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Siemens IC 10 · 2017
Overload Relays
SIRIUS 3RU2 Thermal Overload Relays
3RU2 for standard applications
7
SIRIUS 3RU2136-4.B0 thermal overload relay
3RU21 thermal overload relays up to 100 A have been designed
to provide current-dependent protection for loads with normal
starting against impermissibly high temperature rises due to
overload or phase failure.
An overload or phase failure results in an increase of the motor
current beyond the set rated motor current. Via heating
elements, this current rise heats up the bimetal strips inside the
device which then bend and as a result trigger the auxiliary
contacts by means of a tripping mechanism. 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 characteristic curve,
see Characteristic curves
.
The "tripped" status is signaled by means of a switch position
indicator. The relay is reset manually or automatically after a
recovery time has elapsed.
The 3RU2 thermal 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.
Use in hazardous areas
The 3RU2 overload relays are certified in accordance with the
European explosion protection directive (ATEX) and the interna-
tional explosion protection standard (IECEx),
see Certificates
.
Article No. scheme
Note:
The Article No. scheme shows an overview of product versions
for better understanding of the logic behind the article numbers.
For your orders please use the article numbers quoted in the
selection and ordering data.
6
2
1
5
4
3
Connecting terminals:
Depending on the device version, the connecting terminals are
screw terminals or spring-type terminals for the the main and
auxiliary circuits.
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. The overload relay can be connected directly to the
contactor using these pins. Stand-alone installation is possible as
an alternative (in conjunction with a terminal bracket for stand-alone
installation).
6
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. A remote RESET is possible using the
RESET modules (accessories), which are independent of size.
5
Switch position indicator and TEST function of the wiring:
Indicates a trip and enables the wiring test.
1
Motor current setting:
Setting the device to the rated motor current is easy with the large
rotary knob.
2
STOP button:
If the STOP button is pressed, the NC contact is opened. This
switches off the contactor downstream. The NC contact is closed
again when the button is released.
4
3
IC01_00403a
Product versions
Article number
Thermal overload relays
3RU2
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Device type
e. g. 1 = CLASS 10, 1 NO + 1 NC
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Size, rated operational current and
power
e. g. 16 = 16 A (7.5 kW) for size S00
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Setting range for overload release
e. g. 0A = 0.11 ... 0.16 A
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Connection methods
e.g. B = screw terminals
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Installation type
e. g. 0 = mounting on contactor
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Example
3RU2
1
1
6
–
0
A
B
0
© Siemens AG 2016