Saving energy in motors and drives

Quick hits to look out for

• The most obvious thing: is the driven equipment doing a useful job, or running idle for example? If so, consider time switching or automatic stop/start control (this might include motor load sensing).
• Do you have oversized motors? Hint: you can find out by noting the current and applying the formula √3 x amps x volts x PF / 1000 which gives actual power in kilowatts. PF represents power factor: assume 0.9 (see note 1). Compare the result with the motor’s nameplate rating to see if it is only part-loaded.
• Unusually hot or noisy gearboxes indicate frictional energy losses: thermal imaging equipment can help.
• Are V-belts worn or slack?
• Are pulleys and couplings properly aligned?

Common Opportunities

• Substitute a high-efficiency motor when replacement is necessary.
• Change pulley ratios to run driven equipment at optimum speed.
• If a motor permanently lightly-loaded, switch to permanent star connection or fit a smaller motor.
• On a part-loaded multi-belt drive, remove one or more belts to leave only the minimum required for the power actually being transmitted.
• Consider variable speed drive or multi-speed motor depending on the circumstances
• Where the duty toggles between high and low load, consider replacement with a multi-speed motor (up to four load steps may be accommodated by MSM).
• When V-belt pulleys need replacing, opt for wedge belts (2% improvement) or synchronous, flat, or ribbed belts (5-6% improvement).
• Where possible replace gearboxes with variable-speed direct drives
• Adopt high-performance lubricants

Further information