Brochure

SIRIUS
Siemens Industry, Inc. Industrial Control Product Catalog 2017
3/18
3
OVERlOAd
RElAYS
Overview
The 3RB and 3RB solid-state overload relays up to 630 A
with internal power supply have been designed for inverse-time
delayed protection of loads with normal and heavy starting
(see Function) against excessive temperature rise due to over-
load, phase unbalance or phase failure. An overload, phase un-
balance or phase failure result in an increase of the motor current
beyond the set motor rated current. This current rise is detected
by the current transformers integrated into the devices and eval-
uated 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 the contactors control circuit. The break
time depends on the ratio between the tripping current and set
current 
e
and is stored in the form of a long-term stable tripping
characteristic (see Characteristic Curves).
In addition to inverse-time delayed protection of loads against
excessive temperature rise due to overload, phase unbalance
and phase failure, the 3RB21/31 solid-state overload relays also
allow internal ground-fault detection (not possible in conjunction
with wye-delta assemblies). This provides protection of loads
against high-resistance short-circuits due to damage to the
insulation material, moisture, condensed water etc.
The devices are manufactured in accordance with environmen-
tal guidelines and contain enviro
nmentally friendly
and reusable
materials. They comply with important worldwide standards and
approvals.
Application
Industries
The 3RB2 / 3RB3 solid-state overload relays are suitable for
customers from all industries who want to provide optimum
inverse-time delayed protection of their electrical loads
(e.g. motors) under normal and heavy starting conditions
(CLASS 5 to CLASS 30), minimize project completion times,
inventories and power consumption, and optimize plant
availability and maintenance management.
Application
The 3RB2 / 3RB3 solid-state overload relays have been
designed for the protection of three-phase motors in sinusoidal
50/60 Hz voltage networks. The relays are not suitable for the
protection of single-phase AC or DC loads.
The 3RU thermal overload relay or the 3RB22/3RB23 solid-
state overload relay can be used for single-phase AC loads.
For DC loads the 3RU thermal overload relays are available.
Ambient conditions
The devices are insensitive to external influences such as
shocks, corrosive environments, ageing and temperature
changes.
For the temperature range from –25 C to +60 °C, the
3RB2 / 3RB3 solid-state overload relays compensate the
temperature according to IEC 60947-4-1.
The 3RB2 / 3RB3 solid-state overload relays are suitable for the
overload protection of explosion-proof motors with "increased
safety" type of protection EEx e according to ATEX guideline
94/9/EC. The relays meet the requirements of EN 60079-7 (Elec-
trical apparatus for potentially explosive atmospheres –
Increased safety "e").
The basic safety and health requirements of ATEX guideline
94/9/EG are fulfilled by compliance with
• EN 60947-1
• EN 60947-4-1
•
EN 60947-5-1
• EN 60079-14
EU type test certificate for Group II, Category (2) G/D under
application. It has the number PTB 09 ATEX 3001.
Accessories
The following accessories are available for the 3RB2/3RB3
solid-state overload relays:
• One terminal bracket each for the overload relays size S00
and S0 (sizes S2 to S12 can be installed as single units without
a terminal bracket)
• One mechanical remote RESET module for all sizes
• One cable release for resetting devices which are difficult to
access (for all sizes)
• One sealable cover for all sizes
• Box terminals for sizes S6 and S10/S12
• Terminal covers for sizes S2 to S10/S12
Connection for mounting onto contactors:
Optimally adapted in electrical, mechanical and design terms to the
contactors. The overload relay can be connected directly to these
contactor using these pins. Stand-alone installation is possible as
an alternative (in conjunction with a terminal bracket for stand-alone
installation).
Selector switch for manual/automatic RESET and RESET button:
With this switch you can choose between manual and automatic
RESET. A device set to manual RESET can be reset locally by
pressing the RESET button. On the 3RB21 a solid-state remote
Switch position indicator and TEST function of the wiring:
Indicates a trip and enables the wiring test.
Motor current setting:
Setting the device to the rated motor current is easy with the large
rotary knob.
Trip class setting/internal ground-fault detection (3RB21 only):
Using the rotary switch you can set the required trip class and activate
the internal ground-fault detection dependent on the starting conditions.
Connecting terminals (removableterminalblockforauxiliarycircuits):
The generously sized terminals permit connection of two conductors
auxiliary circuit can be connected with screw-type terminals or with
spring-loaded terminals.
is integrated into the unit.
Solid state test:
Enables a test of all important device components and functions.
The "tripped" status is signaled by means of a switch position
indicator (see Function). Resetting takes place either manually
or automatically after the recovery time has elapsed
(see Function).
Overload Relays
3RB2 / 3RB3 Solid-State Overload Relays
3RB20, 3RB21, 3RB30, 3RB31 up to 630A for standard applications