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This application introduces frequency inverter in ID fan reconstruction.
Inverter not only saves energy, but also improves start-up of motor and
fan, prolongs lifetime of equipment.
Inverter Structure
In general, the load of the unit varies in the range of 50%~100%. Generator output power varies. Forced air flow and induced air flow of boiler vary correspondingly. ID fan is adjusted by changing angle of blade. Although there is energy-saving to some extent contrast to damper adjustment. The loss is still considerable, especially in the situation of low load. Secondly the slow adjustment of static blade may lead to the load lag correspondingly. Generally, the starting current of asynchronous motor is 8~10 times of the rated current, which may surge the power grid. Big torque also affects lifetime of motor and fan badly.
When the speed of the fan varies, the efficiency varies a little. The flow is directly proportional to speed. Pressure is directly proportional to the square of the speed, and shaft power is directly proportional to the cube of the speed. Furthermore, the shaft power would reduce in cube relation when the speed is down, so does the motor power. Then we know that speed adjusting is the key of energy-saving for fans. It could achieve linear adjustment for ID fan with inverter.
Frequency inverter can optimize the operation of the motor and enhance efficiency greatly to save energy. There were some restrictions before, such as price, reliability, capacity etc. inverter was not widely used. Recently, with the rapid development of power devices, control theory and computer science, declining price of inverter and increasing reliability, MV inverter has been widely used in auxiliary equipment of power plants.
Inverter Structure
In general, the load of the unit varies in the range of 50%~100%. Generator output power varies. Forced air flow and induced air flow of boiler vary correspondingly. ID fan is adjusted by changing angle of blade. Although there is energy-saving to some extent contrast to damper adjustment. The loss is still considerable, especially in the situation of low load. Secondly the slow adjustment of static blade may lead to the load lag correspondingly. Generally, the starting current of asynchronous motor is 8~10 times of the rated current, which may surge the power grid. Big torque also affects lifetime of motor and fan badly.
When the speed of the fan varies, the efficiency varies a little. The flow is directly proportional to speed. Pressure is directly proportional to the square of the speed, and shaft power is directly proportional to the cube of the speed. Furthermore, the shaft power would reduce in cube relation when the speed is down, so does the motor power. Then we know that speed adjusting is the key of energy-saving for fans. It could achieve linear adjustment for ID fan with inverter.
Frequency inverter can optimize the operation of the motor and enhance efficiency greatly to save energy. There were some restrictions before, such as price, reliability, capacity etc. inverter was not widely used. Recently, with the rapid development of power devices, control theory and computer science, declining price of inverter and increasing reliability, MV inverter has been widely used in auxiliary equipment of power plants.
Frequency inverters have a great of prospect in application because the
inverter can save a large amount of electric energy when they are used
for fans.
Capacity of the Power Generation 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, inverter installation is very easy. It only series connects between breaker and motor. No need to change load and motor. It is necessary to use inverter to save energy for ID fan.
Inverter reform
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, inverter current can be 100A, 18.6A less than motor rated current 118.6A. After research market, we finally choose Gozuk inverter. The inverter current is 105A.
Bypass cabinet is installed to ensure system stability. When the frequency inverter 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 inverter, we design link lock with QF. Once the inverter is broken, inverter switches off QF. In direct on line state, inverter cancels signal of QF trip-off to make motor run in direct on line.
Frequency inverter 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 inverter through operation platform.
Capacity of the Power Generation 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, inverter installation is very easy. It only series connects between breaker and motor. No need to change load and motor. It is necessary to use inverter to save energy for ID fan.
Inverter reform
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, inverter current can be 100A, 18.6A less than motor rated current 118.6A. After research market, we finally choose Gozuk inverter. The inverter current is 105A.
Bypass cabinet is installed to ensure system stability. When the frequency inverter 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 inverter, we design link lock with QF. Once the inverter is broken, inverter switches off QF. In direct on line state, inverter cancels signal of QF trip-off to make motor run in direct on line.
Frequency inverter 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 inverter through operation platform.
Tags: inverter, Power Generation