I was looking at this problem:

"A balanced delta connected impedance load with (12+j9)Ω per phase is supplied by a balanced three-phase 60 Hz, 208-V source "

I do not wish to ask for help at solving this, rather, I want to know how to interpret the "208 V source" statement. If someone gives me that statement I will immediately think it means
$$ V_{an} = 208 V \angle 0º $$ and we can just get $V_{bn}$ and $V_{cn}$ by adding $\angle +240º$ and $\angle +120º$ respectively.

However I have seen people interpreting this as $ V_{LL} = 208 V$, what reason do they have to conclude it refers to LL and not LN, the problem does not sate it.

  • 1
    $\begingroup$ Normally, unspecified voltage three-phase voltage is considered to be LL. But this depends on individual. $\endgroup$ Nov 30, 2021 at 21:19

1 Answer 1


Note the problem specifies the load is "delta connected". There is no neutral connection to measure phase voltage ($V_{LN}$) against.

Also note the supply frequency is 60 Hz. 208 V is a common line voltage ($V_{LL}$) in the US (which uses a 60 Hz supply), with corresponding phase voltage of 120 V. You are using a US text (Sarma et al, from another post) so you can expect to see examples of US practice.

So the problem is asking about $V_{LL} = 208 V\;$.


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