The control cabinet is to assemble the switchgear, measuring instrument, protective device and auxiliary equipment in the closed or semiclosed metal cabinet or on the screen width according to the requirements of electrical wiring. and the safety of surrounding equipment. During normal operation, the circuit can be connected or disconnected by means of a manual or automatic switch. Cut off the circuit or alarm with the help of protective electrical appliances in case of failure or abnormal operation. Various parameters in operation can be displayed by means of measuring instruments, and some electrical parameters can also be adjusted to prompt or send out signals for deviations from normal working conditions. Commonly used in various power generation, distribution and substations.

Control system composition

Control Unit : HMI,PLC,DCS.

Meters: including conventional meters, smart meters, bus meters

Sensors and actuators: including conventional sensor actuators and bus type sensor actuators

Operating unit: including conventional buttons, indicator lights and bus button indicators

Composition of the control cabinet

Cabinet and installation accessories

Power distribution protection unit: including universal circuit breaker, load switch, air switch, fast fuse, motor circuit breaker, etc. Depending on the type of protection required, the protective device will not be the same

Control unit: including relays, contactors, soft starters, frequency converters, PLCs and interface modules

Terminals

what is a primary circuit

The primary circuit is commonly referred to as the main circuit.

    The primary circuit is responsible for the on and off of the power supply of the equipment (usually a contactor), and provides protection for equipment and lines (usually a circuit breaker, thermal relay, fuse, etc.).

What is a secondary circuit

The auxiliary circuit is also called the secondary circuit, which is a circuit for controlling, protecting, monitoring and measuring the main circuit. The equipment in the secondary circuit is called secondary equipment, and they include various control switches (such as buttons, etc.), relays, coils and auxiliary contacts of contactors, signal lights, measuring instruments, etc.

The difference between primary circuit and secondary circuit

1. Primary circuit A circuit directly connected to the AC grid power supply, such as: a device connected to the AC grid power supply, the primary winding of a transformer, a motor and other load devices. Secondary circuit A circuit that is not directly connected to the primary circuit, but powered by a transformer, converter or equivalent isolating device located within the equipment, or powered by a battery.

2. The power supply of the primary circuit is 220V and above AC. The power supply of the secondary circuit is 380V, 220V, 36V and other alternating current or direct current. 380V, 220V power supply can be obtained in the primary power supply. If it is high voltage at one time, you can also use a transformer to obtain 380V, 220V, 36V power; you can also use a rectifier and battery to obtain DC power.

Electrical control cabinet wiring

Wiring in the cabinet:

1. Open wiring:

Open wiring, also known as front-panel wiring, is characterized by clear wire direction and convenient fault checking, but the process requires

High requirements and slow wiring speed are suitable for equipment with relatively simple circuits and fewer electrical components. use

Pay attention to the following points when wiring.

1) BV-type single-strand plastic hard wires are generally used as connecting wires for open wiring.

2) The lines should be neat and beautiful, horizontal and vertical, and the corners should be at right angles;

The bundle is fixed; the laying of the wire does not affect the removal of the electrical components.

3) The wires and terminals should ensure a reliable electrical connection, and the wire ends should be bent into croissants; for different cross-sections

When the wires are connected in the same terminal, the large section is on the bottom and the small section is on the top, and each terminal is not in principle

More than two wires.

4) The wires should not overlap or cross as much as possible.

Dark wiring

Concealed wiring is also called behind-the-board wiring. It is characterized by neat and beautiful board surface and fast wiring speed, but it is difficult to check electrical circuit faults. The dark wiring should pay attention to the following points.

l) The installation holes of electrical components and wire threading holes should be positioned accurately and the hole diameters should be appropriate.

2) The connection wires between the front of the board and the electrical components must be in reliable contact, and the wires passing through the board should be perpendicular to the board surface.

3) When the switchboard is fixed, the side where the electrical components are installed should face the door of the control cabinet for inspection and maintenance, and a certain gap should be left between the board and the installation surface.