Next generation drive trains based on permanent magnet (PM) technology from The Switch are game changers in their own right when it comes to reaching the highest energy efficiency and lowering the costs of operation. Additionally, they help comply with future environmental legislations. Solutions such as these enable ships to stay afloat and profit in the sea of fierce competition.
Permanent magnet machines – a special force for shaft generators
The shaft generator has been successfully used on board ships for the past 30 years. The main benefit of adding a shaft generator is to produce electrical power with the main engines that have lower fuel consumption and run on cheaper heavy fuel oil, thereby significantly reducing the use of auxiliary generators. The downside, however, is that the propulsion machinery can only be run at constant speed.
The other alternative has been to operate without a shaft generator. In this case, ships continue to take advantage of the main engine’s variable speed operation while auxiliary generators produce electricity on board. The downside is that the ship operator pays a premium in higher fuel cost as well as auxiliary generator maintenance costs.
Now merchant vessels can get the best of both worlds by using a game-changing solution that combines advanced control with The Switch PM machine and frequency converter technology. This enables vessels to produce electricity with better efficiency for the entire ship’s network, lower costs by keeping auxiliary generators off – and allow the main engines to operate at variable speed and generate electricity. In total, it represents major operational savings for vessels with 4-stroke, but in particular 2-stroke engines.
Next generation, electrical drive trains that lead to exceptional energy efficiency and lower operational costs are built from a PM motor and a frequency converter as the major components. The controller acts as the brains for energy efficiency, keeping the network stable regardless of external conditions, such as waves, speed and other influential factors.
Although a newcomer to the shipping industry, PM technology with its matchless design flexibility has reached unprecedented success in numerous other industries. Thanks to their higher power density, PM machines can be more compact, lighter in weight and smaller in size.
Game-changing solution for drive trains from The Switch
- PM machine: provides unmatched power density, energy efficiency, design flexibility and operational reliability
- Frequency converter: robust and liquid cooled
- Control: the brains for energy efficiency
- Take me home / boost mode: enables use of auxiliary generators and/or batteries
- DC-link: brings energy efficiency to the entire vessel
PM technology for unmatched power density
PM technology has been proven in numerous industries to provide energy efficiency, high power density, design flexibility and operational reliability. Now these same advantages are available for numerous marine applications.
A PM machine gives high-efficiency performance over the entire operating range, significantly cutting back on fuel consumption. A PM machine is typically 2-4% more efficient at full load and 10% more efficient at part loads compared with induction machines. These efficiencies result from a lack of current losses in the rotor, the absence of an exciter, and reduced winding losses.
High power density
A synchronous PM machine contains Neodymium-Iron-Boron (NdFeB) magnets, materials with a very high flux density, which makes them ideal for variable speed generators throughout the entire speed range. The magnetic field is created with almost zero rotor losses.
Thanks to the improved high density, the size and weight of a PM machine can be substantially reduced. This leads to greater flexibility with the limited space available in ship configurations.
PM machines have proven their high reliability and durability under extremely harsh operating conditions in many industrial applications. They deliver excellent performance with corrosion resistance and temperature tolerance.
Frequency converter superiorities
Adding a frequency converter to a shaft generator allows a ship to control its speed and ensure a stable source of electricity for the ship’s network. The frequency converter allows the ship to choose between taking power from the main engine or from the auxiliary generators, as deemed best.
Optimized for best efficiency
The Switch frequency converter is based on IGBTs with advanced vector control technology and is optimized to work with PM machines for the best overall system efficiency.
Active front-end speed control
With active front-end (AFE) frequency drive technology, The Switch converter enables Power Take-In (PTI) and Power Take-Out (PTO), while allowing a shaft generator to operate at variable speed. This technology enables the use of a PM machine to be operated as a motor or a generator according to the application requirement. Additional AFE benefits include lower harmonics, resulting in better electricity quality.
Liquid cooling and thermal management
Frequency converters offer a modular, lightweight design with liquid cooling and exceptional thermal management. Their small footprint makes them easy to locate within limited vessel space.
Reliability in harshest conditions
The Switch frequency converter features a rugged IP54-class cabinet. It is designed to be used in harsh environments, such as those on the open seas, and is easily accessible for installation and maintenance.
All-new opportunity for merchant ships
The combination of The Switch PM and frequency converter technology opens up all-new opportunities for hybrid propulsion systems, namely in the large merchant shipping sector, where 2-stroke main engines are the preferred type of prime mover.
Ocean-going merchant vessels are predominantly propelled by fixed pitch propellers that are directly driven from slow-speed, 2-stroke main engines. Along with being very reliable, the 2-stroke main engine is also able to keep fuel consumption at least 20 g/kWh lower compared with a medium speed 4-stroke main engine.
As a merchant vessel sails long distances in the deep sea during most of its operating time, fuel economy is the most important factor after safety and reliability. The 2-stroke main engine operates on slow speeds, equivalent to the required propeller speeds. Therefore, this type of engine is directly connected to the propeller via an intermediate shaft, requiring no additional gearing to match the required revolutions. This leads to a more straightforward propulsion system with fewer components.
Traditionally, adding a shaft generator to this system required special equipment, such as tunnel gears with a step-up PTO shaft for the generator drive. These arrangements add complexity to the system and are fairly costly. A direct-drive PM shaft generator with a variable frequency drive offers the advantages of a hybrid propulsion system to the 2-stroke main engine driven propulsion system.
In the direct-drive PM shaft generator, the rotor is mounted on the intermediate shaft of the propulsion system. Mass and inertia are very low and thus the impact on propulsion system torsional vibration calculations (TVC) remains minimal. No additional bearings are required, thus the propeller shaft system design remains uncompromised.
Up to €50,000 per month in fuel savings
Advantages for these large merchant vessels include energy efficiency and lower operational costs. First, the new drive train enables electrical production with the main engine, which provides much greater energy efficiency than with the auxiliary generator. Second, it can use heavy fuel oil or liquefied natural gas (LNG) as fuel, which are much cheaper fuel sources than the marine diesel oil used by auxiliary generators.
And finally, from an electrical perspective, a solution from The Switch can be dimensioned to allow ships to operate in a combination mode of a controllable pitch, angle and speed. This ensures that the ships can run in the most efficient way with the best available technology.
In terms of actual numbers, merchant ships can save up to 50% in energy consumption by lowering their speeds by 4 knots. Running the ship at lower speeds also requires less maintenance. Moreover, by adding the latest technology, a ship owner can save up to €50,000 per month in fuel costs, which may add up to 7% more profit per year.