Windings

Author: E.E. Kimberly

A direct-current generator may have any even number of poles. The number of poles used is a matter of design economics and depends chiefly on the speed and power output for which the generator is intended.

A wiring diagram of a four-pole generator is shown in Fig. 10-6. In a two-pole generator the poles are 180 degrees apart and the emf of a conductor passes through one cycle of 360 degrees in every revolution or for every two poles passed. In a four-pole generator two cycles of emf are generated in every revolution; and, therefore, 720 electrical degrees are passed through in every 360 mechanical degrees. In any generator there are P/2 electrical degrees in a mechanical degree, where P is the number of field poles. A conductor is said to have passed through 360 electrical degrees when it has experienced one complete cycle of generated emf.

In Fig. 10-6 the active parts of the conductors lying in the armature slots, as 1, 2, 3, 4, etc., are shown radially for convenience. The end connections shown dotted are on the back end of the armature. Conductors and 2, 3 and 4, etc, lie in the bottom and top, respectively, of one slot. The brushes a, b, c, and d are shown on the inside of the commutator for convenience.