Real and Reactive Power - what do they actually mean? #reactivepower

Power systems are characterised as a mix real and reactive power, but these phenomena can be linked to distinct physical mechanisms of energy transfer.

Power is just the rate of energy transfer. In a power system, energy is transferred between the source and circuit. In real power, it is one way - from source to circuit. In reactive power, energy is transferred back and forth between source and circuit, cyclically. But why?

In real power, the voltage excites the electrons and they collide with the ionic lattice, transferring energy to the circuit from the source. Even when the voltage reverses, the collisions still happen so energy is always from source to load.

Reactive power is different. Here, no mechanism for real power transfer exists (if we assume a purely capacitive or inductive circuit, which of course isn't possible in practice!), but energy transfer still happens. This is because the source charges up the electric field when it rises. When it collapses, energy is released from the circuit BACK to the source. Energy is flowing both ways, and its average is actually zero over the cycle. The electric field (for capacitance) and the magnetic field (inductance) provides a storage of energy in the circuit which is cyclically charged up then released back to the source.

[jesseshaver]

This is the best explanation I’ve ever seen on the topic. Everything else is just “real power usable reactive power not”. But this broke down the why

[napoleonperezparedes]

You nail it, good fundamentation and excellent info.

[inductr]

As I for a long time was aware of lagging current in inductive circuits, I got the feeling that capacitive circuits rather distinguish the voltage as lagging (ofcourse current leading), since there is a charging going on, and the voltage cannot change instantly.. (So for inductance the current cannot change instantly) Cheers!