Motor drive device, blower, and control method for motor drive device

Abstract

To drive a motor again without generating abnormal operation even in a case where supplies of a power source which operates a control section and a power source for motor drive are simultaneously cut off.SOLUTION: A motor drive device 10 comprises: an inverter 11 by which power supplied from an external power source 50 is converted into drive power for driving a motor 20 and outputted; a rotation speed calculation section 12d which calculates a rotation speed of the motor 20; a rotation speed change amount calculation section 12e by which, in a case where an operation command of the motor 20 is received, the rotation speed of the motor 20 calculated by the rotation speed calculation section 12d is acquired at least twice or more and a rotation speed change amount that is a change amount of the rotation speed per fixed time is calculated from a plurality of rotation speeds; and a motor drive possibility determination section 12a by which, in a case where the rotation speed change amount is larger than a drivable change amount threshold A1, it is determined that the motor 20 is not driven and in a case where the rotation speed change amount is equal to or smaller than the drivable change amount threshold A1, it is determined that the motor 20 is driven.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive device that drives a motor and a blower that uses the motor drive device. [Background technology]

[0002] In recent years, permanent magnet synchronous motors, which do not have brushes and have permanent magnets mounted on the rotor, have been increasingly adopted as motors due to their high efficiency and quietness. Controlling a permanent magnet synchronous motor requires detecting the magnetic pole position of the rotor. To detect the magnetic pole position of the rotor, magnetic sensors such as Hall ICs and optical sensors such as encoders are used. Additionally, to reduce costs, there are sensorless permanent magnet synchronous motors that estimate the magnetic pole position from electrical information. To estimate the magnetic pole position, it is necessary to accurately measure the current flowing through the motor's stator windings.

[0003] When a motor is used to drive a blower, the rotor has inertia due to the weight of the impeller attached to the rotor, and continues to rotate for a certain period of time even after the supply of driving current from the inverter is stopped. When restarting the motor from this inertial rotation state, there is a risk of abnormalities such as inverter overvoltage or overcurrent or motor step-out. For example, Patent Document 1 proposes a method of reducing the rotation speed to a predetermined speed by inverter control when the motor operation is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-017289 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method disclosed in Patent Document 1, the control unit that controls the drive of the motor needs to reduce the rotation speed of the motor to a predetermined rotation speed using inverter control before stopping the motor, so it cannot be applied during a power outage when the power supply that operates the control unit and the power supply that drives the motor are both cut off at the same time.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a motor drive device that can restart the motor without causing abnormal operation due to step-out or overcurrent, even if the power supply for operating the control unit and the power supply for driving the motor are simultaneously cut off. [Means for solving the problem]

[0007] The motor drive device according to the present disclosure comprises an inverter that converts power supplied from an external power source into drive power for driving the motor and outputs the converted power; a rotation speed calculation unit that calculates the rotation speed of the motor; a rotation speed change calculation unit that, when receiving a motor operation command, obtains the motor rotation speed calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount, which is the amount of change in rotation speed per certain time, from the multiple rotation speeds; a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and a control unit that controls the inverter to drive the motor if the motor drivability determination unit determines to drive the motor.

[0008] In addition, a blower using a motor drive device according to the present disclosure comprises a motor, an inverter that converts power supplied from an external power source into drive power for driving the motor and outputs the power, a rotation speed calculation unit that calculates the rotation speed of the motor, a rotation speed change calculation unit that, when receiving a motor operation command, obtains the motor rotation speed calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount, which is the amount of change in rotation speed per certain time, from the multiple rotation speeds, a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold, and a control unit that controls the inverter to drive the motor if the motor drivability determination unit determines to drive the motor, and an impeller that is attached to the motor, rotates when driven by the motor, and generates an airflow.

[0009] In addition, the control method for a motor drive device according to the present disclosure is a control method for a motor drive device that includes an inverter that converts power supplied from an external power source into drive power for driving the motor and outputs the drive power, and a control unit that controls the inverter based on the motor's rotation speed, and includes the following steps: a rotation speed calculation step in which the control unit calculates the motor's rotation speed; a rotation speed change calculation step in which, when the control unit receives a motor operation command, the control unit obtains the motor's rotation speed calculated in the rotation speed calculation step at least twice and calculates a rotation speed change amount, which is the amount of change in rotation speed per certain time, from the multiple rotation speeds; a motor drivability determination step in which the control unit determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold, and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and an inverter control step in which the control unit controls the inverter to drive the motor if it is determined in the motor drivability determination step that the motor should be driven. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to obtain a motor drive device that can restart the motor without causing abnormal operation due to step-out or overcurrent even if the power supply for operating the control unit and the power supply for driving the motor are cut off at the same time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a configuration diagram of a blower using a motor drive device according to a first embodiment. [Figure 2] 1 is a functional block diagram of a motor drive device according to a first embodiment. [Figure 3] 4 is a graph showing the time change in inertial rotation of the motor according to the first embodiment and whether or not it is possible to drive the motor. [Figure 4] 5 is a flowchart showing a motor drive possibility determination process of the motor drive device according to the first embodiment. [Figure 5] 4 is a flowchart showing a motor start process of the motor drive device according to the first embodiment. [Figure 6] 10 is a graph showing the time change in inertial rotation of the motor according to the second embodiment and whether or not it is possible to drive the motor. [Figure 7] 10 is a flowchart showing a motor drive possibility determination process of the motor drive device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 The following description will discuss embodiments of the present disclosure with reference to the accompanying drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant descriptions are appropriately simplified or omitted. The present disclosure is not limited to the following embodiments, and any of the components of the embodiments may be modified, combined, or omitted without departing from the spirit of the present disclosure.

[0013] Embodiment 1 1 is a configuration diagram of a blower 100 using a motor drive device according to a first embodiment of the present disclosure. The blower 100 is a device that drives an impeller 30 using a motor 20. The blower 100 includes the motor 20, the impeller 30 connected to the motor 20, a motor drive device 10 that controls the motor 20, an external power supply 50 that supplies power to the motor drive device 10, and a blower control unit 40 that sends a control signal to the motor drive device 10.

[0014] The motor 20 is a three-phase permanent magnet synchronous motor and includes a stator 21 and a rotor 22. The stator 21 includes U-phase, V-phase, and W-phase coils 21u, 21v, and 21w, one end of which is connected to one another in a star connection. The other end of each of the coils 21u, 21v, and 21w is connected to an inverter 11 of a motor drive device 10, which will be described later. The motor drive device 10 applies a motor drive voltage to each of the coils 21u, 21v, and 21w, and current flows through each of the coils 21u, 21v, and 21w in accordance with the voltage applied to each phase. The rotor 22 includes a permanent magnet. The current flowing through each of the coils 21u, 21v, and 21w generates a rotating magnetic field, causing the rotor 22 to rotate. As the rotor 22 rotates, the three-phase coils 21u, 21v, and 21w generate an induced voltage that corresponds to the rotational speed and the position of the rotor 22. The motor 20 is not limited to a three-phase motor, but may be a two-phase motor or a four-phase motor or more.

[0015] The impeller 30 is fixed to the rotor 22 of the motor 20. The impeller 30 rotates when driven by the motor 20, and an airflow is generated and blown.

[0016] The external power supply 50 is an AC power supply that supplies AC power to the motor drive device 10.

[0017] The blower control unit 40 transmits control signals to the motor drive device 10 to instruct the on / off and rotation speed of the motor 20. The blower control unit 40 is also connected to a system control unit (not shown) that controls all the components of the device including the blower 100. The device including the blower 100 is, for example, a ventilation system, an air conditioner, a vacuum cleaner, etc.

[0018] 2 is a functional block diagram of motor drive device 10 according to embodiment 1. Motor drive device 10 includes inverter 11, control unit 12, current detection unit 13, and power supply circuit 14. The components of motor drive device 10 are mounted on, for example, a single printed circuit board.

[0019] The power supply circuit 14 rectifies the AC current supplied from the external power supply 50, converts it into a DC current, and outputs it to the inverter 11 and the motor drive device 10.

[0020] The inverter 11 generates an AC voltage for driving the motor 20 from a DC voltage input from the power supply circuit 14. The output voltage of the inverter 11 is input to the motor 20. The inverter 11 also switches a plurality of power semiconductors to output a voltage to the motor 20 such that the effective value of the line voltage becomes the effective value of a target AC voltage. For example, a MOSFET (metal oxide semiconductor field effect transistor) or an IGBT (insulated gate bipolar transistor) is used as each power semiconductor. The inverter 11 may use a 120-degree conduction method or a 180-degree conduction method. The voltage output from the inverter 11 may be a two-phase voltage or a three-phase voltage depending on the type of motor connected.

[0021] The current detection unit 13 detects motor currents Iu, Iv, and Iw flowing from the inverter 11 to the coils 21u, 21v, and 21w of the motor 20. A current transformer can be used as the current detection unit 13. Alternatively, the current detection unit 13 may be configured to measure a voltage generated by a current flowing through a low-resistance shunt resistor. When the motor 20 is rotating by inertia, the current detection unit 13 detects the current flowing through each of the coils 21u, 21v, and 21w due to an induced voltage generated in each of the coils 21u, 21v, and 21w. The motor currents Iu, Iv, and Iw detected by the current detection unit 13 are input to the control unit 12.

[0022] The induced voltage detection unit 15 detects the induced voltage generated in each of the coils 21u, 21v, and 21w due to the rotation of the motor 20. The output waveform of the induced voltage detected by the induced voltage detection unit 15 is input to the control unit 12.

[0023] The control unit 12 includes a motor drive feasibility determination unit 12a, an inverter control unit 12b, a motor drive processing unit 12c, a rotation speed calculation unit 12d, a rotation speed change amount calculation unit 12e, and a position estimation unit 12f. The control unit 12 includes at least one processor and at least one memory. The components of the control unit 12 are software, firmware, or a combination of software and firmware. The processor is also referred to as a CPU (Central Processing Unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory is configured by, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM.

[0024] The rotation speed calculation unit 12d calculates the rotation speed of the motor 20 from the output waveform of the induced voltage input from the induced voltage detection unit 15. Because an induced voltage is generated in each of the coils 21u, 21v, and 21w even when the motor 20 is rotating by inertia, the rotation speed calculation unit 12d can calculate the rotation speed of the motor 20 even when the motor 20 is rotating by inertia. Note that the rotation speed calculation unit 12d may calculate the rotation speed of the motor 20 using the motor currents Iu, Iv, and Iw input from the current detection unit 13.

[0025] The rotation speed change amount calculation unit 12e obtains the rotation speed calculated by the rotation speed calculation unit 12d at least twice, and calculates the amount of change in the rotation speed per unit time.

[0026] When the motor drivability determination unit 12a receives an operation command for the motor 20 from the blower control unit 40, it determines whether or not the motor 20 can be driven using the amount of change in the rotation speed calculated by the rotation speed change amount calculation unit 12e. The motor drivability determination unit 12a determines not to drive the motor if the amount of change in the rotation speed is greater than the drivable change amount threshold A1, and determines to drive the motor if the amount of change in the rotation speed is equal to or less than the drivable change amount threshold A1. The drivable change amount threshold A1 is set to an upper limit of the amount of change in the rotation speed at which the motor 20 can be driven, or to a value smaller than the upper limit by providing a buffer based on the upper limit. The drivable change amount threshold A1 is set in advance in the control unit 12. The upper limit of the amount of change in the rotation speed at which the motor can be driven is determined by experiment.

[0027] The motor drive processing unit 12c performs motor drive processing to determine control of the motor 20 in accordance with the rotation speed of the motor 20 when the motor drive possibility determining unit 12a determines that the motor should be driven.

[0028] When the rotation speed of the motor 20 is equal to or greater than the sensorless control threshold R2, the position of the rotor 22 can be estimated by the position estimator 12f (described later), and the motor drive processor 12c determines to drive the motor using sensorless control. Sensorless control is a control in which a current is passed through the motor 20 according to the position of the rotor 22 estimated by the position estimator 12f, and the motor 20 rotates at a rotation speed instructed by the blower controller 40. The sensorless control threshold R2 is set to the lower limit of the rotation speed of the motor 20 when the induced voltage generated by the rotation of the motor 20 exceeds a value necessary to estimate the position of the rotor 22, and is set to the lower limit or a value greater than the lower limit by providing a buffer based on the lower limit. The sensorless control threshold R2 is set in advance in the controller 12.

[0029] If the rotation speed of the motor 20 is smaller than the sensorless control threshold R2 but equal to or greater than the positioning control threshold R1 (described later), the motor drive processing unit 12c determines to drive the motor 20 using synchronous acceleration control. Synchronous acceleration control is a control that drives the motor 20 without detecting the position of the rotor 22 by passing current through the coils 21u, 21v, and 21w to generate a rotating magnetic field that rotates at a low speed and synchronizes the rotor 22. In synchronous acceleration control, the rotation speed of the motor 20 is gradually accelerated, and when the rotation speed of the motor 20 becomes equal to or greater than the sensorless control threshold R2, the control switches to sensorless control.

[0030] If the rotation speed of the motor 20 is lower than the positioning control threshold R1, the motor drive processing unit 12c determines to perform positioning control. Positioning control is a control that passes current through each of the coils 21u, 21v, and 21w to generate a magnetic field so that the rotor 22 stops at a predetermined position. The positioning control threshold R1 is the upper limit of the rotation speed at which positioning control is possible, and is set to the upper limit or a value smaller than the upper limit by providing a buffer based on the upper limit. The positioning control threshold R1 is set in advance in the control unit 12. After the rotor 22 stops during positioning control, synchronous acceleration control is performed to drive the motor 20.

[0031] The position estimation unit 12f estimates the position of the rotor 22 from the motor currents Iu, Iv, and Iw flowing through the coils 21u, 21v, and 21w of the motor 20, which are input from the current detection unit 13. Even when no current is applied to the motor 20 and the motor 20 is rotating by inertia, the induced voltage causes a current to flow through the coils 21u, 21v, and 21w, so the position of the rotor 22 can be estimated. However, when the rotation speed of the motor 20 is low and the induced voltage is weak, the position estimation unit 12f cannot estimate the position of the rotor 22.

[0032] The inverter control unit 12b switches on and off switching elements (not shown) provided in the inverter 11 in accordance with the control of the motor 20 determined by the motor drive processing unit 12c, and controls the current flowing through each of the coils 21u, 21v, and 21w.

[0033] Fig. 3 is a graph showing the time change in the inertial rotation of motor 20 according to embodiment 1 and whether or not it is possible to drive it. Using Fig. 3, a description will be given of a motor driveability determination and motor drive process based on the rotation speed of motor 20 and the amount of change in rotation speed. In Fig. 3, T0 is the time when control unit 12 receives a command to stop motor 20 from blower control unit 40 and stops applying current from inverter 11 to motor 20, or when a power outage occurs, cutting off the supply of power from external power source 50 to power supply circuit 14 and preventing current from being applied to motor 20; hereinafter, this will be referred to as the motor stop time.

[0034] In Figure 3(a), the change in the rotation speed of motor 20 is greater than drivable change amount threshold A1 until time T1. If an operation command for motor 20 is received before time T1, motor drivability determination unit 12a determines not to drive the motor. After time T1, the change in the rotation speed becomes equal to or less than drivable change amount threshold A1, and motor drivability determination unit 12a determines to drive the motor. After time T1, the rotation speed of motor 20 is smaller than positioning control threshold R1, so motor drive processing unit 12c determines to perform positioning control.

[0035] In Figure 3(b), the change in the rotation speed of motor 20 is greater than drivable change amount threshold A1 until time T2. If an operation command for motor 20 is received before time T2, motor drivability determination unit 12a determines not to drive motor 20. After time T2, the change in rotation speed becomes equal to or less than drivable change amount threshold A1, and motor drivability determination unit 12a determines to drive motor 20. After time T2, the rotation speed of motor 20 is smaller than sensorless controllable threshold R2 and equal to or greater than positioning control threshold R1, so motor drive processing unit 12c determines to drive motor 20 using synchronous acceleration control.

[0036] 3(b), from time T0 when the motor is stopped until time T2 when the amount of change in the rotational speed of motor 20 falls below drivable change threshold A1, the rotational speed of motor 20, which was equal to or greater than sensorless controllable threshold R2, falls below sensorless controllable threshold R2. When the amount of change in the rotational speed is large, i.e., when motor 20 is rotating by inertia and the rotational speed is changing rapidly, performing drive processing for motor 20 will not be able to match the rotational speed of motor 20, and there is a high possibility that abnormal operation such as an overcurrent to inverter 11 or loss of synchronization of motor 20 will occur. Therefore, motor drivability determination unit 12a determines to drive motor 20 when the amount of change in the rotational speed of motor 20 falls below drivable change threshold A1, thereby preventing abnormal operation such as an overcurrent to inverter 11 or loss of synchronization of motor 20.

[0037] In (c) of Figure 3, the change in the rotation speed of motor 20 is greater than drivable change amount threshold A1 until time T3. If an operation command for motor 20 is received before time T3, motor drivability determination unit 12a determines not to drive motor 20. After time T3, the change in rotation speed becomes equal to or less than drivable change amount threshold A1, and motor drivability determination unit 12a determines to drive motor 20. At time T3, the rotation speed of motor 20 is equal to or greater than sensorless controllability threshold R2, so motor drive processing unit 12c determines to drive motor 20 using sensorless control.

[0038] 3(c), the rotation speed of motor 20 is equal to or greater than sensorless controllability threshold R2, but the rotation speed of motor 20 changes abruptly, making it impossible for position estimation unit 12f to accurately estimate the position of rotor 22. If control unit 12 drives motor 20 by sensorless control before time T3, motor 20 may lose synchronism. Therefore, motor drivability determination unit 12a determines to drive motor 20 when the amount of change in the rotation speed of motor 20 is equal to or less than drivable change amount threshold A1, thereby preventing motor 20 from losing synchronism.

[0039] 3(b) and 3(c) show that the rotation speed of motor 20 does not decrease even after a sufficient amount of time has passed since motor stop time T0. When impeller 30 is attached to rotor 22 of motor 20, impeller 30 may continue to rotate at a constant speed due to the influence of wind or the pressure difference between the indoor and outdoor spaces. Thus, even if the rotation speed of motor 20 does not decrease over time, control unit 12 can drive motor 20 without causing abnormal operation by determining whether motor 20 can be driven based on the amount of change in the rotation speed of motor 20 and performing drive processing according to the rotation speed of motor 20.

[0040] Next, a description will be given of the flow of the motor drive feasibility determination process in control unit 12. Fig. 4 is a flowchart showing the motor drive feasibility determination process of motor drive device 10 according to the present disclosure. The motor drive feasibility determination process starts when control unit 12 receives an operation command for motor 20 from blower control unit 40.

[0041] First, in step S101, the motor drivability determining unit 12a sets a variable n, which indicates the number of times the number of rotations of the motor 20 has been calculated, to 0. Next, the process proceeds to S102.

[0042] Next, in step S102, the motor drivability determining unit 12a increments the variable n indicating the number of calculations of the rotation number of the motor 20. Next, the process proceeds to S103.

[0043] Next, step S103 is a rotation speed calculation step. In step S103, rotation speed calculation unit 12d calculates rotation speed Rn of motor 20 from the output waveform of the induced voltage input from induced voltage detection unit 15. The calculated rotation speed Rn is input to motor drivability determination unit 12a. Next, the process proceeds to S104.

[0044] Next, in step S104, it is determined whether n is greater than a preset constant N. That is, in step S103, it is determined whether the number of times that the rotation speed calculation unit 12d has calculated the rotation speed is greater than N. The constant N is set to the number of times that the rotation speed required to calculate the amount of change in the motor rotation speed can be obtained. For example, N is 2. If n is greater than N (S104: Yes), the process proceeds to S105. On the other hand, if n is equal to or less than N (S104: No), the process returns to S102, and the calculation of the rotation speed by the rotation speed calculation unit 12d is repeated. If n is equal to or less than N, the process may return to S102 after a certain time has elapsed in order to calculate the rotation speed at regular intervals.

[0045] Next, step S105 is a rotation speed change amount calculation step. In step S105, rotation speed change amount calculation unit 12e calculates rotation speed change amount A using N rotation speeds R1 to Rn calculated by rotation speed calculation unit 12d. The rotation speed change amount A is calculated using, for example, Equation 1. Note that the method for calculating rotation speed change amount A is not limited to Equation 1 as long as it is a value indicating the amount of change in rotation speed per unit time. Next, the process proceeds to step S106.

[0046]

number

[0047] Step S106 is a motor drivability determination step. In step S106, the motor drivability determination unit 12a determines whether the change amount A in the number of rotations is smaller than the drivable change amount threshold A1. If the change amount A in the number of rotations is smaller than the drivable change amount threshold A1 (S106: Yes), it is determined that the motor 20 should be driven, and the process proceeds to step S107. If the change amount A in the number of rotations is equal to or smaller than the drivable change amount threshold A1 (S106: No), it is determined that the number of rotations is changing too rapidly and therefore the motor cannot be driven, and the process returns to S102.

[0048] Next, in step S107, the motor drive processing unit 12c starts the drive process of the motor 20. This completes the motor drive possibility determination process.

[0049] 5 is a flowchart showing the motor drive process of the motor drive device 10 according to the present disclosure. The drive process of the motor 20 will be described using Fig. 5. The flow in Fig. 5 corresponds to step S107 in Fig. 4.

[0050] First, in step S201, the motor drive processing unit 12c determines whether the rotation speed Rn calculated by the rotation speed calculation unit 12d is smaller than the positioning control threshold R1. If the rotation speed Rn is smaller than the positioning control threshold R1 (S201: Yes), it is determined that the rotation speed is small and positioning control is possible, and the process proceeds to step S202. If the rotation speed Rn is equal to or greater than the positioning control threshold R1 (S201: No), the process proceeds to step S203.

[0051] In step S202, the inverter control unit 12b applies current to each of the coils 21u, 21v, and 21w so that the rotor 22 stops at a predetermined position. The rotor 22, which has been rotating at a speed slower than the positioning control threshold R1 due to the magnetic field generated by the currents in the coils 21u, 21v, and 21w, is fixed in position. Next, the process proceeds to S204.

[0052] On the other hand, in step S203, the motor drive processing unit 12c determines whether the rotation speed Rn calculated by the rotation speed calculation unit 12d is smaller than the sensorless control threshold R2. If the rotation speed Rn is smaller than the sensorless control threshold R2 (S203: Yes), it is determined that the rotation speed is too small to estimate the position of the rotor 22 required for sensorless control, and the process proceeds to step S204. If the rotation speed Rn is equal to or greater than the sensorless control threshold R2 (S203: No), the process proceeds to step S206.

[0053] In step S204, the inverter control unit 12b performs synchronous acceleration control to drive the motor 20. Next, the process proceeds to S205.

[0054] In step S205, while the synchronous acceleration control is being performed, the motor drive processing unit 12c determines whether the rotation speed of the motor 20 calculated by the rotation speed calculation unit 12d is equal to or greater than the sensorless control threshold R2. If the rotation speed of the motor 20 is less than the sensorless control threshold R2 (S205: Yes), the process returns to S204, and the inverter control unit 12b continues to perform the synchronous acceleration control. The synchronous acceleration control gradually accelerates the rotation speed of the motor 20, and when the rotation speed of the motor 20 becomes equal to or greater than the sensorless control threshold R2, i.e., becomes a rotation speed at which the position of the rotor 22 can be estimated (S205: No), the process proceeds to S206.

[0055] In step S206, the inverter control unit 12b drives the motor 20 by sensorless control. In sensorless control, current is passed through each of the coils 21u, 21v, and 21w in accordance with the position of the rotor 22 estimated by the position estimation unit 12f, causing the rotor 22 to rotate. Note that steps S202, S204, and S206 are inverter control steps. This completes the motor drive process.

[0056] The motor drive feasibility determination process determines whether the motor 20 can be driven based on the amount of change in the rotation speed of the motor 20 while it is rotating by inertia. If it is determined that the motor can be driven, the motor drive process is performed according to the rotation speed of the motor 20. Through these processes, the motor drive device 10 can drive the motor 20 without causing abnormal operation such as step-out or overcurrent. These processes are also performed when the motor drive device 10 receives an operation command for the motor 20 from the blower control unit 40. Therefore, even if the supply of power from the external power source 50 is unexpectedly stopped due to a power outage or the like, causing the motor 20 and the motor drive device 10 to stop, and the motor drive device 10 restarts the motor 20, the motor can be driven without causing abnormal operation. In the case of a momentary power outage, power is restored within a few seconds after the motor 20 and the motor drive device 10 stop due to a power outage, so the motor drive device 10 restarts the motor 20 while the motor is rotating by inertia. Therefore, when power is restored after a momentary power outage, motor drive device 10 drives motor 20 through the motor drive feasibility determination process and the motor drive process, thereby enabling the motor to be driven without causing abnormal operation.

[0057] The motor 20 controlled by the motor drive device 10 is preferably a permanent magnet synchronous motor using a permanent magnet in the rotor 22. Permanent magnet synchronous motors continue coasting for a longer period of time after power supply is interrupted than brushed motors, and are therefore more likely to be restarted while coasting. Therefore, using the motor drive device 10 of the present disclosure to drive a permanent magnet synchronous motor effectively prevents abnormal operation. Even if the motor 20 is a brushed motor, using the motor drive device 10 of the present disclosure effectively prevents abnormal operation. Since there is no need to detect the position of the rotor 22, a brushed motor does not lose synchronization. However, when a brushed motor is driven during coasting, an overcurrent may occur. Therefore, by using the motor drive device 10 of the present disclosure to determine whether or not to drive the motor based on the change in rotation speed, the brushed motor can be driven without abnormal operation.

[0058] Furthermore, the motor 20 controlled by the motor drive device 10 is preferably a sensorless permanent magnet synchronous motor that does not have a sensor for detecting the position of the rotor 22. In a sensorless permanent magnet synchronous motor, the inability to detect the position of the rotor 22 makes it prone to abnormalities such as step-out and overcurrent. Therefore, the motor 20 of the present disclosure, when it is a sensorless permanent magnet synchronous motor, is more effective at driving without abnormal operation than a permanent magnet synchronous motor with a sensor. On the other hand, even in a permanent magnet synchronous motor with a sensor for detecting the position of the rotor 22, an error in the sensor's position detection can occur if the rotation speed during inertial rotation changes rapidly, causing the motor 20 to operate abnormally during driving. Therefore, even in a permanent magnet synchronous motor with a sensor, the motor drive device 10 can prevent abnormal operation by driving the motor 20 only after determining that the motor can be driven using a motor drivability determination process. When the motor 20 is a permanent magnet synchronous motor with a sensor for detecting the position of the rotor 22, the position estimation unit 12f estimates the position of the rotor 22 using the sensor for detecting the position of the rotor 22.

[0059] As described above, the motor drive device 10 according to this embodiment comprises an inverter 11 that converts power supplied from an external power source 50 into drive power for driving the motor 20 and outputs the converted power; a rotation speed calculation unit 12d that calculates the rotation speed of the motor 20; a rotation speed change calculation unit 12e that, when receiving an operation command for the motor 20, obtains the rotation speed of the motor 20 calculated by the rotation speed calculation unit 12d at least twice and calculates a rotation speed change amount, which is the amount of change in the rotation speed per unit time, from the multiple rotation speeds; a motor drivability determination unit 12a that determines not to drive the motor 20 if the rotation speed change amount is greater than the drivability change amount threshold A1, and determines to drive the motor 20 if the rotation speed change amount is equal to or less than the drivability change amount threshold A1; and an inverter control unit 12b that, when the motor drivability determination unit 12a determines to drive the motor 20, controls the inverter 11 to drive the motor 20.

[0060] With this configuration, even when the motor 20 and the motor drive device 10 stop unexpectedly due to a power outage or the like and then the motor drive device 10 restarts the motor 20, the motor drive device 10 can drive the motor 20 without causing abnormal operation such as step-out or overcurrent.

[0061] Furthermore, a permanent magnet synchronous motor, which uses a permanent magnet in the rotor 22, is suitable for the motor 20 controlled by the motor drive device 10. Compared to a brush motor, a permanent magnet synchronous motor continues to rotate by inertia for a longer period of time after the power supply is cut off, and therefore there are many opportunities for it to be restarted while rotating by inertia. Therefore, by using the motor drive device 10 of the present disclosure to drive a permanent magnet synchronous motor, the effect of being able to drive it without causing abnormal operation is significant.

[0062] Furthermore, it is desirable that the motor 20 driven by the motor drive device 10 be a sensorless permanent magnet synchronous motor that does not have a sensor for detecting the position of the rotor 22. In a sensorless permanent magnet synchronous motor, the inability to detect the position of the rotor 22 makes it prone to abnormalities such as step-out and overcurrent. Therefore, by using the motor drive device 10 of the present disclosure to drive a sensorless permanent magnet synchronous motor, the effect of being able to drive it without causing abnormal operation is significant.

[0063] Furthermore, if the rotation speed change amount is equal to or less than drivable change amount threshold A1 and the rotation speed calculated by rotation speed calculation unit 12d is equal to or greater than sensorless controllable rotation speed threshold R2, inverter control unit 12b drives motor 20 by sensorless control. With this configuration, if the rotation speed due to inertial rotation of motor 20 is equal to or greater than sensorless controllable rotation speed threshold R2, i.e., if motor 20 is rotating by inertia at a speed sufficient for estimating the position of rotor 22, motor 20 can be driven by sensorless control without synchronous acceleration control.

[0064] Furthermore, when motor drivability determination unit 12a determines that motor 20 should not be driven, rotation speed calculation unit 12d and rotation speed change calculation unit 12e repeatedly calculate the rotation speed and the rotation speed change amount until the rotation speed change amount calculated by rotation speed change amount calculation unit 12e becomes equal to or less than drivable change amount threshold A1. With this configuration, when the change in rotation speed is no longer steep and it is determined that normal driving is possible, motor drive device 10 can drive motor 20.

[0065] A blower 100 equipped with a motor drive device 10 of the present disclosure includes a motor 20, an inverter 11 that converts power supplied from an external power supply 50 into drive power for driving the motor 20 and outputs the converted power, a rotation speed calculation unit 12d that calculates the rotation speed of the motor 20, a rotation speed change amount calculation unit 12e that, when receiving an operation command for the motor 20, acquires the rotation speed of the motor 20 calculated by the rotation speed calculation unit 12d at least twice and calculates a rotation speed change amount that is a change amount in the rotation speed per certain time from the multiple rotation speeds, and a rotation speed change amount calculation unit 12e that calculates a rotation speed change amount that is a change amount in the rotation speed per certain time from the multiple rotation speeds, and a drivable change amount threshold A The motor drive device 10 includes a motor drivability determination unit 12a that determines not to drive the motor 20 when the rotation speed change amount is greater than 1 and determines to drive the motor 20 when the rotation speed change amount is equal to or less than the drivability change amount threshold A1, and a control unit 12 that includes an inverter control unit 12b that controls the inverter 11 to drive the motor 20 when the motor drivability determination unit 12a determines to drive the motor 20, and an impeller 30 that is attached to the motor 20 and rotates when driven by the motor 20 to generate an airflow. Since the impeller 30 is attached to the motor 20, the weight of the impeller 30 makes it easy for the motor 20 to rotate by inertia after the power supply to the motor 20 is cut off. Furthermore, if wind hits the impeller 30, the motor 20 may continue to rotate even without power supply. Therefore, the motor drive device 10 of the present disclosure, which drives the motor 20 without causing abnormal operation of the motor 20 during inertial rotation, is highly effective when used in a blower 100 that includes the impeller 30.

[0066] The control method for motor drive device 10 disclosed herein is a control method for motor drive device 10 that includes inverter 11 that converts power supplied from external power source 50 into drive power for driving motor 20 and outputs it, and control unit 12 that controls inverter 11 based on the rotation speed of motor 20, and includes the following steps: a rotation speed calculation step in which control unit 12 calculates the rotation speed of motor 20; a rotation speed change calculation step in which, when control unit 12 receives an operation command for motor 20, control unit 12 obtains the rotation speed of motor 20 calculated in the rotation speed calculation step at least twice and calculates a rotation speed change amount, which is the amount of change in rotation speed per certain time, from the multiple rotation speeds; a motor drivability determination step in which control unit 12 determines not to drive motor 20 if the rotation speed change amount is greater than drivable change amount threshold A1, and determines to drive motor 20 if the rotation speed change amount is equal to or less than drivable change amount threshold A1; and an inverter control step in which control unit 12 controls inverter 11 to drive motor 20 if it is determined in the motor drivability determination step that motor 20 should be driven. With this control method, even when the motor 20 and the motor drive device 10 stop unexpectedly due to a power outage or the like and then the motor drive device 10 restarts the motor 20, the motor drive device 10 can drive the motor 20 without causing abnormal operation such as step-out or overcurrent.

[0067] Embodiment 2 Next, a second embodiment will be described. In this embodiment, the configuration of the blower 100 and the functional blocks of the motor drive device 10 are the same as those in the first embodiment, and therefore a description thereof will be omitted. In the first embodiment, whether or not the motor 20 can be driven is determined based on whether or not the amount of change in the rotation speed is greater than the drivable change amount threshold A1. Even if the amount of change in the rotation speed is equal to or greater than the drivable change amount threshold A1, if the rotation speed of the motor 20 is smaller than the positioning control threshold R1, i.e., if the motor 20 is rotating at a low speed, a current is passed through each of the coils 21u, 21v, and 21w to generate a magnetic field, thereby stopping the rotor 22 at a predetermined position. Therefore, in the second embodiment, if the rotation speed of the motor 20 is smaller than the positioning control threshold R1, it is determined that the motor 20 can be driven regardless of the amount of change in the rotation speed.

[0068] FIG. 6 is a graph showing the time change in the inertial rotation of motor 20 and whether or not it is drivable according to the second embodiment. In FIG. 6, the change in the rotation speed of motor 20 is greater than drivable change threshold A1 until time T5. After time T4, the rotation speed of motor 20 becomes smaller than positioning control threshold R1. In this embodiment, even if the change in the rotation speed is greater than drivable change threshold A1, if the rotation speed of motor 20 is smaller than positioning control threshold R1, motor drivability determination unit 12a determines to drive motor 20. If the rotation speed of motor 20 is smaller than positioning control threshold R1, rotor 22 can be fixed by passing current through coils 21u, 21v, and 21w so that rotor 22 stops at a predetermined position, even if the change in the rotation speed is large. If an operation command for motor 20 is issued between time T4 and time T5, motor drivability determination unit 12a determines to drive the motor. Since the rotation speed of the motor 20 is smaller than the positioning control threshold value R1, the motor drive processing unit 12c determines to perform positioning control.

[0069] Fig. 7 is a flowchart showing the motor drive possibility determination process of motor drive device 10 according to embodiment 2. In Fig. 7, steps that perform the same processes as in Fig. 4 are given the same reference numerals, and descriptions thereof will be omitted.

[0070] 7, the rotation speed calculation unit 12d calculates the rotation speed Rn of the motor 20. Next, the process proceeds to step S301.

[0071] In step S301, the motor drivability determination unit 12a determines whether the rotation speed Rn is greater than the positioning control threshold R1. If the rotation speed Rn is greater than the positioning control threshold R1 (S301: Yes), the process proceeds to step S104. Since the subsequent processing is the same as in embodiment 1, a description thereof will be omitted. If the rotation speed Rn is equal to or less than the positioning control threshold R1 (S301: No), the process proceeds to step S107, where the motor drive processing is started. If the rotation speed Rn is equal to or less than the positioning control threshold R1, the rotation speed Rn of the motor 20 is sufficiently small, and positioning control, i.e., control so that the rotor 22 stops at a predetermined position, can be performed. Therefore, if the rotation speed Rn is equal to or less than the positioning control threshold R1, it is determined that the motor 20 can be driven regardless of the amount of change in the rotation speed. Since the processing in step S107 is the same as in embodiment 1, a description thereof will be omitted. This concludes the motor drivability determination processing according to embodiment 2.

[0072] As described above, motor drive device 10 according to the second embodiment includes inverter 11 that converts power supplied from external power supply 50 into drive power for driving motor 20 and outputs the converted power, rotation speed calculation unit 12d that calculates the rotation speed of motor 20, rotation speed change amount calculation unit 12e that, when receiving an operation command for motor 20, acquires the rotation speed of motor 20 calculated by rotation speed calculation unit 12d at least twice and calculates a rotation speed change amount that is the amount of change in rotation speed per certain time from the multiple rotation speeds, and rotation speed change amount calculation unit 12e that determines not to drive motor 20 when the rotation speed change amount is greater than drivable change amount threshold A1, and The control unit 12 includes a motor drivability determination unit 12a that determines to drive the motor 20 when the rotation speed change amount is equal to or less than the drivability change amount threshold A1, and an inverter control unit 12b that controls the inverter 11 to drive the motor 20 when the motor drivability determination unit 12a determines to drive the motor 20. When the rotation speed calculated by the rotation speed calculation unit 12d is smaller than the positioning control threshold R1, the motor drivability determination unit 12a determines to drive the motor 20 regardless of the amount of change in the rotation speed, and the inverter control unit 12b performs positioning control on the motor 20 to drive it. When the rotation speed of the motor 20 is smaller than the positioning control threshold R1, positioning control is performed and the motor 20 can be driven regardless of the amount of change in the rotation speed. Therefore, even if the rotation speed is changing rapidly, the motor can be driven if the rotation speed is smaller than the positioning control threshold R1.

[0073] Furthermore, when motor drivability determination unit 12a determines that motor 20 should not be driven, calculation of the rotation speed by rotation speed calculation unit 12d and calculation of the rotation speed change amount by rotation speed change amount calculation unit 12e are repeated until the rotation speed change amount calculated by rotation speed change amount calculation unit 12e becomes equal to or less than drivable change amount threshold A1 or the rotation speed calculated by rotation speed calculation unit 12d becomes smaller than positioning control threshold R1. With this configuration, when the change in rotation speed is no longer steep or the rotation speed becomes small enough to allow positioning control, and it is determined that normal driving is possible, motor drive device 10 can drive motor 20.

[0074] The configurations shown in the above embodiments are examples of the content of the present invention, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present invention.

[0075] Examples of aspects that may be included in the present disclosure are set forth below as appendices. (Appendix 1) an inverter that converts power supplied from an external power source into drive power for driving a motor and outputs the drive power; a control unit including: a rotation speed calculation unit that calculates the rotation speed of the motor; a rotation speed change amount calculation unit that, when receiving an operation command for the motor, obtains the rotation speed of the motor calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount, which is a change amount of the rotation speed per certain time, from the plurality of rotation speeds; a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and an inverter control unit that controls an inverter to drive the motor when the motor drivability determination unit determines to drive the motor; A motor drive device comprising: (Appendix 2) 2. The motor drive device according to claim 1, wherein the motor is a permanent magnet synchronous motor that uses a permanent magnet in a rotor. (Appendix 3) 3. The motor drive device according to claim 2, wherein the motor is a sensorless permanent magnet synchronous motor that does not have a sensor for detecting the position of the rotor. (Appendix 4) The motor drive device according to any one of appendices 1 to 3, wherein when the rotation speed calculated by the rotation speed calculation unit is smaller than a positioning control threshold, the motor drivability determination unit determines to drive the motor regardless of the amount of change in the rotation speed, and the inverter control unit performs positioning control on the motor and drives it. (Appendix 5) 4. The motor drive device according to claim 2, wherein the inverter control unit drives the motor by sensorless control when the amount of change in rotation speed is equal to or less than the drivable change amount threshold and the rotation speed calculated by the rotation speed calculation unit is equal to or greater than a sensorless controllable rotation speed threshold. (Appendix 6) 6. The motor drive device according to claim 1, wherein, when the motor drivability determination unit determines not to drive the motor, the rotation speed calculation unit repeats calculating the rotation speed and the rotation speed change amount calculation unit repeatedly calculates the rotation speed until the rotation speed change amount calculated by the rotation speed change amount calculation unit becomes equal to or less than the drivable change amount threshold. (Appendix 7) 5. The motor drive device according to claim 4, wherein, when the motor drivability determination unit determines not to drive the motor, the rotation speed calculation unit repeats calculating the rotation speed and the rotation speed change amount calculation unit until the rotation speed change amount calculated by the rotation speed change amount calculation unit becomes equal to or less than the drivable change amount threshold, or the rotation speed calculated by the rotation speed calculation unit becomes smaller than a positioning control threshold. (Appendix 8) A motor; a motor drive device comprising: an inverter that converts power supplied from an external power supply into drive power for driving a motor and outputs the power; a rotation speed calculation unit that calculates the rotation speed of the motor; a rotation speed change amount calculation unit that, when receiving an operation command for the motor, obtains the rotation speed of the motor calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount that is a change in the rotation speed per certain time from the plurality of rotation speeds; a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and an inverter control unit that controls the inverter to drive the motor when the motor drivability determination unit determines to drive the motor; an impeller attached to the motor, which rotates when driven by the motor and generates an airflow; A blower comprising: (Appendix 9) A control method for a motor drive device including an inverter that converts power supplied from an external power supply into drive power for driving a motor and outputs the drive power, and a control unit that controls the inverter based on the rotation speed of the motor, comprising: a rotation speed calculation step in which the control unit calculates the rotation speed of the motor; a rotation speed change amount calculation step in which, when the control unit receives an operation command for the motor, the control unit acquires the rotation speed of the motor calculated in the rotation speed calculation step at least twice or more times and calculates a rotation speed change amount, which is an amount of change in the rotation speed per certain time, from the multiple rotation speeds; a motor drive possibility determination step in which the control unit determines not to drive the motor when the amount of change in the number of rotations is greater than a drivable change amount threshold, and determines to drive the motor when the amount of change in the number of rotations is equal to or less than the drivable change amount threshold; an inverter control step in which, when it is determined in the motor drive possibility determination step that the motor is to be driven, the control unit controls an inverter so as to drive the motor; A control method for a motor drive device comprising: [Explanation of symbols]

[0076] 10 motor drive device, 11 inverter, 12 control unit, 12a motor drive feasibility determination unit, 12b inverter control unit, 12c motor drive processing unit, 12d rotation speed calculation unit, 12e rotation speed change amount calculation unit, 12f position estimation unit, 13 current detection unit, 14 power supply circuit, 20 motor, 21 stator, 21u coil, 21v coil, 21w coil, 22 rotor, 30 impeller, 40 blower control unit, 50 external power supply, 100 blower, R1 positioning control threshold, R2 sensorless controllability threshold, A1 drivability change amount threshold.

Claims

1. an inverter that converts power supplied from an external power source into drive power for driving a motor and outputs the drive power; a control unit including: a rotation speed calculation unit that calculates the rotation speed of the motor; a rotation speed change amount calculation unit that, when receiving an operation command for the motor, obtains the rotation speed of the motor calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount, which is a change amount of the rotation speed per certain time, from the plurality of rotation speeds; a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and an inverter control unit that controls an inverter to drive the motor when the motor drivability determination unit determines to drive the motor; A motor drive device comprising:

2. 2. The motor drive device according to claim 1, wherein the motor is a permanent magnet synchronous motor using a permanent magnet in a rotor.

3. 3. The motor drive device according to claim 2, wherein the motor is a sensorless permanent magnet synchronous motor that does not have a sensor for detecting the position of the rotor.

4. 4. The motor drive device according to claim 2, wherein when the rotation speed calculated by the rotation speed calculation unit is smaller than a positioning control threshold, the motor drivability determination unit determines to drive the motor regardless of an amount of change in the rotation speed, and the inverter control unit performs positioning control on the motor and drives it.

5. 4. The motor drive device according to claim 2, wherein the inverter control unit drives the motor by sensorless control when the amount of change in rotation speed is equal to or less than the drivable change amount threshold and the rotation speed calculated by the rotation speed calculation unit is equal to or greater than a sensorless controllable rotation speed threshold.

6. 4. The motor drive device according to claim 1, wherein, when the motor drivability determination unit determines not to drive the motor, the rotation speed calculation unit repeats calculating the rotation speed and the rotation speed change amount calculation unit repeatedly calculates the rotation speed until the rotation speed change amount calculated by the rotation speed change amount calculation unit becomes equal to or less than the drivable change amount threshold.

7. 5. The motor drive device according to claim 4, wherein, when the motor drivability determination unit determines not to drive the motor, the calculation of the rotation speed by the rotation speed calculation unit and the calculation of the rotation speed change amount by the rotation speed change amount calculation unit are repeated until the rotation speed change amount calculated by the rotation speed calculation unit becomes equal to or less than the drivable change amount threshold or the rotation speed calculated by the rotation speed calculation unit becomes smaller than a positioning control threshold.

8. A motor; a motor drive device comprising: an inverter that converts power supplied from an external power supply into drive power for driving a motor and outputs the power; a rotation speed calculation unit that calculates the rotation speed of the motor; a rotation speed change amount calculation unit that, when receiving an operation command for the motor, obtains the rotation speed of the motor calculated by the rotation speed calculation unit at least twice and calculates a rotation speed change amount that is a change amount in the rotation speed per certain time from the plurality of rotation speeds; a motor drivability determination unit that determines not to drive the motor if the rotation speed change amount is greater than a drivable change amount threshold and determines to drive the motor if the rotation speed change amount is equal to or less than the drivable change amount threshold; and an inverter control unit that controls the inverter to drive the motor when the motor drivability determination unit determines to drive the motor; an impeller attached to the motor, which rotates when driven by the motor and generates an airflow; A blower comprising:

9. A control method for a motor drive device including an inverter that converts power supplied from an external power supply into drive power for driving a motor and outputs the drive power, and a control unit that controls the inverter based on the rotation speed of the motor, comprising: a rotation speed calculation step in which the control unit calculates the rotation speed of the motor; a rotation speed change amount calculation step in which, when the control unit receives an operation command for the motor, the control unit acquires the rotation speed of the motor calculated in the rotation speed calculation step at least twice or more times and calculates a rotation speed change amount, which is an amount of change in the rotation speed per certain time, from the multiple rotation speeds; a motor drive possibility determination step in which the control unit determines not to drive the motor when the amount of change in the number of rotations is greater than a drivable change amount threshold, and determines to drive the motor when the amount of change in the number of rotations is equal to or less than the drivable change amount threshold; an inverter control step in which, when it is determined in the motor drive possibility determination step that the motor is to be driven, the control unit controls an inverter so as to drive the motor; A control method for a motor drive device comprising:

Images