Answer / vivek sharma

When an alternator generates voltage, its rms value is given
by 4.4*f*$*t, where $ is value of total flux per pole. So we
can see all the voltages are made inevitably multiple of
this value (1.1, which is the form factor of ac wave). also
it provides us the best economic construction of step up and
step down transformers.

Answer / vipul tayal

we always use a multiple of 1.11 bcoz for a pure sine wave
the FORM FACTOR is the ratio of rms value of voltage or
current with the avg. value of voltage or current and for
pure sine wave rms value of current is Imax/root '2' and
avg. value is 2Imax/pie. and which comes out to be 1.11 so
we cant have a combination of other then a multiple of 1.11.

Answer / selvaraj

Mr Vivek's answer is the best considering the last
statement.It has got nothing to do with form factor etc.,
Internationaly we use different voltage level.This decided
mostly by users and market availability.

Answer / sagar khandey

When an alternator generates voltage, we always use a
multiple of 1.11 because for a pure sine wave the FORM
FACTOR is the ratio of rms value of voltage or current with
the avg. value of voltage or current and for pure sine wave
rms value of current is Imax/root '2' and avg. value is
2Imax/pie and which comes out to be 1.1;

We can't have a combination of other then a multiple of 1.11*.
So we can see all the voltages are made inevitably multiple
of this value (1.1, which is the form factor of ac wave).

Also it provides us the best economic construction of step
up and step down transformers.


In the case of a Square Wave ie. a digital wave, the RMS and
the average value are equal; therefore, the form factor is 1.

Answer / prashant

these 11,22,33,66,110 figures are rms values

generated voltage = V (avg value)

then max value (3.14/2)V

rms value is {1/sqrt(2)}*max. value
=.707*1.57=1.11

Answer / gowrish

mr. sagar is correct.. Because of Form Factor.

Answer / hiresh

In Indonesia it is 70 KV and 12 KV

Answer / paveen

bcoz it should be in the multiples of 11.......

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