Can the fixed frequency screw compressor adjust the frequency?

Fixed frequency screw compressorUnable to adjust frequency directly, because its core drive motor is designed for fixed frequency and its operating frequency is fixed. But it can be passedfrequency conversion transformationIndirectly realize frequency adjustment. The following is a detailed technical analysis:

1. Working principle of fixed frequency screw compressor

1. mechanical structure
   A pair of intermeshing screws (male rotor and female rotor) rotate in the casing to form periodic volume changes to complete gas suction, compression and discharge.

2. operating characteristics

   • Fixed frequency motor drive: The motor speed is fixed, usually power frequency (50 Hz/60 Hz), and the output pressure is directly related to the speed.
   • Capacity adjustment limit: The air volume (unloading/loading) needs to be adjusted through the opening of the intake valve, which belongs to “staged adjustment” and has low energy efficiency.

2. Why cannot the fixed frequency screw compressor directly adjust the frequency

1. hardware limitations
   The fixed frequency motor has no frequency conversion module and cannot change the power supply frequency. The speed is determined by the power grid frequency.

2. control logic
   Traditional fixed-frequency machines control start-stop or loading/unloading through pressure switches, and no frequency conversion algorithm supports stepless speed regulation.

3. Feasibility analysis of frequency conversion transformation

If you need to adjust the frequency, you need to adjust the fixed frequency screw compressor.frequency conversion transformation, the core plan is as follows:

1. transformation content
   • Add frequency converter: Replace the original power frequency power supply with a variable frequency power supply to control the motor speed.
   • Upgrade control system: Add PID control algorithm to adjust the frequency in real time based on the pressure signal.
   • Retain the original protection mechanism: Such as high temperature protection, overcurrent protection, etc., to ensure safety.
2. technical advantages
   • stepless speed regulation: Adjust the output pressure as needed (such as arbitrarily set within the range of 0.5~1.3MPa).
   • energy saving: Avoid frequent loading/unloading, and low-frequency operation when unloaded reduces energy consumption by about 30%.
   • prolong life: Reduce start-stop impact and reduce mechanical wear.
3. limitations
   • High cost of renovation: It requires evaluation by a professional team. The inverter + control upgrade cost is about tens of thousands of yuan.
   • maintenance complexity: Frequency converter parameters need to be calibrated regularly to prevent harmonic interference.
   • low frequency limit: Too low a frequency may lead to insufficient lubrication (recommended lower limit ≥35Hz).

4. Suggestion of alternative solutions

If frequency conversion transformation is not feasible, the following alternatives can be considered:

1. Multiple machines in parallel
   Adjust the total gas volume by starting and stopping multiple fixed-frequency machines, which is suitable for scenarios with large fluctuations in gas consumption.

2. waste heat recovery
   Use compressor waste heat (oil temperature 80~100℃) to heat or preheat process water to improve overall energy efficiency.

3. Direct purchase of inverter screw compressors
   The new equipment has a built-in frequency conversion system for better long-term costs (especially under continuous operating conditions).

conclusion: The fixed-frequency screw compressor itself cannot adjust the frequency, but it can achieve stepless speed regulation through frequency conversion. It is necessary to comprehensively evaluate renovation costs, energy efficiency improvements and long-term maintenance needs to select the best solution. For newly purchased equipment, it is recommended to directly purchase inverter models to match dynamic gas demand.