Short-circuit no-load monitor for AC generator stator winding - has relay preventing generator de-excitation when loaded

摘要

The short-circuit monitor, for an a.c. generator stator winding, de-excites the generator in its no-load condition when a short circuit occurs between its windings, but blocks this de-excitation process with relays when the generator is loaded. The star-coupled windings each have a monitoring coil coupled via transformers to three rectifiers. The rectifier outputs are combined and passed over the blocking relay contacts to the trigger that operates the de-excitation circuitry when a short occurs with the windings on no-load. The blocking relay contacts open when the generator is loaded (i.e. not protected against shorting) and closed when unloaded (i.e. protected against shorting).