NAPIT Certification Scheme napit three phase question didnt know

[lukesparky123]

Hi there just had a napit inspection and got caught out on one of the questions i was asked (didnt look good !!) the guy asked me "why is it between L / N you get 230v but between L1 / L2 you get 400v. I have no experience with three phase and could not remeber from college he also wouldnt tell me !! told me to look it up !
please can anybody jog my memory.
thanks alot luke

 

[telectrix]

its just how 3 phase is. if you imagine a mercedes-benz badge, each point is the L1,L2,L3 red phase, yellow phase, blue phase ( or as it is now Brown, black,grey. the center point is the neutral (Blue). that is a star configuration. each phase is 120deg. behind the other ( in time) . so, the actual single phase voltage e.g.L1/N is 230, and the voltage between any " live " phase and another is 400. the phase/phase voltage is √3 x 230 =400

 

[pmac10]

or draw a sinewave,230v either side of 0. now draw 3 sinewaves 120degrees apart on the same graph. the value measured from the positive peak of the first wave (L1), to the negative point of the second (L2), bout 400v, and the same if you measures to the third (L3), but if you measursed from the 0 line, 230v.