The invention relates to an alternating hybrid excitation assembly and the application of the alternating hybrid excitation assembly to a rotary motor, a linear motor and a transformer. The alternating hybrid excitation assembly comprises an even number of iron cores and a plurality of magnetic isolation layers arranged between the iron cores, wherein the iron cores and the magnetic isolation layers form a closed loop or an open loop, each iron core is provided with one or two notches, permanent magnets are inlaid in the notches of the iron cores, the two magnetic pole faces of each permanent magnet are closely attached to two opposite sides of the notch of the corresponding iron core, and a gap is reserved between one side face of each permanent magnet and the side edge of the notch of the corresponding iron core; and furthermore, the permanent magnets inlaid in the notches of every two adjacent iron cores have opposite magnetic polarity directions, and an excitation coil surrounds the iron cores. According to the alternating hybrid excitation assembly, a permanent magnetic potential and an excitation magnetic potential are superimposed to form an alternating hybrid excitation magnetic field, and thus electromagnetic energy efficiency is improved. The invention further provides embodiments of the alternating hybrid excitation assembly applied to the rotary motor, the linear motor and the transformer.