Application boundary of variable frequency refrigeration compressor | Analysis of variable frequency advantages, cost upper limit and working condition adaptation
Variable frequency compressors rely on frequency converters to change the motor speed, achieving continuous and stepless cooling capacity regulation, suitable for small and medium-sized constant temperature cold storage with frequent load fluctuations and high temperature control accuracy requirements.
The frequency conversion scheme has outstanding energy-saving advantages in the 20%~80% load range. When operating at low loads below 20%, the proportion of losses in the frequency converter itself increases, and the overall energy efficiency decreases by 8%~12%.
The Xiteluo variable frequency semi enclosed machine is mainly used for high-end fresh flower preservation and precision constant temperature laboratories. Ordinary large capacity meat freezers use fixed frequency piston units, which have a higher input-output ratio.
The frequency converter has strict requirements for the computer room environment. In aquatic workshops with high dust concentration and humidity greater than 85%, the corrosion rate of circuit boards is accelerated, and the average life of the frequency converter is shortened by 40%.
The insulation level of variable frequency compressor motors generally requires F level or above. Under high-frequency operation, the temperature rise is higher, the cooling air volume is insufficient, and the winding overheating protection will be frequently triggered.
The cost of exporting overseas variable frequency units is about 35% higher than that of ordinary fixed frequency units, and it requires a matching stable voltage power supply. In areas with unstable voltage, the probability of frequency converter failure increases significantly.
Many buyers blindly choose variable frequency models, believing that all cold storage facilities are energy-saving, stable load, and operate at full load for a long time. Variable frequency cold storage facilities have almost no energy-saving benefits.
The difficulty of controlling the refrigerant return oil of variable frequency units is higher than that of fixed frequency units. During low-speed operation, the flow rate of the return pipe decreases, and the flow rate is below 0.6m/s. The frozen oil is trapped in the evaporator, causing heat transfer attenuation.
The parameter debugging of the frequency converter needs to match the compressor curve. Improper settings of the highest frequency, lowest operating frequency, and acceleration/deceleration time can lead to chain failures such as overload and liquid return.
When refrigeration unit factories provide foreign trade quotations, they will distinguish between standard version fixed frequency and high-end variable frequency schemes, and provide customers with a clear comparison of three indicators: initial investment, annual electricity cost, and difficulty of maintenance spare parts.
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FAQ
Which load range of variable frequency compressor has the best energy-saving effect? The energy-saving advantage is obvious in the 20% to 80% load range.
2. Energy efficiency changes of variable frequency units with low loads below 20%? The overall energy efficiency has actually decreased by 8% to 12%.
3. Does the high humidity dust workshop affect the frequency converter? The lifespan of the frequency converter is reduced by approximately 40%.
What is the minimum flow rate requirement for the return oil of the variable frequency unit? The flow velocity of the return pipe should not be less than 0.6m/s as much as possible.
How much higher is the procurement cost of variable frequency units compared to fixed frequency units? The overall cost has increased by about 35%.
6. Is variable frequency suitable for full load stable cold storage? Not recommended, the energy-saving benefits are very low and the cost is higher.
What is the minimum standard for insulation level of variable frequency motors? It is recommended that the insulation level should not be lower than Class F.
