POLYPHASE CURRENTS.

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tennined by various conditions, sucli as the strength of the cur-rent to be employed, the mass or size of the cores to which theyare applied, and other familiar conditions.

Coils f surround the pole-pieces b, and other coils g are woundon the pole-pieces c. These coils are connected in series in twocircuits, which are branches of a circuit from a generator of alter-nating currents, and they may be so wound, or the respectivecircuits in which they are included may be so arranged, that thecircuit of coils g will have, independently of the particular con-struction described, a higher self-induction than the other circuitor branch.

The function of the shunts or bridges e is that they shall formwith the cores c a closed magnetic circuit for a current up to apredetermined strength, so that when saturated by such currentand unable to carry more lines of force than such a current pro-duces they will to no further appreciable extent interfere withthe development, by a stronger current, of free magnetic poles atthe ends of the cores c.

In such a motor the current is so retarded in the coils g, andthe manifestation of the free magnetism in the poles c is so delayedbeyond the period of maximum magnetic effect in poles b, that astrong torque is produced and the motor operates with approx-imately the power developed in a motor of this kind energizedby independently generated currents differing by a full quarterphase.