Ques. Define a revolving and a stationary winding.
Ans. The words are self-defining; a winding is said to be revolving or stationary according as the armature forms the rotor or stator of the machine.
Ques. What is the significance of the terms lap and wave as applied to alternator windings?
Ans. They have the same meaning as they do when applied to dynamo windings.
Fig. 1,487.—Section of General Electric stationary armature ventilating ducts and winding in position.
These are described in detail in Chapter XVIII. Briefly a lap winding is one composed of lap coils; a wave winding is one which roughly resembles in its diagram, a section of waves.
Half Coil and Whole Coil Windings.—The distinction as to whether the adjacent sides of consecutive coils are placed together under one pole or whether they are separated a distance equal to the pole pitch, gives rise to what is known as half coil and whole coil windings.
A half coil or hemitropic winding is one in which the coils in any phase are situated opposite every other pole, that is, a winding in which there is only one coil per phase per pair of poles, as in fig. 1,488.