SELECTING AN ELECTRIC DREDGE POWER AND CONTROL SYSTEM

The main power requirements in dredgers are those for meeting variable-speed loads such as drives for ladder hoisting winches , pumps , cutters , swing winches , and, in the case of hopper dredgers, propulsion . Electrical systems for transmitting the power from the engine to the driven machine or component have gained significant advantages over mechanical drive in recent years, and in addition the silicon controlled rectifier has become an efficient component in the system. An electrical system allows engines of higher speed to be used, and operating them at constant speed has advantages in longer engine-life and lower maintenance costs. After discussing these matters, the Authors examine the capabilities of a.c. and d.c. motors for dredger requirements, and describe and discuss their control, and in particular the two basic systems for controlling the d.c. motors: the d.c. to d.c. system and the silicon controlled rectifier system. Recommendations are made on the types of motor and control that should, from the performance and economic viewpoints, be used for the various variable-speed drives in these vessels.