A handful of power transmission technologies are available for cooling towers and each has advantages and disadvantages.
Gear drives are used commonly across all cooling tower power levels, offering high efficiency (near 96%), moderate initial cost and low lifetime operating costs. Because the gears are protected by thick, casted shells, gear drives are well suited to the high heat and humid conditions inside cooling towers.
Belt drives offer smooth transmission of power between shafts. This technology is an economical method of power transmission at initial cost, but routine maintenance and belt replacement contributes to higher operating costs. Starting at 95% efficiency, belt drives can drop to the low 90s or even lower as belts stretch and wear.
Direct drive options, often using a permanent magnet motor, can reduce maintenance and lifetime operating costs, but often come with significantly higher initial cost. Direct drive efficiencies compare favorably with gear drives; and oil changes and alignment issues are eliminated.
The electronically commutated motor (ECM) is a relatively new technology that combines the motor, speed controller and fan together in one package, eliminating the need for an external variable frequency drive. Because ECMs use sealed bearings, they require no routine maintenance. The use of this technology in cooling towers is currently limited to small and fractional hp applications and small fan diameters.
When selecting a cooling tower power transmission technology, factors such as energy efficiency, ease of maintenance, reliability and service life must be balanced against initial investment, installation costs, operational complexity and environmental impact. Which power transmission technologies do you most frequently choose?