Interconnection between main and auxiliary supply on board ship - assists with correct monitoring of installation resistance under all auxiliary circuit operating conditions

摘要

The application is to a shipboard auxiliary system (2) which is connected to the primary system (1) by a static converter (10). For example a d.c. auxiliary system is fed by a controlled rectifier from a 3-phase primary supply. A connection is taken from one phase (4) of the primary through a resistor (17) to one pole of the secondary system (8). The value of resistance used is lower than the lowest permissable insulation resistance (12-16) between the supply networks and the ship's hull. When the converter is operating with large delay angle, or when at very low current the output can become discontinuous. The auxiliary circuit is then disconnected from the primary as at certain regular intervals all the converter valves are blocking. The proposed ohmic interconnection ensures that the two systems are always joined galvanically thus enabling earth fault monitoring unit to operate correctly.