5MW super motor takes shape in the UK

The rotor assembly for the world`s first high-temperature superconductor (HTS) ship propulsion motor has been shipped from the US to the UK where it will be assembled into a stator, ready for testing to start by July.

The 5MW, 230rpm motor, being built under a $8m contract from the US Navy`s Office of Naval Research, is seen as a forerunner of a new generation of compact, efficient ship propulsion motors which could help to create a market worth as much as $4bn within ten years.

The motor`s rotor (shown above during testing) has been built by the American Superconductor Corporation and will be incorporated by Alstom Power Conversion into a stator that Alstom is building in the UK. The rotor includes the shaft, torque tube, HTS coils, a power electronic exciter, and refrigeration components to keep it at the extremely low temperatures needed for superconductivity to occur.

The rotor windings use a new design that is said to increase the efficiency and shrink the size of the motor, resulting in a machine that will be about half the size and weight of an equivalent conventional motor with copper coils. Its losses will be less than half those of a standard motor.

These characteristics will allow ships to carry more cargo or passengers and, in some applications, will lead to faster vessels with new hull designs. "We believe that HTS propulsion motors will revolutionise the commercial marine and naval ship industries," says Dave Paratore, general manager of American Superconductor`s electric motors and generators business.

"While our 5MW motor is already a commercially viable size, we intend it to be a risk mitigation step towards the development of HTS motors with power ratings up to about 40MW," he adds. The company aims to start deliveries of commercial 5MW propulsion motors within two to three years.

At present, the global market for electrical propulsion motors is worth around $400m a year. Sales are forecast to grow at a compound annual rate of more than 20% over the coming decade to reach a total of $2-4bn. A recent study by the maritime consultancy MSCL predicted that electric drives will become the dominant form of ship propulsion within ten years.

• In a separate project for the US Navy, developers are working on what, they say, will be the world`s most powerful permanent magnet motor. The motor is intended for use in the Navy`s next-generation destroyer, known as the DD 21 (shown above), which is being developed at a cost of $2.9bn. The motor will have removable magnet modules and segmented stators so that it does not need to be removed from the ship for repair or maintenance. The DD 21 team is being led by Northrop Grumann, with the electromagnetic components and drive electronics being developed by Kaman Aerospace and Power Technology Incorporated.