The first national non-ferrous gold, automation technology and application academic conference papers collection of high-pressure large-scale liquid soft starter on the application of 4 oxygen compressors Li Ping Jiangxi Copper Company Guixi smelter Jiangxi Guixi 335424 Abstract analysis of large liquid soft The structure start-up principle of the starting device, describes the large-scale liquid soft-start device on the 4 oxygen-making air compressor, the keyword liquid soft start device, the motor starting current, the classification number 7, the document identification code, 8 Wen Xinghao, 10044345200350053, 1 Overview, Guixi Smelter 4 Oxygen air compressor is a complete set of equipment imported from Germany. This equipment is the largest equipment of the whole plant of the company. It is the largest equipment of the whole plant. The drive motor is supported by Xian 8 company. Motor, the specific parameters are as follows: rated power 73, rated voltage 6000 rated current 793 people rated speed 1 due to Guiye system transformer impedance, small capacity, equipment is far from the system transformer 1.3 directly start the device is absolutely impossible to start the frequency, directly The investment is nearly 10 million yuan, and the foreign experts also stressed that the voltage of the step-down starting motor can not be lower than 80, otherwise electric The machine is not allowed. Considering the high investment cost of the variable frequency start-up, after careful research and calculation, it is decided to compare several kinds of step-down current limiting starting methods.
If the reactor or autotransformer is used to reduce the voltage, it is difficult to ensure that the startup air compressor process requires the startup time to be randomly adjusted according to the working conditions.
Start-up analysis of 2-phase asynchronous squirrel-cage motor The squirrel cage motor is widely used for general mechanical power drive because of its simple structure, reliable operation and convenient maintenance. However, the weakness of this type of motor is that the starting surge current is large.
The direct failure of the large squirrel cage motor has the major disadvantage of causing transient overload on the power grid, causing the grid voltage to drop and affecting the normal operation of other equipment on the network. It is an acceleration shock to the load that easily damages the equipment or shortens the service life of the equipment; There is an overcurrent surge in itself that affects the service life of the motor.
When the system power grid capacity is small, a small motor can be started directly, and a large and medium-sized motor adopts a step-down start. Even if the grid capacity is marginal, from the point of view of the protection equipment, as long as the load characteristics allow, it should also consider the use of step-down start-up, especially the air compressor pump and other equipment.
The squirrel-cage motor step-down current-limiting starting method has a reactor or an autotransformer. They all have their own advantages and disadvantages. Although they can achieve the purpose of step-down starting motor, the motor terminal voltage is low, the adjustability is poor, and the startup time is long. The starting torque is small, and when the motor is added to the full voltage through the short circuit of the switch or the contactor, the sudden change of the voltage may cause a sudden change of the current and cause a jump of the current, and the secondary impact of the large current is also received. Shortcomings.
3Structure selection of large liquid soft start device 3.1 Structure of large liquid soft start device The structure of large liquid soft start device is mainly composed of balanced phase electro-hydraulic electrode lifting mechanism with negative temperature characteristics and servo control system. The core part is phase. In the electrode and servo control part, in order to achieve the requirement that the starting time of the 4 oxygen-making air compressor can be adjusted randomly according to the working conditions, and the starting control precision is improved, we put forward higher requirements for the servo control system, and the driving motor of the electrode lifting device is changed to the frequency conversion. The device controls, so that the current detected by the servo control system can be compared with the current detected by the servo control system to compare the lifting speed of the control electrode driving motor to achieve the accuracy and starting time of controlling the starting current of the main motor.
3.2 Selection of large liquid soft start device According to the parameters of the motor, the liquid soft start device of 800065 high voltage AC motor is selected. Its rated voltage is 6 rated power 7300; rated current is 793; start time 3.34 oxygen air compressor motor Starting principle High-pressure vacuum switch 1 is closed. The phase electrode of the large-scale liquid soft-start device puts the stator circuit of the string motor, and the resistance is automatically cut off along with the motor time. As the step is gradually reduced, the voltage of the motor terminal is gradually increased, and the starting torque is gradually increased. Gradually increase, the motor speed gradually rises. When the motor speed is close to the rated speed, the high-pressure vacuum switch 201 is closed. At this time, the resistor is cut off and the start is completed. The motor automatically injects normal operation, and its electrical principle is sub-wired 14 large liquid soft. The use of the start-up device The device was completely installed in the month of 2002. The device was successfully started. The operation is still in good condition. The performance is stable and reliable. After testing, the maximum starting current is 2590, which is 3.27 times of the rated current. The load start time is 468, the starting minimum voltage is 65, the starting current is very stable, and the grid voltage drops.
Time, Tian 2 start current motor 奚逋 grid voltage change Line 5 type liquid soft start device features closed-loop current limiting control real-time detection and tracking control and start-up current, stable and reliable equipment performance, simple structure, low cost, easy to use and maintain current The stepless adjustment can be carried out randomly according to the process conditions; the shortcomings of the adaptability of the reactor autotransformer are overcome; the equipment starts smoothly without impact, the starting current is smooth, and there is no secondary current impact when the large liquid soft start device is removed; the reactance is overcome The autotransformer has the disadvantage of secondary current surge; the system power supply voltage drop is small, the line voltage drop is less than 10, which satisfies the system power supply requirements; there is no high-order wave generation for the power grid, gram, the inverter or the soft starter has The impact of higher harmonics on the grid.
6 Conclusion The large liquid soft start device is a new type of soft start device for pressure-off large-powered motor. Because it has simple structure, low price, easy to use and easy to maintain, almost maintenance-free starting current can be randomly adjusted according to the process conditions. The starting device is stable. The impact start current smoothing and other characteristics are widely used in equipment startup and have a tendency to replace the reactor auto-transformer step-down starting equipment. It is believed that this large-scale liquid soft start device has a good application prospect in Guiye through this use.
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