Korea Ever-Power · Y2 Series · Cooling Tower Fan Drive Guide

The air passing through the cooling tower is saturated (100% RH) at the fan inlet. Any motor surface below the dew point of the saturated air will accumulate condensation continuously. This condensation enters motor housings rated below IP65, wets winding insulation, and causes insulation resistance degradation and premature winding failure.

The fan draws not just saturated air but also small water droplets that are entrained in the airstream from the fill section. These droplets are mineral-laden (calcium carbonate, silica, dissolved salts) and deposit on motor surfaces as the water evaporates, forming a mineral scale that absorbs moisture and accelerates corrosion.

Cooling water is treated with biocides (chlorine, bromine, quaternary ammonium compounds) to control Legionella and algae. These chemicals are present in the droplets reaching the motor and can attack motor paint coatings and winding varnish over time. Scale inhibitors and corrosion inhibitors in the cooling water add additional chemical exposure.

Cooling tower fan motors cycle through significant temperature changes: warm humid air during full load operation (40 to 50°C ambient near the fan), cold ambient at night or during winter shutdown (below 0°C in cold climates), and the thermal shock of the motor cooling rapidly when switched off. Class F insulation resists the thermal cycling effects on winding insulation that Class B-insulated motors may not.

Packaged cooling towers with small fans (0.5 to 1.5 m diameter) where gearbox or belt reduction achieves final fan speed. Also used for direct drive on small forced-draft cooling towers where fan design speed is 1,200 to 1,400 rpm.

Standard for cooling tower direct-drive applications. 960 rpm is within the operating range of most large-diameter FRP cooling tower fan blades (2 to 6 m diameter) without requiring a gearbox. Most common specification for industrial and HVAC cooling towers.

Very large cooling towers with fan diameters above 5 m where fan tip speed at 960 rpm would exceed design limits. Also used for low-noise cooling towers where 720 rpm reduces aerodynamic noise compared to 960 rpm operation at the same airflow.

Two-speed pole-changing motor for cooling towers requiring two fan speeds (high speed in summer peak, low speed in mild weather). YD motor replaces two separate motors and avoids the complexity of external winding changeover relays. See Section 5 for control.

The motor is positioned in the airstream above the fill section, directly exposed to warm water-saturated air and water droplet carryover from the spray headers below. IP55 (dust-protected, protected against water jets from any direction) is the minimum requirement for cooling tower fan motor installation. IP55 prevents the direct entry of water droplets carried in the airstream and limits the rate at which humid air enters the motor housing through breathing. Motors rated at IP54 or lower have been shown to fail from winding insulation degradation in cooling tower service within 2 to 4 years, requiring the IP55 specification for reliable long-term service.

Standard motor paint and frame coatings are designed for dry industrial environments and degrade rapidly in the wet, mineral-laden cooling tower atmosphere. Korea Ever-Power Y2 series cooling tower option includes: epoxy-based winding impregnation with moisture resistance specification; marine-grade epoxy primer and polyurethane topcoat on all external surfaces; stainless steel or hot-dip galvanised terminal box screws and nameplate fixings; and silicon carbide wiper seals on shaft penetrations. These corrosion-resistant treatments extend typical cooling tower motor service life from 2 to 4 years (standard motor) to 8 to 15 years (Y2 cooling tower specification).

Cooling tower fan motors below 11 kW can be DOL started. The fan starting inertia is high (large-diameter fan blades have significant rotational inertia) but the starting torque requirement is low because the fan blade pitch is low and airflow resistance at standstill is minimal. Starting current 6 to 7 times rated for 3 to 6 seconds before the fan reaches rated speed is typical. DOL starting is the simplest approach for single-speed small cooling tower fans.

Cooling tower fan motors above 11 kW should use star-delta starting or a soft-starter to reduce the starting current impact on the supply. The high fan inertia means the motor accelerates slowly under star-delta and the time in star connection is long — 8 to 15 seconds is typical for a 6-pole motor driving a 4 to 6 m fan. The star-delta transition must be smooth; a resistor-assisted transition is preferred for large fans to avoid the current surge at the moment of delta connection.

Using a YD multi-speed pole-changing motor (4/6-pole giving 1,450/960 rpm) on the cooling tower fan provides two fixed fan speeds without a VFD. In summer peak cooling demand, the fan runs at high speed (1,450 rpm, maximum airflow and cooling capacity). In mild weather, switching to low speed (960 rpm) reduces fan power by approximately 70% (cube of speed ratio: (960/1,450)³ = 0.29) while maintaining sufficient cooling. Two-speed control is the most cost-effective capacity control method for cooling towers that do not require continuous modulation.

The Korea Ever-Power Y2 series in 6-pole and 8-pole configurations covers the 0.75 to 45 kW power range required for direct-drive cooling tower fan motors. The 6-pole Y2 at 960 rpm is the standard specification for the majority of industrial and commercial cooling tower fan applications. Korea Ever-Power supplies the Y2 for cooling tower service with enhanced moisture-resistant winding impregnation, corrosion-resistant exterior coating, and stainless steel terminal box fixings as a cooling tower package specification. The complete Y2 range is in the three-phase motor product section. Contact Korea Ever-Power for cooling tower package specifications including space heater, space heater control relay, and anti-condensation winding treatment options.

Counterflow and crossflow cooling towers for industrial process cooling (chemical, petrochemical, power plant, manufacturing). Fan motors 7.5 to 45 kW, 6-pole, IP55, Class F. Typical tower cell configurations use 2 to 8 fan cells each with one motor. Y2 6-pole direct drive is the standard specification for cells with 2 to 5 m fan diameter.

Packaged and field-erected cooling towers for building air-conditioning chiller condensers. Fan motors 0.75 to 15 kW, 6-pole or 4-pole with gearbox for small towers. Two-speed YD motor popular for office building cooling towers where part-load operation is the majority of annual hours.

Cooling towers for data centre chiller plant condensing. Very high annual operating hours (8,760 hours/year continuous). Y2 6-pole 3.0 to 22 kW, IP55, with space heater for the tower shutdown periods. Long life specification essential given the critical role of cooling in data centre continuity.

Evaporative condensers for refrigeration systems (cold stores, food processing, industrial refrigeration) use a combined direct-air and evaporative cooling mechanism. Motor requirements are identical to cooling tower fan motors — IP55, 6-pole, moisture-resistant winding, corrosion-resistant exterior. Y2 0.75 to 7.5 kW covers most evaporative condenser fan applications.