JPH05122983A - Controller for permanent magnet motor - Google Patents

Abstract

PURPOSE:To suppress a copper loss and to improve an operating efficiency by reducing a reactive current component of a current of a motor as much as possible. CONSTITUTION:Currents of stator windings 11a of phases are detected by a current detector 14. A rotating position of a rotor of a motor 11 is detected by a rotary encoder 15. A memory 16 outputs a current command value responsive to the rotating position of the rotor. The command value is so previously stored as to become a waveform following to that of an induced voltage of the winding 11a. When the command value is output from the memory 16, comparators 18 to 20 apply compared results with the current to a control circuit 21, which applies a control signal to a driving circuit 12 so as to supply a current following to the induced voltage. Thus, a deviation of phases of harmonic wave components is eliminated to reduce a reactive current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet motor control device in which a rotor is provided with a permanent magnet and a stator winding is energized to drive the motor.

[0002]

2. Description of the Related Art A brushless motor using a permanent magnet as a rotor is widely used in OA equipment, AV equipment and the like, and structurally operates as a synchronous motor having a permanent magnet rotor. Is. Therefore, it is necessary to detect the rotational position of the rotor for synchronization.

The electrical configuration of the control device for rotating the motor is as shown in FIG. 7 (a), for example.
That is, the drive current is applied to the three-phase stator winding 2 of the motor body 1 by the drive circuit 3, and the drive circuit 3 is configured by connecting the transistors in a bridge and controlled by the control circuit 4. Signals are being given.

The control circuit 4 is adapted to be supplied with a signal indicating the rotational position of a rotor (not shown) of the motor 1 from three Hall elements 5 to 7 as position sensors, and controls based on this position signal. Generate a signal. The Hall elements 5 to 7 have a mechanical angle of 60 ° as shown in FIG.
Each of them is arranged to detect the position of the rotor at a position separated by an electrical angle of 120 °.

According to this structure, the Hall elements 5 to 7 are connected to the position shown in FIG.
Position signals as shown in (b) and (c) are output, and the control circuit 4 gives the control signals shown in (d) to (i) to the drive circuit 3 based on the position signals. In the drive circuit 3, the three-phase stator winding 2 is connected to the same figure (j),
A drive current as shown in (k) and (l) is applied, and the rotor is rotationally driven by this.

[0006]

In the conventional structure as described above, for example, the energizing current to the stator winding 2 is as shown in FIGS. 8 (j), (k) and (l). 12 in electrical angle
Three-phase energization is performed with a 0 ° phase shift. The drive voltage waveform at this time is as shown in FIG.

Since the commutation is performed by the signals from the Hall elements 5 to 7 and it is driven as a synchronous motor, the phases of the current and the drive voltage of the fundamental wave component are the same, and the fundamental wave power factor is "1". It has become.

However, the drive voltage waveform and the current waveform are greatly different as shown in FIG. 9, and the phases of the voltage and the current of the high-order harmonic component are largely deviated. Therefore, the power factor of the harmonic component is extremely low, and the motor 1 is driven in a state in which the total power factor of the fundamental wave power factor and the power factor of the harmonic component is low.

That is, in such a situation, the stator winding 2
Since the rotational drive is performed while supplying a reactive current to the stator winding 2, the copper loss in the stator winding 2 increases, and there is a problem that the operating efficiency of the motor decreases.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress the generation of copper loss in the stator winding by reducing the amount of reactive current flowing to the stator winding as much as possible. A controller of a permanent magnet motor capable of improving drive efficiency is provided.

[0011]

The controller for a permanent magnet motor according to the present invention is intended for a permanent magnet motor in which a rotor is provided with a permanent magnet and a stator winding is energized and driven. The present invention is characterized in that the current supplied to the stator winding is controlled so as to follow the induced voltage waveform specific to the stator winding.

[0012]

According to the controller of the permanent magnet motor of the present invention,
The current supplied to the stator winding is controlled so as to follow the waveform of the specific induced voltage induced in the stator winding by the rotation of the rotor, so not only the phase of the fundamental wave component but also the harmonic component , The total power factor can be brought close to 1, so that the reactive power flowing through the stator winding can be reduced and the efficiency as a motor can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1 showing the electrical configuration, a motor 1
1 comprises a stator winding 11a and a rotor having a permanent magnet. The drive circuit 12 includes a transistor 12a
To 12f are bridge-connected, and their output terminals are connected to the stator winding 11a of the motor 11.
In the drive circuit 12, the transistors 12a to 12f are switched according to the applied control signal, and the DC power supply 13 is energized to the stator winding 11a of the motor 11 in three phases.

The current detector 14 is arranged to detect the current flowing through each phase of the stator winding 11a of the motor 11. In addition, the rotary encoder 15 includes the motor 11
Is an absolute type rotational position detector that detects the rotational position of the rotor and outputs it as a digital signal of a plurality of bits, the output terminal of which is connected to the storage device 16.
The storage device 16 stores the data of the current command value corresponding to the rotation angle in advance, and the three output terminals are D
The rotary encoder 15 is connected to the A / A conversion circuit 17.
The current command signal is output according to the rotation angle signal given from the. In this case, the current command value is set to have a current waveform that is similar to the waveform of the voltage induced in the stator winding 11a by the rotation of the rotor.

The current command signal from the storage device 16 is output as a digital signal, and this current command signal is D / A.
The converter 17 converts the analog signal and outputs the analog signal.
Each of the comparators 18 to 20 has a D / A on one side of the input terminal.
It is connected to each output terminal of the converter 17, the other side is connected to each output terminal of the current detector 14, and each output terminal is connected to the control circuit 21.

Then, each of the comparators 18 to 20 has a D / A
The stator winding 11 supplied from the current detector 14 in response to the current command signal of each phase supplied via the conversion circuit 17.
The actual current value flowing in a is compared and the result is given to the control circuit 21. When the control circuit 21 receives a signal indicating the comparison result from the comparators 18 to 20, it supplies a control signal to the bases of the transistors 12a to 12f of the drive circuit 12.

Next, the operation of this embodiment will be described with reference to FIG. The rotary position of the rotor of the motor 11 is detected by the rotary encoder 15 and stored in the storage device 16
Entered in. The rotary encoder 15 uses, as a position detection signal, a digital signal of a plurality of bits corresponding to the rotation angle of the rotor on a one-to-one basis (the most significant bit in FIG. 2D, the following (e), (f) and the least significant bit). Of the current command value ((a), (b) in the figure) stored in accordance with the digital signal indicating the rotation angle. ) And (c)) are read out and output.

In this case, as described above, the storage device 16 stores in advance a pattern of the energizing current corresponding to the value of the induced voltage generated in the stator winding 11a according to the rotation angle of the rotor, The current waveform and the induced voltage waveform are similar to each other. That is, in the past,
The energization period of each phase corresponds to an electrical angle of 120 °, but in the present embodiment, the energization period corresponds to 180 ° according to the induced voltage waveform.

When a control signal is output from the storage device 16 as a digital signal corresponding to each of the three phases, the D / A
The conversion circuit 17 converts this into an analog signal and inputs it to the comparators 18 to 20, respectively. In the comparators 18 to 20, the current command value given via the D / A conversion circuit 17 is compared with the actual energization current of the motor 11 detected by the current detector 14. Then, at this time, when the energizing current is larger than the current command value, energization is stopped, and when it is small, energization is performed and a comparison result signal is output.

As a result, the control circuit 21 outputs an appropriate control signal corresponding to each of the three phases to the drive circuit 12, and the waveforms of the energized current and the induced voltage of the stator winding 11a substantially match. To be controlled. Therefore, by matching the waveforms of the two, there is no phase shift of the harmonic, and the generation of reactive current of the harmonic component is reduced.

According to this embodiment, the current supplied to the stator winding 11a is set so as to follow the waveform of the induced voltage generated in the stator winding 11a according to the rotation angle of the rotor. As a result, the phase shift of the harmonic components is reduced, the reactive current that occupies the entire energizing current can be significantly reduced, and the operating efficiency of the motor 11 can be improved as a whole.

FIGS. 3 and 4 show a second embodiment of the present invention, and only portions different from the first embodiment will be described below. That is, in the present embodiment, as shown in FIG. 3, an incremental rotary encoder 22 and an up / down counter 23 are used instead of the absolute rotary encoder 15 in the first embodiment. ..

That is, in the first embodiment, the absolute rotary encoder 15 generates a signal corresponding to the rotation angle of the rotor and supplies it to the storage device 16. In the above, the incremental rotary encoder 22 outputs a relative rotation amount of the rotor as a pulse signal and also outputs a pulse indicating a zero phase corresponding to the reference position of the rotor, which is used as an up / down counter 23. With the configuration, the rotational position is detected by counting from the position of the zero phase signal.

With this structure, the up / down counter 23 is reset at the time when the zero-phase pulse is input, and the rotation angle is set to zero at this time, after which the pulse is output from the rotary encoder 15. Each time is input, the count number is incremented and the rotation angle is relatively detected. Then, by the output signal of the up / down counter 23 corresponding to this rotation angle, the storage device 16 outputs a current command value of a phase corresponding to the rotation angle as a digital signal.

In the same manner as in the first embodiment, a current having a current waveform similar to the induced voltage waveform of the stator winding 11a is supplied to reduce the phase shift of the harmonic component as much as possible. Therefore, in this embodiment as well, since the position detection signal corresponding to the rotational position of the rotor is input to the storage device 16 as shown in FIG. 4, the same as in the first embodiment. The effect of can be obtained.

FIGS. 5 and 6 show a third embodiment of the present invention, and only portions different from the first embodiment will be described below. In this embodiment, the PLL (Phase
Locked Loop) is used to match the rotation speed of the motor 11 to the reference clock.

Now, in FIG. 5, the hall element 24 is arranged so as to detect the rotational position of the rotor of the motor 11. The signal output terminal of the hall element 24 is connected to one input terminal of the frequency comparator 25, and is also connected to the up / down counter 26. The reference clock generation circuit 27 is a circuit that generates a reference clock for operating the motor 11, and its output terminal is connected to the up / down counter 26 and the input terminal of the frequency dividing circuit 28. The frequency divider circuit 28 divides the input reference clock (frequency f0) into a predetermined frequency and outputs it as a speed reference pulse (frequency fa). Its output terminal is the other input terminal of the frequency comparator 25. It is connected to the.

The up / down counter 26 is reset by the zero phase signal from the Hall element 24 and then counts up the reference clock to output a position signal corresponding to the rotational position of the rotor, the output terminal of which is a storage device. It is connected to 16 input terminals. The three output terminals of the storage device 16 are connected to the comparator 2 via the D / A conversion circuit 17.
It is connected to one of the input terminals 9, 30, 31. The other input terminal of each of the comparators 29 to 31 is the frequency comparator 2
5 are commonly connected to the output terminals. In this case, the frequency comparator 25 compares the frequency of the position detection signal from the hall element 24 with the speed reference pulse signal of the predetermined frequency given from the frequency dividing circuit 28, and outputs the deviation signal. There is.

Each output terminal of the comparators 29 to 31 is connected to one input terminal of each of the comparators 18 to 20. The other input terminal of each of the comparators 18 to 20 is connected to each output terminal of the current detector 14.

Now, the case where the motor 11 has three phases and four poles in the above-mentioned structure will be described. In this case, the Hall element 24 is
A number of pulses (commutation signals) are generated as position signals and given to the frequency comparator 25, and one of the pulses is given to the counter 26 as a reset pulse indicating a zero phase. On the other hand, the frequency dividing circuit 28 is set to divide the reference clock given from the reference clock 27 and generate 24 pulses as speed reference pulses while the rotor makes one rotation.

The frequency comparator 25 detects the frequency fa of the speed reference pulse given from the frequency dividing circuit 28 and the Hall element 24.
Is compared with the frequency of the pulse given from, and if the rotation frequency of the rotor is low, an addition command is output to the comparators 29 to 31, and if it is high, a subtraction command is output. For example,
As shown in FIG. 6, the rotation frequency of the rotor is the frequency dividing circuit 28.
When the frequency is lower than the frequency from Δf1 and Δf2, the addition command is output and the rotation speed is controlled to increase.

When the feedback control is carried out in this manner and the steady state is reached, the frequency of the pulse from the Hall element 24 indicating the rotation frequency of the rotor and the frequency dividing circuit 28.
Since the speed reference pulse from the above is matched, the rotation state of the rotor is stabilized. In this state, the rotational position of the rotor can be obtained by counting the number of reference clocks output from the reference clock generation circuit 27, and the storage device 16 can obtain the current command value based on the signal from this counter. Output.

For example, if one current command value data is stored in the storage device 16 for an electrical angle of 1 °, and the motor speed is 1800 rpm, the frequency f0 of the reference clock is f0 = 360 ( Data) × 4 (poles) × 1800 (rpm) /60=43.2 (kHz) (1) Further, the frequency fa of the speed reference pulse by the frequency dividing circuit 28 becomes fa = 43.2 (kHz) / 24 = 1.8 (kHz) (2).

Then, the speed reference pulse fa and the actual motor speed are compared, and if the pulse interval of the motor rotation signal is longer than the time interval of the output pulse of the frequency dividing circuit 28, the output current is increased. On the contrary, when the pulse interval of the motor rotation signal is shorter than the time interval of the output pulse of the frequency dividing circuit 28, the output current is controlled to be reduced. Therefore, according to this embodiment as well, the same effects as those of the first and second embodiments can be obtained.

In the above embodiment, the control means is composed of hardware, but the present invention is not limited to this, and similar control may be performed by a program using a microcomputer or the like. In this case, the induced voltage generated in the stator winding 11a may be expressed as a function and obtained in correspondence with the position detection signal.

Further, in the above embodiment, the case where the present invention is applied to the three-phase motor 11 has been described. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to a two-phase, four-phase or five-phase motor.

[0038]

As described above, according to the controller of the permanent magnet motor of the present invention, the current induced in the stator winding is uniquely induced in the stator winding by the rotation of the rotor. Since it is configured to control so as to follow the waveform of the voltage, it is possible to reduce energization of the reactive current that does not contribute to the generation of the motor torque as much as possible, and thus it is possible to improve the operation efficiency of the motor. Play.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

[Fig. 2] Correspondence diagram of a current pattern and a rotation angle

FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG.

FIG. 5 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 6 is a view corresponding to FIG.

FIG. 7 is an electrical configuration diagram showing a conventional example.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a waveform diagram of actually measured induced voltage and conduction current.

[Explanation of symbols]

11 is a motor, 12 is a drive circuit, 14 is a current detector, 1
Reference numeral 5 is an absolute rotary encoder, 16 is a storage device, 17 is a D / A conversion circuit, 18 to 20 are comparators, 21 is a control circuit, 22 is an incremental rotary encoder, 23 is an up / down counter, and 24 is a hall. Reference numeral 25 is a frequency comparator, 26 is an up / down counter, 27 is a reference clock generating circuit, 28 is a frequency dividing circuit, and 29 to 31 are comparators.

Claims (1)

[Claims] 1. In a permanent magnet motor in which a rotor is provided with a permanent magnet and is driven by energizing a stator winding, a current supplied to the stator winding is an induced voltage specific to the stator winding. A controller for a permanent magnet motor, which is controlled so as to follow a waveform.