By such practical methods Edison found that the thin, laminated cores of sheet iron gave the least heat, and had the least amount of wasteful eddy currents. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.
The laminated iron core of the armature, formed of thin iron disks, was 33 3/4 inches long, and had an internal diameter of 12 1/2 inches, and an external diameter of 26 7/16 inches. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.