One of our customers cement factory No. 3 limestone crusher selected BL type impact crusher for primary crushing, its feeding system adopted 1500× 12000 apron feeder, the drive motor selected Y225M-4 three-phase AC asynchronous motor. Because the feeder can not adjust the linear speed of the system, when the feed is in excess, it can only stop feeding by stopping the motor, which brings certain difficulties to the control of the feeding amount, especially in rainy weather, the material stickiness is large, the motor heavy load starts and stops frequently, which has a greater impact on the motor and transmission system. In addition, the interval feeding is not easy to control the uniformity of the feeding, which has a great impact on the particle size of the broken discharge, and is difficult to meet the production requirements.
System transformation and debugging We use frequency conversion speed regulation technology to control the speed of the feeder, that is, according to the principle of N=601=s, to achieve the speed control of the AC motor. Considering the requirements of the crushing system, the inverter can not only control the variable speed operation of the motor, but also provide sufficient torque output. To this end, among the many inverter brands, we choose the ACS600 series inverter produced by ABB, its main characteristics are as follows:
1. Direct torque (DTC) control technology, changes the traditional vector inverter control mode, zero speed does not need speed feedback, can achieve full torque output characteristics, dynamic response is fast, and stable and controllable, starting torque up to 200% of rated torque, can withstand 150% overload for 1min.
2. To provide a full range of motor protection, including overvoltage, overcurrent, lack of phase and motor blocking and temperature rise protection, while realizing the soft start of the motor, so that the equipment runs smoothly, thereby extending the service life of the equipment, and can reduce vibration, impact and noise, provide a good working environment. Through the test, it is found that when the apron feeder drive motor runs normally, the three-phase average current is only 30A(rated current 84.6A), and the motor selection is obviously large. In order to save the project investment, after the project demonstration, the frequency converter is selected.
Frequency converter installation, wiring is relatively simple, under normal circumstances, just the frequency converter series connected to the main circuit cable of the motor can be. In order to facilitate operation, a 10k2 speed adjusting potentiometer and a digital display tachometer can be added to the operating table, and the original start-stop control loop does not need to be changed. Combined with the process status of the crushing system, in order to prevent the occurrence of adverse factors such as heating of motor windings caused by high harmonics during the no-load operation of subsequent crushing and low frequency operation, the lower limit of frequency is set at 10Hz(speed 300r/min) and the upper limit is 50Hz(speed 1470r/min). Adjust according to the actual needs of production.
apron feeder transformation effect
1) Apron feeder wide speed range to achieve stepless speed control, according to the actual incoming material and subsequent crushing situation timely adjust the feeding amount, to achieve the expected effect of continuous and uniform feeding.
2) Motor start no impact damage three-phase AC asynchronous motor using direct starting mode, the starting current is about 5 to 7 times the rated current. After the technical reform, the starting current is less than 1.7 times of the rated current, and the interval feeding mode of the frequent start and stop motor is eliminated, the operating condition of the equipment is greatly improved, and the equipment maintenance workload of the post workers is reduced.
3) The power saving effect is remarkable
This apron feeder through more than two months of operation, normal, the motor operating frequency is 20~40Hz, the average current of the power grid 8~15A, the power saving rate of more than 40%.