Why Reactive Power Flows

Why Does Reactive Power Flow If It Does No Useful Work? In a purely resistive load, voltage and current rise and fall together. Electrical energy moves from the source to the load and is converted into heat or useful work. But inductors and capacitors behave differently. An inductor stores energy in its magnetic field. During one part of the AC cycle, it draws energy from the source. During the next part, its magnetic field collapses and sends that energy back. A capacitor does the same through its electric field—charging from the source, then returning the stored energy. So this energy continuously moves back and forth between the source and the load. Over one complete cycle, the net energy consumed by the ideal reactive element is zero. But current still flows through the wires. That current increases conductor losses, voltage drop and equipment capacity requirements, even though it produces no net useful work. This back-and-forth power is called reactive power, measured in VAR. Real power performs work. Reactive power supports electric and magnetic fields. Together, they determine apparent power and the system’s power factor.