The crusher of our customers in Xinjiang is designed and produced by our company, with the designed crushing capacity of 3000t/h. The crusher, together with the belt conveyor, type A and Type B cars, forms the semi-continuous production system of Yimin open-pit mine. Crusher feeding system for scraper conveyer adopts hydraulic drive mode. It is powered by two 250kW driving motors, driven by two straight gear reducer to four hydraulic pumps to generate system pressure, driven by two 1500r/min hydraulic motors, and driven by two planetary reducer to drive the main drive shaft to drive the scraper. Due to the harsh working environment, serious dust, large vibration of equipment, and large temperature difference between winter and summer, the hydraulic system and components fail for many times, which seriously affects the reliable operation of apron feeder hydraulic drive system. With the increasingly mature variable frequency drive system replacing hydraulic drive system has been widely used. 1. Feasibility of using frequency converter
(1) Operating characteristics of apron feeder: most of them start with no load, basically no overload phenomenon, occasionally start with rated load, receiving a maximum of 70t coal in the hopper; Require zero speed start, speed range is 0~0.6m/min, can manually control slow acceleration or deceleration, speed between 0.3 to 0.5m/min used more and stable operation; In stable operation, the external load is basically stable and the impact is small. The ambient temperature is low and the dust is large.
(2) The working characteristics of the converter: it has automatic acceleration and deceleration functions, can adjust the acceleration and deceleration time, can choose acceleration, honest speed mode and frequency hopping function, can ensure that the motor has rated torque at low speed operation, and high efficiency, small impact on the power grid, low failure rate. Therefore, the variable frequency driver system can fully meet the needs of apron feeder driver. The working characteristics and running time of working face belt conveyor (driven by frequency converter) are basically the same as those of apron feeder. Through the comparison of various performance indexes and maintenance costs of these two devices, the operability and economy of replacing hydraulic drive system with frequency converter drive system can be better analyzed.
2. Main equipment and selection of the system.
Planetary reducer of hydraulic drive system requires rated input speed of 1500r/min and input power of 130kW, and apron should be considered The operating speed of the feeder is 0.3~0.5m/min, and the rated speed of the drive motor is 1488r/min. The oversetting of the converter should not exceed 5% to meet the working requirement of 1500r/min input speed of the planetary reducer. Therefore, the planetary reducer should be kept in use.
Rated driving power of apron feeder is PN=1.3Fzv/(1000). In the formula, PN is rated driving power of apron feeder, kW; Fz is traction force, N; v=0.6m/s, is the speed of scraper conveyor; 7=0.8, is the total efficiency of frequency conversion transmission system. Fz Fz | of calculating formula for N = F F2 ten F3 F4 ten F3 = 18065 + 1806.5 + 243 + 154227 + 140810 = 315151.5 type: F: as the running resistance, N. F2 is the additional resistance, N: F3 is the charging resistance, N; F4 is the lifting resistance, N; Fs is friction resistance, N. Then, the power of the motor driven by PN=307 kWapron feeder is Pg=(1.1~1.6). Considering that apron feeder is driven by two motors to start with heavy load, and should be started with load after the hopper coal is frozen and bonded in winter, certain overload capacity should be reserved. The overload coefficient is taken as 1.6. Then P=491.2kW, frequency conversion drive system adopts two motors coaxial drive, therefore, the power of each motor is selected as 250kW. According to the above calculation results, Siemens 1PQ series variable frequency drive motor is selected. Its main parameters are as follows: type 1PQ8315-4bp, power 250kW, revolution 1500r/min, voltage 400V, rated current 430A, frequency 50Hz, power factor 0.87 and protection class IP55.

The selection process of frequency converter mainly considers the installation environment of frequency converter, the optimal matching between the capacity of frequency converter and the motor power. The actual current value of the motor is mainly used as the basis for the selection of frequency converter, and the rated power of the motor is only used as a reference [3]. Because the output of frequency converter contains high harmonics, which will cause the power factor and efficiency of the motor to deteriorate, the rated capacity of frequency converter should be slightly greater than the rated power of the motor. Generally, the capacity of the motor in industrial production is larger, so the frequency converter can be selected according to the load power of the motor to meet the working needs. For continuously working frequency converter capacity, rated current I and capacity P of frequency converter can be determined according to rated current method of motor. As motor parameters have been determined, that is, P=250kW,Um=400V, Im=430A,7=0.75,c0s =0.96, rated current Im≥KIm= 451-473a, capacity Pm≥ 1.732KUm Im cos=300.3~314.5kW. Where: K=1.05~1.1, is the correction coefficient of current wave.
The inverter model is ACS800-04-0400-3. The main parameters are as follows: the working voltage is 400V, the light overload continuation rated current is 590A, the typical power of the light overload motor is 315kW, the heavy overload continuation rated current is 477A, and the typical power of the heavy overload motor is 250kW. Because apron feeder hydraulic drive system and variable frequency drive system both use planetary reducer.