All ship electrical machines have two sets of coils:
one set (field coil in generator and motor, and primary coil in transformer) produces the working magnetic flux φ and the
other set (armature coil in generator and motor, and secondary coil in transformer) reacts to flux φ and produces an electromotive force (voltage) in the generator and transformer, and a mechanical force (torque) in the motor.
Both sets of coils are embedded in magnetic steel to produce the required flux with a minimum magnetizing (field excitation) current.
The electromagnetic interaction between two sets of coils is governed by the following basic laws of physics.
