Damen Tests Unique Permanent-Magnet Dredge Pump Motor

Successful full performance test CEMEX dredge pump e-motor

The Marine Aggregate Dredger CEMEX Go Innovation, currently under construction for CEMEX Marine UK, is fitted out with a submersed dredge pump. This dredge pump is directly driven by an electric motor – and not an arbitrary one. As a first, the dredge pump drive is a permanent magnet 1,400 kW unit, that last week it underwent a large array of tests – passing them all effortlessly.

Submersed dredge pump drive

The hopper dredger is designed for mining marine aggregates at -55 m below sea level. The submersed Damen dredge pump is directly driven by a continuous electric motor – that is, without a gear box in between. Moreover, the electric motor forms an integral part of the trailing pipe structure. But the story does not end there: the air filled e-motor is of the Permanent Magnet type. And in addition to that, it usually functions at -25 m below the sea level, that is somewhere midway in the trailing suction pipe. This unique electric motor has been put to the test last week.

Performance test

At a specialised performance test facility not only the e-motor but the complete drive train - including the frequency converters - have been tested. During a full week of testing a large number of different tests have been performed. These included a full power test, an overspeed test at 120% of the nominal revolutions and a 130% torque test. All tests have been concluded satisfactorily.

The tests were closely monitored by the project team, including CEMEX representative, the supplier Marotechniek and the Damen project team. The CEMEX project manager Mark D.Williams said : “I was impressed with the quality of the equipment on test.” After a full week of testing, all gear will be shipped to the Netherlands shortly, where it will be fitted out with the dredge pump parts, and mounted into the trailing pipe system.

A technical feat

The 1,400 kW electric motor on test is the largest Permanent Magnet motor used in a submersed dredge pump drive to date. The air filled motor is smaller, lighter and more efficient than conventional asynchronous oil filled ones – with a staggering measured efficiency of 97% including friction of all bearings and mechanical-seal. The electric motor is controlled by a water cooled AFE drive. The electric motor has been designed in close cooperation between Marotechniek and Damen Dredging Equipment.

Background information

The hopper dredger MAD3500 CEMEX Go Innovation is currently under construction at the Damen Shipyard in Galati, Romania. The dredging equipment however is constructed by Damen Dredging Equipment in the Netherlands. The dredger will be used by CEMEX Marine UK to mine aggregates in the British Channel and North Sea. The innovative dredger has a number of special features, including the permanent magnet electric motor, which powers the dredge pump for mining aggregates at -55m.