The present invention is directed to a direct-drive fan 
system and a variable 
process control system for efficiently managing the operation of fans in a cooling 
system such a as wet-
cooling tower or air-cooled 
heat exchanger (ACHE), 
HVAC systems, mechanical towers or 
chiller systems. The present invention is based on the integration of key features and characteristics such as 
tower thermal performance, fan speed and 
airflow, 
motor torque, fan 
pitch, fan speed, fan aerodynamic properties, and pump flow. The variable 
process control system processes feedback signals from multiple locations in 
order control a 
high torque, variable speed, 
permanent magnet motor to drive the fan. Such feedback signals represent certain operating conditions including motor temperature, basin temperature, vibrations, and pump flow rates. Other data processed by the variable 
process control system in order to control the motor include 
turbine back pressure set-point, condenser temperature set-point and 
plant part-load setting. The variable process 
control system processes this data and the aforesaid feedback signals to optimize the operation of the cooling system in order to prevent disruption of the industrial process and prevent equipment (
turbine) failure or trip. The variable process 
control system alerts the operators for the need to conduct 
maintenance actions to remedy deficient operating conditions such as condenser 
fouling. The variable process 
control system increases cooling for 
cracking crude and also adjusts the motor RPM, and hence the fan RPM, accordingly during 
plant part-load conditions in order to save energy.