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Keywords direct drawing machine synchronous frequency conversion control
1.IntroductionMetal products are an important link in the metallurgical industry, but it is a weak link in our country. The machinery, electrical equipment old, hinders the development of the industry. In metal processing, direct wire drawing machine is a common one. In the past, it is usually realized by DC dynamo-electric unit (F-D system). Now, with the progress of technology and the popularity of frequency converter, frequency conversion control begins to be widely used in direct wire drawing machine. And through PLC to achieve drawing variety setting, operation automation, production process control, real-time closed-loop control, automatic meter counting and other functions.
The direct drawing machine adopts the frequency conversion speed regulating system, which saves energy significantly. The speed regulating range is 30:1 in normal operation, and can provide more than 1.5 times rated torque at 5% rated speed.
In this paper, the frequency conversion transformation of the direct wire drawing machine produced by a factory is taken as an example to illustrate the application process and effect of frequency conversion control.
2. Frequency conversion control system of direct wire drawing machineThe direct wire drawing machine mainly draws the stainless steel wire out of the fine rolling, the design process requirements are: (1) drawing speed 600m/min; (2) There are three main processing varieties, respectively, the inlet line 2.8mm→ outlet line 1.2mm, 2.5mm→1.0mm, 2.0mm→0.8mm; (3) No more than 2 emergency stop breaks.
Direct wire drawing machine is a kind of wire drawing machine difficult to control, because it is a number of motors at the same time to stretch the wire, the efficiency of the operation is very high. Unlike water tank wire-drawing machines and looper wire-drawing machines, which are often encountered before, the wire is allowed to slip between the molds. At the same time, it has higher requirements for the synchronization of the motor and the rapidity of the dynamic response. Due to the brittle characteristics of stainless steel material, the lack of toughness like high carbon steel wire or steel cord, it is easy to break in the process of operation.
This system has a total of 8 11KW frequency converters. The electrical configuration of the system is a looper, installed at the stage, which is used to pull the rolled stainless steel wire to the wire drawing part. Since the looper can slip freely, no special control is required for this motor. The drawing part has six rotating drums with a diameter of 400mm. A cylinder swing arm for detecting the position is installed between each drum. The position of the swing arm can be detected by a displacement sensor. When the wire is pulled tight, the wire will produce pressure on the cylinder of the swing arm to make the swing arm move down. Finally, the winding motor, this part of the self sliding conical bracket, the whole process of the diameter basically does not change, so there is no need to use the diameter calculation function. The eight motors use frequency conversion special motor power, and have mechanical braking device.
The system logic control of direct wire drawing machine is more complex, and there are various linkage relations, which are realized by PLC. The synchronization control is all realized inside the MD320 inverter in Huichuan, independent of external control.
Its working principle is: according to the operator in the panel set to determine the speed of the operation, the speed of the analog signal into the PLC, PLC considering the speed of the time after the output of the analog signal according to a certain slope. The purpose of doing so is mainly to meet the needs of some operations such as point moving, threading and so on. PLC output analog voltage signal at the same time to all inverter AI2 (AI1 can also) input terminal, as the speed of the main given signal. The signal of each swing arm displacement sensor is connected to the corresponding drum drive frequency converter as the feedback signal of PID control. According to the swing arm in the middle position, set a PID given value. This system is a very typical PID control system with feedforward, one stage in succession, PID as the fine tuning.
The Huichuan MD320 inverter was chosen because it can easily implement main speed following and PID tuning without the need for an additional control panel. In this system, the parameters are set as follows:
F0-03=2: The primary frequency source X is AI2
F0-04=8: auxiliary frequency source Y is PID
F0-07=1: Select primary frequency source X+ secondary frequency source Y
FA-00=0: PID The set source is the numeric keyboard set
FA-01=4: Set value of PID (the reference value of this value is the feedback amount of the system)
FA-02=0: AI1 is the feedback value of PID
FA-03=0: action direction of PID (when the feedback signal is greater than the feed time of PID, frequency output of converter is required to decrease to achieve PID balance)
FA-05=25: P value of PID
FA-06=1: indicates the I value of PID
FA-07=0.08: indicates the D value of PID
FA-08=0.1: PID? Sampling period of
FA-09=0: Deviation limit of PID
Since the stability of the system largely depends on the role of PID, the setting of its parameters must be taken into consideration at low speed, high speed, speed up and speed down. In addition, differential limiting must be added in this system.
3.Closing remarks
This system in the optimization of the parameter value, the equipment test speed of 600 meters /min is very stable, completely solved the original use of synchronous plate high speed under the instability problem (originally only open to 300 meters /min). Through the comparative test under various conditions, and the drawing machine with imported DC driver performance is the same, at the same time, the efficiency of the equipment is 90-95%, the power saving rate is about 40%. Moreover, the electrical device configuration of the system is simple, clear logic, and the cost is greatly reduced compared with the original, it is indeed a cost-effective.
