In inverter air conditioners, the rotational speed of the compressor can be adjusted according to actual needs. Generally speaking, when the indoor temperature differs significantly from the set temperature, inverter air conditioners will operate at a higher frequency (i.e., fast speed) to quickly reach the set temperature. When approaching the set temperature, the frequency will be reduced and the operating speed will be slowed down. The common reasons for the frequency-limited operation of inverter air conditioners are mainly as follows:
Evaporator high and low temperature frequency limit: When the inverter air conditioner detects that the evaporator temperature is too low, it will limit the operating frequency of the compressor to prevent frost or ice formation on the surface of the evaporator and protect the compressor from damage such as liquid return.
High-temperature frequency limiting of condenser: If the outdoor ambient temperature is too high or the condenser has poor heat dissipation (such as dust accumulation), it will cause the condensing pressure to rise, which in turn will increase the exhaust temperature of the compressor and energy consumption. At this point, the control system will automatically reduce the compressor frequency, decrease the refrigerant flow rate, and keep the condensing temperature within a safe range.
When the temperature of the gas discharged by the compressor exceeds the set value, it may indicate problems such as insufficient lubrication and improper refrigerant charging. Long-term operation may damage the compressor. Therefore, when the system detects an abnormal increase in exhaust temperature, it will take measures to reduce the frequency to cool down and attempt to restore the normal state.
Current frequency limiting: In some cases, if the input power supply is unstable or the grid voltage fluctuates greatly, it may cause difficulties in starting the motor or a sudden increase in load during operation, resulting in the current passing through the motor exceeding its rated value. To prevent the motor from burning out, the control system will automatically adjust the output power upon detecting abnormal current, that is, reduce the speed of the compressor.
Voltage frequency limiting: Unstable power supply voltage has a significant impact on electrical equipment, especially for inverter air conditioners that have high requirements for precise control. When the voltage provided by the power grid is lower or higher than the normal range, it not only affects the normal working performance of the system, but may also damage electronic components. Therefore, when encountering unsuitable power supply conditions, the air conditioning system will automatically adjust the working frequency of the compressor to adapt to the current power situation.
Abnormalities in the indoor/outdoor electronic control system, such as short circuits, component damage or software errors, may cause the system to misjudge the current status and take frequency limiting measures to avoid potential risks. If there is a problem with the power supply in the outdoor unit or the controller fails, it will affect the working condition of key equipment such as the compressor and fan motor.
Temperature-sensing device failure: Temperature-sensing devices (temperature sensors) are used to monitor the actual temperature of evaporators, condensers or other parts and feed the information back to the control system. If the temperature-sensing device malfunctions, even if the actual ambient temperature is normal, incorrect temperature readings may mislead the control system into believing that the evaporator is too cold, thereby triggering the frequency-limiting protection mechanism. The solution is usually to replace the faulty temperature sensing device and recalibrate the entire temperature control circuit.
Abnormal pressure in the refrigeration system: The refrigerant needs to maintain an appropriate pressure level during the circulation process. Both too high and too low pressure levels will affect the operation of the system. The pressure sensor can monitor this parameter in real time. Once an abnormality is detected, to prevent damage to the compressor, the system will automatically reduce the working frequency. Possible causes include refrigerant leakage, improper charging or pipeline blockage, etc.
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