What Is a Disconnect Terminal Block?
A disconnect terminal block is a terminal block that, in addition to the function of electrically connecting cables to which terminals are crimped, as with a normal terminal block, has a disconnect function. Therefore, it can be easily disconnected electrically by simply pulling on the mechanism by hand, without removing the terminals.
Since there is no need to loosen screws when disconnecting, there is no need to touch the charging section even when power is being supplied, eliminating the risk of electric shock. The terminals are connected to the terminal block with screws.
Uses of Disconnect Terminal Blocks
Disconnect terminal blocks are mainly used in control panels and relay panels. Most of them are used in the low voltage range of 24 V to 220 V.
They are used specifically because they are built into the power supply to sensors and instrumentation, and can be easily turned off by disconnection terminal operation when a sensor is out of service due to a failure of the relevant sensor, etc.
Also, when repairing a sensor, simply disconnecting the disconnecting terminal is all that is required, so there is no need to open the upper MCB and the sensor can be repaired individually.
Principle of Disconnect Terminal Blocks
In a basic terminal block, a cable with terminals crimped to each of the terminal blocks facing each other is attached with screws, allowing current to flow through conductors such as copper inside and electrically connecting the two cables.
The disconnect terminal block also has a conductor attached to the disconnect mechanism, and when energized, the two cables are connected through the conductor of the disconnect section. When disconnecting the power, the disconnecting section is pulled, and the intermediate conductor connecting each terminal section is removed, thus disconnecting the power line (basically, the disconnection operation is performed when there is no voltage).
This method is not suitable for use in areas where voltage is high, as arcing may occur when disconnecting from the energized state, resulting in electric shock or burn damage.
Terminal blocks are also equipped with insulators called separators to prevent short circuits by insulating adjacent terminals so that current does not flow between them. Separators can also burn out and cause dielectric breakdown if used in high-voltage circuits.