In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating current voltages that are offset in time by one-third of the period. A three-phase system may be arranged in delta (∆) or star (Y) (also denoted as wye in some areas). A wye system allows the use of two different voltages from all three phases, such as a 230/400V system which provides 230V between the neutral (centre hub) and any one of the phases, and 400V across any two phases. A delta system arrangement only provides one voltage magnitude, however it has a greater redundancy as it may continue to operate normally with one of the three supply windings offline, albeit at 57.7% of total capacity. Harmonic currents in the neutral may become very large if non-linear loads are connected.
"Balanced Three-Phase Voltages"
Three-phase voltages are often produced with a three-phase ac generator or alternator whose cross-sectional view is shown below,
The voltage sources can be either wye-connected as shown in Fig.(a) or delta-connected as in Fig (b).
Balanced phase voltages are equal in magnitude and are out
of phase with each other by 120◦.
The phase sequence is the time order in which the voltages pass through their respective maximum values.
A balanced load is one in which the phase impedances
are equal in magnitude and in phase.
Types of Connections:
- Balanced Wye-Wye Connection
- Balanced Wye-Delta Connection
- Balanced Delta-Delta Connection
- Balanced Delta-Wye Connection
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