JPH04317593A - Controller for motor - Google Patents

Abstract

PURPOSE:To provide a motor controller in which inconvenience such as an increase in an irregularity of a torque caused by a current waveform distortion, an increase in an irregularity of a rotating speed, etc., is eliminated by preventing simultaneous occurrence of periods of dead times in two or more phases. CONSTITUTION:A central arithmetic processor 10 calculates an A-phase PWM signal, a B-phase PWM signal, a C-phase PWM signal to be supplied to phases, sequentially shift them by a short-circuiting preventing time (dead time), and adds them to an A-phase driver 11, a B-phase driver 12, a C-phase driver 13. The drivers 11, 12, 13 respectively form drive signals UA and DA, UB and DB, UC and DC having dead times corresponding to the A-phase, B-phase, C-phase signals.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a motor control device suitable for controlling synchronous motors, induction motors, etc., and in particular, the present invention relates to a motor control device suitable for controlling synchronous motors, induction motors, etc. The present invention relates to a motor control device that improves torque unevenness and speed unevenness caused by distortion of current waveform.

0002

[Prior Art] Conventionally, a three-phase voltage type PWM inverter (DC-AC conversion circuit) has been known as a motor control device for controlling, for example, a three-phase motor. In order to prevent short-circuiting of the DC power supply, a short-circuit prevention time (hereinafter referred to as dead time) is provided in the pulse width modulation signal of each phase. That is, in a three-phase voltage source PWM inverter, a switch consisting of six transistors, two for each phase, is provided, and the two transistors for each phase control the PWM applied to each phase.
(Pulse Width Modulation) They are turned on and off alternately in response to the signal, but in order to prevent two transistors in each layer from turning on at the same time due to variations in the on/off time of each transistor, causing a short circuit in the DC power supply. A short-circuit prevention time, ie, a dead time, for turning off two transistors of each phase simultaneously is provided in the PWM signal of each phase.

0003

[Problems to be Solved by the Invention] However, in the conventional motor control device as described above, when the dead time period occurs in two or more phases at the same time, distortion of the current waveform becomes large. However, there has been a problem in that various problems such as an increase in torque unevenness and an increase in rotational speed unevenness occur.

Therefore, the present invention provides a motor that suppresses disadvantages such as increased torque unevenness and increased rotational speed unevenness caused by current waveform distortion by preventing dead time periods from occurring simultaneously in two or more phases. The purpose is to provide a control device.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention supplies a pulse width modulation signal to each phase of a multi-phase motor, and also provides a direct current power supply short circuit to the pulse width modulation signal of each phase. The motor control device is provided with a short circuit prevention time for preventing short circuits, characterized in that a control means is provided for sequentially shifting the pulse width modulated signals of each phase by the short circuit prevention time.

[0006]

[Operation] The pulse width modulation signals supplied to each phase are sequentially shifted by the short-circuit prevention time by the control means, so that the short-circuit prevention time does not occur simultaneously in two or more phases, resulting in current waveform distortion. This suppresses the resulting increase in torque unevenness and rotational speed unevenness.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention. The motor control device of this embodiment controls a three-phase motor, and a three-phase control circuit is shown in FIG.

In FIG. 1, a central processing unit (CPU
) 10 is a PWM (pulse width modulation) signal for each phase necessary to obtain the desired motor speed or motor torque;
That is, A-phase PWM signal, B-phase PWM signal, C-phase PW
The M signal is calculated, and the A-phase PWM signal is applied to the A-phase driver 11, the B-phase PWM signal is applied to the B-phase driver 12, and the C-phase PWM signal is applied to the C-phase driver 13.

The A-phase driver 11 forms two drive signals UA and DA having a dead time from the A-phase PWM signal, amplifies their power, and outputs them.

Further, the B-phase driver 12 forms two drive signals UB and DB having a dead time from the B-phase PWM signal, amplifies their power, and outputs them.

Further, the C-phase driver 13 forms two drive signals UC and DC having a dead time from the C-phase PWM signal, amplifies their power, and outputs them.

In FIG. 2, the control circuit of this embodiment is as follows:
3-phase AC power supply 21, a diode bridge circuit 22 consisting of six diodes that rectifies the 3-phase AC output from the 3-phase AC power supply 21 into DC, a smoothing capacitor 23 for smoothing the output of the diode bridge circuit 22, 6 transistors TR1, TR2, TR3, TR4, TR
5 and TR6, and a three-phase motor 25 in which the current of each phase is controlled by the switching circuit 24.

Here, the two drive signals UA and DA output from the A-phase driver 11 shown in FIG. 1 are as shown in FIG.
The transistor TR1 of the switching circuit 24 shown in FIG.
2 is added as a switching signal to the base of TR2 and output from the B-phase driver 12 shown in FIG.
The two drive signals UB and DB are applied as switching signals to the bases of transistors TR3 and TR4 of the switching circuit 24 shown in FIG.
Two drive signals UC and DC output from the phase driver 13 are applied as switching signals to the bases of transistors TR5 and TR6 of the switching circuit 24 shown in FIG. 2, respectively.

Next, the operation of this embodiment will be further explained with reference to the timing chart shown in FIG.

The CPU 10 shown in FIG.
signals, i.e., A-phase PWM signal, B-phase PWM signal, C
A phase PWM signal is formed and output. Here, the CPU 10 examines the pulse width of the PWM signal of each phase, and sequentially shifts the pulse width by a time corresponding to the dead time and outputs the signal in descending order of the pulse width. This state is shown in FIGS. 3(a), (d), and (g). In addition, in FIG. 3, TA, TB, TC
indicates the pulse width of each of the A-phase PWM signal, B-phase PWM signal, and C-phase PWM signal, and in the first half PWM period of FIG. 3, the pulse width of each PWM signal is TA < TB < T
In the latter half of the PWM cycle, each PWM
The case where the pulse width of the M signal is TB < TC < TA is shown.

As is clear from FIG. 3, in the first half PWM cycle, the pulse width of each PWM signal is TA < TB
<TC, so at the start of this first half PWM cycle, the A-phase PWM signal is first output (see Figure 3(a)).
), then the B-phase PWM signal is output with a delay of time t corresponding to the dead time from this A-phase PWM signal (see Fig. 3(d)), and then the B-phase PWM signal is The C-phase PWM signal is output with a delay of a time t corresponding to the dead time, that is, a delay of a time 2t, which is twice the time t corresponding to the dead time, from the A-phase PWM signal (see Fig. 3 (g)). ).

[0018] Also, in the latter half of the PWM cycle, each PWM
Since the pulse width of the M signal is in the relationship TB < TC < TA, at the start of this second half PWM cycle, the B
A phase PWM signal is output (see FIG. 3(d)), and then,
The time t corresponding to the dead time from this B-phase PWM signal
The C-phase PWM signal is output with a delay of 100 min (see Fig. 3 (g)), and then the C-phase PWM signal is delayed by a time t corresponding to the dead time, that is, the dead time is output from the B-phase PWM signal. A time 2t which is twice the time t corresponding to
The A-phase PWM signal is output with a delay of
reference).

[0019] The A-phase PWM signal, the B-phase PWM signal, and the C
The phase PWM signals are respectively supplied to an A-phase driver 11, a B-phase driver 12, and a C-phase driver 13.
1 forms two drive signals UA and DA corresponding to the A-phase PWM signal (see FIGS. 3(b) and (c)), and the B-phase driver 12 forms two drive signals UB and DA corresponding to the B-phase PWM signal. Form a DB (see Figures 3(e) and (f))
, the C-phase driver 13 forms two drive signals UC and DC corresponding to the C-phase PWM signal (Fig. 3(h), (
(see i)). Here, 2 formed by the A-phase driver 11
A dead time is formed in the two drive signals UA and DA in which the two drive signals UA and DA become low level at the same time, and a dead time is formed in the two drive signals UB and DB formed by the B-phase driver 12. A dead time is formed in which the drive signals UB and DB are at low level at the same time, and also in the two drive signals UC and DC generated by the C-phase driver 13, these two drive signals UC and DC are at low level at the same time. A dead time is formed.

[0020] Therefore, according to such a configuration, dead time of each phase does not occur simultaneously, and therefore, distortion of the current waveform due to simultaneous occurrence of dead time of two or more phases does not occur. Further, increases in torque unevenness and speed unevenness due to distortion of this current waveform are also suppressed.

[0021]

[Effects of the Invention] As explained above, according to the present invention, the pulse width modulation signals supplied to each phase are sequentially shifted by the short circuit prevention time. The short-circuit prevention time no longer occurs at the same time, and it is possible to reliably suppress increases in torque unevenness, rotational speed unevenness, etc. caused by current waveform distortion.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a motor control device of the present invention.

FIG. 2 is a circuit diagram showing an example of a control circuit used in the embodiment shown in FIG. 1;

FIG. 3 is a timing chart explaining the operation of the embodiment shown in FIG. 1;

[Explanation of symbols]

10 Central processing unit (CPU) 11
A-phase driver 12 B-phase driver 13 C-phase driver 21 3-phase AC power supply 22 Diode bridge 23 Smoothing capacitor 24 Switching circuit 25 3-phase motor

Claims (1)

[Claims] 1. A motor control device that supplies a pulse width modulation signal to each phase of a multi-phase motor, and provides a short circuit prevention time for the pulse width modulation signal of each phase to prevent short circuits in the DC power supply. A motor control device comprising a control means for sequentially shifting the pulse width modulation signal of each phase by the short circuit prevention time.