1.1 Frequency and Refrigeration Capacity Equation The principle of the inverter compressor is to adjust the displacement of the compressor per unit time by adjusting the speed of the compressor, so as to achieve the purpose of adjusting the cooling capacity. For AC variable frequency compressors, the relationship between speed and frequency is as follows: where n - speed (r / min); f - power frequency (Hz); s - motor slip rate; P - motor pole pairs The power consumption of the compressor has the following relationship: λ - leakage coefficient; P s - suction pressure; V k - suction volume; ni - variable index; εi - pressure ratio (exhaust / suction) Gas); δ0 - relative pressure loss coefficient; Z s, Z d - actual gas compressibility coefficient and thus the air conditioner refrigeration capacity can be expressed as follows: EER - average energy efficiency ratio (EER (energy efficiency ratio) - Energy efficiency ratio under rated conditions) Therefore, we obtain a mathematical relationship between cooling capacity and compressor frequency: the value of EER is a parameter that is difficult to calculate accurately, and it is in heat exchange efficiency with the climatic environment and refrigeration cycle in which the air conditioner is located. related. In general, EER can be considered as a relatively stable value.
It is the relationship between theoretical cooling capacity and frequency and the relationship between actual cooling capacity and frequency.
There is a gap between the actual cooling capacity and the theoretical cooling capacity. The main reason is that the value of the EER of the air conditioner changes, the value of EER is higher in the low frequency stage, and the value of EER is lower in the high frequency stage.
1.2 Working principle is to use the indoor temperature sensor to sense the difference between the indoor temperature and the set temperature, and then control the AC frequency delivered to the compressor, thereby controlling the speed of the compressor, so that the power consumption and cooling capacity of the air conditioner vary with the temperature of the environment. And change.
1.3 The operation process is that the indoor sensor transmits the indoor temperature operation status to the outdoor part, the outdoor part analyzes the information transmitted, calculates the time difference between the temperature difference and the room temperature, and then calculates the frequency of the compressor motor operation through the calculation of the CPU. In this way, when the air conditioner starts running, if the room temperature and the set value are different, the high-frequency operation is used to achieve rapid cooling. If the difference between the indoor temperature and the set value is small, the running frequency of the motor is small, and the cooling capacity is also relatively small. Small, so that the cooling capacity is consistent with the load.
2.1 Characteristics of inverter air conditioner 2.1.1 Rapid cooling, good comfort When starting operation, the unit starts low frequency and low speed, and quickly turns into high frequency and high speed operation. Its speed can reach 2~3 times of normal speed, so it is faster than fixed speed. The air conditioner can reach the set temperature faster, generally only 3 to 5 minutes after cooling down to 10 °C. When the room temperature is close to the set temperature, adjusting the rotation speed of the compressor to adjust the room temperature without stopping the compressor operation can create a comfortable environment with little temperature change.
2.1.2 Ultra-low temperature heating, fast defrost Inverter air conditioner automatically changes the compressor speed according to the change of outdoor temperature. When the outdoor temperature is low, the operating frequency is increased to improve the heating capacity. At -12 °C, the output can reach the rated value of 70. About %, about twice as high as the average air conditioner. In the case of low temperature, the general outdoor unit of the air conditioner needs to be shut down for 5 to 15 minutes. Inverter air conditioner defrosting is the use of warm defrosting of the compressor exhaust to achieve uninterrupted heating and rapid defrosting.
2.1.3 Energy-saving and energy-saving The inverter air conditioner adopts fuzzy control technology to adjust the cooling (heat) capacity, and the compressor does not stop and reduces the loss caused by frequent start and stop. The energy-saving effect is obvious, saving 20% ​​to 30% compared with the ordinary air conditioner. The inverter air conditioner has strong voltage adaptability and the working voltage is between 187 and 242V, which is suitable for use in areas where the grid voltage is unstable.
2.1.4 Low-noise operation, reasonable dehumidification function The inverter air conditioner adopts frequency conversion double-rotor compressor and variable-frequency DC motor, so that the compressor can operate in a balanced manner from low speed to high speed, and the long-term low-frequency operation makes the outdoor unit run more smoothly. . The indoor unit also has no frequent start and stop sounds, achieving low noise operation of the whole machine. The dehumidification unit is only equivalent to 1/3 frequency operation during cooling, and the dehumidification effect is achieved with a small input power.
2.2 Classification of inverter air conditioners The type of inverter air conditioners is mainly determined by the frequency conversion method and main components. Basically, it can be divided into three types.
The first type of inverter air conditioner adopts AC frequency conversion, the refrigerant flow regulation mode adopts a capillary tube, and the compressor adopts a single rotor AC frequency conversion compressor.
The second type of inverter air conditioners also use AC frequency conversion. The difference is that the compressor uses a double-rotor AC inverter compressor. The refrigerant flow regulation reduces the power consumption, and then quickly shifts from the low frequency state to the high frequency state. valve.
The third type is a DC inverter air conditioner, which uses a DC inverter compressor and a DC fan motor. The adjustment method is an electronic expansion valve.
This paper introduces the working principle, characteristics and classification of inverter air conditioners. However, the energy-saving features of the inverter air conditioner mentioned here are proposed under the premise of continuous operation of the air conditioner, which saves the starting current when the fixed-speed air conditioner is frequently started, and cannot be asserted for the discontinuous operation.
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