Application of domestic rare earth permanent magne

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Application of domestic rare earth permanent magnet AC servo motor in horizontal continuous casting 1. Overview horizontal continuous casting technology is a new continuous casting technology that appeared in the 1980s. Horizontal continuous casting is widely used in metallurgical industry because of its simple process, high efficiency and good product quality. Billet drawing technology is the core of horizontal continuous casting technology. In order to make the crystallization of liquid metal in the mold more sufficient and uniform, the drag system of billet drawing should complete the reciprocating variable speed movement of pull stop push stop pull through multiple drive motors. This puts forward high requirements for the response time, follow-up, synchronization and other technical indicators of the drive system

Shandong Dingxi special steel's continuous casting and drawing production line was a new project in 2002. The production line adopts the rare earth permanent magnet AC servo motor (3 sets, 15kw/set, model: tysz-) of Zhejiang Zhongyuan Electric Co., Ltd. and is equipped with the F5 servo controller of German KEB to realize the speed synchronous control function and master-slave synchronous control function. It has fast response, accurate positioning and good synchronization. It passed the on-site commissioning in July 2003. At present, it operates well, and all performance indicators have fully met the requirements of the drawing process of horizontal continuous casting

II. Performance characteristics of Zhongyuan Electric TYSZ series rare earth permanent magnet AC servo motors

1. High speed regulation and positioning accuracy

2. Fast dynamic response (small electromagnetic time and electromechanical time constant)

3. High sensitivity (low starting voltage of motor)

4, wide speed regulation range and strong overload capacity

5, large power range, up to 75kW

6, good linearity and small torque fluctuation

7. Large power density, small volume and light weight

8, low loss and high efficiency

9. Low noise, low temperature rise and long service life

III. brief introduction of continuous casting servo drive system

the motion curve of continuous casting blank drawing is an analog waveform similar to sine wave. It is controlled by single-chip microcomputer program, and the frequency and speed of blank drawing are adjusted through keyboard input and monitor. The operation is simple and fast. The servo controller drives the motor by receiving the switching value control signal and the analog speed setting signal of the single chip microcomputer. The single-chip microcomputer detects the motion track of the motor rotor in real time through the position feedback signal, and realizes the position closed loop of the control system to ensure that the motion track of the motor meets the process requirements. See figure I for the control diagram of horizontal continuous casting process flow and figure II for the control system block diagram

IV. technical requirements of the drawing process for the drive system

according to the control requirements of the drawing process, the speed given signal (analog quantity similar to sinusoidal waveform) is output by the single chip microcomputer and sent to the servo controller through the shielded communication cable to drive the servo motor to realize reciprocating variable speed movement. The actual running track waveform of the motor must follow the given signal curve quickly, synchronously and accurately in order to complete the drawing process. This requires that the drive system must meet the following technical requirements:

1, response time

the casting frequency is generally times/min (adjustable), and the casting speed is generally meters/min (i.e., rotating, adjustable). Such a complete pull stop push stop pull operation process takes about 0.3s-0.8s. Among them, the time required for the pulling process is 0.2s-0.6s, and the response time is the highest. The response time of the rare earth permanent magnet AC servo motor (15kw) of Zhongyuan Electric is about 150ms (corresponding to 1000 revolutions), which can fully meet the requirements of the blank drawing process for the response of the motor at the beginning

2. Follow up performance

the quality of continuous casting slab is directly affected by the follow-up performance. If the following property is not good, it is difficult to control the amplitude and time of pulling, stopping and pushing, which will cause uneven crystallization in the billet and defects such as wrinkles and cracks on the surface. The rare earth permanent magnet AC servo motor (tysz-) of Zhongyuan Electric is equipped with the servo controller of KEB in Germany, and the sampling time can reach s before the plastic profile is extruded as fast as 0.5m. Moreover, the permanent magnet structure of the rotor determines the strict correspondence between the speed and frequency (n=60f/p). When the number of poles is certain, the number of motor revolutions per unit time only changes with the change of frequency, which completely overcomes the disadvantage of slip of asynchronous motor, Higher control accuracy

3. Synchronization performance

in this system, three servo motors drive three pressure rollers respectively, and the synchronization between motors is required to be high. The billet surface has solidified after cooling, and it is a rigid object. If the synchronization is not good, there will be some phenomena such as slipping of a motor drive roll and inconsistent output, which will affect the quality of the billet in slight cases, and cause major accidents such as failure to produce normally and shutdown in serious cases

the servo system adopts speed synchronous control function and torque control function. Speed synchronization control is adopted in the casting starting stage, because at this time, the drive rollers of the three motors are running in the traction dummy bar, and the pressure rollers on each drive roller need to be lifted separately to let the connection between the dummy bar and the billet pass through. In this stage, the torque control requirements between the three motors are not high. When the billet passes through three drive rollers after several hours of competition, the master-slave synchronization is realized by torque control. At this time, because the driven billet is a rigid object, when there is no slip, the linear speed of the driving rollers of the three motors is strictly consistent. At this time, the speed of the drive roll is controlled by the host, and the actual torque of the host is output through the analog port, which is given as the torque of the slave, and the output torque of the control slave is consistent with that of the host. This not only ensures the consistency of the three motors in speed, but also ensures the load balance of the three motors

4. Anti interference performance

interference is a problem that every set of electrical equipment will encounter. Small will affect the accuracy of control, large will make 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 the stable operation of the system

during the on-site commissioning of Shandong Dingxi special steel, the drive system had two failures: the first was that the motor generated regenerative energy during the rapid braking process, resulting in the automatic protection of the DC bus voltage of the controller due to high voltage, and the failure was removed after adding energy consumption braking resistance. The second time was that the actual speed curve of the motor was deformed due to the positive deviation of the blank drawing analog signal after it was transmitted to the controller. After inspection and testing, it was found that there was a problem with the program control module of the blank drawing waveform. After the processing of the program debugging personnel, the fault was eliminated

in the past year, the horizontal continuous casting production line of Shandong Dingxi special steel has operated stably, and the driving system has not failed once. The total billet output has reached more than 20000 tons, and the billet quality fully meets the standard requirements. The domestic rare earth permanent magnet AC servo drive system has been successfully used in horizontal continuous casting

v. comparison of various drive systems

VI. performance comparison of servo motor with asynchronous and synchronous motor

VII. Summary

the main problems existing in the application of domestic rare earth permanent magnet servo motor are: the system composed of machines has the advantages of diversified control methods, high control accuracy, obvious energy saving effect, stable operation, etc., which is close to the international advanced level, and the after-sales service is more comprehensive and fast, saving users' expenses. At present, TYSZ rare earth permanent magnet AC servo motor has been widely used in metallurgy, printing and dyeing, packaging, textile, printing, military industry and other industries, and the use condition is good. With the continuous expansion of application fields and industries, domestic rare earth permanent magnet servo motors are also maturing and improving

The successful application of rare earth permanent magnet AC servo motor and its drive system in continuous casting production line shows that the system composed of domestic rare earth permanent magnet servo motor (especially high-power servo motor) and high-performance servo controller can fully meet some high-performance technical requirements, which is a system scheme with high cost performance. (end)

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