SIEMENS
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Siemens IC 10 · 2017
Overload Relays
SIRIUS 3RB3 Electronic Overload Relays
3RB30, 3RB31 for standard applications
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SIRIUS 3RB3133-4.B0 electronic overload relay
The 3RB30/3RB31 electronic overload relays up to 115 A with
internal power supply have been designed for current-depen-
dent protection of loads with normal and heavy starting, and to
protect against excessive temperature rises due to overload,
phase asymmetry or phase failure. An overload, phase asymme-
try or phase failure result in an increase of the motor current be-
yond the set rated motor current. This current rise is detected by
the current transformers integrated into the devices and evalu-
ated by corresponding solid-state circuits which then output a
pulse to the auxiliary contacts. The auxiliary contacts then switch
off the load by means of a contactor. The break time depends on
the ratio between the tripping current and the current setting
I
e
and is stored in the form of a long-term stable tripping charac-
teristic curve,
(see Characteristic curves)
.
In addition to inverse-time delayed protection of loads against
excessive temperature rises due to overload, phase asymmetry
and phase failure, the 3RB31 electronic overload relays also
allow internal ground-fault detection (not possible in conjunction
with contactor assemblies for wye-delta starting). This provides
protection of loads against high-resistance short circuits due to
damage to the insulation material, moisture, condensed water
etc.
The "tripped" status is signaled by means of a switch position
indicator. The relay is reset manually or automatically after the
recovery time has elapsed.
The 3RB3 electronic overload relays are suitable for operation
with frequency converters.
The devices are manufactured in accordance with environmen-
tal guidelines and contain environmentally friendly and reusable
materials. They comply with all important worldwide standards
and approvals.
3RB20 and 3RB21 overload relays in sizes S6 to S10/S12,
see
page 7/109 onwards.
Use in hazardous areas
The 3RB30/3RB31 electronic overload relays are suitable for the
overload protection of motors with the following types of
protection:
•
II (2) G [Ex e] [Ex d] [Ex px]
•
II (2) D [Ex t] [Ex p]
EC type test certificate for Group II, Category (2) G/D exists. It
has the number PTB 09 ATEX 3001.
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4
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2
A sealable transparent cover can be optionally mounted
(accessory). It secures the motor current setting against adjustment.
Connection for mounting onto contactors:
Optimally adapted in electrical, mechanical and design terms to the
contactors 3RT2. The overload relay can be connected directly
using these connection pins. Stand-alone installation is possible as
an alternative (in conjunction with a terminal support for
stand-alone installation).
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Selector switch for manual/automatic RESET:
With the slide switch you can choose between manual and automatic
RESET.
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Indicates a trip and enables the wiring test.
Switch position indicator and TEST function of the wiring:
1
Solid-state test (device test):
Enables a test of all important device components and functions.
3
Motor current setting:
Setting the device to the rated motor current is easy with the large
rotary knob.
6
Trip class setting/internal ground-fault detection (only 3RB31):
Using the rotary switch you can set the required trip class and
activate the internal ground-fault detection dependent on the
start-up conditions.
2
Connecting terminals (removable joint block for auxiliary circuits):
Depending on the device version, the terminals for screw and
spring-type connection are configured for the main and auxiliary
circuit.
4
A device set to manual RESET can be reset locally by pressing the
RESET button. On 3RB31 overload relays an electrical remote
RESET is integrated.
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IC01_00406
© Siemens AG 2016