JP5929286B2 - Electric motor control device - Google Patents

Description

  The present invention relates to a motor control device, and more particularly to a motor control device driven by inverter control.

  Conventionally, a compressor mounted in an air conditioner, a refrigerator, or the like has an electric motor, and an electric motor driven by inverter control such as a sensorless three-phase brushless DC motor is applied. There are many. As a control method of the brushless DC motor, there is known a method of switching control of a switching element of an inverter circuit provided in a control device for driving the brushless DC motor by a PWM (Pulse Width Modulation) method.

  When the brushless DC motor is driven by the rectangular wave drive, an induced voltage is generated in the non-energized phase of the brushless DC motor. By supplying a voltage higher than the induced voltage from the inverter circuit, the brushless DC motor is rotated. Let it continue. However, if the induced voltage generated in the non-energized phase is higher than the supply voltage from the inverter circuit, the rotational speed of the brushless DC motor cannot be increased. In such a case, by setting the phase of the current supplied to the brushless DC motor to a phase that is advanced with respect to the induced voltage, even when the induced voltage is high, more current is supplied to the brushless DC motor and the rotational speed is increased. The drive control of the brushless DC motor is performed by using the field weakening control method (for example, Patent Document 1).

  By the way, in the brushless DC motor as described above, there is a possibility that the step-out may occur due to insufficient torque (overload) of the motor. If the step-out occurs, for example, energization of the brushless DC motor is stopped. Therefore, it is necessary to perform step-out protection control for stopping the brushless DC motor.

  In a brushless DC motor that performs rectangular wave driving, a return current flows in a non-energized phase due to energization switching, and as a result, a spike voltage is generated in each phase. The spike voltage appears as a spike-like waveform (hereinafter referred to as a spike voltage waveform) in the voltage waveform of each phase of the brushless DC motor. A method for detecting the occurrence of step-out using this spike voltage waveform has been proposed. Yes.

  If step-out occurs, the time during which the return current flows (return current time) becomes longer, and the generation time of the spike voltage also becomes longer. The brushless DC motor control means performs various processes related to the brushless DC motor in parallel, and the spike voltage is detected at a predetermined timing, for example, at a timing when the switching elements constituting the inverter circuit are turned on. This is done by interrupt processing.

  Therefore, if the spike voltage generation time becomes longer due to a step-out and the spike voltage waveform rises / falls after the end of the interrupt processing period for detecting the spike voltage, the spike voltage waveform rises / falls. Can no longer be detected. If this state occurs continuously a predetermined number of times, for example, 5 times, the control means determines that a step-out has occurred in the brushless DC motor, and executes step-out protection control.

Japanese Patent Laid-Open No. 2003-199382 (pages 4 to 5, FIGS. 5 and 6)

  As described above, the control unit of the brushless DC motor performs various processes related to the brushless DC motor in parallel, including the interrupt process for detecting the rise / fall of the spike voltage waveform. If there are many processes that are executed in parallel by the control means and a large load is applied to the control means, even if it is time to execute the interrupt process that detects the rise / fall of the spike voltage waveform, the spike voltage waveform actually The operation of detecting the rising / falling may be delayed.

  When the load applied to the brushless DC motor is reduced, the spike voltage generation time may be shortened, contrary to the case where the step-out occurs in the brushless DC motor. Interrupt processing to detect spike voltage waveform rise / fall if a delay occurs in the operation of detecting the spike voltage waveform rise / fall by the control means as described above when the spike voltage generation time becomes short The rise / fall of the spike voltage waveform occurs before performing the operation, and the rise / fall of the spike voltage waveform may not be detected.

  However, in the conventional brushless DC motor, if a state where the rising / falling of the spike voltage waveform cannot be detected continuously occurs a predetermined number of times, the step-out protection control is executed regardless of the cause. Therefore, when the spike voltage waveform rise / fall cannot be detected due to a delay in the interrupt processing for detecting the rise / fall of the spike voltage waveform executed by the control means, that is, when it is unlikely that a step-out has occurred. Even so, since the step-out protection control is executed and the brushless DC motor is stopped, the brushless DC motor is stopped unnecessarily.

  The present invention solves the above-described problems, and an object of the present invention is to provide an electric motor control device that can accurately detect the occurrence of step-out in an electric motor and can fully utilize the performance of the electric motor.

In order to solve the above-described problems, a motor control device according to the present invention converts DC power into AC power by an inverter, supplies the AC power to the motor, and controls the rotation of the motor. After the energization is switched, the detection of the spike voltage generated due to the reflux current generated at the time of switching is permitted for a predetermined time, and the generation time of the spike voltage is stored . Then, when the rising or falling edge of the spike voltage cannot be detected, the motor control device reads the last spike voltage occurrence time detected and stored, and a state in which this occurrence time is equal to or longer than a predetermined time continues for a predetermined number of times. In such a case, it is determined that the motor has stepped out, and step-out protection control is performed to stop the motor.

  Since the motor control device of the present invention configured as described above can accurately detect the occurrence of step-out in the motor using the generated spike detection signal and the generation time of the stored spike voltage, erroneous detection of step-out occurrence It is possible to avoid unnecessary stopping of the electric motor.

It is a block diagram which shows the structure of the control apparatus of a brushless DC motor in the Example of this invention. It is a timing chart for demonstrating the behavior of the brushless DC motor in the Example of this invention when the field-weakening control is performed. It is a timing chart for demonstrating the behavior of a brushless DC motor when a step-out occurs when performing field weakening control. It is a timing chart for demonstrating the behavior of a brushless DC motor when the spike detection signal cannot be detected due to the processing in the control means during the field weakening control. It is a flowchart explaining the process when the position detection of a rotor cannot be performed in the Example of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, a control device that drives and controls a brushless DC motor of a compressor mounted on an outdoor unit of an air conditioner will be described as an example. The present invention is not limited to the following embodiments, and can be variously modified without departing from the gist of the present invention.

  The brushless DC motor 200 to be controlled by the control device 100 includes a hollow stator having three-phase (U-phase, V-phase, and W-phase) windings, and a four-pole coil disposed in the hollow interior of the stator. A three-phase, four-pole sensorless brushless DC motor including a rotor having a permanent magnet. As this brushless DC motor 200, an IPM (Interior Parmant Magnet) motor in which a permanent magnet is embedded in the rotor may be applied, or an SPM (Surface Permanent Magnet) motor in which a permanent magnet is disposed on the surface of the rotor. May be.

  The control device 100 includes an AC power source 1 that supplies AC power, a converter circuit 2 that converts AC power supplied from the AC power source 1 into DC power, and a smoothing capacitor 3 that smoothes the DC power converted by the converter circuit 2. And an inverter circuit 4 (which forms at least a part of the inverter means) that drives the brushless DC motor 200 using a DC power smoothed by the smoothing capacitor 3, and winding voltages (motor terminal voltages) of the brushless DC motor 200. ) Are synthesized from the respective windings through resistors, and a virtual neutral point voltage circuit 6 for outputting a motor virtual neutral point voltage obtained by dividing by a resistor connected between the synthesized point and the ground, and The motor virtual neutral point voltage output from the virtual neutral point voltage circuit 6 is compared with the reference voltage to obtain the intersection (zero cross point) of both voltages. The position detection circuit 8 that detects the position of the rotor from the intersected intersection, the control means 10 that controls the brushless DC motor 200 based on the signal from the position detection circuit 8 and the like, and the control signal that the control circuit 10 outputs are also included. And a motor drive circuit 7 for driving the brushless DC motor 200 via the inverter circuit 4.

  A shunt resistor 5 that detects a bus current of the inverter circuit 4 is connected between the smoothing capacitor 3 and the inverter circuit 4. The current detection circuit 9 detects the voltage across the shunt resistor 5. The current detection circuit 9 calculates the bus current of the inverter circuit 4 from the input voltage, and the calculated bus current is input to the CPU 11 (to be described later) via the A / D conversion unit 14 included in the control means 10.

  The inverter circuit 4 has a total of six switching elements including three switching elements 41U1, 41V1, and 41W1 on the upper arm and three switching elements 41U2, 41V2, and 41W2 on the lower arm. A phase bridge circuit is configured. These six switching elements (hereinafter referred to as switching element 41 unless otherwise mentioned) can be realized by, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Field Effect Transistor), or the like. A free-wheeling diode 42 is connected to each switching element 41 in parallel. Specifically, an anode terminal of the free-wheeling diode 42 is connected to an emitter terminal of the switching element 41, and a free-wheeling diode 42 is connected to a collector terminal of the switching element 41. The cathode terminal is connected. The free-wheeling diode 42 has a function of flowing a free-wheeling current generated by energy accumulated in the stator winding of the brushless DC motor 200 that becomes a non-conduction phase at the moment when the corresponding switching element 41 turns off the switch to the input power supply side. .

  The control unit 10 generates a PWM (Pulse Width Modulation) waveform based on a command from the CPU 11 that controls the rotational speed of the brushless DC motor 200, and outputs the generated PWM waveform to the motor drive circuit 7. A storage unit 15 including a unit 12 and a ROM (Read Only Memory) in which a control program for executing various types of processing is stored in advance, and a RAM (Random Access Memory) in which calculation parameters and data for various types of processing are stored. And an input unit 13 and an A / D conversion unit 14.

  Next, a method for controlling the brushless DC motor 200 realized using the control device 100 having the above-described configuration will be described. The position detection circuit 8 compares the induced voltage generated in the non-energized phase of the brushless DC motor 200 captured via the virtual neutral point voltage circuit 6 with the reference voltage, and detects the intersection (zero cross point) between the two. Then, the position detection circuit 8 generates a position detection signal based on the detected zero cross point and outputs it to the control means 10.

  The CPU 11 having input the rotor position detection signal via the input unit 13 calculates the motor rotation speed (actual rotation speed) of the brushless DC motor 200 using the position detection signal. Further, the CPU 11 calculates the PWM waveform from the difference between the calculated motor rotation speed and the rotation speed (frequency) target value output from the control unit of the outdoor unit and the bus current value of the inverter circuit 4 input from the current detection circuit 9. , And outputs a rotation speed instruction signal including the calculated duty ratio to the PWM generator 12. Furthermore, the CPU 11 outputs a commutation signal including information about the commutation timing and which switching element 41 of the inverter circuit 4 is switched on / off to the PWM generation unit 12 using the input position detection signal. .

  The PWM generation unit 12 that has received the rotation speed instruction signal and the commutation signal from the CPU 11 generates a PWM waveform having a duty ratio included in the rotation speed instruction signal, and the commutation timing and inverter circuit 4 included in the commutation signal. An energization switching signal is generated from information about which of the switching elements 41 is switched on / off. Then, the PWM generation unit 12 generates a drive signal in which the generated PWM waveform is superimposed on the generated energization switching signal, and outputs the drive signal to the motor drive circuit 7.

The motor drive circuit 7 that has received the drive signal from the PWM generator 12 generates a motor drive signal based on the input drive signal and outputs the motor drive signal to the inverter circuit 4. The inverter circuit 4 to which the motor drive signal is input from the motor drive circuit 7 generates a three-phase rectangular wave voltage using the DC voltage smoothed by the smoothing capacitor 3 and the input motor drive signal. It is applied to the brushless DC motor 200 at a predetermined energization timing.
In the following description, the case where the drive control of the brushless DC motor 200 is performed according to the rotor position detection result as described above is referred to as normal control.

  By controlling the brushless DC motor 200 as described above, the rotation speed of the brushless DC motor 200 is controlled to be the target rotation speed. In the PWM method, as the duty ratio of the PWM control superimposed on the drive signal increases, the electrical phase (energization phase) of the energization switching timing advances and the motor rotation speed increases. In order to further increase the motor rotation speed after the duty ratio of the PWM waveform reaches 100%, the phase of the current supplied to the brushless DC motor 200 is advanced with respect to the induced voltage so that the induced voltage is reduced. Even in a high state, it becomes possible to supply more current to the brushless DC motor 200, thereby executing field-weakening control that increases the rotational speed of the brushless DC motor 200.

  Next, a step-out detection method when performing field weakening control and field weakening control of the brushless DC motor 200 realized using the control device 100 will be specifically described with reference to FIGS. 1 to 4. When the rotational speed of the brushless DC motor 200 is further increased after the duty ratio of the PWM control reaches 100%, the CPU 11 of the control means 10 causes the phase angle of the energization phase of each phase of the brushless DC motor 200 from the normal control. Shift to field-weakening control.

  FIG. 2 is a timing chart for explaining the behavior of the control device 100 when the CPU 11 is performing field-weakening control. In FIG. 2, the drive signal indicates a signal for turning on / off each switching element 41 of the inverter circuit 4, and the drive signal (U1) is supplied to the base of the switching element 41U1, and the drive signal (V1) ) Indicates what is supplied to the base of the switching element 41V1, and the drive signal (W1) indicates what is supplied to the base of the switching element 41W1. The drive signal (U2) is supplied to the base of the switching element 41U2, the drive signal (V2) is supplied to the base of the switching element 41V2, and the drive signal (W2) is supplied to the base of the switching element 41W2. Each one is shown.

  When the CPU 11 performs field weakening control of the brushless DC motor 200, only a predetermined electrical angle (predetermined and stored in the storage unit 15) from the commutation timing when the brushless DC motor 200 is driven by normal control. The drive signals are supplied to the inverter circuit 4 so as to quickly commutate. Thereby, the field angle control is performed by advancing the phase angle of the energization phase of each phase of the brushless DC motor 200.

  In FIG. 2, the voltage waveform indicates the change in voltage of each phase (changes between 0 and the voltage Vp applied to the inverter 4) when the brushless DC motor 200 is driven by field weakening control. The UN voltage waveform is the voltage change in the U-phase coil of the brushless DC motor 200, the VN voltage waveform is the voltage change in the V-phase coil of the brushless DC motor 200, the WN voltage waveform is the voltage change in the W-phase coil of the brushless DC motor 200, Respectively.

  In the voltage waveform of each phase, a spike voltage due to the reflux current flowing in each phase when not energized appears as a spike voltage waveform as shown in FIG. The spike voltage is generated when the switching elements 41U2, 41V2, 41W2 constituting the lower arm of the inverter circuit 4 are switched from on to off, and when the switching elements 41U1, 41V1, 41W1 constituting the upper arm are switched from on to off. Each case occurs.

  Specifically, in the UN voltage waveform, the spike voltage waveform (U2) when the drive signal (U2) switches from on to off, and the spike voltage waveform when the drive signal (U1) switches from on to off. (U1) appears. Further, in the VN voltage waveform, the spike voltage waveform (V2) when the drive signal (V2) is switched from on to off, and the spike voltage waveform (V1) when the drive signal (V1) is switched from on to off. Each appears. In the WN voltage waveform, the spike voltage waveform (W2) is switched when the drive signal (W2) is switched from on to off, and the spike voltage waveform (W1) is switched when the drive signal (W1) is switched from on to off. Each appears.

  In the following description, the width of the spike voltage waveform generated in the voltage waveform of each phase, that is, the spike voltage generation time is represented by a spike angle converted to an electrical angle. In FIG. 2, the spike angle corresponding to the spike voltage waveform (U1) and the spike voltage waveform (U2) is Ru, the spike angle corresponding to the spike voltage waveform (V1) and the spike voltage waveform (V2) is Rv, and the spike voltage waveform ( The spike angle corresponding to W1) and the spike voltage waveform (W2) is Rw. The CPU 11 overwrites and stores the spike angle generated in each phase in the storage unit 15.

  The spike detection signal is generated by the CPU 11 using each spike voltage waveform described above. Specifically, the CPU 11 determines that the spike voltage waveforms (U2), (V2), and (W2) that are generated when the switching elements 41U2, 41V2, and 41W2 are switched from on to off respectively change from Vp → 0 (hereinafter referred to as the following). , And the spike voltage waveforms (U1), (V1), and (W1) generated when the switching elements 41U1, 41V1, and 41W1 are switched from on to off, respectively, from 0 to Vp ( Thereafter, the rise and description) are detected, and a spike detection signal as shown in FIG. 2 is generated using these.

  The detection permission indicates a timing at which the rise / fall of the spike detection signal generated by the CPU 11 is detected by interrupt processing. As shown in FIG. 2, the detection permission is prohibited → permitted synchronously when the switching elements 41U1, 41V1, 41W1 are switched from OFF to ON, respectively, and if the rise / fall of the spike detection signal is detected Permission is forbidden. It should be noted that this detection permission is also permitted → prohibited even when the rise / fall of the spike detection signal cannot be detected within a predetermined time (maximum permission time Tm shown in FIG. 3) after the prohibition → permission.

  When the brushless DC motor 200 is driven by field weakening control, if the drive control can be performed normally without step-out, the spike angle of the spike voltage generated in each phase is constant (Ru = Rv = Rw). The spike detection signal also repeats rising / falling at a constant cycle. Therefore, if the CPU 11 can detect the rise / fall of the spike detection signal, the CPU 11 can determine that no step-out has occurred in the brushless DC motor 200.

  On the other hand, when the step-out occurs in the brushless DC motor 200 and the spike angle increases, the width of the spike detection signal becomes wide, and the spike detection signal rises / falls while the CPU 11 permits detection in the interrupt processing. There is a possibility that it cannot be detected (hereinafter referred to as a step-out state). In addition, when a large load is applied to the CPU 11 and the operation of actually detecting the spike voltage waveform is delayed, and the load applied to the brushless DC motor 200 is reduced to reduce the spike angle, the spike detection signal rise / There is a possibility that the falling edge cannot be detected (hereinafter referred to as a non-detectable state).

  In the conventional brushless DC motor control device, when the out-of-step occurrence is detected by generating the spike detection signal and detecting the rise / fall as described above, the rise / fall of the spike detection signal is detected. Regardless of the cause of the failure, that is, whether it is in a step-out state or in a non-detectable state, it is determined that a step-out has occurred if the rising / falling edge of the spike detection signal cannot be detected continuously a predetermined number of times. The step-out protection control was performed.

On the other hand, in the controller 100 of the brushless DC motor 200 of the present invention, when the rising / falling of the spike detection signal cannot be continuously detected a predetermined number of times by the method described below, the cause is the brushless DC motor 200. Step out protection control is carried out if it is determined whether or not step out occurs.

  First, a case where step-out has occurred in the brushless DC motor 200 (step-out state) will be described with reference to FIG. In FIG. 3, detailed description of the same terms and symbols as in FIG. 2 is omitted.

  When step-out occurs in the brushless DC motor 200, the spike angle of the spike voltage that appears in the voltage waveform of each phase increases. As the spike angle increases, the width of the spike detection signal generated by the CPU 11 increases accordingly. At this time, if the width of the spike detection signal is so wide that it cannot be detected during the maximum permission time Tm of the detection permission, the CPU 11 cannot detect the rise of the spike detection signal. In FIG. 3, for example, the spike angle corresponding to the spike voltage waveform (U1a) appearing in the UN voltage waveform is increased to Rua (> Ru), indicating that the CPU 11 cannot detect the rising edge of the spike detection signal. . In FIG. 3, the rising edge of the spike detection signal that cannot be detected corresponding to the spike voltage waveform (U1a) is indicated by a broken line and “◯” is given.

  When the rising / falling edge of the spike detection signal cannot be detected, the CPU 11 reads the spike angle stored in the storage unit 15. As described above, the CPU 11 overwrites and stores the spike angle corresponding to the spike detection signal in the storage unit 15 when the spike detection signal rise / fall time can be detected at the detection permission timing. The spike angle of the spike voltage corresponding to the fall of the spike detection signal immediately before the rise of the spike detection signal that cannot be detected with “O” (the one with “◎”), that is, the spike voltage waveform that appears in the VN detection voltage ( The spike angle Rvj1 corresponding to V2j) is read out.

  Further, the CPU 11 reads out the step-out determination angle Rs (for example, 24 degrees in electrical angle) that is stored in advance in the storage unit 15 and is a threshold value for determining whether or not the brushless DC motor 200 has stepped out. The out-of-step determination angle Rs and the spike angle Rvj1 are compared to determine whether or not the spike angle Rvj1 is greater than or equal to the out-of-step determination angle Rs. In FIG. 3, since the spike angle Rvj1 is equal to or greater than the step-out determination angle Rs, the CPU 11 counts the number of times that the rising / falling of the spike detection signal cannot be detected: once. Specifically, in FIG. 3, when the rising edge of the spike detection signal to which “◯” is given is detected, the time is counted once when the detection permission time Tm has elapsed.

  When the brushless DC motor 200 is out of phase, since the spike angle of each phase after the spike angle of the UN voltage waveform is increased, the spike detection signal rises and falls thereafter as described above. It cannot be detected. In FIG. 3, the spike angle corresponding to the spike voltage waveform (W2a) appearing in the WN voltage waveform that is the source of generation of the spike detection signal next to the spike voltage waveform (U1a) is increased to Rwa (> Rw). The spike angle corresponding to the spike voltage waveform (V1a) appearing in the VN voltage waveform is also increased to Rva (> Rv), and the CPU 11 detects spikes corresponding to these spike voltage waveform (W2a) and spike voltage waveform (V1a). It indicates that the rising / falling of the signal cannot be detected. In FIG. 3, spike detection signals after the rising edge of the undetectable spike detection signal to which “◯” is given are indicated by broken lines, and “Δ” is given to the rising / falling edge that cannot be detected.

  The CPU 11 compares the step-out determination angle Rs and the spike angle Rvj1 each time when the spike detection signal rise / fall after the rise of the spike detection signal that could not be detected first cannot be detected. If the spike angle Rvj1 is greater than or equal to the step-out determination angle Rs, the number of times the spike detection signal rise / fall was not detected is counted. If this number of times continues for a predetermined number of times, for example, 5 times, the CPU 11 determines that the brushless DC motor 200 has stepped out, and stops energization of the brushless DC motor 200 to the motor drive circuit 7. An instruction is given via the PWM generator 12, and step-out protection control for stopping the brushless DC motor 200 is executed.

  Next, a case where a large load is applied to the CPU 11 and the operation of actually detecting the spike voltage waveform is delayed and the spike angle is small (detection disabled state) will be described with reference to FIG. In FIG. 4, detailed description of the same terms and symbols as in FIG. 2 is omitted.

  When the load applied to the brushless DC motor 200 is reduced, the spike angle of the spike voltage appearing in the voltage waveform of each phase may be small. Further, as described above, the CPU 11 detects the spike detection signal by an interrupt process, and when a large load is applied to the CPU 11, the switching elements 41U1, 41V1, 41W1 are turned off as shown in FIG. Even if it is prohibited → permitted in synchronization with switching to ON, the timing at which detection can actually be performed may be delayed by the time Tr from when the switching elements 41U1, 41V1, 41W1 are switched from OFF to ON.

  For example, as shown in FIG. 4, when the detection timing of the rise / fall of the spike detection signal is delayed by the time Tr, and the spike angle corresponding to the spike voltage waveform (U1b) appearing in the UN voltage waveform is Rub ( When <Ru) and the width of the spike detection signal generated by the CPU 11 based on this becomes narrow, the CPU 11 cannot detect the rise of the spike detection signal. In FIG. 4, the rising edge of the spike detection signal that cannot be detected corresponding to the spike voltage waveform (U1b) is indicated by a broken line and “◯” is given.

  When the rising / falling edge of the spike detection signal cannot be detected, the CPU 11 reads the spike angle stored in the storage unit 15. As described above, the CPU 11 overwrites and stores the spike angle corresponding to the spike detection signal in the storage unit 15 when the rise / fall of the spike detection signal can be detected at the detection permission timing. The spike angle of the spike voltage corresponding to the fall of the spike detection signal immediately before the rise of the spike detection signal that cannot be detected with “O” (the one with “◎”), that is, the spike voltage waveform that appears in the VN detection voltage ( The spike angle Rvj2 corresponding to V2j) is read out.

  Further, the CPU 11 reads out the step-out determination angle Rs (for example, 24 degrees in electrical angle) that is stored in advance in the storage unit 15 and is a threshold value for determining whether or not the brushless DC motor 200 has stepped out. The out-of-step determination angle Rs and the spike angle Rvj2 are compared to determine whether or not the spike angle Rvj2 is greater than or equal to the out-of-step determination angle Rs. In FIG. 4, since the spike angle Rvj1 is not greater than the step-out determination angle Rs, the CPU 11 determines that the brushless DC motor 200 has not stepped out and continues the field weakening control of the brushless DC motor 200.

  Even if the spike angle of the UN voltage waveform is reduced, if the spike angle of each phase continues to be small, the subsequent rise / fall of the spike detection signal cannot be detected as described above. In FIG. 4, the spike angle corresponding to the spike voltage waveform (W2b) appearing in the WN voltage waveform that is the source of generation of the spike detection signal next to the spike voltage waveform (U1b) is reduced to Rwb (<Rw). The spike angle corresponding to the spike voltage waveform (V1b) appearing in the VN voltage waveform is also reduced to Rvb (<Rv), and the CPU 11 detects spikes corresponding to these spike voltage waveform (W2b) and spike voltage waveform (V1b). It indicates that the rising / falling of the signal cannot be detected. In FIG. 4, spike detection signals after the rise of the undetectable spike detection signal to which “◯” is given are indicated by broken lines, and “Δ” is given to the rise / fall that cannot be detected.

  The CPU 11 compares the step-out determination angle Rs and the spike angle Rvj2 each time when the rising / falling edge of the spike detection signal cannot be detected after the spike detection signal that has not been detected first. Do. If the spike angle Rvj2 is not equal to or greater than the step-out determination angle Rs, the CPU 11 determines that the brushless DC motor 200 has not stepped out and continues field-weakening control of the brushless DC motor 200.

Next, the flow of processing in the CPU 11 in this embodiment will be described using the flowchart shown in FIG. The flowchart shown in FIG. 5 explains the flow of processing when the out-of-step occurrence in the brushless DC motor 200 is detected. ST represents a step and the subsequent number represents a step number.
Note that FIG. 5 mainly illustrates the processing related to the present invention, and description of other processing such as when the brushless DC motor 200 is driven by the above-described normal control is omitted.

  The CPU 11 of the control means 10 starts driving control of the brushless DC motor 200, and resets the number N of times when the spike detection signal rise / fall cannot be detected to 0 (ST1). Next, the CPU 11 generates a spike detection signal from the spike voltage waveform that appears in each phase (ST2). Next, the CPU 11 determines whether or not the rise / fall of the spike detection signal has been detected by the interrupt process (ST3).

  If the rising / falling of the spike detection signal can be detected (ST3-Yes), the CPU 11 stores the spike angle of the spike voltage of the phase corresponding to the detected rising / falling in the storage unit 15 (ST9), and processes to ST1. To return.

  If the rising / falling edge of the spike detection signal cannot be detected (ST3-No), the CPU 11 stores the spike angle Rj (Rvj1 and Rvj2 in this embodiment) and the step-out determination angle Rs (24 in this embodiment) from the storage unit 15. Degree) is read (ST4). Next, the CPU 11 compares the step-out determination angle Rs (24 degrees in this embodiment) with the spike angle Rj, and determines whether or not the spike angle Rj is greater than or equal to the step-out determination angle Rs (ST5).

  If the spike angle Rj is not greater than the step-out determination angle Rs (ST5-No), the CPU 11 returns the process to ST1. If the spike angle Rj is equal to or greater than the step-out determination angle Rs (ST5-Yes), the CPU 11 counts the number N of times that the spike detection signal rise / fall was not detected, that is, sets 1 to the previous number N. Add (ST6).

  Next, the CPU 11 determines whether or not the number N of times when the rising / falling of the spike detection signal could not be detected has reached a predetermined number Na (5 times in this embodiment) (ST7). If the number N is not Na (ST7-No), the CPU 11 returns the process to ST2. If the number of times N is Na (ST7-Yes), the CPU 11 executes step-out protection control for stopping energization of the brushless DC motor 200 (ST8), and ends the process.

  As described above, the motor control device of the present invention can accurately detect the occurrence of step-out in the motor using the generated spike detection signal and the width of the stored spike voltage. Unnecessary stopping of the motor can be avoided.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter circuit 3 Smoothing capacitor 4 Inverter circuit 5 Shunt resistance 6 Virtual neutral point voltage circuit 7 Motor drive circuit 8 Position detection circuit 9 Current detection circuit 10 Control means 11 CPU
DESCRIPTION OF SYMBOLS 12 PWM production | generation part 13 Input part 14 A / D conversion part 41U1, 41U2 Switching element 41V1, 41V2 Switching element 41W1, 41W2 Switching element 42 Free-wheeling diode 100 Control apparatus 200 Brushless DC motor

Claims (2)

A control device for an electric motor that converts direct current power into alternating current power by an inverter and supplies it to an electric motor, and performs rotation control of the electric motor,
The control device for the electric motor generates the spike voltage by allowing the detection of the spike voltage generated due to the return current generated at the time of switching after switching the energization to each phase of the motor for a predetermined time. Remember time,
When the control device of the electric motor cannot detect the rise or fall of the spike voltage, it reads the generation time of the spike voltage that was detected and stored last,
The control device of the motor, when the state generation time of the spike voltage read is the predetermined time or more has continued for a predetermined number of times, the control unit for an electric motor, characterized by determining that the electric motor is out of step .   2. The motor control device according to claim 1, wherein when it is determined that the motor has stepped out, step-out protection control is performed to stop the motor. 3.

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