[Daily Question 20090222] In what equipment is the frequency converter more energy-saving when used? Why?

I think it's very unprofessional. For example, you talked about computers and win. Where is the xp operating system used? Can't answer?? Haha. PLC is a means of operation, a combination of software and hardware. You can use PLC to control the inverter. Of course, PLC can also be used to control other things, and inverters generally act on motors, three-phase asynchronous motors, etc... Main It is a machine used to reduce or increase the voltage and current by changing the frequency of the power grid. Therefore, the inverter can be used wherever there is a motor, such as large fans, power grids, wire drawing machines, etc... Although the inverter can be operated by PLC, the inverter can also be controlled in other ways, with special keyboards and other tools...

In places where the process system requires constant voltage and constant current, the old method is to use cycle adjustment or throttling. In this case, it is more energy-saving to use a frequency converter to automatically adjust. Such as constant pressure water supply, gas supply system, etc.

Generally speaking, the energy-saving effect of pumps used in variable torque load fans and pumps is more obvious than that of constant torque loads. This is based on the physical characteristics of the load, because the output power of fans and pumps is P=KN3, and the constant torque load power is p=KTN. where P is the power ； N is the rotation speed ； T is torque. That is, the output power of variable torque fans and pumps is proportional to the cube of the rotational speed, while the power of the constant torque load is proportional to the first power of the rotational speed. Of course, there are exceptions, such as Roots blowers.

1. Frequency conversion energy saving can be known from fluid mechanics, P (power) = Q (flow) ╳ H (pressure), the flow rate Q is proportional to the square of the rotation speed N, the pressure H is proportional to the square of the rotation speed N, the power P is proportional to the cube of the rotation speed N. If the efficiency of the water pump is certain, when the flow rate is required to decrease, the rotation speed N can decrease proportionally, and at this time the shaft output power P decreases in a cube relationship. That is, the relationship between the power consumption of the water pump motor and the rotation speed is approximately a cubic ratio. For example: The power of a water pump motor is 55KW. When the speed drops to 4/5 of the original speed, the power consumption is 28.16KW, saving 48.8%. When the speed drops to 1/2 of the original speed, the power consumption is 6.875KW, saving 87.5% of power. 2. Power factor compensation energy-saving reactive power not only increases line losses and equipment heating, but more importantly, the reduction in power factor leads to a reduction in the active power of the grid. A large amount of reactive power is consumed in the lines, the equipment usage efficiency is low, and the waste is serious. According to the formula P=S╳COSФ, Q=S╳SINФ, where S-apparent power, P-has Active power, Q - reactive power, COSФ - power factor. It can be seen that the greater the COSФ, the greater the active power P. The power factor of an ordinary water pump motor is between 0.6-0.7. After using the frequency conversion speed regulating device, due to the effect of the filter capacitor inside the frequency converter, COSФ≈1, thus reducing the reactive power loss and increasing the active power of the power grid. 3. Soft start energy saving. Since the motor is started directly or Y/D, the starting current is equal to (4-7) times the rated current. This will have a serious impact on the electromechanical equipment and the power supply grid, and will also require too high grid capacity. The large current and vibration generated during startup will cause great damage to the baffles and valves, and are extremely detrimental to the service life of the equipment and pipelines. After using the variable frequency energy-saving device, the soft start function of the frequency converter will make the starting current start from zero, and the maximum value will not exceed the rated current, which reduces the impact on the power grid and the requirements for power supply capacity, and extends the service life of the equipment and valves. Saves equipment maintenance costs.

In situations where the flow needs to be adjusted frequently and the adjustment range is relatively large, a frequency converter can be used instead of a regulating valve to control the flow. Since the pressure drop in the pipeline caused by the use of regulating valves is reduced, it is more energy-saving. At present, many control loops have both regulating valves and frequency converters.

1. Frequency conversion energy saving can be known from fluid mechanics, P (power) = Q (flow) ╳ H (pressure), the flow rate Q is proportional to the square of the rotation speed N, the pressure H is proportional to the square of the rotation speed N, the power P is proportional to the cube of the rotation speed N. If the efficiency of the water pump is certain, when the flow rate is required to decrease, the rotation speed N can decrease proportionally, and at this time the shaft output power P decreases in a cube relationship. That is, the relationship between the power consumption of the water pump motor and the rotation speed is approximately a cubic ratio. For example: The power of a water pump motor is 55KW. When the speed drops to 4/5 of the original speed, the power consumption is 28.16KW, saving 48.8%. When the speed drops to 1/2 of the original speed, the power consumption is 6.875KW, saving 87.5% of power. 2. Power factor compensation energy-saving reactive power not only increases line losses and equipment heating, but more importantly, the reduction in power factor leads to a reduction in the active power of the grid. A large amount of reactive power is consumed in the lines, the equipment usage efficiency is low, and the waste is serious. According to the formula P=S╳COSФ, Q=S╳SINФ, where S-apparent power, P-has Active power, Q - reactive power, COSФ - power factor. It can be seen that the greater the COSФ, the greater the active power P. The power factor of an ordinary water pump motor is between 0.6-0.7. After using the frequency conversion speed regulating device, due to the effect of the filter capacitor inside the frequency converter, COSФ≈1, thus reducing the reactive power loss and increasing the active power of the power grid. 3. Soft start energy saving. Since the motor is started directly or Y/D, the starting current is equal to (4-7) times the rated current. This will have a serious impact on the electromechanical equipment and the power supply grid, and will also require too high grid capacity. The large current and vibration generated during startup will cause great damage to the baffles and valves, and are extremely detrimental to the service life of the equipment and pipelines. After using the variable frequency energy-saving device, the soft start function of the frequency converter will make the starting current start from zero, and the maximum value will not exceed the rated current, which reduces the impact on the power grid and the requirements for power supply capacity, and extends the service life of the equipment and valves. Saves equipment maintenance costs.

We generally use it on motors. In order to adjust pipeline flow, when the motor is not required to operate at full load, the regulating valve can be fully opened and the frequency converter can be used to control the flow.

When the load of the pump changes frequently, it is meaningless to use a frequency converter to control it because the load remains unchanged.

Fans or water pumps that need to control flow and save energy space are required. Use frequency converter control instead of regulating valve control. reason: When the regulating valve is controlled, the fan or water pump is running at full load, and the flow is controlled by adjusting the regulating valve. This is undoubtedly not energy-saving. ； If you switch to a frequency converter, you can adjust the speed and reduce the motor load to adjust the outlet flow of the fan or water pump to achieve energy saving.

Usually in industrial production and product processing manufacturing, blower equipment is mainly used in boiler combustion systems, drying systems, cooling systems, ventilation systems and other occasions. According to production needs, furnace pressure, wind speed, air volume, temperature and other indicators are controlled and adjusted to adapt to process requirements and operating conditions. The most commonly used control method is to adjust the opening of the damper and baffle to adjust the controlled object. In this way, regardless of the size of the production demand, the fan must run at full speed, and changes in operating conditions cause energy to be consumed through the throttling loss of the damper and baffle. In the production process, not only is the control accuracy limited, but it also causes a lot of energy waste and equipment loss. This results in increased production costs, shortened equipment service life, and high equipment maintenance and repair costs. Pump equipment also has broad application space in the production field. Water lifting pump stations, pool storage tank supply and drainage systems, industrial water (oil) circulation systems, and heat exchange systems all use centrifugal pumps, axial flow pumps, gear pumps, plunger pumps and other equipment. Moreover, according to different production needs, throttling devices such as adjustment valves, return valves, and stop valves are often used to control signals such as flow, pressure, and water level. This not only causes a lot of energy waste, but also damages the sealing performance of pipelines, valves, etc. ； It also accelerates the wear and cavitation of the pump chamber and valve body, and in serious cases damages the equipment, affects production, and endangers product quality. Most fans and pumps are driven directly by asynchronous motors, which have shortcomings such as large starting current, mechanical impact, and poor electrical protection characteristics. Not only does it affect the service life of the equipment, but it also cannot act instantly to protect the equipment when a mechanical failure occurs on the load. The pump is often damaged and the motor is burned out. In recent years, due to the urgent need for energy saving and the continuous improvement of product quality, coupled with the use of variable frequency speed regulators (referred to as frequency converters), they are easy to operate, maintenance-free, have high control accuracy, and can achieve high functionality. ； Therefore, the inverter-driven solution began to gradually replace the control solution of dampers, baffles, and valves. The basic principle of variable frequency speed regulation technology is based on the relationship between motor speed and working power input frequency.: n=60f (1-s)/p, (where n, f, s, and p respectively represent the rotation speed, input frequency, motor slip rate, and the number of motor magnetic pole pairs) ； The purpose of changing the motor speed is achieved by changing the motor operating power frequency. The frequency converter is a comprehensive electrical product that uses AC-DC-AC power conversion technology, power electronics, microcomputer control and other technologies based on the above principles. It can be known from the basic laws of fluid mechanics that: Fans and pumps are all square torque loads, and their rotational speed n has the following relationship with flow rate Q, pressure H and shaft power P: Q∝n, H∝n2, P∝n3 ； That is, the flow rate is proportional to the rotation speed, the pressure is proportional to the square of the rotation speed, and the shaft power is proportional to the cube of the rotation speed. Taking a water pump as an example, its outlet pressure head is H0 (the outlet pressure head is the static pressure difference between the pump inlet and the pipeline outlet), the rated speed is n0, the pipe resistance characteristic when the valve is fully open is r0, the corresponding pressure under rated operating conditions is H1, and the outlet flow rate is Q1. The flow-speed-pressure relationship curve is shown in the figure below. In on-site control, the water pump is usually used to operate the outlet valve at a fixed speed to control the flow. When the flow rate decreases by 50% from Q1 to Q2, the valve opening decreases, causing the pipe network resistance characteristics to change from r0 to r1, and the system operating point moves from the original point A to point B along direction I. ； Due to its throttling effect, the pressure H1 changes to H2. The actual value of the water pump shaft power (kW) can be calculated by the formula: P=Q·H／(ηc·ηb)×10-3 is obtained. Among them, P, Q, H, etac, and etab respectively represent power, flow, pressure, water pump efficiency, and transmission device efficiency. Direct transmission is 1. Assuming that the total efficiency (ηc·ηb) is 1, when the water pump moves from point A to point B, the power consumption saved by the motor is the area difference between AQ1OH1 and BQ2OH2. If speed regulation is used to change the speed n of the water pump, when the flow rate decreases by 50% from Q1 to Q2, then the pipe network resistance characteristics will be the same curve r0, and the system working point will move from the original point A to point C along direction II, and the operation of the water pump will become more reasonable. When the valve is fully open and there is only pipe network resistance, the system meets the on-site flow requirements and energy consumption is bound to be reduced. At this time, the power consumption saved by the motor is the area difference between AQ1OH1 and CQ2OH3. Comparing the use of valve opening adjustment and water pump speed control, it is obvious that using water pump speed control is more effective and reasonable, and has significant energy-saving effects. In addition, it can be seen from the figure: When the valve is adjusted, the system pressure H will increase, which will threaten and damage the sealing performance of the pipeline and valve. ； When the speed is adjusted, the system pressure H will decrease as the pump speed n decreases, so it will not have a negative impact on the system. It is not difficult to conclude from the above comparison that: When the on-site demand for water pump flow drops from 100% to 50%, the use of speed adjustment will save the power corresponding to BCH3H2 compared with the original valve adjustment, and the energy saving rate is more than 75%. Similarly, if frequency conversion speed regulation technology is used to change the speed of pumps and fans to control on-site pressure, temperature, water level and other process control parameters, the above comparison results can also be obtained by drawing a relationship curve based on the system control characteristics. That is to say, using variable frequency speed regulation technology to change the motor speed is more energy-saving and economical than using valves and baffles to adjust, and the operating conditions of the equipment will also be significantly improved.

Frequency conversion does not save power everywhere, and there are many occasions where using frequency conversion does not necessarily save power. As an electronic circuit, the frequency converter itself also consumes power (about 3-5% of the rated power). A 1.5-horsepower air conditioner consumes 20-30W of electricity, which is equivalent to a continuous light. It is a fact that the inverter runs at the power frequency and has a power-saving function. But his prerequisite is: First, high power and fan/pump load ； Second, the device itself has a power-saving function (software support) ； Third, long-term continuous operation. These are the three conditions that reflect the power saving effect. Other than that, it doesn't matter whether it saves electricity or not, it doesn't make much sense.

The original poster’s questions are not complicated, but the answers behind them are very good.

Motors above 100KW are used in operating equipment that requires frequent flow adjustment.

Energy-saving principle of variable frequency speed regulation energy-saving device 1. Frequency conversion energy-saving can be known from fluid mechanics, P (power) = Q (flow) ╳ H (pressure), the flow rate Q is proportional to the square of the rotation speed N, the pressure H is proportional to the square of the rotation speed N, the power P is proportional to the cube of the rotation speed N. If the efficiency of the water pump is constant, when the flow rate is required to decrease, the rotation speed N can decrease proportionally, and at this time the shaft output power P decreases in a cube relationship. That is, the relationship between the power consumption of the water pump motor and the rotation speed is approximately a cubic ratio. For example: The power of a water pump motor is 55KW. When the speed drops to 4/5 of the original speed, the power consumption is 28.16KW, saving 48.8%. When the speed drops to 1/2 of the original speed, the power consumption is 6.875KW, saving 87.5% of power. 2. Power factor compensation energy-saving reactive power not only increases line losses and equipment heating, but more importantly, the reduction in power factor leads to a reduction in the active power of the grid. A large amount of reactive power is consumed in the lines, the equipment usage efficiency is low, and the waste is serious. According to the formula P=S╳COSФ, Q=S╳SINФ, where S-apparent power, P-has Active power, Q - reactive power, COSФ - power factor. It can be seen that the greater the COSФ, the greater the active power P. The power factor of an ordinary water pump motor is between 0.6-0.7. After using the frequency conversion speed regulating device, due to the effect of the filter capacitor inside the frequency converter, COSФ≈1, thus reducing the reactive power loss and increasing the active power of the power grid. 　　3. Soft start energy saving. Since the motor is started directly or Y/D, the starting current is equal to (4-7) times the rated current. This will have a serious impact on the electromechanical equipment and the power supply grid, and will also require too high grid capacity. The large current and vibration generated during startup will cause great damage to the baffles and valves, and are extremely detrimental to the service life of the equipment and pipelines. After using the variable frequency energy-saving device, the soft start function of the frequency converter will make the starting current start from zero, and the maximum value will not exceed the rated current, which reduces the impact on the power grid and the requirements for power supply capacity, and extends the service life of the equipment and valves. Saves equipment maintenance costs. 　　It is an indelible fact that the frequency converter can save electricity. In some cases, it can save more than 40% of electricity, but in some cases it will be more wasteful than not connecting the frequency converter! 　　The inverter achieves energy saving by reducing voltage at light loads. Since the speed of the drag torque load does not change much, even if the voltage is reduced, it will not be much, so the energy saving is very weak. However, it is different when used in a fan environment. When a smaller air volume is required, the motor will reduce its speed. We know that the energy consumption of the fan is proportional to the 1.7th power of the speed, so the motor's torque will drop sharply, and the energy saving effect is obvious. If we use it on an oil well, a lot of electric energy will be wasted by using the braking resistor on the return journey, which will result in even more waste electricity. 　　Of course, if the environment requires speed regulation, the energy-saving effect of the inverter is still relatively obvious. When the speed is not adjusted, the inverter will not save power and can only improve the power factor. 　　1. If two identical motors both work at a power frequency of 50HZ, one uses an inverter and the other does not, and both the speed and torque are at the motor's rated condition, can the inverter still save power? How much can you save? 　　answer: In this case, the frequency converter can only improve the power factor but cannot save power. 　　2. If the torque of the two motors does not reach the rated torque of the motor (the frequency and speed are still the same 50HZ), how much power can the one with an inverter save? 　　answer: If automatic energy-saving operation is used, the inverter can run at reduced voltage at this moment, which can save some power, but the power saving is not obvious. 　　3. Under the same conditions, how much can be saved in the no-load state? Which of the three states saves more? 　　answer: The no-load state of the drag type load cannot save much electric energy.

Agree with the second floor, a little bit about the law of conservation of energy. Only what is wasted can be saved. What constant pressure should be managed? The inverter is not a generator!

In situations where loads such as pumps and fans often change, energy saving is crucial for high-power equipment.: The effect is obvious.

Frequency conversion does not save power everywhere, and there are many occasions where using frequency conversion does not necessarily save power. As an electronic circuit, the frequency converter itself also consumes power (about 3-5% of the rated power). A 1.5-horsepower air conditioner consumes 20-30W of electricity, which is equivalent to a continuous light. It is a fact that the inverter runs at the power frequency and has a power-saving function. But his prerequisite is: First, high power and fan/pump load ； Second, the device itself has a power-saving function (software support) ； Third, long-term continuous operation. These are the three conditions that reflect the power saving effect. Other than that, it doesn't matter whether it saves electricity or not, it doesn't make much sense. Only for motors above 100KW, operating equipment that requires frequent flow adjustment is required.

To put it simply, it is used on high-power motors, and the control parameters need to be adjusted in a wide range.

Generally speaking, the energy-saving effect of pumps used in variable-torque load fans and pumps is more obvious than that of constant-torque loads. This is based on the physical characteristics of the load, because the output power of fans and pumps is P=KN3, and the constant torque load power is p=KTN. where P is the power ； N is the rotation speed ； T is torque. That is, the output power of variable torque fans and pumps is proportional to the cube of the rotational speed, while the power of the constant torque load is proportional to the first power of the rotational speed. Of course, there are exceptions, such as Roots blowers.