I. Present situation of domestic hoists (I) AC traction mode adopts AC traction mode of series resistance speed regulation, including single rope and multi-rope series connection, and most of them adopt speed regulation mode of changing slip rate S, which generates a large amount of slip power during speed regulation, so that a large amount of electric energy is consumed on the additional resistance of the rotor, resulting in poor speed regulation economy. Very few hoists adopt cascade speed regulation, which has narrow speed regulation range and large investment. (2) DC hoists powered by DC traction thyristor rectifier are common in China's coal mines, but most of them are SCR-D electric control systems of mine hoists introduced in 1980s and made in China before the mid-1990s. The regulation, control and protection circuits of these electronic control systems are basically analog. Due to the limitation of component design and manufacturing level, the system has some defects. (3) Research and development of1. Large DC hoists and electric control systems in China have been gradually improved and popularized. 2. The efficiency of high-power variable frequency speed regulating electric hoist can reach 98%, and the system has been studied by domestic institutions and applied to practical production. Second, the composition and principle of PLC hardware PLC is mainly composed of power supply, CPU, communication unit, high counting unit, analog I/O unit, digital I/O unit and other hardware. (I) Composition of PLC system The main control PLC system consists of power supply, CPU, communication unit, high counting unit, analog I/O unit, digital I/O unit and other hardware. Installed in the main control cabinet. An electric control system with auxiliary PLC is composed of power supply, CPU, communication unit, high counting unit, analog I/O unit, digital I/O unit and other hardware. (2) Basic characteristics of each unit 1. Power supply unit: power input voltage 100-240V AC, which provides bus power and basic power for PLC; 2.CPU unit: CPU unit is the core of PLC, including memory interface and programming interface. , which is the carrier of program execution. The memory stick inserted on it uses lithium battery to store RAM content; PLC can be set to "stop" or "run" mode to execute the program. Third, the control principle (1) Stator control loop When the wellhead or bottom hole sends a start signal to the machine room, if the main power supply and control power supply are connected at this time; The oil pump motor has been running; Oil temperature and oil pressure are normal; The brake handle and control handle are at zero position, the overwinding reset, brake adjustment switch, overhaul reversing switch and overhaul shifting switch are at normal position, and the brake switch is at pedal position, ready to start the hoist (winch). Under normal circumstances, if the brake handle is slowly pushed forward to release the brake, when the oil pressure reaches the opening voltage, the operating handle is pushed forward or backward at the same time, and the main contactor is immediately closed, and the stator of the main motor is electrified, so the winch (winch) starts to rotate forward or backward, thereby increasing or reducing the load. (2) After the stator circuit of the rotor control circuit is electrified, the operating handle is still in the power supply state at this time, all the additional resistors of the rotor circuit of the main motor are added, and the output torque of the motor shaft is only 30-40% of the rated torque. This torque can eliminate the gear clearance of the transmission system, smoothly tighten the wire rope to reduce the impact, and can also start the hoist (winch) with light load. At this point, the hoist (winch) runs smoothly in the preparation stage. At this time, the hoist (winch) will produce a crawling speed of 0.3-0.5 m/s under light load, so as to check the shaft and wire rope and meet the requirements of the mine car crawling in the abandoned roadway when the inclined shaft is lifted. Push the joystick forward or backward step by step, and the PLC will close 1JC-5JC (or 8JC) respectively according to the starting current and gear delay, so as to cut off the rotor resistance of the motor in stages, realize the transition from the preparation stage to the acceleration stage, and gradually accelerate the motor. When the handle is pushed to the front end or the end, the constant speed contactor (the final accelerating contactor) moves, all additional resistances are removed, and the hoist (winch) accelerates into the constant speed stage. The cutting of motor rotor is controlled by the principle that current function is the main function and time function is the auxiliary function. The external resistance series of the motor is determined by the controlled motor power and rotor parameters. Generally, 5-level or 8-level starting resistors are used. The crane (winch) can be adjusted from low speed to high speed or from high speed to low speed. At this time, as long as the joystick is pushed out or pulled back to any position, the hoist (winch) can run stably at the corresponding speed at that position. (3) deceleration control When the hoist (winch) runs to the deceleration point (which can be set by PLC), the PLC sends out a deceleration signal, JSJ acts, the deceleration bell rings, the deceleration indicator lights up, which attracts the attention of the winch driver, and at the same time, the winch automatically decelerates to the last two or three gears; After receiving the deceleration signal, the winch driver should gradually retract the operating handle according to the operating experience, so that the winch (winch) will gradually decelerate and the motor will decelerate to the crawling speed. When the hoist (winch) runs to the terminal position, the brake handle and operating handle should be quickly pulled back to zero. When the crane (winch) runs to the finish line quickly, it can be slowed down by applying the adjustable mechanical brake until it runs to the finish line. (4) speed limit protection circuit When the hoist (winch) enters the deceleration stage, on the one hand, the PLC automatically downshifts, on the other hand, the speed limit is carried out according to the given speed curve, and the deceleration stage exceeds 10%PLC for safe braking. (5) overspeed protection circuit 1. When the hoist (winch) enters the stage of constant speed operation, the voltage signal detected by the tachogenerator is sent to PLC for processing through the transmitter, and the 15%PLC that exceeds the constant speed is safely braked; On the other hand, the overspeed protection signal is given by setting overspeed relay GSJ. One signal of GSJ enters the hardware safety loop for safety braking, and the other signal enters the PLC safety loop for safety braking. 2. When the hoist (winch) enters the stage of constant speed operation, a rotary encoder is installed beside the reducer or low-speed shaft to detect the rope speed, which is handled by PLC, and the 15%PLC with excessive constant speed performs safe braking. Free paper net: