© Siemens AG 2011
Overload Relays
SIRIUS 3RU1 Thermal Overload Relays
3RU11 for standard applications
■
Overview
"Increased safety" type of protection EEx e according to
ATEX directive 94/9/EC
The 3RU11 thermal overload relays are suitable for the overload
protection of explosion-proof motors with "increased safety" type
of protection EEx e. The relays meet the requirements of
EN 60079-7 (Electrical apparatus for areas subject to explosion
hazards – Increased safety "e");
see Catalog IC 10.
3
5
4
7
6
1
2
EC type test certificate for Category (2) G/D exists. It has the
number DMT 98 ATEX G 001.
■
Benefits
The most important features and benefits of the 3RU11 thermal
overload relays are listed in the overview table
(see
"General Data" on page 5/42).
■
Application
Industries
$
Connection for mounting onto contactors:
%
&
(
)
*
+
Optimally adapted in electrical, mechanical and design terms to the
contactors. Connecting pins can be used for direct mounting of the
overload relays. Stand-alone installation is possible as an alternative
(in some cases in conjunction with a stand-alone installation module).
Selector switch for manual/automatic RESET and RESET button:
With this switch you can choose between manual and automatic RE-
SET. A device set to manual RESET can be reset locally by pressing
the RESET button. A remote RESET is possible using the RESET mod-
ules (accessories), which are independent of size.
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 ro-
tary knob.
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.
Transparent, sealable cover:
Secures the motor current setting and the TEST function against ad-
justment.
Supply terminals:
The generously sized terminals permit connection of two conductors
with different cross-sections for the main and auxiliary circuits. The
auxiliary circuit can be connected with screw terminals and alterna-
tively with spring-type terminals.
The 3RU11 thermal overload relays are suitable for customers
from all industries who want to guarantee optimum inverse-time
delayed protection of their electrical loads (e. g. motors) under
normal starting conditions (CLASS 10).
Application
The 3RU11 thermal overload relays have been designed for the
protection of three-phase and single-phase AC and DC motors.
If single-phase AC or DC loads are to be protected by the 3RU11
thermal overload relays, all three bimetal strips must be heated.
For this purpose, all main current paths of the relay must be con-
nected in series.
Ambient conditions
The 3RU11 thermal overload relays have temperature compen-
sation in accordance with IEC 60947-4-1 for the temperature
range of –20 °C to +60 °C. For temperatures from +60 °C to
+80 °C the upper set value of the setting range must be reduced
by the factor listed in the table below.
Ambient temperature in °C
+60
+65
+70
+75
+80
5
Derating factor for the upper set
value
1.0
0.94
0.87
0.81
0.73
The 3RU11 thermal overload relays up to 100 A have been de-
signed for inverse-time delayed protection of loads with normal
starting
(for "Function" see note on Technical Information on
page 5/1)
against excessive 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 ele-
ments, this current rise heats up the bimetal strips inside the de-
vice which then bend and as a result trigger the auxiliary con-
tacts 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 set cur-
rent
I
e
and is stored in the form of a long-term stable tripping
characteristic
(for "Characteristic Curves" see the note on Tech-
nical Information on page 5/1).
The "tripped" status is signaled by means of a switch position in-
dicator. Resetting takes place either manually or automatically
after a recovery time has elapsed
(for "Function" see note on
Technical Information on page 5/1).
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 ap-
provals.
■
Accessories
The following optional accessories are available for the 3RU11
thermal overload relays:
• For the four overload relay sizes S00 to S3 one terminal
bracket each for stand-alone installation
• One mechanical RESET module for all sizes
• One cable release for resetting devices which are difficult to
access (for all sizes)
• One electrical remote RESET module in three voltage variants
for all sizes
• Terminal covers
5/46
Siemens LV 1 AO · 2011
SIEMENS [ Siemens Semiconductor Group ]
