Energy saving and speed control by using Variable Frequency Drive on three phase induction motor driving centrifugal fans

Centrifugal fans have many industrial and commercial applications such as cooling tower fans, supply and return fans, exhaust fans, boiler combustion fans, and fume hood fans etc. The energy saving is possible in the applications where flow control is required. The most common methods used for the f

Project Title

Energy saving and speed control by using Variable Frequency Drive on three phase induction motor driving centrifugal fans

Project Area of Specialization

Shared Economy

Project Summary

Centrifugal fans have many industrial and commercial applications such as cooling tower fans, supply and return fans, exhaust fans, boiler combustion fans, and fume hood fans etc. The energy saving is possible in the applications where flow control is required. The most common methods used for the flow control of the fans are bypass air dampers, discharge air dampers and inlet guide vanes. These methods have following disadvantages motor driving the fan runs at constant speed and draws the rated power from the supply, the mechanical stresses on the system will increase, the system will be less reliable and less efficient. By using Variable Frequency Drive (VFD) the required flow of air can be obtained by adjusting the speed of the motor driving the fan. According to Affinity laws the horsepower required by the motor is proportional to cube of the speed of the fan, thus a small reduction in speed can save huge amount of power. The aim of this study is to investigate the amount of energy saving by using VFD on the motor driving fans. An experimental set up will be made in which a fan is connected to the shaft of the three-phase induction motor and the motor is operated on direct online (DOL) method in first case and in second case the motor is operated through VFD at different speeds. The amount of energy consumption in both the cases will be recorded. Finally, the total cost of energy in both the cases will be compared. Additionally, the motor will be operated at full load and at no load on DOL and then through VFD at full load and no load. In both methods the power factor will be measured at no load and full load and the amount of demand charges saved due to power factor improvement will be measured. The study will compare the inrush current drawn by motor operated through VFD and the other starting methods. The results of the study will be implemented on the induced draft fans, forced draft fans and cooling tower fans used in power plant.

Project Objectives

• To study the operation of VFD and its industrial applications.
• To study the industrial applications of centrifugal fans and their speed torque characteristics.
• To fabricate an experimental layout and performance measuring system of the centrifugal fan.
• To measure the energy consumption by operating the motor on DOL method and then through VFD.
• To measure the inrush current drawn by the motor started through VFD and other starting methods
• To measure the power factor on direct online method and then through variable frequency drive at no load and full load.
• To calculate the total amount of energy saving and its cost per year including the investment cost of VFD.

Project Implementation Method

• The project can be implemented on the induced draft fans, forced draft fans used in power plants.
• By sensing the temperature of the water output from the cooling tower the speed of the motors used for driving cooling fans can be adjusted accordingly by using VFD and huge amount of power can be saved.
• The project can be implemented in heating, ventilating and air conditioning (HVAC) systems in public buildings.

Benefits of the Project

• Huge amount of energy can be saved.
• The flow of air can be controlled effectively without any mechanical stress on the system.
• High precision, smooth start and control of three phase induction motor.
• High power factor, no need of phase advancer and capacitor bank for improvement of power factor.

Technical Details of Final Deliverable

The results obtained from the experimental work can be provided to the power plants in which motors driving cooling fans can be operated through the variable frequency drive by sensing the ambient temperature and the output water temperature of the cooling tower, the motor speed will be varied accordingly to give required cooling. In addition, the project can be implemented on induced draft fans and forced draft fans used in power plants. Only 20% reduction in fan speed can save 50% of the power drawn by the motor at full speed. Variable frequency drive technology can be introduced in the heating, ventilation and air condition (HVAC) components in the public buildings.

Final Deliverable of the Project

Hardware System

Type of Industry

Energy

Technologies

Shared Economy

Sustainable Development Goals

Decent Work and Economic Growth, Sustainable Cities and Communities, Responsible Consumption and Production

Required Resources

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