Variable Speed Cooling Tower Fan

The operating cost of cooling tower operation is.

Variable speed cooling tower fan. Vfd controlled cooling tower fans operate over many speeds as opposed to the fans on a single or two speed motor starter. The controlled variable is the temperature of the cooling water that is sent back to the process and the manipulated variable is the air flow through the tower which can be changed either by adjusting the speed of variable speed fans or by starting and stopping a number of constant speed fans. Vfd controlled cooling tower fans operate over many speeds as opposed to the fans on a single or two speed motor starter. The paper presents variable speed drive vsd structures for automatic speed regulation of cooling tower fans in order to maintain a constant temperature for the circulated technological water.

A variable speed drive vsd controls the speed of the high torque direct drive motor for optimal fan operation. Annual fan electrical energy requirements are calculated for towers with single speed two speed and variable speed fans. When variable condenser water flow and variable speed cooling tower fans are implemented on the same system care must be taken in the development of control strategies. One way is to increase capacity of cooling tower by installing another cooling tower cell.

Fan energy requirements are determined counter flow and cross flow towers. If your facility has variable speed cooling tower fans approach can be reduced by increasing fan speed and therefore taking advantage of more evaporative cooling. The cooling system usually features cooling towers that house large fan blades. Abb direct drive motor and variable speed drive packages for industrial cooling replace the gearbox driveshaft and induction motor typically used in industrial cooling fans.

If fan speed and heat load are maintained constant for a given wet bulb temperature approach is constant. To power the fan it is now possible for a high efficiency permanent magnet direct drive motor to be coupled directly to the fan. As such it is a good practice to perform a vibration analysis on the fan and tower assembly as a mechanical resonance may develop at certain speeds. Other way is to keep the same cooling tower and install variable frequency drive vfd on cooling tower fans so that we can increase fan speed hence increase air flow to get the required cooling and reduced cooling water supply temperature.

Typically the best course of action is to establish a condenser water minimum flow for each pump and vary the condenser water flow based on chiller loading.