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Tension measuring circuit of aluminum strip slitter

on the research and engineering demonstration of the incombustible exterior wall insulation and decoration system with high combustion level, low smoke toxicity, good decoration effect, long service life, and compatibility of insulation and decoration, the uncoiling tension is controlled by the pneumatic holding brake on the 1 longitudinal shear train in the finishing workshop of Southern Aluminum (China) Co., Ltd., and decreases with the reduction of coil diameter through the follow-up small pressure wheel pressed on the aluminum coil of the uncoiler, Thus, the brake air pressure is controlled to make the friction torque proportional to the winding diameter and keep the tension constant. The adjustment of the linear speed of the machine train is completed by the coiler. In this way, it is impossible to see whether the system has constant tension through the winding ammeter on the console, because when the voltage at both ends of the motor armature of the coiler is less than its rated voltage, the speed regulation is achieved by regulating the voltage, and the motor magnetic field is constant. Since the uncoiling tension is constant, the armature current of the coiler increases in proportion to the coil diameter, which cannot reflect the magnitude of the tension (at this time, the current is changing, and the tension is constant). According to the needs of production, a tension detection circuit can be designed by measuring the operating parameters of the coiler and the tension calculation formula

1 tension measurement principle

according to the principles of physics, there is the following relationship:

p=ei=ui η= Fv (1)

where p is the input power of the motor; U is the working voltage of the motor; I is the working current of the motor; E is the back electromotive force of the motor; η Is the efficiency of the motor; TM is the electromagnetic torque of the motor; Cm is the electromagnetic constant of the motor; Φ Is the magnetic flux of the motor; F is the tension of the strip; V is the linear velocity of the strip; D is the coil diameter; I is the reduction ratio of the mechanical system

(1) and (2) can be transformed into the following two formulas:

in formula (4), magnetic flux Φ Is the analog conversion value of excitation current, and the winding diameter D is the calculated value; In formula (3), u, I and V are all direct measured values. Therefore, according to the measurement requirements, formula (3) is more accurate, and through formula (3), enterprises with early and fast transformation in the industry can rely on excellent technology and products to calculate the maximum tension value generated by the equipment carried by the motor, so formula (3) is used as the design basis of this circuit

2 design of tension measuring circuit

2.1 calculation of the maximum tension of colorless crystal or white small spherical solid

the parameters of the coiler motor of the Slitting unit are shown in Table 1

the original equipment has two kinds of reels, 280mm and 500mm respectively. Now only 500mm is used, so the field weakening multiple of the motor is redundant. After readjustment, the excitation current is if=2.4 ~ 6.5A, and the speed is n=556 ~ 1500r/min, so as to adapt to thin plate production (for the maximum torque control method, the motor with smaller field weakening multiple can be selected)

maximum linear speed of train vmax= π × nmax × Dmin/i=330m/min (because the system is of constant linear speed, when the winding diameter is minimum, the speed is maximum)

because the tension control system has the property of constant power load, pe=fmaxvmax, there is the maximum tension

2.2 signal selection

according to the equipment parameters, tt300-t/s current transformer can be selected, with a rated current of 300A and a rated output of 150mA; TV100 － aw/500 voltage transformer, with rated voltage of 500V and rated output of 40mA; The tachometer is the original parameter, and the corresponding output of 330m/min is dc37.5v. The signal conversion circuit is shown in Figure 1 by pressing the "swing taking" button

2.3 design of tension measuring circuit

2.3.1 selection of tension meter

calculate the actual full-scale tension by selecting the parameters of the detection element, η Take 88%

therefore, a DC voltmeter with a range of 10V is selected, so that 10V corresponds to 24kn scale as tension display

2.3.2 tension measuring circuit

multiply and divide the converted signals of u, I and v. the actual circuit is shown in Figure 2

n5 is the multiplier, N6 is the divider, and N4 is the maximum output operating point adjustment. When the conversion signals of input u, I and V correspond to the maximum value, adjust the potentiometer rp7 so that the indication of the tension gauge is 10V, corresponding to 24kn

3 application effect

this circuit has been able to detect the actual tension of the strip since it was put into use in the 1 longitudinal shear train of Southern Aluminum (China) Co., Ltd. in October 1996. Compared with the theoretical calculation value, the tension fluctuation range is less than 3%. It is easy to use. Although the brake air pressure is adjusted in the uncoiler, it can be reflected from the tension gauge

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