Mineral sizers have the advantages of light weight, small size and low energy consumption, and are suitable for a variety of operating environments and have been widely used in coal mines. In open pit mines, large volumes of raw coal are broken by mineral sizers and then driven by belt conveyors to coal bins or secondary crushers. Because the raw coal is often mixed with gangue, iron and other hard materials, mineral sizers often stop the load, resulting in equipment damage. At present, coal mine production enterprises often use the moment limited hydraulic coupler as overload protection device to maintain the normal operation of mineral sizers. However, in open-pit coal mines, the load of the crusher is a strong impact type, the vibration is large, and the hydraulic coupler often has oil leakage and other phenomena, which affects the normal use of the equipment. At the same time, when the ambient temperature is low in winter, the hydraulic coupler is easy to melt plug, and can not effectively protect the equipment when the load is blocked and turned off, which may cause production accidents. Different from the hydraulic coupler, the magnetic coupler takes the magnetic field as the medium and relies on the interaction between the magnetic fields to achieve the effective transmission of torque. Compared with the hydraulic coupler, it has the advantages of high efficiency, fast dynamic response, easy maintenance, etc., and has been widely used in the field of coal mining.
1. The torque limited magnetic coupler is mainly composed of an input component and an output component, and a permanent magnet is installed on the output component to provide the air gap main magnetic flux. When there is relative displacement between the input component and the output component, the copper ring cutting air gap main magnetic flux generates eddy current, and the eddy current magnetic field interacts with the air gap main magnetic field to generate torque and realize the energy transfer from the motor to the load. Since there is no physical contact between the input and output components of the magnetic coupler, it has the advantages of low centring requirements and vibration isolation. Under normal circumstances, the rated slip rate of the magnetic coupler is 0.01~0.03.
The running curves of the magnetic coupler and motor are shown in figure 2. Since the input speed of the magnetic coupler is the output speed of the motor, when the Mineral sizers magnetic coupler and the motor work together, the magnetic coupler curve turns up and down, and the intersection point between the two curves is the working point of the motor and the magnetic coupler.
The slip speed of the magnetic coupler increases with the increase of the load. When the load torque is greater than the limit value, the axial force of the magnetic coupler becomes larger, the output component is separated from the input component, and the motor runs no-load, realizing the function of overload protection of the motor
2. Crusher magnetic coupler transformation of the current site crusher motor rated power is 220kw, rated current 25.1a, no load operation motor current 8.5a, normal operation current about 14a. Due to the field conditions, the crusher motor often has impact changes, and the strong impact load can instantly reach 4 to 5 times the rated power of the motor, which is more than 10 times the normal operating power. When the torque limited magnetic coupler overload protection, the motor is equivalent to no-load operation, the motor current is not much different from the crusher no-load operation, it is necessary to build an overload protection detection system, when the overload protection, you can remind the field staff to deal with. Usually, the operating status of the magnetic coupler is monitored by the sensor, but because the open-pit crusher is installed outdoors, the ambient temperature can reach a minimum of -50 ° c in winter, the electronic control equipment and sensors can not work normally in such a low temperature environment, so it is necessary to build an electronic control system that can accurately determine whether the torque limited magnetic coupler is overload protection. Due to the field collection of motor running current, combined with the constant current during no-load operation and the impact change of current during load operation, the heating power of the torque limited magnetic coupler during overload protection operation is set at slightly higher than 70kw, so that the current of the motor is stable at about 12a when the load is blocked and stopped, which is convenient for the electronic control system to judge.
3. Limited moment magnetic coupler because the overload coefficient of the limited moment magnetic coupler is generally about 2.0, in order to cope with the needs of strong impact load, it is necessary to improve the rated power of the limited moment magnetic coupler, and change the conventional matching principle of the coupler: Prime mover: Machine from 1:1.05:1.1 to 2:1.05: 1.1, so that the limited moment magnetic coupler can still have the overload operation ability when the strong impact, to avoid affecting the normal operation of the crusher.
The slope deformation process of mineral sizers is carried out by using a torque limited magnetic coupler, and the relationship between the cause of slope deformation and the imaging form of foundation interferometric radar is obtained. In general, the foundation interference radar imaging can easily and effectively deduce the cause of slope deformation in open pit mining area, and help to analyze slope deformation in detail, which is of great significance for the safe operation of mining area.