Everything You Need to Know About Terminal Blocks

Terminal blocks have been used for many years to provide semi-permanent, secure wire connections in a variety of applications. They are a well-known part of every engineer's connector toolkit. Terminal blocks, also known as connection terminals, terminal connectors, or screw terminals, are devices that join two or more wires together by way of a modular shell and an insulated body. Terminal blocks make field inspection and maintenance easier because of the semi-permanent nature of their connections. While being a very straightforward component, it is nevertheless advantageous to have a foundational understanding of terminal blocks and their requirements before making a choice. To aid engineers in this process, this article will go into further depth on a number of subjects, such as typical terminal block types, important electrical and mechanical concerns, and more.

Important electrical specifications

Now that the common forms of terminal blocks have been discussed, the design step must consider a number of important electrical requirements. They consist of the following:

Current Rating:

The current rating is often the most significant characteristic to take care of in terminal block designs. This is supported by three factors: the cross-sectional area, the resulting temperature increase, and the conductivity of the terminals. It is advised that the module has a current rating of at least 150% of the system's estimated maximum current when choosing a terminal block. A terminal block that has been improperly rated and operated at an excessive current risk of overheating and other serious safety issues.

Voltage Rating:

The pitch and dielectric strength of a terminal block's enclosure have some bearing on its voltage rating. The voltage rating of a terminal block must be larger than the maximum system voltage, considering any voltage spikes that might harm the connections in a manner similar to the current rating.

Pole count:

The most typical technique to describe the number of separate circuits that are included by a terminal block is via the usage of the pole count. Typically, this standard will include a single pole or as many as 24 poles.

Pitch:

 Regarding elements like creepage, voltage/current, and clearance, the total rating of the terminal block governs pitch, which is measured as the center distance between neighboring poles. Common pitch values include things like 2.54 mm, 3.81 mm, 5.0 mm, and more.

Wire Size/Type:

 In North America, terminal blocks specify the size or gauge of wire the module can take to make sure wires will actually fit into the housing. This information is expressed in units of American wire gauge (AWG). Fortunately, most terminal blocks provide some tolerance by supporting a variety of wire diameters, such as 18- or 24-gauge wire. Depending on the chosen module type, wire type should also be considered in addition to wire gauge. The single-core wire is often used with push-in type terminal blocks, but stranded or multi-core is best for screw terminals.

Types of terminal blocks

So, having looked at some of the more popular connecting techniques, let's now take a closer look at some of the various terminal block designs.

Ground terminal block

A Ground terminal block first resembles a standard Screw-in terminal block. The Ground terminal block links the incoming cable to the Ground rather than attaching any wires. Wherever the block is installed, whether it is on a panel, DIN Rail, etc., the wire is terminated there.

Fuse terminal block

As a fuse is placed in series between the wire-in and the wire-out, fused Connecting terminal blocks do not need external overcurrent protection. Several providers have added a Fuse Failure LED circuit to provide a visual indication of the fuse condition to aid in troubleshooting.

terminal block for thermocouples

A thermocouple block may accept Thermocouple lead connections. The usual terminal blocks cannot be used to connect thermocouples. An undesired connection happens as soon as the thermocouple wire touches the conducting material within the terminal block. Combining two dissimilar metals will result in a new junction and undesirable voltage. Some thermocouple connections hold the thermocouple leads together on both sides of the block to prevent the formation of a new connection. Thermocouple blocks from certain manufacturers come with inside metal connecting strips made of the same metal as the thermocouple wire.

Multi-level terminal blocks

Space within a cabinet or an electrical panel is often at a premium. Individual terminal blocks may be linked together to create groups or clusters, and they are often organized in multi-level layouts to save space. There are a varied number of layers or levels in each setup. A Triple level terminal block, for instance, has three levels.

Consider reviewing everything one last time. When used correctly, terminal blocks are reliable and effective equipment. The wrong choice of terminal blocks might lead to undesirable complexities and poor performance. It is advised to speak with an experienced High-power terminal block supplier to assess your application's needs or for assistance in creating an appropriate terminal block specification.