Common protections for coal mining scraper conveyor include emergency stop protection, comprehensive motor protection, underspeed protection and chute blockage protection.
Emergency stop protection: Mainly used for the protection added by the operator to prevent the equipment from starting up erroneously during the operation of the coal mining scraper conveyor after power failure. For the scraper conveyor, the emergency stop device is generally set at the position of the machine head. The emergency stop uses a normally closed point in series and is connected in series in the control circuit. When the emergency stop button is disconnected, it can return to the PLC emergency stop signal. It can also directly cut off the control circuit to ensure that the device will not start.
Comprehensive protection of coal mining scraper conveyor motor: It is mainly installed on the power output circuit of electrical equipment, and the current feedback circuit information of the three-way cable is detected. The content mainly includes overcurrent, locked rotor, undervoltage, overvoltage, three-phase unbalance, Leakage and short circuit. It is mainly composed of current transformer, zero-sequence transformer and motor comprehensive protection controller, and performs internal calculation and processing according to the collected signals. When the set value is reached, the PLC signal is given to the normally open and normally closed contacts, and the automatic control program breaks Open the circuit to protect the electrical equipment.
Underspeed protection: It is to weld an iron piece on the inner edge of the side of the tail wheel of the coal mining scraper conveyor, and let the iron piece be the object to be measured. When the tail wheel of the scraper conveyor rotates, the iron piece rotates with the tail wheel. The proximity switch installed near the tail wheel detects a continuous pulse signal. This pulse signal passes through the secondary instrument installed in the PLC cabinet of the power distribution room. After the conversion, it will be fed back to the PLC in the form of a switch. The normally closed point is used, and it is disconnected during action.
Chute blockage protection: generally set on the side of the chute of the coal mining scraper conveyor head or the side of the blanking point to prevent the accumulation of coal lumps and cause equipment failure. Coal preparation plants generally use heavy hammer protection switches. The voltage used by the heavy hammer is 220V, normally closed device. There is a conductive liquid inside, which conducts when standing upright, and disconnects when the coal blocks pile up and cause tilting or inversion, and returns to the PLC switch signal.
