JPH01283090A - Driving method for 3-phase dc motor - Google Patents

Abstract

PURPOSE:To reduce power consumption by providing a common terminal at a common connection end of 3-phase windings. bipolarly driving it at the time of start, and unipolarly driving conducting it after it arrives at a predetermined speed. CONSTITUTION:A 3-phase current motor 1 has a 12-pole stator 2 and an 8-pole rotor 3, windings L1-L3 are wound on the stator 2, and coupled in a Y- connection. The rotor 3 is formed of a permanent magnet, and 3 Hall elements HU-HW are disposed at an internal of 60 degrees (120 degrees of electric al angle) mechanically at each 2 phases of the stator 2 directly thereunder. A control circuit of an analog switch 5 and a switch circuit of a transistor(Tr) is connected to each of the windings L1-L3 of the phases. Thus, the Tr 9 is turned OFF at the time of start, but turned ON by a switching signal when it arrives at a predetermined speed after starting, and one of the Trs 10-12 is selectively turned ON. As a result, a motor is switched from a bipolar drive to a unipolar drive.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a three-phase DC motor drive suitable for devices that need to start up to high-speed steady rotation in a short period of time, such as hard disk drives and optical disk drives. Regarding the method.

[Conventional technology]

Generally, the speed-torque characteristics of a DC brushless motor are as follows:
Ω is the rotational speed (rpm), 7 is the generated torque (g-am),
V is the supply voltage (V), K is the back electromotive force constant (V/rpm
), , where Kf is the torque constant (gcm/A) and Rs is the winding resistance (Ω).

Further, when k is a constant and Ia is a winding current, the following holds true.

When this type of three-phase DC motor is used, for example, as a spindle motor for an optical disk device, a relatively low supply voltage V is used, and the three-phase DC motor is driven with a constant winding current 1a. In this case, in order to miniaturize the device, it is required to drive the device with low power consumption and to reach a predetermined high-speed steady rotation speed in a short time.

- For boat fishing, a high rotation speed Ω can be obtained by increasing the supply voltage V and decreasing the generated torque T from equation (1), but specifically, the desired rotation speed can be obtained with a relatively low supply voltage V. Ω and generated torque T (1), (2)
A driving method is set based on the formula.

[Problem to be solved by the invention]

In the conventional method described above, in order to obtain a high rotational speed Ω with a given relatively low supply voltage V, the generated torque T must be reduced from equation (1).

Therefore, by reducing the winding current 1a and furthermore the torque constant by 7 from equation (2), the generated torque T can be reduced.

However, if the generated torque T is reduced in this way,
At startup, sufficient torque may not be obtained and the device may not drive smoothly.

On the other hand, in order to obtain sufficient torque at startup, the winding current I
Increasing a requires increasing the wire diameter of the winding to withstand the increased winding current. Increasing the wire diameter of the winding in this way increases the size of the three-phase DC motor itself in order to secure the necessary number of turns, which also leads to an increase in manufacturing costs.

The present invention was made in view of the current state of this type of three-phase DC motor as described above, and its purpose is to reduce power consumption, generate sufficient torque at startup, and generate high torque in a short time. The purpose of this invention is to propose a method for driving a three-phase DC motor that reaches a maximum rotational speed.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for driving a three-phase DC motor including a stator having three-phase windings and a rotor that rotates in accordance with switching of the excitation phase of the stator. A common terminal is provided at a common connection end of the three-phase windings, and when the three-phase DC motor is started, bipolar drive is performed in which the two-phase windings are energized, and the three-phase DC motor is set in advance. When the rotational speed is reached, the common terminal is used to energize the one-phase winding to perform unipolar drive.

[Effect]

In the present invention, a common terminal is provided at the common connection end of the three-phase windings of the stator.

First, at startup, no current is applied using this common terminal, and bipolar driving is performed. in this case,
If the winding resistance of each phase is r, then from equations (1) and (2), the rotational speed Ω and the generated torque T are given by the following equations, respectively.

T”KtIa・・・・・・・・・
(4) Next, when the number of rotations of the three-phase DC motor reaches a predetermined value, energization is performed using the common terminal. In this case, the number of turns of the winding to be energized becomes 1/2, so the torque constant? and the back electromotive force constant is 1/
2, and from equations (1) and (2), the rotational speed Ω' and the generated torque T' are given by the following equations, respectively.

Kt KtKt T””-Ktla ・・・・・・・・・
(6) As is clear from the comparison of equations (4) and (6) obtained in this way, the torque T generated at startup is twice that of unipolar drive, which is sufficient to ensure smooth startup. Achieves high steady rotation speed in a short time. Furthermore, as is clear from the comparison of equations (3) and (5), when the maximum rotational speed is reached and the generated torque is sufficiently small, the motor rotates at twice the rotational speed as in bipolar drive.

〔Example〕

Embodiments of the present invention are shown in FIGS. 1 to 3(a),
This will be explained in detail based on (b) and (c).

Here, FIG. 1 is a circuit diagram showing a control circuit of a three-phase DC motor according to an embodiment, FIG. 2 is an explanatory diagram showing a schematic configuration of a three-phase DC motor according to an embodiment, and FIG. (b),
(c) is an explanatory diagram showing the connection state of the windings and the flow of current, respectively.

As shown in Fig. 2, the three-phase DC motor 1 consists of a 12-piece stator 2 and an 8-piece rotor 3, and the stator 2 is wound with windings L+, Lx, and L3. )～(
As shown in c) Yifi! It is lined. The rotor 3 is made of a permanent magnet formed by alternately magnetizing S and N poles, and is rotatably arranged around the outer periphery of the stator 2. In the example, a three-phase DC motor 1 is energized at 120 degrees, and three Hall elements Hu are installed directly below the rotor 3 for each two phases of the stator 2 at an interval of 60 degrees mechanically, that is, 120 degrees in electrical angle. , Hv, and Hw are provided.

-m, when driving the three-phase DC motor, the outputs of the ball elements Hu, Hv, Hw are input to a drive circuit (not shown) and predetermined signal processing is performed, and the output terminals h1□, hv of the drive circuit are , h, to winding L1. A drive current is supplied to LZ and L3. This drive current causes the U terminal of the winding vAL1, the ■ terminal of the winding L2, and the W terminal of the winding to be in the logic value "0" state and 0PEN state at every phase angle of 360" (one round 'M). , the state of the logical value “1” of the signal, 0PE
Repeat N state. For this reason, between the U terminal and the
The excitation pole is switched every 60 degrees between the terminal and the W terminal, and between the terminal and the W terminal, and the rotor 3 is rotated by the field formed.

In the embodiment, as shown in FIG. 3(a), the windings L+, L! of each phase are connected to each other. , Ls are provided with a common terminal C, and as shown in FIG. 1, the output terminals hu, hv, h of the drive circuit and the winding Ll.

A control circuit consisting of an analog switch 5 and a transistor switch circuit is connected between the U terminal, ■ terminal, and W terminal of Lt and L3. That is, the output terminals hu, hv
, h, are connected to the bases of transistors 6, 7, and 8, respectively, via analog switch 5, and
．． 7.8 collectors have windings L+, Lt, respectively.
U terminal of L, s.

V3: N terminal, connected to W terminal.

Further, a common terminal C is connected to the emitter of a transistor 9, and a predetermined bias voltage VCC is applied to the collector of this transistor 9 and the emitters of the aforementioned transistors G and 7.8.
is applied. And the collectors of transistors 6, 7, and 8 become the collectors of transistors 10, 11, and 12, respectively! 2 connected, transistors 10, 11, 12
The emitter of is grounded.

In the control circuit shown in FIG. 1 having such a configuration, the transistor 9 is OFF when the three-phase DC motor is started, but after the start, the rotation speed of the three-phase DC motor reaches a predetermined rotation speed (for example, 1800 rpm). When this reaches the terminal t4, a detector (not shown) detects this and connects the base of the transistor 9 to the terminal t4.
A switching signal is input from the transistor 9, and the transistor 9 is turned on. Further, one of the transistors 6, 7, 8 is selected and turned on by the analog switch 5, and in synchronization with this, the terminal Ll+ j! + By inputting an ON signal to one of i3, transistor 1
One of 0, 11, and 12 is selected and turned ON.

At startup, when transistor 6 and transistor 11 are turned on, transistor 9 is turned off, so winding L
A winding current flows through + and Lt to form an excitation pole. Similarly, when transistor 6 and transistor 12 are turned on, an excitation pole is formed by windings Lt and L3, and when transistor 7 and transistor 12 are turned on, windings Lt and L3 are formed.
An excitation pole is formed at i. Moreover, when transistor 7 and transistor 10 are turned on, due to the winding, L,
When transistor 8 and transistor 10 are turned on, winding '1aLs and Lt cause winding '1aLs and Lt to turn on, and when transistor 8 and transistor 11 are turned on, winding 'its'.

L, respectively, form excitation poles.

Next, the rotation speed of the three-phase DC motor is, for example, 1800 rpm.
When the detector detects that the switching signal has reached the transistor 10, the switching signal turns on the transistor 9.
When turned ON, an excitation pole is formed by the winding L1, when the transistor 11 is turned ON, an excitation pole is formed by the winding Lm, and when the transistor 12 is turned ON, an excitation pole is formed by the winding Lm. .

When starting a three-phase DC motor, the volume &'iLI.

If the winding resistance of L, , L3 is r, the rotational speed Ω and the generated torque T are given by equations (3) and (4) as already obtained from equations (1) and (2).

When the rotational speed of the three-phase DC motor reaches a preset rotational speed of 180 Orpm after starting, the transistor 9 in FIG.
is turned on, the winding L++ LztL becomes as shown in FIG. 3(C), and the three-phase DC motor is switched from bipolar drive to unipolar drive. 3 in this case
The rotational speed Ω' of the phase-DC motor and the generated torque T' are (1)
, as already obtained using equation (2), as shown in equations (5) and (6).

From equations (4) and (6) obtained in this way, T-
27' is obtained, and when bipolar drive is started, twice as much torque as in unipolar drive is generated, and the engine starts smoothly with sufficient starting force, increasing the rotational speed in a short time.

Furthermore, as is clear from the comparison between equations (3) and (5), when the rotational speed Ω of the three-phase DC motor reaches the maximum rotational speed and the generated torque becomes sufficiently small, (3).

In equation (5), the second term is ignored with respect to the first term, and in steady state, a rotational speed Ω'-360Orpm, which is twice that of the conventional one, is obtained.

In this way, according to the embodiment, with low power consumption,
It is possible to drive a three-phase DC motor so that the torque at startup is sufficiently large to smoothly start up and reach a high steady rotation speed in a short time.

〔Effect of the invention〕

As described in detail above, according to the present invention, sufficient torque can be generated at startup with low power consumption, and a high steady-state rotation speed can be reached in a short time.

[BRIEF DESCRIPTION OF THE DRAWINGS] All the figures are for explaining the present invention in detail. Fig. 1 is a circuit diagram showing a control circuit of a three-phase DC motor, and Fig. 2 is a circuit diagram showing a control circuit of a three-phase DC motor according to an embodiment. 3(a), (b), and (c) are explanatory diagrams showing the schematic configuration of jI!, respectively. ! FIG. 3 is an explanatory diagram showing the connection state of wires and the flow of current. l...3-phase DC motor, 2...
...Stator, 3...Rotor, 5...
・・・・・・Analog switch, 6 to 12・・・・・・
...transistor, L+, Lm, La...
...winding wire. Figure 1 Figure 2 もS w

Claims (1)

[Claims] In a method for driving a three-phase DC motor comprising a stator having three-phase windings and a rotor that rotates in accordance with switching of the excitation phase of the stator, a common connection end of the three-phase windings is A common terminal is provided, and when the three-phase DC motor is started, bipolar drive is performed in which the two-phase windings are energized, and when the three-phase DC motor reaches a preset rotation speed, the common terminal is used to drive the three-phase DC motor. A method for driving a three-phase DC motor, characterized in that unipolar drive is performed by energizing one-phase winding.