Vibration aspects of the design of a new generation of DC motors for the propulsion of submarines

The authors discuss vibration and audible noise aspects of a new series of DC motors for the propulsion of submarines. A number of sources of vibrations and audible noise exists: external mechanical; external electrical; internal electrical; and electromagnetic forces. All these sources are discussed individually. Measurements show that an adapted motor construction combined with independent choppers for field and armature winding yields acceptable results. Except for the influence of the brushes, the internal mechanical sources are negligible. For predicting the vibrations and the audible noise originating from electromagnetic forces, the concept of Maxwell stress can be adapted. The forces may be split into symmetrical and asymmetrical components, and a fourier analysis may be used. An optimized main pole shape can be obtained using the finite element technique