SIEMENS
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Siemens IC 10 · 2017
Overload Relays
SIRIUS 3RB2 Electronic Overload Relays
3RB22, 3RB23 for high-feature applications
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Overview
SIRIUS 3RB22 and 3RB23 evaluation modules
The 3RB22 and 3RB23 electronic overload relays up to 630 A
(up to 820 A possible in combination with a series transformer)
are from a modular system and comprise an evaluation unit, a
current measuring module and a connecting cable. The 3RB22
overload relays (with monostable auxiliary contacts) and the
3RB23 overload relays (with bistable auxiliary contacts) are
supplied from an external voltage.
They have been designed for inverse-time delayed protection of
loads with normal and heavy starting against excessive
temperature rises due to overload, phase asymmetry or phase
failure. An overload, phase asymmetry or phase failure result in
an increase of the motor current beyond the set rated motor
current.
This current rise is detected by means of a current measuring
module
(see page 7/132)
and electronically evaluated by the
evaluation module which is connected to it. The evaluation elec-
tronics sends a signal 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 current setting
I
e
and is stored in the form of a long-
term stable tripping characteristic curve
(see Characteristic
Curves)
. The "tripped" status is signaled by means of a
continuous red "
OVERLOAD
" LED.
The LED indicates imminent tripping of the relay due to overload,
phase asymmetry or phase failure by flickering when the limit
current has been violated. In the case of the 3RB22 and 3RB23
overload relays this warning can also be issued through auxiliary
contacts.
In addition to the described inverse-time delayed protection of
loads against excessive temperature rises, the 3RB22 and
3RB23 electronic overload relays also allow direct temperature
monitoring of the motor windings (full motor protection) by
connection with broken-wire interlock of a PTC sensor circuit.
With this temperature-dependent protection, the loads can be
protected against overheating caused, for example, indirectly
by reduced coolant flow and which cannot be detected by
means of the current alone. In the event of overheating, the de-
vices switch off the contactor, and thus the load, by means of the
auxiliary contacts. The "tripped" status is signaled by means of a
continuously illuminated "
THERMISTOR
" LED.
To protect the loads against high-resistance short circuits due to
damage to the insulation, humidity, condensed water, etc., the
3RB22 and 3RB23 electronic overload relays offer the possibility
of internal ground fault monitoring in conjunction with a function
expansion module (for details,
see Operating Instructions
, not
possible in conjunction with contactor assemblies for start-delta
(wye-delta) starting). In the event of a ground fault the 3RB22
and 3RB23 relays trip instantaneously.
The "tripped" status is signaled by means of a continuous red
"Ground Fault" LED. Signaling through auxiliary contacts is also
possible.
After tripping due to overload, phase asymmetry, phase failure,
thermistor or ground-fault tripping, the relay is reset manually or
automatically after the recovery time has elapsed.
In conjunction with a function expansion module, the motor
current measured by the microprocessor can be output in the
form of a DC 4 mA to 20 mA analog signal for operating rotary
coil instruments or for feeding into analog inputs of programma-
ble logic controllers.
More information
Home page,
Industry Mall,
see www.siemens.com/product?3RB2
Application Manual "SIRIUS Controls with IE3/IE4 Motors",
see
Operating Instructions "3RB22, 3RB23 Electronic Overload Relays",
see
Characteristics and certificates,
see
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3RB2985 function expansion module:
Enables more functions to be added, e.g. internal ground-fault
detection and/or an analog output with corresponding signals.
Motor current and trip class setting:
Setting the device to the motor current and to the required trip class
dependent on the start-up conditions is easy with the two rotary
switches.
Connecting terminals (removable joint block):
The generously sized terminals permit connection of two conductors
with different cross-sections for the auxiliary, control and sensor
circuits. Connection is possible with screw connection and
alternatively with spring-type connection.
Test/RESET button:
Enables testing of all important device components and functions,
plus resetting of the device after a trip when manual RESET is
selected.
Selector switch for manual/automatic RESET:
With this switch you can choose between manual and automatic
RESET.
Red LED "OVERLOAD":
A continuous red light signals an active overload trip; a flickering red
light signals an imminent trip (overload warning).
Red LED "THERMISTOR":
A continuous red light signals an active thermistor trip.
Red LED "GND FAULT":
A continuous red light signals a ground-fault tripping.
Green LED "READY":
A continuous green light signals that the device is working correctly.
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NSB0_01621b
© Siemens AG 201
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