Abstract: This article introduces the current status and composition of energy consumption of electrical equipment, and elaborate on the energy-saving principles of frequency conversion and soft start through calculation. It also lists the energy-saving advantages of the inverter in the control of fans and pumps and the process of the motor's soft start to effectively combat the peak voltage of the grid. Keywords: inverter soft start energy saving
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I. Introduction
With the acceleration of industrialization, the form of energy saving and consumption reduction is becoming more and more serious, and some electronic products that can reduce industrial losses are emerging. The application fields of frequency converters and soft starters are getting wider and wider, and their use is becoming more and more frequent. In the control of the motor and fan, the frequency conversion speed regulation and soft start energy saving effect is very obvious.
2. Analysis of power consumption
In order to ensure the reliability of production, all kinds of production machinery have a certain surplus when they are designed with power drives. The motor cannot run under full load. In addition to meeting the power drive requirements, the excess torque increases the consumption of active power and causes waste of electrical energy. During the production process, the fan and pump must be adjusted in real time due to the large range of motor load changes. Traffic. At present, most of the methods for adjusting the flow rate are the adjustment of the adjustment valve. This adjustment method only changes the flow resistance of the channel, and the output power of the motor does not change much. The motor is often running at full speed, and the adjustment valve controls the production through throttling. The need is actually to increase the resistance artificially to achieve the purpose of regulation, this throttling regulation method wastes a lot of electrical energy. When the air volume decreases and the fan speed decreases, its motor input power decreases rapidly. For example, when the air volume drops to 80% and the speed n also drops to 80%, the shaft power drops to 51% of the rated power; if the air volume drops to 50%, the shaft power will drop to 13% of the rated power, and its power saving potential is very large .
When the motor is started at full voltage, due to the need for the motor's starting torque, it is necessary to absorb 7 times the rated current of the motor from the grid, and a large starting current is a waste of power, and the voltage fluctuation of the grid is also greatly damaged, increasing line loss and variable damage. Excessive starting torque produces mechanical impact, which causes large impact on the driven equipment, shortens the service life, and affects accuracy. Such as damage to the coupling, tearing the belt, etc. It causes abnormal wear and impact of mechanical transmission components, accelerates aging, shortens life and increases maintenance workload. The hard start of the motor has a serious impact on the power grid, and it also has too high requirements on the capacity of the power grid. The large current and vibration generated during start-up cause great damage to the baffle and valves, which is extremely unfavorable for the service life of equipment and pipelines. After using the soft start device, using the soft start function of the inverter 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 power supply capacity requirements, and extends the use of equipment and valves life. Save the equipment maintenance costs. When the motor starts, the starting current can be from 0-the rated current of the motor gradually increases, which reduces the impact of the starting current on the grid, saves electricity costs, and reduces the impact of the starting inertia on the high inertia speed of the equipment, extending the service life of the equipment.
Three, frequency conversion energy saving analysis
3.1 Working principle of inverter
Synchronous speed expression bit of AC motor:
n = 60 f (1-s) / p formula (1)
Where n—the speed of the asynchronous motor;
f-the frequency of the asynchronous motor;
s-motor slip rate;
p ——— The number of motor pole pairs.
It can be known from equation (1) that the speed n is proportional to the frequency f. As long as the frequency f is changed, the speed of the motor can be changed. When the frequency f changes within the range of 0-50 Hz, the motor speed adjustment range is very wide. The frequency converter realizes the speed regulation by changing the motor power frequency, which is an ideal high-efficiency and high-performance speed regulation method.
The role of the frequency converter is to change the speed of the motor by changing the frequency of the power supply, which is also known as frequency conversion speed regulation. The frequency converter is divided into two categories: AC-DC, AC-AC frequency conversion. At present, AC-DC-AC frequency conversion is widely used. It is composed of three parts: a converter, an intermediate filter link, and an inverter. The function of the rectifier is to transform the alternating current of constant voltage and fixed frequency into adjustable direct current, and provide DC power to the inverter through a voltage or current filter. The inverter converts the DC power source into AC power with adjustable frequency. Both the converter and the inverter are thyristor three-phase bridge circuits. The filter consists of a capacitor or a reactor to provide a stable voltage source or current source for the inverter.
3.2 Energy saving method of inverter
3.2.1 Frequency conversion energy saving:
In order to ensure the reliability of production, all kinds of production machinery have a certain surplus when they are designed with power drives. The motor can not be operated under full load. In addition to reaching the power drive requirements, the excess torque increases the consumption of active power and causes the waste of electrical energy. When the pressure is high, the operating speed of the motor can be reduced to make it at a constant voltage. Save electricity. When the motor speed changes from N1 to N2, the change relationship of the motor shaft power P is as follows:
P = CN3; formula (2)
In the formula: P——The host sends
N——Rotating speed of host
C-constant
When the motor speed decreases from N1 to N2, its power also decreases from P1 to P2. Power change formula (3) 
If the efficiency of the water pump is constant, when the required flow rate is reduced, the speed N can be reduced proportionally, and at this time, the shaft output power P has a cubic relationship. That is, the relationship between the power consumption of the pump motor and the rotation speed is approximately a square ratio. When the required flow Q decreases, the output frequency of the inverter can be adjusted so that the motor speed n decreases proportionally. At this time, the power P of the motor will be greatly reduced according to the cubic relationship, which is 40-50 energy saving than adjusting the baffle and valve, so as to achieve the purpose of saving electricity.
For example: the power of a centrifugal pump motor is 55 kilowatts, when the speed drops to 4/5 of the original speed, the power consumption is 28.16 kilowatts, saving 48.8%, when the speed drops to l / 2 of the original speed, the The power consumption is 6.875 kilowatts and the power saving is 87.5%.
3.2.2 Dynamic adjustment of energy saving:
With the development of electronic technology and the maturity of inverter technology, the inverter quickly adapts to load changes and supplies the maximum efficiency voltage. The frequency conversion speed controller is provided with a measurement and control output function of 5000 times / second on the software, which always maintains the motor output with high efficiency.
3.2.3 Power saving by frequency conversion's own V / F function:
Under the condition of ensuring the output torque of the motor, the V / F curve can be adjusted automatically. Reduce the output torque of the motor, reduce the input current, and reach the state of energy saving.
3.3.4 Improve power factor energy saving:
The motor generates torque from the stator winding and the rotor winding through electromagnetic action. The winding is due to its inductive reactance. For the power grid, the impedance characteristics are inductive, and the motor absorbs a lot of reactive power during operation, resulting in a low power factor. After adopting the frequency conversion energy-saving governor, because its performance has become: AC-DC-AC, after rectification and filtering, the load characteristics have changed. The variable frequency speed regulator is resistive to the impedance characteristics of the power grid, the power factor is very high, and the reactive power loss is reduced.
Fourth, soft start energy saving features:
When the motor is started at full voltage, due to the need for the motor's starting torque, it is necessary to absorb 7 times the rated current of the motor from the grid, and a large starting current is a waste of power, and the voltage fluctuation of the grid is also greatly damaged, increasing line loss and variable damage. After the soft start is adopted, the starting current can be from 0 to the rated current of the motor, which reduces the impact of the starting current on the power grid, saves electricity costs, and reduces the impact of the starting inertia on the high inertia speed of the equipment, and extends the service life of the equipment. The soft start controller can automatically determine the load factor of the motor based on the power factor of the motor. When the motor is at no load or the load rate is very low, the conduction angle of the thyristor can be changed through phase control, thereby changing the power input to the motor to achieve the purpose of energy saving. The soft starter uses three opposite parallel thyristors as the voltage regulator, which is connected between the power supply and the motor stator. Such a circuit is a three-phase fully controlled bridge rectifier circuit. When a soft starter is used to start the motor, the output voltage of the thyristor gradually increases, and the motor gradually accelerates until the thyristor is fully turned on. The motor works on the mechanical characteristics of the rated voltage to achieve smooth start, reduce the starting current, and avoid starting overcurrent trip. When the motor reaches the rated speed, the starting process ends, the soft starter automatically replaces the completed thyristor with a bypass contactor to provide the rated voltage for the normal operation of the motor, to reduce the thermal loss of the thyristor and extend the life of the soft starter , To improve its work efficiency, and to avoid harmonic pollution in the power grid.
4.1 Soft start control mode:
4.1.1 Current-limiting soft-start control mode: when the motor starts, its output voltage increases rapidly from zero until the output current reaches the set current limit value Im, and then to ensure that the output current is not greater than this value, the voltage gradually When it rises, the motor gradually accelerates. When the motor reaches the rated speed, the bypass contactor pulls in, and the output current quickly drops below the rated current Ie, completing the starting process. As shown in Figure 1. 
It is a fact that the frequency converter runs at power frequency and has power saving function. But his prerequisites are: first, high power and fan / pump load; second, the device itself has 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 if it doesn't save electricity, it doesn't make much sense. The mechanical characteristic curve of a general AC motor is certain. Both theory and practice have proved that when the load power is less than the rated power of the motor, its efficiency decreases as the load torque decreases, that is to say, the motor will be relatively light at light load. Electricity costs. The inverter will automatically adjust the V / f value according to the size of the load (where V is the voltage of the stator winding of the motor and f is the frequency of the voltage change of the stator winding), changing the mechanical characteristic curve of the motor to adapt it to the load, thereby making The efficiency is improved to achieve the purpose of energy saving.
6. Conclusion
Motor system energy saving is one of the ten key energy-saving projects initiated by the National Development and Reform Commission. According to the requirements of the national development plan, the current frequency conversion energy-saving technology should be promoted, that is, general-purpose mechanical systems such as fans, pumps, and compressors adopt frequency conversion energy-saving measures, and industrial machinery adopts AC motor frequency conversion technology. Motor system energy saving is currently the area with the most commercial potential in China's energy saving market. With the development of microelectronics, power electronics, computers and automatic control theory, frequency conversion technology has entered a brand-new era. The fully mature technology has also made its application enter a new climax. It changes the shaft output power through frequency conversion and speed regulation to achieve the purpose of reducing input power and saving electric energy.
references
[1] Xu Furong. Technical and economic analysis of high-speed fan and water pump speed regulation and energy-saving operation [j]. Inverter World, 2001
[2] Wang Yi, Xu Dianguo. Soft starter for fan load and stop control [J]. Fan Technology, 2001.
[3] Xu Furong, Cui Li. Research on soft starting and optimized energy-saving control technology of AC asynchronous motor [J]. Electric Drive Automation, 2003.1.
[4] Gao Yuenong. The subject of electric motor soft start [J]. Electric Drive Automation, 2005.1.
[5] Li Zixian, et al. Application maintenance and repair of frequency converter [M]. Beijing: Earthquake Press, 2005.
[6] Zhi Chengyong. Principle and application of soft start control of high-voltage high-power AC motors [j]. Control and Transmission, 2008.12