Great advantages with a 2-speed CP-propulsion system giving optimised running conditions and considerable energy savings
The 2-speed reduction gearbox is a fully integrated solution to provide the option for two steps of different propeller speed in a hybrid or diesel mechanical configuration. The system is ideal for vessels with variations in power requirements, such as Purse Seiners, Trawlers, AHTS, Seismic vessels, Mega Yachts and Rescue vessels.
The graphs of Step1 and Step2 in the diagram show the direct effect of reducing the rpm using the 2-speed reduction gearbox.
The pelagic vessel Odd Lundberg, owned by the Norwegian fishing company Odd Lundberg, is designed with a strong focus on optimal working conditions, safety and comfort for the crew. “We are generally very proud of our vessel,” said Mats Lundberg, Odd Lundberg’s skipper. “The performance and the new technology means that we can save time and fuel when we are at sea, and this means more time at home with our families and friends."
The collaboration between the owner, the Karstensens shipyard and Brunvoll resulted in an effective and sustainable solution for propulsion and manoeuvring, based on the vessel's operating profile. The 2-speed propulsion system allows for operation in two speed modes, ensuring optimisation of propeller speed and energy consumption in different operating conditions, a system that has proven to provide significant savings.
"We have used step two of the system to a much greater extent than first expected. We experimented with the plant during trawling, and to our surprise we experienced that trawling by using step two and the 50-60 Hz floating frequency resulted in a fuel consumption decrease by 100-130 litres per hour. With 12-20 hours spent in that condition per day for much of the year, such savings are very positive," Mats Lundberg said.
The 2-speed gearbox design and construction is based on the same principles as for all Brunvoll gearboxes, and benefit from a reliable high quality philosophy.
The gear housing is as standard made from high quality grey cast iron, designed with high stiffness and good vibration damping property. However, nodular cast iron is available as option (typical in high Ice class applications).
Gears are designed and manufactured with high precision and optimised for high load, low vibratory excitation and long lasting. Extensive use of sliding bearing (long lasting) for both journal bearings and thrust bearings. Clutches are of high capacity, hydraulically operated, multiple disc, oil lubricated type.
Gearbox fulfil all Class Society requirements.
The gearboxes are designed in 3D and analysed for full load to ensure excellent performance.
The Direct On-Line (DOL) starter consists of a contactor and a protection device such as a circuit breaker. The contactor is energized when the start button is pressed, and the full line voltage is connected to the motor. Motor is started with propeller in zero pitch position (IZP).
The star-delta starter method applies reduced voltage to the motor, thus reducing current, during startup. This method requires that both ends of motor winding terminals are available. When connected in star each winding has less voltage (1 / √3 ~ 60%), and thus will have reduced starting current and torque. When full speed is reached the motor is connected in delta, having full torque available. Propeller pitch can be increased, and load applied when motor is connected in delta. Motor is started with propeller in zero pitch position (IZP).
Auto-Transformer also applies reduced voltage in steps to the motor during startup. The transformer voltage ratio can be designed to the application, typically having a 50-70% motor voltage during startup. The motor consumes less current at a lower starting voltage. For example, with a 50% tap on the Auto-Transformer, the motor draws half its rated current, or about 25% of what it would draw with a DOL starter. Motor is started with propeller in zero pitch position (IZP).
An electronic soft starter is a starting device that controls the way electricity is provided to the motor by using active switching devices such as thyristors. The device works in both in-line and in-delta configuration modes in three-phase motors.
This starting method is ramping up the motor voltage in the starting sequence resulting in a reduced start-up current, allowing for a smooth and surge-free increase in motor torque. The voltage dips, stress, and wear and tear on the mechanical parts are all reduced as a result. Due to the thyristors there will be harmonic distortion of the current, and the influence on system voltage will depend on starting current and system impedance. Motor is started with propeller in zero pitch position (IZP).
This is an electronic-controlled approach for starting asynchronous motors smoothly. It controls the frequency and current for the motor with electronics inverter circuits, avoiding large startup current. The thruster system's mechanical parts will be protected from high load because of the smooth start-up, and the this will also reduce the load on generators during startup compared to line-starter options. Depending on required performance torque and current may be below nominal values during startup. This is the high-end solution for the starting the thrusters, giving benefits such as smooth start, better energy economy, reduced wear and tear and process optimization. Other benefits include motor speed stability during load changes and a longer motor life overall. Motor is started with propeller in zero pitch position (IZP).
Frequency converter starters may have different interface towards the main switchboard where 6-pulse rectifier is the most common, but both 12/24 pulse and Active Frontend (AFE) are used.6-pulse starters are the most common type, widely used due to the compact design and availability.The disadvantage with the 6-pulse starter is the increased THD during startup, particularly in smaller power system with large thrusters this might be an issue.
To mitigate the THD a 12 or 24 pulse transformer and rectifier may be chosen, typically used for larger thrusters in larger ships.
Frequency converter starters with active front end guarantees sinusoidal current and does not require a transformer. The AFE rectifier and LCL filter is more spacious than the 6-pulse rectifier and is suitable for high end solutions and ships with relatively small power system compared to thruster power.
Please contact us for any further information you may require about this solution
See all contacts
Request for information about our solutions, products and services
Send request
