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
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 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.
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.
| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Variable Frequency Drive | Equipment | 1 | 20000 | 20000 |
| Three Phase Induction Motor(1Hp) | Equipment | 1 | 18000 | 18000 |
| Centrifugal Fan | Equipment | 1 | 12000 | 12000 |
| Magnetic Contractor (HIMC 12) Hyundai 220V | Equipment | 1 | 1600 | 1600 |
| Electronic Over Current Relay(0.5 to 6.5amps) | Equipment | 1 | 1000 | 1000 |
| Miniature Circuit Breaker(C6) | Equipment | 1 | 1000 | 1000 |
| Three Phase Energy meter | Equipment | 1 | 7000 | 7000 |
| Measuring Equipment's | Equipment | 1 | 5000 | 5000 |
| Total in (Rs) | 65600 |
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