• ENE-CAS-5
  • 空壓系統
  • 系統設計、安裝或更新-採變速控制
  • Variable speed drives (VSD, see Section 3.6.3) for compressors find applications mainly when the process air requirements of the users fluctuate, over times of the day and days of the week. Conventional compressor control systems such as load/unload, modulation, capacity control and others, try to follow this change in the air demand. If this leads to high switching frequencies and high idle time, a consequential reduction in the energy efficiency takes place. In VSD compressors, the speed of the electric motor is varied in relation to the compressed air demands, resulting in a high level of energy savings.
    Studies show that a majority of compressed air applications have moderate to large fluctuations in air demand and hence there is great potential for energy savings by the application of variable speed driven compressors.


  • None.

  • Variable speed drive compressors are appropriate for a number of operations in a wide range of industries, including metal, food, textile, pharmaceutical, chemical plants, etc. where there is a highly fluctuating demand pattern f or compressed air. No real benefit can be achieved if the compressor operates continuously at its full capacity or close to it (see Examples, below).
    VSD compressors may be applied into an existing compressed air installation. On the other hand, VSD controllers could be integrated into existing fixed speed compressors; however, better performances are obtained when the VSD controller and the motor are supplied in conjunction since they are matched to give the highest efficiency within the speed range. VSD applications should be limited to more up- to-date compressors due to possible problems with older compressors. The manufacturer or CAS expert should be consulted if in doubt.
    Many CASs already have a variable speed driven compressor so the applicability across industry for additional variable speed compressors is some 25 %. The savings can be up to 30 %, although the average gain in a CAS, where one compressor with a variable speed drive is added, is about 15 %. It is likely that more CASs can employ variable speed driven compressors to their advantage.


  • Energy typically constitutes about 80 % of the life cycle costs of the compressor, the balance of 20 % comprises investments and maintenance. An installation, where (conservatively estimated) 15 % energy is saved owing to using variable speed drives, saves 12 % life cycle costs, whereas the additional investment for the variable speed compressor (instead of a traditional one) adds only some 2 to 5 % to the life cycle costs.


  • Energy Efficiency (2009) 3.7.2