JPS61177172A - Pwm inverter controller - Google Patents

Abstract

PURPOSE:To suppress the generations of a vibration and a noise by providing oscillating means for outputting carrier of different frequency and selecting means for selecting one carrier from them. CONSTITUTION:3-phase power sources are converted by rectifier into DC, which is converted to PWM output by an inverter of bridge configuration, and supplied to an induction motor. In this case, a carrier controller 10', a carrier selector 13 for sorting the outputs and a selector 14 are provided in the controller to generate a triangular wave signal TR'. The carrier outputs F1-F3 of 3 triangular wave signals of different frequencies are output from the controller 10', selection signals SL1-SL3 are applied from the selector 13 to the selector 14 to select the outputs F1-F3. Thus, when a machine structure including a motor is resonated, a signal which does not cause a resonance out of three types is selected to apply a triangular wave signal TW'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a pulse width modulated (PWM) output.
Inverter, especially an asynchronous W that provides a drive signal to the inverter circuit by comparing a fixed carrier wave signal and a sine wave signal
The present invention relates to improvements in control devices for PWM inverters.

[Conventional technology and problems]

Conventionally, the PWM inverters shown in FIGS. 3 and 4 are known as PWM inverters, particularly voltage-type valve synchronized PW'M inverters.

Figure 3 shows the main part configuration of a general main circuit of a PWM inverter, where l is a three-phase power supply, 2 is a rectifier circuit that converts the three-phase power supply 1 to DC, 3 is a filter capacitor, and 4 is, for example, a self-contained An inverter circuit 5 is configured as a bridge using a switching element 8, which is an arc-extinguishing element, and a diode D, which is connected in antiparallel to the switching element SK.5 is an induction motor. Here, the inverter circuit 4 has a switching element 8
This is an example in which a transistor is used as a base drive signal 8 from a control section as shown in FIG.
BD is obtained and the PWM output is supplied to the induction motor 5. Note that the main circuit section as described above is commonly used, so a description thereof will be omitted.

FIG. 4 shows the main part configuration of a conventional PWM inverter control device, in which 6 is a frequency setter, 7 is a voltage frequency converter for signal conversion, and 8 is an output voltage ratio to the output frequency of the inverter circuit 4. 9 is a sine wave controller that generates a sine wave signal SW corresponding to the output voltage from the voltage frequency converter 7 output and the voltage controller 8 output, that is, the input values of the frequency command and voltage command; A carrier wave controller that generates a triangular wave signal TW of a constant frequency with positive/negative symmetry that is a PWM carrier frequency, 11 a comparator that compares the sine wave signal SW and the triangular wave signal TW to generate a PWM mode drive signal DW, 12 a drive signal This is a driver that obtains DW and sends a base drive signal SBD to the switching element S of the inverter circuit 4 shown in FIG. Note that the control operation and PWM control of the conventional control unit are well known, so their explanation will be omitted.

However, in conventional asynchronous PWM inverters of this type, since the fixed carrier wave output and the sine wave output are compared as described above, the inverter circuit section supplies a pseudo sine wave output to the electric motor, so the inverter output The current, that is, the motor current, contains a pulsating component caused by the chipping, that is, a frequency component that is the same as the carrier wave output signal, and the motor generates vibration and noise due to the chipping.

On the other hand, mechanical structures including electric motors have resonance points,
When the natural frequency of the mechanical structure and the signal frequency of the carrier wave are close to each other, resonance occurs and vibration and noise due to chipping increase.

In particular, in the case of an asynchronous PWM inverter, resonance occurs over a wide range of output frequencies. Furthermore, since general-purpose electric motors are usually put into practical use, a problem arises in that the mechanical structure including the electric motor resonates after actually being combined with the electric motor.

[Means for solving problems and their effects]

The present invention has been made with attention to the above-mentioned points, and includes an oscillation means for outputting carrier waves of different frequencies and a selection means for selecting one carrier wave from the oscillation means, thereby preventing mechanical resonance of the motor from occurring. By using a method that allows carrier selection, the fixed carrier signal frequency can be oscillated and
This provides an exceptional device that can select the most suitable carrier wave depending on the situation, such as noise. Hereinafter, the present invention will be explained based on the drawings.

〔Example〕

FIG. 1 is a partial configuration diagram showing the main configuration of an embodiment of the present invention, in which 10' is a carrier wave controller, and 13 is a carrier wave controller 10'.
14 is a selection circuit, TW' is a fourth carrier wave selector that uses a packaged DIP switch to select the output, etc.
This is a triangular wave signal sent as one signal input of the comparator 11 in the control section of the PWM inverter as shown in the figure. Here, the triangular wave signal TW' can be used in the same way as the triangular wave signal TW shown in FIG. 4, and therefore the part shown in FIG. It constitutes.

Here, the carrier wave controller 10' has three carrier wave oscillators 08
Cs.

The main components are 08C2 and 08Cs, and each generates carrier waves of different frequencies.

Thus, in FIG. 1, the carrier wave output Fl of three triangular wave signals having different frequencies is output from the carrier wave controller 10'.

Fg, Fs are generated by the selection circuit 14, and selection signals 8Ls, SLz, 8Ls are generated by the carrier selector 13.
An appropriately selected selection signal output is given to the selection circuit 14.

Here, the selection circuit 14 may be a multiplexer, for example, and generates one triangular wave signal TW' selected from the carrier wave outputs F1m F2 t Fm, and sends the signal to the comparator section of the control section as described above.

Here, the state of the carrier wave output Fs*F2*Fs is illustrated as shown in FIG.

FIG. 2 shows the frequency relationship of the carrier wave output, and the carrier wave outputs FB, F2, and Fs are shown as characteristic lines of three frequencies.

That is, in the case of a transistor inverter, for example, the carrier wave for PWM control is generally selected from a sufficiently high value with respect to the output frequency, and is generally l kHz, and three different frequencies around l kHz are selected, for example, 900 and 950.
, 1000Hz. In the asynchronous system, it goes without saying that the carrier frequency is constant over the entire range with respect to the imperter output frequency.

Furthermore, in FIG. 1, by using the carrier wave selector 13, when the mechanical structure including the electric motor resonates, the carrier wave selector 13 is used.
Type of carrier wave output F1. The optimal signal that does not cause mechanical resonance is selected from Fx and Fs to generate the triangular wave signal TW.
' is given.

〔Effect of the invention〕

As explained above, according to the present invention, in a motor drive device using a PWM inverter, the natural frequency of the mechanical structure does not exist as a continuous value, but a plurality of carrier signal frequencies are set at appropriate intervals. Since the PWM inverter and the mechanical structure are provided separately, it is possible to avoid resonance points, and it is possible to provide a device with a simple configuration that can suppress the generation of vibration and noise due to most resonances of the combination of the PWM inverter and the mechanical structure. Furthermore, it is extremely useful in that it is possible to easily select the carrier wave output according to the situation on the spot when combined with a 2wM inverter, and that it can be easily selected using a selection switch on the control board.

[Brief explanation of the drawing]

FIG. 1 is a partial configuration diagram showing the main configuration of an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the carrier wave frequency of the carrier wave output and the inverter output frequency, and FIG. 3 is a diagram showing the general main structure of the PWM inverter. FIG. 4 is a diagram showing the configuration of the main parts of the circuit section, and FIG. 4 is a diagram showing the structure of the main parts of a conventional PWM inverter control device. 4... Inverter circuit, 9... Sine wave controller, 10.10'... Carrier wave controller, 11
...Comparator, 12...Driver, 13.
...Carrier selector, 14...Selection circuit,
TW, TW'-...Triangular wave signal, FxtFz, F
s...Carrier wave output.

Claims (1)

[Claims] A drive signal for an inverter circuit is generated by comparing the carrier wave output of a constant triangular wave signal and a sine wave signal output, and a pseudo sine wave output is supplied from the inverter circuit.
The WM inverter control device is characterized by being provided with carrier wave oscillation means for respectively providing carrier wave outputs of different frequencies, and carrier wave selection means capable of selecting one carrier wave that does not cause mechanical resonance of the motor from the output of the oscillation means. PWM inverter control device.