A TIMELESS CHRISTMAS CLASSIC!
FOR THE ENTIRE HUMAN FAMILY...
BiTT 5.0 WITH RESISTIVE LOAD VARIATIONS.
CHEERS
Thane
http://www.allaboutcircuits.com/vol_2/chpt_11/2.html
REACTIVE POWER vs REAL and APPARENT POWER
We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This "phantom power" is called REACTIVE POWER, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit's voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S.
As a rule, true power is a function of a circuit's dissipative elements, usually resistances (R). Reactive power is a function of a circuit's reactance (X). Apparent power is a function of a circuit's total impedance (Z). Since we're dealing with scalar quantities for power calculation, any complex starting quantities such as voltage, current, and impedance must be represented by their polar magnitudes, not by real or imaginary rectangular components. For instance, if I'm calculating true power from current and resistance, I must use the polar magnitude for current, and not merely the "real" or "imaginary" portion of the current. If I'm calculating apparent power from voltage and impedance, both of these formerly complex quantities must be reduced to their polar magnitudes for the scalar arithmetic.
There are several power equations relating the three types of power to resistance, reactance, and impedance (all using scalar quantities):
Please note that there are two equations each for the calculation of true and reactive power. There are three equations available for the calculation of apparent power, P=IE being useful only for that purpose.
http://en.wikipedia.org/wiki/AC_power
REAL, REACTIVE, and APPARENT POWER
The apparent power is the vector sum of real and reactive power.
Real power (P)
Reactive power (Q)
Complex power (S)
Apparent Power (|S|)
Phase of Current (φ)In a simple alternating current (AC) circuit consisting of a source and a linear load, both the current and voltage are sinusoidal. If the load is purely resistive, the two quantities reverse their polarity at the same time. At every instant the product of voltage and current is positive, indicating that the direction of energy flow does not reverse. In this case, only real power is transferred.
If the load is purely reactive, then the voltage and current are 90 degrees out of phase. For half of each cycle, the product of voltage and current is positive, but on the other half of the cycle, the product is negative, indicating that on average, exactly as much energy flows toward the load as flows back. There is no net energy flow over one cycle. In this case, only reactive energy flows—there is no net transfer of energy to the load.
Practical loads have resistance, inductance, and capacitance, so both real and reactive power will flow to real loads. Power engineers measure apparent power as the vector sum of real and reactive power. Apparent power is the product of the root-mean-square voltage and current.
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.
Does increaing the voltage slightly cause the power factor to drop because it makes the core saturated so that no back-EMF can get through?
Galv140577 2 months ago
@Galv140577 Yes. Cheers Thane
ThaneCHeins 2 months ago
Hi Thane, what if you took two toroids, one primary on each, sandwiched them together, connected the primaries in parallel so that the flux are in opposite, then wrap one secondary around the two toroids, possibly with some extra turns on just one of the cores, would that give the same effect?
nilrehob 1 year ago
@nilrehob,
Can you send me a picture and save 1000 words?
Thanks
Thane
thane_heins@yahoo.ca
ThaneCHeins 1 year ago