Zhukovskyy Oleksey

Faculty: Energomechanics and Automation Department

Speciality: Automatic control of technological processes

Theme of master's work:

Research of physical processes of electrotechnical complex working site by using quasi-frequency, and development of automatic anti-stopping device for mine scraper chaine

Scientific adviser: Marenych Kostyantyn

Introduction

Currently, for most of transporting machines and electric devices are used in antiquated systems with relatively low technical and economic indicators. Replacement of electrical equipment for the new is not always possible due to lack of funds from the customer. Therefore, the main thrust now - maintaining equipment in working condition and the continuous monitoring of its technical condition. Assessing the technical condition of the particular electromechanical system begins with a visual inspection of EIL, assessing the range of changes in the load of the cycle, the temperature of bearing assemblies, engine temperature, presence of grease, etc.. If you see an unusual noise, vibration system increases, the need to resort to methods vibration diagnostic-measure vibration velocity and vibration acceleration salient points in the system. Increasing the resource is directly related to the restriction of the dynamic loads of EMC. Therefore, the use of special units, nodes, limiting currents, the points forming the desired character of the executive body of the movement, supporting the power factor at the optimal level, will help extend the life of a particular equipment.

Survey of research and developments

With the advent of the power converter technology has become a real management of asynchronous motors by changing the parameters of the supply voltage - in particular, the simplest way to implement the management should be considered phase asynchronous motor. The method is based on three-phase thyristor voltage control systems and pulse phase control. The system of pulse-phase control is designed to create stimulating angles unlock thyristors voltage regulator, the diagrams of stresses SIFU explained With regard to AM, phase management is an indirect way to regulate the speed, because there is a quadratic relationship between the voltage and the electromagnetic momentum which has developed asynchronous motor. In this connection, the area of application of this method is limited to triggering device drives. When tyristors managing asynchronous electric all the time is in consistently changing each other transient conditions caused by switching thyristors. At each switching circuits in AM raises the electromagnetic transition process, due to changes in the magnetic state of the machine and hence the emergence of the free flow which interacts with the core (forced) is creating alternate transitional moments, the maximum values which can be an order of magnitude greater than the maximum value of the time promoted AM in a stable mode. Dynamic mechanical characteristics in contrast to the static represents the link between the instantaneous values of torque, and velocity of blood in the process of moving electric power from one equilibrium state to another. The static mechanical characteristic is the connection between the average values of the time and speed in the steady-state mode and is only a locus of equilibrium system, the engine load.

Starting characteristic of AM

Quasi frequency

Formation quasi frequency voltage is carried out through a network of frequency modulation of the voltage signal of reduced frequency. Thyristors TC include groups, alternating with a given sequence. Upon formation of the same harmonic composition phase voltage during one period of modulation commute six thyristors at regular intervals. The figure presents a diagram of forming stations quasi frequency load stresses in phases during one such time interval. Included thyristor VS1 determines the formation of a positive half voltage in phase A and thyristors VS4 and VS6 determine the formation of the negative half of stresses in phases B and C. On the t0 - t1 load attached to the linear voltage UAB. Therefore, phase voltage at the load attached to the entry of TC, determined by the expressions: Where ua, ub - voltage phases A and B chains

Forming of quasi frequncy voltage: A-Voltage diagramm; B-connection loading scheme; Animation was made in MP Gif Animator , contais of 7 pics with 20 ms delay

To implement the phase shift between the voltages U'A; U'B; U'C; equal 2ï / 3 rad., Each middle piece in half sinusoids of both polarities should be separated from the preceding and subsequent segments of sinusoids in the middle of other phases at intervals of time, at least equal to: TC / 6, with the orders of coincidence of alternating phases of the network and the switch; Tc / 2, with the orders of coincidence of alternating phases of the network and the switch. In determining the general course of the processes in the TC-AM, harmonic analysis, however, does not take into account a number of features. Each half quasi frequency voltage formed by the LC, is composed of alternating segments of sinusoid voltage network and breaks, as defined closed thyristors. Therefore, AM quasi frequency power may be represented as the process of filing for the stator voltage modulating frequency. These ratios quasi frequency and the nominal starting currents of blood necessitated limiting the duration of power quasi frequency AM using the criteria of its heating, or the introduction of the phase values quasi frequency voltage regulation.

Conclusion

Thus, based on analysis of existing technical solutions, found that the most applicable in terms of solving the automatic removal gumming SC, is the power quasi frequency AM using frequency modulation: 7.14 Hz (in a direct way) and 10 Hz in the opposite direction . In this case, a possibility of sustained work at a reduced velocity of blood pressure with increased 2-fold starting point. However, preliminary simulations revealed that the presence of high levels of EMF motor inverse modeling of frequency can be changed by the actual moment of switching thyristors power switch and increased consumption of current. In this regard, the scientific validity of the study are the processes in AD, with V power to determine the amplitude and phase of the reverse EMF.

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