An example of the installation of electric propulsion system in 1997 is the thyristor motor propulsion system which has been delivered by Taiyo Electric Mfg. Co., Ltd. To the fishery survey ship "Shoyomaru" of Fisheries Agency.
This newly developed high technology survey ship is not only equipped with many computer systems and observation instruments for the study, but also provided with high accuracy navigation system which keeps own ship position on the routes.
Accordingly, the electric propulsion system complies with the requirements for noise and vibration so that these precision equipment shall not be affected thorough the survey area.
The diagram of electric propulsion system for "Shoyomaru" is shown in Fig. 13.1.
Fig. 13.1 The diagram of electric propulsion system for Shoyomaru
The clutch and break are provided for each main engine, propulsion motor and propeller, by which operation modes are changed over.
In the future as SOLAS's ISM code goes into effect from July 1998, the responsibilities of the ship company for the safety of navigation and the protection of environment shall be increasing in spite of the increase of mixed crew ships and the lack for skilled crew.
It is expecting that many electric propulsion ships go into service as a solution of the "gentle ship for the earth and the human crew".
13.2.2 Generator control and electric power management
Terasaki Electric Co., Ltd. and Japan Radio & Electric Mfg. Co., Ltd. put respectively the type "GAC- 16M" and the type "JACOM-2001/MPC-1" on the market, of the small size, distributed control and high performance system for the generator control and/or electric power management.
It is possible for the main switchboard to be reduced to small size by using these devices as the synchronous panels could be deleted when the number of generators connected to the system is small.
13.2.3 Circuit-breaker with higher short-circuit breaking capacity
Terasaki Electric Co., Ltd. puts the circuit-breaker type "AH-50CH" on the market, which has been developed in order to comply with increase of onboard ship electric power required by the large-sizing of container ship.
The new circuit-breaker has a higher short-circuit breaking capacity of 135 kA for low voltage system (rated voltage = 500 V AC).
As the short-circuit breaking capacity of the ordinary circuit-breaker is about 120 kA, the increase of breaking capacity shall be capable of wide application for low voltage system.
13.3 Regulation
Ships constructed on or after 1 July 1998 need comply with the following amendments to SOLAS, and rules for classification shall be accordingly amended.
* Disconnecting of main bus bar
In the old paragraph, "Where the total installed electrical power of the main generating sets is in excess of 3 MW, the main bus bar shall be subdivided into at least two parts which shall normally be connected by removable links or other approved means". The new paragraph reads, "Where the main source of electrical power is necessary for propulsion of the ship, the main bus bar shall be subdivided into at least two parts which shall normally be connected by circuit breakers or other approved means".
It is necessary to confirm each classification for the selection of the devices as there are differences in the interpretation of the "other approved means".
* Restoring propulsion from a dead ship condition within 30 min.
