In recent years, a method for improving the efficiency of removing iron has been developed. A "short-term strong excitation" is applied to the electromagnet, that is, a sensor is installed on the front side of the magnetic shoe and on the lower side of the conveyor belt. Its purpose is to detect demagnetization using a sensor. The magnetic material at the farthest point of the boot and the weakest attraction effect is then transmitted through the sensor to the forcically excited rectifier so that when the magnetic substance passes under the pole piece again, a high supply voltage is briefly applied to the magnet ring. Generated a strong magnetic flux, so that a sudden increase in electromagnetic suction, which will be able to aspirate the magnetic material buried deep, then the voltage will be restored to the usual power supply. The purpose of installing the sensor in front of the pole piece is to avoid interference from the magnetic field of the electromagnet. Under normal circumstances, when the iron material is in the upper or middle of the coal seam, the sensor will not send an effective signal, only when the iron is buried in the bottom of the coal seam. Can send a valid signal.

The sensor has the following aspects: The normal excitation triggering control link is mainly for the normal excitation control of the electromagnet, and it needs to have a trigger pulse movement adjustment function to control the main commutator silicon KP1, KP2 to achieve a normal excitation current adjust. The strong excitation delay control link is to provide time delay from the detection of the iron material signal to the time when the iron material just runs to the front stage of the pole piece of the electromagnet, and then starts the strong excitation control signal and starts the strong excitation triggering stage. In the best moments for strong excitation, and reduce the excitation time as much as possible, do not miss the purpose of capturing strong incentives. The strong excitation time control link is mainly to control the length of the forced excitation time, and to control the strong excitation time in the front section of the front pole shoe before running and to the rear end of the rear pole shoe, to control the strong excitation time in the optimal range. Inside. Strong excitation triggering control link It is mainly under the control of strong excitation delay and strong excitation time, it sends strong excitation trigger pulse to the thyristor KP3 and KP4 of the strong excitation main loop for strong excitation. In addition, there is no need to control the trigger pulse, and only the trigger angle can be controlled to the minimum value, so that a larger excitation current can be obtained.