Emerson PLC and VFD (Variable-frequency Drive) are used in sizing machines

1. System Overview

The application of Emerson PLC and VFD (Variable-frequency Drive) on the sizing machine. This electrical system adopts PLC centralized management and decentralized control. The system is centralized, simplified, easy to control, and can better reduce the failure rate. The scheme configuration is as follows:

The PLC system consists of Emerson EC202416BAR main module, 16-point digital input module and 4-channel analog output module.

The operation interface adopts an industrial-grade LCD touch screen, which can dynamically modify the control parameters and conveniently display the current speed, current piece length, number of pieces and the dynamic operating status of the system.

The side shaft motor VFD (Variable-frequency Drive) adopts the high-performance and general-purpose EV2000 series, and the weaving beam winding TD3300 22KW tension VFD (Variable-frequency Drive). This VFD (Variable-frequency Drive) is a tension-specific VFD (Variable-frequency Drive) with built-in tension control function. It adopts independent frequency conversion mode, with simple structure, easy maintenance and high stability, ensuring the winding tension and linear speed, and is stable and reliable in the process of changing from small roll to large roll. The automatic compensation control during acceleration and deceleration makes the tension more stable during acceleration and deceleration. There is also a yarn breakage prevention program during winding, making it easy to operate when winding up the machine.

Advantages of this system:

The tension setting is set on the human machine, humanized operation;

Use advanced control algorithms: recursive calculation of roll diameter; linear increase of tension when hollow roll diameter is activated; application of tension taper calculation formula; dynamic adjustment of torque compensation, etc.;

The real-time calculation of the winding diameter is very accurate and ensures smooth performance of the winding motor output torque. In addition, the recursive operation of the curling diameter is added when calculating the curling diameter. When an operation error is made, the curling diameter can be corrected to the correct value by oneself;

Because the moment of inertia of the winding device is very large, when the winding diameter changes from small to large. If the operator accelerates, decelerates, stops, and reactivates, it is easy to cause yarn bursting and yarn loosening, which will directly affect the quality of the yarn. After the transformation of frequency conversion winding, the winding is very stable and the tension is always constant under various circumstances mentioned above. Moreover, after PLC processing, some dynamic adjustment measures are added to the specific dynamic process to make the winding performance better;

Based on the traditional mechanical transmission winding, it is transformed into a variable frequency winding, which is very simple and low-cost, and basically does not require modification of the original machinery. The transformation cycle is short, and installation and debugging can basically be completed in two or three days;

It overcomes the disadvantages of mechanical wear caused by mechanical winding and extends the service life of the machinery. Convenient to maintain equipment.

All operating parts on the machine use safety power below 36V to ensure safety during operation.

2. System block diagram

3. Tension control principle

The so-called tension control, in layman's terms, is to be able to control how much force the motor outputs, that is, how many Newtons it outputs. The output torque of the motor can be controlled by reacting to the motor shaft. Real tension control is different from a system that relies on the speed difference between the front and rear power points to form tension. The essence of adjusting the tension based on the speed difference is PID control of the tension, which requires the addition of a tension sensor. Moreover, the adjustment when starting, stopping, accelerating, decelerating, and parking the large and small rolls cannot achieve the effect of real tension control, and the tension is not very stable. It will definitely affect the quality of the product.

The essence of variable frequency winding is to complete tension control, that is, to control the operating current of the motor, because the output torque of the three-phase asynchronous motor T=CmφmIa is proportional to the current. And when there is a sudden change in the load, it can ensure that the mechanical characteristic curve of the motor is relatively hard. Therefore, vector VFD (Variable-frequency Drive) must be used, and encoder closed-loop control must be added. The essence of using VFD (Variable-frequency Drive) for constant tension control is infinite loop vector control, that is, adding encoder feedback. The winding warp changes from small to large. In order to ensure constant tension, the output torque of the motor is required to change from small to large. At the same time, corresponding torque compensation must be carried out during different operating processes. That is, when the small roll starts, accelerates, decelerates, stops, and when the large roll starts, different torque compensation must be carried out at different winding times. This can make the entire winding process very stable and avoid excessive tension when the small roll is started. ; The phenomenon of yarn loosening when starting a large roll.

Calculation principle of roll diameter

Calculate the winding diameter according to V1=V2. Because V1=ω1×R1, V2=ω2×Rx. Because the length of the yarn passed by the length measuring roller is equal to the length of the yarn received by the winding in the same time. That is, L1/Δt=L2/Δt, Δn1×C1=Δn2×C2/i

(Δn1---the number of turns of the traction motor running per unit time, Δn2---the number of turns of the winding motor running per unit time, C1---the circumference of the length measuring roller, C2---the number of winding pan head Circumference, i---reduction ratio)

Δn1×π×D1=Δn2×π×D2/i

D2=Δn1×D1×i/Δn2, because Δn2=ΔP2/P2

(ΔP2---the number of pulses generated by the winding encoder, P2---the number of turns of the winding encoder). Δn1=ΔP1/P1 takes Δn1=1, that is, the length measuring roller rotates once and is connected to the PLC by the encoder. Then D2=D1×i×P2/ΔP2, so the winding diameter of the winding head is obtained

Dynamic process analysis of winding

To ensure the stability of the winding process, the tension must be constant whether it is large winding, small winding, acceleration, deceleration, activation, or parking.