A Practical Guide to Terminal Blocks & Connectors
Terminal blocks and connectors are essential components for connectivity. They are often the last electrical interface in the system, playing a crucial role in connecting electronic devices to the mains, as well as to associated sensors and other system parts for the overall system to operate correctly.
Terminal blocks come in different design types and ratings, including fixed or pluggable varieties, with screw, spring-clamp and screw-less variants offered. They are used for diverse applications and can be found on many PCBs, providing connectivity for many products.
The most popular format is the familiar screw-terminal. Another common format is the spring-clamp terminal, which uses a spring-loaded mechanism to clamp the wire in place, eliminating the need for screws. Screw-less terminals have a push-fit mechanism to secure the wires. These variants are designed for rapid, quick and easy installation and are also ideal for applications that require frequent wire changes.
When selecting a terminal block, it's important to consider several important factors:
Product Quality
Terminal blocks are designed to provide secure and stable connections, allowing an efficient, low resistance connection. They are often used for industrial or other equipment engineered for long life operation in the field, including equipment located in humid or otherwise harsh environments. The materials used are critical; with a common problem being oxidization leading to higher contact resistance. At high-voltage mains voltages this can cause heat dissipation, arcing and an associated fire hazard. Even at low voltages, oxidation is a problem; causing increased resistance and reliability problems. Selecting good quality terminal blocks is essential to long-term hazard-free reliable operation.
Voltage and current ratings
The voltage and current ratings of a selected terminal block must exceed the specifications of your use case in order to ensure safe and reliable operation. Voltage surges should be taken into consideration when selecting the isolation voltage and current rating to prevent damage to the connections. We normally advise to select a terminal with an isolation voltage and current rating of at least 150% of the system’s expected maximum. Current ratings for Summit Terminal blocks can vary from 4A up to 76A.
Pitch & Pole Count
The pitch of a terminal block refers to the distance between the center of one terminal or pin to the center of the next terminal or pin. This measurement is usually specified in millimeters or inches, and it is an important factor to consider as this affects the isolation characteristics and corresponding spacing of the wires. The Summit terminal block connectors feature pole counts up to 24, and are available in horizontal, vertical, 45°, and 180° orientations. These models offer 2.54, 3.5, 3.81, 5.0, 5.08, 7.5 and 7.62 pitches.
Wire size
Terminal blocks come in different wire size ranges, and needless to say that it's important to select a model with appropriate current carrying capacity for the target application. When field installation is necessary, it is sometimes advisable to provide larger size ranges to be able to manage larger connection cables. Summit terminal blocks are available for wire sizes from 0.081mm2 to 21.15mm2 (28 – 4 AWG).
Insulation
Terminal blocks with appropriate insulation breakdown voltages are mandatory for mains or high-voltage applications requiring protection from electrical shock or where there is a risk of contact with live parts.
Environment
The absolute worst-case operating environment conditions for a terminal block should be carefully considered. For example, terminal blocks for outdoor use must be oxidation and weather-resistant, while those for use in harsh environments must be durable and able to withstand extreme low or high temperatures, vibration, humidity, moisture and dust over extended periods whilst retaining reliable low-resistance arc-free operation.
Space restrictions
Terminal blocks come in different shapes and sizes, and it's important to consider the space restrictions of your application when doing your selection. Rectangular terminal blocks are ideal for high-density wiring.
Type of connection
The different varieties of terminals available include screw, spring-clamp and screw-less variants. There are also fixed and pluggable versions. Select the type of terminal block that is most suitable for your application based on the wiring density, ease of installation and wire changes.
Other connector forms
Summit also provides other forms of connectors in a variety of shapes and sizes, from simple plugs and sockets to more complex circular and rectangular connectors.
Circular connectors are useful for industrial control systems and other harsh environments. These connectors are designed to withstand harsh conditions, including temperature extremes, vibration, humidity and moisture.
Conclusions
Terminal blocks and connectors are a real Basics for All Innovation…; ensuring efficient and safe electricity flow. Selecting the right version is critical to ensure trouble-free operation. Consider the rated voltage and current, wire size, insulation, environment, type of connection and space restrictions when making your selection.
