300Amp Impedance Bond

300Amp


300Amp Impedance Bond

High quality Ansaldo STS Impedance bonds are designed for electrified territories that use insulated joints to isolate track circuit signaling current from signaling currents of adjacent track circuits, but still permit propulsion current to flow around the joints to or from adjacent track circuits. Bond styles include "Mini" (300 amp/rail AC) and "PT" (1000 to 2500 amp/rail DC).

Typically, impedance bonds are installed in pairs at insulated joint locations. Bond center taps are electrically interconnected with a heavy conductive cable. The remaining two terminals of one bond are connected to the rails with heavy conductive cable (one per rail) on one side of the insulated joints. The remaining two terminals of the other bond are likewise connected on the other side of the insulated joints.

Propulsion currents are divided equally between the two rails and pass through the impedance bond winding such that the propulsion current of the winding halves cancel each other magnetically. As a result, the bond offers very little impedance to the propulsion current flow. AC signaling current flows into the bond from one rail and exits the bond into the other rail. There is no magnetic cancellation and the bond develops an inductive impedance which restricts signaling current flow. This current cannot enter the adjacent track circuits at the center taps connection because there is no suitable return path for the current flow.