Asynchronous 3-phase motor reverse control system

Contents

Task

Introduction

1. Engine

2. Magnetic starter selection

3. Selection of thermal relays

4. Control circuit calculation

4.1 Selection of control buttons

4.2 Selection of light signalling

5. Transformer calculation and selection

6. Selection of fuses

7. Select a circuit breaker

8. Principle of circuit operation

9. Conclusion

List of literature

Introduction

Modern automated electric drives are complex dynamic systems, including linear and non-linear elements, providing a variety of static and dynamic characteristics in their interaction. The acquisition of skills in the design, calculation and analysis of such systems is important in the training of specialists in the field of automation and mechanization of modern production.

The wide development of self-propelled guns by industrial equipment in mechanical engineering is associated with the use of a rich arsenal of technical means, among which electric devices and devices have an important place.

Electric elements of automation perform numerous functions in control systems related to processing of input information, internal conversion and matching of signals, storage of information, performance of logical operations, generation of executive signals and their use for process control.

Electroautomatics takes on increasingly complex control functions, usually based on contactless devices. This significantly improves the reliability and speed of control systems, reduces the size and mass of devices, and also allows you to implement many additional functions in control systems: troubleshooting, communication with the central control panel, etc.

Principle of circuit operation.

Electrical equipment is supplied via control center from three-phase AC mains with rated voltage of 380 V, frequency of 50 Hz. Allowable deviation of supply voltage: 15%... + 10% from nominal voltage.

The circuit provides remote start, reversal and shutdown, engine overload protection, self-start protection.

When QF1 circuit breaker is switched on, power is supplied to electric motor power circuit and to TS1 step-down transformer. At the same time, two lamps light up: HL1 - "network" and HL4 - signals the state of the engine - "shutdown." To start the engine, the operator presses the SB3 (or SB4) button depending on the direction of bitumen injection. In this case, the coil KM1 (KM2) is turned on, the contactor operates and turns on the contacts KM1 (KM2), that is, the start button is blocked, the "stop" lamp goes off, and the "forward" ("back") lamp lights up, electronic interlocking from simultaneous switching on of the contactors is activated. The engine is running. In case of overload (if stator current exceeds 1.1-1.2 nominal value for a long time), heat relays KK1, KK2 operate, disconnecting the control circuit, and therefore the engine power supply circuit .

To stop the engine, the operator presses the SB2 button, which breaks the control circuit (de-energizes KM, KM2). The lamp "stop" lights up.

To protect the network from short circuits, a QF1 circuit breaker with a dynamic release is used. To create a visible circuit break during repair work, it is enough to remove fuses from their sockets or turn off the QF1 machine.

In the event of an "accident," the operator presses the button SB1, which is located in the visible position of the control station and provides the same functions as SB2.

Conclusion

A scheme for connecting an asynchronous motor with a short-circuited rotor to the industrial network has been developed. The circuit provides: starting, stop and reversing of the electric motor; protection of the supply network against short circuit occurring in the equipment; protection of the electric machine against short-term and long-term overloads; protection against reintroduction of the unit (zero-protection); disconnection, ensuring safe repair and preventive work in the power circuit; signaling of modes and interlocks; emergency disconnection by the operator; galvanic isolation of power circuits and control circuits.

Спецификация.spw

Схема электрическая принципиальная.cdw