Importance

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Abstract

An electromagnetic machine (particularly an electric motor) based on the design described in British Patent Application No. 48794/74. Iron losses in this type of machine are reduced by laminating the rotor backing plate (2,4). Although a spiral lamination (FIG. 3) is preferred, an axial stack of insulated plates (FIG. 2) may be employed. Interpolar flux leakage is reduced by radially staggering the U-shaped pole pieces around the stator coil (FIG. 4). In addition or alternatively differently shaped pole pieces may be employed, alternately, around the stator assembly (FIG. 5). Eddy current losses are reduced by replacing the backing plates (2,4) and separate magnets (1,1a,3,3a) with plates (12,14) of sintered magnetic material, permanently magnetized to present alternate North and South poles, therearound. Alternatively eddy current losses are reduced by forming the backing plates from sintered ferrite material (16,18) and mounting either an array of discrete magnets (20,20a,22,22a) or a magnetized ring such as (16,18), therearound.

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First Claim