EEE360 Three Phase Circuits
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED
PASS
Polyphase Systems - CORRECT ANSWER-Tried (6 and 12 phase) have been tried but proved
uneconomical
-used for large rectifiers
Major Advantage - CORRECT ANSWER-efficiency of power transmission, generation of constant
torque which reduces vibration for rotating machines
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
QUESTIONS AND VERIFIED
CORRECT ANSWERS
GRADED A+ [LATEST] 100%
GUARANTEED
PASS
Polyphase Systems - CORRECT ANSWER-Tried (6 and 12 phase) have been tried but proved
uneconomical
-used for large rectifiers
Major Advantage - CORRECT ANSWER-efficiency of power transmission, generation of constant
torque which reduces vibration for rotating machines
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
