Siemens SIRIUS 3RH Series, Системное руководство

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SIRIUS 3RU2/3RB3 overload relays
5.4 Functions
SIRIUS Innovations
496
System Manual, 01/2011, A8E56203870002-03
5.4.1.4 Tripping characteristics
Introduction
The tripping characteristic curves map the relationship between tripping time and tripping
current as a multiple of the current setting I
e
; they are specified for symmetrical 3-pole and
for 2-pole loading from cold.
The lowest current at which tripping will occur is known as the minimum tripping current.
According to IEC/EN 60947-4-1/VDE 0660 Part 102, this current has to lie within specific
defined limits.
The limits for the total tripping current in the case of 3RU21/3RB30/3RB31 overload relays
with symmetrical 3-pole loading are between 105 and 120 % of the current setting.
Tripping characteristics
The limit tripping current determines the progression of the tripping characteristic curve up to
higher tripping currents based on the characteristics of the tripping classes (CLASS 10,
CLASS 20 etc., see the chapter titled Tripping classes (Page 495)).
The tripping classes describe time intervals within which the overload relays have to trip in
the case of a symmetrical, 3-pole load from the cold state with 7.2 times the current setting
I
e
.