Slotless-armature DC drives for surface warship propulsion

A slotless armature with multiplex connection can operate with higher coil voltage and current than a conventional armature before the commutation limits are reached and so can achieve higher power ratings. DC motors may be designed for powers of tens of MW. The resulting machine may use a conventional field system, permanent magnets or superconducting coils for excitation. Alternative machine designs are compared. The superconducting field offers the lightest and most compact overall arrangement and the best efficiency. Permanent-magnet excitation offers the simplest and possibly the cheapest solution.