Can I reduce energy costs by replacing an old Variable Speed Drive with a new modern drive?

Replacing an existing modern variable speed drive with other variable speed drives will not save you money. 2022 drives from all major manufacturers have an operating efficiency of circa 98% efficiency.

Older drives going back to the 1980s will have the same efficiency; the only difference would be if the existing drive had been poorly maintained, and so the potential reduced running costs do not justify replacing good and reliable drive with new as the payback period would be decades.

Maintaining the existing drive may also offer the same benefits for a fraction of the costs. However, older drives should be replaced when spares are no longer available, or reliability issues start to occur, not as an energy-saving strategy.

There are, however, instances when the VSD reaches the point it needs replacing when changing technology type will provide additional savings, for example, a current 12 pulse VSD could be replaced with another 12 pulse, a standard 6 pulse VSD, an Active Front End (AFE) Low Harmonic VSD, or a VSD and filter package.

Undertaking one of our G5/5 harmonic surveys would tell you if the harmonic mitigation is required and by what amount. if it isn’t a requirement, then the new standard 6 pulse VSD would have the lowest running costs and would provide additional energy savings.

Both 12 pulse and AFE VSDs have approximately double the losses of a standard drive, and a standard VSD with an active power quality filter would be somewhere between the two depending on the branding and size of the filter required.

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