Steerprop to launch permanent magnet propulsors

According to Steerprop managing director Jussi Seppälä, market demand for more compact designs and greater efficiency has prompted the development of company’s new CRP ECO LM model.

Jussi Puranen of The Switch explained that in a conventional synchronous generator, the magnetic field is created by feeding current into the rotor winding, but the “massive field poles” bring both losses and complexity into the system. By contrast, a much simpler and more efficient field is created by using permanent magnets around a hollow steel cylinder instead of a rotor, reducing components and losses as well as raising efficiency and giving instantaneous torque.

There are also a number of design advantages: a PM unit can be between 30% and 50% smaller with a weight reduction of up to 40%, partly conferred by the hollow rotor design. This again lowers inertia, an important point if shaft line vibration is a consideration.

Steerprop’s CRP ECO LM is a mechanical, fully azimuthing propulsor with electric motor and a flexibly coupled shaftline. The system yields a number of benefits, according to Aarno Niemi, Steerprop’s automation manager: not only is the simplicity likely to yield extremely low maintenance, but having a hollow ‘donut’ rotor has “allowed us to put the shaft line straight through the centre”.

Niemi added that everything is integrated into one package for easy installation – even if it’s a late consideration. Further, he added that keeping the electric motor above the waterline means it can be reached easily.

The price will be at a slight premium to Z-drive, induction motor units, Seppälä confirmed.

The new PM-model will initially be available in Steerprop’s large CRP ECO units (5MW to more than 10MW), and for the smaller CRP units (0.8–1.2MW and 3MW).

By Stevie Knight