Development of relay-contactor control circuits

Contents

Introduction

1 Calculation, development and simulation of relay-contactor control system of DC motor

1.1 Calculation and simulation of natural characteristics of DC motor

1.2 Calculation of starting rheostat by graphical method

1.3 Calculation of starting rheostat by analytical method

1.4 Calculation of time delay and construction of transients during rheostatic start-up of DC motor

1.5 Construction and simulation of transients during rheostat start-up of DPT

1.6 Selection of braking type and calculation of braking resistance

1.7 Development of engine control system and selection of its components

2 Calculation, development and simulation of relay-contactor control system of asynchronous motor

2.1 Calculation and simulation of natural characteristics of asynchronous motor

2.2 Calculation of starting rheostat by graphical method

2.3 Calculation of starting rheostat by analytical method

2.4 Calculation of time delay and construction of transients during rheostatic start-up of asynchronous motor

2.5 Selection of braking type and calculation of braking resistance

2.6 Development of engine control system and selection of its components

3 Synthesis of discrete control system of asynchronous motor with phase rotor

3.1 Compiling algebraic expressions and synchronous motor control logic

3.2 Selection of element base for implementation of discrete control system of asynchronous motor

Conclusion

List of sources used

COURSE PROJECT ASSIGNMENT

Heading: Electrical devices

Project theme: Development of relay-contact control circuits

approved by the decision of the department No. 2 of 19. 10. 2015.

Initial data: for DC motor P62 to calculate rheostat, which performs automatic starting and control of engine speed at 5 stages; build and simulate start-up electromechanical characteristics and transient graphs [omega] = f (t) and I = f (t).

Develop a schematic control diagram that provides for automatic starting of the engine at any speed and dynamic braking as a function of speed. Select the control and switching equipment.

The moment of load on the engine shaft is jet. Moment of inertia of mechanism 3Jdv.

For the asynchronous motor MTN71210, calculate the starting rheostat, which starts the engine in 5 stages, build and simulate the starting mechanical characteristics and transient graphs [omega] = f (t) and I = f (t).

Develop a schematic control diagram that provides for automatic starting of the engine, reversing and braking by anti-switch in the function of current. Select the control and switching equipment.

The moment of load on the engine shaft is jet. Moment of inertia of mechanism 3Jdv.

Recommended literature: Veshenevsky S.N.. Characteristics of engines in electric drive. M.: Eliseev V.A. Relay-contact control systems of electric drive. M.: MPEI Publishing House, Leonenko A.S. Synthesis of discrete control systems. Publishing House of IrSTU, 2005.

Introduction

During the course design for "Electric sets" it is necessary to familiarize yourself with DC motors (DPT) and asynchronous motors. To complete the course project, you need to familiarize yourself with the disciplines: "Electric drive," "Electric devices." During the course project, all the necessary characteristics of the engines modeled in the Difsys program are considered, the controller in the Alpha program is programmed.

Modern adjustable electric drives for automatic lines and mechanisms are usually built on semiconductor devices. Relay and contact equipment in such drives is usually assigned the functions of turning on the power supply (connection to the network) of power units and control units, protecting and entering the initial and final commands into the drive control system. But along with electric drives performing complex functions, in some cases containing microprocessors or software control devices, there are a large number of electric drives that are assigned relatively simple functions. These are usually non-adjustable or adjustable stepwise in a small range of electric drives with low speed. The task of control systems of such electric drives is most often to organize starting, braking, switching from one speed stage to another, reversing and performing these operations in a certain sequence in time or according to commands from the working machine that completed the next technological operation. And it is not necessary that the control system performs all these functions: the set of functions depends on the requirements for the drive. Control systems for such electric drives are usually built on relay-contact equipment with a relatively small number of its actuations per hour, and with a large number of actuations - on contactless equipment.

Selection of element base for implementation of discrete asynchronous motor control system

We receive the programmable logic controller of the "Alpha2" series.

The controller of the "Alpha2" series is designed for application purposes for automation of lighting systems, air conditioning systems, control of electric drives of gate valves, gates, automation of water supply systems. The controller performs on/off cycles according to the program specified by the user.

The controller is designed for switching AC circuits with a voltage of up to 240 V. At the same time, it has 15 discrete inputs designed for the input current of each circuit up to 0.25 mA and 6 discrete outputs designed for the output current up to 10 A (under active load). Relays are used as output keys in the controller.

In the controller, it is possible to display both operating information and alarm messages (situations) on the liquid crystal display. The information is presented as a message of 12 characters and 4 lines. The image displayed on the display can be emailed using a GSM modem.

Programming and communication with peripheral equipment is carried out using the RS232C interface, through a specialized AL232CAB cable. ALPCS/WINE software allows you to create, save algorithms for the controller, and also makes it possible to change data, parameters within functional blocks and provide status control when performing an application task.

Conclusion

For DC motor P62 and for asynchronous motor MTN71210 according to passport data, we calculated the starting rheostat, built and simulated starting electromechanical characteristics and transient graphs.

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