Siemens SIRIUS 3RH Series, System Manual

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SIRIUS 3RV2 motor starter protectors
4.4 Functions
SIRIUS Innovations
388
System Manual, 01/2011, A8E56203870002-03
4.4.1.2 Tripping characteristics
The time-current characteristic, the current-limiting characteristics, and the I
2
t characteristics
have been determined according to DIN VDE 0660/IEC 60947.
In the case of the time-current characteristic, the tripping characteristic of the inverse-time
delayed overload release (thermal overload release) applies for direct current and alternating
current with frequencies from 0 Hz up to 400 Hz.
The characteristics apply to the cold state; at operating temperature, the tripping times of the
thermal releases drop to approximately 25%.
In normal operation the device must be loaded at 3 poles. You are recommended to switch
all 3 main current paths in series to protect single-phase or DC loads.
With both 2- and 3-pole loading, the maximum deviation of the tripping times at and above 3
times the current setting is ± 20% and thus meets the requirements of DIN VDE 0165.
The tripping characteristics for the instantaneous, electromagnetic overcurrent releases
(short-circuit releases, 'n' releases) are based on the rated current I
n
that is also the upper
value of the setting range for motor starter protectors with adjustable overcurrent releases. If
the current is set to a lower value the tripping current of the 'n' release is increased by a
correspondingly higher multiple.
Frequency dependence of the short-circuit release
The characteristics of the electromagnetic overcurrent release apply for frequencies of
50 Hz/60 Hz. For lower frequencies up to 16 2/3 Hz, for higher frequencies up to 400 Hz,
and for direct current, correction factors have to be taken into account accordingly.
The following characteristic curve shows the frequency dependence of the short-circuit
release.
40
30
20
10
0
-10
-20
-30
0 50
100
200 250 300 350 400 150
,>@
I>+]@
Δ I Change in operating current
f Frequency