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## Main Question or Discussion Point

Hello, I would like someone to give me some help or clarification relating to the conversion from a delta to star source. I understand that in star, Line Voltage is sqrt(3) times the phase voltage, and line voltage also leads phase by 30°. I also understand that Line and Phase currents are the same too. In Delta, I understand that Line and Phase Voltages are the same, and that Line Currents are sqrt(3) times the phase Currents, but LAG Phase currents by 30°. My issue seems to be relating to the time when converting a delta source to a star source is required. What I am not sure about is what to take as reference? If you start with a Delta Source and convert to Star, do you take the Delta Voltage as reference, and then divide by sqrt(3) and subtract 30° to get the equivalent star phase voltage, or do you say that the delta voltage is the same as the star phase voltage (in terms of angle and magnitude) and then multiply by sqrt(3) and add 30° to get the equivalent star line voltage.

Also, when converting from delta to star, do you make the initial delta voltages to be at 30°, so that when you divide by sqrt(3) and subtract 30° to get the equivalent star phase voltage this will be at 0 degrees?, or do you take the voltages in the initial delta source to be at 0°?

E.g., should the conversion be undertaken as below if the delta voltages are 415V, as there are several ways of doing this, depending on what is taken as the reference (0° angle) (Vp = Phase Voltage and Vl = Line Voltage)

If Delta VL = 415V@30° → Star Vp = 415/√3 @ 0° & Star VL = 415V@30°

Or

Delta VL = 415V@0° → Star Vp = 415/√3 @ -30 & Star VL = 415V@ 0°

or

Delta VL = 415V@0° → Star Vp = 415V@0° & Star VL = √3 * 415V @ 30°

I'm really sorry if this has confused anyone but I would appreciate some help as this should be so simple and is really bugging me. I'm not sure whether I'm making a mountain out of a molehill here or whether I have missed something really obvious, its the fact that our lecturer said it doesn't matter what is taken as reference, although surely this would knock everything out by 30° if true?

Thanks

Also, when converting from delta to star, do you make the initial delta voltages to be at 30°, so that when you divide by sqrt(3) and subtract 30° to get the equivalent star phase voltage this will be at 0 degrees?, or do you take the voltages in the initial delta source to be at 0°?

E.g., should the conversion be undertaken as below if the delta voltages are 415V, as there are several ways of doing this, depending on what is taken as the reference (0° angle) (Vp = Phase Voltage and Vl = Line Voltage)

If Delta VL = 415V@30° → Star Vp = 415/√3 @ 0° & Star VL = 415V@30°

Or

Delta VL = 415V@0° → Star Vp = 415/√3 @ -30 & Star VL = 415V@ 0°

or

Delta VL = 415V@0° → Star Vp = 415V@0° & Star VL = √3 * 415V @ 30°

I'm really sorry if this has confused anyone but I would appreciate some help as this should be so simple and is really bugging me. I'm not sure whether I'm making a mountain out of a molehill here or whether I have missed something really obvious, its the fact that our lecturer said it doesn't matter what is taken as reference, although surely this would knock everything out by 30° if true?

Thanks