JPH02211092A - Pwm power converter - Google Patents

Abstract

PURPOSE:To prevent the magnetic sound of a motor from increasing and to convert the sound into a convenient sound by differentiating a carrier frequency for PWM control of PWM power converters respectively provided for a plurality of motors for supplying variable voltages in predetermined relationship. CONSTITUTION:An induction motor 2A is driven with VVVF AC inverted from a DC power source 3A by an inverter 1A. The output of a speed command circuit 8A is V/F-converted by a V/F converter 7A, and input to a voltage command circuit 6A. The circuit 6A generates voltage command patterns having a phase difference of 120 deg., which are compared with an output f1 of an oscillator 5A for generating a carrier signal by comparators 9B-11B to form a PWM signal, thereby controlling switching elements TUP-TWN via a gate 4. Other motors 2B, 2C are controlled entirely similarly, but carrier frequencies f1-f3 are combined to form a chord. Thus, electromagnetic sounds generated from the motors 2A-2C are simplified, not amplified, and converted into convenient sound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a PWM power converter, and particularly to reducing electromagnetic noise generated from a plurality of electric motors and improving the pitch thereof.

[Conventional technology]

When a motor is driven by a PWM inverter, harmonic current flows due to harmonic voltage components included in the pulsed inverter output voltage, and magnetic sound is generated from the motor. Therefore, conventionally, when magnetic noise is a problem, torque ripple is allowed to occur and PAM (pulse amplitude modulation) control is used, and when torque ripple is a problem, magnetic sound is allowed to occur and PWM (pulse amplitude modulation) control is used. A method for making it possible to select width modulation control is described in Japanese Utility Model Application Laid-Open No. 61-52497.

[Problem to be solved by the invention]

However, the above conventional technology
There is no mention of making the magnetic noise of the electric motor pleasant through WM control, nor is there any mention of countermeasures against the increase in magnetic noise that occurs when a plurality of electric motors are operated at the same time.

An object of the present invention is to provide a PWM power converter that can prevent an increase in the magnetic noise of the motors even when a plurality of electric motors are operated simultaneously by the PWM power converter, and can also make the magnetic noise a pleasant sound. .

[Means to solve the problem]

The above purpose is to set the carrier wave frequency of PWM control of each power conversion device that supplies variable voltage to multiple electric motors in a predetermined relationship 1.
For example, this can be achieved by varying the musical scale or chord relationship.

[Effect]

PW of each PWM power converter that drives multiple motors
Since the carrier wave frequencies of the M control are different, the magnetic sounds generated by each motor have different frequencies, and the result of combining them does not amplify a specific frequency. Furthermore, since the carrier wave frequencies are selected so that the result of combining the carrier wave frequencies of each PWM power converter becomes a musical chord, the magnetic sound generated from each electric motor also becomes a chord, making it a pleasant sound. .

〔Example〕

A first embodiment of the invention is shown in FIG. The first embodiment is a case where a plurality of electric motors 2A, 2B, and 2C are operated simultaneously by respective PWM inverters LA, IB, and IC. Inverter devices IA and IB.

Since each IC has the same configuration, the configuration of the IA that operates 2A will be explained here. In Figure 1, PWM
Inverter IA converts the DC voltage applied from DC power supply 3A into AC voltage. The inverter IA includes Graetz-connected self-extinguishing elements TUP, TVP, ... TWN and a feedback diode DUP connected in antiparallel to each self-extinguishing element.
, DVP...DWN. As the self-extinguishing element, a switching element such as a transistor or a gate turn-off thyristor is used. An induction motor 2A is connected to the AC output terminal of each phase U, V, and W of the inverter IA.

The speed command signal of the speed command circuit 8A is applied to the voltage-frequency converter 7A. The voltage-frequency converter 7A determines the output frequency of the inverter IA (the primary frequency of the electric motor 2A) with a zero frequency converter number that outputs a frequency command signal proportional to the speed command signal.

The voltage command circuit 6A generates a voltage command pattern signal with an amplitude proportional to the magnitude of the frequency command signal and a phase difference of 120° where one frequency is proportional to the frequency command signal.

Output ν, umbrella, νW*. Voltage command pattern signal
I, yv Shin, 9. * indicates comparator 9A.

10A, added to IIA. The output signal of the oscillator 5A that generates a carrier wave signal for pulse width modulation control is 9A,
Added to IQA and IIA. Gate circuit 4 is comparator 9
A, IOA, and switching element TUP, according to the PWM pulse outputted by IIA.

TVP, . . . give gate signals to TWN.

Next, the operation will be explained.

The first @ control method is a constant V/f control method using a PWM innometer, and AC voltage command signals 5*, 5, and 5 are output from the speed command signal of the speed command circuit 8A.

The output voltage of each phase is controlled in accordance with the PWM signal obtained by calculating .

Next, each inverter device LA, IB according to the present invention.

The method for selecting the IC carrier frequency is shown in Figures 3 and 4.
This will be explained with reference to FIG.

When operating multiple electric motors 2A, 2B, and 2C simultaneously with their respective PWM inverters LA, IB, and Ic, the PWM
When motor 2A is operated by inverter IA, comparator 9A
, IOA, and IIA, a high-frequency current flows due to the harmonic voltage components included in the PWM pulses output from the motor 2.
A more unpleasant electromagnetic bass is generated. Other electric motors 2B, 2
At the same time, unpleasant electromagnetic bass is generated from C.

Therefore, in the present invention, the electromagnetic bass generated from each electric motor 2A, 2B, 2G has a carrier wave frequency fl of each PWM control,
Focusing on things related to fz e fa.

The frequencies of the oscillators 5A, 5B, and 5C that generate these carrier wave frequencies fl, fz, and fa are made to differ in a predetermined relationship. This will be explained below. Fifth
As shown in the figure, harmonic current components twice the carrier frequency flow through the motor.

Carrier frequency f1 of PWM inverters LA, IB, and IC
, fz, fδ and the frequency of electromagnetic bass generated from the electric motors 2A, 2B, and 2C have a 1:2 relationship. Furthermore, there is a relationship between the carrier wave frequency and the scale code as shown in Figure 3, and by changing the carrier wave frequency as shown in Figure 3, it is possible to obtain a sound corresponding to an arbitrary scale code from the electric motor. can. Therefore, in the present invention, the carrier frequency of each PWM inverter IA, IB, and IC is made different as shown in FIG. 3 to create a chord as shown in FIG. 4. As a result, Each electric motor 2A, 2B
, the electromagnetic bass generated from 2C is unified and not amplified, and a pleasant sound is obtained.

be able to.

FIG. 2 shows a second embodiment of the invention. Components that are the same as those in the first embodiment are given the same numbers, so their explanation will be omitted. 1st
The difference from the embodiment is that the PWM inverters LA, IB, and I
The controller 12 controls the carrier wave frequency f1゜fz, fa of C to be continuously varied in a predetermined relationship with respect to time.
This is because we have established the following. The output signal of the controller 12 is P
The carrier wave signal is taken in by the carrier wave signal oscillators 5A, 5B, and 5C of the WM inverters LA, IB, and IC, and outputs a carrier wave signal based on the frequency command assigned to each one to the comparator.

When a plurality of electric motors 2A, 2B, and 2C are operated simultaneously by respective PWM inverters LA, IB, and IC, a carrier wave frequency f1. fz
By providing an oscillator controller D capable of controlling , fa, it is possible to vary the relationship among the carrier frequencies fs, fz, and fa.

Therefore, in the present invention, the carrier wave frequency fz.

The relationship between fx and fa is made to differ depending on the pitch. FIG. 3 shows the PWM calculation cycle when the carrier frequency corresponds to a chord of a certain pitch. For example, as shown in Figure 3, the carrier wave frequency corresponding to the C11 chord of the pitch is 1047 (seven), and the PW
Assuming 1 and 0 (p, u,) based on the M operation period, the controller 12 outputs 1.0°0.7937 and 0.6674 (p,
A chord can be generated by specifying the PWM operation period of (u, ). Furthermore, in this embodiment, the carrier wave frequency f
t.

It is also possible to change the relationship between fz and fa depending on the pitch, and change the combination of chords over time as shown in FIG. As a result, the discomfort caused by single chords can be eliminated, and melodies can also be played.

FIG. 6 shows a third embodiment of the present invention. The first example of this example.
The difference from the second embodiment is that in normal operation, the first.
The operation is the same as in the second embodiment, or the carrier wave frequency is varied according to the magnitude of the current of the motor 2A, and the operation is performed to report the operating state, but when an overcurrent flows through the PWM inverter IA. In this embodiment, a current detector 13A is provided to detect the current, and the carrier wave frequency f1 is changed in a specific cycle to generate an alarm sound from the electric motor 2A when there is an abnormality. Detector 1
A 3A output signal is input to the controller 12. The controller 12 varies the carrier frequency f1 so as to generate an alarm sound to the PWM inverter IA when the current detection signal exceeds a predetermined magnitude. According to this embodiment, damage to the electric motor 2A or damage to the PWM inverter IA due to overcurrent can be prevented by issuing an alarm sound.

FIG. 7 shows a fourth embodiment of the present invention. The first example of this example.
The difference from the second embodiment is that in normal operation, the first.
Operation similar to the second embodiment or.

The carrier wave frequency is varied according to the speed of the electric motor 2A to report the operating state.

In this embodiment, when an abnormality occurs when overspeed occurs in the PWM inverter IA, the carrier wave frequency fr is changed in a specific cycle to generate an alarm sound from the electric motor 2A. A speed detector 14A for detecting speed is provided, and an output signal of the speed detector 14A is input to the controller 12. The controller 12 varies the carrier wave frequency fl so as to generate an alarm sound to the PWM inverter IA when the speed detection signal exceeds a predetermined magnitude. According to this embodiment, damage to the electric motor 2A due to overspeed or abnormality in the PWM inverter IA is sounded as an alarm, thereby making it possible to prevent damage.

FIG. 8 shows a fourth embodiment of the present invention. The first example of this example.
The difference from the second embodiment is that in normal operation, the first
．． The operation is similar to that of the second embodiment, or the carrier frequency is varied according to the size of one compartment of the electric motor 2A to report the operating state of the electric motor 2A, but the PWM inverter I
In the event of an abnormality when the motor A overheats, the carrier wave frequency fz is changed at a specific cycle so that the electric motor 2A generates an alarm sound. In this embodiment, a temperature detector 15A is provided to detect the temperature of the electric motor 2A, and an output signal of the temperature detector 15A is input to the controller 12. The controller 12 varies the carrier frequency f1 so as to generate an alarm sound to the PWM inverter IA when the speed detection signal exceeds a predetermined magnitude. According to this embodiment, damage to the electric motor 2A due to overheating or abnormality in the PWM inverter IA is emitted as an alarm sound, thereby making it possible to prevent damage.

Although the embodiments in which the present invention is applied to a PWM inverter have been described above, the present invention is not limited to the control configuration of a power conversion device, and can be implemented using analog and digital control.

〔Effect of the invention〕

According to the present invention, when a plurality of electric motors are operated by respective inverters, it is possible to make the sound pleasant without amplifying the unpleasant electromagnetic waves generated by each electric motor. Additionally, during normal operation, the motor notifies you of the operating status through sound, allowing you to know if there is an abnormality. Furthermore, in the event of an abnormality, an alarm sound is generated by the electric motor to prevent damage.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the present invention in a first embodiment, Fig. 2 is a block diagram showing the present invention in a second embodiment, and Fig. 3 is a table explaining the relationship between carrier frequency and pitch code of a PWM inverter. 4 is a diagram showing a musical score explaining the combination of chords of the carrier wave frequency of the PWM inverter,
FIG. 5 is a waveform diagram illustrating the relationship between the carrier wave frequency of the PWM inverter and the harmonic current component related to the electromagnetic field generated from the motor, FIG. 6 is a configuration diagram of the third embodiment of the present invention, and FIG. 7 8 is a block diagram of a fourth embodiment of the present invention, and FIG. 8 is a block diagram of a fifth embodiment of the present invention. 1A...inverter, 2A...induction motor, 5A...oscillator, 8A...speed command circuit, 12...controller 1-roller. Muji/A Qinguchi Nekosaya ■ E, (r, B (r, 8. D B, D, F Houme Hokyo Houme

Claims (1)

[Claims] 1. In a PWM power conversion device that supplies variable voltage to a plurality of electric motors, each electric motor is provided with a PWM power conversion device, and the carrier wave frequency of PWM control of each PWM power conversion device is made different. A PWM power conversion device characterized by: 2. The PWM power conversion device according to claim 1, characterized in that the carrier wave frequency of the PWM control is varied so as to have a musical interval relationship, for example, a chord relationship. 3. A PWM power converter that supplies a variable voltage to an electric motor, comprising means for detecting or commanding the speed of the electric motor, and in relation to the speed detection or command signal, the PWM power converter
A PWM power conversion device characterized in that a carrier wave frequency for PWM control of the power conversion device is variable. 4. A PWM power converter that supplies a variable voltage to a motor, comprising means for detecting or commanding the current of the converter or the motor, and generating a carrier wave for PWM control of the PWM power converter in relation to the current detection or command signal. A PWM power converter characterized in that the frequency is variable. 5. A PWM power conversion device that supplies a variable voltage to an electric motor, comprising means for detecting or estimating the temperature of the electric motor, and
A PWM power conversion device characterized in that a carrier wave frequency for PWM control of the power conversion device is variable. 6. In claims 3 to 5, the P
The carrier wave frequency for PWM control of the WM power converter is determined by musical pitch relationships, such as C, D, E, F, G, A, C, etc.
A PWM power conversion device characterized in that the PWM power conversion device changes the sound so that it becomes a sound related to C. 7. In claims 3 to 5, the P
A PWM power conversion device characterized in that the carrier wave frequency of PWM control of the WM power conversion device is changed so as to produce an audio-like sound. 8. In claims 3 to 5, the P
A PWM power conversion device characterized in that the carrier wave frequency of PWM control of the WM power conversion device is varied to notify the presence or absence of an abnormality by sound.