Siemens 3RB20 Manual de referencia - Página 9

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■

Overview

(1) Connection for mounting onto contactors:

Optimally adapted in electrical, mechanical and design terms to the

contactors and soft starters, these connecting pins can be used for di-

rect mounting of the overload relays. Stand-alone installation is possi-

ble as an alternative (in some cases in conjunction with a stand-alone

installation module).

(2) 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 mod-

ules (accessories), which are independent of size.

(3) Switch position indicator and TEST function of the wiring:

Indicates a trip and enables the wiring test.

(4) Motor current setting:

Setting the device to the rated motor current is easy with the large

rotary knob.

(5) 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.

(6) Transparent sealable cover

Secures the motor current setting and the TEST function against

adjustment.

(7) 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 up to 100 A have been desi-

gned for inverse-time delayed protection of loads with normal st-

arting

(see "Function")

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 elements, this current rise heats up the bi-

metal 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 trip-

ping current and current setting I

long-term stable tripping characteristic

ves").

The "tripped" status is signaled by means of a switch position in-

dicator. Resetting takes place either manually or automatically

after the recovery time has elapsed

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.

and is stored in the form of a

(see "Characteristic Cur-

(see

"Function").

Overload Relays

3RU1 Thermal Overload Relays

3RU11 for standard applications

"Increased safety" type of protection EEx e acc. to ATEX di-

rective 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;

see Catalog LV 1, Chapter 20 "Appendix" --> "Standards and ap-

provals" --> "Type overview of approved devices for explosion-

protected areas (ATEX Explosion Protection)".

EC type test certificate for Category (2) G/D exists. It has the

number DMT 98 ATEX G 001.

■

Design

Device concept

The 3RU11 thermal overload relays are compact devices, i. e.

current measurement and the evaluation unit are integrated in a

single enclosure.

Mounting options

The 3RU11 thermal overload relays can be mounted directly

onto the 3RT1 contactors (exception: size S00 with Cage Clamp

terminals can only be installed as a stand-alone installation).

With the matching terminal brackets the devices can still be ins-

talled as stand-alone units.

For more information on the mounting options see "Technical

specifications" and Catalog LV 1, "Selection and ordering

Connection methods

All sizes of the 3RU11 thermal overload relays with screw termi-

nal can be connected to the auxiliary and main current paths.

Rails can be connected to the main conductor connections of

size S3 overload relays if the box terminals are removed.

As an alternative, the devices are also available with Cage

Clamp terminals. The auxiliary conductor connections of these

devices, and for size S00 the main conductor connections as

well, are fitted with Cage Clamp terminals.

For more information on the connection options see "Technical

specifications" and Catalog LV 1, "Selection and ordering data".

Overload relays in contactor assemblies for

wye-delta starting

When overload relays are used in combination with contactor as-

semblies for wye-delta starting it must be noted that only 0.58

times the motor current flows through the line contactor. An over-

load relay mounted onto the line contactor must be set to 0.58

times the motor current.

An assignment of the 3RU11 thermal overload relays to the line

contactors of our 3RA contactor assemblies for wye-delta star-

ting can be found under "Controls ---> Contactors and Contactor

Assemblies".

Operation with frequency converter

The 3RU11 thermal overload relays are suitable for operation

with frequency converters. Depending on the frequency of the

converter, a higher current than the motor current must be used

in some cases due to eddy-currents and skin effects.

data".

Siemens · 2011