The simulation and control of naval vessel shaft frequency electromagnetic signature

Shaft frequency electromagnetic signature on submarines that can be easily detected in seawater is produced due to periodic resistance variation of shaft to hull and voltage between shaft and hull. The shaft frequency signal must be controlled in order to make naval vessel safe. The practical results show that passive shaft grounding can´t effectively control the signal, especially for high rotation propellers. A mechanical installation was designed and manufactured to simulate axis´s word and a small type of electronic controller was used to control the signals to less than 0.1mV in different shaft speed in laboratory. Based on the data obtained from the simulation equipment, a kind of submarine controller up to 24V/100A was designed, installed and tested with shaft simulation installation. The results demonstrated that the controller can compensate resistance variation of shaft to hull and maintain voltage between shaft and hull less than 1mV. In other word, the grounding resistance via the controller is less than 1.3×10^-5 Ω. At same tine, a modeling circuit that simulates to cathodic protection routine combined with equipment above was verified the coordination between the controller and rectifier-transform. The results show that the controller can effectively inhibit shaft frequency signal while working together with cathodic protection system.