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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
I have an application that require running an 55Kw high efficiency induction motor at rated torque at any rpm from 5% to 100% of the rated rpm. It will be controlled by a frequency inverter with FOC.
This motor has independent cooling fan running with a separate motor that is capable of removing 5Kw heat from the motor. It will be controlled by an inverter with FOC. The motor is a good 95% efficient with cast copper rotor / not the regular cast aluminum. Can an induction motor give out full torque at 5% of its rated rpm with an inverter?? My concern is it may over heat at low frequency - not due to cooling fan because that is independent, but due to the other reasons.
This motor has independent cooling fan running with a separate motor that is capable of removing 5Kw heat from the motor. It will be controlled by an inverter with FOC. The motor is a good 95% efficient with cast copper rotor / not the regular cast aluminum. Can an induction motor give out full torque at 5% of its rated rpm with an inverter?? My concern is it may over heat at low frequency - not due to cooling fan because that is independent, but due to the other reasons.
Computation delay in digital systems translates to additional phase loss. This phase loss at any frequency f is given by 360*f/fs, where fs is the digital loop sampling frequency. So if we can maintain high fs compared to the bandwidth fc then the phase margin reduction caused by the delay at the crossover frequency (fc) is minimized. This also means that for high BW digital system the delay must be minimized as Ron entioned.
Digital gives some advantage while closing some loops. For ex, UPS output voltage loop the integrator in the compensator can be changed to provide high gain at the UPS output frequency and not necessarily at DC. For high Q buck, digital allows for better loop response by use of complex zero compensation. This can also be used in PFC current loop or Solar inverter current loop with LCL type output filter.
Digital gives some advantage while closing some loops. For ex, UPS output voltage loop the integrator in the compensator can be changed to provide high gain at the UPS output frequency and not necessarily at DC. For high Q buck, digital allows for better loop response by use of complex zero compensation. This can also be used in PFC current loop or Solar inverter current loop with LCL type output filter.
Tags: inverter
This is a recurring question for me in my Soar Academy classes and is
gaining traction. I want to add that the SMA Sunny Island can be used
with any solar/wind inverter regardless of make. SMA is coming out with
our own micro inverter after SPI and it will be able to be used with the
SI45/50/6048U inverters, although initially, it will not respond to the
Sunny Island frequency shifts.
That being said, the only issue with a non-SMA inverter will occur when the following three conditions exists:
1. The grid is out (or in a standalone system)
2. The batteries are fully topped off
3. There is no demand on the protected loads panel
If these three conditions are met, the Sunny Island will increase the micro grid frequency to throttle the RE inverters down to 0W to prevent battery overcharge. With a non-SMA inverter, it will not respond to these frequency shifts and as soon as the frequency hits the UL1741 limit of 60.5Hz it will immediately disconnect from the grid. Worst case, you will have to wait 5 minutes when the Island recognizes a demand and the isolation relays in the inverters will be overexercised. Not a big deal really.
That being said, the only issue with a non-SMA inverter will occur when the following three conditions exists:
1. The grid is out (or in a standalone system)
2. The batteries are fully topped off
3. There is no demand on the protected loads panel
If these three conditions are met, the Sunny Island will increase the micro grid frequency to throttle the RE inverters down to 0W to prevent battery overcharge. With a non-SMA inverter, it will not respond to these frequency shifts and as soon as the frequency hits the UL1741 limit of 60.5Hz it will immediately disconnect from the grid. Worst case, you will have to wait 5 minutes when the Island recognizes a demand and the isolation relays in the inverters will be overexercised. Not a big deal really.
Tags: inverter, Micro inverter
Single phase inverter normally is used in 200V AC to 240V AC in low
power applications, like small pumps. The AC motor's input need to be
three phase as all of the inverters are three phase output. In our
factory, the 1 phase inverters power is from 0.5HP to 3HP.
This single phase inverter is the updated generation driver. Due to the new technology being used in the inverters, this single phase inverter is in high performance & more stable against the old one. Also, the updated 1 phase inverter which is manufacturing by Gozuk in China, has inherit the advantage features, like vector control, RS 485 communication, powerful overload ability and much more.
Single phase inverter features
This single phase inverter is the updated generation driver. Due to the new technology being used in the inverters, this single phase inverter is in high performance & more stable against the old one. Also, the updated 1 phase inverter which is manufacturing by Gozuk in China, has inherit the advantage features, like vector control, RS 485 communication, powerful overload ability and much more.
Single phase inverter features
- Input voltage: 1 phase 220V, 230V, 240V
- Output voltage: 3 phase rated input voltage
- Power range: 0.4kW to 2.2kW
- Vector control single phase inverter
- Multiple programmable multi-function input/output terminals
- Special speed tracking function without impact
- Rich fault protection and operation monitoring function
- 32 bit high speed CPU special for AC motor control
- Low frequency with high start torque: 0.5Hz/150%
- Simple PLC with multi-step control function
- Built-in brake unit
- Offer RS485, support MODBUS-RTU communication protocol
- Close-loop control with built-in PID
- Dynamic torque current control, rapid response to load's change
- Load distribution control function
- Online modify and check parameters of the inverters
- Wobble frequency control special for spinning
- Simple servo fixed-length control function
Tags: inverter, Single phase inverter
Most fans and water pumps are selected
according to its full loads working status, but in practice they are not
working at the full load state in most of the time. So to control flow
& air volume of the pumps & fans, it needs a wind deflector,
reflux valve or start/stop timer usually, and the large power ac motors
are very difficult in start/stop frequently as the electric impact is in
a high level, during this time, it's absolutely will cause electric
energy wasted and high current impact during start/stop of the ac motor.
To solve this kind of problem, the most scientific way is to adopt a Gozuk inverter (AC Drive) to control the fans and water pumps. When the AC motor operates at 80% of its rated rotation speed, in theory, the power consumption is the cube of 80% of its rated power, i.e. 51.2%. Generally, it can almost save 40% power consumption for the manufacturer when deduct the impact of mechanical loss and ac motor copper and iron loss. Plus, it can improve energy-efficient when the fan & pump adopt closed-loop constant-pressure control which can be achieved easily. Due to the inverter can realize soft start/stop for the ac motors, it can avoid voltage surge during the motor's start period to decrease the failure rate and increase its service life, and reduce the power system's capacity requirements and reactive power loss.
Energy Conservation Analysis
Through the fluid mechanics' basic principles, we know the fans and pumps are belong to square torque loads, the rotation speed n, flow Q, pressure H and shaft power P relation: Q?n, H?n2, P?n3, i.e., the flow is in proportion to its rotation speed, the pressure is in proportion to the square of its rotation speed, and the shaft power is in proportion to the cube of its rotation speed.
We now take the fan as an instance of the principle in energy conservation. As show in following fig, when the fan in its rated rotation speed, the air volume and air pressure change as curve 1, which intersects with the pipe network resistance curve 2 at the rated working condition point N when the air door is full opened; the air volume of the fan is Qn and the pressure is Hn. Normally, the working condition point is moved to point E by closing the regulation air door and increasing the resistance in ventilation pipe network. At this moment, the air volume is decreased to Qe and the generated pressure head is He. If the air volume is regulated by reducing the rotation speed of the fan, the fan will operate as curve 4, and re-generate required air volume Qe, it will intersect with the pipe network resistance curve 2 at the working condition point C when the air door is full opened.
To solve this kind of problem, the most scientific way is to adopt a Gozuk inverter (AC Drive) to control the fans and water pumps. When the AC motor operates at 80% of its rated rotation speed, in theory, the power consumption is the cube of 80% of its rated power, i.e. 51.2%. Generally, it can almost save 40% power consumption for the manufacturer when deduct the impact of mechanical loss and ac motor copper and iron loss. Plus, it can improve energy-efficient when the fan & pump adopt closed-loop constant-pressure control which can be achieved easily. Due to the inverter can realize soft start/stop for the ac motors, it can avoid voltage surge during the motor's start period to decrease the failure rate and increase its service life, and reduce the power system's capacity requirements and reactive power loss.
Energy Conservation Analysis
Through the fluid mechanics' basic principles, we know the fans and pumps are belong to square torque loads, the rotation speed n, flow Q, pressure H and shaft power P relation: Q?n, H?n2, P?n3, i.e., the flow is in proportion to its rotation speed, the pressure is in proportion to the square of its rotation speed, and the shaft power is in proportion to the cube of its rotation speed.
We now take the fan as an instance of the principle in energy conservation. As show in following fig, when the fan in its rated rotation speed, the air volume and air pressure change as curve 1, which intersects with the pipe network resistance curve 2 at the rated working condition point N when the air door is full opened; the air volume of the fan is Qn and the pressure is Hn. Normally, the working condition point is moved to point E by closing the regulation air door and increasing the resistance in ventilation pipe network. At this moment, the air volume is decreased to Qe and the generated pressure head is He. If the air volume is regulated by reducing the rotation speed of the fan, the fan will operate as curve 4, and re-generate required air volume Qe, it will intersect with the pipe network resistance curve 2 at the working condition point C when the air door is full opened.
Electrical environment
A. Prevent overvoltage in input terminal
The main circuit of the inverter is consisted of power electronic parts, these devices are very sensitive on the voltage, the over voltage on input terminal will cause permanent damage of the main components. For example, some factories have their own electricity generator, power grid fluctuation is relative high, so they should have precautions on the input voltage of the frequency inverter.
B. Prevent electromagnetic interference
The inverter main electrical components are power module and control system hardware and software circuit, If these components and software programs are impacted by a certain electromagnetic interference, it will cause hardware circuit malfunction, software program failed and then cause accident. So, in order to avoid electromagnetic interference, the variable frequency inverter needs to prevent electromagnetic interference according the electrical environment. For example: the input power cord, output motor lines, control lines shall be kept away from each other; The devices and signal lines which are easily affected, should be installed as far as possible from the frequency inverter; The critical signal lines should be shielded cable, it is recommended to use shield cable with 360° grounded.
A. Prevent overvoltage in input terminal
The main circuit of the inverter is consisted of power electronic parts, these devices are very sensitive on the voltage, the over voltage on input terminal will cause permanent damage of the main components. For example, some factories have their own electricity generator, power grid fluctuation is relative high, so they should have precautions on the input voltage of the frequency inverter.
B. Prevent electromagnetic interference
The inverter main electrical components are power module and control system hardware and software circuit, If these components and software programs are impacted by a certain electromagnetic interference, it will cause hardware circuit malfunction, software program failed and then cause accident. So, in order to avoid electromagnetic interference, the variable frequency inverter needs to prevent electromagnetic interference according the electrical environment. For example: the input power cord, output motor lines, control lines shall be kept away from each other; The devices and signal lines which are easily affected, should be installed as far as possible from the frequency inverter; The critical signal lines should be shielded cable, it is recommended to use shield cable with 360° grounded.
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.
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.
This article introduces inverter principle and its commissioning at
site, analyses energy saving effect and gives reference to understand
inverter operation.
Electrical system is 'one drives one' mode (dashed line parts is the added).
Medium voltage inverter can switch operation mode according to need. For example: mode of one runs in variable frequency and the other runs in direct on line, and mode of the both run in direct on line. The disadvantage is that during switching, load needs to be adjusted. After lowering load, stop 1# (or 2#) ID fan, then switch the operation mode. In normal state, two ID fans run in variable frequency.
Medium voltage inverter has local control and remote control. In remote control, speed signal from DCS trails inverter speed and makes feedback. In local control, remote control is invalid.
There is auto and manual modes when inverter is controlled by DCS. In manual state, personnel controls inverter speed by changing in interface to realize negative pressure adjustment.
Electrical system is 'one drives one' mode (dashed line parts is the added).
Medium voltage inverter can switch operation mode according to need. For example: mode of one runs in variable frequency and the other runs in direct on line, and mode of the both run in direct on line. The disadvantage is that during switching, load needs to be adjusted. After lowering load, stop 1# (or 2#) ID fan, then switch the operation mode. In normal state, two ID fans run in variable frequency.
Medium voltage inverter has local control and remote control. In remote control, speed signal from DCS trails inverter speed and makes feedback. In local control, remote control is invalid.
There is auto and manual modes when inverter is controlled by DCS. In manual state, personnel controls inverter speed by changing in interface to realize negative pressure adjustment.
Tags: inverter
Adjusting
speed of auxiliary equipments such as fan and pump by variable frequency
technology makes each parameter at the best state, which improves
operation, enhances efficiency and saves power, water and coal, reduces
production cost, brings lots of benefits for power plant. Meanwhile,
inverter cooperates with control system of units, which can improve
automatization level, save labour, enhance management level of whole
system.
There are two aspects for inverter development in power plant. One is inverter itself development; the other is how to cooperate with progress of plant production technology and automatization.
For inverter itself development: development in big capacity and small dimension, modularization, voltage withstand and hardware universal are research goals in short time.
For application in power plant: manufacturer should improve inverter self-detection function; restore inverter fault quickly; solve problem of damper and valve quick response; digital connection to central system and so on. Furthermore, anti-dirt, heat, anti-disturbance and reliability should be researched and explored for a better mode.
There are two aspects for inverter development in power plant. One is inverter itself development; the other is how to cooperate with progress of plant production technology and automatization.
For inverter itself development: development in big capacity and small dimension, modularization, voltage withstand and hardware universal are research goals in short time.
For application in power plant: manufacturer should improve inverter self-detection function; restore inverter fault quickly; solve problem of damper and valve quick response; digital connection to central system and so on. Furthermore, anti-dirt, heat, anti-disturbance and reliability should be researched and explored for a better mode.
Tags: inverter, Medium voltage inverter
There are local start/stop and remote start/stop, function set,
parameter set, fault inquiry, operation record on WINDOWS interface.
Set inverter parameters by colorful LED touch-screen. Output operation data table can be printed out. HMI can display voltage/ current waveform, frequency, speed and motor status at any time.
Good ability in detecting and indicating: operation status of every part of inverter can be detected. Integrated fault monitor circuit, accurate fault orientation, fault position and type showing in HMI make fault points clear at a glance. Easy replacement of broken cell reduces MTTR and can be operated by general personnel.
Set inverter parameters by colorful LED touch-screen. Output operation data table can be printed out. HMI can display voltage/ current waveform, frequency, speed and motor status at any time.
Good ability in detecting and indicating: operation status of every part of inverter can be detected. Integrated fault monitor circuit, accurate fault orientation, fault position and type showing in HMI make fault points clear at a glance. Easy replacement of broken cell reduces MTTR and can be operated by general personnel.