If we have a three phase circuit, where source voltages are in a delta configuration, like the one in the picture:

enter image description here

What is the difference between phase and line voltages in this case?

When generators are in a wye configuration, we know that line voltages are defined as: \$E_{12}=E_1-E_2\$, but here, line voltages are simply: \$E_1, E_2\$ and \$E_3\$. What are phase voltages then?

  • \$\begingroup\$ There are phase to phase voltages and phase to neutral voltages. In your case it depends where the circuit is grounded, if it is floating then you can't speak about phase to neutral voltage. \$\endgroup\$ – Marko Buršič Sep 4 '16 at 13:38
  • \$\begingroup\$ single phase voltage depends on source or reference. Delta , is a differential between phases, Y is a differential to Neutral. IN both cases , the voltage is sine shifted by 120 deg \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 4 '16 at 14:17
  • \$\begingroup\$ @Marko Buršič wherever there is a wye connected source or load, there is a phase to neutral voltage regardless of whether or not the neutral is grounded. \$\endgroup\$ – Charles Cowie Sep 4 '16 at 14:53

For a delta source or load, the phase voltage is the same as the line voltage. For a wye source or load, the phase voltage is the line-to-neutral voltage. For a delta source or load, the phase current is the current in the line-to-line branch. For a wye source or load, the phase current is the same as the line current. Each source and load has its own phase current definition even if there is only one source and one load as shown. As illustrated by your diagram, a wye load can be connected to a delta source and create its own neutral.


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