In the mechanical transmission powered by the electric motor, the flow speed control has always been ahead of the AC speed control with excellent performance. However, because the DC motor has brushes and commutators, the maintenance and maintenance workload is large, and there is a limit capacity problem. The field of speed regulation turned its attention to AC motors. After the 1960s, especially since the 1970s, the continuous development of MCT and Intelligent Power Module (IPM) has enabled the rapid development of frequency conversion technology. (1) Features of frequency conversion speed regulation AC motor frequency conversion speed regulation is a new technology developed on the basis of modern microelectronics technology. It has a wide range of speed regulation, smooth speed regulation, high efficiency, good characteristics, simple structure, good mechanical characteristics, and protection functions. Complete, stable, safe and reliable, it can easily achieve constant speed or constant power speed regulation. It is superior to AC speed regulation such as voltage and speed regulation, variable pole speed regulation, cascade speed regulation, etc.; its speed regulation characteristics are comparable to those of DC motors, and it is the ideal choice of frequency converter. Introduction In recent years, the AC inverter technology has developed rapidly. There are many inverter manufacturers. The main products are: U1 G9S series and P9S series inverters of Fuji company. The input and output voltages are 200V and 400V. G9S series power is 0.2220kW, P9S series power is 7.5280kW, G9S starting torque is 150%, P9S starting torque is 50%, so G9S is suitable for occasions requiring large starting torque. 13.Since 1972, Siemens AG of Germany has applied the frequency of “cross-over” to large-scale cement mills, ore crushers, and mine hoists. Since the 1980s, China has adopted the application of frequency conversion speed regulation technology as the main direction of power transmission innovation. . In order to meet the needs of medium and small-capacity AC motors to achieve variable frequency speed regulation, many inverter series suitable for asynchronous motor operation have been established in China. In 1986, Beijing Electric Motor General Factory introduced a full set of production technology and equipment from Mitsubishi Japan, and developed the P5C inverter series. The suitable motor power is 1.5 110kW, the power supply voltage is 380V, and the frequency variation range is 1 3.2. Application of inverter The governor speed control method has u/f type and vector type. The u/fa system method is based on the static model of the asynchronous motor. The system shows obvious at low speed and dynamic (such as acceleration and deceleration), and when the load is increased or decreased. The defect vector control method is based on the dynamic mathematical model of the AC motor and uses the coordinate transformation method to decompose the fixed current of the AC motor into the magnetic field component current and the torque component current, and control them separately. Dynamic performance of high-speed systems.

The frequency converter of u/fg system is suitable for the load of mechanical characteristics of fans and pumps. The load torque of this type of load decreases rapidly as the speed decreases. For the load with constant torque mechanical characteristics, the inverter of the vector control mode should be selected, because the vector control mode can still obtain a large starting torque at low frequencies.

For general industrial equipment that does not require high control accuracy, the u/f system can be used, and the speed control accuracy is 2% 3%. For industrial equipment that requires high control accuracy, the open-loop control method can be used, and the speed control accuracy is better than 1%. For special industrial equipment that requires high control accuracy, closed-loop vector control mode or servo control mode can be used, and the speed control accuracy can reach 0.01%. Fuji inverters should use P9S series products for fans and pumps. For constant torque loads, G9S series products should be selected; however, regardless of the load on the inverters of Siemens and CT, the product selection is a unified series, and the control characteristics are selected by the software in the machine.

4 The application of frequency conversion speed regulation in the building materials industry 4.1 The feeding equipment of cement and 1 flow speed cement plants generally adopts slip speed regulation. Practice has proved that in the case of relatively harsh industrial environments, slip motor speed regulation is adopted. At high speeds, due to the poor sealing of the slip clutch, the clutch is easily blocked by dust or foreign objects and causes a flying phenomenon. The low speed performance of the slip speed regulating motor is poor. When the belt scale is running at a low speed, the speed of the belt conveyor is often in an unstable state, which will affect the normal work and measurement accuracy of the belt scale when it is serious. In addition, when the range of the set value of the belt scale is required to be large, the speed range of the slip speed regulating motor is not large enough. If the slip motor is changed to a variable frequency speed regulation motor and a vector control inverter is used, the speed regulation performance can be greatly improved, the system reliability is improved, and the system power consumption can be reduced. The slip motor is changed to frequency conversion speed regulation It will be the main application area of low-power frequency converters in cement plants.

Large and medium-sized cement r generally adopts rotary kiln for calcining cement clinker. Regardless of the type of kiln used, it is required to adjust the speed of m rotary kiln. For N rotary kiln, the current DC speed is generally used in China, but for cement rotary kiln AC frequency conversion speed regulation has replaced DC speed regulation. Some cement plants at home and abroad have been successfully applied. The reliability of AC motors is high, which improves the operation rate of the rotary kiln. However, this technology is still in the trial stage and needs to be further deepened. the study.

4.2 The frequency converter of the ceramic material search machine controls the mixer for the production of ceramic materials. According to the different materials and the speed of the system, the mixing speed can be adjusted accordingly; the finished ceramic products can be delicate, smooth and firm when the mixing speed is uniform. durable. The greater the viscosity of the material, the greater the torque of the motor. The entire stirring process requires low-speed constant torque. Especially at low-speed stirring, the control system needs to have a low-frequency large torque output function. The frequency converter of Hitachi 300 series is used to adjust the rotation speed of the mixer, so that the mixer system achieves good low-frequency characteristics, large output torque, strong mixing ability, system operating efficiency and wide range of processed materials, which satisfies the requirements of the production process well.

43 Energy-saving effect of frequency conversion speed regulation technology shed There are many large fans in the cement production line, such as milling fan and kiln tail fan. Usually these fans use valves to adjust the air volume. Although this method of air volume adjustment can meet the needs of cement production, it Cause a lot of waste of electrical energy. If frequency control is adopted for these fans, not only can the characteristics of air volume adjustment be improved, but also significant energy saving can be achieved.

5 Conclusion Frequency conversion speed regulation is currently the world's best performance, efficiency and most widely used motor speed regulation technology, is the development direction of electric drag. With the application of new technologies and new theories such as vector control and speed sensorless technology in variable frequency speed regulation, it will develop in the direction of higher performance, greater capacity, and intelligence.