ABYC AEMC Chapter 3 Three Phase Exam Questions and Answers With Complete Solution
Compared to traditional US power sources, _____ delivers three times the power with only 1.5 times the conductor material. -ANSWER - three-phase power
In a delta configuration, the phase voltage is _____ the line voltage -ANSWER - equal to
Three-phase power ______ than single-phase power -ANSWER - is more efficient
Proper overcurrent protection for a three-phase motor requires -ANSWER - a triple-pole
breaker
Three-phase induction motors can be damaged by ____ in a three-phase power distribution system. -ANSWER - loss of voltage
In the SO-Hertz world, the Three-Phase _(___) configuration is by far the most frequently used. -ANSWER - wye
Three-Phase is a more efficient use of conductors. Given the same peak voltage between conductors and same current in each conductor, three-phase delivers three times the power with only ___ times the conductor material (three wires instead of two). -ANSWER - 1.5
Normally, the loads are unbalanced in a ______ configuration with a neutral cable connected at that center point where the three phases meet to supply the line to neutral loads. -ANSWER - wye(Y)
Notice that for 208-volt three-phase wye(Y), all three line conductors exhibit ___ volts to
neutral. -ANSWER - 120
The delta configuration has the three phases connected in a triangular configuration. They don't normally have a_______ cable. -ANSWER - neutral
In the delta configuration, the phase voltage is ___ to theline voltage. -ANSWER - equal
A wye configuration, the phase voltage is the _________ divided by root 3 (sqrt(3) = 1. 732). -ANSWER - line voltage A delta configuration does a great job at suppressing _____________, as well as maintaining balanced voltages when load currents are severely unbalanced while using only 3 wires -ANSWER - triplen harmonic magnetizing current
the. total VA rating of a Delta Transformer configuration gets reduced to____% of all 3 units, not 66.7% as intuition suggests. -ANSWER - 57.7
A Y configuration is ideal for connection to ____ ground because of the neutral point symmetry. -ANSWER - earth
Y also provides lower _________ stress, important for high voltages. -ANSWER - insulation
Delta is well suited for ___________ venues. -ANSWER - lower voltage high current
Delta systems are connected as ___________________ (that is, floating ground systems) where the power source and load connections are not referenced to ground. -
ANSWER - isolated ground systems
In a ________________________: phase current, line current, and load current are all the same in each phase. -ANSWER - wye source/load configuration
Line voltage is the voltage measured between any two _______ ________ in a three-
phase circuit. -ANSWER - line conductors
Phase current is the current through any___ component comprising a three-phase source or load. -ANSWER - one
In balanced wye circuits, line voltage is equal to phase voltage times the ____________
while line current is equal to phase current. -ANSWER - square root of 3, (1.732)
In a three-phase delta connection scheme, line voltage is equal to phase voltage but the
current supplied to or taken from each line conductor is 1. 732 times the current through
________. -ANSWER - each phase winding
Some examples of nonlinear loads that can generate _______ are inverters, battery chargers, and VFDs, as well as computers, PL Cs, refrigerators, TVs, and electronic light ballasts, and AC control circuits, to name a few. -ANSWER - harmonics
Current harmonics impact what is known as "power factor" _______. -ANSWER - negatively
Power factor is basically tee ratio between tbe average power of a _____ and tbe average power calculated for a pure resistive load witb equal voltage amplitude (AC peak voltage on the sine wave). -ANSWER - load
Compared to traditional US power sources, _____ delivers three times the power with only 1.5 times the conductor material. -ANSWER - three-phase power
In a delta configuration, the phase voltage is _____ the line voltage -ANSWER - equal to
Three-phase power ______ than single-phase power -ANSWER - is more efficient
Proper overcurrent protection for a three-phase motor requires -ANSWER - a triple-pole
breaker
Three-phase induction motors can be damaged by ____ in a three-phase power distribution system. -ANSWER - loss of voltage
In the SO-Hertz world, the Three-Phase _(___) configuration is by far the most frequently used. -ANSWER - wye
Three-Phase is a more efficient use of conductors. Given the same peak voltage between conductors and same current in each conductor, three-phase delivers three times the power with only ___ times the conductor material (three wires instead of two). -ANSWER - 1.5
Normally, the loads are unbalanced in a ______ configuration with a neutral cable connected at that center point where the three phases meet to supply the line to neutral loads. -ANSWER - wye(Y)
Notice that for 208-volt three-phase wye(Y), all three line conductors exhibit ___ volts to
neutral. -ANSWER - 120
The delta configuration has the three phases connected in a triangular configuration. They don't normally have a_______ cable. -ANSWER - neutral
In the delta configuration, the phase voltage is ___ to theline voltage. -ANSWER - equal
A wye configuration, the phase voltage is the _________ divided by root 3 (sqrt(3) = 1. 732). -ANSWER - line voltage A delta configuration does a great job at suppressing _____________, as well as maintaining balanced voltages when load currents are severely unbalanced while using only 3 wires -ANSWER - triplen harmonic magnetizing current
the. total VA rating of a Delta Transformer configuration gets reduced to____% of all 3 units, not 66.7% as intuition suggests. -ANSWER - 57.7
A Y configuration is ideal for connection to ____ ground because of the neutral point symmetry. -ANSWER - earth
Y also provides lower _________ stress, important for high voltages. -ANSWER - insulation
Delta is well suited for ___________ venues. -ANSWER - lower voltage high current
Delta systems are connected as ___________________ (that is, floating ground systems) where the power source and load connections are not referenced to ground. -
ANSWER - isolated ground systems
In a ________________________: phase current, line current, and load current are all the same in each phase. -ANSWER - wye source/load configuration
Line voltage is the voltage measured between any two _______ ________ in a three-
phase circuit. -ANSWER - line conductors
Phase current is the current through any___ component comprising a three-phase source or load. -ANSWER - one
In balanced wye circuits, line voltage is equal to phase voltage times the ____________
while line current is equal to phase current. -ANSWER - square root of 3, (1.732)
In a three-phase delta connection scheme, line voltage is equal to phase voltage but the
current supplied to or taken from each line conductor is 1. 732 times the current through
________. -ANSWER - each phase winding
Some examples of nonlinear loads that can generate _______ are inverters, battery chargers, and VFDs, as well as computers, PL Cs, refrigerators, TVs, and electronic light ballasts, and AC control circuits, to name a few. -ANSWER - harmonics
Current harmonics impact what is known as "power factor" _______. -ANSWER - negatively
Power factor is basically tee ratio between tbe average power of a _____ and tbe average power calculated for a pure resistive load witb equal voltage amplitude (AC peak voltage on the sine wave). -ANSWER - load
