The generators form the heart of the electrical design and their correct sizing is the key to a safe, workable and economical system. When sizing a marine generator cognizance must be given to the nature of the load. The generator often works on its own power and is accordingly susceptible to large system load swings, loads causing distortion, the connection of motors and the connection of large heater elements for air conditioning systems. In addition to satisfying the system load requirements, consideration must be given to the special requirements of any large loads, unusual operational requirements, spare capacity requirements and the required system operating philosophy.
International maritime regulations (e.g. SOLAS), require at least two generators for a ship's main electrical power system. The generators are normally driven from their own dedicated diesel engine but this can be expensive, taking up additional space that could be used for other purposes. For ships engaged on long sea voyages, it can be economical to drive the generators from the main propulsion plant. International maritime regulations also require at least one electrical generator to be independent of the speed and rotation of the main propellers and associated shafting and accordingly at least one generator must have its own prime mover.
If a minimum of two generators is provided, one of which is driven from the propeller shaft, failure of one of the generators could make the ship non-compliant with the International regulations. For this reason many owners opt to provide three generators. One is used for the normal sea load (e.g. the shaft generator), leaving two available to meet any unusually high loads
or to provide security when maneuvering. Alternately, the third is retained as a standby set able to provide power if one set fails in service or requires specific maintenance work.
In some applications such as a generator supplying a large SCR type load, the generator rating may be increased well beyond its full load value, in order to account for harmonic heating and the inductive requirements of the SCR devices. DCMT has developed its own software to assist in generator sizing.
Пояснювальна записка. | Find the equivalents of following word combinations. | Give adequate Russian equivalents of the italicized words. | Read and translate the following text. | Виберіть відповідну форму герундія. | Give adequate Russian equivalents of the italicized words. | Read and translate the text. | Визначте форму герундія і переведіть пропозиції на російську мову. | FIRST AID FOR ELECTRIC SHOCK. | Визначте правильне закінчення речень. |