Voltage Tolerance Criteria

1. Gohil Soham H
Voltage Tolerance

2.  Manufacturers of computers and data-
processing equipment do not publish data
information to user of the voltage tolerance
limits for their equipment.
 An agency Information Technology Industry
Council (ITIC) has published guidance for
voltage tolerance.
 x-axis is the time duration in seconds,
 y-axis represents the voltage as a
percentage of the nominal voltage.

3.  The graph contains three regions. The area
within the graph in which equipment operate
satisfactorily.
 The area above the graph is the prohibited
region, in which equipment might result
damage.
 The area below the graph is the region where
the equipment might not function properly
but no damage to the equipment.

5.  Steady-State Tolerance:-
This describes RMS voltage either slowly
varying or is constant. The subject range is
±10% from the nominal voltage.
 Line Voltage Swell:-
This region describes a voltage swell having
an RMS amplitude up to 120% of the nominal
voltage.

6.  Low-Frequency Decaying Ring Wave:-
This region has a decaying transient as
results as connection of PFC capacitors to an
AC distribution system. The frequency of this
transient is 200 Hz to 5 kHz.
 High-Frequency Impulse Ring Wave:-
This region has the transients that occur due
to lightning. The standard is given by
ANSI/IEEE C62.41.

7.  Voltage Sags:-
generally transient that appear due to heavy
load as well as fault occurs in the AC power
distribution system.
Sag is 80% of nominal are assumed to a
duration of to 10 sec and sags to 70% of
nominal are assumed to have a duration to
0.5 sec.

8.  Drop out:-
It is consists both voltage sags and
interruption .It is up to 20msec. transient
occur as faults in the distribution system.
 No Damage Region:-
This region include sags and drop outs.
Voltage level is less than steady state
tolerance, but no damage to equipment.

9.  Prohibited Region:-
 This region includes all swell which crosses
the upper limit of the envelope. ITIC
subjected to such conditions damage might
 The ITIC graph applicable for 120V nominal
obtained from 120V, 120/208V 60hz
systems.