Application of the hottest magnetic control soft s

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Application of magnetic control soft start in coking transformation project of Jinzhou Petrochemical Company

in the coking transformation project of Jinzhou Petrochemical Company, the high-voltage motor of the 'decoking' high-pressure water pump needs soft start. Due to the particularity of the process, the start-up is relatively frequent. Therefore, the measurement and control system adopts high-precision digital servo valve, and Jinzhou Petrochemical Company does not use hydraulic resistance soft starting device. The reason why Jinzhou Petrochemical Company does not use variable frequency soft start is that the price of the device is 4-5 times higher than that of magnetic control soft start, and the maintenance amount of long-term use is also higher than that of the latter

I. magnetic control soft start

magnetic control soft start is derived from reactor start. The common point of the two is to use reactors in series at the stator side of the motor to realize voltage reduction. The main feature of magnetic control soft start is to replace reactors with controllable saturated reactors. In the magnetic control soft starting device, the SCR three-phase bridge rectifier circuit controls the motor current through the power and voltage amplification of the saturation reactor. Different from SCR soft starting device, high voltage resistance and large current flow here are completed by saturated reactor

technical advantages of magnetic control soft start: reliable, cheap, and low environmental requirements

II. Basic information of Jinzhou Petrochemical decoking water pump motor (1). Purpose: drive the high-pressure water pump to realize the "decoking" process. It is started at least twice a day, with an interval of about 4-5 hours

(2) simulation (program name: MAG):

① some data input: 1. The rated line voltage of the motor is (V):6000, 2. The rated current of the motor is (a):354, 3. The rated capacity of the motor is (kw):3150, 4. The rated speed of the motor is (RPM):2985, 5. The ratio of locked rotor current to rated current of the motor is: 7.3, 6 When the motor starts at full voltage, the ratio of magnetic torque to rated value is: 1.1, 7. The ratio of maximum torque to rated value under the rated voltage of the motor is: 2.2, 8. The rated voltage of the motor 2. The no-load stator current under the problem of the experimental stroke is (a):60, 10. The total flywheel inertia converted to the motor shaft (n · m):5330, 11. The number of simulation steps is: 2000, 12 The simulation time is (seconds):30, 3 There is contact between the toothed bar pressing plate and the toothed bar 13. The given value of constant current is (a):1200, 18. The impedance is (Ω):0.45, 21. The time constant of inertia link between the given current and the actual current is (s):0.5

② some results of simulation:

2 groups of simulation curves are shown in Figure 1 and Figure 2. The starting completion time is (seconds):15.9, and the unit value of the maximum voltage drop is (%):14.6

③ the simulation results show that the soft starting current can be constant at 3.4 times the rated value, the soft starting time can be limited within 20 seconds, and the maximum voltage drop during the starting process is too large, but it can meet the requirement that the per unit value is not greater than 15%

v. operation condition

2 2 pump on load operation time: August 20, 2003

operation conditions: the opening of the inlet valve is 33%, and the outlet valve is reversed to the reflux direction (see the schematic diagram attached at the end of the text)

see Fig. 3 for the measured current time curve of soft starting according to the set 3.6 times of the rated current of the motor

test instrument used: digital oscilloscope, model: tds-1002

the time scale is 2 seconds per grid, and the completion time of soft start is about 17 seconds. The vertical coordinate is 260a per grid, and the maximum multiple of soft starting current is 3.6 times. During soft start, the pointer meter shows that the electric voltage drops from 6100v to 5200v. Pressure drop


Jinzhou Petrochemical Company believes that the operation has achieved the expected effect

Jinzhou Petrochemical Company originally prepared to replace the aluminum core cable with copper core cable in the transmission cable. After replacement, the electric short-circuit capacity will be increased and the voltage drop will be reduced

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