When the bow thruster motor is operated together with the exclusive generator on the 1:1 basis, the voltage may be fluctuated due to the pulsation of the load under the heavy sea conditions, etc., and the safety may be insufficient. To cope with this problem, the automatic voltage regulator was developed, which is not adversely affected by the sea conditions by adding the stabilization control of the field current of the generator.
[Yoshinobu SANPEI]
13. Electric Equipment and System
There is scarcely any remarkable developments or new products on the technology of the ship electrical installations in 1998, since the new type of ship has not appeared although many ordinary type ships have been built.
It is noted as a general tendency that the revision works of the rules and standards become lively in the ship related fields for the preparation against the 21th century. The computer Year 2000 problem and the podded electric propulsion system whose installations are on the increase in Europe are also noted as topics in 1998.
13.1 Podded electric propulsion system
An interest in the podded electric propulsion system known as “Azipod” of ABB which integrated the drive motor, propeller, shaft and rudder, is increased in Europe. Almost applications of this type propulsion system are up to now ABB/Kvaerner make, nevertheless five manufacturers have already entered this market.
Installations of the podded electric propulsion system at present 1998 have been limited for the passenger ships and the special purpose ships such as survey vessels because the cost are rather expensive. But there are totally such merits as efficient use of machinery space and reduction of the shipyard's works, since the propulsion device are equipped at outside hull and flexibility of arrangement of machinery space increases. Therefore there is a strong possibility in the future that installations of this type system spread for the all other type ships.
The society (MESJ) has implemented an investigation study in 1997 about the electric propulsion system. It is reported that the electric propulsion ships will contribute to the safety of navigation and the environmental protection. As the podded electric propulsion system will contribute further to the innovation of the shipbuilding technology, It is a following up item from now on.
13.2 Revision of JIS marine cables
The electric cables for ships of the JIS (Japan Industrial Standards) which are based on the standard IEC600092-3 have been used for a long time to the ship electrical installations. As the IEC standards have been recently revised and established as new standards of IEC60092-300 series. Accordingly the JIS for the marine cables have been changed completely in accordance with the standards IEC60092-300 series. The main revised items are as follows;
(1) Two standards for the fire protection are established in accordance with the standard IEC60332-1 on the fire resistant and IEC60332-3 Category A on the frame retardant.
(2) The nominal section 1.25mm2 of conductor size which was the original size of the JIS cables has been abolished and the minimum conductor size becomes 1.5mm2. This unification of conductor size has settled the difference from the classification societies' rules.
The practical ship application of the new JIS cables will be about 1 year later.
Fig. 13.2 Installation of Azipod
Fig. 13.3 Typical one-line diagram for two Azipod installations
