Terminal blocks are a type of connector assembly used in industrial applications to connect parts of electronic circuits. They include conductive components with wire retention sockets, all enclosed in a one-piece plastic housing. Some terminal blocks have contact pads or feet for connecting to the PCB, but most are designed with their own housing for screwing onto machine frames, attaching to the sides of industrial electrical components, snapping into industrial rails and rack systems or mounting to the inner wall of the control panel enclosure.
Electrical terminals blocks can be used as electrical connection terminals in a wide variety of applications. Other more specialized terminal blocks include:
1. Used to transmit I/O signals
2. Terminal block used as ground block. Specifically designed for grounding
3. Junction box used as fuse box. Two of the wires are connected to a fuse to protect the circuit
Unlike other connector options, a single terminal block typically only establishes a single wire connection to the electronic circuit at hand. That said, the terminal blocks do come in multiple rows for connecting the array of wires to the circuit as needed.
When choosing a terminal block, the current rating is critical. Excessive current flow through the junction box can cause overheating and failure. Voltage is usually not an issue, but is still a critical terminal block parameter. Excessive voltage can cause dielectric breakdown and current leakage between adjacent terminals. Published creepage and clearance values for terminal blocks also affect voltage ratings.
The socket on the terminal block must be large enough to accommodate the designed cable gauge. The wire type partly determines the type of terminal that works best, single-strand wire is usually stiff enough to push away the spring mechanism inside the push-on connector, while multi-strand wire is usually used with screw terminals on terminal blocks.