JP2016163517A - Control method of permanent magnet motor and controller of permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiency control the drive of permanent magnet motor.SOLUTION: A rectification part 11 and a smoothing capacitor 13 rectify an AC voltage supplied from a single-phase AC power source 12 to generate a rectified voltage having a ripple; an inverter circuit 14 supplies the rectified voltage to a wiring 6 for period of time of a half cycle of an electrical angle period of a motor 7. A control circuit 16 stops from supplying the rectified voltage to the wiring 6 for a period of time when the rectified voltage detected via the voltage sensor 17 is smaller than a threshold level V.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a method and apparatus for controlling a permanent magnet motor.

  In a general brushless DC motor control method, when an energization period in which a voltage is applied to a winding according to a load (rotation speed or load torque) is provided, a phase precedes a zero crossing point of an induced voltage generated in the winding. There is an advance period to advance. The energization period and the advance period are controlled to be constant or to be changed according to the rectified voltage and the rotation speed (for example, refer to Patent Document 1).

Japanese Patent No. 5546496

  Home appliances use a DC voltage obtained by rectifying the voltage of a commercial AC power supply. However, in many cases, a smoothing capacitor having a small capacity is selected from the viewpoint of cost, and there is also a case where a smoothing capacitor is not provided. In such a case, the rectified voltage includes a ripple. In the motor control method disclosed in Patent Document 1, energization is performed even during a period when the level of the rectified voltage is low, but it is difficult to generate torque of the motor even when the winding is energized during the low voltage period. Reduces motor efficiency and increases torque ripple.

  Therefore, a permanent magnet motor control method and a permanent magnet motor control device capable of performing drive control more efficiently are provided.

  According to the first aspect of the present invention, when the rectified voltage obtained by rectifying the AC voltage to have a ripple state is applied to the winding of the motor during a period of a half cycle of the electrical angular cycle of the permanent magnet motor. In addition, the current supply to the winding is stopped during the period when the rectified voltage is equal to or lower than the threshold value.

The figure which is one Embodiment and shows the structure of a motor drive system Cross section of single-phase brushless permanent magnet motor viewed from the axial direction The figure which shows an example of the electricity supply pattern to a motor The figure which shows the electricity supply period in this embodiment, and the electricity supply period in a conventional method The figure which shows (a) winding current waveform and (b) torque waveform at the time of motor operation The figure which shows the winding current waveform when the energization period at the time of motor operation is (a) long and (b) short Flow chart showing contents of control by control circuit The figure which shows the electricity supply pattern and torque waveform by a conventional method and this embodiment.

  Hereinafter, an embodiment will be described with reference to the drawings. FIG. 2 is a cross-sectional view of a single-phase brushless permanent magnet motor (hereinafter referred to as a motor) viewed from the axial direction. The rotor 1 is composed of a shaft 2 and a permanent magnet 3 disposed on the outer periphery of the shaft 2, and the stator 4 is composed of an octagonal iron core 5 and a winding 6 wound around the iron core 5. Composed. The rotor 1 may include an iron core. The rotor 1 and the stator 4 constitute a motor 7. In addition, a position sensor 8 (position detecting means) is arranged to detect the position of the rotor 1.

  FIG. 1 shows a configuration of a motor drive system, and a rectification unit 11 (rectification means) composed of a diode bridge rectifies an AC voltage supplied from a single-phase AC power supply 12. A smoothing capacitor 13 (rectifying means) and a full bridge inverter circuit (hereinafter referred to as an inverter circuit) 14 are connected in parallel between the DC output terminals of the rectifying unit 11. The inverter circuit 14 (energizing means) is configured by connecting four switching elements SW1 to SW4 in a full bridge (H bridge), and free wheel diodes D1 to D4 are connected in parallel to the switching elements SW1 to SW4, respectively. It is connected. The output terminal of the inverter circuit 14 is connected to the winding 6 (not shown in FIG. 2) of the motor 7. For the switching elements SW1 to SW4, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET, a bipolar transistor, or the like is used.

  The position signal output from the position sensor 8 is input to the control circuit 16 (energization control means) via the position detection unit 15 (position detection means). The voltage sensor 17 (voltage detection means) detects the rectified voltage, which is the terminal voltage of the smoothing capacitor 13, and the output signal is input to the control circuit 16 via the voltage detection unit 18 (voltage detection means). The control circuit 16 is composed of a microcomputer, and controls each switching element SW1 to SW4 of the inverter circuit 14 by an energization pattern (energization period, advance period, etc.) according to the input rotor position and rectified voltage value, The motor 7 is driven. Here, when the capacity of the smoothing capacitor 13 is small (or when the smoothing capacitor 13 is not disposed), a relatively large level of ripple is generated in the rectified voltage. It is done.

  FIG. 3 is an example of an energization pattern of the motor 7. The control circuit 16 controls the energization period and the advance period according to the load (rotation speed, load torque), and energizes the winding 6. In this example, the switching elements SW1 and SW4 are simultaneously turned on during the period related to the rising edge of the position sensor signal, and the switching elements SW2 and SW3 are simultaneously turned on during the period related to the falling edge. The energization period is 120 ° (electrical angle), and the advance period is 50 ° (electrical angle).

  Further, when the rectified voltage has a ripple, the control circuit 16 adjusts the energization period and the advance period in accordance with the instantaneous value of the rectified voltage. In particular, when the motor 7 is rotating at a high speed, since there are many electrical angle cycles of the motor 7 within one cycle of the AC voltage, fine control may be performed for each electrical angle cycle. For example, when the AC power supply frequency is 50 Hz and the rotational speed is 75000 rpm, there are 25 electrical angle cycles within one cycle of the AC power supply, and fine control may be performed within each electrical angle cycle.

  FIG. 4 shows the energization period in the present embodiment and the energization period in the conventional method. In the conventional method, regardless of the level of the rectified voltage that varies due to the ripple shown in (a), (b) the energization period is controlled to be constant. In this case, in the period where the rectified voltage is low, torque is hardly generated in the motor even if the energization period is provided, which causes a reduction in efficiency and an increase in torque ripple.

  Therefore, in this embodiment, energization is not performed during a period when the level of the rectified voltage is low (the energization period is set to 0 °), and (c) a longer energization period is provided during a period when the level of the rectified voltage is high. Realize motor drive with high efficiency and low torque ripple. Therefore, energization is performed only during a period in which the level of the rectified voltage exceeds the threshold (in FIG. 4, for the convenience of illustration, the length of the energization period in this embodiment and the conventional method is the same image). The threshold value is determined so that the input current or the input power is minimized by adjusting the size of the non-energization period and the energization period so as to obtain a desired output (rotation speed and load torque). The energization period and the advance period may be controlled according to a constant or rectified voltage.

  Hereinafter, the above-described control principle will be described with reference to FIGS. FIG. 5 shows (a) winding current waveform and (b) torque waveform during motor operation. The current waveform is divided into the following three periods within an electrical angle half cycle. Each period is (1) an energization period, (2) a return period due to the inductance of the winding, and (3) a current period due to a change in magnet magnetic flux (indicated by circled numbers in the figure). In the periods (1) and (2), a current flows so as to generate a positive torque, but in a period (3), a current that generates a negative torque flows, so that the driving efficiency of the motor is reduced.

  FIG. 6 is a comparison according to the length of the energization period of the winding current waveform during motor operation. When the energization period of (b) is long, the current period due to the change of the magnet magnetic flux of (3) is short compared with the case of short (a), and it is difficult to generate negative torque in the motor. Therefore, it can be seen that the longer the energization period, the more efficiently the torque is generated.

Next, the effect | action of this embodiment is demonstrated with reference to FIG.7 and FIG.8. FIG. 7 is a flowchart showing the contents of control by the control circuit 16. The control circuit 16 detects the rectified voltage V via the voltage detector 18 (S1), and subsequently detects the rotor position and the rotational speed N of the motor 7 via the position detector 15 (S2). Then, the rotational speed N is compared with a threshold _{N th} (S3), the if _{(N ≦ N th) (NO} ) to produce the energization pattern corresponding to the rotational speed N (S8), the voltage of the generated power pattern The voltage is applied to the winding 6 of the motor 7 (S6). In this case, the energization pattern in step S8 is the same pattern as the conventional method shown in FIG.

On the other hand, if (N> N _th ) in step S3 (YES), the rectified voltage V is compared with the threshold value V _th (S4). Here, if (V ≦ V _th ) (NO), the winding 6 is not energized and the non-energized period is set (S7). If (V> V _th ) (YES), an energization pattern corresponding to the rotational speed N is generated (S5). In this case, if (V ≦ V _th ), a non-energization period is considered. Thus, the energization period is set longer than in the case of step S8. Then, the process proceeds to step S6. The motor rotation speed threshold N _th and the rectified voltage threshold V _th are determined so that the input current or the input power is minimized at a desired load point.

  FIGS. 8B and 8D are torque waveforms according to the conventional method and the present embodiment. In this embodiment, a non-energization period is provided, but an energization period longer than that in the conventional technique is provided in a period during which the rectified voltage V is high so that the average torque T ′ is equal to the average torque T in the conventional technique (( e)). In the present embodiment, energization is performed during a period of high rectified voltage where torque is likely to be generated, so that the driving efficiency of the motor 7 can be improved.

As described above, according to the present embodiment, the rectifier 11 and the smoothing capacitor 13 rectify the AC voltage supplied from the single-phase AC power supply 12 to generate a rectified voltage having ripples. The rectified voltage is energized to the winding 6 during a period over a half cycle of the electrical angular period of the motor 7. The control circuit 16 stops energization of the winding 6 during a period when the rectified voltage detected via the voltage sensor 17 is equal to or lower than the threshold value _Vth . Thereby, it is possible to improve the driving efficiency of the motor 7 without energizing the period during which the output torque of the motor 7 decreases. Further, an increase in torque ripple can be suppressed.

In this case, the control circuit 16, the rotational speed of the motor 7 stops energization of the winding 6 on a condition that exceeds the threshold N _th, the speed is hardly out high torque range of the motor 7, the effective Effects can be obtained. In addition, the control circuit 16, the rotational speed of the motor 7 is longer conduction period of the winding 6 exceeds the threshold value N _th, it can be generated efficiently torque to the motor 7.

(Other embodiments)
The smoothing capacitor 13 may be provided as necessary.
Steps S3 and S8 may be deleted for implementation.
It is not always necessary to make the energization period in the period where the rectified voltage V is high longer than in the conventional method.
Specific numerical values of the energization period and the advance period may be appropriately changed according to the individual design.
You may apply to a polyphase motor.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawing, 6 is a winding, 7 is a single-phase brushless permanent magnet motor, 11 is a rectifier (rectifier), 13 is a smoothing capacitor (rectifier), 14 is an inverter circuit (energizer), and 16 is a control circuit (energizer). Control means), 17 is a voltage sensor (voltage detection means), and 18 is a voltage detection section (voltage detection means).

Claims (6)

  When the rectified voltage obtained by rectifying the AC voltage to have a ripple state is applied to the winding of the motor during a period of a half cycle of the electrical angular period of the permanent magnet motor, the rectified voltage becomes a threshold value or less. A method for controlling a permanent magnet motor that stops energization of the winding during the period.   The method for controlling a permanent magnet motor according to claim 1, wherein energization of the winding is stopped when the rotation speed of the motor exceeds a threshold value.   3. The method of controlling a permanent magnet motor according to claim 1, wherein when the number of rotations of the motor exceeds a threshold value, the energization period to the winding is adjusted to be longer. Rectifying means for generating a rectified voltage that has a ripple by rectifying an AC voltage;
Energizing means for energizing the windings of the motor during a period over the half cycle of the electrical angular period of the permanent magnet motor;
Voltage detecting means for detecting the rectified voltage;
A control device for a permanent magnet motor, comprising energization control means for stopping energization of the winding during a period when the rectified voltage is equal to or less than a threshold value.   The control device for a permanent magnet motor according to claim 4, wherein the energization control unit stops energization to the winding when the rotation speed of the motor exceeds a threshold value.   The control device for a permanent magnet motor according to claim 4 or 5, wherein the energization control means adjusts the energization period to the winding to be longer when the rotation speed of the motor exceeds a threshold value.

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