Balanced Wye - Wye Connection
- The wye-wye arrangement requires a neutral connection between the source and the primary of the transformers not only to assure balanced line-to-neutral voltage, but also to provide a path for the third-harmonic component in the exciting current of the transformers. Without the primary neutral connection, serious unbalances in the line-neutral voltage may result from (a) unequal exciting admittances among the three transformers and (b) unbalanced line-to-neutral loads in the secondary. Furthermore, if the third harmonics are suppressed in the exciting current, large third harmonic components may appear in the line-to-neutral voltages. The wye-wye arrangement is, therefore, a four-wire system if balanced voltages are to be assured. The delta-delta arrangement is, on the other hand, a 3-wire system.
In the three phase circuit arrangements displayed, each leg is shown with an impedance. If the impedances are identical on each phase, then the load is said to be balanced. A three-phase source is balanced when each leg produces equal magnitude voltage, with 
phase difference between any two phases.
Power Factor Correction
The process of increasing power factor without altering the voltage or the current to the original load is called Power Factor Correction.
Alternatively, power factor correction may be viewed as the addition of a reactive element usually a capacitor in parallel with the load in order to make the power factor closer to unity.An inductive load is modeled as a series of combination of an inductor and a resistor.
The effect of adding a capacitor can be illustrated using either the power triangle or the phasor diagram of the currents involved. Adding the capacitor has caused the phase angle between the supplied voltage and the current to reduce from ϴ1 to ϴ2,
Thereby increasing the power factor.
Therefore, it is beneficial to both the power company and the consumer that every effort is made to minimize current level or keep the power factor as close to unity as possible. By choosing a suitable size for the capacitor, the current can be made completely in phase with the voltage, implying unity power factor.
Capacitive Power Factor correction (PFC) is applied to electric circuits as a means of minimizing the inductive component of the current and thereby reducing the losses in the supply.
The introduction of Power Factor Correction capacitors is a widely recognized method of reducing an electrical load, thus minimizing wasted energy and hence improving the efficiency of a plant and reducing the electricity bill.It is not usually necessary to reach unity, ie Power Factor 1, since most supply companies are happy with a PF of 0.95 to 0.98
