1 Introduction Supercalendered paper is referred to as SC paper for low cost of groundwood pulp, chemical mechanical pulp or waste paper deinked pulp, and wheat straw pulp as the main raw materials, together with a small amount of long-fiber chemical pulp, and added more than 30% of the filler. It has a smoothness of 500S or more, an opacity of more than 85%, an average length and breadth of cracks of more than 3,000m, and its quality can be comparable to that of a low-quantity coated paper. It can be used for color printing of advertisements, catalogs, and inserts. Because the process uses a large amount of fillers and high yields of groundwood or chemical pulp, fiber and wood resources can be saved, which can greatly reduce costs. After the paper sheet is calendered by the calender, it can improve the smoothness, gloss and tightness of the sheet, and make the full thickness of the sheet uniform, thereby improving the appearance quality of the sheet and reducing the air permeability.

The supercalender shown in Fig. 1 is mainly divided into a unwinding device (also known as a paper retractor), a calender roller device (including a main motor), and a rewinding device. From the unwinding device, the base paper passes through the paper roll rollers and the chilled casting roll, and then enters the center winding. This article discusses how to use frequency control to complete the super calender drive control.

[center] Figure 1 Super calender schematic [/ center]

2 Variable frequency control of super calender 2.1 Open loop tension control scheme The super calender must ensure that the tension of the paper sheet is constant during quick start, quick stop and intermediate continuous speed adjustment, otherwise the paper sheet received will be curled and folded. Even fractures seriously affect the quality and yield of production. In this system, a combination of frequency converters is used to achieve precise tension control. We know that under normal circumstances, two ways can be used to meet such requirements: First, by controlling the speed of the motor, and second, by controlling the torque of the motor. achieve. Since the cost and conditions of installing the tension sensor are taken into consideration, open loop tension control is used. Of course, in this control mode, the tension of the paper sheet must be known, but it is obtained through the internal detection and calculation of the frequency converter, thereby reducing the cost and difficulty of the system.

The torque command of the inverter can be calculated from the set tension and the roll diameter of the reel. The formula is as follows:
T=(F X D) / (2 X i )
Among them: T is the output torque instruction of the frequency converter; F is the tension setting instruction; D is the winding diameter of the reel; i is the mechanical transmission ratio.
The program must take into account the line speed detection signal, coil diameter calculation and tension taper control, so as to accurately control the torque output of the motor and keep the tension constant.

2.2 Frequency conversion fabric of super calender The calculation of the main transmission power of the super calender can be based on the following:
P = K x B x V x N
Among them: P is the electric motor power (KW); K is the constant coefficient, generally takes 0.015~0.026; V is the working vehicle speed (M/min); N is the roller number (root).
Taking a paper mill in Sichuan as an example, a 12-roll supercalender is used. The rolled paper is 1M wide and 10um thick. The design speed is 250 meters per minute. The power of the selected main traction motor (inverter) is: P = 0.018 X 1 X 250 X 12 = 54KW, so the 55KW inverter can be used.
This system uses high-performance vector inverter TD3000, the configuration is as follows: Main traction inverter: TD3000-4T0550G, winding inverter: TD3300-4T0055G. In addition, the winding motor adopts variable frequency motor and installs rotary encoder (Omron, 1024 line output)

[center] figure two super calender electrical configuration diagram [/ center]

2.3 Frequency Conversion Speed ​​Control Description This system uses TD3000 vector open-loop control to drive the main drive motor. The rewinding frequency converter TD3300 adopts open-loop tension control mode. The speed of the main traction is given by AI1 input, and the control accuracy is 1%~0.5%. The TD3300 uses the analog output AO2 of the TD3000 (the output frequency of the TD3000 drive) of the pre-stage main traction inverter TD3000 to obtain the line speed and calculate the coil diameter; the tension setting signal is obtained by AI1; the signals of the rotary encoder are respectively received. PGP/COM/A-/B- ports.

3 Steps for debugging the super calender winding inverter 3.1 Preliminary check of the inverter, motor, rotary encoder wiring and nameplate parameters.
Motor nameplate: rated power 5.5kw, rated voltage 380V, rated frequency 50Hz, rated current 11.6A, rated speed 1440RPM.
Rotary encoder: Omron 1024 line output, supply voltage 24VDC, A\B\Z open collector output.
3.2 Complete self-identification of the motor parameters of the inverter Check the no-load current of the motor identified by the inverter. The no-load current of the motor should be within 30% to 50% of the rated current of the motor. The actual no-load current of the motor identified by the TD3300 inverter is 4.9A, which is 42% of the rated motor current, within the normal range.
3.3 Preliminary Test The drive capability of the drive to the motor The TD3000 drive is set to open-loop vector control mode, the TD3300 is set to closed-loop vector control mode, and the TD3300 drive is to set the encoder parameters (FB.00) in the (FB encoder function entry). = 1024), in the keyboard control mode to test the drive capacity of the drive for the motor, focusing on the stability of the output frequency of the inverter and the output current size, with particular attention to the output current of the TD3300 inverter, if it is under no-load conditions, If the output current is too high and an overcurrent fault is reported, the A/B phase connection of the rotary encoder should be incorrect. Replace the A/B phase connection or change the direction setting of the PG connection in the inverter (function code FB.01).
3.4 Completion of signal interface test of TD3000 and TD3300 Complete the relevant parameter settings of analog output AO2 (F6.07=1) of TD3000 inverter and analog input AI2 (F6.01=0, F6.04=1.0) of TD3300 inverter. Check the jumper of the V/I port on the interface board AI2 of the TD3300 inverter at the I side, and correct the linearity of the TD3000 analog output AO2 output and the corresponding TD3300 analog input AI2 (temporarily modify the TD3000 drive AO2 port (F6. 07 = 0) To set the frequency output, set F3.03 = 0, by changing the value of F3.04 can change the output value of AO2, when using TD3300 keypad to stop, it can display the input voltage value of AI2 - set FD. 02 = 1024, in the case of TD3000 and TD3300 power-on, modify the TD3000 inverter F6.10-AO2 offset adjustment and F6.11-AO2 gain settings to complete its linearity correction).
3.5 Set other relevant operating parameters of the TD3000 and TD3300 inverters, with initial commissioning test operation.
F3.06=3, open-loop tension control mode;
F1.00 = 2.81, the speed ratio of the winding motor and the winding reel provided by the equipment manufacturer;
F5.03 (multi-function terminal X3) = 12, roll diameter reset 1 command;
F8.00=0, rewind mode;
F8.01=1, AI1 setting;
F8.03=1000, modify according to the on-site debugging situation, meet the adjustment requirements of the tension setting potentiometer;
F8.08 = 0, initially set coil diameter does not calculate, to ensure the stability of the tension in the initial test;
F8.09 = 500, provided by the equipment manufacturer, the proposed value is slightly larger than the value provided by the manufacturer;
F8.10=170, supplied by the equipment manufacturer, diameter of air-core reel;
F8.12=170, for roll diameter reset, used with F5.03 (multi-function terminal X3)=12, roll diameter reset 1 command;
F8.16=170, Calculate the output torque of the inverter when the TD3300 inverter is initially started.
F8.17=0, positive, since the winding motor is in the electric state, the torque output should be in the same direction as the rotation speed, that is, in the forward direction.
After the parameters are set, the equipment runs well. The customer reports that as the coil diameter increases, the tension becomes smaller and smaller, which is the result of the uncalibrated coil diameter.
3.6 increase the volume diameter calculation function, again with load operation F8.08=1, set the coil diameter source selection line speed calculation method;
FC.00=2, AI2 setting, output from AO2 (operation frequency) port of main traction frequency converter TD3000.
FC.03=250m/min, provided by the equipment manufacturer, FC.00*FC.03= current line speed V, the frequency converter calculates the current coil diameter according to the formula: D=(i*V)/(л*n);
FC.04=80 m/min to prevent the TD3300 inverter from inaccurately calculating the coil diameter when the speed is low. When the line speed of the TD3300 inverter is lower than the set value of FC.04, the volume is The diameter calculation function stops and the current coil diameter value is maintained. When the line speed of the TD3300 inverter is greater than the FC.04 set value, the coil diameter calculation function is enabled again.
The test was again loaded and the tension in the winding process was stable to meet the requirements. However, the customer reported that the TD3300 had a sudden increase in torque at the start of the TD3300 and the paper was easily broken. The F3.12 function item was modified to cause the torque ramp mode at the start of the TD3300 inverter to slow down the sudden change in the torque at start-up, thus fully satisfying the customer's process. Claim.
(Note: This system has a constant tension in the whole process due to the small inertia of the equipment, and no inertia compensating function and tension taper control function are used.)

4 Conclusion After the system adopts the TD3000+TD3300 frequency conversion winding scheme, the on-site configuration is simple, the work is stable, and the debugging is convenient. The actual winding effect is very ideal, with good finishing and stable tension. It is based on the tension control characteristics of the TD3300 inverter, coupled with its perfect function, high reliability and excellent cost performance, to meet the different requirements of users for textile, paper, metallurgy and other fields.