JPS62203564A - Inverter apparatus - Google Patents

Abstract

PURPOSE:To always obtain a suitable output voltage without influence of the variation of an input voltage by detecting the variation in the input voltage from a power source, and switching the frequency-voltage characteristics of the output of an inverter apparatus in response to the detected result. CONSTITUTION:An input voltage from a power source 1 is reduced by a transformer 40, rectified by a diode 41 and a smoothing condenser 42, and applied to a series circuit of resistors 43, 44. The voltage across the resistor 44 is varied in response to an input voltage, the voltage across the resistor is converted by an A/D converter 45 into a digital signal to be supplied to a microcomputer 24, which detects the variation in the input voltage. The microcomputer 24 selects the frequency-voltage (V/F) characteristic stored in advance in an internal memory with the detected input voltage as a parameter, and controls an inverter waveform composite circuit 26 on the basis of the selected V/F characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inverter device used in an air conditioning layer or the like equipped with a variable capacity compressor.

<Prior art> In general, air conditioners are equipped with a refrigeration cycle mainly based on variable capacity compression, and an inverter device that supplies driving power to the variable capacity compressor, and the output frequency of the inverter device is There is also a system that obtains the optimum ability to cope with the air conditioning load by controlling the voltage and the voltage, thereby improving comfort and energy saving effect.

As an impark device used in such an air conditioner, there is one shown in FIG. 4, for example.

In Figure 4, 1 is a commercial AC power supply, and this power supply 1I11
The inverter main circuit 10 and the control section 20 are connected to the inverter main circuit 10 and the control section 20. The inverter main circuit 10 first converts the output of the power supply 1 into direct current, converts it into three-phase alternating current power of a predetermined frequency and voltage by turning on and off a plurality of switching elements, and outputs the same.

Thus, a compressor motor 30, which is a load, is connected to the output end of the inverter main circuit 10.

On the other hand, the A control unit 20 controls i! The output voltage of the power supply is stepped down by a transformer 21, rectified by a rectifier circuit consisting of a diode 22 and a smoothing capacitor 23, and taken in as an operating voltage. Further, the control section 24 has a microcomputer 24, and a frequency command device 25 and an inverter waveform synthesis circuit 26 are connected to the microcomputer 24. Furthermore, a base drive circuit 27 is connected to the inverter waveform synthesis circuit 2G.

The frequency command device 25 sends a frequency setting signal corresponding to the air conditioning load of the air conditioner body to the microcomputer 24.
It is intended to be supplied to microcomputer 24
Controls the inverter waveform synthesis circuit 2G according to the frequency setting signal from the frequency command device 25, and causes the inverter waveform synthesis circuit 26 to sequentially output a plurality of pulse signals at a predetermined period and phase. The base drive circuit 27 generates a drive signal corresponding to the pulse signal from the inverter waveform synthesis circuit 26 to each switching element of the inverter main circuit 10, such as an NPN power transistor.

(Problem to be Solved by the Invention) By the way, the output of such an inverter device is set to have a specific frequency-voltage characteristic (hereinafter referred to as V,7'F characteristic). . This is due to 1) i), in which as the output frequency increases, the voltage increases accordingly.

However, the output of the inverter device is a normal voltage! 1
It is determined that this V/F characteristic corresponds to the rectified value of
It has the disadvantage that it rises outside of the F characteristic. In other words,
When the output voltage increases, the pressure lIi! The compressor motor 30 becomes over-excited and the current flowing through the compressor motor 30 increases unnecessarily. If the current is too large, the current release function is activated and the compressor motor 30 stops operating.

Further, when the voltage of the power supply 1 fluctuates in the downward direction, the output voltage of the inverter main circuit 10 deviates from the V/F characteristic and falls. At this time, pressure mv! If the I motor 30 is in an overload operating state, a breakdown phenomenon will occur, and the compression motor 30 will also come to a stop.

This invention was made in view of the above circumstances,
The purpose is to
It is an object of the present invention to provide an inverter device that can always obtain an appropriate output voltage without being affected by this, and that enables stable operation of a load.

[Structure of the Invention] (Means for Solving the Problems) A means for detecting fluctuations in input voltage is provided, and a means for switching the frequency-voltage characteristics of the output according to the detection result is provided.

(Function) When the input voltage fluctuates, the frequency-voltage characteristics are switched accordingly to suppress fluctuations in the output voltage.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. However, in the drawings, the same parts as in FIG. 4 are given the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIG. 1, a transformer 40 is provided in the control unit 20, and a primary coil 40a of the transformer 40 is connected to the power source 1. A rectifier circuit consisting of a diode 22 and a smoothing capacitor 23 is connected to the secondary coil 401 of the transformer 40, and the operating voltage for the control unit 20 is taken from this rectifier circuit. In addition, a rectifier circuit consisting of a diode 41 and a smoothing capacitor 42 is connected to the secondary coil 40c of the transformer 4o, and the output voltage of this rectifier circuit is connected to a resistor 43.44.
applied to the series circuit. Then, A/
A D (analog/digital) converter 45 is connected, and the output of this A/D converter 45 is sent to the microcomputer 24.
supply to.

Next, the operation in the above configuration will be explained.

When the power source 1 is turned on, the control section 20 operates, and a drive signal is supplied from the base drive circuit 27 to the inverter main circuit 10. The inverter main circuit 10 first directly converts the AC input voltage from the power supply 1, and converts it into AC power of a predetermined frequency and voltage by turning on and off the power transistors according to the drive signal from the base drive circuit 27. Convert and output.

Therefore, the compressed Nada house-Yu 30 is activated and the air conditioner is turned off!
The vehicle itself begins to operate.

During this operation, the air conditioner body supplies a load signal corresponding to the air conditioning load to the frequency command device 25 of the control unit 20, and the movement of the frequency command device 25 changes the period of the drive signal to the inverter main circuit 10. Change. This results in
The output frequency and voltage of the inverter main circuit 10 change, and the compressor motor 30 operates at a rotation speed corresponding to the air conditioning load. In other words, the air conditioner main body is operated at an optimal capacity corresponding to the air conditioning load.

By the way, the input voltage from the voltage m1 is stepped down by a transformer 40, and is also passed through a diode 41 and a smoothing capacitor 4.
2 and applied to a series circuit of resistors 43 and 44. Therefore, when the input voltage fluctuates upward, the voltage across the resistor 44 increases, and conversely, when the input voltage fluctuates downward, the voltage across the resistor 44 increases.
The voltage across 4 decreases. The voltage across this resistor 44 is A
The signal is converted into a digital signal by the /D converter 45 and supplied to the microcomputer 24. Therefore, the microcomputer 24 can detect fluctuations in the input voltage.

The microcomputer 24 stores in advance V/F characteristic selection conditions as shown in FIG. 2 in its internal memory, and switches the V/F characteristic using the input voltage value as a parameter. In this case, there are three types of V/F characteristics as shown in Figure 3, and normally the V/'F characteristic of B is selected, but when the input voltage increases, the V/F characteristic of C, which has a low output voltage, is selected. Characteristics, when the input voltage fluctuates downward, V of A with high output voltage
/Select F characteristic. Then, the inverter waveform synthesis circuit 26 is controlled based on the selected V and /F characteristics.

In addition, in the selection condition of the V/F characteristic, a differential of several volts is provided for the set value with respect to the change in the input voltage, so that hunting does not occur in the selection.

In this way, when the input voltage increases and fluctuates, the V/F of C
By selecting the characteristics, it is possible to suppress an increase in the output voltage of the inverter main circuit 10.

Therefore, it is possible to prevent an increase in the current flowing through the compressor motor 30, and it is possible to avoid unnecessary shutdown of the compressor motor 30 due to the current release function.

Furthermore, when the input voltage fluctuates downward, by selecting the V/F characteristic of A, it is possible to suppress the decrease in the output voltage of the inverter main circuit 10. Therefore, pressure! Unnecessary operation stoppage due to breakdown of the tl i motor 30 can be avoided.

In other words, it is possible to always obtain an appropriate output voltage without being affected by fluctuations in input voltage, and the compression U1 motor 3
0 can be operated efficiently and stably. Moreover, the secondary coil 40 for capturing the operating voltage detects fluctuations in the input voltage.
b) are conducted through another secondary coil 40c, so even if load fluctuations occur in the control unit 20 itself,
Accurate detection can be performed without being influenced by this.

In the above embodiment, a case has been described in which there are three types of V/F characteristics that can be selected, but there is no limit to the number of types, and the number may be changed as appropriate depending on the situation. In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without changing the gist.

[Effects of the Invention] As described above, according to the present invention, it is possible to always obtain an appropriate output voltage without being affected by variations in input voltage, and stable operation of the load is possible. An inverter gffff can be provided.・

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a control circuit in one embodiment of the present invention, FIG. 2 is a diagram showing V/F characteristic selection conditions in the same embodiment, and FIG. 3 is a diagram showing the V/F characteristics in the same embodiment. FIG. 4 is a diagram showing the configuration of a control circuit in a conventional inverter device. 10... Inverter main circuit, 20... Control section, 24
...Microcomputer, 30...Compressor motor. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (1)

[Claims] In an inverter device that once converts an AC input voltage into DC, converts it into AC power of a predetermined frequency and voltage, and outputs the same, means for detecting fluctuations in the AC input voltage;
An inverter device comprising means for switching the frequency-voltage characteristics of the output according to the detection result.