Answer / hassan

In 3 phase (RYB) one Phase remain zero other one positive and one negative. if we draw 3 phase (wave)diagram .
so voltage is 440 not 690
V+0+(-V)= 2V
0+V+(-V)=2V and v=240
(-V)= V because it is magnitude
similarly
8 combination

Answer / paul jeffery

Some countries (E,G. Sweden) and processes (E.G. Paper pulp) do use 690 V line to line systems (400 V line to neutral)and transform to 690 v from 11 kv. Wind farms often generate at 690 v and step up to 11 kv to synchronise with the grid. 690 v reduces cable sizes and cost vs 400-440 v systems and enables much larger motors to be DOL started - up to 600 kw plus compared to 200 kw plus for 400 v units. A 400 delta connected motor will operate at 690 v when star connected. These are the basics but 690 v has many advantages over 400 v.

Answer / shrawan

Shashank, your answer seems to be a best answer but kindly
eleborate the thing star delta connections.

after that we can unsderstand properly...
Waiting your reply..

Answer / shashank

Normally in india and some other countries the normal
single phase voltage used is 240 V & 415 V for 3 phase.
When we say single phase the voltage is considered with
ref. to earth i.e. zero potential, hence the volt meter is
connected in between the phase and the earth. (This voltage
can also be measured between the line terminal and its star
point in a balanced STAR connected system with line voltage
of 415 V)
Similarly when the voltmeter is connected between two line
terminals, we get the line voltage (for star system, the
line voltage = phase voltage * SQRT(3); where as for delta
connected system Line Voltage = Phase voltage.)
- Why line voltage cannot be 690 V?
The ans is simple, as nobody uses a single phase supply of
400 V AC, 690 V line voltage does not exists.

Answer / guest

the phase difference between two phase are 415 V In steed of
three phase& also phase angle are 120 degree there fore 690 v
are not measured

Answer / sks

Because of 50 Hz frequency & RYB phases are rotating at the
phase sequence of 120 degree electrical.

Answer / shoaib9786

When you use the word three phase, it does not mean you are
connecting the voltmeter across all the three phases
(R,Y,B). The voltmeter is connected just across 2 phases,
so the line voltage across it is 440 or 415 volt. Hope that
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