Modeling of operation of the automatic control system by downloading of APK-10A aggregat

Abstract

The electric drive is one of the most energy intensive consumers and converters (in mechanical) energy. In this regard, the issue of improving the efficiency of electric drives is relevant. The solution of this problem is possible with the use of optimal structures, laws of electric drive control, and the latest technical means. The theory of regulated electric drive is constantly evolving, especially in recent years, with the creation of new power semiconductor systems. This in turn led to the complication of calculating the characteristics of the drive in traditional ways or the use of assumptions by reducing the accuracy of calculations. Modern computer technologies give an opportunity to deeply and qualitatively investigate a regulated electric drive both in statics and in dynamics.

The industry produces an aggregate APK-10A, which is used for the simultaneous grinding of coarse fodder (hay, straw, etc.), silos, haylings, root crops, concentrated feeds and solutions of various additives for the purpose of the current preparation of full-range fodder mixtures in the feeders of the VRX farms and pig farms. On the unit you can also wash the root crops without shredding them.

The feed screw feed is regulated step by step (in 12 stages) by replacing the wreaths of the stars on its drive. That is, it is only the setting of the unit under the selected feed, and in the process of automatic load regulation is absent. The chip load level is controlled by ammeter readings.

Purpose – reduction of time and expenses in studies of regulated asynchronous electric drive by means of computer simulation.

The analysis of the electromagnetic processes of the regulated electric drive with a thyristor voltage regulator was carried out using the provisions of the theory of the electric drive and the statistical methods of processing the results of research on the physical and computer model in the MatLab system.

The even feed of the feed to the chopping chamber of the APK-10A unit is carried out by adjusting the rotational speed of the drive motor of the screw-feeder. The feed is fed by a loading screw-feeder to the chopping chamber. In the shredder engine when the load is changed, the current changes. The value of the current of engine loading is fixed by the transformer current sensor. From the secondary winding of the current sensor, the signal is fed to the frequency controller of the current from which the motor of the screw-feeder is powered. Depending on the load of the electric shredder, the frequency of the current at the output of the frequency controller is changed, and, accordingly, the speed of the screw-feeder rotation.

Many researchers have come to the conclusion that the transfer function of food

preparation machines through the input channel is the supply of product Q, the exit - the load of the driving electric motor is an aperiodic link of the 1st order with a delay.

The primary converter in this automatic control system is a transformer current sensor that measures the current in one of the windings of the drive motor of the chopper drum; the output value will be a voltage varying from 1 to 10 V depending on the load.

The transformation factor will be determined depending on the rated current of the engine, which is equal to 85 A.

Choose a transformer current sensor with a transformation factor: = 0,12 mark DTT-58. In relative units, taking into account net latency = 1.0.

The regulating body in this automatic system is a screw dispenser. Transmission function of the regulating body (dispenser) will be the inertial link.

An executive mechanism in this system is an asynchronous motor with a short-circuited rotor, which drives the dispenser.

For an adjustment object with an aperiodic function, a PI regulator (proportional to integral) is required. For the shredder under consideration, the gain of the PI regulator will be equal to k_P = 0,02; k_I = 0.01.

As a regulator, we choose the frequency converter FR-E540-1.5K, which works with an asynchronous dosing engine up to 1.5 kW.

The calculation results are presented below on the model.

To study the transients in the automatic shredding system, we compile a structural algorithmic scheme of optimal SAR, on the basis of which we build the model in the MatLAB system.

We conduct the research as follows. In relative units, we set different values of the control signal and using an oscilloscope we obtain the results of research.

Analyzing the transition process of regulation, it is possible to assess the quality indicators of regulation, which include:

- time of adjustment: tP - time during which the adjustment value changes to values within ε = ± 3%. Proceeding from this tP = 4,5 s;

- overregulation: σ - maximum deviation of the regulating value from the set value.

According to the results of the research it was established that the output signal corresponds to the controller, respectively, 1,0 and 0,8 units, that is, the control signal can be set to the magnitude of the load on the electric shredder. Time of the transient process (time of regulation) with tP = 4,5 s, which satisfies the conditions of operation of the electric motor in terms of heating it from the currents of the transition regime. The thermal mode of the electric motor will not be disturbed if the duration of the transient process does not exceed 5 seconds.

Thus, on the basis of the performed calculations for the automatic control system of the shredder APK-10A we choose such hardware:

• a screw dispenser with a motor-reducer МPz-2-31,5-90-КУ3 and an electric motor 4АХ71В2Р3 (РН = 1,1 kW, nH = 2810 rpm IN = 2,5 A);

• Frequency converter FR-E-540-1.5K;

• transformer current sensor DDT-58.

 The results of the research revealed that with the selected PI controller for the shaft load control system, with gain coefficients kP = 0,02 and kI = 0,01, the transition period does not exceed 5 s, which satisfies the conditions of regulation for heating the electric motor.

According to the research carried out on the computer model, equipment was chosen for implementation of the recommended drive control scheme.