AC circuit reactive power

[172_driver]

An electrical question here from a driver, regarding reactive power (VAR) in AC circuits. I understand the principle of self-induction in coils and opposition to flow offered by capacitors when they charge up.

As far as I can understand, the inductive reactance causes a back-EMF when ever the flux is changing that cancels out part of the applied EMF, leaving a net EMF less than the applied EMF. Hence the opposition to flow. As far as my imagination goes, this will reduce the current flow and reduce the heat generated. So it's not really higher resistance in the coil, but rather a less strong EMF the electrons will sense. Is this correct thinking, or will reactive power actually heat up the coil like a resistor?

Thanks in advance!!

[ArthurR]

Had to check, long time since I did my courses

Engineers care about apparent power, because even though the current associated with reactive power does no work at the load, it heats the wires, wasting energy. Conductors, transformers and generators must be sized to carry the total current, not just the current that does useful work.


AC power - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/AC_power)

[Bus429]

Just a few musings...

Xc = 1/2(3.14)fC where Xc is capacitve reactance, f = frequency & C = capacitance (by the way, that's 1 over the other values)

Xl = 2(3.14)fL where Xl = inductive reactance, f = frequency & L = inductance

Z = square root of R (squared) + Xl (squared)

Electrical Impedance (Z), is the total opposition that a circuit presents to alternating current. Impedance is measured in ohms and may include resistance (R), inductive reactance (XL), and capacitive reactance (XC).

I also remember: "1 over 2 pi root LC gives you the resonant frequency"
In a series circuit at resonance, Z = min, I = max (SIMAX)
In a parallel circuit at resonance, Z = max, I = min

I need to get out more...

[172_driver]

Oh damn... wikipedia said actually the opposite of what I thought. Just trying to get my head around what actually happens within those coils and circuits when self-induction occurs.

Remember those formulas as well... :p

[Hand Shandy]

And that's why there's 16 million fluorescent tubes on a 737 .

[AvionicsGuy]

XL XC and R are all impedance and will causes power loss through heat... ill give you a more definite answer in sep lol im sitting QD then lol

[Bus429]

Remember, we want to get Power Factor as close as possible to 1 (100%) or, rather, as high as possible.