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Variable speed compressor vs fixed speed compressor

If you need an air compressor that can offer reliable performance when dealing with varying air demands, a variable speed compressor (VSD) might be the way to go instead of the more traditional fixed-speed compressor. However, you must make an informed decision before choosing your compressor unit as a VSD compressor might not be the best option for your requirements.

In this article, Glaston Compressor Services examines the case for using variable speed compressors by comparing them directly with their fixed-speed counterpart and seeing which comes out on top.

Variable speed compressor energy savings

The key benefit of using a variable speed compressor is their ability to effectively meet fluctuating air demands by controlling speed. Because a variable-speed compressor runs only at the required speed, this can present businesses with substantial energy saving costs.

By rotating slowly, variable speed compressors produce less and, as a result, absorb less energy. They can automatically slow down their rotation speed until the unit produces the precise amount of compressed air for the downstream equipment. As a result, variable speed compressors can save around 30% on average when compared to the energy costs of fixed-speed compressors.

How do VSD energy savings compare to fixed speed compressors?

Unless your application has either full load or no load requirements, the ability to save considerable energy costs should not be ignored. As most applications tend to have a fluctuating air demand, this is one area where VSDs have the edge over fixed-speed compressors.

Additionally, if your business qualifies for energy-saving programmes then there might be an added incentive for using a variable-speed compressor because it can help towards this.

Variable speed compressor advantages

Aside from saving money on energy costs, variable speed compressors can also stop and start under full system pressure. Because there is no need to unload, this can contribute towards increasing productivity. Additional benefits of using variable speed compressors include:

  • Quieter operation under lower RPM
  • The ability to run on 100% airflow
  • Minimised system leakages due to lower pressure
  • Avoiding peak currents at compressor start-ups
  • Soft motor starts
  • Removing blow-off losses during operation
  • Increased component lifetime
  • Consistent plant pressure

How do VSD benefits compare to fixed speed compressors?

A fixed speed compressor can provide a constant supply of compressed air 24/7, albeit one that is limited to a fixed RPM unless turned off manually. They are most efficient in applications with consistent compressed air demands, not ones that might have peaks and troughs. Generally, they have a lower capital cost, lower maintenance and repair fees, and increased availability of spare parts.

It is important to note that despite their energy-saving potential, variable speed compressors are much more of an investment compared to fixed speed compressors, which are cheaper to purchase and cost less to maintain.

Variable speed compressor reliability

Variable speed compressors are very reliable when it comes to addressing fluctuating air demand. Using variable speed drive technology, they can change the frequency that they supply to their motors, meaning they can adjust the spin speed of their rotary screws.

Depending on the air pressure requirements at any one time, they can speed up and slow down to address specific requirements without over-consumption.

How reliable are VSD compressors compared to fixed speed compressors?

If your business operates 24/7 without any notable disruptions to production cycles or has a consistent rate of energy consumption, fixed speed compressors can be just as reliable as their VSD counterparts. However, if your business has frequent changes in production outputs – be they daily, weekly or even seasonal – a fixed speed compressor will ultimately use more energy than variable speed compressors.

That said, because variable speed compressors can change operational speeds, they are more prone to inconsistencies coming from their power source and are particularly sensitive to heat and moisture exposure.

Variable speed vs fixed speed: which is better?

The key differences between variable speed and fixed speed compressors are the way the motor is controlled, how much energy they can save, and how much they cost to maintain. While variable speed technology is more superior for adapting to changing air demand and therefore saving considerable energy costs, they might not be worth the investment if they don’t match your site requirements.

For example, if your business is prone to peaks in production cycles or fluctuations daily, then a VSD compressor will be better, providing it won’t take too long to reap the energy-saving benefits. Alternatively, if your business experiences drop-offs or surges that can’t be controlled, a VSD compressor might not be worth both the initial or the long-term cost.

If you are unsure about whether your business requires a variable speed compressor or not, Glaston Compressor Services can offer a site audit to assess which method of compressed air generation is most beneficial for your requirements.

With years of industry experience, our compressor engineers can provide the most comprehensive service available anywhere in the North West of England. Glaston has an extensive on-site stock of air compressor systems, including fixed speed compressors and variable speed drive compressors.

To arrange a site visit today, speak with Glaston Compressor Services on 01695 51010, email info@glaston.com or view our range of compressed air services online.

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