What are the common types of distribution terminals?
Common distribution terminals can be divided into many types according to their structures, connection modes and application scenarios. The following are detailed classifications and features:
I. Classification by connection mode
1. Screw terminal
Structural principle: the wires are fixed by screw tightening pressure, which can be divided into single-hole compression and double-hole compression (clip-type).
Features:
Advantages: firm connection, wide application range (both hard wire and flexible wire are acceptable, and cold-pressed terminals are required), and the cost is low.
Disadvantages: Tool operation is required, and improper screw torque can easily lead to wire damage or poor contact.
Application scenario: low-voltage distribution cabinet, lighting circuit, main loop or control loop of power equipment.
Typical models: UK series (guide rail installation) and TB series (plate installation).
2. Spring terminal
Structural principle: the conductor is clamped by spring tension, and the conductor can be inserted and fixed without screw tools.
Features:
Advantages: quick connection, good shock resistance (stable spring pressure), suitable for frequent maintenance scenes.
Disadvantages: the accuracy of conductor cross-sectional area is high, and the cost of high current scene is high.
Application scenario: Control line connection of automation equipment, control system and small distribution box.
Typical models: WAGO 221 series (universal type), Phoenix spring terminal.
3. Crimping terminal
Structural principle: the wires and terminals are pressed into a whole by a special crimping tool (the wires need to be stripped first).
Features:
Advantages: low contact resistance, high mechanical strength, excellent anti-vibration and high current performance.
Disadvantages: Special tools are needed, which is not suitable for temporary wiring on site.
Application scenarios: high-voltage distribution cabinets, power transformers and high-current main circuits (such as bus connection).
Typical models: OT/UT series cold-pressed terminals (copper nose) and peep-mouth crimping terminals.
4. Plug-in terminal
Structural principle: it is divided into male and female terminals, which can be quickly plugged and unplugged with sockets through plugs.
Features:
Advantages: convenient installation, support for live plugging (some models) and convenient modular maintenance.
Disadvantages: Contact parts are easy to wear, so contact reliability should be checked after long-term use.
Application scenarios: connection between modules in control cabinet, temporary power interface, photovoltaic inverter, etc.
Typical models: Phoenix pluggable terminals (such as ST series) and universal pluggable terminals.
Second, according to the structural form of classification
1. Single layer terminal
Structure: each terminal has an independent wiring hole, which can be used in a single circuit.
Features: simple structure, good heat dissipation, but occupying a large space.
Application scenario: simple circuit or large current loop (such as motor start-stop control).
2. Double-layer terminal
Structure: The upper and lower layers of independent wiring holes can connect two wires (such as phase wire and zero wire).
Features: saving space, suitable for circuits with two parallel conductors (such as lighting circuits), but attention should be paid to the insulation between the two layers.
Application scenario: compact power distribution cabinet, lighting distribution box.
3. Combined terminal
Structure: Multiple single-layer terminals are assembled in rows through guide rails, which can be flexibly spliced.
Features: modular design, support for different current specifications mixed, easy to expand and maintain.
Application scenarios: industrial control cabinet, PLC control system, complex distribution circuit.
Typical model: Veidemyuller Z series combined terminal.
4. Terminal with protective cover
Structure: Insulating protective cover is installed outside the terminal to prevent electric shock or foreign body invasion.
Features: High protection level (such as IP20 and IP44), suitable for outdoor, dusty or humid environment.
Application scenarios: outdoor distribution cabinets, machine tools and equipment, mines and other harsh environments.
Third, according to the purpose and scene classification
1. Main circuit terminal (high current)
Features: High rated current (usually ≥100A), made of copper alloy, with heat sink or thickened conductive sheet.
Application: incoming terminal of power distribution cabinet, outgoing terminal of transformer and main circuit of motor.
Typical model: NT series high current terminal (rated current can reach 1000A).
2. Control circuit terminal (low current)
Features: Low rated current (generally ≤32A), compact size, supporting multi-loop dense installation.
Application: relay control circuit, instrument signal line, PLC input and output interface.
Typical models: UK1.5N (rated current 24A) and TB-2506 (rated current 25A).
3. Grounding terminal (PE terminal)
Features: special yellow-green logo, large conductive cross-sectional area, usually directly connected to the cabinet.
Application: grounding of distribution cabinet shell and grounding circuit of equipment protection.
Typical model: PE grounding terminal block (with jumper to ensure reliable grounding).
4. Special terminal for special scene
Explosion-proof terminal: used in flammable and explosive environment (such as chemical plant), with explosion-proof certification (such as Ex certification).
High-temperature-resistant terminal: made of silicone rubber or ceramic, with temperature resistance ≥200℃, used for high-temperature equipment (such as boiler control cabinet).
Waterproof terminal: with sealing rubber ring, protection grade IP67, suitable for outdoor or humid environment (such as street lamp distribution box).
Four, according to the material and coating classification
1. Electrical conductor material
Copper alloy (brass/copper): Good conductivity, moderate cost, common in ordinary terminals.
Stainless steel: strong corrosion resistance, used in wet or corrosive environment (such as seaside power distribution cabinet).
Aluminum alloy: light weight, low cost, but poor conductivity, only used in small current non-critical circuits.
2. Surface coating
Tin plating: anti-oxidation, low cost, common in ordinary terminals.
Silver plating: excellent conductivity and low contact resistance, used for high-frequency circuits or high-current precision equipment.
Nickel plating: strong corrosion resistance, used outdoors or in high humidity environment.
V. Comparison of common terminal models and parameters
Type Typical Model Rated Current Adapted Conductor Cross-sectional Area Connection Mode Protection Level Application Scenario
Screw-type terminal UK6N 32A 1.5~6mm² screws press IP20 control circuit.
Spring terminal wago221-41224a 0.08 ~ 4 mm spring clamping IP20 automation equipment
Crimping terminal OT10-8 100A 10mm² Crimping-main circuit of motor
Plug-in terminal PHOENIX ST4-S24A 0.5 ~ 4 mm Plug-in IP20 module quick connection
Grounding terminal PE-60/860a6 ~ 16mm screw presses IP20 to protect the grounding circuit.
Selection suggestion
High-current main circuit: Priority is given to crimping or screw-type terminals (such as OT copper nose and UK series) to ensure conductive reliability.
Frequent maintenance scenario: choose spring-type or plug-in terminals to improve efficiency (such as WAGO and Phoenix).
Harsh environment: Use terminals with protective cover, waterproof or explosion-proof (such as IP44 protection and Ex certification terminals).
Control circuit: Compact combined terminals (such as Veidemyuller Z series) are adopted to save space and facilitate identification.
Considering the electrical performance, mechanical strength and environmental adaptability comprehensively according to the actual demand, the safe and stable operation of the terminal can be ensured.
