JPS61227698A - Controller for inverter - Google Patents

Abstract

PURPOSE:To enable the attenuation effect of noise to be easily and exactly obtained, by detecting noise and by controlling frequency so that the noise may be diminished. CONSTITUTION:Troublesome noise generated from a motor 2 and a fan 3 is detected by a noise detector 4. A frequency change control circuit 9 is organized with a reference power source 11, a micro-computer(micon) 12, and a variable frequency width setting circuit 13, and when the noise level detected by the noise detector 4 is equal to the reference level or more, then the output of voltage Vf2 is generated in order to change the frequency of an inverter so that the noise level may be lowered. The voltage Vf2 is added to voltage Vf1 from a frequency setting circuit 15 by an addition circuit 17, and the output frequency of the inverter is decided.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is used in a device for driving an AC motor with a load such as a blower or a compressor using a variable frequency inverter, and provides an inverter that can reduce noise. Regarding a control device.

[Conventional technology and its problems]

If, for example, a high mR frequency included in the voltage supplied from the inverter to the motor matches or comes close to the mechanical co-op frequency of the motor and/or the load, the noise due to the mechanical co-op will increase. For this reason, there is a method of inserting a reactor between the inverter and the motor to remove harmonic components. However, the disadvantage of this method is that it becomes thicker and requires an accelerator.

Also, if the reactor becomes large, there will be a drawback that the motor power will be insufficient.

On the other hand, it is conceivable to operate the motor and load in advance, measure the inverter frequency at which harsh noise occurs, and design the inverter so that it is not continuously operated at this frequency. However, this method is inferior in versatility because it is necessary to measure the frequency Y of noise generation in advance.

Also, if the frequency that generates noise changes due to the change in time,
It becomes difficult to reduce noise.

Therefore, an object of the present invention is to
An object of the present invention is to provide an inverter control device that can reduce noise.

Means for Solving Problem c] To achieve the above object, the present invention provides a control device for a variable frequency inverter for driving a cross-flow motor provided with a load. 4. A noise detector for detecting noise is provided, and the noise detected by the noise detector is detected. This invention relates to an inverter control device that is equipped with a frequency control circuit for changing the frequency of the inverter to reduce the noise level when the noise level exceeds the standard level. It is.

[For production]

In the above invention, when the level of the detected noise is equal to or higher than the basic noise level, the frequency of the inverter is changed to reduce the noise. This allows the mechanical resonance frequency of the motor and/or load and the output frequency of the inverter or its height l! The difference between the second wave component and the second wave component increases, and the noise level decreases.

〔Example〕

Next, with reference to FIGS. 1 to 4, an inverter according to an embodiment of the present invention and its l! IJ all! Explain i&.

In FIG. 1, R (1) is a variable frequency inverter, and in this embodiment, the pulse width can be changed! ! 161 (PWM J
This is a D C-A C inverter. (2) is an AC motor, which is driven by the output of the inverter (1). (3) is a fan as a load, which is coupled to the motor (2).

(4) is a noise detector, which includes a motor (2) and a fan (
3), an amplifier (6), a filter (7) with a passband in the audible frequency range of several hundred Hz to 2 kHz, and an amplifier (8). This circuit detects the harsh noise generated by the motor (2) and fan (3).

(9) is a frequency change control circuit, which consists of a voltage comparator a [, a reference turtle pressure point Qll, a microcomputer (121), a variable frequency width setting circuit 1131, and a digital/analog converter side. This frequency change control circuit (9) generates a voltage Vf corresponding to the frequency Δf to be changed. ◎ α is a frequency setting circuit, which is connected to a variable resistor (1 bit-) to the DC power supply +V, and is connected to the set frequency fs. Corresponding voltage V
f. The setting of the voltage V(, by the frequency setting circuit [151) may be performed manually or may be performed automatically based on temperature detection.

αη is a zero arithmetic circuit, and the voltage V of the one-frequency foot circuit α
voltage vf, which determines the inverter output frequency by adding f, and voltage vf of the frequency change control circuit (9), +V
It outputs f*=Vf. The output line of the 7FD arithmetic circuit α is the frequency of inverter (1) 1ffll 4
connected to the circuit.

Next, the operation of the apparatus shown in FIG. 1 will be explained using FIGS. 2 to 4 as rare examples.

The output frequency f of the inverter (1) is 1 frequency setting circuit α
The inverter (1) is configured to change in response to a change in the output voltage V(, . 9. When controlling this inverter (1) by PWM, for example, a sine wave and a triangular wave are used, as shown in principle in FIG. By comparison, a control pulse as shown in FIG.

Note that the output frequency is divided into a plurality of blocks, and the frequency of the triangular wave (carrier) is changed for each block.

That is, when the frequency is low as shown in Figure 1M4 (N).

As shown in FIG. 4 and 10, control is performed so that the number of times of switching in a period is the same as in the case where the frequency is high.

While changing the output frequency f of the inverter (1),
If the frequency of the triangular wave (carrier) is changed for each block shown divided by the dashed line in Figure 2, motor (2) and fan (
The peak of the noise generated in 3) occurs in each block.

In this embodiment, when the noise level shown by waveform Q8 is higher than the base noise level a9, it is lowered to below this level. The noise peak of each frequency block in Figure 2 is the base layer v /< AZ
When it is larger than α, noise reduction control is performed in any block.

Figure B3 shows an enlarged view of the change in the noise level of one block in Figure M2. A noise detection voltage vN corresponding to the noise shown in FIG. 3 is obtained from the noise detector (4).

The output line of this noise detector (4) is connected to one input terminal of a comparator aω, and the other input terminal of a comparator QO is given a base voltage vR corresponding to the reference bell a in FIG. Since the basic voltage source αυ is connected.

A comparison voltage between the two is generated from the comparator. if.

When the noise detection voltage V is lower than the base layer 1 pressure, the microcomputer (121) does not generate the frequency changing voltage Vh for shifting the output frequency f.

The inverter (IJ) is controlled by Vf, which is equal to the voltage Vh of the frequency setting circuit 051.

On the other hand, if the noise level is determined to be at point A of waveform a8 in FIG. 3, the operation of changing the output frequency f of the inverter υ starts. In this embodiment, a variable frequency width setting circuit u3 is provided, and this circuit uses a variable frequency width Δf(
A control signal indicating 2 Hz) is given to the microcomputer Q2+. For this reason, the microcontroller generates frequency variable data (frequency sweep signal) corresponding to ±2 Hz, which is converted into an analog signal by the digital/analog converter I. (17).As a result, the 1-frequency control am pressure Vf also changes following the change in Vf, and the output frequency f of the inverter (1) changes by 2 Hz, for example, at intervals of 0.5 Hz.

That is, if the frequency A, 40 in FIG. The noise detection voltage vN corresponding to 40 to 44 Hz is obtained, which is converted from analog to digital and written to the memory (RAM) in the microcontroller αΔ. Determine whether there is a frequency below level 09. Then, if it is found that there is a frequency that can be made below the reference level a9, the frequency that is closest to point A in Figure 3 and below the reference level a9 is determined. In the example of Figure 3, select the frequency of .

Since the A point of 42.5Hz is the standard, the bell is below a9.

A frequency of 42.5Hz is selected. And 42.5
Data corresponding to -42.0 = +0.5 Hz is output from the microcomputer α, and the frequency changing voltage V(.

is applied to the power zero calculation circuit (In. As a result, the inverter (1) is operated at a frequency of 42-5 Hz.

If the operating frequency of inverter (1) is 40
If the frequency is Hz, point B (39Hz) is closest to 40Hz in the 2Hz range and lower than the base level α9.
will be changed to

With this device: If there is no frequency below the standard bell QIJ'J in the variable frequency range of 2 Hz.

Control is performed to obtain the frequency that produces the lowest noise within the variable frequency range.

[Modified example]

The invention is not limited to the embodiments described above.

For example, the following variations are possible.

(a) It is also possible to detect the loudest noise of either one without detecting the total value of the noise of the motor (2) and the noise of the fan (3). Furthermore, the present invention is not limited to the fan (3), and can of course be applied to cases where another device such as a compressor is coupled to the motor (2).

When the frequency is changed by 2 Hz using the C-microcomputer α power, the frequency that produces the lowest noise level may be selected and the operation may be performed at this frequency. In other words, when point A is detected in FIG. 3, operation may be performed at a higher frequency than point A.

el If there is no frequency below the base level in the first frequency change operation, variable frequency width setting circuit α3
The variable frequency width may be expanded to, for example, 4 Hz. Alternatively, the variable frequency range may be sequentially changed until the frequency falls below the base level. Also, i&
Even if it is initially detected that the noise level is below the base level, the noise may be controlled to the lowest noise frequency within the variable frequency range (!2 Hz).

(# It is also applicable when obtaining the output voltage of the inverter (1) by the PAM method.

〔Effect of the invention〕

As is clear from the above, according to the present invention, noise is detected and the frequency is controlled to reduce the noise.
A noise reduction effect can be easily and reliably obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an inverter device according to an embodiment of the present invention. FIG. 2 is a characteristic-1 diagram showing the relationship between the inverter output frequency and noise. FIG. 3 is a characteristic diagram showing a part of FIG. 2 in an enlarged manner. FIG. 4 is a waveform diagram showing PWM control of the decoy inverter. (1)...Inverter, (2)...Motor, (3)
...Fan, (4)...Noise detection a, (9)...
Frequency change control circuit.

Claims (1)

[Claims] (1) In the control equipment of a variable frequency inverter for driving an AC motor with a load, the motor and/or
Alternatively, a noise detector is provided to detect the noise of the load, and when the level of noise detected by the noise detector is equal to or higher than a reference level, the frequency of the inverter is changed to lower the noise level. An inverter control device comprising a frequency control circuit for controlling an inverter.