power circuit or power system: load resistor's power dissipation were substantial distinction between a power circuit and a regular circuit: size and cost of wiring necessary to deliver power from the AC source to the load Vol – Chapter 10~12 Disadvantages: the danger of electric shock from high voltages → tradeoff between efficiency and danger What voltage to use for powering loads? ◦ ◦ ◦ ◦ North America: 120 V Japan: 110 V European: 240 V Vietnam: ??? V What frequency to use: 50 Hz or 60 Hz? Alternative solution: Alternative solution → Split–phase (AC) or three–wire Ineutral? ? → similar to split–phase: no neutral conductor → star or Y True power (P): ◦ actual amount of power being used, or dissipated, in a circuit ◦ Unit: W Reactive power (Q) ◦ inductors and capacitors dissipate zero power ◦ drop voltage and draw current gives the deceptive impression that they actually dissipate power → “phantom power” ◦ Unit: VAR Apparent power (S) ◦ Combination of reactive power and true power ◦ Unit: VA Calculate the apparent power and power factor What is the unit of power factor? Calculate the apparent power and power factor after having a 80 uF capacitor parallel to the load What is the merit?