What is the purpose of placing a capacitor in series with the primary of a power transformer?

Placing a capacitor in series with the primary of a power transformer serves the purpose of improving the power factor. In electrical systems, particularly in AC circuits, the power factor is a measure of how effectively the electrical power is being converted into useful work output. A low power factor indicates that more current is required to provide the same amount of useful power, which can lead to inefficiencies.

When a capacitor is added in series with the primary winding of a transformer, it creates a leading power factor. This is beneficial because it helps to offset the lagging power factor often associated with inductive loads, enhancing the overall efficiency of the system. The capacitor provides reactive power that counters the reactive power consumed by inductive components, thus reducing the total amount of current drawn from the supply for a given level of actual power required by the load.

This setup not only improves the power factor but can also lead to reduced losses in the electrical system and can help in meeting regulatory requirements for power factor compensation in industrial applications.