Selection Guide For Terminal Blocks: Meeting Different Application Requirements
As the core component of electrical connections, the selection of terminal blocks requires comprehensive consideration of wire diameter, current, installation environment, and functional requirements to ensure the safe and stable operation of the electrical system. The following guide covers three aspects: key parameters, application scenarios, and selection strategies.
1、 Core parameter matching
Wire diameter and current carrying capacity
Select the appropriate terminal based on the cross-sectional area of the wire. For example, for 0.2-6mm ² wires, the Phoenix UK 5N universal terminal (current 10-32A) can be selected, while for high current scenarios (such as the DC side of photovoltaic inverters), the Weidmuller HD 10.16 terminal (spacing 10.16mm, compatible with M6-M10 screws) should be selected. Please note that there should be a margin left for the nominal current of the terminal to avoid excessive temperature rise caused by long-term overload.
Installation method and space
The installation of the guide rail needs to match a 35mm standard guide rail and reserve 20% expansion space; When fixing screws, the recommended distance between M4 screw holes is 25mm (single hole load capacity ≤ 1.5kg). For compact devices such as building automation systems, Wanke TOPJOB S 2.5 spring terminals (width 5.2mm, insertion depth ≥ 8mm) can be selected to achieve high-density wiring.
2、 Scenario based selection strategy
Industrial Control Cabinet
Priority should be given to universal terminals (such as UK/NT series) with a spacing of 5.08mm, suitable for PLC signal wiring and sensor connections. If you need to prevent accidental insertion, you can choose marked terminals with color markings or double-layer terminal blocks to improve maintenance efficiency.
Outdoor distribution box
It must meet the protection level of IP65 or above, such as the Taike AK3 series ceramic base terminal, with high temperature resistance>105 ℃, suitable for humid or high temperature environments. For motor junction boxes, fence type terminals (such as TB/JB series) are designed with anti touch fingers through a fence height of 8-15mm to enhance safety.
New energy vehicle battery pack
Use high temperature resistant and flame-retardant materials (such as UL94 V0 certification), and ensure that the terminal spacing is ≥ voltage level × 0.5mm (such as 220V circuit spacing ≥ 3.5mm) to avoid creepage short circuits. For example, the LXT series terminals of AVIC Optoelectronics have passed the vehicle specification level certification and are suitable for high-voltage DC bus scenarios.
3、 Guide to Avoiding Pits
Neglecting the bending radius of cables
The bending radius of 6mm ² cable should be ≥ 48mm. If the selection is too dense (such as using standard spacing terminals), it may cause insulation layer wear. The solution is to use side outlet terminals (such as Phoenix PTFIX 6) or increase the space for cable trays.
Mixing different brands of terminals
Similar appearance but with a dimensional tolerance of ± 0.2mm may result in poor insertion. Suggest unifying the brand or verifying compatibility (such as some models of AVIC Optoelectronics LXT and Phoenix PT being compatible).
No reserved expansion space
During the installation of the guide rail, 20% of the space should be reserved to avoid the need for re layout when adding lines in the future. For example, a factory was forced to replace the entire terminal block during later expansion due to lack of reserved space, resulting in a 30% increase in cost.
4、 Industry Trends
With the development of industrial automation and new energy fields, terminal blocks are evolving towards miniaturization and high density. For example, the Wanke TOPJOB S series uses spring clamping technology to achieve instant connection of 0.2-4mm ² wire diameter, which is 5 times faster than traditional screw terminals; The Phoenix PTFIX series adopts modular design, supports plug and play, and is suitable for intelligent manufacturing scenarios.
Conclusion: The selection of terminal blocks should follow the principles of "safety, reliability, and efficiency", match parameters with specific scenarios, and pay attention to industry technology upgrades. By standardizing the selection process, design risks can be reduced, system stability can be improved, and solid guarantees can be provided for electrical engineering.
