您好，Hubei Tiangong Electromechanical Technology Co., Ltd网站欢迎您！
Squirrel-cage asynchronous motors are commonly used in industrial and agricultural production machinery, especially in the power of smelting, mining, chemical industry transmission, pumps, crushing, fans and other machinery. Statistics show that about 2/3 of China's power generation is consumed by AC motors. Three-phase asynchronous motors have the advantages of simple structure, high efficiency, convenient control, reliable operation, easy maintenance and low cost. Three-phase asynchronous motors are used to undertake, so we have taken measures in various production areas to ensure the routine maintenance and overhaul of asynchronous motors. At the same time, by implementing automatic control of the AC motor, the purpose of control simplification and energy saving is achieved. The shortcoming of AC asynchronous motor is that it can't be smoothed, mainly because the inrush current at start-up is very large, and the starting shock torque generated is also relatively large. There are also many faults in the starting process, because it is difficult to start and we are helpless. The number of high-power motor shutdowns results in a large power consumption.
1, starting method and principle
In order to save investment targets in the traditional design, the method used for starting the large and medium-sized AC motors is to start directly at full pressure, and relatively large inrush current and impact torque appear, which may cause interference to other loads on the power grid and the power grid. It even affects the safe operation of the power grid. Therefore, according to different working conditions, many kinds of decompression starting methods have been adopted. The early measures include series reactance or resistance, series autotransformer, star-delta conversion. Since the 1970s, soft start with thyristor voltage regulation technology has appeared, and the analog control circuit has been replaced by a single-chip microcomputer, and it has developed into an intelligent soft start. Soft start is a new type of motor control device that integrates various softening functions such as soft start, soft stop and light load energy saving. In recent years, more mature ones have liquid resistance start, solid state soft start and high voltage inverter start.
2, the choice of soft start mode
The high-pressure cage type liquid resistance starter is at the cost of losing part of the starting torque, but for high-voltage high-voltage AC motors that are not constant torque (such as fans) or light-load starting, the grid capacity is not large enough or instantaneously dragged. One of the best ways to take it when the impact of a moving machine is large. GZYQ high pressure liquid rheostat soft starter is available.
The condition of the cage type asynchronous motor adopting decompression starting is as follows: First, when the motor is fully pressed, the production machinery cannot withstand the impact torque at this time; second, when the motor is fully pressed, the terminal voltage cannot meet the requirements; When starting the pressure, it affects the normal operation of other loads.
The traditional decompression starting method of the asynchronous motor has a star-delta starting, etc., all of which belong to the staged decompression starting. There are obvious disadvantages, that is, a secondary inrush current occurs at the time of starting. Therefore, soft start is currently popular.
The basic principle of the desulfurization induced draft fan drag system is that the original straight-lined sulfur-containing sintering flue gas is led to the desulfurization device through the induced draft fan to be desulfurized and dusted, and then discharged into the atmosphere to reduce environmental pollution. If the electro-hydraulic varistor technology is applied to the start of a ten-kilovolt high-voltage motor of a desulfurization induced draft fan, the motor starting time can be extended by 60 seconds or more. Besides, the price of equipment is also relatively low, only a few hundred thousand yuan. It is obvious that the soft start greatly improves the starting performance of large motors.
3. System composition and performance characteristics of high pressure cage type liquid resistance starter
The high-pressure cage type liquid resistance starter adopts PLC control, and the internal position signal of the liquid level, the moving plate, etc., and the opening and closing signal of the star point are all necessary interlocking. When the condition does not meet the starting condition, the device is locked, not The main motor is allowed to start, ensuring safe and reliable operation of the equipment.