Topic 1 - ECE341 Energy Conversion(Spring 2011 Topic 1 Ac power and three phase concepts Ac power phasor power factor Active and reactive power

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1 J. Wang 4/3/2011 1 Topic 1: Ac power and three phase concepts ECE341 Energy Conversion (Spring 2011) s Ac power, phasor, power factor s Active and reactive power s Capacitor vs. Inductor s Why three phase s Wye and Delta connection s Per phase analysis s Unbalanced three phase Facts J. Wang 4/3/2011 2 Ohio’s “renewable portfolio standard,” which originated in the Republican-led state Senate in 2008, requires that 25 percent of Ohio’s energy come from renewable sources by 2025 , and that half of that renewable portion be created in-state. Its passage — along with grants from a state program known as the Ohio Advanced Energy Fund — essentially jump-started an alternative energy industry in the state. Already, the impact is visible across Ohio. Farmers, homeowners and small companies put up solar panels and wind turbines; several large-scale renewable projects, including a 12-megawatt solar field in northern Ohio and planning for a 50-megawatt field in the southeast, got underway ; wind companies moved ahead with plans for five new wind farms around the state and five turbines in Lake Erie ; hundreds of companies either started up or got involved in the manufacturing supply chain for renewable energy; the city of Toledo emerged as a hub for research and manufacturing of thin-film solar cells.
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2 Notation - Power J. Wang 4/3/2011 3 • Power: Instantaneous consumption of energy • Power Units Watts = voltage x current for dc (W) kW 1 x 10 3 Watt MW 1 x 10 6 Watt GW 1 x 10 9 Watt • Installed U.S. generation capacity is about 900 GW ( about 3 kW per person) Notation - Energy J. Wang 4/3/2011 4 • Energy: Integration of power over time; energy is what people really want from a power system • Energy Units Joule = 1 Watt-second (J) kWh = Kilowatthour (3.6 x 10 6 J) Btu = 1055 J; 1 MBtu=0.292 MWh; 1MWh=3.4MBtu – One gallon of gas has about 0.125 MBtu (36.5 kWh); one gallon ethanol as about 0.084 Mbtu (2/3 that of gas) • U.S. electric energy consumption is about 3600 billion kWh (about 13,333 kWh per person)
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3 Symbols in the Ac Circuits J. Wang 4/3/2011 5 t ϖ sin 2 100 Phase Angles in Ac circuits J. Wang 4/3/2011 6 • Angles need to be measured with respect to a reference - depends on where we define t=0 • When comparing signals, we define t=0 once and measure every other signal with respect to that reference • Choice of reference is arbitrary – the relative phase shift is what matters • Relative phase shift between signals is independent of where we define t=0
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4 Example: Phase Angle Reference J. Wang 4/3/2011 7 Pick the bottom wave as the reference 1 sin 4 v V t π ϖ = + ( 29 2 sin 0 v V t = + ( 29 1 sin 0 v V t = + 2 sin 4 v V t = - 1 2 4 θ - = 1 2 4 - = Or pick the top as the reference- it does not matter!
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This note was uploaded on 04/01/2012 for the course ECE 341 taught by Professor Keyhani during the Fall '08 term at Ohio State.

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Topic 1 - ECE341 Energy Conversion(Spring 2011 Topic 1 Ac power and three phase concepts Ac power phasor power factor Active and reactive power

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