Under Normal operating conditions the degaussing system is automatically controlled. However, if required, it may also be manually controlled by accepting a few restrictions. The external field changes acting on a ship can only be compensated in an optimum manner by a probe controlled degaussing system. It is therefore , we can say that such type of degaussing system consists of system components and units for :
- Generating, regulating and controlling direct currents required for the degaussing system.
- Operating and monitoring the entire degaussing system
Block Diagram of a standard probe controlled Degaussing system
The Field probes are used as reference value transmitters. They convert the picked up values of the magnetic field into electrical signals. Each of these probes is aligned with one of the three ship’s axes. In this manner, the three components of the earth’s field, based on the ship’s axes, will be picked up. The probe signals are processed in the Control Unit and control the direct currents in the coil systems (VI, AI and LI). Therefore, these currents are controlled directly proportionally to the earth’s magnetic field components, depending on the ship’s Geographic Latitude, Heading and Own Motions. On the other hand, the current for the coils VP, AP and LP will be kept constant in accordance with the set values.
Further the operation of the degaussing system affects the magnetic compass. These affects on the magnetic compass are eliminated by means of the Electrical Compass Compensation System.
The Manual Course Compensation switch permits a course dependent manual control for the AI and LI channel if the automatic system of the degaussing system partially or completely fails.. The VI channel does not require compensation as the vertical field remains constant within the same degree of latitude.
The three probes are vertically arranged with respect to each other, thus, forming a three-dimensional system of co-ordinates. The three probes are rigidly mounted in a common housing that is fixed atop a mast adjustment device.
Each of the 3 probes are identical. Each probe contains two identical and individual cores of a highly permeable metal, located inside two longitudinal grooves of a cylindrical coil form. Each core has an excitation coil (at 10 KHz) and a measuring coil, wound around it. Seven different compensating coils are wound over the coil form contacting the two cores.
During automatic operation, the value for the induced part of the ship’s magnetic field is automatically determined by the probe and fed to the magnetometer in the control cabinet. The magnetometer automatically applies the correction signal to the excitation windings of the Converter Set I which generates the desired value of current (Coil Current) of appropriate polarity, in the respective coil system (VI, AI, LI). As the polarity of the current flowing in the I coils can be required to be reversed the Converter Set I is provided with two excitation coils to facilitate the change.
For the P-Channel (VP, AP, LP) the reference voltage is firmly adjusted by a current regulator and as the Converter Set P is required to deliver current of constant polarity and strength there is only a single excitation winding in the P Generator.