EEE 360 Midterm Exam 1 Verified Latest Update

Midterm Exam Study Guide EEE 360 | A+ Rated Study Resource If the power is positive, the element is absorbing or supplying power. - answer - absorbing, like a load If the power is negative, the element is absorbing or supplying power. - answer - supplying, like a generator. The RMS value of v(t) = Vmaxcos(wt + theta) is given by: - answer - Vmax / 2^0.5 For balanced wye-delta loads, Z delta = ? - answer - Z delta = 3Zy For delta transformers, Vphase = ? - answer - V line to line. There is no neutral In wye circuits, Phase = ? - answer - V line to neutral voltage Step-down transformers - answer - Wye-delta transformers are frequently used as this. current magnitude - answer - I_M = rad(2)I_rms Complex Power (VA) - answer - S = V_rms x I*_rms; S = P + jQ the rating of power equipment is described by the apparent power, S, also measured in volt-amperes P = real power Q = reactive power In this circuit, the current lags the applied voltage - answer - inductive In this circuit, the current leads the applied voltage - answer - capacitive Resistor real power equation - answer - S_R = V_R x I* Capacitive reactive power [negative] equation - answer - S_C = V_C x I* Voltage source complex power equation - answer - S_S = V_S x I* Voltage regulation - answer - The difference between the magnitudes of the voltage at the load terminals for the no-load (V_no-load) and (full) load conditions divided by the load voltage (V_load) magnitude Voltage regulation generalizations - answer - Typically, the voltage regulation should be less than 10%. Overvoltage in no-load condition must be less than 5%. The voltage drop in full load condition should not be more than -5%. Loads - answer - Are represented by an impedance Z = V_load / I_load = R + jX Lagging - answer - The phase angle is positive if the load power factor is? Leading - answer - The phase angle is negative is the load power factor is? Low power factor - answer - This requires more rms current for the same load power which results in greater utility transmission losses in the power lines. S_load = V_load x I*_load = V_load x I_load x e^(+-jtheta_load) : (+) sign is used if the pf is? - answer - Lagging S_load = V_load x I*_load = V_load x I_load x e^(+-jtheta_load) : (-) sign is used if the pf is? - answer - Leading power factor is lagging if circuit is - answer - inductive power factor is leading if circuit is - answer - capacitive balanced three-phase system, each voltage source: - answer - has the same magnitude (V_M) and frequency (w), and each is 120 degrees out-of-phase with the other two A balanced three-phase circuit is one in which the loads are such that the _____ produced by the ________ are also balanced. - answer - currents, voltages sum of the balanced voltages and the sum of the balanced currents in a three-phase system - answer - equal zero total instantaneous power equation - answer - p_T(t) = 3V_rms x I_rms cos(theta) The total three-phase complex power is - answer - three times the complex power of any of the phases S_T = S_A + S_B + S_C = 3S_1 phasor voltage expressions of a wye-connected generator - answer - V_an = V_rms angle delta V_bn = V_rms angle delta - 120 degrees V_cn = V_rms angle delta - 240 degrees phase voltage - answer - V_P is the phase voltage magnitude between the phase conductors and neutral and is called the line to neutral voltage in a balanced wye-connected generator, the total phase voltages equal - answer - zero V_an + V_bn + V_cn = 0 Line-to-line voltage equation in balanced wye-connected generator - answer - V_ab = V_an - V_bn In balanced wye-connected generator, V_ab = - answer - V_ab = rad 3 V_an angle 30 degrees In wye-connected generator, line-to-line voltage leads or lags from phase voltage by - answer - leads by 30 degrees V_ab leads the corresponding V_an by 30 degrees The total three-phase complex power is how many times the single-phase power? - answer - Three S_T = 3S_a But the sum of the three ph