3 Phase AC Motor

Because the internal wiring is different. In star there are in effect √3 x as many windings as in delta, so voltage is √3 higher.

Read this article

Three-Phase Transformers

First define where do you want to measure?. Phase to phase or Phase to netral

This may help

Dear TonyS

Please note that what you have shown in diagram is already shown by mathematically and vectorially in my comments in the previously posted title " Re: Voltage Equation dated 08/03/2011 12:32AM"

You need to refresh your basics from any standard text book/literature on the subject.

You may recall that, in case of STAR ,the line current & phase current are same.But ,the line voltage is \/3 times the phase voltage.

However, in DELTA ,the phase voltage & line voltage are same,where as the line current is \/3 times the phase current.

From above,you can see that,line voltage of STAR is \/3 times that of DELTA ,where as line current of DELTA is \/3 times that of STAR.