The performance of variable-frequency drives (VFDs) can be compared with that of other methods of volume control quickly and simply. All that you need are:
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Motor horsepower;
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The alternative to VFD control (inlet guide vane, outlet damper, “ride the fan curve,” bypass damper, discharge valve, bypass valve, no control);
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The total hours of operation per year (8,760 maximum);
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The cost per kilowatt-hour of electricity.
NOTE
1) This is only an estimate based on averages and assumptions. Additional savings, such as power-factor improvement to 0.98 and reduced demand charges, also should be considered.