According to your previous concerns about the selection of industrial air compressors, operation and maintenance of air compressor rooms and other related requirements, the core conclusion is that there is no absolute “who saves more electricity” for the comparison of frequency conversion and power frequency air compressors. The energy saving performance is entirely determined by the actual gas consumption conditions. The specific differences are as follows:
Energy Consumption Logic of 1. Power Frequency Air Compressor
The motor of the power frequency air compressor runs at a fixed speed, and the air volume is adjusted by loading/unloading: when the air consumption is low, the motor will still consume 30% ~ 50% of the rated power, which is completely invalid no-load loss. At the same time, in order to reduce frequent start-up and stop, its air supply pressure bandwidth is usually set to be wide (such as 0. 7-1MPa), long-term high-voltage operation will consume more than 12% of the additional electric energy, plus the instantaneous impact loss of 3-5 times the rated current during hard start, the overall ineffective energy consumption is very high.
Energy Saving Advantages of 2. Variable Frequency Air Compressor
The variable frequency air compressor adjusts the motor speed in real time through the frequency converter, can dynamically match the back-end gas demand, hardly enters the unloading state, and completely eliminates the no-load invalid power consumption. At the same time, it can stabilize the gas supply pressure within a very small range of ± 0.02MPa, avoiding compression loss caused by high pressure redundancy. For every 0. 1MPa pressure reduction, energy consumption can be reduced by 6% ~ 8%. Coupled with the characteristics of soft start without current impact, the comprehensive energy saving rate can reach 20% ~ 35% under most gas fluctuation scenarios.
Condition boundary of 3. power saving effect
When the gas consumption in the workshop fluctuates by more than 30%, the gas consumption is uneven day and night, and it belongs to intermittent production, the power saving advantage of the variable frequency air compressor will be fully enlarged, and the electricity cost will be saved considerably after long-term operation. Usually, the higher purchase price difference of the variable frequency air compressor can be recovered within 1-2 years.
If it is a working condition with full load and almost zero fluctuation of gas consumption 24 hours a day, the energy consumption difference between the two is less than 5%. At this time, the purchase cost of the power frequency air compressor is lower, and the comprehensive cost performance ratio is better.
A simple judgment standard: if the daily unloading time of the existing power frequency air compressor exceeds 15% of the total operating time, obvious power saving benefits can be obtained by replacing the frequency conversion model.