For a single phase system,the voltage between the live wire and the neutral wire is called as the phase voltage.In case of three phase system,the voltage between one phase out of any of the three phases and the neutral point or neutral wire is called as phase voltage.
Line voltage is the voltage between any two phases out of the three phases and depending upon the type of connection the line voltage will vary. It will be easy for you if you see the pictures below:
Above content originals from https://www.quora.com/What-is-the-difference-between-phase-and-line-voltage , hope it can help generator newbie to better understand generator technical specifications.
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