JP2002186274A - Brushless dc motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless DC motor controller which can generate a high output by effectively utilizing a power source voltage. SOLUTION: This brushless DC motor controller comprises a first magnetic pole position detecting means for detecting a magnetic pole position for the duty angle of 120 deg., by detecting an induced voltage from a motor input terminal of Y (star)-connected armature coil in the non-duty section; and a second magnetic pole position detecting means for detecting a magnetic pole position when the duty angle is wider than 120 deg. from a variation of potential difference between the neutral point of the armature coil and the neutral point of the Y (star)-connected resistance element connected in parallel to the armature coil. For the setting of the duty angle or the like, a plurality of operation patterns are provided in the form of a table respectively for the rotating area, a value of motor current, a DC voltage of inverter, modulation rate of PWM waveform, and a torque of motor load, and the optimum operation pattern is selected for respective operating conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for a brushless DC motor for a compressor of an air conditioner.

[0002]

2. Description of the Related Art In recent years, a brushless DC motor controlled by an inverter has been used in most cases as a compressor driving motor of a small air conditioner (air conditioner). The main body of the brushless DC motor has a synchronous motor structure. The inverter controls the voltage and frequency applied by detecting the magnetic pole position to perform a closed loop operation, generate a predetermined torque, and generate a predetermined rotation speed. Rotate with. 11 and 12 are block diagrams showing a configuration of a brushless DC motor for driving a compressor according to a conventional technique.

In FIG. 11, the voltage of each phase by the inverter unit 4 is set to a conduction angle of 120 °, and the Y (star)
By taking the input signals of the connection armature windings 51U, 51V and 51W into the first magnetic pole position detecting means 8, three times the electric rotation speed obtained by comparing the induced voltages of the respective phases generated during the non-energization period with each other. The magnetic pole position is detected from the signal of the frequency of (1), and a control instruction is given to the microcomputer 90 of the inverter control circuit 9.

Next, FIG. 12 is different from FIG.
The signal input to the magnetic pole position detecting means 7 is Y (star).
This is a point obtained from the neutral point of the armature winding of the connected motor 5 and the neutral point of the Y (star) connection resistance connected in parallel to the input terminal of the armature winding. In this method, the position of the magnetic pole of the motor 5 is detected by detecting a magnetic pole position using a potential difference fluctuation having a frequency component three times the electric rotation speed generated between the neutral point of the armature winding and the neutral point of the resistance. Perform closed loop control. According to the method of FIG. 12, the voltage applied to the motor 5 can be wide-angle energization such as 180 ° energization.

[0005]

However, the first method described above has a problem that the voltage of the power supply cannot be used effectively because the conduction angle is fixed at 120 °. Further, the conduction angle is set to 120 ° or more (for example, 170 °).
(°), there is a problem that the magnetic pole position cannot be detected with high accuracy. In addition, the second
The method has a problem that the magnitude of the signal of the frequency component three times the electric rotation speed between the neutral points obtained in the low rotation region is small, and it is difficult to detect the magnetic pole position with high accuracy.

The present invention has been made under such a background, and it is possible to effectively use the energizing angle from 120 ° to 180 °, and to provide means for accurately detecting the magnetic pole position at this time. Accordingly, an object of the present invention is to provide a control device for a brushless DC motor that enables high-speed operation by effectively utilizing a power supply voltage.

[0007]

According to the first aspect of the present invention, there is provided a control device for a brushless DC motor, comprising: a rotation speed, a magnitude of a motor current, an inverter DC voltage, and a PWM.
An operation pattern table in which a plurality of operation patterns are tabulated for each of the waveform modulation rate and the torque of the motor load is provided, and an optimum operation pattern for each operation condition is selected from the operation pattern table. A control device for a brushless DC motor, which is operated.

According to the present invention, the energization angle is set in the rotation region, the magnitude of the motor current, the inverter DC voltage, the PWM
The motor loss can be reduced by selecting the optimal pattern for the operating conditions from the operating patterns provided for the waveform modulation rate and the torque value of the motor load, thereby reducing motor loss. Is improved.

According to a second aspect of the present invention, in the control device for a brushless DC motor according to the first aspect, an operation pattern having an energization angle of 120 ° is selected and started in an open-loop operation, and 120 ° in a low-speed rotation region. Select the operation pattern of the current-carrying angle and perform closed-loop operation by detecting the magnetic pole position.
In the high-speed rotation region, a closed-loop operation is performed by detecting a magnetic pole position by selecting an operation pattern with a wide-angle conduction angle of 120 ° or more, and the conduction angle and PWM (pulse width modulation) in the medium-speed rotation region.
It is characterized in that a closed-loop operation by detecting a magnetic pole position is performed by selecting an operation pattern for controlling a conduction angle so as to reduce a motor current waveform distortion by combining a combination of waveform modulation rates.

According to the present invention, the distortion of the motor current waveform is reduced and harmonic components are reduced by making the conduction angle variable in the rotation region and making the conduction angle of the inverter 120 ° in the low-speed rotation region. And motor efficiency is improved. In the high-speed rotation region, by setting the conduction angle to be a wide angle of 120 ° or more (for example, 180 °), it is possible to effectively use the inverter input voltage.
° Since the voltage applied to the motor can be made higher than when energized, the maximum rotation speed can be increased.
Further, in the medium speed rotation region, even under the same load condition, the distortion of the motor current waveform can be reduced by the combination of the conduction angle and the modulation factor of the PWM waveform, the motor loss is reduced, and the motor efficiency is improved.

According to a third aspect of the present invention, in the control device for a brushless DC motor according to the first or second aspect, instead of starting the open loop operation by the 120 ° conduction angle,
It is characterized in that an operation pattern with a conduction angle of 180 ° is selected, the operation is started in an open-loop operation, and the operation is returned to an operation pattern with a conduction angle of 120 ° immediately before shifting to a closed-loop operation.

According to the present invention, by applying 180 ° current at the time of startup, torque ripple during open loop operation immediately after startup is reduced, and the chance of stopping due to overcurrent protection of the inverter or stopping due to stall is reduced. Can be.
Further, as the rotational speed increases, the torque ripple also decreases. Therefore, the reliability of the start-up control can be ensured by returning to 120 ° energization immediately before switching to the closed loop control.

[0013] The invention according to claim 4 is the invention according to claims 1 to 3.
A brushless DC having a Y (star) connected armature winding in the control device for a brushless DC motor according to any one of the above.
A first magnetic pole position detecting means for detecting a magnetic pole position by detecting an induced voltage from an input terminal of the Y (star) connected armature winding in a non-energized section;
(Star) neutral point of the connection armature winding and the Y (star)
Second magnetic pole position detecting means for detecting a magnetic pole position by detecting a potential difference fluctuation between a neutral point of a Y (star) connected resistive element connected in parallel to an input terminal of the connected armature winding; It is characterized in that either one of the first magnetic pole position detecting means or the second magnetic pole position detecting means is selected and the rotation speed is controlled in accordance with the magnitude of the conduction angle or the magnitude of the rotation speed.

According to the present invention, two types of magnetic pole position detecting means are provided, and the detecting means is selected according to the energizing angle. Therefore, the magnetic pole position can be reliably determined at any energizing angle between 120 ° and 180 °. Detection can be performed, and an optimum conduction angle with respect to the operation region can be selected.

[0015] The invention according to claim 5 is the invention according to claims 1 to 3.
A brushless DC having a Y (star) connected armature winding in the control device for a brushless DC motor according to any one of the above.
A first magnetic pole position detecting means for detecting a magnetic pole position by detecting an induced voltage from an input terminal of the Y (star) connected armature winding in a non-energized section;
The (star) connection armature winding is connected in parallel to a voltage dividing point divided by a resistance element connected between windings of a predetermined phase and an input terminal of the Y (star) connection armature winding. Y
And (2) second magnetic pole position detecting means for detecting a magnetic pole position by detecting a potential difference fluctuation between a voltage dividing point of the predetermined phase of the resistance element of the (star) connection resistance element and the intermediate tap. The method is characterized in that either the first magnetic pole position detecting means or the second magnetic pole position detecting means is selected in accordance with the magnitude of the energization angle or the magnitude of the rotation speed to perform closed loop control of the rotation speed.

According to the present invention, two types of magnetic pole position detecting means are provided, and the detecting means is selected according to the energizing angle, so that the magnetic pole position can be reliably determined at any energizing angle between 120 ° and 180 °. Detection can be performed, and an optimum conduction angle with respect to the operation region can be selected.

The invention according to claim 6 is the invention according to claims 1 to 3
A brushless DC having a Y (star) connected armature winding in the control device for a brushless DC motor according to any one of the above.
A first magnetic pole position detecting means for detecting a magnetic pole position by detecting an induced voltage from an input terminal of the Y (star) connected armature winding in a non-energized section;
The (Star) connection armature winding is connected in parallel to the voltage dividing point between the neutral point of the resistance element between the neutral point and the DC-side negative potential and the input terminal of the Y (star) connection armature winding. Y
A second magnetic pole for detecting a magnetic pole position by detecting a potential difference change between a neutral point of the resistive element between the neutral point of the (star) connected resistive element and the DC side negative potential. Position detecting means, wherein the first magnetic pole position detecting means or the second magnetic pole position detecting means
And the closed loop control of the rotational speed is performed by selecting one of the magnetic pole position detecting means.

According to the present invention, two types of magnetic pole position detecting means are provided, and the detecting means is selected according to the energizing angle. Therefore, the magnetic pole position can be reliably determined at any energizing angle between 120 ° and 180 °. Detection can be performed, and an optimum conduction angle with respect to the operation region can be selected.

The invention according to claim 7 is the invention according to claims 1 to 6
In the control device for a brushless DC motor according to any one of the above, when the energization angle is around 120 °, the magnetic pole position is detected by the first magnetic pole position detection means, and the energization angle is larger than 120 °, When it is difficult to detect the magnetic pole position by the magnetic pole position detecting means, the magnetic pole position is detected by the second magnetic pole position detecting means.

According to the present invention, the magnetic pole position is detected by the first magnetic pole position detecting means when the energizing angle is around 120 °, and the magnetic pole position is detected by the second magnetic pole position detecting means when the energizing angle is larger than 120 °. By doing so, it is possible to reliably detect the magnetic pole position irrespective of the conduction angle.

[0021] The invention according to claim 8 is the invention according to claims 1 to 6.
In the control device for a brushless DC motor according to any one of the above, in a low rotation speed region, the first magnetic pole position detection means detects a magnetic pole position, performs a closed loop operation at a conduction angle of 120 °, and in a middle and high speed rotation speed region. The magnetic pole position is detected by the second magnetic pole position detecting means,
The closed loop operation is performed at a conduction angle of 80 ° or less.

According to the present invention, when the rotation speed is low, the first magnetic pole position detecting means detects the magnetic pole position and
By operating with 20 ° energization, if the rotation speed is at or above medium speed, the magnetic pole position is detected by the second magnetic pole position detection means, and the motor is operated with an energization angle of 120 ° or more and 180 ° or less. Regardless of the above, the magnetic pole position can be detected reliably.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, three embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a brushless DC motor according to a first embodiment of the present invention. In this figure, reference numeral 1 denotes an AC power supply, which is converted into DC power by a converter unit 2 and then smoothed by a smoothing capacitor 3. The smoothed DC power is inversely converted into AC power in the inverter unit 4 under the control of the inverter control circuit 9 to drive the motor 5.

The first magnetic pole position detecting circuit 7 detects a magnetic pole from a signal having a frequency three times the electric rotational speed obtained by comparing the induced voltages of the respective phases generated during the non-energization period of the input terminal voltage of the motor 5 with each other. The position is detected and a control command is given to the microcomputer 90 of the inverter control circuit 9. The first magnetic pole position detecting circuit 7 is configured such that the inverter unit 4 is energized by 120 °
It is used when the current is around 0 ° to 140 ° and the non-current period is 60 ° or around 60 ° to 40 °. FIG. 2 shows a basic circuit example of the first magnetic pole position detection circuit 7. In this figure, the input voltage of each phase is represented by operational amplifiers 71 to 73.
And the respective outputs are passed to the microcomputer 90 of the inverter control circuit 9.

The second magnetic pole position detecting circuit 8 includes a neutral point 50 for the Y (star) connected armature winding and a neutral point 50 for the Y (star).
Neutral point 6 of resistance neutral point circuit 6 using a Y (star) connected resistance element connected in parallel with the input terminal of the connection armature winding
The magnetic pole position is detected based on the potential difference fluctuation between 0 and 0, and a control command is given to the microcomputer 90 of the inverter control circuit 9. The second magnetic pole position detection circuit 8 is used when the energization angle applied to the armature winding of the motor 5 is larger than 120 °. FIG. 3 shows an example of a principle circuit of the second magnetic pole position detection circuit 8. In this figure, the input signals of the neutral point and the neutral point of the resistance of the Y (star) -connected armature winding are represented by an operational amplifier 80, a low-pass filter 81 and an operational amplifier 8.
The output is passed to the microcomputer 90 of the inverter control circuit 9.

As described above, the first magnetic pole position detecting circuit 7
And the second magnetic pole position detection circuit 8, the magnetic pole position can be detected accurately even when the energization angle is changed from 120 ° to 180 °, and the output is effectively extracted from the motor 5. be able to. FIG. 4 shows 120 °
It is a figure showing an example of a waveform at the time of energization.

Next, a method of controlling the conduction angle of the brushless DC motor having the configuration of FIG. 1 will be described with reference to the example of the rotation speed and the conduction angle shown in FIG. In FIG. 5, at the time of startup and in the low-speed rotation region up to the rotation speed N1, the operation is performed at a conduction angle of 120 °. In the high-speed rotation region where the rotation speed is equal to or higher than the rotation speed N2, the operation is performed at the conduction angle of 180 °. Further, in the medium speed rotation region A from the rotation speeds N1 to N2, the operation is performed with the conduction angle between 120 ° and 180 ° as shown by the dotted line.

The above-mentioned medium speed rotation region A will be described with reference to FIG. FIG. 6 is a table in which the energization angle with respect to the rotation speed is tabulated. In the low-speed rotation region up to the rotation speed N1, the motor is used at 120 ° conduction, and in the high-speed rotation region above the rotation speed N2, it is used at 180 ° conduction. Is shown.
Further, in the rotation speed between N1 and N2, the rotation speed k
The conduction angle α at (rps) is

(Equation 1)

Further, inverter DC voltage V _DC, the modulation rate A _f of the PWM waveform, may be corrected energization angle α with the motor current I _M.

(Equation 2)

Next, the operation when the energizing angle at the time of starting is 180 ° will be described with reference to FIGS.
In FIG. 7, during open-loop operation at the time of startup, 180 ° conduction is performed until the rotation speed NC is about to be completed, and the conduction angle is reduced to 120 ° from this NC to the start completion rotation speed NO to detect the magnetic pole position. Transition to closed loop operation by circuit. For rotation speeds from N1 to N2 or more, the motor is operated at the same conduction angle as that shown in FIG.

FIG. 8 is a diagram showing the rotation speed and the motor generated torque from the start to the transition to the closed loop operation.
FIG. 8A shows the characteristics when activated by 120 ° conduction, and FIG. 8B shows the characteristics when activated by 180 ° conduction. That is, from the start to the rotation speed NC immediately before the start is completed, the torque ripple is smaller in the case of the 180 ° conduction shown in FIG. 8B, and the difference between the two after the rotation speed NC is not remarkable. By starting by 180 ° energization in FIG. 8B, torque ripple is reduced, and the chance of stopping due to overcurrent protection of the inverter or stopping due to stall is reduced.

Next, the brushless DC according to the second embodiment, which is a modification of the first embodiment described above, is described.
FIG. 9 is a block diagram showing the configuration of the motor. This embodiment differs from the first embodiment in FIG. 1 in that the input signal detection point of the second magnetic pole position detection circuit 8 is not a motor neutral point and a resistance neutral point, but a U-phase motor. An intermediate tap having a predetermined voltage division ratio of a resistor 53 connected in parallel with the slave winding 51U;
This is a point taken from an intermediate tap having a predetermined voltage division ratio of the resistor 61U of the resistor neutral point circuit corresponding thereto. With this connection, a desired signal for magnetic pole position detection can be obtained.

FIG. 10 is a block diagram showing a configuration of a brushless DC motor according to a third embodiment, which is a modification of the first embodiment. This embodiment differs from the first embodiment in FIG. 1 in that the input signal detection point of the second magnetic pole position detection circuit 8 is not the neutral point of the motor neutral point and the neutral point of the resistance neutral point circuit. , A point taken from an intermediate tap having a predetermined voltage dividing ratio of the resistors 54 and 64 provided between the respective neutral points and the negative side of the DC circuit. With this connection, a desired signal for magnetic pole position detection can be obtained.

The three embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and is not limited to the scope of the present invention. Even a design change or the like is included in the present invention.
FIG. 13 shows an example of the rotation speed of the motor, the magnetic pole position detecting means, and the conduction angle according to the above description.

[0035]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, the setting of the energization angle is performed in the rotation region, the magnitude of the motor current, the inverter DC voltage,
The motor loss can be reduced by selecting and operating the optimum pattern for the operating condition from the operating patterns provided for each of the PWM waveform modulation rate and the motor load torque value. Efficiency is improved.

According to the second aspect of the present invention, the energization angle is made variable in the rotation region and the energization angle of the inverter is made 120 ° in the low-speed rotation region, so that the distortion of the motor current waveform is small and the harmonic components are reduced. And the motor efficiency is improved. In the high-speed rotation region, 120 °
By setting the above wide-angle conduction angle (for example, 180 °), it is possible to effectively use the inverter input voltage,
Since the voltage applied to the motor can be increased as compared with the case of 120 ° conduction, the maximum rotation speed can be increased. Further, in the medium speed rotation region, even under the same load condition, the distortion of the motor current waveform can be reduced by the combination of the conduction angle and the modulation factor of the PWM waveform, the motor loss is reduced, and the motor efficiency is improved.

According to the third aspect of the present invention, 180
By performing the energization, torque ripple at the time of open loop operation immediately after startup is reduced, and the chance of stopping due to overcurrent protection of the inverter or stopping due to stall can be reduced. Also, as the rotational speed increases, the torque ripple also decreases.
By returning the current to 0 °, the reliability of the start control can be ensured.

According to the fourth to sixth aspects of the present invention, two types of magnetic pole position detecting means are provided, and the detecting means is selected according to the energizing angle. Therefore, at any energizing angle between 120 ° and 180 °. It is possible to reliably detect the magnetic pole position, and it is possible to select an optimal energization angle with respect to the operating region.

According to the seventh aspect of the present invention, the conduction angle is 120
In the vicinity of °, the magnetic pole position is detected by the first magnetic pole position detecting means, and the magnetic pole position is detected by the second magnetic pole position detecting means at a conduction angle larger than 120 °,
Regardless of the conduction angle, the magnetic pole position can be detected reliably.

According to the invention of claim 8, in the low rotation speed region, the first magnetic pole position detection means detects the magnetic pole position, and performs the closed loop operation at the 120 ° conduction angle. By detecting the magnetic pole position by the magnetic pole position detecting means 2 and performing the closed loop operation at a conduction angle of 120 ° or more and 180 ° or less, regardless of the rotation speed,
The detection of the magnetic pole position can be performed reliably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a brushless DC motor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a specific example of a first magnetic pole position detection circuit 7.

FIG. 3 is a diagram showing a specific example of a second magnetic pole position detection circuit 8;

FIG. 4 is a diagram showing an example of a waveform in the case of 120 ° conduction.

FIG. 5 is a diagram illustrating an example of a rotation speed and a conduction angle.

FIG. 6 is a diagram in which a conduction angle with respect to a rotation speed is tabulated.

FIG. 7 is a diagram showing an example of a rotation speed and an energization angle when the energization angle at the time of starting is 180 °.

FIG. 8 is a diagram showing a rotation speed and a motor-generated torque from a start to a transition to a closed-loop operation, and FIG.
FIG. 8 is a diagram showing characteristics when the motor is started by energizing by 20 °, FIG.
(B) is a diagram in the case of starting by 180 ° energization.

FIG. 9 is a block diagram showing a configuration of a brushless DC motor according to a second embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a brushless DC motor according to a third embodiment of the present invention.

FIG. 11 is a block diagram showing one configuration of a brushless DC motor for driving a compressor according to a conventional technique.

FIG. 12 is a block diagram showing another configuration of a brushless DC motor for driving a compressor according to a conventional technique.

FIG. 13 is a diagram illustrating an example of a rotation speed, a magnetic pole position detection unit, and a conduction angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Converter part 3 ... Smoothing capacitor 4 ... Inverter part 5 ... Motor 51U, 51V, 51W ... Armature winding 52 ... Rotor (rotor) 53 ... Resistance 54 ... Resistance 6 ... Resistance neutral point circuit 61U , 61V, 61W ... resistor 64 ... resistor 7 ... first magnetic pole position detection circuit 8 ... second magnetic pole position detection circuit 9 ... inverter control circuit 90 ... microcomputer 91 ... base drive circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H560 AA02 BB04 BB07 BB12 DA13 DA16 EB01 EC09 EC10 RR05 SS07 TT07 TT08 TT15 UA02 XA12

Claims (8)

[Claims] 1. A control device for a brushless DC motor, comprising: a rotation speed, a magnitude of a motor current, an inverter DC voltage,
An operation pattern table in which a plurality of operation patterns are tabulated for each of the modulation rate of the WM waveform and the torque value of the motor load is provided, and an optimum operation pattern for each operation condition is selected from the operation pattern table. A control device for a brushless DC motor, wherein the control device is operated by a motor. 2. An operation pattern is selected from the operation pattern table by selecting an operation pattern having a conduction angle of 120 ° and starting in an open-loop operation, and selecting an operation pattern having a conduction angle of 120 ° in a low-speed rotation region. In the high-speed rotation region, a closed-loop operation is performed by detecting the magnetic pole position by selecting an operation pattern having a wide-angle conduction angle of 120 ° or more. In the medium-speed rotation region, the conduction angle and PWM ( 2. A closed loop operation by detecting a magnetic pole position by selecting an operation pattern for controlling a conduction angle so as to reduce a motor current waveform distortion based on a combination of a modulation rate of a pulse width modulation waveform. Control device for brushless DC motor. 3. An operation pattern having a conduction angle of 180 ° is selected to start the operation in the open-loop operation instead of the activation of the open-loop operation by the conduction angle of 120 °. The control device for a brushless DC motor according to claim 1 or 2, wherein the operation is performed after returning to the corner operation pattern. 4. A control device for a brushless DC motor having a Y (star) connected armature winding, wherein an induced voltage is detected from an input terminal of the Y (star) connected armature winding in a non-energized section. First magnetic pole position detecting means for detecting a magnetic pole position; a neutral point of the Y (star) connected armature winding; and a Y connected in parallel to an input terminal of the Y (star) connected armature winding.
A second magnetic pole position detecting means for detecting a magnetic pole position by detecting a potential difference between the neutral point of the (star) connected resistive element and a magnetic pole position in accordance with the magnitude of the conduction angle or the magnitude of the rotational speed; 4. The brushless DC motor according to claim 1, wherein one of the first magnetic pole position detecting means and the second magnetic pole position detecting means is selected to perform closed loop control of a rotation speed. 5. Control device. 5. A control device for a brushless DC motor having a Y (star) connected armature winding, comprising detecting an induced voltage from an input terminal of the Y (star) connected armature winding in a non-energized section. A first magnetic pole position detecting means for detecting a magnetic pole position; a voltage dividing point divided by a resistance element connected between windings of a predetermined phase among the Y (star) connected armature windings; (Star) Connection A potential difference between the Y (star) connected resistive element connected in parallel to the input terminal of the armature winding and a voltage dividing point at the intermediate tap of the resistive element of the predetermined phase is detected. And a second magnetic pole position detecting means for detecting a magnetic pole position by using the first magnetic pole position detecting means or the second magnetic pole position detecting means in accordance with the magnitude of a conduction angle or the number of rotations. Select for closed-loop control of rotational speed. 4. The control device for a brushless DC motor according to claim 1, wherein the control is performed. 6. A control device for a brushless DC motor having a Y (star) connected armature winding, comprising detecting an induced voltage from an input terminal of the Y (star) connected armature winding in a non-energized section. A first magnetic pole position detecting means for detecting a magnetic pole position; a voltage dividing point between a neutral point of the Y (star) connected armature winding and a DC-side negative potential by an intermediate tap of a resistance element;
(Star) connection A voltage dividing point by an intermediate tap of the resistance element between the neutral point of the resistance element of the Y (star) connection connected in parallel to the input terminal of the armature winding and the DC negative potential, And a second magnetic pole position detecting means for detecting a magnetic pole position by detecting a change in potential difference between the first magnetic pole position detecting means and the second magnetic pole position detecting means according to the magnitude of the conduction angle or the magnitude of the rotation speed. 4. The brushless DC motor control device according to claim 1, wherein one of the magnetic pole position detecting means is selected to perform closed loop control of the rotation speed. 7. The magnetic pole position is detected by the first magnetic pole position detecting means when the energizing angle is around 120 °, and the energizing angle is larger than 120 ° and the magnetic pole position is detected by the first magnetic pole position detecting means. The brushless D according to any one of claims 1 to 6, wherein when it is difficult to detect the magnetic pole position, the second magnetic pole position detecting means detects the magnetic pole position.
Control device for C motor. 8. In a low rotation speed range, the first magnetic pole position detection means detects a magnetic pole position, and performs a closed loop operation at a 120 ° conduction angle. In a middle and high speed rotation speed range, the second magnetic pole position detection is performed. 7. The control device for a brushless DC motor according to claim 1, wherein the closed-loop operation is performed at a conduction angle of 120 ° or more and 180 ° or less by detecting a magnetic pole position by the means.