Patent GB-972069-A (GB)
Title: Improvements in and relating to power plants for ships
Inventor: GRAYHAM LINDSAY WILLIAM WALLAC
IPC: H02P9/06
Filed: 1960-03-10
Abstract: 972,069. Supply systems depending on two or more machines. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. March 10, 1961 [March 10, 1960], No. 8508/60. Heading H2H. At least a portion of a ship's auxiliary electric circuit may be energized by either a generator driven from an auxiliary prime mover or alternatively by one driven from the ship's propulsive power plant. A portion of the ship's auxiliary electric load AM1 comprises electric motors or other devices suitable for operation at differing supply frequencies. Switch means SW1 may be closed during a starting period of the ship's propulsive power plant PM during which the ship's propeller is below some predetermined speed, and thus connects the auxiliary load AM1 through a bus-bar BAX to a constant frequency generator CFG driven from an auxiliary prime mover APM such as a turbine or a diesel engine, and which supplies a permanent auxiliary load AM2 requiring a constant supply frequency. When the predetermined propeller speed is attained the frequency of a variable generator VFG driven from the propulsive prime mover PM through a mechanized transmission MC either directly or through a gear-box, corresponds approximately to the frequency of the generator CFG so that the switch means SW1 may be opened and a switch means SW2 closed thus transferring the load AM1 on to the generator VFG. A corresponding change over of the load from generator VFG to generator CFG may be carried out when the propeller speed is reduced through the predetermined speed. The change over of the load AM1 may be effected manually or automatically in response to the frequency or speed derived for instance from a propulsive electric motor PrM energized by a propulsive generator PrG and driven from the prime mover PM. Synchronizing the generator VFG with the generator CFG before the load AM1 is transferred is not essential as a transition period may be introduced between its disconnection from generator CFG and connection to generator VFG in order to allow for the delay of the magnetic fields of any motors which may comprise the load. If the said motors are rotating already, their initial current from the generator VFG will be less than their starting current, whilst if the motors are large, means may be provided to prevent their connection when the generator frequency exceeds a predetermined value. A voltage relay may be included to prevent closing the switching means SW2 when the said motor's residual voltage exceeds that of the generator VFG by a predetermined amount. The load AM1 may be connected as described above to the output of the propulsive generator PrG instead of to a separate variable frequency generator VFG. One or more generators VFG may be used and these may be built into or comprise separate windings of the propulsive generator PrG or Motor PrM. Transformers may be used where differing voltage requirements are to be met. The whole of the ship's auxiliary load may be supplied by the generator VFG if the propeller speed corresponds to the frequency requirements of the load AM2. In an emergency the propulsive motor PrM may be energized from the generator VFG.