the start-up rotation speed ω ^* ses during forward rotation after the reverse synchronization operation converges to the acceleration rotation speed ω ^* seh (see FIG. 13).

On the other hand, in step S52 executed after the processing of step S3 without the processing of step S45, the start-up voltage selection unit 82 outputs the voltage command of the start-up voltage selected in step S2 or step S14 as the voltage command of the acceleration voltage V ^* h (see FIG. 12) during forward rotation in forward rotation synchronous operation to the synchronization voltage setting unit 3. Furthermore, the control unit 80 drives the fan motor M so that the start-up rotation speed ω ^* es during forward rotation converges to the acceleration rotation speed ω ^* eh (see FIG. 12).

The forward rotation synchronous operation control in step S52 is performed for a predetermined time T2s (see FIG. 12) that is determined in advance by an experiment. The control unit 80 monitors whether the elapsed time reaches the predetermined time T2s. When the elapsed time after the start of the forward rotation synchronous operation reaches the predetermined time T2s, the control unit 80 determines that the drive voltage of the fan motor M has converged to the acceleration voltage V ^* h and the rotation speed of the fan motor M has converged to the acceleration rotation speed ω ^* eh, ends the forward rotation synchronous operation, and proceeds to step S53.

The phase adjustment process in step S53 is performed for a predetermined time T3s (see FIG. 12) that is determined in advance by experiment. The control unit 80 monitors whether the elapsed time has reached the predetermined time T3s, and when the elapsed time after the start of the phase adjustment process reaches the predetermined time T3s, it determines that the phase adjustment has ended and proceeds to step S6 for out-of-step determination.

<Operation when fan motor M starts from normal rotation>
<Operation when startup is successful>
Next, an example of the operation when starting the fan motor M during normal start-up, i.e., when the outdoor unit fan is not rotating in reverse, will be described with reference to Fig. 12. Fig. 12 is a diagram showing the change in the rotation speed [rad/s] of the fan motor M and the voltage command V ^* of the motor applied voltage V [V] from before start-up to the transition to normal operation, with the horizontal axis showing time. As shown in Fig. 12, the operation sections of the fan motor M are divided into a non-energized section T1 where the processes of steps S1 to S3 are performed, a forward rotation synchronous operation section T2 where the processes of steps S51 and S52 are performed, a phase adjustment section T3 where the process of step S53 is performed, a step-out determination section T3' where the process of step S6 is performed, a mode transition section T4 where the process of step S10 is performed, and a normal operation section T5 where the process of step S11 is performed.

In the de-energized section T1, the fan motor M is in a de-energized state before startup, and the rotation detection unit 91 detects the idling direction and idling speed. In the case of FIG. 12, it is determined that the fan motor M is rotating in the forward direction based on the detected idling direction and idling speed, and the operation section of the fan motor M transitions from the de-energized section T1 to the forward rotation synchronous operation section T2.

In the forward rotation synchronous operation section T2, in order to accelerate the fan motor M to a rotation speed at which sufficient induced voltage is obtained, the rotation of the fan motor M is accelerated while increasing the motor applied voltage V and the rotation speed, and the rotation speed is increased over time.

The fan motor M is driven, for example, so that the rotation speed converges from the startup rotation speed ω ^* es to the acceleration rotation speed ω ^* eh during a time T2s, and specifically, is driven so that the rotation speed changes according to the characteristics expressed by the following equation (7).

The time T2s, the startup rotation speed ω ^* es, and the acceleration rotation speed ω ^* eh are predetermined values that are determined in advance by tests, etc. The time T2s indicates the elapsed time from the start of the forward rotation synchronous operation section T2, that is, from the start of the supply of current to the fan motor M.

Also, the fan motor M is driven so that the motor applied voltage V converges from the start-up voltage Vs ^* to the acceleration voltage Vh ^* during the time T2s, specifically, so as to increase linearly. In the forward rotation synchronous operation section T2, the start-up voltage selection section 82 outputs the voltage command of the start-up voltage selected in the non-energized section T1 to the synchronous voltage setting section 3 as the voltage command of the acceleration voltage V ^* h during forward rotation. Therefore, the acceleration voltage V ^* h has a different value depending on the idling speed of the fan motor M detected in the non-energized section T1, that is, the load applied to the fan motor M in the non-energized section T1. As a result, the motor control device 1 can start the fan motor M with a start-up voltage predicted to be the minimum required depending on the load applied to the fan motor M when the fan motor M is started, thereby improving energy saving.

When the fan motor M is accelerated to, for example, a target value, the phase adjustment section T3 begins.
In the phase adjustment section T3, the rotation speed is adjusted according to the current load state with respect to the acceleration voltage Vh ^* reached in the forward rotation synchronous operation section T2, thereby matching the phase difference between the γ-δ coordinate system and the d-q coordinate system. In other words, the fan motor M is controlled so that the rotation speed converges from the acceleration rotation speed ω ^* eh to the rotation speed ωe' that can make the γ-axis current Iγ zero during the time T3s while ^the motor applied voltage V maintains the acceleration voltage Vh*. The time T3s is set to, for example, the time required for the γ-axis current Iγ to converge to zero.

In the following out-of-step determination section T3', an out-of-step determination is performed. Note that in the out-of-step determination section T3', drive control of the fan motor M continues in the phase adjustment section T3 until out-of-step is determined.

When the fan motor M is started normally, the amplitude of the U-phase current Iu in the phase adjustment section T3 gradually decreases, so that the amplitude of the U-phase current Iu becomes smaller than the threshold value. Therefore, as a result of the out-of-step determination, it is determined that the fan motor has started normally, and a mode transition is performed. Before the mode transition is started, in the histogram change process (step S9) shown in FIG. 9, the ranking generation unit 81 performs a process of updating the ranking of successful start-up voltages, etc.

In mode transition section T4, the mode transitions from synchronous operation mode to vector control mode, and the fan motor M is controlled to rotate at a constant speed, and accordingly the motor applied voltage V is also controlled to be constant.

Then, in the subsequent normal operation section T5, the fan motor M is driven in vector control mode by speed and torque control based on the mechanical angular velocity command value ωm_ref input from outside the motor control device 1.

<Action when startup fails>
On the other hand, when the fan motor M is not started normally (i.e., when the fan motor M fails to start), the amplitude of the U-phase current Iu in the phase adjustment section T3 does not decrease. Therefore, in the out-of-step determination section T3', the amplitude of the U-phase current is equal to or greater than the threshold value, and it is determined that the fan motor M has failed to start. Since the fan motor M has failed to start, its drive is stopped, and both the motor applied voltage V and the rotation speed converge to zero, and the section transitions to the non-energization section T1.

Since startup has failed, the startup conditions are changed and restart is attempted, transitioning from the non-energized section T1 to the forward rotation synchronous operation section T2, and synchronous operation is started in the same manner as above. During restart, the process of step S14 shown in FIG. 9 is executed, and the startup voltage (i.e., acceleration voltage) is selected again based on the ranking of successful startup voltages.

Then, when the motor moves from the forward rotation synchronous operation section T2 to the phase adjustment section T3 and restart fails in the out-of-step determination section T3', the start-up conditions are changed and restart is attempted. If start-up fails even after driving with the start-up conditions changed a predetermined number of times, the process of step S16 shown in FIG. 9 is executed and a fault notification is issued indicating that the fan motor M has failed. This allows the user to recognize that the fan motor M has failed.

<Operation when fan motor M starts from reverse synchronous operation>
<Operation when startup is successful>
Next, an example of the operation when the outdoor unit fan starts the fan motor M from a reverse rotation state will be described with reference to Fig. 13. Fig. 13 is a diagram showing the change in the rotation speed [rad/s] of the fan motor M and the voltage command V ^* of the motor applied voltage V [V] from before the start to the transition to normal operation, with the horizontal axis showing time. As shown in Fig. 13, the operation sections of the fan motor M are divided into a non-energized section T11 where the processes of steps S1 to S3 are performed, a reverse synchronous operation section T12 where the processes of steps S41 and S42 are performed, a phase adjustment section T13 where the process of step S43 is performed, a mode transition section T14 where the process of step S44 is performed, a reverse synchronous operation section T15 where the process of step S45 is performed, a forward synchronous operation section T16 where the processes of steps S51 and S52 are performed, a phase adjustment section T17 where the process of step S53 is performed, a step-out determination section T17' where the process of step S6 is performed, a mode transition section T18 where the process of step S10 is performed, and a normal operation section T19 where the process of step S11 is performed. Further, the inverted synchronized operation section T15 includes a deceleration operation section T15a and a transition synchronized operation section T15b.

In the non-energized section T11, the fan motor M is in a non-energized state before start-up, and the rotation detection unit 91 detects the idling direction and idling rotation speed. In the case of FIG. 13, it is determined that the fan motor M is rotating in the reverse direction based on the detected idling direction and idling rotation, and the operation section of the fan motor M transitions from the non-energized section T11 to the reverse synchronous operation section T12.

In the reverse synchronous operation section T12, the fan motor M is driven, for example, during time T2g, so that the rotation speed converges from the start rotation speed ω ^* ges during reverse rotation to the acceleration rotation speed ω ^* geh, and more specifically, is driven so that it changes according to the characteristics expressed by the following equation (8).

The time T2g, the start-up rotation speed ω ^* ges during reverse rotation, and the acceleration rotation speed ω ^* geh are predetermined values determined in advance by tests, etc. The time T2s indicates the elapsed time from the start of the reverse synchronous operation section T12, that is, from the time when the supply of current to the fan motor M is started.
Also, the fan motor M is driven so that the motor applied voltage V converges from the start-up voltage Vgs ^* during reverse rotation to the acceleration voltage V ^* gh during the time T2g, specifically, so as to decrease linearly. In the reverse rotation synchronous operation section T12, the start-up voltage selection section 82 outputs the voltage command of the start-up voltage selected in the non-energized section T11 to the synchronous voltage setting section 3 as the voltage command of the acceleration voltage V ^* gh during reverse rotation. Therefore, the acceleration voltage V ^* gh has a different value depending on the idling speed of the fan motor M detected in the non-energized section T11, i.e., the load applied to the fan motor M in the non-energized section T11. As a result, the motor control device 1 can start the fan motor M with a start-up voltage predicted to be the minimum required depending on the load applied to the fan motor M when the fan motor M is started, thereby improving energy saving.

When the fan motor M is accelerated to, for example, a target value, the phase adjustment section T13 begins.
In the phase adjustment section T13, similarly to the phase adjustment section T3 in the case of starting from forward rotation, the rotation speed is adjusted according to the current load state with respect to the acceleration voltage V ^* gh reached in the synchronous operation section in reverse rotation, thereby matching the phase difference between the γ-δ coordinate system and the d-q coordinate system. In other words, the fan motor M is controlled so that the rotation speed converges from the acceleration rotation speed ω ^* gh to the rotation speed ωe' that can make the γ-axis current Iγ zero during the time T13s while the motor applied voltage V is maintained at the acceleration voltage V ^* gh. The time T13s is set to, for example, the time required for the γ-axis current Iγ to converge to zero.

In the following mode transition section T14, the operation mode transitions from synchronous operation mode to vector control operation mode, and the fan motor M is controlled to rotate at a constant rotation speed, and accordingly the motor applied voltage V is also controlled to be constant.

Then, in the subsequent reverse synchronous operation section T15, for example, in the deceleration operation section T15a, when the rotation speed of the fan motor M at the time when the mode transition section T14 ends is the synchronous start start rotation speed ω ^* gd, the rotation speed is driven so as to converge from the synchronous start start rotation speed ω ^* gd to the deceleration rotation speed ω ^* geg. Also, when the voltage of the d-axis at the time when the mode transition section T14 ends is the synchronous start start voltage V ^* gd, the motor applied voltage V is driven so as to decelerate from the synchronous start start voltage V ^* gd to the deceleration voltage V ^* geg. In the subsequent transition synchronous operation section T15b, the fan motor M is driven so that the rotation speed of the fan motor M converges from the deceleration rotation speed ω ^* geg to the start start rotation speed ω ^* ses during time T5g'. Also, the motor applied voltage V is driven so as to converge from the deceleration voltage V ^* geg to the start start voltage V ^* sh during time T5g'. At this time, in the deceleration operation section T15a, the motor is driven so that the rotation speed converges from the synchronous start-up rotation speed ω ^* gd to the start-up rotation speed ω ^* ses during time T5g, and converges from the deceleration rotation speed ω ^* geg to the start-up rotation speed ω ^* ses during time T5g'. Similarly, in the deceleration operation section T15a, the motor applied voltage V converges from the synchronous start-up voltage V ^* gd to the start-up voltage V ^* sh during time T5g, and converges from the deceleration voltage V ^* geg to the start-up voltage V ^* sh during time T5g'.

The subsequent forward rotation synchronized operation section T16 is controlled in the same manner as the forward rotation synchronized operation section T2 when started from forward rotation, and thereafter, the phase adjustment section T17, out-of-step determination section T17', mode transition section T18, and normal operation section T19 are controlled in the same manner as the phase adjustment section T3, out-of-step determination section T3', mode transition section T4, and normal operation section T5, respectively, when started from forward rotation.
That is, in the case of Fig. 11, after the transition to forward rotation, the fan motor M is successfully started, so in the out-of-step determination section T17', it is determined that the start is successful, and the mode is then changed. Before the mode change is started, in the histogram change process (step S9) shown in Fig. 9, the ranking generation unit 81 executes a process of updating the ranking of successful start-up voltages, etc. Then, operation in the vector control mode is performed.

<Action when startup fails>
On the other hand, when the fan motor M is not started normally (i.e., when the fan motor M fails to start), the amplitude of the U-phase current Iu in the phase adjustment section T17 does not decrease. Therefore, in the out-of-step determination section T17', the amplitude of the U-phase current is equal to or greater than the threshold value, and it is determined that the fan motor M has failed to start. Since the fan motor M has failed to start, its drive is stopped, the motor applied voltage V and the rotation speed both become zero, and the section transitions to the non-energization section T11.

Since startup has failed, fan motor M is restarted from reverse synchronous operation. During restart, the process of step S14 shown in FIG. 9 is executed, and the startup voltage (i.e., acceleration voltage) is selected again based on the ranking of successful startup voltages. If startup fails every time the startup conditions are changed a predetermined number of times and startup is attempted, the process of step S16 shown in FIG. 9 is executed, and a notification is issued that fan motor M has failed. This allows the user to recognize that fan motor M has failed.

＜Effects＞
As described above, the motor control device 1 stores the combination of the load and the startup voltage when the fan motor M is successfully started, selects a startup voltage that is predicted to be the minimum required from the combination of the load and the startup voltage based on the pre-start load of the fan motor M, and starts the fan motor M with the selected startup voltage. This allows the motor control device 1 to prevent starting the fan motor M with a startup voltage that exceeds the startup voltage required to start the fan motor M, thereby improving energy conservation.

Furthermore, the motor control device 1 performs a step-out determination at start-up, and performs this step-out determination based on the current waveform of the U-phase, which is one of the phase currents supplied to the fan motor M after phase adjustment. Therefore, it is possible to determine whether the rotating magnetic field and the rotor are synchronized without providing a sensor that detects the rotor position of the fan motor M. Therefore, even when a sensorless synchronous motor is used, the fan motor M can be started more reliably.
In addition, when it is determined that the start-up of the fan motor M has failed, restart is attempted multiple times with different start-up conditions, thereby increasing the probability of successful start-up, and when start-up fails even after multiple attempts with different start-up conditions, it is determined that the fan motor M has failed, so that failure of the fan motor M can be detected by software.
In addition, by stopping the driving of the fan motor M when it is determined that the fan motor M has failed, it is possible to stop the fan motor M at an earlier stage than when the failure of the fan motor M is detected using hardware.

<Modification>
In the above embodiment, the case where the out-of-step determination is performed only by the phase adjustment after the forward rotation synchronous operation has been described, but the present invention is not limited to this, and the out-of-step determination may also be performed in the phase adjustment after the reverse rotation synchronous operation. Specifically, the out-of-step determination may be performed in the phase adjustment section T13.
In addition, in the above embodiment, when it is determined that startup has failed, one of the conditions, the startup voltage V ^* s, the startup rotation speed ω ^* es, and the voltage rise slope VF, is changed depending on the number of failures. However, it is also possible to change more than one of these.
In the above embodiment, the case has been described where the drive control is performed so that the rotation speed and the motor applied voltage V change at the time of start-up as shown in Figures 12 and 13. However, the present invention is not limited to this, and any drive method in which phase adjustment is performed when starting the fan motor M can be applied.

The motor control device 1 according to the above embodiment is configured to use the amplitude of the U-phase current Iu when a predetermined time has elapsed during the mode transition period after phase adjustment in order to detect the load applied to the fan motor M, but is not limited to this. The motor control device 1 may be configured to use the amplitude of the U-phase current Iu when a predetermined time has elapsed during the mode transition period after phase adjustment and the amplitude of the U-phase current Iu has converged to a predetermined value in order to detect the load applied to the fan motor M. Here, the motor control device 1 may determine that the amplitude of the U-phase current Iu has converged to a predetermined value when the amount of change in the amplitude of the U-phase current Iu falls below a predetermined value, for example.

Furthermore, the motor control device 1 according to the above embodiment may use a composite value √(ida2 + iqa2) of the d-axis current average value ida and the q-axis current average value iqa, instead of the amplitude of the U-phase current Iu, to detect the load applied to the fan motor M. By using ^{the dq} -axis current, it is possible to handle the current as a current value taking into account the currents of all three phases (U-phase, V-phase, and W-phase).

The ranking generating unit 81 may also store a plurality of weighted start-up voltages V0 to Vx in combination with loads L _-y to L _+y . In this case, for example, the ranking generating unit 81 stores a plurality of weighted start-up voltages V0 to Vx in combination with loads L _-y to L _+y via indexes Id0 to Idx. If the voltage value of the start-up voltage ranked m+1 is smaller than that of the start-up voltage ranked m (m is a natural number) and the difference in frequency (i.e., success frequency) between the start-up voltage ranked m and the start-up voltage ranked m+1 is equal to or less than a predetermined value (for example, the difference in frequency is 30%), the start-up voltage selecting unit 82 may select the start-up voltage ranked m+1. This allows the start-up voltage selecting unit 82 to preferentially select a relatively low start-up voltage when the condition is satisfied, thereby enabling the motor control device 1 to improve energy saving.

Furthermore, the motor control device 1 according to the above embodiment stores the loads L _-y to L _+y at successful startup in combination with the success frequencies SF _{_0} to SF _{_x} , but this is not limited to the above. The motor control device 1 may store the pre-start load of the fan motor M in combination with the success frequencies SF _{_0} to SF _{_x} . This eliminates the need for the motor control device 1 to perform a process of acquiring the loads L _-y to L _+y at successful startup from the pre-start load of the fan motor M, thereby reducing the processing load on the startup voltage selection unit 82.

The motor control device 1 according to the above embodiment is configured to use the startup voltage selected by the startup voltage selection unit 82 as the acceleration voltage in the forward rotation synchronous operation section T2 or the reverse rotation synchronous operation section T12, but is not limited to this. The motor control device 1 may also be configured to use the startup voltage selected by the startup voltage selection unit 82 as the acceleration voltage in the forward rotation synchronous operation section T16 after the reverse rotation synchronous operation.

Although the embodiments of the present invention have been described above, the above embodiments are merely examples of devices and methods for embodying the technical ideas of the present invention, and the technical ideas of the present invention do not specify the materials, shapes, structures, arrangements, etc. of the components. The technical ideas of the present invention can be modified in various ways within the technical scope defined by the claims.

REFERENCE SIGNS LIST 1 Motor control device 3 Synchronous voltage setting unit 10 Drive unit 20 Detection unit 30 Calculation unit 40 Voltage output unit 50 Integration unit 60 First conversion unit 70 Loss of synchronism determination unit 80 Control unit 81 Ranking generation unit 82 Starting voltage selection unit 90 Load detection unit 91 Rotation detection unit 92 Starting load detection unit

Claims (7)

a load detection unit that detects a load applied to the sensorless synchronous motor;
a synchronous voltage setting unit that sets a second voltage command, which is a voltage command for driving the synchronous motor, based on an input first voltage command;
a drive unit that drives the synchronous motor in response to the second voltage command input from the synchronous voltage setting unit;
a ranking generating unit that stores combinations of start-up voltages for starting the synchronous motor and the load, and generates a ranking of the start-up voltages based on a frequency of successful start-up of the synchronous motor;
a start-up voltage selection unit that selects the start-up voltage to be used during a start-up process of the synchronous motor based on the load detected by the load detection unit and the ranking generated by the ranking generation unit, and outputs a voltage command for the selected start-up voltage to the synchronous voltage setting unit as the first voltage command. The motor control device according to claim 1 , wherein the load detection unit detects the load based on a current flowing through the synchronous motor when the synchronous motor is successfully started. 3. The motor control device according to claim 1, wherein the start-up voltage selection unit selects the start-up voltage that is ranked higher. 4. The motor control device according to claim 1, wherein the start-up voltage selection unit changes and selects the start-up voltage based on the ranking when start-up of the synchronous motor fails, and attempts to restart the synchronous motor. The ranking generation unit stores a plurality of weighted startup voltages in combination with the loads,
5. The motor control device according to claim 1, 2 or 4, characterized in that when the startup voltage ranked m+1st is smaller in voltage value than the startup voltage ranked mth (m is a natural number), and the difference in frequency between the startup voltage ranked mth and the startup voltage ranked m+1st is less than a predetermined value, the startup voltage selection unit selects the startup voltage ranked m+1st. 6. The motor control device according to claim 1, wherein the startup voltage selected by the startup voltage selection unit is used as an acceleration voltage for accelerating the synchronous motor during the startup process. The motor control device according to claim 1 , wherein the ranking generation unit generates the ranking for each of a plurality of predetermined loads.

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