What are the similarities and differences between traditional relay contactor control and PLC contro

It's all done according to a logical relationship! The difference is that the control process of the relay - contactor, there are too many wires, which takes up too much space, and it is not easy to check the line in the later maintenance; The PLC control is much more convenient, the internal program replaces most of the lines in the logic control, and the volume of the distribution cabinet will be greatly reduced! Later maintenance is also convenient!

The main advantages of PLC are:

1. Strong function and performance ratio.

High (It can be equivalent to integrating a lot of relays, most of the time the cost performance is not low, unless it is a simple circuit, only a few relays are used, then it may not be very practical.) ）

2. The hardware is complete, easy for users to use, and adaptable.

3. High reliability and strong anti-interference ability.

4. The design, installation and commissioning of the system have less work.

5. The programming method is simple.

6. The maintenance workload is less and the maintenance is convenient.

7. Small size and low energy consumption.

The similarities are the low-voltage control of the start-up of high-voltage equipment.

The difference is that the traditional hardware control loop requires a large number of relays, and the circuit is built and it is difficult to change.

PLC control can save hardware and is easy to modify. It is also convenient for over-finding errors and later maintenance.

Control design: action logic part.

Of course, there are many more functions such as detection, communication, etc.

Categories: Computer Network >> Computer Knowledge.

Analysis: These are two different means of implementing automatic control. The connection is that both approaches can basically achieve the same function.

Their application requires knowledge of "gate circuits". Gate circuits are knowledge of things like "AND gate", "NAND gate", and "OR gate".

Another connection is that with PLC control, relays may often be required when collecting input signals. When outputting the control signal, the relay is also used to do "power amplification".

What kind of control you want to achieve is determined by the object being controlled and the purpose of your automatic control. It has nothing to do with what means are employed.

The biggest difference between the two systems is the hardware used to implement the control logic.

The logic function of the relay control system is completed by the traditional relay, such as the control time, and there is a corresponding time relay. The action of relays is generally related to electromagnetism.

PLC is a spinning programmable controller, which is an integrated controller based on various "gate circuits". The formula is closer to that of a computer. For the lines that have been connected, the control logic and parameters can be changed by changing the program of the PCL, which has a more flexible application mode.

Another difference is that the relay control system is suitable for simpler logic control, while the PLC can implement more complex logic control.

1. The control logic is different.

Relay-contactor control: large size, complex wiring, difficult to modify.

PLC control: The storage logic is small in size, less in connection, flexible in control, and easy to expand.

2. The control speed is different.

Relay-contactor control: The control function is realized by the opening and closing of the contact, and the action speed is tens of milliseconds, and the contact jitter is prone to occur.

PLC control: controlled by semiconductor circuits, each instruction execution time is at the microsecond level, and there will be no contact jitter.

3. The time-limited control is different.

Relay-contactor control: Implemented by a time relay, with poor accuracy and susceptibility to ambient temperature.

PLC control: realized by semiconductor integrated circuit, high precision, convenient time setting, not affected by environment and temperature.

4. Reliability and maintainability are different "relay-contactor" control: short life, poor reliability and maintainability.

PLC control: long life, high reliability, self-diagnosis function, easy maintenance.

Compared with the relay contactor control system, PLC has the following advantages:

1. The hardware structure is simple.

2. The control logic is easy to change.

3. The system is stable and easy to maintain.

Working principle of vacuum AC contactor:

The vacuum contactor uses vacuum as the arc extinguishing medium, and its main contact is sealed in a special vacuum interrupter tube. When the operating coil is energized, the armature engages and the contacts close under the action of the contact spring and the self-closing force of the vacuum tube. When the operating coil is de-energized, the reaction spring overcomes the self-closing force of the vacuum tube to release the armature and the contact is disconnected.

When the contactor breaks the current, platinum scale formed by metal vapor will form in the contact gap, which will affect the service life of the contactor. <>