Basic Definition
Electricity is a science that creates, maintains and improves the limited space and environment by means of electric energy, electric equipment and electric technology, covering the conversion, utilization and research of electric energy, including basic theory, application technology, facilities and equipment, etc.
Is electricity to appliances what weather is to the sky? Engaged in electrical industry for many years, but the connotation and extension of its definition are few. There is a discussion on the definition of electrical, electrical/Electrical Engineering (EE), which covers microelectronics, photonics, and microcomputer application technology. But it seems to be a little different from what we're talking about with electricity. However, you can be sure that what we agree with is that electrical appliances are specific object image, electrical is not touchable classification concept! Electrical includes electrical appliances. At the beginning of western industry, power machinery was driven by steam turbine, and then there was electricity, so "electrical", began to refer to industrial power, but now there is no steam turbine, so simply refer to electricity. The term "electrical" has been used so well that it is still used! Nothing fancy!!
Gas in electricity, when referring to "compressed air". Industrial automation, the need to move up the equipment, there are electric, pneumatic transmission, hydraulic transmission and other three. Electric and pneumatic are the most widely used power sources, which are combined to complete automation. So called: electrical automation.
ElectricalEngineering (EE) is one of the core disciplines in the field of modern science and technology, and an indispensable key discipline in the field of high and new technology. For example, it is the great progress in electronic technology that has promoted the arrival of the information age based on computer networks and will change the way people live and work. Electrical engineering is also promising, contributing to today's high student employment rate.
Electrical control system is generally called the secondary control loop of electrical equipment, different equipment has different control loops, and the control mode of high voltage electrical equipment and low voltage electrical equipment is not the same.
Main Function
In order to ensure the reliability and safety of the primary equipment operation, there are many auxiliary electrical equipment for the service, to achieve a control function of a number of electrical components, known as the control loop or secondary loop. These devices should have the following functions:
(1) Automatic control function. The volume of high voltage and high current switching equipment is very large, generally using the operating system to control the opening and closing, especially when the equipment fails, the switch needs to automatically cut off the circuit, to have a set of automatic control of the electrical operation equipment, automatic control of the power supply equipment.
(2) Protection function. Electrical equipment and lines will fail in the process of operation, and the current (or voltage) will exceed the range and limit of equipment and lines allowed to work, which requires a set of protection equipment to detect these fault signals and automatically adjust the equipment and lines (disconnect, switch, etc.).
(3) Monitoring function. Electricity is invisible to the eyes. Whether a device is powered or powered off cannot be distinguished from its appearance. It is necessary to set up various audio-visual signals, such as lighting and sound, to carry out electrical monitoring on the equipment.
(4) Measurement function. Lighting and sound signals can only show the working state of the equipment qualitatively (with power or power), if you want to know the working condition of the electrical equipment quantitatively, but also need to have a variety of instrument measuring equipment, measuring the various parameters of the line, such as voltage, current, frequency and power size.
In equipment operation and monitoring, the traditional operation components, control appliances, instruments and signals and other equipment can be replaced by computer control systems and electronic components, but in small equipment and local local control circuits still have a certain range of application. This is also the basis of microcomputer automatic control circuit.
System Composition
The basic loop of the commonly used control circuit consists of the following parts.
(1) Power supply circuit. The power supply of the power supply loop has AC380V and 220V, etc.
(2) Protection loop. The working power supply of the protection (auxiliary) circuit includes single-phase 220, 36V or DC 220, 24V, etc. It protects electrical equipment and circuits against short circuit, overload and voltage loss, etc. It is composed of fuse, thermal relay, voltage loss coil, rectifier component and voltage regulator component.
(3) Signal loop. The circuit that can reflect or display equipment and line normal and abnormal working status information in time, such as signal lights of different colors, sound equipment of different sounds, etc.
(4) Automatic and manual ask the way. In order to improve work efficiency, electrical equipment is generally equipped with automatic link, but in the installation, debugging and emergency treatment, the control line also needs to set up manual link, through the combination switch or transfer switch to achieve automatic and manual mode conversion.
(5) Brake and parking circuit. Cut off the power supply of the circuit, and take some braking measures to make the motor stop quickly control links, such as energy braking, power reverse braking, reverse pull braking and regenerative power generation braking.
(6) Self-locking and locking in the same way. After the start button is released, the line remains energized and the electrical equipment can continue to work is called the self-locking link, such as the moving and closing contacts of the contactor in series in the coil circuit. Two or more than two electrical devices and components, in order to ensure the safety and reliability of equipment operation, only one power start, the other can not power start protection link, called locking link. Such as two contactor moving break contact respectively in series in the other coil circuit.
