Abstract: AC variable frequency speed control is the direction of electrical development, with significant energy-saving effect and high control accuracy. This article analyzes the energy-saving effect of frequency converters in gas presses. English Abstract: With the development of science and technology, AC-Converter Control System is widely used in production because it can save power and improve control accuracy. We will discuss its application in Gas-press System in this article. Keywords: Frequency converter, energy saving 1 Introduction The 80,000 m³ gas station of Handan Iron and Steel Plant is a supporting facility for the recovery of converter gas in the No. 3 steelmaking process of Handan Iron and Steel. The recovered converter gas is sent to various users through two gas presses. The gas press is a D1000-11 type produced in Jiangyin, with a flow rate of 16.67 m³/s, a total pressure of 24.5 kPa, and equipped with an 850 kW, 10 kV AC asynchronous motor. The process requires an outlet pressure of 22-24 kPa and a flow rate of 60,000 m³/h. To meet the user's gas usage needs, the JZHICON-1A-10/060 frequency converter produced by Harbin Jiuzhou was selected. 2 Advantages of the JZHICON-1A-10/060 frequency converter (1) Adoption of advanced control technology The JZHICON-1A series high-voltage frequency converter adopts advanced power unit series superimposed wave technology and space vector control sinusoidal PWM modulation method. It has a built-in PID regulator, which can realize closed-loop operation. It has a built-in PLC, which can realize flexible control in different application sites. It has three control modes: local, remote and host computer. (2) High-quality power input The secondary coil of the isolation transformer on the input side is phase-shifted to provide power to the power unit, which is equivalent to 48 pulse diode rectification input. It eliminates the harmonic current caused by a single power unit, greatly suppresses the generation of grid-side harmonics, and eliminates the need to install an input filter and protect the power supply and peripheral equipment from harmonic interference. (3) Perfect output performance: The unit is connected in series with pulse width modulation and superimposed wave output. There are 8 units per phase in the 10kV series, which greatly reduces the output harmonic content. The output waveform is close to a perfect sine wave and no output filter device is needed. (4) Energy saving effect: Traditional pressurizers control the flow and pressure of the pipeline network by manually adjusting the opening of the outlet valve to artificially increase or decrease the wind resistance of the pipeline network to reduce or increase the flow. The motor always runs at a constant speed. In this system, the outlet pressure and flow of the pressurizer are adjusted by the change of motor speed. 3 Energy saving principle of the new system 3.1 The speed of the asynchronous induction motor is determined by the following formula : n=(1-s)60f/p Where: n——motor speed; s——motor slip; f——power supply frequency; p——number of motor pole pairs. Changing any parameter in the formula can change the motor speed. For example, use a cascade speed control device to change the slip, manufacture motors with different pole numbers and pole pairs to change the number of pole pairs, and use frequency conversion technology to change the power supply frequency, etc. 3.2 Energy-saving principle of fan speed regulation control According to the principle of fluid mechanics, the air volume Q is proportional to the speed n, the pressure H is proportional to the square of the speed n, and the shaft power P of the motor is proportional to the cube of the speed n, that is: Q/Q1=n/n1 (1) H/H1=（ n/n1）2 (2) P/P1=（ n/n1）3 (3) Q1: rated air volume of fan n1: rated speed of motor P1: rated power of motor H1: rated pressure of fan The power expression P/ P1(Q/ Q1)3 (4) Assuming that the efficiency of the fan is constant, when the air volume drops to 80% of Q1, that is, when the speed drops to 80% of n1, the shaft power can be obtained from equation (4) as P_shaft=0.512＊P1/ηF (5) ηF: is the efficiency of the fan. When the air volume drops to 50%Q1, that is, when the speed drops to 50%n1, the shaft power can be obtained from equation (4) as Pshaft = 0.125 P1/ηF (6). The calculation results show that when the process requires a reduction in air volume, if the fan speed is reduced, not only can the process requirements be met, but the motor shaft power is also significantly reduced, thus saving a lot of electricity. If the air volume is reduced by manually adjusting the valve, although the process requirements can also be met, the motor speed remains unchanged and the motor shaft power does not decrease. According to theoretical calculations, when Q drops to 80% of the rated Q1, the speed control method saves nearly 49% more electricity than the regulating valve. When Q drops to 50% of the rated Q1, the speed control method can save up to 87.5% more electricity than the regulating valve. The above theoretical calculations show the energy-saving effect. 4. Economic benefits of using variable frequency speed control system 4.1 Energy saving Under normal system operation, the motor frequency is about 42.6Hz and the motor power is maintained at about 41.6% of the rated power. According to this calculation, the annual power saving of the press exceeds 2,000,000 kWh. At RMB 0.48/kWh, the annual saving is more than RMB 960,000. 4.2 Improved motor efficiency and CosΦ value The use of frequency converter has greatly improved the efficiency of motor. After using frequency converter, the CosΦ value is above 0.96, which is much higher than that of traditional system. 4.3 Other According to statistics from relevant departments, in situations where flow control needs to be changed, the energy saving of frequency converter is generally 30% to 60%, and it has the following characteristics: (1) Soft start function. Frequency converter has soft start function. There is no starting impact current when starting. The current starts from zero and increases according to the speed and gradually rises. No matter what, it will not exceed the rated current. Therefore, it does not matter when the motor is started, which can save starting equipment. (2) The frequency converter itself has strong protection and control functions. By setting the frequency converter, protection parameters and control requirements can be easily determined. Currently, the widely used frequency converters are AC-DC-AC type, vector control, and are particularly suitable for fans and pumps. Some frequency converters also have PID regulation functions and some programmable functions, greatly facilitating user operation. 5 Conclusion In summary, although the initial investment in frequency converters is large, their economic benefits are very obvious in the long run. With the development of science and technology, frequency converters will inevitably be more widely used, and their performance-price ratio will be more acceptable to users.