The main question discussed here will be the effect of thyristor switching operations. The motor is assumed to be equipped with a suitable filter to eliminate electromagnetic interference occuring at the collectors. In any case, such disturbance is slight. The problem is quite different in thecase of switching of thyristors and diodes. As illustrated by the oscillograms in figure 9, the phase voltage is reduced during switching. To beginwith, the alternator voltage has to be adjusted (usually to a higher level, but close to the busbar voltage). The difference between alternator andbusbar voltage zero points is then measured, to check the voltage phase difference, and close in the circuit-breaker. The direction of variation ofthe deviation and of the voltage variation is also established. Recordings of the form of the electrical network voltage, taken on board a cable-laying ship show a very rapid voltage variation at the start and end of the switching period. Because of the steep voltage front created by switching,the zero detector appears to record a 'fictitious' zero, whereas the network voltage is not nil. The result is that connection takes place under unsatisfactory phase conditions. This problem disappears when the voltage applied to the synchronisation device is filtered. On this cable ship, propulsion is provided by two d.c. motors, supplied by a 660 v network comprising three alternators.
Electrical propulsion of merchant ships (suite), part III: electrical propulsion
Elektrischer Antrieb von Handelsschiffen (Serie), Teil III: elektrischerAntrieb
Bulletin Technique du Bureau Veritas, English Edition ; 75 , 4 ; 3-32
1993
30 Seiten, 9 Bilder, 4 Tabellen
Article (Journal)
French
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