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1/30/2014 DC Electric Circuit DC Electric Circuits Examples (source: http://hyperphysics.phyastr.gsu.edu/hbase/electric/dcex.html) Multisim Circuit Simulation DC Circuit Construction, PhET Interactive Simulations, 1 http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc Electric Power DC Electric Power = Voltage * Current P = V * I = (joules/coulomb)*(coulomb/sec) = joules/sec = watts Ohm’s Law: V = I * R P = V * I = (I*R)*I = I2*R P = V * I = V * (V/R) = V2/R Other References Electric Power – HyperPhysics, http://hyperphysics.phyastr.gsu.edu/hbase/electric/elepow.html 2 1 1/30/2014 A DC Relay Circuit with R, L and C . • DC Circuit • DC Power Supply V (volts), Resistor R (Ohms, mΩ, kΩ, MΩ, etc), Inductor L (Henry, mH, μH), Capacitor C (Farad, μF, nF, pF) • Circuit Configuration L • Relay coil: L and R --- in series 158.9mH E 12 V • 12V DC coil: R • Calculated current 64.9 mA • Measured current 64.x … 59.x mA C 330µF 25V 185Ω • Contact • 120V, 1/6 HP • 240V, 1/3 HP Relay • Normally Open (NO) contact • Normally Closed (NC) contact • C in parallel with the relay coil DC 12V, AC 120V 1/6 HP, 240V 1/3 HP 3 FIGURE 2-2 Waveforms for the voltage and current represented by equation 2.3. % sinewave2.m Vm = 170; Vrms = Vm/sqrt(2); f = 60; T = 1/f; dt = T/100; t = 0: dt: 2*T; w = 2*pi*f; vt = Vm*sin(w*t); Im = 30; Irms = Im/sqrt(2); theta = pi/6; it = Im * sin(w*t - theta); plot(t, vt, t, it), grid on xlabel('Time sec'), ylabel('Volt/Ampere'); 200 150 100 50 0 -50 -100 -150 -200 0 0.005 0.01 0.015E. 0.02 Timothy L. Skvarenina and William Time sec DeWitt Electrical Power and Controls, 2e 0.025 0.03 0.035 4 Copyright ©2005 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. 2 1/30/2014 Example 2-1 Phasor Doagram FIGURE 2-3 reference. Phasor diagrams for the voltage and current of Example 2-1; (a) voltage as reference, (b) current as reference, (c) cos(t) as 170 sin 30 sin Timothy L. Skvarenina and William E. DeWitt Electrical Power and Controls, 2e 120 2 sin( 21.21 2 sin( 5 Copyright ©2005 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. 3