in india why 50 hz and 220 volt taken as standard rating for
equipments whereas in US 100hz and 110v is consided as
standard rating.is this method save power.
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Answer Posted / shafeeq
A lot of points are factored when a utility decides to
choose 50 or 60 hertz, sometimes it may even been a
political rather than a technical one. We have seen various
types of wars on measurements types of units used or have
been an interested but an innocent invitee in format wars
in electronics like 8 track v/s cassette, v2000 (an
excellent system) V/s the betamax (also with some notable
features) and the vhs. Now we are also extended into the
video disc formats. However if we were to look closely many
of us will agree that 60hz is a good choice. All inductors
and motors could be smaller, and the benefits will
encompass a wide array of electrical and electronic goods
to which the changes will almost be transparent. But it
should be noted that most critical and large capital
intensive plants and machinery, including certain medical
equipment, will not take too kindly to such a change,
which, besides straying from the critical specs, or worse
still may give up altogether, unless expensive time
consuming replacement or an equally complicated and
efficient cycle converter is installed before the system is
connected to the mains.
As a historical note, 60Hz was originally chosen in the US
to help market AC power systems to customers. The ploy was
that a clock could run using a synchronous AC motor and at
60Hz, the gear mechanism would be greatly simplified. Then
the job of keeping accurate time fell to the electricity
company by maintaining a constant frequency. Prior to this,
many different frequencies had been tried.
As regards 50 Hz in India it is descendant of the British
Imperial system. Technically speaking operating 50 Hz
versus 60 Hz would not make much difference but, to achieve
it, either the prime movers - for example steam turbines,
gas turbines and diesel engines - would need to be able to
tolerate a 20% increase in speed or the alternators they
drive - which produce the electricity - would need to be
completely rebuilt with extra poles and windings so that
they could continue to run at the same rotational speed.
The costs of doing such re-engineering would be enormous
and could not be justified as "economically worthwhile"
from the point of view of actual necessity, quite apart
from the severe problems which would be caused to assuring
operational continuity of service whilst such changes were
made.
Further, for any load equipment - machines, appliances,
etc. - that have reactive components
(capacitors/inductors), the effects of a frequency change
from 50 Hz to 60 Hz on such impedances would not be trivial
and would significantly alter their in-circuit behaviour.
This means changes would have to be made to the sizes all
such reactive components to achieve the same effects at the
higher frequency. Doing that would be yet another enormous
cost of conversion from 50 Hz to 60 Hz which could not be
justified as economically worthwhile.
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