Date: 04 Jun 2024
Types of terminal blocks
In the scientific literature, there is no single unified classification of terminal blocks, but several classification categories have been developed in the professional community:
By purpose:
*Terminal blocks for connecting wires
*PCB terminals
*DIN rail terminals
*Cross modules
According to the installation method:
*Screw (screw clamp is used for fastening)
*Embossed (with embossed clip)
*With wire protection (pull protection)
*Detachable (The terminal strip consists of two male-female type parts. One part is attached to the board/panel, the other part is attached to the wire)
*For surface mounting
Responsible part to the cable
*Push-on (screwless terminals, lever is used to grip the wire, adjustable without additional devices)
barrier (screw terminals designed for higher current than ordinary models)
*Terminal blocks for DIN rail (for mounting DIN rails and electromechanical rails)
*Pass-through (parallel symmetrical connection of wires on 2 sides of the terminal block)
In order:
single line
two-line
three-line
multiline
By performing:
*direct
*corner
By type of connected wire:
*terminals for solid wires
*terminals for stranded wires
*flexible wire terminals
By bracket type:
*Screw
*springy
Terminal block device
The terminal block is a mechanical clamp (cage) in a plastic housing or without it. Depending on the type of clamp, the terminal can be equipped with screws, a metal plate or a spring to fix the wire. The conductor is installed in the clamping cage fixed inside. In addition, depending on the purpose of the terminal block, several more wires are installed in it to create a network, or the terminal block is mounted on a printed circuit board or a DIN rail.
The body is usually made of plastic (polyamide PA6, PA66, UL94-V0/V2 modification is sometimes used (self-extinguishing for 10 seconds on a vertically mounted specimen, including penetration of drops of flaming particles). Additional modifications of the body are possible, for example, levers for easy installation, flanges, tires.
The clamping cage is made of stainless steel, phosphor bronze. The screws are made of galvanized or nickel-plated steel, brass.
Electromechanical characteristics
Current strength, withstand voltage and resistance
One of the main electrical characteristics of terminals. They affect conductivity and resistance to electrical impacts and surges. These parameters largely determine the scope of application of certain terminals.
Temperature mode
The withstand temperature determines whether the terminal block can be used in extreme or ordinary environments. The standard temperature range is from -40 to +105, this is enough for continuous operation of most terminals in distribution boxes, modules, devices and power supply units. For special needs, for example, for connecting high-current wires or in areas where the possibility of melting is unacceptable, terminals made of liquid crystal polymer (on a printed circuit board) are used. They can withstand up to +250 °C with a short-term surge and function normally up to +130 °C. Ceramic terminals that withstand up to +300 °C are used to connect the wires.
Maximum clamping force
It is in the range of 0.2Nm to 2.5Nm. The smaller this parameter is, the easier it is to tighten and fix the wire in the terminal block, but at the same time, the risk of the terminal block being pulled from the mounting surface or the loose wire is more tall.
Contacts step
The distance at which the holes for connecting wires are located relative to each other. It is most often in the range of 1 to 20 mm.
Also, when choosing a terminal, the following are important parameters:
Cross-section of the connected wire, mm2
Number of contacts (determines the maximum number of wires that can be connected to this terminal). There are usually 1 to 48 contacts
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