Water-jacket cooling eliminates the need for an external cooling unit, enabling a smaller footprint, lower maintenance requirements and quieter operation
The Switch has announced the launch of its latest permanent magnet (PM) machine for marine applications, the PMM850M, developed to support shipowners in reducing fuel consumption, emissions and operating costs.
Engineered as a compact, high-efficiency solution, the PMM850M offers high power density within a small footprint, making it suitable for both newbuild and retrofit installations where space optimisation is critical. Deliveries are scheduled to begin in 2027.
Key advantages for customers:
- Reduced fuel consumption thanks to high electrical efficiency.
- Lower CO₂ and NOx emissions, supporting compliance with environmental regulations.
- Minimal maintenance requirements due to the brushless design and simplified cooling system.
- High reliability supported by a proven PM technology platform with more than 5 million operating hours and no failures causing vessel downtime.
- Compact footprint, enabling greater flexibility in vessel layout and installation.
- Quieter operation and compliance with increasingly strict airborne and underwater radiated noise regulations thanks to the absence of external cooling fans.
Designed for shaft generator and propulsion applications, the PMM850M targets vessels operating in the 500 kW to 1.5 MW power range, filling a gap at the lower end of The Switch’s PM machine portfolio.
The launch addresses a growing market need for a smaller and more cost-efficient machine for vessels where even the PMM1000M may be too large to install.
“We often see that space in the engine room is extremely limited, especially in vessels with narrow hull designs. Our goal was to develop a compact, cost-effective machine for the lower power end without compromising efficiency,” says Jussi Puranen, Product Line Director, Electric Machines at The Switch. “By combining water-jacket cooling with our high power density machine design, we have created a solution that is extremely compact while still delivering excellent efficiency throughout the entire operating range. With recent volatility in energy prices, maximizing efficiency is more important than ever to minimize fuel consumption.”
As vessel electrification continues to advance, the PMM850M is particularly suited for smaller bulk carriers, product tankers and coastal trading vessels, specifically narrow-hulled shortsea ships where engine room space is often constrained. Demand is especially visible in regional markets with large fleets of smaller ships, such as Japan, where many coastal vessels have narrow hull designs.
A key feature of the PMM850M is its water-jacket cooling system, which removes the need for external cooling units, including fans and heat exchangers. Cooling water flows through a hollow channel integrated into the machine housing and connects to the vessel’s freshwater cooling system.
This approach simplifies the overall mechanical design while reducing footprint and operating expenses.
“Without an external cooling unit, the machine becomes significantly more compact,” Puranen says. “It also eliminates cooling fans, which means fewer components to maintain and lower operating noise.”
The new machine is based on The Switch’s proven PM technology platform, built on more than 20 years of experience.
PM machines deliver particularly strong performance at partial loads, where ships frequently operate. Compared with conventional induction or electrically excited machines, they typically achieve 2–4% higher electrical efficiency at the rated point – and even more at partial loads. This helps reduce fuel consumption and associated greenhouse gas emissions.
“The main difference is that PM machines don’t require electrical power for magnetisation,” Puranen says. “In conventional machines, that power demand remains even when the load decreases, reducing efficiency. With PM machines, this loss is eliminated.”
Depending on the application, the PMM850M can be delivered with or without bearings. In addition, its modular design allows the axial length of the machine to be scaled up or down depending on the power rating, matching it perfectly to the customer’s application without oversizing.
Final testing is scheduled for the second half of 2026, and first deliveries are expected to start soon after that.
With the latest addition of the PMM850M, The Switch PM machine portfolio now includes more than 70 variants enabled by a scalable platform, covering a power range from roughly 500 kW to over 10 MW. By extending its PM machine range into lower-power and space-constrained applications, The Switch aims to ensure that vessels of all sizes can benefit from the efficiency and reliability advantages of PM technology.
PM machines are particularly well suited to modern electric propulsion architectures. Their high efficiency across a wide load range, combined with fast response and compatibility with variable-speed drives, makes them ideal for integration into shaft generator systems, PTI/PTO configurations and hybrid or fully electric propulsion architectures.
