JPS6240091A - Air conditioner - Google Patents

Abstract

PURPOSE:To improve the efficiency of a room air conditioner by controlling a voltage control section so that an electric compressor can be operated at a maximum efficiency point at all times to the variation of an input to an AC power supply by an output signal from a current sensor. CONSTITUTION:In a controller 4, an electric compressor 5 is controlled by a micro-computer 12 on the basis of a temperature input signal from a room temperature setter 10 and a room temperature detector 11. DC voltage is adjusted by a voltage control section 15 at all times on the basis of an input signal from a current sensor 14 even to the variation of an input to a power supply Accordingly, output voltage from an inverter 3 is kept constant, and the relationship of the ratio V/Hz (V/Hz is constant) of voltage V to the fre quency Hz of AC voltage inputted can be maintained, thus operating the electric compressor 5 at a maximum efficiency point at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an air conditioner such as a roomier conditioner.

<Prior art> Conventional variable capacity electric compressors for inverters achieve maximum motor efficiency when the ratio of the input voltage input to the electric compressor and the input frequency Hz is constant (V/Hz = constant). Therefore, in an air conditioner equipped with an inverter, an output voltage that satisfies V/Hz = constant is applied to the electric compressor according to each operating frequency. However, this output voltage output by the inverter is based on the DC voltage obtained by rectifying the AC power supply.
Since it is uniquely determined for each operating frequency, if the reference DC voltage changes due to input fluctuations of the AC power supply, the inverter output voltage will inevitably change, which is the highest point of motor efficiency. Even though the output voltage was being output so as to operate at There was a drawback that the performance was not fully utilized.

<Purpose> In view of the above, the present invention aims to provide an air conditioner such as a roomier conditioner with high efficiency by constantly operating an electric compressor at the highest efficiency point.

<Example> Hereinafter, an example of the present invention will be described in detail based on FIGS. 1 and 2. In FIG. 1, a converter 1 rectifies a single-phase or three-phase AC power source 2 into DC and outputs it to an inverter 3. In the inverter 3, a control device 4 determines the DC voltage rectified by the converter 1. It converts into AC having the output frequency and output voltage and applies it to the electric compressor 5 to control its drive.

An indoor heat exchanger 6 is connected to the electric compressor 5 through a piping A, and an outdoor heat exchanger 8 is similarly connected to the indoor heat exchanger 6 via a pressure reducer 7. The electric compressor 5 is connected to the heat medium compressor cycle 9.
has been established.

In the control device 4, the operating frequency of the electric compressor R5 is determined by a microcomputer (hereinafter referred to as microcomputer) 12 based on temperature signals from a room temperature setting device 10 and a room temperature detector 11 such as a thermistor. Said electric compression I! 5, the motor efficiency is highest when the ratio of the frequency Hz of the input AC voltage to the voltage V is constant (■/Hz = constant), so each determined operating frequency Hz is V/H.
The output voltage is uniquely determined so as to satisfy the relationship z=fixed.

The microcomputer 12 outputs the frequency and voltage data determined in this manner to the inverter driving section 13, the inverter 3 is driven, and the DC voltage obtained by the converter I is converted into a pseudo AC voltage.

Here, if the DC voltage changes due to input fluctuations of the AC power source 2, the output voltage of the inverter 3 will also change, the above-mentioned relationship (V/Hz=constant) will collapse, and the motor efficiency will decrease. Therefore, a current sensor 14 is provided, and a voltage control section is provided that varies the DC voltage from the converter and outputs it to the inverter 3. The converter has a function of controlling the voltage control section 15 so that it can always operate at the highest efficiency point in response to input fluctuations in the power supply, and the converter has a rectifier circuit 16 as shown in FIG.
and a capacitor 17 for smoothing the DC voltage rectified by the circuit 16. The voltage control unit 15 also includes a chopper transistor 19 for chopping the DC voltage from the rectifier circuit 16, a diode 20 for protecting the transistor 19, and a coil 21 for converting the chopped DC voltage into a smoother one. and capacitor 22
and a driving section 18 having one of the transistors.

This control method will be explained below based on FIG. 2.

The input from the AC power supply 1 is converted into a DC voltage by a rectifier circuit 16 and a smoothing capacitor 17, and the DC voltage is input to the inverter 3. If the AC power supply 1 fluctuates, the DC voltage will fluctuate, and the output voltage of the inverter 3 will also fluctuate. Due to this variation in output voltage, the line current flowing through the electric compression TFI5 naturally changes, so the current sensor +-1A
Enter 719 numbers. Since the output voltage is uniquely determined by the operating frequency in the microcomputer 12, a command is issued to the chopper transistor drive section 18 based on the amount of change detected from the current sensor 14, and the 0N10FF ratio (duty) of the chopper transistor 19 is determined. By changing the DC voltage, the DC voltage can be changed and adjusted. Then, the output voltage from the inverter 3 is output with a constant ratio (optimal value) to the operating frequency.

In this way, the DC voltage applied to the voltage control unit 15 is adjusted based on the input signal from the current sensor 14 so that the line current flowing to the electric compressor 5 is always constant, and as a result, the above-mentioned The output voltage of inverter 3 becomes constant,
The aforementioned V/Hz=constant relationship can be maintained, and the electric compressor 5 can always be operated at the highest efficiency point.

It goes without saying that many modifications and changes can be made to the above embodiments within the scope of this book 1.

Effect> As is clear from the above description, the present invention includes a converter that rectifies and smoothes input from an AC power source, and a converter that inputs DC voltage from the converter to control the output frequency and output voltage to an electric compressor. A current sensor is provided that includes an inverter and a control device that controls the inverter, and that detects changes in the line current flowing through the electric compressor, and that varies the DC voltage from the converter and outputs the voltage to the inverter. A control unit is provided, and the control unit has a function of controlling the voltage control unit using the output signal of the current sensor so that the electric compressor can always operate at the highest efficiency point with respect to input fluctuations of the AC power source. The present invention relates to an air conditioner characterized by:

Therefore, according to the present invention, the voltage control section allows the electric compressor to always operate at the highest efficiency point in response to input fluctuations in the AC power source, so that there is an excellent effect that an air conditioner can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an air conditioner showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a voltage control section. 2: AC power supply, 3: Inverter, 4: Control device, 5: Electric compressor, 14: Current sensor, 15: Voltage control section, 1
7, 22: Capacitor, 19: Transistor.

Claims (1)

[Claims] A converter that rectifies and smoothes input from an AC power supply, an inverter that inputs DC voltage from the converter to control the output frequency and output voltage to the electric compressor, and a control device that controls the inverter, A current sensor is installed to detect changes in the line current flowing through the electric compressor.
A voltage control unit is provided that varies the DC voltage from the converter and outputs it to the inverter, and the control device controls the electric compressor to always maintain the highest efficiency point with respect to input fluctuations of the AC power source based on the output signal of the current sensor. An air conditioner characterized in that it has a function of controlling the voltage control section so that the air conditioner can be operated at