In the coking plant renovation project at Jinzhou Petrochemical Branch, the high-pressure motor of the 'coke removal' high-pressure water pump requires soft starting. Due to the special nature of the process, starting is relatively frequent. Therefore, Jinzhou Petrochemical does not use liquid resistance soft starters. The reason Jinzhou Petrochemical does not use frequency conversion soft starters is that the price is 4-5 times that of magnetically controlled soft starters, and the long-term maintenance requirements are also higher. I. Magneticly Controlled Soft Starters Magnetically controlled soft starters are derived from reactor starting. Using a reactor connected in series on the stator side of the motor to achieve voltage reduction is a common feature of both. The main characteristic of magnetically controlled soft starters is the use of a controllable saturated reactor instead of a traditional reactor. In a magnetically controlled soft starter, the SCR three-phase bridge rectifier circuit controls the motor current through the power and voltage amplification effect of the saturated reactor. Unlike SCR soft starters, here the high voltage withstand and high current flow are both achieved by the saturated reactor. The technical advantages of magnetically controlled soft starters are: reliability, low cost, and low environmental requirements. II. Basic Information on the Motor of Jinshi Chemical Coking Decoction Pump (1) Purpose: Drives the high-pressure water pump to realize the 'decoction' process. It is started at least twice a day, with an interval of about 4 to 5 hours between starts. (2) Simulation (program name: mag): ① Input data: 1. Rated line voltage of motor (volts): 6000, 2. Rated current of motor (amps): 354, 3. Rated capacity of motor (kilowatts): 3150, 4. Rated speed of motor (rpm): 2985, 5. Ratio of motor stall current to rated current: 7.3, 6. Ratio of electromagnetic torque to rated value when motor starts at full voltage: 1.1, 7. Ratio of maximum torque to rated value under rated voltage: 2.2, 8. No-load stator current under rated voltage: 60, 10. Total flywheel inertia converted to motor shaft (N·m²): 5330, 11. Simulation steps: 2000, 12. Simulation time (seconds): 30, 13. Constant current setpoint (amps): 1200, 18. Grid impedance (ohms): 0.45. 21. The inertial link time constant between the given current and the actual current is 0.5 seconds. ②. Partial simulation results: Two sets of simulation curves are shown in Figure 1 and Figure 2. The start-up completion time is 15.9 seconds, and the maximum voltage drop per unit of the power grid is 14.6%. ③. Simulation results show that the soft-start current can be kept constant at 3.4 times the rated value, the soft-start time can be limited to within 20 seconds, and the maximum voltage drop of the power grid during the start-up process is relatively large, but it can meet the requirement that the per-unit value is not greater than 15%. V. Commissioning status : Commissioning time of No. 2 water pump under load: August 20, 2003. Commissioning conditions: Inlet valve opening 33%, outlet valve reversed to the backflow direction (see the schematic diagram attached at the end of the document). The measured current-time curve of soft starting at the set 3.6 times the rated motor current is shown in Figure 3. Test instrument used: Digital oscilloscope, model: TDS-1002. The time scale is 2 seconds per division, and the soft start completion time is about 17 seconds. The vertical axis is 260A per division, and the maximum soft start current multiple is 3.6 times. During the soft start process, the pointer meter shows that the grid voltage drops from 6100V to 5200V. Grid voltage drop. Conclusion Jinzhou Petrochemical Branch believes that the commissioning has achieved the expected effect. Jinzhou Petrochemical originally planned to replace the aluminum core cable in the power transmission cable with the copper core cable. After the replacement, the grid short circuit capacity will be improved, and the grid voltage drop will also be reduced. References [1] Gao Yuenong Magnetic Control Soft Start Electrical Era 2002.10 [2] Gao Yuenong Chen Shengbo Electric Motor Soft Start Offline Simulation Electrical Engineering Technology 2003.1 [3] Gao Yuenong Yan Wenjin Three Paths to High Voltage Soft Start Electrical Drive Automation 2004.2