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Frequency inverters are basically a green energy savings product that matches the amount of work or load on a motor to the amount of energy it needs to power that amount of work. This reduces excess energy from being wasted.
We use a lot of energy in this country and most of that energy is used to move air and water around a building. About half the electricity in commercial buildings is just used to move air and water around, so a frequency inverter is a big way to save energy there. If you look at a typical pump motor the life cycle cost of a pump, 90% of its life cycle costs is the energy it consumes and only 10% the actual cost of the pump motor… a frequency inverter can cut that in half.
Most motors are oversized to deal with your worst-case scenarios, your peak loads. A frequency inverter allows you to run that motor at the load it needs to be instead of running it at peak load all the time. Another benefit is it has a built-in soft start capability. So those combinations of things are going to give you savings; not only on energy, but also extending the life of the motor.
So what is a frequency inverter? Some of the different names that are used in the industry are a inverter, an adjustable frequency drive, a variable speed drive, or an adjustable speed drive. The technology has been around for quite a few years but only has started to make some headway in HVAC and pumping applications in the last several years. The size and cost of electronics has made frequency inverters applicable to a wider range of motors and increased the opportunity for savings.
All frequency inverters are going to take 3 phase AC power and convert that 3 phase power to DC power inside the drive and pulse it out in a simulated AC wave form to the motor. The motor still thinks it has AC power but the DC power conversion now lets us control the speed of the motor without harming it. Now we are in control to save energy and money.
The basic concept with the savings for frequency inverters is your speed and your flow are more or less proportional. But the energy consumption is cubed. If you're running your motor at full speed 60 Hertz, you don't have any savings- but any reduction pays the reduction cubed.
We use a lot of energy in this country and most of that energy is used to move air and water around a building. About half the electricity in commercial buildings is just used to move air and water around, so a frequency inverter is a big way to save energy there. If you look at a typical pump motor the life cycle cost of a pump, 90% of its life cycle costs is the energy it consumes and only 10% the actual cost of the pump motor… a frequency inverter can cut that in half.
Most motors are oversized to deal with your worst-case scenarios, your peak loads. A frequency inverter allows you to run that motor at the load it needs to be instead of running it at peak load all the time. Another benefit is it has a built-in soft start capability. So those combinations of things are going to give you savings; not only on energy, but also extending the life of the motor.
So what is a frequency inverter? Some of the different names that are used in the industry are a inverter, an adjustable frequency drive, a variable speed drive, or an adjustable speed drive. The technology has been around for quite a few years but only has started to make some headway in HVAC and pumping applications in the last several years. The size and cost of electronics has made frequency inverters applicable to a wider range of motors and increased the opportunity for savings.
All frequency inverters are going to take 3 phase AC power and convert that 3 phase power to DC power inside the drive and pulse it out in a simulated AC wave form to the motor. The motor still thinks it has AC power but the DC power conversion now lets us control the speed of the motor without harming it. Now we are in control to save energy and money.
The basic concept with the savings for frequency inverters is your speed and your flow are more or less proportional. But the energy consumption is cubed. If you're running your motor at full speed 60 Hertz, you don't have any savings- but any reduction pays the reduction cubed.
4# boiler (75t) of coal gangue plant of circulating flow bed boiler. Technics of boiler is following: burning is low temperature burning. Fuel is delivered to boiler chamber by coal feed system. Primary air entrances to fire box from air distributor bottom, ensuring material fluidization. The secondary air entrances along height class, increasing oxygen to ensure full burning. Materials of fire box vibrate intensively by fluidization air action. Part of solid materials are brought to boiler chamber by high speed air flow. Some big granules flow along chamber inside by gravitation. Some small granules entrance material separator following flue gas. Gas and solid are forming inside chamber. After separation of solid and gas, granules left return to fire box. Gas separated leaves boiler. Because boiler has separator of high efficiency, granules left return to chamber. Ash concentration of chamber is high. Circulating flow bed boiler differs from common boiler which only has radiation heat transfer. Circulating flow bed boiler also has other heat transfer modes such as convection, which heightens heat transfer coefficient of chamber greatly, ensures boiler to reach rated output. Circulating flow bed boiler has low requirement for coal quality. Its pollution material discharging is very low. So it is boiler of environmental protection which is promoted widely by state.
Introduction of reconstruction
1) Parameters
a. mill fan: 2
b. parameters of mill fan
Motor parameters
c. Work parameters: air flow of single fan 48000 m3/h, yearly work time 5850h. Average current is 40A when motor runs in direct on line.
d. Power price: 0.24 Yuan /kWh
2) Equipment after reconstruction
The system is composed of inverter and bypass cabinet. In above figure, QS1, QS2 and QS3 are all in bypass cabinet. QF and M are original equipment.
The system has switch function between line frequency and variable frequency. QS2 and QS3 cannot close together. They are mechanical interlock. During variable frequency operation, QS1 and QS2 close, QS3 opens. During line frequency operation, QS3 closes, QS1 and QS2 open.
3. Mill fan Technics
Mill fan is installed behind of ball mill, raw powder separator and fine powder separator. In ball mill, raw coal mixes with hot air and recycle air from outlet of mill fan. Raw coal is dried and grindered into coal powder. With negative air flow produced by mill fan, fine powder separator separates air from powder. Coal powder drops in warehouse as storage. Residual gas contains 5~10% mixture of air and powder. It is delivered to furnace as tertiary air, or mixes with coal powder left as primary air. Mixture is delivered to furnace. From above processes, we see mill fan provides negative pressure for system. After reconstruction with frequency inverter, outlet gate of mill fan is full open. Meanwhile, adjust outlet gate appropriately. It can meet requirement of providing negative pressure completely, without affection on tertiary air.
1) Parameters
a. mill fan: 2
b. parameters of mill fan
Model | M6-31No20D | Rated flow (qv, max) | 78000 m3/h |
Rated pressure (Pa) | 13235 | speed (NO) | 1450 r/min |
Motor parameters
Model | Y5601-4 | Rated voltage (UO) | 6000V |
Rated power (Pdn) | 630kW | Efficiency (η) | 96% |
Rated current (IO) | 71A | Power factor (cosФ) | 0.87 |
speed (NO) | 1485r/min | | |
c. Work parameters: air flow of single fan 48000 m3/h, yearly work time 5850h. Average current is 40A when motor runs in direct on line.
d. Power price: 0.24 Yuan /kWh
2) Equipment after reconstruction
The system is composed of inverter and bypass cabinet. In above figure, QS1, QS2 and QS3 are all in bypass cabinet. QF and M are original equipment.
The system has switch function between line frequency and variable frequency. QS2 and QS3 cannot close together. They are mechanical interlock. During variable frequency operation, QS1 and QS2 close, QS3 opens. During line frequency operation, QS3 closes, QS1 and QS2 open.
3. Mill fan Technics
Mill fan is installed behind of ball mill, raw powder separator and fine powder separator. In ball mill, raw coal mixes with hot air and recycle air from outlet of mill fan. Raw coal is dried and grindered into coal powder. With negative air flow produced by mill fan, fine powder separator separates air from powder. Coal powder drops in warehouse as storage. Residual gas contains 5~10% mixture of air and powder. It is delivered to furnace as tertiary air, or mixes with coal powder left as primary air. Mixture is delivered to furnace. From above processes, we see mill fan provides negative pressure for system. After reconstruction with frequency inverter, outlet gate of mill fan is full open. Meanwhile, adjust outlet gate appropriately. It can meet requirement of providing negative pressure completely, without affection on tertiary air.
Scheme selection
In order to save cost, we considered to use hydraulic coupling ever. But we finally gave up this method as its much maintenance, long installation period. After research, considering advanced technology and mature product, we decide to use medium voltage inverter. In several inverter brands such as ABB, Gozuk, Siemens, we decide to use Gozuk inverter because of its advanced technology and the cost-effective.
Model selection
1) Motor is 6kV/450kW. The frequency inverter current is a key parameter. The inverter capacity is designed according to motor rated current and max current. So inverter should meet following conditions:
η: efficiency 0.85
cosφ: power factor 0.75
Um: voltage
Im: current
K: revised coefficient of current waveform (1.05~1.1).
Pcn:inverter capacity (KVA). Icn:inverter rated current(A).
2) connecting method: one drive one bypass circuit
3) Control principle: PLC implements pressure PI control, ensures pipe pressure constant, outputs 4~20mA signal to inverter to implement auto control of speed. Equip upper PC on inverter. Install upper PC in control room, start/stop, adjust inverter through upper PC. Frequency inverter data and state shows in upper PC.
4) Link lock protection of isolator, inlet valve, outlet valve and pump fault.
5) Set over current protection, low speed protection.
6) Protection action: by PLC.
In order to save cost, we considered to use hydraulic coupling ever. But we finally gave up this method as its much maintenance, long installation period. After research, considering advanced technology and mature product, we decide to use medium voltage inverter. In several inverter brands such as ABB, Gozuk, Siemens, we decide to use Gozuk inverter because of its advanced technology and the cost-effective.
Model selection
1) Motor is 6kV/450kW. The frequency inverter current is a key parameter. The inverter capacity is designed according to motor rated current and max current. So inverter should meet following conditions:
Pcn≥(KPm)/(ηcosφ) (KVA)Pm: output power
Icn≥KIm (A)
Pcn≥K√3UmIm*10-3 (KVA)
η: efficiency 0.85
cosφ: power factor 0.75
Um: voltage
Im: current
K: revised coefficient of current waveform (1.05~1.1).
Pcn:inverter capacity (KVA). Icn:inverter rated current(A).
2) connecting method: one drive one bypass circuit
3) Control principle: PLC implements pressure PI control, ensures pipe pressure constant, outputs 4~20mA signal to inverter to implement auto control of speed. Equip upper PC on inverter. Install upper PC in control room, start/stop, adjust inverter through upper PC. Frequency inverter data and state shows in upper PC.
4) Link lock protection of isolator, inlet valve, outlet valve and pump fault.
5) Set over current protection, low speed protection.
6) Protection action: by PLC.
I have a 100 HP (75 kW) 1500 RPM motor in a sugar mill, operating a TurboRotor. The motor is oversized due to the large torque it needs to apply to start the turbo rotor, there is no solution to this problem because the motor was sold integrated in the machinery.
However, the motor can be equipped with an inverter because the load of sugar is intermittent. When the silo needs sugar a valve opens and feeds the turbo rotor, during which the electric motor consumes 40,5 kW, when the silo is full the valve closes and the motor keeps operating in "No Load" consuming 33,8 kW. It isn't profitable to turn off the motor because it takes too long to start and it would result in damage to it.
Therefore I decided to use an inverter to control the speed for the "Load- no Load" problem. Can you help me with the detailed energy savings part, because I am used to calculating for Pumps but this is a different situation.
However, the motor can be equipped with an inverter because the load of sugar is intermittent. When the silo needs sugar a valve opens and feeds the turbo rotor, during which the electric motor consumes 40,5 kW, when the silo is full the valve closes and the motor keeps operating in "No Load" consuming 33,8 kW. It isn't profitable to turn off the motor because it takes too long to start and it would result in damage to it.
Therefore I decided to use an inverter to control the speed for the "Load- no Load" problem. Can you help me with the detailed energy savings part, because I am used to calculating for Pumps but this is a different situation.
This paper makes a comparison between the inverter and hydraulic coupling by introducing the methods and principles of inverter, analyses the situation of fans and pumps in term of energy saving. We think the inverter control program is matured, its energy saving is obviously. Inverter will be widely used in various power plants.
Variable frequency control inverter is a new electric drive and it has rapid development in twentieth century, mainly used in AC motor speed control. Its technology and performance are better than any other kind of speed control mode (such as: Voltage Step-down speed control, pole changing speed control, slip speed control, internal feedback cascade speed control and hydraulic coupling). The inverter speed control has a great acceptance in broad users as its remarkable energy saving, high-precision speed control, wide adjustment range,faultless power electronics protection, as well as easy implementation of the automatic communication function. Inverter also brings great convenience to user in safe operation, reliable installation, maintenance etc, which makes domestic and foreign enterprises adopt best choice of energy-saving method for motor.
Principle
As we know, the relationships of speed (N), flow(Q), pressure(H) and power(P) is as follows:
Variable frequency control inverter is a new electric drive and it has rapid development in twentieth century, mainly used in AC motor speed control. Its technology and performance are better than any other kind of speed control mode (such as: Voltage Step-down speed control, pole changing speed control, slip speed control, internal feedback cascade speed control and hydraulic coupling). The inverter speed control has a great acceptance in broad users as its remarkable energy saving, high-precision speed control, wide adjustment range,faultless power electronics protection, as well as easy implementation of the automatic communication function. Inverter also brings great convenience to user in safe operation, reliable installation, maintenance etc, which makes domestic and foreign enterprises adopt best choice of energy-saving method for motor.
Principle
As we know, the relationships of speed (N), flow(Q), pressure(H) and power(P) is as follows:
Q1/ Q2=n1/n2From above, if other operating conditions remain unchanged, through reducing motor speed, energy-saving effect is very remarkable. For example, working condition only demands 50% flow, personnel can adjust speed to half of rated. Power consumption is only 12.5% of rated value, that is, theoretically, energy saving rate can reach to 87.5%.
H1/ H2=(n1/n2)2
P1/ P2=(n1/n2)3
Power factor is a measurement of reactive power. Reactive power is the VA used to establish the magnetic field in a motor. For permanent magnet motor, most time you see power factor being unity, which means all VAs are used to generate torque (minus the loss, of course). Under the condition of field weakening operation though, you will see the PM motor gets less than unity power factor because some VAs are used to counter the perm magnet field. In induction motor, the power factor indicates the portion of VAs used to generate the field comparing to the VAs that generate torque (and loss), which is related to the v/hz in scalar controller or Id in vector control. So under light load condition, you can improve the power factor of an induction motor by lowering the field a bit.
The motor power factor does not make a big difference other than giving an idea of loading. In regards to the inverter fixing power factor everyone is mostly correct. An inverter will always show a DPF (Displacement Power Factor) near unity. DPF is what a utility company traditionally monitors and is the measure of lag looking at current and voltage of power at 60hz or fundamental only. The true power factor on an frequency inverter will change with loading etc and includes current and voltage inclusive of harmonics.
The motor power factor does not make a big difference other than giving an idea of loading. In regards to the inverter fixing power factor everyone is mostly correct. An inverter will always show a DPF (Displacement Power Factor) near unity. DPF is what a utility company traditionally monitors and is the measure of lag looking at current and voltage of power at 60hz or fundamental only. The true power factor on an frequency inverter will change with loading etc and includes current and voltage inclusive of harmonics.
Tags: Definition, Energy saving
Energy saving using inverter is always vary application to application. Following points you need to consider before using inverters for energy saving.
Energy savings as it relates to frequency inverters as above explained. My technology uses negative amp draw to develop the torque in our motors, the traditional amp draw is blocked bi-directionally by our power electronics. Hence, our electric power consumption neutralization platform is an electric power production and a power performance platform as opposed to an inverter energy savings and performance sacrificing platform.
- How much process flow and pressure requirement through AC motors
- Existing control methodology like control valve in pumps, Damper or guide vane for Fans & Blowers etc. and position of the valve or dampers
- If you have process flow and pressure data and pump or fan design data, you can calculate energy saving using affinity law
- Loading and Unloading cycle for compressor application. If the unloading time is higher for compressor application, you will get better energy saving
- Using affinity law, you can calculate the energy saving with consideration of inverter losses. With this you can calculate the Pay back of inverters.
Energy savings as it relates to frequency inverters as above explained. My technology uses negative amp draw to develop the torque in our motors, the traditional amp draw is blocked bi-directionally by our power electronics. Hence, our electric power consumption neutralization platform is an electric power production and a power performance platform as opposed to an inverter energy savings and performance sacrificing platform.
Tags: inverter, Energy saving
With the development of economy, energy saving and emission reduction
are key points in future. Technology of medium voltage variable
frequency is promoted increasingly. This paper demonstrates inverter
design, electrical connecting, thermal control logic configuration,
commissioning and benefits in condenser pump.
Equipment parameters
Condensing water system is middle pressure system, equipped with condenser pump. Parameters are following:
Operation state before reform
Condensing pump runs in constant speed. After being boosted pressure by pump, condensing water passes through axes and governing valve (inlet gate of deaerator, serial No C-1), then enters into deaerator. Condensing flow is controlled by governing valve opening to maintain stability of water level of deaerator. In addition, condensing water is also supplied to other auxiliary equipments. In order to avoid condensing system superpressure and cavitation during operation in low load, we design recycle pipeline. (see following figure).
Circulating governing valve C-2 cooperates with C-1 to adjust water level of deareator, keeps normal pressure for system.
Equipment parameters
Condensing water system is middle pressure system, equipped with condenser pump. Parameters are following:
Motor parameters | |||||
Model | YLKK500--4 | Rated voltage (U0) | 6kV | Cooling mode G | Q161 |
Rated power (Pdn) | 1120kW | Speed (n0) | 1491r/min | Insulation class | F |
Rated current (I0) | 124.7A | Power factor | 0.901 | IP class | IP54 |
Condenser pump parameters | |||||
Rated flow | 912.98m3/h | Rated speed | 1480r/min | Rated lift | 258.4m |
Power | 1120kW | Model | NLT350 - 400*6 |
Operation state before reform
Condensing pump runs in constant speed. After being boosted pressure by pump, condensing water passes through axes and governing valve (inlet gate of deaerator, serial No C-1), then enters into deaerator. Condensing flow is controlled by governing valve opening to maintain stability of water level of deaerator. In addition, condensing water is also supplied to other auxiliary equipments. In order to avoid condensing system superpressure and cavitation during operation in low load, we design recycle pipeline. (see following figure).
Circulating governing valve C-2 cooperates with C-1 to adjust water level of deareator, keeps normal pressure for system.