Definitions
Contactor ( mechanical ): A mechanical device having only one position of rest, operated electromechanically and capable of making, carrying and breaking currents under normal circuit conditions, including overload operations.
Note: A contactor is usually intended to operate frequently.
Emergency: An unexpected occurrence or condition that could cause danger and requires immediate action.
Emergency Switching: An operation intended to remove as quickly as possible, danger that may have occurred unexpectedly. This includes emergency stopping.
Undervoltage: Any voltage less than the nominal voltage of the installation.
Figure 16 shows a simple terminal block arrangement. Individual terminals are designed to clip onto a variety of mounting rails. They are manufactured in a variety of sizes to accommodate any cable CSA. Green / Yellow earth terminals are designed to make good contact with the mounting rail on tightening of the centre screw. Other colours are available but are not essential.
The terminals must be installed the correct way round as each one is generally insulated on one side only. An end insulator must be installed to insulate the last terminal. An end clamp must be used to prevent the terminals from spreading apart. An earth terminal doubles as an end clamp. Terminals with solid links or fuse holders are also available.