Soft starters for Supply Ships
Driving retractable thrusters
Motor ratings: 6600V, 4500KW
The Blue Marlin, refurbished by HHI (Hyundai Heavy Industries), was designed to carry heavy loads such as drilling rigs and other static floating objects.
The ship is equipped with 3 generators, rated at 3655KW, 6600V, 400A and 2 retractable thrusters rated at 4500KW, 6600V, 486A.
The large power rating of the thrusters and the relationship between the 3 generators and the motor power required that special attention be paid to starting-current and voltage-drop issues.
Some of the critical requirements were:
- Limiting the starting current and consequently the voltage drop to acceptable levels.
- Enabling thruster starting when two of the three generators are running.
After comparing the various starting methods available such as auto-transformer starter, electronic soft starter and variable frequency drive, it was concluded that a medium voltage soft starter would offer the optimum solution both technically and economically.
Two HRVS-DN soft-starters were installed. Starting current is 360% of In and starting time is 12 Sec. Voltage drop when starting the thruster with only two generators running is less than 5%.
