MV design guide - Schneider Electric

Standards
IEC - ANSI comparison
Peak value of short-time current
and closing capacity
According to IEC
c The peak value of short-time withstand current is equal to:
v 2.5•Isc at 50 Hz
v 2.6•Isc at 60 Hz
v 2.7•Isc for special cases.
According to ANSI
c The peak value of short-time withstand current is equal to:
v 2.7 K Isc at peak value
v 1.6 K Isc at rms. value.
(K : voltage factor)
Rated short-circuit duration
According to IEC
c The rated short-circuit duration is equal to 1 or 3 seconds.
According to ANSI
c The rated short-circuit duration is equal to 3 seconds.
Rated supply voltage
for closing and opening
devices and auxiliary circuits
According to IEC
c Supply voltage values for auxiliary circuits:
v for direct current (dc): 24 - 48 - 60 - 110 or 125 - 220 or 250 volts
v for alternating current (ac): 120 - 220 - 230 - 240 volts.
c Operating voltages must fall within the following ranges:
v Motor and closing release units:
-15% to +10% of Ur in dc et ac
v opening release units:
-15% to +10% of Ur in ac; -30% to +10% of Ur in dc
v undervoltage opening release units
the release unit gives
the command and
forbids closing
0 % 35 % 70 % 100 %
According to ANSI
c Supply voltage values for auxiliary circuits:
v for direct current (dc): 24 - 48 - 125 - 250 volts.
v for alternating (ac): 120 - 240 volts
the release unit
must not have
an action
(at 85%, the release unit must enable
the device to close)
U
74 Merlin Gerin MV Design Guide Schneider Electric