Basic knowledge of electric cabinet
There are two types of electric cabinet, one is the distribution cabinet, the other is the control cabinet.
The composition of electric control cabinet
From the perspective of structure, the electric cabinet is composed of a shell, steel structure and various mounting plates, as well as components, instruments, measurement and control devices and cables.
There are partitions in the electrical cabinet. The partition includes bus compartment, component compartment, outlet compartment and so on. Compartments exist to avoid arc shock and temperature rise.
We call the power transmission and control loop the primary loop, the implementation of measurement and control, data acquisition and amplification, display, information exchange loop called the secondary loop. Accordingly, the components in the electrical cabinet are also divided into primary circuit components and secondary circuit components. In addition, the primary loop is also called the main loop, and the secondary loop is also called the control loop.
Control system of electric cabinet
For primary circuit components, when a short circuit occurs, only circuit breakers and fuses can break the short circuit current, so the circuit breakers and fuses are called active components, and other electrical appliances, including bus bars, are called passive components.
Because the short-circuit current will produce electrodynamic shock and thermal shock to the electric cabinet, we divide the ability of the electric cabinet to withstand the electric dynamic shock degree into dynamic stability and thermal stability, dynamic thermal stability is the core technology of the electric cabinet.
For the electrical cabinet, the rating problem of the main circuit components is overload protection and short circuit protection, which we call overcurrent protection. Overcurrent protection is related to the design of the distribution system and the distribution network, to the grounding system of the distribution, to the load and load “of course, but also closely related to the wires and cables that the distribution system connects to the load.
The operation of the distribution equipment will produce temperature, we subtract the temperature of the distribution equipment from the ambient temperature, which is called temperature rise. There is a limit value of temperature rise, greater than the limit value, the components in the electrical cabinet will be damaged, the insulation will be damaged, and the human body may be in contact with the surface of the electrical cabinet, so the temperature rise is an important technical indicator of the electrical cabinet .
Analysis of short circuit problem of electric cabinet
When a short circuit occurs, the switchgear will produce an arc when it breaks the short circuit current, and the ablation of the arc will cause damage to the electric cabinet. And the switchgear inside the bus system. Due to the short-circuit current flow will produce a huge electric power, its value can reach several tons to more than ten tons of force. Such a huge electric force will have a strong impact on the structure of the electric cabinet, and even disintegrate in serious cases.
The control mode of the components in the electrical cabinet is often related to the system. For example, the power supply and distribution of the back mode, the control mode of the motor, and the start and stop control of the self-provided generator, as well as the collection and control of distributed electrical parameters, that is, DCS and so on. The control of many electrical cabinets uses PLC to perform control.
Many times, PLC can perform control tasks, but also can perform data management, data exchange and man-machine dialogue control operations, and supporting man-machine interface, power monitoring system and DCS system, these data can also be sent to the intelligent building management system and fire management system and so on.
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