Several problems should be considered in the selection of ball mill motor
The ball mill is dragged by the motor. Therefore, we can't just consider the machine itself and not the electrical. When selecting a motor, consider the following aspects: 1. Load characteristics of the ball mill (1) The working speed of the ball mill is constant. Unless there is special speed change in the process, the main motor of the ball mill is generally not required to adjust the speed; (2) The ball mill is the largest electricity-consuming equipment in the cement factory. As mentioned above, the ball mill consumes about two-thirds of the electricity used in cement production; (3) When the ball mill is in normal operation, its load is basically stable; (4) The starting torque of the ball mill is 1.1 to 1.5 times the rated torque of the motor. 2. Requirements for electric power drag: (1) Power specifications The rated power of the selected motor should be 1.05~1.1 times higher than the actual required motor power of the ball mill, and the load rate is guaranteed to be above 90%. In this way, the motor is often in a fully loaded state during operation, making full use of the power of the device. (2) Motor start request Since the ball mill main motor has a large capacity, the starting current should be limited. Otherwise, the starting current is too large, which will inevitably lead to a sudden drop in the grid voltage, which will cause the other equipment of the factory to “become out of pressure†and even cause a shutdown accident. (3) Improve the power factor of the motor On the one hand, the choice of the appropriate motor type, on the other hand, depends on the compensation measures for the power factor. (4) Power supply voltage In the electric drive of the ball mill, low voltage power is used: 220V, 380V; high voltage is used: 3000V, 6000V. Generally speaking, the motor of a small ball mill uses low-voltage electricity, and the main motor of a large- and medium-sized ball mill exceeding 300 KW should use a high voltage. 3. Introduction to the motor for ball mill drag (1) Asynchronous motor In addition to the small ball mill application of the squirrel-cage motor drag, most of the small and medium-sized ball mills are driven by a three-phase wound asynchronous motor. Wirewound motors are available in JR, JRQ, and YR series. The main disadvantages of asynchronous motors in ball mill drag are: 1 equipment is simple and cheap; 2 has sufficient starting torque to directly start the ball mill; its starting torque can be controlled by connecting the series resistance of the rotor winding The frequency sensitive varistor automatically changes the resistance in the rotor circuit during the starting process of the motor to adapt to the requirement of improving the starting performance. When starting, as long as the power switch is closed, the motor is automatically reduced in the frequency sensitive varistor as the rotor speed increases. The resistance of the string in the rotor circuit causes the motor speed to rise steadily. 3 The starting current is small. The starting current can be controlled below 1.5 times of the rated current, so it is applied to the line with small grid capacity and will not affect the normal operation of other equipment. Its only drawback is that asynchronous motors have a lower hysteresis power factor. This limits its application to ball mill drag. There are two ways to improve the power factor: one is to apply a large-capacity high-voltage electrostatic capacitor; the other is to apply it to the camera, connect it to the rotor winding of the main motor, and change the phase of the motor to improve the factor. Increase the motor power factor to 0.95 to 1.0. In addition, the power factor of the asynchronous motor is related to the rated motor speed. The lower the speed, the lower the power factor. Therefore, from the point of view of electricity use in the river, high-speed asynchronous motors should be preferred. (2) Synchronous motor There are two kinds of synchronous motors for dragging ball mills: ordinary low-start torque synchronous motors, TD series three-phase synchronous motors; large-scale low-speed high-torque ball mill-specific synchronous motors - three-phase synchronization for TDQ and TZ series ball ball mills Electric motor. (3) Induction synchronous motor Induction synchronous motors have the following advantages: 1 Compared with asynchronous motor at start-up, it has the advantages of large starting torque and small starting current; 2 Compared with synchronous motor in operation, it has the advantage of advanced power factor, thus solving the problem of non-moving compensation of cement plant power grid; 3 constant speed The disadvantage is that the manufacturing is complicated and expensive. However, the induction synchronous motor is promising as the transmission original motor of the large ball mill. (4) Ball mill main motor selection principle In the selection of the model, in addition to considering the above various motor characteristics, the following issues should be considered comprehensively: 1 The initial investment and operating expenses must be balanced; 2 Considering the type of motor of other equipment in the cement plant, that is, the power factor of the whole plant power network; 3 When determining the rated voltage, the voltage transformation status of the power grid and the capacity of the power grid should be taken into account in the area where the cement plant is located; 4 It is determined that the motor should be uniformly evaluated with the mechanical transmission scheme of the ball mill, and the mechanical manufacturing conditions of the speed reduction mechanism should be taken into account when assessing. 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