Three-Phase Wye Connection Flashcards
What is a phase voltage?
The Voltage, produced or dropped by one line to neutral in a wye, or from line to line in a delta connected alternator, transformer or load.
What is Line Voltage?
The Voltage, produced or dropped line to line in a wye, or from line to line in a delta connected alternator, transformer or load.
What does E represent?
A source voltage;
Generally depicted as a ‘volt rise’.
Should a phasor diagram of a wye connected load contain line voltages?
Yes, it should contain both line and phase voltage.
In a balanced wye circuit what is the time displacement between ENA and ENC?
120 electrical degrees.
How is line voltage in a wye circuit calculated?
By adding phasors of the voltage of one phase to neutral and the voltage of the other phase, from neutral;
This gives, VL = VPH • 31/2.
In a balanced wye system, what is the time displacement between VAB and VAN?
VAN Lags VAB by 30º.
What makes a balanced wye circuit?
When each phase impedance and power factor are identical.
Why are phase current and line current equal in a wye connected system?
Because there is only one path for current, from phase to neutral.
The phase current will lag/lead phase voltage by __________.
The power factor angle Θ.
If the neutral of an unbalanced wye system was disconnected, how would the voltages behave?
The highest voltage will be dropped by the phase with the largest impedance.
What does a wye neutral do?
It carries the unbalanced load;
It maintains proper voltages across each phase.
When does no current flow in a wye neutral?
When the circuit is balanced.
How is current in the neutral determined?
By taking the phasor sum of the three line currents.
What is the power factor?
The phase angle between phase voltage and phase current.
