Fig. 1,225.—Diagram illustrating "phase." In wave, vibratory, and simple harmonic motion, phase may be defined as: the portion of one complete vibration, measured either in angle or in time, that any moving point has executed.
Ques. What are the advantages of low frequency?
Ans. The number of revolutions of the rotor is correspondingly low; arc lamps can be more readily operated; better pressure regulation; small motors such as fan motors can be operated more easily from the circuit.
Phase.—As applied to an alternating current, phase denotes the angle turned through by the generating element reckoned from a given instant. Phase is usually measured in degrees from the initial position of zero generation.
If in the diagram fig. 1,225, the elementary armature or loop be the generating element, and the curve at the right be the sine curve representing the current, then the phase of any point p will be the angle φ or angle moved through from the horizontal line, the starting point.
Ques. What is phase difference?
Ans. The angle between the phases of two or more alternating current quantities as measured in degrees.
Ques. What is phase displacement?