Marine PMG

PM shaft generators optimize electrical output

To remain competitive, shipowners are always looking to increase efficiency while lowering operating costs. Ship designers can help by optimizing electrical generation, as variations in electricity consumption can mean the difference between profit and loss.

After all, a ship is essentially a mobile floating power plant on the water – electrical power used onboard must all be generated during a voyage. To avoid using auxiliary electrical generators while moving, ships can use shaft generators to leverage the rotational power of the main propulsion engine shaft and generate electricity for onboard consumption.

Older technologies require the shaft generator to rotate at constant speed, constraining the main engines to avoid varying speeds. Yet implementing variable speed and propeller pitch can help maximize efficiency and fuel consumption. Typically, this is done with sophisticated software that selects the best engine speed and propeller pitch to achieve the optimal fuel consumption point. The engines usually have extra power capacity, which is then available for electrical power generation. Combined load requirements of propulsion power plus electrical power can be used to reach the optimal engine speed and efficiency of the overall system.

At Yaskawa Environmental Energy / The Switch, we’ve developed permanent magnet (PM) generators with variable speeds. They feature a power conditioning unit that stabilizes the variable voltage and frequency output and sends a constant supply of voltage to the main switchboard.

A variety of configurations are possible. For low-speed diesel engines, the PM shaft generator can be installed directly on the main engine shaft, which is coupled right to the generator – reducing bearing counts and lubrication requirements. For medium-speed diesel engines, the PM shaft generator can be connected via a gearbox, with the gearbox ratio optimized for speed and efficiency.

Overall, the benefits and efficiency of the PM shaft generator at full and partial speeds are superior compared to other rotating machine technology.

In addition, the PM shaft generator systems:

  • Offer motoring or power take out (PTO) modes, which enable emergency or in-harbor low-power propulsion without the use of the main engines
  • Lower maintenance costs through the reduction of lubrication needs and more basic machine designs
  • Reduce the required installation space due to compact designs
  • Cut air pollution by optimizing fuel usage
  • Provide low-noise electrical power generation for a quieter vessel
  • Enable parallel co-generation and redundancy when two shaft generators are employed

Like many in the marine industry, it is good to embrace electric and hybrid-electric engine configurations to optimize efficiencies. We hope you’ll consider adding the PM shaft generator as an integral part of your plan.