The CBU is a single inductor housed within a transformer-style can that prevents the distribution line carrier signals from being shunted to ground when grounded-Y capacitors are on the distribution line or from being shunted line to line for a delta application. The CBU is pole a mounted and connected in series with the capacitors. Consult your system implementation plan to determine the exact CBU specified for each installation location. The CBU functions as a low impedance to the 50-60 Hz power and does not alter the operation of the capacitors. However, the CBU functions as a high impedance to the carrier signal and prevents it from being shunted to ground or line to line. Since the distribution lines are usually three-phase, requiring capacitor banks in all three phases, the CBU installation must also be effective in all three phases.