Fourth, the technical requirements of the drive system for the drawing process
According to the control requirements of the blanking process, the speed reference signal (approximating the analog quantity of the sinusoidal waveform) is output by the single chip microcomputer, and is sent to the servo controller through the shielded communication cable to drive the servo motor to realize the reciprocating shifting motion, and the actual running track waveform of the motor The given signal curve must be followed quickly, synchronously and accurately to complete the blanking process in its entirety. This requires the drive system to meet the following technical requirements:
1, response time
The drawing frequency is generally 80-200 times/min (adjustable), and the pulling speed is generally 0-2 m/min (ie 0-800 rpm, adjustable). Such a complete pull---stop---push---stop--- pull operation process takes about 0.3S-0.8S. The process required for pulling is 0.2S-0.6S, and the response time is the highest. The response time of Zhongyuan Electric's rare earth permanent magnet AC servo motor (15KW) is about 150mS (corresponding to 1000 rpm), which can fully meet the motor response time requirements of the drawing process.
2, follow performance
Follow the performance of the direct impact of the quality of continuous casting. If the followability is not good, then the amplitude and time of pulling, stopping and pushing are difficult to control, which will cause uneven crystallization inside the billet and defects such as wrinkles and cracks on the surface. Zhongyuan Electric's rare earth permanent magnet AC servo motor (TYSZ-1500-160) is equipped with the servo controller of Germany KEB. The sampling time can reach 0.5ms at the earliest. Moreover, the permanent magnet structure of the rotor determines the strict correspondence between speed and frequency. Relationship (n=60f/p), when the number of poles is constant, the number of revolutions of the motor per unit time changes only with the change of frequency, completely overcomes the shortcoming of the asynchronous motor, and the control precision is higher.
3, synchronization performance
In this system, three servo motors drive three pressure rollers respectively, and the synchronization between the motor and the motor is required. The surface of the billet has been solidified after cooling, and it is a steel object. If the synchronism is not good, there will be a phenomenon that the slip of the motor drive roller and the output force are inconsistent. When it is slight, the quality of the billet will be affected. In severe cases, it will not be able to produce normally. Waiting for major accidents.
The servo system uses speed synchronization control and torque control. Speed synchronization control is used in the casting stage, because the driving rollers of the three motors are operated on the traction spindle, and the pressure rollers on each of the driving rollers need to be lifted separately to allow the connection between the spindle and the billet. Through this stage, the torque control between the three units is not high. When the billet passes completely through the three drive rollers, the master-slave synchronization is achieved by torque control. At this time, since the driven billet is a steel object, the line speed of the driving rollers of the three motors is strictly consistent when there is no slippage. At this time, the driving roller speed is controlled by the host, and the actual torque of the main engine is output through the analog measuring port. As the torque of the slave, the output torque of the controlling slave is consistent with the host. This not only ensures the consistency of the speed of the three motors, but also ensures the load balance of the three motors.
4, anti-interference performance
Interference is a problem that every electrical device encounters. Smaller affects the accuracy of the control, and large makes the whole set of equipment unable to operate normally. The communication cable used in the servo system adopts multi-layer shielding, which has strong anti-interference ability and ensures stable operation of the system.
During the on-site commissioning process of Shandong Dingxi Special Steel, the drive system has two faults: the first time the regenerative energy is generated during the rapid braking of the motor, which causes the DC bus voltage of the controller to be too high and automatically protected. The fault is removed after the braking resistor is consumed. The second time, after the blank analog signal is transmitted to the controller, a positive deviation causes the actual speed curve of the motor to be deformed. After inspection and testing, it is found that the program control module of the blank waveform has a problem, after being processed by the program debugging personnel. The fault is eliminated.
In the past year, Shandong Dingxi Special Steel's horizontal continuous casting production line has been running stably, and the drive system has not experienced a failure. The total billet production has reached more than 20,000 tons, and the quality of the billet fully meets the standard requirements. The domestic rare earth permanent magnet AC servo drive system has been successfully used in the horizontal continuous casting.
