A pilot installation on board Viking Line’s Gabriella is providing the first practical application for an ABB synchronous reluctance motor (SynRM) used to drive a mooring winch. ABB segment sales manager for marine winches and cranes Mikael Holmberg outlines the project background and the advantages of the new technology
Viking Line offers passenger travel and cargo carrier services on routes serving Finland, Sweden and Estonia with its seven vessels, including Gabriella. The ship takes around 2,400 passengers, has a crew of approximately 170 and can load about 400 cars or 900 m of cargo units.
Gabriella was built in 1992 and some of its deck equipment is reaching the end of its lifespan. Viking Line is carrying out an upgrade programme to ensure it will always meet its operational targets. As part of the upgrade programme, Viking Line carried out a pilot retrofit installation of a SynRM motor and ACS880 variable speed drive (VSD) combination for its mooring winches.
Fast starts, fast stops
The original winches on Gabriella use a three-speed control system with three winding, direct-on-line motors, and an external mooring controller and load sensor in the gearbox. However, this can create a lag of up to a second while the motor is magnetised. Only when the stator is magnetised is the brake released so that the winch can start to rotate.
The advantage of the SynRM motor and ACS880 drive combination is that it has a much faster start and stop time. That means that when the winch operator uses the joystick to start the winch, it reacts immediately and starts rotating. This instant response has had a positive impact on crew operations, since the operator simply releases the mechanical brake and lets the speed controller take over.
Modern VSD-controlled winches offer completely stepless speed control. However, this project was carried out as a fast-track retrofit with Viking Line retaining much of its original equipment. The ACS880 has been programmed with three speed levels – low, middle and high – so that the winch can be operated by the existing control stand that previously switched between three contactors. This control now provides a digital output for each speed, with a ramping transition programmed into the drive to provide the smoothest possible changeover.
Peak current issues are eliminated
Power consumption used to be a constant problem on the winch deck. Previously, when every lever was shifted to full-ahead it resulted in a peak current demand that posed the risk of system failure. Gabriella’s chief electrician, Christian Holmberg, stated that in the past there were times when he wondered if the ship would be able to dock. Now, the new variable speed drive and SynRM motor have eliminated this serious issue.
“We now have two different new drives,” said Mr Holmberg. “The first was installed with the old motor, which was a good improvement. The second was installed with the new SynRM motor – and this is so much better. It uses less power and is really smooth when you change the speed. We had asked ABB for new drive options. They came up with something that is smaller and better. There are now fewer components and that makes fault-finding easy. The variable speed drive cabinet is almost empty so there's also less maintenance.”
The SynRM motor also requires less maintenance as it has no rotor windings and runs cooler, which means a longer lifetime for the bearings. At about 600 kg, the SynRM is about half the weight of the induction motor it replaced. With six mooring winches on board, the transition to lighter, more compact technology delivers more power in a much smaller package.
Auto mooring is critical for operations
The auto mooring system on board a passenger-vehicle ferry like Gabriella is crucial for its operations. When the ship comes into harbour it has a certain load draft and as unloading and loading take place, its level in the water changes. So constant precise adjustment to the mooring winches is vital to maintain the correct tension.
This is where ABB’s solution offers another important saving as the VSD features a built-in time control sequence for auto mooring, handling tension control without a load cell sensor in the gearbox. There is now no need for an expensive speed feedback device on the motor. Once the vessel is moored, it is simply switched to automatic operation.
The direct torque control provided by the drive ensures precise regulation of lower motor speeds with high torque levels. Handling line tension with time control means fewer components face the risk of being subjected to fault conditions, making it more reliable.
“We cleared out the cabinet before ABB came aboard and they had a round trip to install the new components,” said Mr Holmberg. “We had the system up and running before docking. Of course, some adjustments in the programme were still needed, but you could use it right away.”
The aim of the Gabriella pilot programme was to test the concept of using a SynRM motor for the crucial operation of powering a mooring winch. The project encompassed design, commissioning, training and fine-tuning. ABB followed up by providing training for the electrical personnel on board.
At first, the winch operators were not completely comfortable with the new installation and its configuration. And their feedback led to further improvements. There were initially some drive parameter adjustments that needed to be made, which is normal in this type of pilot exercise. However, the biggest issue was not a problem with the motor or the retrofit itself, but with how the operators were using the system, which was fixed with a minor reconfiguration.
Gabriella has an ongoing maintenance programme and following the successful year-long trial, the plan is for all the vessel’s motors to be upgraded.
- Equipment needed upgrading to meet operational targets.
- The original winches could create a time lag.
New technology benefits
- Much faster start and stop time.
- Easier for crew to operate.
- Winches can be operated by the existing control stand.
- Peak current demand posing risk of system failure is eliminated.
- Uses less power.
- New drive smaller and uses less components.
- Less maintenance.
- Longer lifespan for bearings.
- No need for an expensive speed feedback device on the motor for automatic mooring.
New equipment challenges
- At first, winch operators were not completely comfortable with the new installation and its configuration.
- Drive parameter adjustments were made.