Currently, frequency converters are increasingly widely used in cement production enterprises. Due to their advantages such as low failure rate, high speed control accuracy, multiple protection functions, and significant energy-saving effects, variable frequency speed control systems are the most ideal replacement for DC speed control and electromagnetic slip speed control. At the same time, the rationality of the frequency converter parameter settings directly affects whether the frequency converter can start smoothly, operate stably, and achieve energy-saving effects. Some parameters in the frequency converter parameter settings must be set first and do not need to be modified, such as motor power, number of motor poles, rated current, and rated voltage. Other parameters, however, require repeated adjustments and modifications based on different loads to achieve optimal performance. The 2500t/d clinker production line of kiln No. 6 at Harbin Cement Plant, which went into operation at the end of 2003, extensively adopted variable frequency speed control technology. 1. Application of Variable Frequency Drives in Fans Many devices in rotary kiln systems use centrifugal fans to regulate airflow. Due to constantly changing operating conditions and other factors during production, centrifugal fans are usually designed with a large margin of safety. Therefore, in actual use, to meet production requirements, electric valves, baffles, and other devices are installed in the air inlet ducts to regulate airflow by adjusting the valve opening. This method of changing airflow by increasing system resistance results in significant energy loss. However, using variable frequency speed control to regulate airflow offers a much more efficient energy-saving effect. The principle of energy saving through variable frequency speed control for fans: Speed ​​control of fans reduces aerodynamic energy consumption and is a relatively ideal energy-saving method. Compared with the method of controlling airflow by adjusting dampers, it has a significant energy-saving effect. The primary air fan at the No. 6 kiln head and the primary air fan at the kiln tail decomposition furnace in this plant all utilize variable frequency speed control technology. Key Parameter Setting: For loads like fans, the key is to properly adjust the start-up and stop times. Initially, we set several times, including 20s, 40s, and 60s. Due to the large inertia of the fan, overvoltage tripping occurred during acceleration and deceleration. After repeated adjustments, we finally set the time between 90s and 120s, and the acceleration and deceleration speed regulation were normal. 2. Application of Frequency Converters in Grate Coolers Because grate coolers need to operate in high-temperature, high-concentration dust environments for extended periods, the grate cooler motor is prone to failure. This factory has now adopted frequency converter motors instead of DC motors. Key parameters: deceleration time, regenerative feedback control. Since the grate bed of the grate cooler is in reciprocating motion, each motion cycle consists of forward acceleration, forward deceleration, stop, reverse acceleration, and stop cycles. If the motor is in an accelerating state, the force of the motor is greater than the resistance of the grate bed, and the motor works normally; when the motor reaches the given speed, the grate bed stops. During the transition from reverse acceleration (or stop * forward acceleration), due to the resistance of the material and the gravity of the transmission arm, the grate will generate a reverse acceleration force on the motor, causing the motor to be in a generating state at this time. This generates a feedback control electromotive force superimposed on the motor stator, triggering the overvoltage protection action of the frequency converter. Therefore, the regenerative feedback control parameters should be repeatedly adjusted. Different brands of frequency converters and different production conditions require different parameter values, so repeated adjustments are necessary to determine the correct parameter. Additionally, for the deceleration time, if the setting is too small, overvoltage alarms often occur when the speed is reduced or the machine stops; the stopping time should be appropriately extended. 3. Application of Frequency Converters in Raw Material Vertical Mill Classifiers The MP S3750B vertical raw material mill classifier in this factory uses frequency conversion speed control technology. Key parameter setting: capture and restart. According to the classifier's process requirements, the exhaust fan must be turned on before starting the classifier. The structure of the classifier dictates that the classifier body rotates along with the exhaust fan, resulting in the motor already having a certain speed before the classifier starts. If the frequency converter is started to supply power to the classifier at this time, it will cause the frequency converter to trip due to overcurrent, and this phenomenon always occurs after repeated adjustments. Finally, the capture restart constant was set to 2, and the start-up was normal. The reason is that the capture restart constant was 0 at the factory, which allows the motor to start normally in a stationary state. However, before starting, when the motor is rotating or driven by the load, it will be braked before returning to the set value of the frequency converter, which will cause overcurrent tripping. After setting the capture restart parameter to 2, the frequency converter can capture the speed of the motor through the capture restart function and drive the motor from this speed to the set value. In summary, in the actual production process, the advantages of the frequency conversion speed control system are far greater than those of the DC speed control system and the electromagnetic slip speed control system. In addition to the above-mentioned equipment using frequency conversion speed control, the 2500t/d clinker production line of this plant also uses frequency conversion speed control system on the outlet separator and belt conveyor of the ZGM80G vertical coal mill, and the results are very good. 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