Global : English
Home » News » Blogs »
Connectwell Screw Clamp Terminal Blocks
January 2022

When it comes to connection technology, Screw Clamp Terminal Blocks are the most widely used component in the electrical industry. This level of popularity is due to the fact that over decades, Screw Clamp connections still proves to be the most reliable with billions ofconnections made and in operation.

A closer look at Screw Clamp technology

A wire is inserted inside the Terminal Block in the space between the clamping yoke and the Current Bar. The screw is then tightened with the help of a screwdriver. When the screw is being tightened, the clamping yoke moves upwards exerting force on the wire which then gets compressed firmly between the clamping yoke and the current bar. The clamping yokes have a unique design feature wherein upon tightening of the screw, a counteracting force is generated on the engagement area of the screw threads and this acts as a self-lockingfeature enabling vibration-proof connections. Connectwell Screw Clamp Terminal Blockscomprise of screws and clamping yokes made of high-grade Mild Steel material. Moreover, these screws and clamping yokes also go through heat treatment and electro-platingprocesses which enhances the strength of the material and also enables corrosionresistance. Furthermore, the current bars of these Terminal Blocks are made of high-grade copper and copper alloys which provide extremely high conductivity. A pre-determined torque value for tightening the screw is specified by the manufacturer which helps the user to apply the exact force in order to hold a wire firmly inside the Terminal Block..

Typical wire installation can be in any one of the following ways:

- Stripped wire is directly inserted into the clamping unit

- Wire is first fitted into a ferrule, which is then inserted into the terminal

- Wire is attached to a connecting lug, which is then inserted into the terminal.

Screw Clamp Terminal Blocks can accommodate Copper and Aluminium wires in solid, stranded or flexible wire forms. Multiple wires can also be inserted into one clamping unit, provided the wire size specified by the manufacturer can be accommodated stranded or flexible wire forms. Multiple wires can also be inserted into one clamping unit, provided the wire size specified by the manufacturer can be accommodated.

There are different kinds of Screw Clamp Terminal Blocks:

The standard Screw Clamp Terminal Block can be further categorized into different ranges depending on the functionality they offer.


Feed Through Terminal Block: One of the most versatile terminals for Control, Automation, Instrumentation, and Power Distribution applications. A specially designed flexible foot enables easy mounting and detaching from the DIN rail with the help of a screwdriver. These Terminal Blocks have marker holding recesses to accept marking tags for circuit identification. Cross-connection can be achieved with the aid of screw-type jumpers.



Multi Connection Terminal Block: These Terminal Blocks are used to eliminate reliability problems encountered when there is a need to connect multiple wires in a single Terminal Block. They are an ideal solution for future-proofing circuits by virtue of extra connection points available in the terminal block.




Multi Level Terminal Block: Double & Triple level Terminal Blocks are ideal for use in applications requiring high-density wiring. Triple-level Terminal Blocks are an ideal choice for control systems where sensor and actuator applications are involved. The simplified 3-level connections can tremendously increase wiring density in the circuit.




Ground Terminal Blocks are used for terminating Grounding / Earthing wires. They are green-yellow colour coded as per industry standards. These terminals have same shape and thickness identical to the respective feedthrough terminal of the same wire size. 



Fuse Terminal Blocks provide protection to electrical circuits against short circuits and ensure fail-safe system operations. These fuse terminal blocks can accommodate ø5x20 mm glass cartridge fuses inside the integral fuse carrier which is hinged and captive in the Terminal block.

Specially designed fuse carriers with "Blown Fuse" indication feature help in quickly identifying faults.

Multiple level Fuse & Feed Through terminals facilitate two wire sensor and actuator connections in a single terminal block for DCS applications thereby increasing the wiring density and reducing the control cabinet foot print.



Disconnect Terminal Blocks allow quick, convenient and safeseparation/isolation and disconnection of electrical circuits in electrical control systems for testing purposes.

Specially designed knife contacts can be manually opened or operated using a standard screwdriver. Sliding link Disconnect & Test Terminal Blocks are available for connecting Current and Voltage transformer circuits in switchgear protection panels. The disconnection of circuit is achieved with help of opening the central sliding link with a screwdriver.

Multiple Level disconnect terminals facilitate two wire sensor and actuator connections in a single terminal block for DCS applications thereby increasing the wiring density and reducing the control cabinet foot print. Our intrinsically safe disconnecting terminals are perfect choice for hazardous location applications in Oil and Gas and Continuous Process industries.



High Voltage Terminal Blocks have been specially designed for extremely high voltage (1500 V DC) applications. By virtue of its design additional creepage and clearance distances are incorporated in the terminal to fulfil regulatory requirements. They are particularly suited for applications in the solar industry.  




Spring Loaded Terminal Block: These Terminal Blocks are preferred for connections that involve safety requirements of the Electric Supply Industry (ESI) standards, British CEGB regulations, SEC and NTPC applications. In addition to the high torque screws, these blocks have a built-in spring loading feature. It is recommended to use hook type lug/ferrule for terminating wires in such connections. These Terminal Blocks have a specially designed current bar for the right location & placement of wires crimped with hook type lug/ferrule, thus preventing loosening of the wires even when the screw clamps are not tightened.  



Modular Distribution Blocks are an ideal choice for creating a simplified distribution system.

In CDB series a bolt in the center of the block provides a connection point for the incoming cable. All the adjoining terminals are internally connected with a single current bar and provide multiple connection points for the outgoing wires. A protective shield effectively shrouds the incoming connection.

CMDB blocks are a modified version of the CDB Terminal Blocks without the central incoming terminal connection. which offers same wire size connection at input and output.




Micro Terminal Block: These Terminal Blocks are extremely compact and are used in applications with space constraints. These blocks should be used with DIN 15 type (DIN 2) rails.




Panel Mount Terminal Block: Panel mount Terminal Blocks are an excellent solution for extremely compact wiring applications. These Terminal Blocks are "modular" and can be stacked to form multipole assemblies. The stacked assemblies can be mounted on the panel surface using an End Plate. These Terminal Blocks are perfect solution for industries like Control Transformer, Elevators, Junction Boxes and applications with limited wiring space.




Thermocouple Terminal Blocks are used with thermocouple wires in measurement applications. As per DIN 43713 & DIN 43714  the current carrying element of the Terminal Block is made of the same material as the Thermocouple wire. These special current carrying elements ensure that there is no loss of potential at the connecting points. 





Tab Connection Terminal Block: These Terminal Blocks offer quick connection with the use of "Fast On type" lugs. The connection is achieved by pushing the lug on to the tab blade of the Terminal Blocks.




Component carrier Terminals facilitate the installation ofelectronic components in specially designed plugs. These plugs can be then mounted on the base terminal. The plugs can be replaced easily in case of failures during operations without disconnecting the wires from the base terminals.




Terminal Blocks with Electronic component: Certain sensitive circuits in industrial control panels need extra protection. Electronic Component Terminal Blocks areintegrated with various electronics components such as diodes, resistors and LED's. They help in protection and in circuit indication applications.

Range of accessories for Terminal Blocks

Apart from the above-mentioned types of Terminal Blocks, there is a range of accessories that can be used with the respective Terminal Blocks in order to form a complete assembly.



End Plates: End Plates are used to cover the live parts of the last Terminal Block in an assembly. They are snapped onto the terminal and its profile ensures that the live parts of the respective terminal block is completely covered.


Partition Plates: Partition Plates are used to segregate different groups of Terminal Blocks and provide the required creepage and clearance value in an assembly. Partition Plates electrically isolate adjacent Jumpers. They also provide a separation between Terminal Blocks of different potentials. For visual separation of the different circuits, a choice of coloured End Plates and Partition Plates are also available.


Separator Plates: Separator Plates are used for electrical separation of adjacent Jumpers without the use of additional space. They can be inserted after the Terminal Blocks have been assembled on the DIN rail.



Shorting Link or Jumpers: The shorting systems bridge potentials between Terminal Blocks, reducing wiring time. Adjacent blocks of selective Terminal Blocks within an assembly can be easily interconnected, leaving terminal clamps free for wiring. The current carrying capacity of shorting system is lower than the rated current of the respective Terminal Blocks; therefore, applied current must not exceed the maximum current value of the Terminal Block.


End Clamps help to secure the entire Terminal Block assembly on the DIN Rail. End Clamps should be fixed on both sides of theTerminal Block assemblies. These End Clamps are designed tofix on DIN 32, DIN 35, and DIN 15 rails.




Markers: The Marking Tags facilitate quick identification of electrical circuits in the assembly. This in turn makes the maintenance of individual components quicker and hassle-free. The tags come with a large surface area providing better visibility. All 'K' series tags are available as strips from which an individual marker can be easily separated. The Marking Tags are available in both printed and blank versions. The printing can be horizontal or vertical in 2 or 3 digits, alphabets or symbols, or a combination of these depending on a user's requirement. 



Din Rail is a metal rail used for mounting Terminal Blocks. It can be fixed effortlessly in panel board or other equipments. Connectwell offers 3 types of steel mounting rails: DIN-32, DIN- 35 and DIN-15 that comply with European Standards. The rails are zinc plated and chromate passivated.


Where are Screw Clamp Terminal Blocks used?

Screw terminals are extensively used for power, signal and data connections in electrical control cabinets.These are mainly electrical panels and switchboards, which can be further classified as power distribution panels, DCS Panels, Automation Process Industry Panels, etc.

Moreover, these Terminal Blocks are widely used across industries such as:

- Power Generation / Transmission / Distribution
- Pharmaceuticals                    - Railways & Transport
- Aerospace                              - Machine building
- Automation                             - Solar grids
- Escalators and Elevators       - Process Industry
- Defense                                  - Marine


To know more about Connectwell Screw Clamp Terminal Blocks, click here