JPH02197291A - Method and device for starting brushless motor - Google Patents

Abstract

PURPOSE:To start a brushless motor smoothly by increasing at least one of the frequency and the duty ratio of rotary magnetic field along a curve having differential coefficient decreasing with time while increasing the other with time along a line having predetermined inclination, thereby suppressing starting current and vibration of the motor. CONSTITUTION:A synchronous signal 100 is outputted such that the frequency thereof increases with time along a line having predetermined inclination simultaneously with rising of a start command signal 151. A duty ratio command signal 153 is outputted such that the duty ratio increases along a line having predetermined inclination simultaneously with rising of the start command signal 151. When the frequency and the duty ratio of the synchronous signal 100 reach to such values as maintaining stable rotation of a brushless motor 3, they are stopped from increasing and maintained at constant values.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a brushless motor, and in particular detects the relative position between a magnet rotor and an armature winding by an induced voltage induced in the armature winding, and starts the motor. The present invention relates to a method and device for starting a brushless motor for stable rotation.

BACKGROUND OF THE INVENTION Normally, a brushless motor requires a detector to detect the magnetic pole position of its rotor. For example, when this brushless motor is used in an air conditioner compressor, the These detectors cannot be used because the reliability of the detectors cannot be guaranteed. Therefore, in such applications, a method is used in which a voltage signal induced in the armature winding is detected without using a magnetic pole position detector, and a motor commutation signal is generated based on the detected voltage signal.

However, the voltage signal is pulsed to the armature winding only when the rotor is rotating, and when the rotor is stopped, magnetic pole position information cannot be obtained. In other words, this voltage signal cannot be used during startup. Therefore, at startup, a specific signal that generates a rotating magnetic field in the armature winding is applied to force the rotor to rotate regardless of the magnetic pole position of the rotor.

+7 However, since this particular signal is given while ignoring the magnetic pole position of the far rotor, a large starting current will flow at the time of starting. If this starting current exceeds the permissible current value of the group of semiconductor switching elements that conduct and cut off current to the armature windings, startup is impossible.

In order to solve this problem, a method has been invented in which the voltage of the DC power supply that supplies current to the motor is lowered only during startup, thereby reducing the starting current (for example, Japanese Patent Application Laid-Open No. 135385/1985). .

Problems to be Solved by the Invention However, in the case of large brushless motors, such as those used to drive the compressor of air conditioners, the power supply capacity is only a few kVA.
Therefore, in such applications, so-called pulse width modulation is usually used in which the power supply voltage is kept constant and the voltage is controlled by controlling the duty ratio of the voltage signal pulse. This is to avoid an increase in the size and cost of the device due to the configuration of a variable voltage power source.

Therefore, there is a problem in that the startup method shown in the conventional example cannot be used in the application of large equipment as described above.

In view of the above-mentioned conventional problems, the present invention provides a starting method and a starting device for a brushless motor, which suppress starting current and vibration at the time of starting the motor and enable smooth starting even when voltage is controlled by pulse width modulation. It is something.

Means for Solving the Problems In order to solve the above problems, the present invention provides a means for controlling the frequency of the rotating magnetic field generated in the armature winding of the brushless motor and the duty ratio as a control means for the voltage applied to the motor for a certain period of time after the motor is started. is simultaneously increased along a straight line with a constant slope over time, and after a certain period of time has elapsed, the brushless motor is driven based on a signal obtained by converting a voltage signal induced in the armature winding. It is something.

Further, at least one of the frequency and duty ratio of the rotating magnetic field is increased along a curve whose differential coefficient decreases over time, and the other is increased along a straight line with a constant slope over time.

Furthermore, at least one of the frequency and duty ratio of the rotating magnetic field is increased along a plurality of straight lines whose slope decreases over time, and the other is increased along a curve whose differential coefficient decreases over time, or along a straight line with a constant slope. It has an increasing configuration.

Further, a brushless motor having a three-phase armature winding connected to a neutral point ungrounded, a DC power supply, a group of semiconductor switching elements for supplying or interrupting current to the armature winding, and a magnet rotor. , a starting command means, a synchronizing signal generating means for outputting a synchronizing signal in response to a command from the starting command means, and a rotating magnetic field for generating a rotating magnetic field in the armature winding using the signal output from the synchronizing signal generating means. a generating means, a position detecting means for detecting the relative position of the armature winding and the magnet rotor based on a voltage signal induced in the armature winding, and an output signal of the rotating magnetic field generating means and the position detecting means. a switching means for selecting, switching and outputting an output signal of the means; a switching command means for giving a switching command to the switching means; and a drive signal for generating a drive signal for the switching element group using the output signal of the switching means. generating means, duty ratio commanding means, and pulse width modulation means for applying pulse width modulation to the output signal of the drive signal generating means based on the command of the duty ratio commanding means, the pulse width modulation means being constant after generation of the command of the start commanding means. The frequency of the output signal of the synchronizing signal generating means and the duty ratio are simultaneously increased along a straight line with a constant slope over time, the magnet rotor is started to rotate, and after a certain period of time, the switching is performed. The motor is configured to drive the motor based on the output signal of the position detection means by switching the means.

Further, at least one of the frequency of the output signal of the synchronizing signal generating means and the duty ratio is increased along a curve whose differential coefficient decreases over time, and the other is increased along a straight line with a constant slope over time. We are prepared.

Furthermore, at least one of the frequency and duty ratio of the output signal of the synchronizing signal generating means is increased along a plurality of straight lines whose slope decreases with time, and the other is a curve whose differential coefficient decreases with time, or a constant It has a configuration in which the slope increases along a straight line.

Effect: With the above-described configuration, the present invention appropriately increases the frequency and duty ratio of the rotating magnetic field generated in the armature winding over time, thereby suppressing the starting current and vibration when starting the motor, and realizing smooth starting. I will do it.

EXAMPLE Hereinafter, a first example of the present invention will be described with reference to the drawings.

FIG. 4 is a block diagram of a brushless motor starter according to the first embodiment of the present invention. In Figure 4, 1
is a DC power supply, 2 is a group of semiconductor switching elements, Q1~
It consists of six transistors Q6 and six diodes connected in antiparallel to each transistor. Reference numeral 3 designates a brushless motor, which includes an armature winding 4 and a magnet rotor 5 connected in three phases. 6 is a position detection means, 7 is a switching means, 8 is a drive signal generation means, 9 is a pulse width modulation means, 10 is a synchronization signal generation means, 11 is a rotating magnetic field generation means, 12 is a start command means, 13
14 is a switching command means, and 14 is a duty ratio command means.

With the above configuration, at startup, the output signal of the rotating magnetic field generating means 11 is transmitted to the drive signal generating means 8 by the switching means 7, and the output signal is pulse width modulated to drive the transistors of the semiconductor switching element group 2. Start the brushless motor 3. When the brushless motor 3 starts rotating, the position detection means 6 detects the magnetic pole position of the magnet rotor 5 from the induced voltage generated in the armature winding 4, and the signal is sent to the drive signal generation means 8 by the switching means 7. The brushless motor 3 is controlled by applying pulse width modulation to the signal to drive the transistors of the semiconductor switching element group 2.

FIG. 5 shows a more concrete configuration of the block diagram in FIG. 4, and the same reference numerals are given to the same parts or parts that have the same function as those in FIG. 4.

In the figure, 1 to 5 are exactly the same as in FIG. 4. Reference numeral 6 denotes a position detection circuit, which includes three filters 61 to 63 and a comparator group 64. 7 is a switching circuit, 8 is a drive signal generation circuit, 9 is a pulse width modulation circuit, 1° is a synchronization signal generation circuit, 11 is a rotating magnetic field generation circuit, 15 is a microcomputer, and the activation command means 12 and switching shown in FIG. command means 13;
Corresponding to the duty ratio command means 14, it sends a start command signal 151 to the synchronization signal generation circuit 10 and a switching signal 1 to the switching circuit 7.
52 and the duty ratio command signal 1 to the pulse width modulation circuit 9.
53 are output respectively.

The operation of the embodiment of the brushless motor starting device configured as described above will be described.

First, a start command signal 15 is sent from the microcomputer 15.
1. The switching signal 152 and the duty ratio command signal 153 are output simultaneously. The synchronization signal generation circuit 10 that receives the activation command signal 151 outputs a synchronization signal 100 as shown in FIG. Based on this synchronization signal 100, the rotating magnetic field generating circuit 11 outputs signals 111 to 113 shown in FIG. The switching circuit 7 receives input signals 87 to 8 of the drive signal generation circuit 8.
9 is a circuit that switches between using the output signal of the position detection circuit 6 and the output signal of the rotating magnetic field generating circuit 11. At startup, the switching signal 152 causes the rotating magnetic field generating circuit 11 to be output.
has been switched to the output signal side. The output signals 111 to 113 of the rotating magnetic field generation circuit 11 are taken into the drive signal generation circuit 8, which outputs output signals 81 to 86 shown in FIG. 6. Of these output signals, 81 to 8
3 is further input to the pulse width modulation circuit 9, where pulse width modulation is performed based on the duty ratio command signal 153, and each becomes a drive signal for the transistors Q1 to Q3 of the semiconductor switching element group 2.

The output signals 84 to 86 of the blade drive signal generation circuit 8 are directly transmitted to the transistors Q4 to Q of the semiconductor switching element group 2.
6 drive signal. These drive signals switch the six transistors of the semiconductor switching element group 2, and as a result, a rotating magnetic field is generated in the armature winding 4, the magnet rotor 5 rotates, and the brushless motor 3 is started. .

Here, as shown in FIG. 1, the synchronizing signal 100 is outputted at the same time as the startup command signal 151 rises so that its frequency increases along a straight line with a constant slope over time. Further, as shown in FIG. 1, the duty ratio command signal 153 is also outputted at the same time as the starting command signal 151 rises so that the duty ratio increases along a straight line with a constant slope over time. When the frequency and duty ratio of the synchronization signal 100 reach a value that allows stable rotation of the brushless motor 3 to be maintained, these increases are stopped and the constant values are maintained.

After the brushless motor 3 is started and after a period of time to which the brushless motor 3 can maintain sufficiently stable rotation, the microcomputer 15 outputs a switching signal 152 and switches the switching circuit 7 to the position detection circuit 6.
Switch to the side. As a result, the input signals 87 to 89 of the drive signal generation circuit 8 are replaced by the output signals 641 to 641 of the position detection circuit 6.
643, and thereafter the brushless motor 3 is driven by the induced voltage signals 410 to 430 generated in the armature winding 4. Following the fall of the switching signal 152, the start command signal 151 is canceled and the series of start operation procedures is reset to the initial state.

Note that the duty ratio command signal 153 is generated at time t.

After that, the microcomputer 15 outputs the applied voltage control command for controlling the speed of the brushless motor 3.

The above operation suppresses the starting current and vibration at the time of starting the motor, and enables smooth starting even when voltage is controlled by pulse width modulation.

Next, a second embodiment of the present invention will be described with reference to FIG.

The configuration of the device is the same as that of the first embodiment, so a description thereof will be omitted.

In the first embodiment, the synchronization signal 100 and the duty ratio command signal 153 are changed so that the frequency and duty ratio of the synchronization signal 100 follow a curve whose differential coefficient decreases with time, as shown in FIG. Change it so that it increases along. Operations other than these are similar to those in the first embodiment.

The above operation suppresses the starting current and vibrations when starting the motor even when voltage is controlled by pulse width modulation, enabling smoother starting.

Furthermore, by increasing the frequency and duty ratio of the starting signal 100 over time along the curve shown in FIG. 2, the starting time can be shortened, and the duration of the large current and vibration associated with starting can be shortened. Can be done.

Next, a third embodiment of the present invention will be described with reference to FIG.

The configuration of the device is the same as that of the first embodiment, so a description thereof will be omitted.

In the first embodiment, the synchronization signal 100 and the duty ratio command signal 153 are changed by three straight lines in which the frequency and duty ratio of the synchronization signal 100 decrease over time, as shown in FIG. Change it so that it increases along. Operations other than these are similar to those in the first embodiment.

The above operation suppresses the starting current and vibrations when starting the motor even when voltage is controlled by pulse width modulation, enabling smoother starting.

Furthermore, by increasing the frequency and duty ratio of the synchronization signal 100 over time along three straight lines as shown in Figure 3, the startup time can be shortened, and the duration of the large current and vibration associated with startup can be shortened. can do. Furthermore, by linearizing the changes in the synchronization signal 1000 frequency and duty ratio, the generation of those change patterns can be performed using a simple proportional equation, and the synchronization signal 100 and duty ratio command signal 153 can be easily generated.

In addition, in the first to third embodiments, the synchronization signal generator circuit 1
0 and the rotating magnetic field generating circuit 11 are each provided as independent circuits, but the microcomputer 15 may perform part or all of these circuit functions.

Effects of the Invention As described above, the present invention comprises a three-phase armature winding connected to an ungrounded neutral point, a DC power supply, and a group of semiconductor switching elements for supplying and interrupting current to the armature winding. , a brushless motor having a magnetic rotor, a start command means, a synchronization signal generation means for outputting a synchronization signal in response to a command from the start command means, and a signal output from the synchronization signal generation means to generate the armature winding. a rotating magnetic field generating means for generating a rotating magnetic field, a position detecting means for detecting the relative position of the armature winding and the magnet rotor based on a voltage signal induced in the armature winding, and the rotating magnetic field generating means. switching means for selecting, switching and outputting the output signal of the means and the output signal of the position detection means; switching command means for giving a switching command to the switching means; and switching means for controlling the switching element group using the output signal of the switching means. a drive signal image generation means for generating a drive signal; a duty ratio command means; and a pulse width modulation means for applying pulse width modulation to the output signal of the drive signal generation means based on a command from the duty ratio command means;
By simultaneously increasing the frequency of the output signal of the synchronizing signal generating means and the duty ratio along a straight line with a constant slope over time, it is possible to reduce the starting current and vibration when starting the motor even when voltage control is performed by pulse width modulation. suppress,
This enables smooth startup.

Further, at least one of the frequency of the output signal of the synchronizing signal generating means and the duty ratio is increased along a curve whose differential coefficient decreases over time, and the other is increased along a straight line with a constant slope over time. As a result, the startup time can be shortened, and the duration of the large current and vibration associated with startup can be shortened.

Furthermore, the frequency of the output signal of the synchronization signal generating means,
At least one of the duty ratios is increased along a plurality of straight lines whose slope decreases with time, and the other is increased along a curve whose differential coefficient decreases with time, or a straight line with a constant slope, thereby increasing the startup time. It is possible to shorten the duration of the large current and vibration associated with startup, and it is also possible to easily generate a startup pattern.

[Brief explanation of the drawing]

1 to 3 are diagrams showing how the synchronizing signal frequency and duty ratio of the brushless motor starter in the first to third embodiments of the present invention are increased over time, respectively, and FIG. 5 is a block diagram of a brushless motor starting device in the third embodiment, FIG. 5 is a block diagram of the same brushless smoke starting device, and FIG. 6 is a waveform diagram of each part in the configuration of FIG. 5. 1... DC power supply, 2... Semiconductor switching element group, 3... Brushless motor, 4...
... Armature winding, 5 ... Magnet rotor, 6
...Position detection means, 7...Switching means,
8... Drive signal generation means, 9... Pulse width modulation means, 10... Synchronization signal generation means, 1
DESCRIPTION OF SYMBOLS 1... Rotating magnetic field generating means, 12... Starting command means, 13... Switching command means, 14...
... Duty ratio command means, 15 ... Microcomputer, 100 ... Synchronization signal, 15
1...Start command signal, 152...Switching signal, 153...Duty ratio command signal.

Claims (6)

[Claims] (1) Detecting a voltage signal induced in the armature winding of a brushless motor having a magnetic rotor, and generating a commutation signal for the brushless motor using the signal obtained by converting this voltage signal, In a brushless motor that does not include a magnetic pole position detector, for a certain period of time after the motor is started, the frequency of the rotating magnetic field generated in the armature winding of the brushless motor and the duty ratio as a control means for the motor applied voltage are simultaneously adjusted to a constant value over time. A method for starting a brushless motor, in which the voltage is increased along a straight line of inclination, and after a certain period of time has elapsed, the brushless motor is driven based on a signal obtained by converting the voltage signal. (2) At least one of the frequency and duty ratio of the rotating magnetic field is increased along a curve whose differential coefficient decreases over time, and the other is increased along a straight line with a constant slope over time. How to start a brushless motor. (3) At least one of the frequency and duty ratio of the rotating magnetic field is increased along a plurality of straight lines whose slope decreases over time, and the other is set along a curve whose differential coefficient decreases over time, or along a straight line with a constant slope. The method for starting a brushless motor according to claim 1, wherein the brushless motor is increased. (4) A brushless motor having a three-phase armature winding connected to an ungrounded neutral point, a DC power supply, a group of semiconductor switching elements for supplying or interrupting current to the armature winding, and a magnet rotor. a starting command means; a synchronizing signal generating means for outputting a synchronizing signal in response to a command from the starting command means; and a rotating magnetic field for generating a rotating magnetic field in the armature winding using the signal output from the synchronizing signal generating means. a generating means, a position detecting means for detecting the relative position of the armature winding and the magnet rotor based on a voltage signal induced in the armature winding, and an output signal of the rotating magnetic field generating means and the position detecting means. a switching means for selecting, switching and outputting an output signal of the means; and a switching command means for giving a switching command to the switching means;
a drive signal generation means for generating a drive signal for the switching element group using the output signal of the switching means; a duty ratio command means; and an output signal of the drive signal generation means;
Pulse width modulation means applies pulse width modulation based on a command from the duty ratio command means, and the frequency of the output signal of the synchronization signal generation means and the duty ratio are adjusted for a certain period of time after the command from the start command means is issued. At the same time, the magnetic rotor is increased along a straight line with a constant inclination over time to start rotating the magnet rotor, and after a certain period of time, the switching means is switched to drive the motor based on the output signal of the position detecting means. Motor starting device. (5) At least one of the frequency and duty ratio of the output signal of the synchronizing signal generating means is increased along a curve whose differential coefficient decreases over time, and the other is increased along a straight line with a constant slope over time. The brushless motor starting device according to item (4). (6) At least one of the frequency and duty ratio of the output signal of the synchronization signal generating means is increased along a plurality of straight lines whose slope decreases with time, and the other is a curve whose differential coefficient decreases with time, or is constant. The brushless motor starting device according to claim 4, wherein the inclination of the brushless motor increases along a straight line.