EEE360 Midterm 1
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED PASS
Balanced Three Phase Systems - CORRECT ANSWER-each voltage source has the same
magnitude (Vm) and frequency(w), each is 120 degrees out of phase with the other two
-Van(t)=Vm cos(wt)
-Vbn(t)=Vm cos(wt-120)
-Vcn(t)=Vm cos(wt-240)
Balanced Three Phase Circuit - CORRECT ANSWER-loads are such that the currents produced by
the voltages are also balanced
-ia(t)=Im cos(wt-theta)
-ib(t)=Im cos(wt-theta-120)
-ic(t)=Im cos(wt-theta-240)
Instantaneous Power in Balanced 3Phase - CORRECT ANSWER-3Vrms Irms cos (theta).
constant over time
, Complex Power in Balanced 3Phase - CORRECT ANSWER-3x the complex power of any of the
phases. 3S>
Three Phase Power measurement - CORRECT ANSWER-analog wattmeter
-current input is connected in series with the load
-voltage input is in parallel with the supply or load
-wattmeter provides a measurement of the average power (P)
-Voltmeter(parallel) and Ammeter(series) used with wattmeter to determine rms values
-microprocessor calculates rms values
-instantaneous readings multiplied to get instantaneous power (p(t))
-average value of p(t) gives real power
-permits calculation of pf and apparent power (lS>l)
-pf= P/lS>l
Four Wire System - CORRECT ANSWER-the loads can be connected between the phase
conductors and the neutral
-for unbalanced loading, the measurement requires three wattmeters to measure each phase
separately
-Pt=Pa+Pb+Pc
-three wattmeters
Three Wire System - CORRECT ANSWER-the wiring system used at present for safety reasons,
with live, neutral, and ground wires
-the sum of the three line currents is zero
-two wattmeters
Capacitive reactive power [negative] equation - CORRECT ANSWER-S_C = V_C x I*
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED PASS
Balanced Three Phase Systems - CORRECT ANSWER-each voltage source has the same
magnitude (Vm) and frequency(w), each is 120 degrees out of phase with the other two
-Van(t)=Vm cos(wt)
-Vbn(t)=Vm cos(wt-120)
-Vcn(t)=Vm cos(wt-240)
Balanced Three Phase Circuit - CORRECT ANSWER-loads are such that the currents produced by
the voltages are also balanced
-ia(t)=Im cos(wt-theta)
-ib(t)=Im cos(wt-theta-120)
-ic(t)=Im cos(wt-theta-240)
Instantaneous Power in Balanced 3Phase - CORRECT ANSWER-3Vrms Irms cos (theta).
constant over time
, Complex Power in Balanced 3Phase - CORRECT ANSWER-3x the complex power of any of the
phases. 3S>
Three Phase Power measurement - CORRECT ANSWER-analog wattmeter
-current input is connected in series with the load
-voltage input is in parallel with the supply or load
-wattmeter provides a measurement of the average power (P)
-Voltmeter(parallel) and Ammeter(series) used with wattmeter to determine rms values
-microprocessor calculates rms values
-instantaneous readings multiplied to get instantaneous power (p(t))
-average value of p(t) gives real power
-permits calculation of pf and apparent power (lS>l)
-pf= P/lS>l
Four Wire System - CORRECT ANSWER-the loads can be connected between the phase
conductors and the neutral
-for unbalanced loading, the measurement requires three wattmeters to measure each phase
separately
-Pt=Pa+Pb+Pc
-three wattmeters
Three Wire System - CORRECT ANSWER-the wiring system used at present for safety reasons,
with live, neutral, and ground wires
-the sum of the three line currents is zero
-two wattmeters
Capacitive reactive power [negative] equation - CORRECT ANSWER-S_C = V_C x I*
