Page 24 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

FUNDAMENTALS OF ELECTRIC SYSTEMS

FUNDAMENTALS OF ELECTRIC SYSTEMS 1.23

Power in Three-Phase Systems
The average power in a single-phase ac circuit is given by
P V I cos
T p p p
where is the power factor angle. The total power delivered in a balanced three-phase cir-
p
cuit is given by
P 3 (V I cos )
T p p p
The total power expressed in terms of line voltages and currents for a wye or delta con-
nection is
P 3 V I cos
T l l p

FIGURE 1.29 (a) Wye connection; (b) delta connection.

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