Working principle of frequency converter in air compressor
We found that the speed of an air compressor motor is directly proportional to the actual power consumption of the air compressor. Therefore, reducing the actual power consumption of the air compressor requires reducing the motor speed. The use of a frequency converter (VFD) in an air compressor system allows for precise coordination between electrical control and VFD control. This enables real-time control of the motor speed (output power) without altering the motor torque (i.e., its load-driving capacity). By changing the compressor speed, it responds to changes in system pressure and maintains a stable system pressure (setpoint), thus achieving on-demand output of high-quality compressed air. When the system's air consumption decreases, the compressor supplies more compressed air than the system consumes, causing the compressor to reduce its speed and output less compressed air. Conversely, it increases the motor speed to increase compressed air output and maintain a stable system pressure. The role of the VFD in the system is similar to that of a fan motor or water pump in energy saving; it controls the input voltage frequency according to load changes.
Its energy-saving principle and effect are as follows:
1. After using a frequency converter, the air compressor pressure setting can be a single point, that is, the minimum pressure required to meet the production equipment can be used as the set pressure. The frequency converter will adjust the speed of the air compressor according to the trend of the fluctuation of the pipeline pressure, and even eliminate the unloading operation of the air compressor, saving energy.
2. Because the frequency converter in the system stabilizes the pressure in the pipeline, it can reduce or even eliminate pressure fluctuations, so that all the air compressors in the system operate at a lower pressure that meets production requirements, reducing the power loss caused by upward pressure fluctuations.
3. Since the compressor cannot rule out the possibility of operating at full load for extended periods, the motor capacity must be determined based on maximum demand, resulting in a generally larger design capacity. In actual operation, the proportion of time spent in light-load operation is very high. Using variable frequency speed control can significantly improve operating efficiency. Therefore, incorporating frequency converters into air compressor systems has great energy-saving potential.
4. Some adjustment methods (such as adjusting valve opening and changing blade angle) cannot reduce the motor's operating power even when demand is low. By using variable frequency speed control, the motor speed can be reduced when demand is low, thus reducing the motor's operating power and further achieving energy savings.
5. Single-motor drive systems generally cannot continuously adjust according to the load. However, with variable frequency speed control, continuous adjustment can be made very conveniently, maintaining the stability of parameters such as pressure, flow rate, and temperature, thereby greatly improving the compressor's performance.
