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Power factor

Vilnis Vesma's picture
  • Member since 2021
  • 11 items added with 5,730 views
  • Jul 23, 2021

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Poor power factor increases the stress on electrical distribution cabling, switchgear and transformers but it's hard to get your head around. This kitchen table-top demonstration explains both the principle and the solution (capacitors) using string, springs and a pulley wheel.

Bob Meinetz's picture
Bob Meinetz on Jul 25, 2021

Vilnis, another winner. Everyone at Energy Central would benefit from watching your intuitive tabletop demonstrations.

Question: with AC power factor, is the lag of current behind voltage attributable to resistance in the wires, momenta of the electrons as they switch direction, or a combination of the two?

Vilnis Vesma's picture
Vilnis Vesma on Jul 26, 2021

It's actually caused by back EMF from inductive loads like motors. The changing current induces a magnetic field but the changing magnetic field in turn induces a voltage opposing the flow of current. By contrast when a small voltage is applied to a capacitor, high current immediately starts to  flow but reduces as the capacitor fills with electric charge. So the alternating current in a capacitor leads the alternating voltage rather than lagging as happens with an inductive load. Hence a capacitor can be used in parallel with an inductive load to bring the current back in phase with voltage 

Bob Meinetz's picture
Bob Meinetz on Jul 26, 2021

Interesting. I imagine the capacitor would introduce some loss of power to resistance (your pulley), but less than the uncorrected power factor?

Vilnis Vesma's picture
Thank Vilnis for the Post!
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