MEEN 225 Lecture Notes - Lecture 14: Ac Power, Phasor

• School: Texas A&M University
• Department: Mechanical Engineering
• Course: MEEN 225
• Professor: John Steven Haglund

Document Summary

Complex power, s: the product of the voltage across the load and the current through the load, unit in va (volts-amperes, given by: s = v i* S = (v v )(i - i )* = (v v )(i + i ) Power triangle: the relationship btwn s, p and q can be represented graphically by a power triangle. For inductive load, since > 0, q = vi sin + = +ve q. For capacitive load, since < 0, q = vi sin - = -ve q. Based on the discussion earlier, the summary is as follows: Q is -ve pf is leading: a power factor of 1 or unity is the goal of any electric utility company. If less than 1, the utility company has to supply more current to the user for a given amount of power use: this will cause more line losses.