When the ship arrives in port, the ship’s winches keep it secure to the dock so the passengers can safely board and depart the ship. The ship’s six winches, in operation since 1985, use a three-speed control system with three-winding, direct-on-line (DOL) motors and an external mooring controller and load sensor in the gearbox.
Using this system to moor the ship, winch operators watch the rope until it is taught, adjusting the speed of the winch accordingly. Each speed change made to the winch (low, middle, or high speed) results in a direct-on-line start of one of the motor’s windings. DOL starting combined with the high torque demands of the mooring operation place substantial stress on the winch system, and as a result, rotors on the winch motors would break periodically. In addition, the age of the winches makes finding spare parts more difficult, typically some spare parts could have long delivery times, especially for the motor parts.