JP2005204383A - Method of controlling brushless dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a field-weakening control to be performed sufficiently by enlarging a leading phase angle by a presumed phasing scheme which presumes the rotor phase of a brushless DC motor. <P>SOLUTION: A method of controlling the brushless DC motor includes a step of controlling the brushless DC motor 8 by calculating the time ts of a circulating current generated by switching the energization of a control circuit 20 in a range that cannot detect a rotor position by an induced voltage generated in a non-energizing phase when the brushless DC motor 8 is controlled, and outputting the drive signal of the energizing timing of the brushless DC motor 8 by the presumed phasing scheme IPM6 for presuming the rotor phase so that the circulating current time ts becomes the value corresponding to the predetermined number of rotations. The leading phase angle is enlarged by this presumed phasing scheme, thereby enabling the field-weakening control to expand the range of the number of rotations. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a lead phase control technology of a sensorless DC motor (brushless DC motor; IPM motor, etc.), and rotates in a region where the rotor position cannot be detected by an induced voltage (back electromotive force) generated in the motor non-energized phase. The present invention relates to a brushless DC motor control method that increases the number and expands the rotation speed range.

  The control device for controlling the inverter of the DC motor has a configuration shown in FIG. 9 when applied to, for example, a compressor. This control device passes an AC power source 1 through a noise filter 2 for removing harmonic noise and a reactor 3 for power factor correction, rectifies the AC power source 1 to a predetermined DC power source by a converter circuit 4, and smoothes this by a smoothing capacitor 5. It supplies to IPM (inverter means) 6.

  The IPM 6 is driven by a control circuit (microcomputer) 7, and the control circuit 7 sends a drive signal (including a PWM signal for the upper arm) to the motor drive circuit 9 for switching the switching elements of the upper and lower arms to a predetermined level. To IPM6. The IPM 6 has a plurality of upper and lower arm switching elements (such as IGBTs) configured as a bridge, and each switching element of the upper and lower arms releases the current generated by the accumulated energy of the motor winding to the input power source side at the moment of switching off. A free-wheeling diode is provided.

  As a result, the output (DC voltage) of the IPM 6 is converted to a three-phase rectangular wave voltage and applied to a sensorless DC motor (for example, a three-phase four-pole brushless DC motor) 8. A driving current flows through the brushless DC motor 8. Rotation torque is generated.

  At this time, the position of the rotor is detected to obtain the winding current switching timing of the stator. For example, when energization is switched by a 120-degree energization method or the like, the virtual neutral point voltage circuit 10 determines the non-energized phase of the brushless DC motor 8. A motor virtual neutral point voltage including an induced voltage waveform is obtained, and the position detection circuit 11 compares the motor virtual neutral point with a reference voltage to detect this intersection (zero cross point).

  When the position detection signal including the zero cross point is input to the control circuit 7, the control circuit 7 calculates the energization switching timing based on the position detection signal, and drives each switching element of the IPM 6 based on this timing. To output the drive signal for switching the stator winding current.

  Since the PWM control method is adopted, the control circuit 7 generates a PWM waveform having a predetermined duty ratio in order to calculate the current motor rotation speed from the position detection signal and set it as the target rotation speed. Is output to the IPM 6 and a predetermined rectangular wave voltage converted by the IPM 6 is generated to control the brushless DC motor 8 to the target rotational speed.

  In the above control method, for example, when the section in which phase energization is not performed is 60 degrees, and the configuration is such that the zero cross point of the induced voltage comes to the center of this section, the energization phase timing is in the range of 30 degrees before and after. Can only be controlled. In addition, if field weakening control is applied, the advance phase angle is small, that is, the energized phase timing is not so fast, and the effect of field weakening control is not sufficiently exhibited.

  For this reason, a method has been proposed in which a virtual neutral point to be compared with the induced voltage is changed to greatly advance the energization timing in order to detect the rotor position (see, for example, Patent Document 1). According to the invention of Patent Document 1, a virtual neutral point is obtained by dividing the bus voltage of the inverter, but a resistance circuit having a different voltage dividing ratio is configured by combining a resistance circuit and a switching element, and different virtual neutral points are obtained. Generate one.

  According to this, by using a low comparison voltage in addition to the normal comparison voltage as the virtual neutral point, the advance phase angle can be increased and the effect of field weakening control can be exhibited.

Japanese Patent Laid-Open No. 11-14685

  The problem to be solved by the present invention is applied within the PWM control range in the invention of Patent Document 1, but cannot be applied in a region where the rotor position cannot be detected by induced voltage, and the advance phase angle is increased. There is a point that can not.

  Specifically, the induced voltage waveform is hidden by the influence of the drive signal when the duty ratio of the PWM waveform reaches 100% and the return diode of the inverter circuit 3, the rotor position cannot be detected, and the motor current is increased by increasing the load. When the voltage increases, the induced voltage cannot be detected.

In the synchronous motor, when the driving torque or load of the motor fluctuates, an elastic vibration system (J · 1 / p · (d ² δ / dt ² ) + Td · (dδ / dt) + Ts = Tm is expressed. Vibration of internal phase difference angle δ). J is the moment of inertia, p is the number of poles, the first term of the above equation is the inertia torque, the second term is the braking torque (Td; coefficient), and the third term is the synchronous torque.

  As is clear from the above equation, when the vibration becomes significant, the motor becomes turbulent, which is not preferable from the viewpoint of noise, damage to the refrigerant piping of the compressor, and efficiency. Therefore, in the current turbulence suppression control, a change in the rotor phase is detected and the commutation timing is adjusted so that the phase approaches a constant value, that is, the energization timing is corrected to correct the rotation speed.

  In this case, in order to suppress adverse effects due to erroneous detection of the rotor phase or the like, integral control is formed in which the feedback gain of the rotation control is only the integral term. This contributes to the stability of the system including the motor, but may not be able to follow when the amount of turbulence is large or when the motor current fluctuates rapidly. Therefore, even in the advance phase control, if the turbulence is not suppressed as an actual problem, it will affect the expansion of the high rotation speed region.

  In order to solve the above-mentioned problems, the present invention converts an AC power source into a predetermined DC voltage and supplies it to the brushless DC motor by the inverter means. When switching the energization of the brushless DC motor, the invention obtains the inverter means. In a brushless DC motor control method for controlling rotation by applying a predetermined voltage to the brushless DC motor, the motor rotation speed becomes a predetermined value based on the time ts of the return current generated when the energization is switched. Thus, the brushless DC motor is controlled by an estimated phase method for estimating the motor phase.

  Further, the present invention converts the AC power source into a predetermined DC voltage and supplies it to the brushless DC motor by the inverter means. When switching the energization of the brushless DC motor, the predetermined voltage obtained by the inverter means is used. In the brushless DC motor control method in which rotation control is performed by applying to the brushless DC motor, the time ts of the return current generated when the energization is switched is set to a value corresponding to a predetermined motor rotational speed obtained in advance. An open loop in which the brushless DC motor is controlled by an estimated phase method for estimating the rotor phase and the estimated phase is set to a large advance phase angle while the return current time ts does not exceed a predetermined value. It is characterized by performing control.

  The return current time ts is calculated based on the current switching timing and the waveform signal including the induced voltage, and the predetermined value for limiting the return current time ts is at least the ambient temperature of the apparatus. The higher the value, the smaller the value.

  In the present invention, when switching the energization of the brushless DC motor, the induced voltage is controlled when the inverter means is controlled based on the rotor position detected by the induced voltage generated in the non-energized phase of the brushless DC motor. Thus, the control based on the estimated phase method is preferably executed in a region where the rotor position cannot be detected.

  The current flowing through the inverter means (overcurrent, reverse current or bus current) is detected. When the detected current exceeds a preset value, it is determined that the motor has stepped out and protection is performed. When the motor is stopped by the operation, the predetermined value for limiting the return current time ts may be lowered by a preset amount in restarting the motor.

  When the input AC current flowing through the AC power source is detected, and the detected current exceeds a predetermined value set in advance, it is determined that the motor has stepped out and protection operation is performed, and the motor is stopped by the protection operation. In the restart, the predetermined value for limiting the reflux current time ts may be lowered by a preset amount.

  In the present invention, in the region where the rotor position cannot be detected by the induced voltage, the motor phase is estimated so that the time ts of the return current generated when the energization is switched becomes a value corresponding to a predetermined motor speed. The brushless DC motor is controlled by a phase method, and the estimated phase is set to a large advance phase angle to allow the rotation speed range to be expanded. On the other hand, when the energization timing is obtained based on the return current time ts, the return current A mode is included in which the time ts is compared with the previously obtained return current time ts, and the energization timing is corrected so as to suppress motor turbulence based on the comparison result.

  In this case, the fluctuation amount of the bus current of the inverter means is detected, the magnitude of the motor turbulence is estimated from the fluctuation quantity, and the energization timing is estimated so as to correct the rotation speed according to the magnitude of the turbulence. It is preferable.

  According to the present invention, the region where the rotor position cannot be detected by the induced voltage generated in the non-energized phase, for example, the region where the PWM duty ratio reaches 100% and the rotor position cannot be detected, or the PWM duty ratio becomes close to 100%. Since the rotor phase is estimated by using the time ts of the return current generated by the energization switching, the advance phase angle is increased so as to increase the return current time ts, and the field weakening control is sufficiently exerted to rotate. For example, in the case of an IPM motor, the reluctance torque is also generated, and the effect that the motor can be highly efficient can be expected.

  Further, since the return current time ts does not exceed a preset limit value, the motor can be prevented from stepping out and the motor demagnetization and the switching element of the inverter circuit 4 can be prevented from being damaged. In addition, since the limit value is changed according to the ambient temperature of the device, motor step-out can be more appropriately prevented according to the use environment of the device, and damage to components and the like can be prevented.

  Further, since the current (overcurrent or reverse current or bus current) of the IPM (inverter means) 6 and the input AC current are detected and the motor step-out is determined based on the detected current, the device and the motor are appropriately protected. In addition, since the limit value of the return current time ts is reduced by a predetermined amount in restarting the motor after the motor step-out is judged and stopped, the motor step-out is suppressed, and as a result Expansion of the rotation speed region can be realized.

  Further, since the energization timing is corrected so that the amount of change in the return current time ts (the comparison result of the current return current time and the previous return current time) is reduced, the effect of suppressing motor turbulence can be achieved. Can be expected.

  Further, since the energization timing is corrected so that the fluctuation amount of the bus current of the inverter means becomes small, motor turbulence can be suppressed, and noise, refrigerant pipe breakage of the compressor, and the like can be prevented.

  The control method of the brushless DC motor of the present invention aims to increase the lead phase angle and expand the rotation speed range as a higher rotation speed at least in a region where position detection by the motor induced voltage waveform cannot be performed. Utilizing the fact that the return current time (commutation spike voltage width) ts reflects the current phase angle of the motor, the phase angle (energization timing) is estimated and realized so that the return current time ts becomes larger. To do.

  Another object of the present invention is to reduce the difference between the return current time ts and the previous return current time ts so as to reduce the motor turbulence and to expand the high rotation speed region, and to generate a bus of the inverter means. This is realized by correcting the estimated energization timing so that the amount of fluctuation in current becomes small.

  FIG. 1 is a block diagram of a control device to which the brushless DC motor control method of the present invention is applied. In the figure, the same parts as those in FIG.

  In FIG. 1, this control device uses the current commutation interval information (energization timing) and the position information (commutation spike voltage waveform) from the position detection circuit 11 to determine the commutation spike voltage width (so-called return current time ts). Is provided with a control circuit (microcomputer) 20 that estimates the energization timing so that the return current time ts is increased to control the advance phase angle. The control circuit 20 also has the function of the control circuit 7 shown in FIG.

  The return current is a reverse current that flows to the input side via the return diode at the commutation timing in the IPM 6, and the return current time ts is a time for which the reverse current flows as shown in FIG.

  Further, as shown in FIG. 3, when the current phase angle (corresponding to the energization phase angle) increases, the reflux angle (corresponding to the reflux current time ts) increases. That is, the time during which the reflux current flows is proportional to the square of the inductance and the motor current. Accordingly, the advance phase angle can be increased by determining the energization timing so that the return current time ts is increased.

  In addition to the control circuit 20 and the like, the control device includes a shunt resistor 21 provided between the converter circuit 4 and the IPM 6, and an overcurrent detection circuit that detects an overcurrent of the IPM 6 via the shunt resistor 21. 22, a reverse current detection circuit 23 for detecting the reverse current of the IPM 6, a bus current detection circuit 24 for detecting the bus current of the IPM 6, a current sensor (CT) 25 provided on the input side of the converter circuit 4, An input current detection circuit 26 that detects an input current via the CT 25 is provided.

  These detected currents are input to the control circuit 20 via the A / D conversion port and the input port (INT), and processing necessary for protection of the device is executed. A position signal from the position detection circuit 11 is input to the control circuit 20 through an input port (INT), and a drive signal for the IPM 6 is output from the output port of the control circuit 20.

  When the apparatus is applied to an air conditioner outdoor unit compressor, for example, the control circuit 20 is brushless in accordance with the outdoor unit system 20a and instructions from the outdoor unit system 20a (such as a remote control signal and compressor frequency information via the indoor unit). A rotational speed controller 20b that controls the rotational speed of the DC motor 8 and controls it for each protection, and a PWM generation controller that generates a PWM waveform and superimposes it on the drive signal (for example, only the upper arm drive signal) of the IPM 6 20c functions are provided.

  The advance phase angle control in the control circuit 20 will be described with reference to the block diagram of the rotation speed controller 20b shown in FIG. 4. A deviation between the target frequency and the actual frequency is calculated by the calculator 20ba, and according to this deviation. The command rotational speed calculator 20bb generates a command frequency, and the phase adjuster 20bc generates an inverter phase angle (energization signal) based on the command actual rotational speed to control the IPM 6, while the brushless DC motor 8 is driven by the phase angle. The flow information (interval) is output to the actual frequency calculator 20bd.

  The actual frequency calculator 20bd calculates and feeds back the actual frequency in consideration of the input position information and commutation information. On the other hand, when the position cannot be detected by the input position information, the actual frequency calculator 20bd uses the commutation information and position information. Based on the spike voltage information included, the actual frequency for increasing the return current time ts (increasing the advance phase angle) is calculated and fed back. As a result, the phase adjuster 12c calculates the energization timing based on the large advance phase angle and controls the IPM 6, thereby increasing the actual motor rotation speed.

  The operation of the control device having the above configuration will be described with reference to the flowchart of FIG. 5. First, the control circuit 20 outputs a drive signal (an energization signal including a PWM waveform) to the IPM 6 in the same manner as in the prior art, thereby While controlling the rotation, the actual rotation speed is controlled to the target rotation speed.

  At this time, the number of rotations of the rotor is calculated from the position information (detection signal), and the rotor position detection timing is predicted, that is, the next position detection prediction time is calculated. Based on this, the phase timing (that is, commutation) is calculated. Timing) to control the rotation of the motor. However, for example, due to the influence of the drive signal when the duty ratio of the PWM waveform reaches 100% and the return diode of the inverter circuit 3, the induced voltage waveform is hidden, so that the position cannot be detected.

  When the rotor position cannot be detected, the rotational speed is increased by the advance phase angle control. That is, the return current time ts is calculated based on the current energization timing (commutation information) and the spike voltage waveform included in the position information, and the phase angle is estimated so that the return current time ts becomes larger. The switching elements of the IPM 6 are driven with the energization timing based on the estimated phase angle.

  Specifically, the target frequency is compared with the actual frequency (step ST1), and when the target frequency is greater than the actual frequency, it is determined whether or not the return current time ts is less than or equal to the limit value (step ST2). That is, the current phase increases due to the characteristics of the return current shown in FIG. 3, and in particular, as the current phase exceeds 60 degrees and approaches 90 degrees, it is necessary to limit the return current time ts for the motor to step out. Because.

  Therefore, the limit value of the return current time ts at which the motor does not step out within the range of the return angle and current phase angle, the return angle (corresponding to the return current time ts) 60 degrees, and the current phase angle 90 degrees shown in FIG. Is determined empirically in advance by considering the load and the like for each rotation speed, and these limit values are stored in the internal memory of the control circuit 20.

  When the return current time ts is less than or equal to the limit value in the current rotation speed, the output frequency is set to the previous output frequency + a predetermined value (for example, 0.1) (step ST3), that is, the return current time ts corresponds to the output frequency. The energization timing is estimated so as to be a value, and the rotation of the motor is controlled.

  The above steps are repeated until the actual frequency reaches the target frequency to increase the return current time ts, and the advance phase angle is sequentially increased. Thereby, since the return current time ts is made longer, the advance phase angle can be made larger than before, and the motor rotation speed can be increased.

When the return current time ts is larger than the limit value, the output frequency is set to the previous output frequency minus a predetermined value (for example, 0.1) (step ST4). As a result, the advance phase angle does not become too large, that is, the motor rotation speed does not increase, and the above-mentioned motor step-out does not occur.
When the target frequency is smaller than the actual frequency, the process proceeds from step ST1 to ST5, and the output frequency is set to the previous output frequency minus a predetermined value (for example, 0.1).

By performing the advance phase angle control in this way, it is possible to lead the motor rotational speed to the target rotational speed and to enlarge the high rotational speed region.
In addition, if an IPM motor is used as the brushless DC motor 8, reluctance torque is generated along with magnet torque, but the reluctance torque is sufficiently generated even in a region where position detection by induced voltage cannot be performed, coupled with the field weakening control. Expected to increase motor efficiency and expand motor operating range.

  Further, since the motor rotation speed is limited by the above limit value, it is possible to prevent the motor from stepping out, and to prevent the motor demagnetization and the switching element of the IPM 6 from being damaged. Note that the above limit value is determined in consideration of the load, etc., but for example when the motor is housed in a refrigeration cycle such as a compressor, the refrigeration cycle load may vary depending on the ambient temperature. May be calculated and tabulated for each ambient temperature of the device, stored in the internal memory of the control circuit 20, and the limit value may be switched by monitoring the ambient temperature.

  In this case, it is necessary to provide the apparatus with a temperature sensor. For example, an apparatus such as an air conditioner is already provided with the temperature sensor. The limit value may be changed for each ambient temperature, and the limit value may be set to a smaller value as the ambient temperature is higher.

  By the way, the advance phase angle control described above controls the advance phase angle with the return current time ts, that is, does not directly feed back the rotor rotation state (rotation phase), and is open loop control. Therefore, the protection of the device may not be sufficient only by limiting the return current time ts.

  An embodiment for protecting the device will be described. A reverse current flowing through the IPM 6 is detected by a shunt resistor 21 and a reverse overcurrent detection circuit 23 provided in the control device. Perform protection when the value is reached. This protection operation, like the operation performed based on the overcurrent detected by the shunt resistor 21 and the overcurrent detection circuit 22, lowers the rotation speed of the motor or temporarily stops the motor.

  The predetermined value as the criterion for determining the protective operation may be obtained empirically. For example, the reverse current value that flows through the IPM 6 when the current phase angle shown in FIG. That is, it is necessary to make the current phase angle lower than 90 degrees. Thereby, the said apparatus and motor can be protected and the step-out of a motor can be prevented.

  As the protection, the shunt resistor 21 and the bus current detection circuit 24 are used to detect the bus current (current in the negative direction) of the IPM 6, and the control circuit 20 is in a motor step-out state when the bus current is a predetermined value or more. The protection operation may be performed based on the determination. That is, when the motor is stepped out, a negative bus current is generated.

  Further, the step-out state may not be detected by the above-described method for determining motor step-out. This is because, for example, the motor may step out even if the reverse overcurrent does not reach a predetermined value or the negative bus current does not exceed a predetermined value depending on the use environment and load of the motor.

  Therefore, the input current (AC current) of the device is detected using the current sensor (CT) 25 and the input current detection circuit 26, and the control circuit 20 monitors the AC current based on the detected input current to determine motor step-out. Good. That is, when the motor steps out, the motor current is regenerated in the IPM 6, thereby reducing the value of the current supplied from the AC power supply 1.

  In this case, a predetermined value of the AC current in the motor step-out state is empirically obtained in advance for each rotation speed, and these values are stored in the internal memory of the control circuit 2, and the detected AC current value is the predetermined value. If it is smaller, it is determined that the motor has stepped out and the protection operation is performed.

  When the motor is restarted after determining the motor step-out described above and performing the protection operation, the return current limit value (limit value) may be lowered by a predetermined amount. Thereby, the advance phase angle is suppressed and the motor rotation speed is suppressed in the high rotation speed region, but the motor step-out can be suppressed and the trouble of the control (decrease in operating efficiency, etc.) can be solved.

  In this embodiment, in order to suppress motor turbulence using the advance phase angle control, the return current time ts obtained in the above embodiment is compared with the previous return current time ts, and the result is obtained as the advance phase angle. It is used for control, that is, the energization timing is corrected.

  Referring to the flowchart of FIG. 6, first, the control circuit 20 calculates the return current time ts (step ST10). If the return current time ts is previously calculated in the above embodiment, the control circuit 20 calculates the return current time ts. May be used. The return current time ts is stored in the internal memory of the control circuit 20 and updated every time the energization is switched.

  Subsequently, the previous return current time ts-α is compared with the current return current time ts (step ST11). When the previous return current time ts-α is smaller than the current return current time ts, In order to reduce the difference, the current correction value is set to the previous correction value + β (step amount; for example, 2 μsec) (step ST12). Α (predetermined value; for example, 4 μsec) is a hysteresis width for preventing the hunting of the turbulence suppression control, and the correction value is stored in the internal memory of the control circuit 20 and is updated as with the return current time ts. .

  It is determined whether or not the calculated correction value is larger than γ (maximum correction amount; for example, 8 μsec) (step STST13). When the correction value is larger than γ, the correction value is limited as γ (step ST14). ). The next energization timing is corrected by the correction value thus obtained (step ST15). That is, if the current return current time ts is longer than the previous return current time ts, the motor rotation speed tends to decelerate, so the correction value is increased to suppress the decrease in the rotation speed, that is, to suppress turbulence. To do.

  However, when the correction value is γ or less, the correction value is left as it is, and the next energization timing is corrected by this correction value (step ST15). As a result, the correction value does not increase more than necessary, so that the rotation speed does not change significantly, that is, the occurrence of turbulence can be prevented.

  Subsequently, as a result of comparison between the previous reflux current time ts-α and the current reflux current time ts, when the previous reflux current time ts-α is larger than the current reflux current time ts, the difference is calculated. In order to reduce the number, the current correction value is set to the previous correction value−β (step amount) (step ST16).

  It is determined whether or not the calculated correction value k satisfies −α ≦ k ≦ + α (step ST17), and when the correction value k is in the range of −α ≦ k ≦ + α, the calculated correction value− The next energization timing is corrected by β (step ST15). That is, if the current return current time ts is smaller than the previous return current time ts, the motor rotation speed tends to increase. Therefore, the correction value is reduced to suppress the increase in the rotation speed, that is, to suppress turbulence. To do.

  However, when the correction value k is larger in the negative direction than -α or larger than + α, the correction value is limited to γ (step ST18), and the next energization timing is corrected by the correction value (step ST15). That is, the rotational speed of the motor is prevented from excessively decreasing, that is, turbulence is suppressed.

  Thus, when the advance phase angle control is performed because the position cannot be detected by the induced voltage, when the energization timing is estimated based on the return current value ts, the return current value ts is monitored for each energization timing. Since the energization timing is corrected, the motor turbulence can be suppressed.

  In the present embodiment, the motor rotation speed is corrected so that the fluctuation amount of the bus current of the inverter means is detected and reduced for a certain period (determination period) shown in FIG. For the control device that realizes this embodiment, refer to the configuration shown in FIG.

  When the induced voltage cannot be detected and the motor is controlled to the target rotational speed by the advance phase control, the control circuit 20 executes the routine shown in FIG. 8 and first performs predetermined sampling from the detection signal from the bus current detection circuit 24. A bus current is detected for each cycle (step ST20).

  Subsequently, it is determined whether or not the bus current is larger than the MAX bus current (step ST21). Since the MAX bus current is not determined at first, it is determined as 0A, and the detected bus current is larger than 0A. Therefore, this is set as a MAX bus current (step ST22).

  It is determined whether the bus current is smaller than the MIN bus current (step ST23). Since the MIN bus current is not determined at first, it is determined as 50A in the current range, and the detected bus current is determined from 50A. Since it is low, this is used as the MIN bus current (step ST24).

  Subsequently, a counter for the number of bus current samplings in the predetermined period is incremented (step ST25), and it is determined whether or not the value of the counter has reached a predetermined value (step ST26).

  If the bus current is not detected for the number of times of sampling in the certain period, the routine is terminated once, the process returns to step ST1, and the above-described processing is repeated. When the sampling bus current is larger than the MAX bus current, it is updated to the MAX bus current (steps ST21 and ST22), but when the bus current is smaller than the MAX bus current and smaller than the MIN bus current, it is updated to the MIN bus current. (Steps ST23 and ST24).

  As a result, steps ST20 to ST26 are executed as many times as the number of samplings, and the minimum value of the bus current in a certain period is obtained (see FIG. 7). Subsequently, after the counter is cleared (step ST27), the current ratio (that is, current fluctuation rate) of the bus current in the fixed section is set to the maximum value (MAX bus current) / minimum value (MIN) using the minimum value and the maximum value. (Bus current) is calculated (step 28).

  Subsequently, it is determined whether or not the calculated current ratio is larger than a predetermined value (step ST29). The predetermined value is a value empirically obtained in advance (ripple limit value; normally generated current ripple value).

  When the current ratio is larger than the ripple limit value, motor turbulence has occurred or has occurred, and the output rotational speed is decreased by a predetermined value (for example, 0.1 rps), that is, the motor rotational speed is decreased (step ST30). Then, the MAX bus current is set to 0A, the MIN bus current is set to 50A, and the turbulence suppression control in the next fixed section (determination section) is performed.

  As described above, since the motor output rotational speed is corrected for each fixed section, the motor turbulence can be suppressed as in the third embodiment, and the motor noise and the compressor refrigerant piping can be prevented from being damaged. Can do. The turbulence suppression control based on the amount of fluctuation of the bus current may be performed after the turbulence suppression control based on the amount of change in the return current time ts described above. According to this, the suppression of motor turbulence is more effectively suppressed. As a result, the expansion of the high rotation speed region in the advance phase angle control is not impaired.

  Since the range of the rotational speed of the brushless DC motor 8 is expanded, it can be used for general home appliances equipped with fans, compressors, etc. to improve their functions, especially in air conditioners and refrigerators equipped with compressors. It is possible to improve the performance by using them.

The schematic block diagram explaining the control apparatus with which the control method of the brushless DC motor which shows the Example of this invention is applied. (Examples 1, 2, 3, 4) FIG. 2 is a schematic waveform diagram for explaining the operation of the control device shown in FIG. 1. (Examples 1 and 2) The schematic graph explaining operation | movement of the control apparatus shown in FIG. FIG. 2 is a schematic partial schematic diagram for explaining a control circuit constituting the control device shown in FIG. 1. The schematic flowchart figure explaining operation | movement of the control apparatus shown in FIG. The schematic flowchart figure explaining the Example of this invention. Example 3 The schematic graph explaining the Example of this invention. (Example 4) The schematic flowchart figure explaining the Example of this invention. The schematic block diagram explaining the control apparatus of the conventional brushless DC motor.

Explanation of symbols

1 DC power supply 4 Converter circuit 6 IPM (inverter means)
7,20 Control circuit (microcomputer)
8 DC motor (brushless DC motor; IPM motor)
DESCRIPTION OF SYMBOLS 10 Virtual neutral point voltage circuit 11 Position detection circuit 21 Shunt resistance 22 Overcurrent detection circuit 23 Reverse current detection circuit 24 Bus current detection circuit 25 Current sensor (CT)
26 Input current detection circuit ts Return current time

Claims (8)

An AC power source is converted into a predetermined DC voltage and supplied to the brushless DC motor by the inverter means, and when the energization of the brushless DC motor is switched, the predetermined voltage obtained by the inverter means is applied to the brushless DC motor. In the control method of the brushless DC motor that performs rotation control by
The brushless DC motor is controlled by an estimation phase method that estimates a motor phase so that a motor rotation speed becomes a predetermined value based on a time ts of a return current generated when the energization is switched. Motor control method. An AC power source is converted into a predetermined DC voltage and supplied to the brushless DC motor by the inverter means, and when the energization of the brushless DC motor is switched, the predetermined voltage obtained by the inverter means is applied to the brushless DC motor. In the control method of the brushless DC motor that performs rotation control by
The brushless DC motor is controlled by an estimation phase method for estimating the rotor phase so that the time ts of the return current generated when the energization is switched becomes a value corresponding to a predetermined motor rotational speed obtained in advance. A control method for a brushless DC motor, wherein open-loop control is performed so that the return current time ts does not exceed a predetermined value while the phase is set to a large advance phase angle.   The return current time ts is calculated based on the current switching timing and a waveform signal including the induced voltage, and the predetermined value for limiting the return current time ts is smaller as the ambient temperature of the apparatus is higher. The method for controlling a brushless DC motor according to claim 1, wherein:   When switching the energization of the brushless DC motor, when the inverter means is controlled based on the rotor position detected by the induced voltage generated in the non-energized phase of the brushless DC motor, the rotor position is detected by the induced voltage. 4. The method of controlling a brushless DC motor according to claim 1, wherein the control based on the estimated phase method is executed in a region where it cannot be performed.   A current that flows through the inverter means is detected, and when the detected current exceeds a preset predetermined value, the motor is stopped, and when the motor is restarted, a preset value that limits the return current time ts is set in advance. 5. The method of controlling a brushless DC motor according to claim 1, wherein the brushless DC motor is lowered only by a predetermined amount.   An input AC current flowing through the AC power supply is detected, and the motor is stopped when the detected current falls below a predetermined value set in advance. A predetermined value that limits the return current time ts is set in advance when the motor is restarted. The brushless DC motor control method according to any one of claims 1 to 4, wherein the brushless DC motor is lowered by a predetermined amount. When the AC power is converted into a predetermined DC voltage and supplied to the brushless DC motor by the inverter means, and the energization of the brushless DC motor is switched, it is detected by the induced voltage generated in the non-energized phase of the brushless DC motor. In the control method of the brushless DC motor, which controls the inverter means based on the rotor position, and applies a predetermined voltage obtained by the inverter means to the brushless DC motor to control the rotation.
When obtaining the energization switching timing based on the return current time ts generated when the energization is switched, the energization timing is corrected by comparing the return current time ts with the previously obtained return current time ts. A control method for a brushless DC motor. When the AC power is converted into a predetermined DC voltage and supplied to the brushless DC motor by the inverter means, and the energization of the brushless DC motor is switched, it is detected by the induced voltage generated in the non-energized phase of the brushless DC motor. In the control method of the brushless DC motor, which controls the inverter means based on the rotor position, and applies a predetermined voltage obtained by the inverter means to the brushless DC motor to control the rotation.
The amount of fluctuation of the bus current of the inverter means is detected, the magnitude of the motor turbulence is estimated from the amount of fluctuation, and the energization timing is set so as to correct the rotation speed according to the magnitude of the turbulence. A control method of a brushless DC motor.

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