JPS5956895A - Controller for inverter - Google Patents

Abstract

PURPOSE:To operate an inverter with low noise by varying the value of chopping frequency whenever the prescribed time period is elapsed directly after acceleration or deceleration and selecting the lowest range of the detected output of the motor noise to apply a chopping frequency command. CONSTITUTION:A signal of a speed setter 1 is applied through an acceleration/ deceleration regulator 2 to a level signal generator 5, inputted together with the chopping frequency of a triangular wave generator 4 to a modulator 6 to obtain a modulation output, thereby controlling a sinusoidal wave modulation type pulse width controlled inverter to drive an induction motor. At this time the output of a flip-flop 3a connected to both terminals of the regulator 2 is applied to an oscillator 3b, a selector 3c is controlled via a comparator 3e which inputs the signals from a counter 3d and a noise detector 3g, thereby operating the generator 4. Accordingly, the lowest noise range is selected to instruct the chopping frequency, thereby enabling to operate the inverter with low noise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction motor drive device using a sine wave modulation type pulse width control inverter, and particularly to an inverter control IQ F: for operating the motor with low noise.

Conventionally, in inverters that generate variable voltage/variable frequency AC output, pulse control expansion is often used as a method of adjusting the number of pulses per cycle of the output frequency to obtain the desired fundamental voltage. There is. When adjusting the magnitude of the output voltage by controlling the pulse width, that is, the number of pulses, the output voltage has a rectangular waveform, so it contains voltages of higher harmonic components in addition to the fundamental voltage. Therefore, in such an induction motor pivoting system, a sine wave modulation method, which has few low-order harmonic components, is particularly preferred. This will be explained with reference to FIG.

Figure 1 is an explanatory diagram showing an example of operation of sinusoidal modulation type pulse width control, where ■υ, Vv, and Vw are level signals, and wT
n is a triangular carrier wave signal, and UO is a U gate signal. Incidentally, since such a sine wave modulation operation is well known, its Ml'51fl theory9 will be omitted here.

Now, the width of the chisel Tsuping Zhou JtJI CoI is "KL"
As long as the peak value of the motor current waveform does not exceed the limit,
Therefore, the chilling frequency Foi1 can be reduced within a range that does not exceed the above-mentioned limit. Further, the required minimum width of the chipping period CoI+ is determined by the turn-off time and the turn-off time of the switching element.

In this way, the chopping frequency F'c+1 can be changed freely to some extent. In addition, mill l, lj
When you want to increase the Q voltage, use the level signals ■U, ■■, v
All you have to do is increase the magnitude of w or decrease the magnitude of the carrier signal WTR.If you want to change the motor frequency, you can change the motor cycle CM, and the chopping frequency F
It is clear that if you want to change the OR, you just need to change the width of the chopping period Co).

When a motor is driven with a sine wave modulation function as described above, in addition to the fundamental wave voltage, a voltage component due to the chopping frequency FCH and a voltage component of the harmonics of the integer part thereof are generated. For this reason, the harmonic components and ? ! f, lb
If the resonant frequencies of mechanical parts match or approach, large noise will be generated, but if this can be avoided, such noise can be eliminated and reduced to a small level. Next, a specific example of the above-mentioned harmonic voltage is shown in FIG.

Figure J2 shows an example of the main harmonic 1 [positive value] generated based on the chopping frequency. In the figure, the ridge is the fundamental wave frequency rc'! i35.1Lz, the characteristic CC1 of the fundamental wave voltage 140■ is shown, and the dotted line and the dashed line indicate the chopping frequency Fon for the same fundamental wave (FOI (= 945
Hz) and (FOH=1155Hz), the characteristics CC2 and CC3 are shown, respectively.

Here, the resonant frequency of the motor components is now 1900H.
If it is near z, then the chopping frequency (Fon=
9451(z) characteristic CC2 double frequency 189
0Hz is close to that, and even though electric motors generate a lot of noise, the chipping frequency (F□H=1155Hz
), the double frequency is 2310)
(z, and this frequency of 2310Hz is the resonant frequency of 19
Since the frequency is far from 00 Hz, the electric motor can generate only a small amount of noise. In an electric motor, each component has a different mechanical resonance frequency.

The present invention focuses on the above-mentioned points, and even though the motor frequency is changed at a certain chopping frequency during acceleration/deceleration of the motor, chi-sobbing is performed at certain time intervals immediately after constant speed. The driving frequency is changed to set the noise level at that time to 48 mm, and the chopping frequency that produces the loudest noise is selected from among the various chopping frequencies, and this is used to send a signal. The object of the present invention is to provide a device that can realize low-noise operation of a motor.

FIG. 3 is a basic circuit configuration diagram shown to facilitate understanding of the technical idea of the present invention, in which 1 is a speed setting device that generates a speed setting signal N, and 2 is a capacitor and a resistor, for example, an acceleration/deceleration regulator that generates an output voltage that reaches the sudden change level by delaying the sudden change in time; 3, a frequency selection command circuit (hereinafter simply referred to as the selection command circuit); 4, a triangular wave; 5 is a level signal generator, and 6 is a transformer. Here, the selection command circuit 3 includes a flip-flop 3a and a count oscillator 3b.
.

It consists of a chopping frequency selector 3c, a counter 3d, a comparator 3e, an analog-to-digital converter (hereinafter referred to as AD converter) 3f, and a microphone 3g. Further, the triangular wave generator 4 is given a tiloping frequency command signal DOH from the selection command circuit 3 and generates a carrier wave signal WTR as shown in FIG. The modulator 6 generates level signals U r V r vw as shown in FIG.
UG, VG, and wo are obtained as modulated outputs. These have been described above, and detailed explanation thereof will be omitted. Next, this circuit configuration will be explained in detail using the waveform diagram of each part shown in FIG.

First, in the selection command circuit 3, the flip-flop 3a
inputs the speed setting signal Ns and the speed command signal N of the input/output of the acceleration/deceleration regulator 2. Here, flip-flop 3a
has a slight hysteresis characteristic, and it is possible to determine whether it is accelerating or decelerating or at a constant speed based on the power of the two people.
L" is generated or when the two forces are almost equal, the signal output is "
1('' is generated.

Furthermore, the output of the flip-flop 3a is output from the count oscillator 3.
b and a chopping frequency selector 3ci are given,
The count oscillator 3b output is the chopping frequency selector 3
c, the sound pressure level of the noise is applied to the counter 3d and the comparator 3e, and the sound pressure level of the noise is applied to the comparator 3e through the AD converter 3f from a microphone 3g disposed as a noise detector of a motor (not shown). Furthermore, the output of the counter 3d is given to the comparator 3e, and the chopping frequency selector 3c
is configured such that the output of the counter 3d and the output of the comparator 3e 14j are applied to the output of the counter 3d.

The various operating states of the selection command circuit 3 as described above are as follows.

That is, the output signal FF of the flip-flop 3a is “L”.
'' level, as shown in FIG. 4, the flip-flop 3a operates the chopping frequency selector 3C to generate a signal of a certain predetermined chopping frequency command CH. As a result, the triangular wave generator 4 will send out a signal at a predetermined rubbing frequency even if the motor frequency changes.

Next, the output signal FF of the flip-flop 3a is rHJ
In the case of level, the count oscillator 3b has a certain period of time'
rt l T2 r T3 + T4 t T5 r
Pulse PI r P2 +P3 r P4 every T6
r P5 + re. First, the chopping frequency selector 3 receives the pulse P1 signal.
c is a certain chopping frequency command C during time T
Generate H. At this time, the comparator 3e obtains the sound pressure level of the motor in this operating state from the AD converter 3f as an output signal PH, stores it together with the pulse P1, and holds the state. Thereafter, when the pulse P2 is sent to the chopping frequency selector 3C and the comparator 3e, a chopping frequency command CH2 is further generated to obtain the sound pressure level in that state. Here, the comparator 3e compares the sound pressure level during pulse P1 and the sound pressure level during pulse P2, and stores the smaller pulse number and sound pressure level. . In this way, the chopping frequency selector 3C selects chopping frequency commands C1 (1, CH2, CH3, CH4, CH
S +Cl16 is sent as a signal, and the sound pressure level of the previous motor noise is obtained by the AD converter 3f, and the comparator 3e compares the smaller one of the previous sound pressure levels with the new one, and selects the smaller one. The sound pressure level and its pulse number are stored.

Furthermore, when the output signal C of the counter 3d that counts the pulses output from the count oscillator 3b changes from the rLJ level to the "■]" level, the chopping frequency selector 3
c and the comparator 3e do not obtain the pulse number of the count oscillator 3b, and the comparator 3e provides the chopping frequency selector 3c with the memory capacity that minimizes the noise obtained, and therefore the pulse number and sound pressure level. becomes. This is the frequency command signal I) OH which chops the frequency command CH2 by one pulse P2 as shown in the example.
is given to the triangular wave generator 4, and the second
As explained above using the dashed line in the figure, the present invention can provide an inverter control device that can perform exceptional control with low noise and electric operation.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the operation of sinusoidal liquid H1 method pulse width control, Fig. 2 is a characteristic diagram showing an example of main harmonic voltage values based on the chopping frequency, and Fig. 3 is the technical idea of the present invention. FIG. 4 is a basic circuit configuration diagram shown for easy understanding, and FIG. 4 is a waveform diagram of each part shown for explanation of FIG. 1. Speed setter, 2. Acceleration/deceleration adjuster, 3. Chopping frequency selection command circuit (selection command circuit), 4. Triangular wave generator, 5. Level signal generator, 6. Modulator, DcH.
Chopping frequency command signal. Patent applicant: Toyo Denka Seizo ((ζ Type Company Representative: Atsushi Doi 3rd Hisatoshi 4th)

Claims (1)

[Claims] In an induction motor driven by a sinusoidal modulation type pulse width control type inverter, the tipping frequency value of the induction motor is changed at regular time intervals immediately after acceleration/deceleration of the exciter. A switching frequency selection command means is provided which selects the lowest output of a noise detector that obtains the sound pressure level of the electric motor from among the values of the switching frequency and provides a switching frequency command in the low range. f. Inverter ft+lI control device.