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MV VFD application in ID fan of Danhe Power Generation Co., Ltd.
Abstract: The Harsvert-A VFDs are presented in the paper. The focus is on Series Connection Medium voltage Multi-level VFDs that are used in Danhe Generation Co.,Ltd. VFDs have a great of prospect in application because the drives can save a large mount of electric energy when they are used for fans.
Keywords: Multilevel Medium voltage VFD ID fan application and analysis

Question
Capacity of Jiaozuo Danhe Power Generation Co., Ltd. is 110MW. After reconstruction of 1# dedust fan, the power of fan increases 525kW. Variable frequency technology is an effective method to save energy. Variable frequency can realize soft start, reduce impact on equipment. In addition, VFD installation is very easy. It only series connects between breaker and motor. No need to change load and motor. It is necessary to use VFD to save energy for ID fan.

1. Reform method of VFD
Air flow is controlled by damper in 1# system. Big redundancy power and damper adjusting mode cause high power consumption.
Motor parameters ID fan parameters
model:Y560-8 Y4-73-11-27D
power:1000kW flow:425700m3/h
voltage:6kV pressure: 5064Pa
current:118.6A media ℃: 90℃
frequency:50HZ
speed:744r/min
According to practical operation, VFD current can be 100A, 18.6A less than motor rated current 118.6A. After research market, we finally choose Leader Harvest VFD. VFD current is 105A.
Bypass cabinet is installed to ensure system stability. When VFD is broken, motor can be switched to direct on line manually. Bypass circuit is composed of 3 breakers QS1, QS2 and QS3. QS2 and QS3 are interlocked. In variable frequency state, QS1 and QS2 close, QS3 opens. In direct on line state, QS3 closes, QS1 and QS2 open.
In order to protect VFD, we design link lock with QF. Once VFD is broken, VFD switches off QF. In direct on line state, VFD cancels signal of QF trip-off to make motor run in direct on line.
VFD can also be equipped with upper PC. The PC is installed in control room. User can start/stop, set speed through PC. PC can show operation data and current state. User can also control VFD through operation platform.

2. Data comparison
A side variable frequency operation record

Load MW Fan current(A) Damper opening(%) A side speed (r/min) A side frequency (Hz) pressure (KPa) Furnace subpressure (Pa)
A side B side A side B side
65 3.6/46.4 55 100 30 350 23.41 3.0 -20
65 3.5/45.6 55 100 30 350 23.41 3.0 -20
63 3.5/45.6 56 100 30 349.3 23.41 3.0 -20
62 3.5/46.2 55 100 30 349.3 23.41 3.0 -20
106 30.5/84.8 48 100 5 746 49.9 4.1 -20
109 29.8/83.7 52 100 25 746 49.9 4.1 -20

B side variable frequency operation record

Load MW Fan current(A) Damper opening(%) A side speed (r/min) A side frequency (Hz) Pressure (Ka) Subpressure (Pa)
A side B side A side B side
60 77 1.7/42.5 60 100 242 16.18 3.0 -20
60 68 3.8/42.4 49 100 299 19.95 3.0 -20
60 58 9.6/44.3 34 100 400 26.63 3.0 -20
60 55 18.1/49.6 20 100 500 33.28 3.0 -20
60 50 32.2/58 10 100 600 39.91 3.0 -20
93 53 49.8/70.3 20 100 700 46.54 3.8 -20
93 52 61/77.3 17 100 747 49.68 3.8 -20

3. Calculation

1) 110MW, energy saved in an hour
ID fan power before reconstruction:
0.9539*6*67*1.732*0.8506=565kw
ID fan power after reconstruction:
0.9539*6*29*1.05*1.732*0.8506=257kw
(565-257)*2=616kw
2) 80MW, energy saved in an hour
ID fan power before reconstruction :
0.9539*6*60*1.732*0.8506=506kw
ID fan power after reconstruction:
0.9539*6*21*1.05*1.732*0.8506=186kw
(506-186)*2=640kw
3) 60MW, energy saved in an hour
ID fan powr before reconstruction:
0.9539*6*55*1.732*0.8506=464kw
ID fan power after reconstruction:
0.9539*6*11*1.05*1.732*0.8506=97kw
(464-97)*2=734kw
#1 yearly work time is 7764h in 2002,yearly energy saved is:
7764*(616*25%+640*50%+734*25%)=5104830Kwh
Price: 0.22yuan/Kwh
Energy saved is: 5104830*0.22=1123100yuan

In addition, because power factor of Harsvert VFD can be 0.95 which is more than that of motor 0.8506. It reduces reactive power and heightens equipment utilization factor. VFD realizes motor soft start and reduces influence of motor insulation and lifetime.

4. Concluding remarks
Energy saving effect of VFD is very obvious, especially in low load. With VFD, motor realizes soft-start. Damper is full open, which reduces vibration and damage. VFD will be widely used for more and more power plants as its excellent energy saving effect.

Reference:
1. Reconstruction material of 1# ID fan in Jiaozuo Danhe Power Generation Co., Ltd.
2. HARSVERT-A06/105 VFD principal

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