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2010 CA08103002Z-EN
www.eaton.com18/88 IZM circuit-breakers, IN switch-disconnectors
IZM26 tripping characteristics
IZM26 trippingcharacteristics
1 The trip unit has a thermal memory, which can shorten the tripping time in
the overload range.
This function plays a role whenever a current is higher than the overload
release’s tripping time and which is then isolated by a downstream
circuit-breaker or the circuit-breaker itself. On a subsequent overload
current the circuit-breaker will trip more quickly than normal.
The reduced tripping time is inversely proportional to the time expired
since the last overload. After about five minutes the thermal memory is
reset.
2 The overload release is activated at a pick-up time of 110 % I
r
with a
tolerance of ±5 % (indicated by the lit “Unit Status” LED).
3 The characteristic curves apply to applications in a temperature range
from -20 °C to +55 °C. Temperatures over +85 °C cause automatic tripping.
The circuit-breaker must be selected according to the temperature-
dependent derating values from the table in the technical data.
4 The end of the characteristic curve is determined by the type of
application and the switching capacity of the selected circuit-breaker.
5 The non-delayed short-circuit release is activated at a response value of
conventionally 100 % with a tolerance of ±10 %.
6 The listed overall switch-off times include the response times of the trip
unit, the opening times of the switch and the time required to switch off
the current.
7 Additional setting “max M1”:
IZM20
M1 = 14 × I
n
for nominal currents of 200 A to 1250 A
M1 = 12 × I
n
for nominal currents of 1600 A to 2000 A
IZM32
M1 = 14 × I
n
for nominal currents of 200 A to 1250 A
M1 = 12 × I
n
for nominal currents of 1600 A to 2500 A
M1 = 10 × I
n
for nominal currents of 3200 A
IZM40
M1 = 12 × I
n
for nominal currents of 4000 A
IZM63
M1 = 14 × I
n
for nominal currents of 2000 A to 2500 A
M1 = 12 × I
n
for nominal currents of 3200 A to 5000 A
M1 = 10 × I
n
for nominal currents of 6300 A
8 The overload release trips at 110 % I
r
with a tolerance of ±5 %
(indicated by the “Unit Status” LED).
The short-time delayed short-circuit release I
sd
is activated at a pick-up
time of conventionally 100 % with a tolerance of ±5 %.
9 When zone selectivity (ZSI) is activated in the short-time delayed short-
circuit release and no blocking signal is applied, the minimum time value
(0.10 s) applies irrespective of the short-time delay settings.
10 The upper lines of the I²t characteristic curves are horizontal from a value
of 8 × I
r
(indicated by the points).
11 IZM circuit-breakers32 feature an additional, permanently set non-
delayed short-circuit release, which is set to a peak value of 170 kA
with a tolerance of ±10 %.
This protective function remains active when the non-delayed
short-circuit release is switched off.
12 The listed overall switch-off times are conservative and take into account
the trip unit’s maximum response times, the circuit-breaker’s maximum
opening delays and the longest current interruption times with regard to
factors that contribute to worst-case conditions, such as maximum rated
operational voltage, single-phase interruptions and minimum power
factor.
Fast disconnecting times are possible but depend on the system
conditions and the circuit-breaker model.
13 The ground-fault release is activated at a response value of
conventionally 100 % with a tolerance of ±10 %.
14 Unless otherwise specified, the current value tolerances are ±10 %
of the values shown in the diagram.
15 In combination with ARMS function, ground-fault protection is limited
to 1200 A.
16 When zone selectivity (ZSI) is activated in ground-fault protection and no
blocking signal is applied, the minimum time value (flat characteristic
curve) applies irrespective of the settings.
17 The upper lines of the I²t characteristic curves are horizontal from a value
of 0.625 × I
n
(indicated by the points).
18 The maintenance mode function must be activated with a switch or
through the communications terminals for these characteristic curves
to apply. A blue LED indicates that the maintenance mode settings are
active.
19 The shown switch-off times apply for connection to an additional auxiliary
power supply.
20 Tripping by the Maintenance Mode Trip is indicated by the non-delayed
short-circuit protection LED.
21 The nominal reduction values (response values), with a tolerance
of ±15 % are:
2.5 x I
n
(= R5), 4 x I
n
(= R4), 6 x I
n
(= R3), 8 x I
n
(= R2), 10 x I
n
(= R1)
22 This characteristic curve is shown as a multiple of the overload release
setting I
r
. The overload release trips at 110 % Ir with a tolerance of ±5 %
(indicated by the “Unit Status” LED).
23 The delayed short-circuit release I
sd
also has an “M1” setting, which may
increase the response threshold when I
sd
is active (at the curves’ point of
overlap).
24 The delayed short-circuit release I
sd
trips at 100 %, with a tolerance
of ±5 %.
25 Delay tolerances in the area of the flat characteristic curve:
The tolerance is +0/-80 ms of the set values, with the following exceptions:
At 100 ms the tolerance is 6 to 13 ms
At 150 ms the tolerance is 10 to 17 ms
At 200 ms the tolerance is 15 to 22 ms
26 I
2
t-function
The upper lines of the I
2
t characteristic curves are horizontal from a value
of 8 × I
r
(for ground-fault protection 0.625 × I
n
), the lower limit value of the
band following the line.
The characteristic curve has a tolerance of +0/-30 % for all settings
except the following ones:
For 0.10 s +30 %/-25 %
For 0.15 s +20 %/-25 %
For 0.20 s +10 %/-25 %
For all characteristic curves the lower, minimum time value, which
merges with the I
2
t line, determines the break point and the shape of the
upper characteristic curve.
27 In the time range ≦ 0.5 s the I
4
t characteristic curve becomes horizontal.
Tripping does not take place faster than the set short-time delay t
sd
.
(In the drawing a displacement of the characteristic curve is avoided.)
28 This characteristic curve is shown as a multiple of the overload release
setting I
r
.
This so-called “E-/IEC-... inverse” characteristic curve results from the
time setting “TimeDial” in combination with the delayed short-circuit
release I
sd
and the delay t
sd
(shown as thick lines). The non-delayed
short-circuit release I
i
, shown as a separate characteristic curve, can be
disabled (Off position).
IZM26...A(V)(U)(P)...