Permanent magnet machines for shaft generator systems and main propulsion

Permanent magnet (PM) technology has already proven its worth across many industries – from renewable energy to electric transportation. But in the maritime sector, it is only in recent years that its full potential has begun to unfold. The Switch, a pioneer in megawatt-class PM machines, has been at the forefront of this shift, adapting its proven technology from the wind power industry to meet the demanding conditions at sea.

While PM machines have existed for over a century, it was only with the invention of Neodymium magnets and the evolution of power electronics that they became a viable choice for large-scale applications. Today, high-power PM machines are used in power generation and propulsion across industries – and increasingly, in shipping.

For The Switch, the transition from wind to marine use was a natural step. With the shipping industry’s growing focus on decarbonization and energy efficiency, the company saw a perfect opportunity to deliver cleaner, more efficient performance through PM-based technology – just as it has successfully done in the wind sector for years.

Why PM makes sense for ships
The journey began by rethinking onboard power generation. Ships have long sought more efficient ways to produce electricity at sea. Traditional auxiliary gensets, running on four-stroke engines, consume more fuel and require additional maintenance. In contrast, a shaft generator produces electricity using the ship’s most efficient two-stroke engine.

Building on this, The Switch replaced conventional electrically excited synchronous generators (EESGs) with PM machines. This eliminated the need for external excitation systems, reducing energy losses and further improving the shaft generator design. The result: a smaller, lighter and more efficient machine that delivers lower fuel consumption and emissions – exactly what modern shipowners are seeking.

In practice, this can translate into fuel savings worth millions of dollars over a vessel’s lifetime. 

In addition, PM machines offer other significant benefits. They maintain high efficiency even at low rotational speeds. That’s where traditional machines suffer significant losses. Their compact design – often 30–40% lighter – saves valuable space in the engine room. And thanks to the considerably lower inertia, they improve the torsional vibration characteristics of the propulsion line – another critical factor for reliable operation. 

Built for today’s regulations – and tomorrow’s fleets
Importantly, the efficiency of PM machines aligns perfectly with the shipping industry’s push for greener operations. Especially with the International Maritime Organization’s (IMO’s) stricter emission measures, they offer a practical way to meet today’s targets, while also helping future-proof for tomorrow.

Every percentage point of improved generator efficiency reduces both fuel burn and emissions, supporting compliance and profitability at the same time. This dual benefit has made Permanent Magnet shaft generators one of the most attractive solutions for shipowners worldwide.

Expanding into propulsion
Since the first installations in 2015, The Switch’s PM shaft generators have accumulated more than five million operating hours, demonstrating exceptional reliability and performance. Today, over 300 units have been delivered worldwide, following a sharp surge in orders after the IMO’s new regulations.

Building on this success, the same proven PM technology is now finding its way into propulsion applications as well. For example, The Switch propulsion motors are an integral part of the award-winning M/S Nukumi. And with ongoing innovations, including concepts like tandem motor configurations, the company is ensuring that PM propulsion systems are safe and reliable under all operating conditions.

Innovation, experience and belief – powering the progress
The Switch’s continued development of PM technology – from its roots in wind applications to today’s shaft generators and main propulsion systems – shows how innovation, experience and a strong belief in the technology can drive real progress.

In record time, permanent magnet machines have redefined what’s possible in marine power generation and propulsion. But the journey behind this technology – and the engineering choices that made it successful – is worth exploring.

Discover the full story in the Talking Point: “Creating new savings for the maritime industry.”