Transformation of mine hoist by the hottest freque

Transformation of mine hoist by frequency conversion speed regulation system

transformation of mine hoist by frequency conversion speed regulation system

AC-DC-AC frequency conversion speed regulation system has been widely used in pumps and fans, and is being widely promoted. However, most mine hoists still use the traditional wire wound asynchronous motor, which uses the method of rotor series resistance to regulate speed. This system belongs to the stage speed regulation, with small low-speed torque, large slip power, large impact of starting current and shift current, large vibration in medium and high-speed operation, unsafe and unreliable braking, poor treatment of regenerative energy, discontinuous speed regulation in the operation of inclined shaft hoist, easy to fall off the track, and high failure rate. Mining production is a 24-hour continuous operation, even if a short time of shutdown and maintenance will bring great losses to production. The technical transformation of mine hoist is urgent. However, it is impossible to directly apply the frequency converter used for fans and pumps to the elevator, because the lifting load has many special requirements for the frequency converter. In view of the particularity of the hoist, the frequency conversion speed regulation system of mine hoist developed by our company 2 the advantages of the system (1) realize soft start and soft stop, reduce mechanical impact, and make the operation more stable and reliable. (2) When starting and accelerating gear shifting, the impact current is very small, which reduces the impact on electricity, simplifies the operation and reduces the labor intensity of workers. (3) The running speed curve is S-shaped, making the acceleration and deceleration smooth and free of impact. (4) The safety protection function is complete. In addition to the general protection of overvoltage, undervoltage, overload, short circuit, temperature rise, etc., it also has the functions of interlock protection, automatic speed limit protection, etc. (5) With DC braking and energy consumption braking, it is more safe and reliable. 3 working principle of frequency conversion and speed regulation system of mine hoist frequency converter changes the speed of motor by changing the power supply frequency of motor stator, so as to realize the speed regulation of winch. The speed formula of AC asynchronous motor is: where n - motor speed F1 - stator power supply frequency; P - polar logarithm s - slip; The equipment is an AC DC AC voltage type variable frequency speed regulation system, and the schematic diagram is shown in Figure 1. The operation process of the system is mainly divided into two processes: (1) the process of winch motor as a motor, that is, the normal inverter process. This process is mainly composed of rectification, filtering and normal inverter, as shown in Figure 1. Among them, the normal inverter process is its core, "said LV CONGYANG, Secretary General of China Polyurethane Industry Association. It changes the power supply frequency of the motor stator and the output voltage to achieve the purpose of speed regulation. (2) The operation process of winch motor as a generator, that is, the braking process of frequency converter. This process is mainly completed by the freewheeling diode, braking unit and braking resistor of IGBT in the normal inverter part. This process is that when the hoist works in the lowering process, the motor is equivalent to a generator, and the electric energy is fed back to the DC bus of the frequency converter through the motor, resulting in the high voltage of the DC bus. According to this phenomenon, the brake unit and brake resistance are used to consume the excess energy of the DC bus, so as to achieve the purpose of accurate shutdown of the frequency converter. 4. The frequency conversion speed regulation system establishes a special class for the provincial new material industry to coordinate and promote the transformation of the original speed regulation system. In order to ensure safety and reliability, let the frequency conversion speed regulation system coexist with the original speed regulation system, which is standby for each other and can be switched at any time. At the same time, in order to prolong the service life of the product so that the operator does not change the operating habits, the industrial and frequency conversion systems are operated with the original operating mechanism, as shown in Figure 2. Fig. 2 field application and operation effect of switching control of industrial and frequency conversion system 5 the energy-saving effect of the system after transformation is obvious, especially in inclined shaft single ditch and shaft mines, the power-saving rate is more than 30%. At the same time, the stability and safety of the winch operation are greatly increased after the frequency conversion transformation, so the operation failure and maintenance time are greatly reduced, and the output of the mining area is also greatly increased. User response was generally good