The Y Connections
- each phase is connected between a line and the neutral.
Phase Voltage = Line to neutral voltage(Va, etc.).
Phase Currents = Line currents(Ia, etc.).
Neutrals Connect the 3 phases.
The Delta Connections
- each phase is connected in two lines.
Phase Voltage = Line voltages(Vab, etc.).
Phase Currents = Currents from line to line(Iab, etc.).
Neutral is not present.
Definition of the following:
Phase - it is simply the branch of the circuit.
Line - wires that connect the source to the load.
Neutral - the 4th wire in the three phase system. It's where the phases of a Y connection come together.
Line Currents - the current flowing in each of the lines(Ia, Ib, Ic).
Line Voltage - the voltage between any two of the lines(Vab, Vbc, Vac).
Phase Currents & Voltages - the voltages and currents across and through a single branch (phase) of the
circuit. It depends on whether the connection is Wye or Delta!
Y connected source
Y connected source
Delta connected source
Y connected load
Delta connected load
Reminders:
- All 3 variables have the same amplitude
- All 3 variables have the same frequency
- All 3 variables are 120o in phase
- All 3 sources are represented by a set of balanced 3-phase variables
- All loads are 3-phase with equal impedance's
- Line impedance are equal in all 3 phases
Balanced 3-phase circuit:
