JPS58108977A - Starting current reducing method for air conditioner - Google Patents

Abstract

PURPOSE:To reduce the starting current of an air conditioner by reducing the starting frequency at the starting time and decreasing the ratio of the starting fundamental wave voltage to be applied to the starting frequency. CONSTITUTION:An inverter 3 outputs an alternating voltage which has a starting frequency lower than the frequency at the ordinarily operating time and a starting fundamental wave voltage to be applied and determined by the ratio of the starting fundamental wave voltage to be applied to the starting frequency smaller than the ratio of the fundamental wave voltage to the frequency at the ordinarily operating time. After the start of a compressor 4 is completed, the inverter 3 outputs an alternating voltage which has a voltage determined by the ratio of the fundamental wave voltage to the frequency at the ordinarily operating time. In this manner, the starting current of the compressor can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing the starting current of an air conditioner, and an object of the present invention is to improve the operating efficiency of the air conditioner by reducing the starting current, which is larger than the line current during continuous operation. do.

When an air conditioner compressor is directly connected to a power source, the starting current (
Usually 80 to 40 A) flows (see solid line in Figure 8).

In addition, in air conditioners that can control the refrigeration capacity by changing the power frequency applied to the compressor using an inverter and controlling the rotation speed of the compressor, Fundamental voltage ratio V/
By keeping the Hz constant, the most efficient operation can be achieved.

Therefore, by lowering the power frequency applied to the compressor using an inverter and maintaining the 11'iJ recording ratio V/Hz at a predetermined value, the starting current can be significantly reduced (8th (See the two-dot dashed line in the figure).

However, if the starting current is to be sufficiently reduced only by lowering the power supply frequency, the range in which the power supply frequency can be varied by the inverter must be widened.

The present invention makes it possible to sufficiently reduce the starting current without widening the variable range of the power supply frequency by the inverter, and will be described in detail below with reference to the accompanying drawings showing embodiments.

Figure 1 is a block diagram of an air conditioner that implements the method of the present invention, in which a single-phase or three-phase alternating current power supply (1) is rectified by a converter (2), and the rectified output of the converter (2) is The inverter (3) converts it into an alternating voltage with variable frequency and variable voltage, and the converted alternating voltage is applied to the compressor (4). The compressor (4) is equipped with an indoor heat exchanger (
5), a pressure reducer (6) and an outdoor heat exchanger (7) are connected in this order to constitute a refrigerant compression cycle.

When the compressor (4) is in normal operation, the inverter (3) maintains a ratio V between the output fundamental wave voltage and the frequency.
/I=lz is maintained at a predetermined value that allows the compressor (4) to operate most efficiently, and when starting the compressor (4), the starting frequency is lowered and the ratio of the starting applied fundamental wave voltage to the starting frequency Vs /llz is configured to be smaller than the ratio V/Hz. In this case, the application time of the starting applied fundamental wave voltage is set within the time (usually within several seconds) during which the load torque is less than the maximum output torque when the starting applied fundamental wave voltage is applied.

The operation of the air conditioner of the present invention having the above configuration is as follows.

When starting the compressor (4), the inverter (3) applies a starting fundamental wave determined by a ratio Vs/Hs that is lower than the frequency during normal operation and is also smaller than V/liz during normal operation. Outputs an alternating voltage with voltage.

Then, by applying the alternating voltage to the compressor (4) for a predetermined period of time, the compressor (4) can be started.

After completing the startup of the compressor (4), the inverter (3)
The compressor (4) can be operated normally by outputting an alternating voltage having a frequency determined by the ratio V/Hz and an applied fundamental wave voltage.

Therefore, when starting the compressor (4), the starting frequency is lowered, and the ratio of the starting fundamental wave voltage to the starting frequency is V.
By reducing B7ki z, the applied voltage can be lowered, and therefore the starting current of the compressor (4) can be sufficiently reduced (see the broken line in FIG. 8).

For example, three-phase rated output cuff 50W, winding 60Elz=18
When starting the compressor of 3■, if you apply three-phase alternating power directly without using an inverter, the starting frequency is 5.
9 Hz, applied fundamental wave voltage 138■, ratio V/llz
2, 2. The starting current is 80 A, and if the starting frequency is lowered using an inverter while keeping the ratio V/llz constant, the starting frequency is 39 Hz, the applied fundamental wave voltage is 70 V, and the ratio V/llz is lowered.
11 Z 2.8, the starting current is 18 A, and if the starting frequency is lowered using an inverter and the ratio V/)lz is made smaller, the starting frequency is 39 Hz, the applied fundamental wave voltage is 40 V, the ratio V/Hz IJ, starting The current was 9A.

As described above, in the present invention, when starting the compressor, the starting frequency is lowered and the ratio V/llz f is made smaller, so the starting current can be made sufficiently small, and the switching elements of the inverter can be reduced. The capacitance can be reduced, and the air conditioner as a whole can be made less expensive, and the switching loss of the elements can be reduced, resulting in higher efficiency.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an air conditioner implementing the method of the present invention, Figure 2 is a diagram showing the relationship between frequency and applied fundamental voltage at startup and during normal operation, and Figure 8 is the time of the starting current. , 8... Inverter 4... Compressor No. 1
Figure 2 Figure 3

Claims (1)

[Claims] 1. It has a refrigerant compression cycle that sequentially connects an electric compressor, an indoor heat exchanger, a pressure reducer, and an outdoor heat exchanger,
In an air conditioner equipped with a control unit that controls the three-phase alternating voltage and frequency applied to the electric compressor, when starting the electric compressor, the ratio of the starting applied fundamental voltage to the starting frequency is set to the fundamental wave during normal operation. The ratio between voltage and frequency is also small, and the stage where the electric compressor starts controls the three-phase alternating power supply applied to the electric compressor according to the ratio between the fundamental voltage and frequency during normal operation. A method for reducing starting current in air conditioners.