80

INVENTIONS OF NIKOLA TESLA.

by bolts d. Each plate is formed with four (more or less) longcores e, around which is a space to receive the coil and an equalnumber of short projections e to receive the coils of the resistance-circuit. The plates are generally annular in shape, having anopen space in the centre for receiving the armature g, which Mr.Tesla prefers to wind with closed coils. An alternating currentdivided between the two circuits is retarded as to its phases inthe circuit a to a nrnch greater extent than in the circuit b. By

Fig. 66.

Fig. 6o.

reason of the relative sizes and disposition of the cores and coilsthe magnetic effect of the poles e and f upon the armature closelyapproximate.

An important result secured by the construction shown hereis that these coils which are designed to have the higher self-induction are almost completely surrounded by iron, and that theretardation is thus very materially increased.