Category: THREE-PHASE AC CIRCUITS

In a three-phase system, there are three voltages having same magnitude and frequency displaced by an angle of 120° electrical. They are attaining their positive maximum value in a particular order. The order in which the voltages (or emfs) in the three phases attain their maximum positive value is called the phase sequence. The emfs…

The three phases may be represented by numbers (1, 2, and 3) or by letters (a, b, and c) or by colours (red, yellow, and blue,i.e.,R, Y, and B). In India, they are named by R, Y, and B,that is, red, yellow, and blue.

In a three-phase system, there are three equal voltages (or emfs) of the same frequency having a phase difference of 120°. These voltages can be produced by a three-phase, AC generator having three identical windings (or phases) displaced 120° electrical apart. When these windings are rotated in a stationary magnitude field (see Fig. 8.1(a)) or…

The following are the main advantages of three-phase system over single-phase system:

Poly means many (more than one) and phase means windings or circuits, each of them having a single alternating voltage of the same magnitude and frequency. Hence, a polyphase system is essentially a combination of two or more voltages having same magnitude and frequency, but displaced from one another by equal electrical angle. This angular displacement between the adjacent…

Although single-phase system is employed for the operation of almost all the domestic and commercial appliances, for example, lamps, fans, electric irons, refrigerators, TV sets, washing machines, exhaust fans, computers, etc. However, it has its own limitations in the field of generation, transmission, distribution, and industrial applications. Due to this, it has been replaced by…