New design for our water jacket cooled motors




New design for our water jacket cooled motors

A new water-cooled electric motor design for today’s more efficient and better optimized ships.


Today’s variable speed electric motors provide benefits in terms of space-saving, low ambient and structure-borne noise and reliability. At the same time they have to be designed and engineered to high standards to comply with complex marine requirements.

Marelli Motori first introduced the water jacket motor in 2001. The integral water jacket coolers provide high power output in a more compact size when compared to traditional designs, where the heat exchanger is installed on the top of the motor frame. Due to the typical propeller load versus speed profile, the motor is self cooled and the water jacket provides a natural sound silencer in turn reducing both emissions and structural vibrations.

We have just finished to develop another model of the new and optimized series of water jacked cooled motors, the new B5J 630 frame, developed for marine main propulsion applications. This motor (2910kW @ 60H z) has just been tested in-house at full load. The structural strength has been increased, the motor case has been completely redesigned, the vibration level greatly reduced, the cooling circuits optimized and the thermal performance improved, therefore enhancing all the benefits already given by our jacked cooling method. 

A detailed multiphysics simulation approach has been used to avoid potential resonances throughout the operating speed range. Bearings and shaft arrangements have been verified in worst-case scenarios, to take static and dynamic ship roll and pitch motion into account.

The potential effects on windings, including voltage peaks and voltage gradients, and on rotor circulating currents, of using variable speed drive technology have been considered and appropriate design solutions adopted to take these into account. 

Given the improvement of the internal air cooling efficiency and the water jacket circulation system which effectively minimizes power loss, the efficiency of the motors is increased. The water jacket design has further advantages in terms of lower structure-borne noise levels, while the power density, compact design and straightforward installation benefit naval architects and shipyards.

Discover more about our water jacket motor series.