Good Practice: Variable frequency device for controlling motor and fans, Beijing, China

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Setting

Country: China
Location: Beijing
Technology keywords: Variable frequency device, motors and fans
Host sector: Industrial sectors
Ref: SETatWork Good Practice # 39

Objective of the Project

A variable-frequency drive is an electronic controller that adjusts the speed of an electric motor by modulating the power being delivered; it provides continuous control, matching motor speed to the specific demands of the work being performed. Variable-frequency drives are an excellent choice for adjustable-speed drive users because they allow operators to fine-tune processes while reducing costs for energy and equipment maintenance.

Technical Summary

In Lidu power centre in Beijing, there were three boilers of 20t/h, equipped with auxiliary devices including: three 75kW draught fans, three 55kW blast fans, one 22.5 kW feed-in water pump, one 7.5 kW condensing water pump and one 22kW washing slag pump. Because the steam demand was varied with seasons and climates, the flow of air and water to the boiler should be controlled to match with the steam demand. Mechanical devices such as flow-restricting valves or moveable air vanes were often used to control flow, but this process used excessive energy and may create punishing conditions for the mechanical equipment involved. In order to saving energy, variable-frequency drives were successively installed in 9 fans and pumps mentioned above, to control flows of air and water into the boiler by adjusting speed of fans and pumps, which led to more energy saving than the previous conditions.

See the Good Practice Case Study PDF file for further information

Environmental and Social Benefits

• Lower CO₂, SO₂ and NO_x emission by saving electricity from coal-fired power plants.
• Lower noises from the motors and improve on-site environment.
• Save significant energy as much as 50%.
• Reduce maintenance and repair costs and extend motor life, by lessening mechanical and electrical stress on the motor system.
• Allow more precise control of process, such as air and water flows.

There are great applications where flow requirements vary, such as fans and pumps in boilers.

Economic Data

Capital Costs: Total investment 667000 CNY
Payback period: 1.88 years

To find similar reports, click on a keyword below:
SETatWork: Sustainable Energy Technology at Work (2008-2010) : Coal Combustion : Energy Efficient Technologies : Heating Ventilation and Air Conditioning : Manufacturing Industries : Power Generation and Use : Process Technologies

ZERI - Zhejiang Energy Research Institute of China