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Application of Harsvert VFD on circulating fan
I. Introduction
Tongli Cement Co., Ltd was established in 1995. It has two work lines with daily production 2500t and yearly production 2000000t. In 2006, Tongli cement plant purchased Harsvert-A06/150 to adjust speed. The drive has been running stably since it carried into operation on January in 2007 and energy-saving is considerable.
II. Energy-saving effect
Circulating fan is driven by wire-wound motor. Its rated power is 6kV/1250kW. Before using VFD, air flow was adjusted by valve and there is much power loss on valve. Meanwhile, because valve was adjusted frequently, reliability of valve was not good, which affected system stability. After using VFD ( short connecting rotor winding), motor speed is adjusted by VFD. There is no need to adjust valve frequently and valve opens at a large scope.

Data in the site:

item Before modification After modification
Total material volume (t/h) 220 200
Given speed of VFD (r/min) 1000 820
Grinding head pressure(Pa) 13 160
Grinding tail pressure(Pa) 1000 1100
Motor current A 55 35
Noise 67 67
Outlet pressure(Pa) 2300 1800
Outlet temperature (℃) 78 52

We can see that motor current is lower after reconstruction with VFD and energy is saved a lot.

III. Characters of Harsvert VFD

Model Harsvert-A06/150
Rated capacity 1565KVA
Rated current 150A
Rated voltage 6kV
Output frequency 0~50Hz
Motor power 1250kW
Acceleration/deceleration time 0~3200s
Over load capacity 120% for 60s, 150% for 3s, 200% immediately
Protection Over voltage, low voltage, over current, over heat, earth, lack phase and so on.

IV. Advantages
When motor starts, current increases from zero and will be not over rated current. So VFD avoids big current impact when motor starts, decreases maintenance, improves system safety.

V. Conclusion
Adjusting speed by VFD is not only easy and convenient but also saves much energy. It improves system safety and manufacture process.

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