Phoenix ST series spring cage terminal block

Phoenix Contact ST Series Spring Cage Terminal Blocks: Comprehensive Analysis and Application Guide

In the fields of modern industrial automation and electrical engineering, the quality of wiring inside control cabinets directly affects the stability, safety, and maintenance efficiency of the entire system. As a leader in connectivity technology, Phoenix Contact has launched the ST series Spring cage terminal block in the CLIPLINE complete system, which has become one of the preferred solutions for engineers worldwide due to its excellent seismic performance, fast wiring experience, and long-term stable connection reliability. This article will provide a comprehensive and in-depth technical analysis of the ST series terminals, from core technology, product line architecture to specific application selection, presenting you with a detailed technical guide.

Core Technology: Advantages of Spring Cage Connection

The core of the ST series lies in its innovative spring cage connection technology. Unlike traditional screw crimping methods, it uses high endurance stainless steel springs as clamping elements. When operated with a standard screwdriver, the terminal point is opened and the wire can be easily inserted into the clamping space; After removing the screwdriver, the spring automatically resets and provides a constant, high-strength contact force.

This design brings several decisive advantages:

Seismic and airtight connection: High contact force ensures that the connection point will not loosen even in strong vibration environments such as rail transit and shipbuilding. At the same time, the pressure is sufficient to penetrate the oxide layer on the surface of the wire, form an airtight connection, prevent electrochemical corrosion, and ensure long-term stability.

Unprocessed wiring: All types of copper wires, up to a maximum of 35mm ², can be directly inserted and connected without any pre-treatment (such as tinning), greatly reducing installation time.

Large tolerance wiring space: Thanks to the optimized clamping space design, convenient and reliable wiring can be achieved for wires with nominal cross-sections, whether or not cold pressed terminals are used.

Front end operation convenience: All operations are carried out on the front of the terminal, and with the help of a standard screwdriver, wiring can be easily completed even in a compact control cabinet, while maintaining a clear view.

Overview of Product Line (Classified by Section)

The ST series provides an extremely rich product matrix to adapt to various application scenarios from signal transmission to power distribution. According to the cross-section of the wire, it is mainly divided into the following levels, each level containing multiple functional terminals.

1. 1.5 mm ² series: precision signal transmission

This series is mainly used for connecting weak electrical signals inside control cabinets. Its product types include:

Straight through, multi wire, and multi-layer terminals: such as ST 1.5/S-QUATTRO (four layer bridging terminal), used to achieve multi-point potential distribution in a limited space.

Double layer terminals: such as MZFKK 1.5, can be wired separately on two layers, effectively saving installation rail space, and both layers can be bridged.

Special function terminals: including STTB 1.5 BUS for fieldbus, STTB 1.5-PV for photovoltaic applications, and models with LED indicators for quick diagnosis of signal status.

Grounding terminal: STTB 1.5-PE with yellow green casing, used for safety protection grounding.

2. 2.5 mm ² Series: Universal Control Core

This is the most widely used series and the main force for I/O connections inside PLC cabinets.

Basic straight through terminals, such as ST 2.5, are the basic units for constructing potential strips.

Multi connection point terminals: ST 2.5-TWIN (three connection points) and ST 2.5-QUATTRO (four connection points), used for star wiring or sharing the same potential.

Sensor/actuator terminals: such as the STIO 2.5 series, designed specifically for connecting on-site sensors and actuators, with some models integrating PE pins or LED status display.

Knife switches and breaking terminals: such as ST 2.5-MT and ZDMTK 2.5, can achieve circuit breaking and testing without disconnecting wires, greatly facilitating debugging and maintenance.

Fuse type terminal: provides overcurrent protection for the circuit.

Hybrid Terminal (STS Series): One side is spring connected, and the other side is screw connected, providing a perfect solution for the transition of different connection technologies.

Micro terminals (MSB series): such as MSBV 2.5, with extremely low height, especially suitable for flat control cabinets with limited depth or 15mm DIN rails.

3. 4 mm ² Series: Balancing Power and Protection

This series achieves a good balance between load-bearing capacity and space occupation.

Fuses and lever type breaking terminals: consistent in appearance, easy to layout uniformly. We offer a variety of fuse specifications ranging from 5x20mm to 6.3x32mm.

Double layer breaking terminal: such as STTBS 4, which integrates breaking function in two layers of one terminal, suitable for compact power distribution and measurement circuits.