Variable Speed Drives
It is our opinion that Variable Speed Drives should be fitted to all Cooling Towers as standard. Variable Speed Drives save power thus saving the cooling demand for a power station. It can also be argued that fitting a Variable Speed Drive can also help reduce drift in especially old towers that may not have fully complying eliminators.
Features Operational Benefits
Adjustable speed Variable Speed Drive
- Matches air flow to system demand which typically uses nearly 60% less fan motor energy then fixed air flow system
- Drastically reduces fan noise level
- Eliminates annoying fan's cycling
- Eliminates excessive cooling water loss
- Eliminates the need for output water throttling valve
- Maintains water at the desired temperature
- Most efficient method of adjustable speed
- Significantly reduces the amount of make-up water required.
- Power consumption closely follows HP requirements of fan at all speeds
- Lowest installation cost
- No mechanical fabrication required
- Control can be mounted remotely from motor
- Can use existing motor wiring.
- Works with economical rugged, readily available AC motor
- Works with any brand AC induction Motor, standard or high efficiency
- Can use existing motors when updating fixed speed system
- Optional bypass capability eliminates down time
Minimum Maintenance Variable
- No rotary air unions or variable pitch hubs to maintain
- No pneumatic signals required
- Reduces chances of freeze-up
Multi Fan Capability
- One drive can control a combination of fans
- Inherent speed matching of motors
- Total costs are down because one drive per fan is not required.
Inherent Soft Start
- Reduces line voltage fluctuation caused by high demand
- Increases life of reducers, bearings, belts and fans
Sinewave PWM Output
- Motor noise is minimal regardless of speed or load.
Variable frequency AC drive is used to adjust the speed and therefore, the flow of the fan or fans on a cooling tower. The AC drive receives a control signal from the cooling tower control system and adjust the fan's speed to deliver water exactly the desired temperature.
The power requirement of cooling tower fan varies as a cube of its speed. The AC Variable frequency drive allows the cooling tower fan to run at whatever speed is required to meet the cooing demand. Typically the fan runs at only 40 - 70% of full speed, thus saving 50% or more of the energy consume by fixed speed system.
The AC variable frequency drive can be retrofitted to any existing AC motor and fan. One drive can operate a number of cooling tower fans at proportional speed. No complex feed back or reference circuits are required.
THE ENERGY SAVING POTENTIAL
A cooling tower is designed to remove heat from the incoming water at a specific rate. It delivers a specified flow of water at a temperature that should never exceed the designed temperature. Because the cooling of the water is due to evaporation, the wet bulb temperature of the ambient air is important. The cooling tower must be designed to provide water no higher than the specified temperature at the highest wet bulb temperature the cooling tower will experience. Every time the actual wet bulb temperature is lower than the design wet bulb, an energy saving potential exists. Daily and seasonal changes in the ambient wet bulb temperatures allow the fan speed to be modulated and this reduces energy consumed by the fan's motor. The magnitude of this saving potential depends upon the range of wet bulb temperatures actually encountered. The cost of saved energy can be worked only.
Additional savings are obtainable if the process has a variable heat output to the cooling tower. Modulating the fan speed will also reduce the evaporation rate of the treated cooling water, saving both water and the water treatment chemicals. The wear & tear caused by cycling the equipment will be eliminated.