3RT2015-2BB42 Siemens SIRIUS Main contactor


  • 3RT2015-2BB42
  • Main contactor
  • Construction size S00
  • AC-3
  • 3 kW/400 V
  • Auxiliary contacts: 1 x normally closed contact
  • Control voltage: 24 V DC
  • Spring-loaded connection

Main contactor Siemens SIRIUS 3RT2015-2BB42


— Version not possible

✓ Version possible

1) Connection system:
– Main circuit: Busbar connection (optionally with box terminals),
– Auxiliary/control circuit: screw terminals or spring-loaded terminals.

Contactors with screw terminals: 3RT2 (sizes S00 to S3) and 3RT1 (sizes S6 to S12)

3RT contactors, sizes S00 to S12

Our power range:

  • Contactors for switching motors:
    • Size S00: 3RT201 up to 7.5 kW
    • Size S0: 3RT202 up to 18.5 kW
    • Size S2: 3RT203 up to 37 kW
    • Size S3: 3RT204 up to 55 kW
    • Sizes S6 to S12: 3RT10 up to 250 kW
  • Vacuum contactors for switching motors, see :
    • Sizes S10 and S12: 3RT12 up to 250 kW
    • Size 14: 3TF6 up to 450 kW

IEC/EN 60947‑1, IEC/EN 60947‑4‑1, IEC/EN 60947‑5‑1 (auxiliary switches)

Ambient conditions

If the devices are used in ambient conditions which deviate from common industrial conditions (IEC 60721‑3‑3 “Stationary Use, Weather-Protected”), information must be obtained about possible restrictions with regard to the reliability and endurance of the device and possible protective measures. In this case, contact our Technical Support,

Auxiliary contact complement
  • Size S00: An auxiliary contact is integrated in the basic unit.
  • Sizes S0 to S3: The basic units contain two integrated auxiliary contacts (1 NO + 1 NC).
    All basic units, with the exception of coupling contactors sizes S00 and S0, can be expanded using auxiliary switches, see .
  • Sizes S6 to S12: These contactors are supplied with two laterally mounted auxiliary switches. The fitting of auxiliary switches is possible on the front and on the side (the 3RT12 vacuum contactor is an exception: only lateral mounting of auxiliary switches is possible here).

For detailed information on the fitting of auxiliary switches, see .

Contact reliability

If voltages ≤ 110 V and currents ≤ 100 mA are to be switched, the auxiliary contacts of the 3RT contactors or 3RH contactor relays should be used as they guarantee a high level of contact reliability.

These auxiliary contacts are especially suitable for solid-state circuits with currents ≥ 1 mA at a voltage of 17 V and higher.

Connection methods

Main circuit

  • Sizes S00 and S0: screw or spring-loaded terminals, spring-loaded terminals with convenient plug-in design for device connectors
  • Sizes S2 and S3: screw terminals with box terminal; direct connection to the connecting bar possible with cable lugs for S3 when the box terminal is removed.
  • Sizes S6 to S12: screw terminals with connecting bars that the cables can be connected to using either cable lugs or flexible or rigid busbars. Alternatively, box terminals are available as accessories.

Auxiliary/control circuit

  • Sizes S00 to S12: Screw or spring-loaded terminals
Electromagnetic compatibility (EMC)

The 3RT contactors fulfill the requirements for environment category A.


When the contactors are used in an environment with frequency converters, the configuration notes in the Equipment Manual must be observed, see .

Short-circuit protection

For short-circuit protection of contactors without overload relays, see the product data sheet of the relevant contactor.

Refer to the configuration manuals for details of short-circuit protection of contactors with overload relays or of load feeders, see Technical Specifications.

Selection aids are available for fuseless assembly of motor feeders consisting of 3RV2 motor starter protector and 3RT2 contactor, see .

Motor protection

3RT2 contactors

or can be mounted on the 3RT2 contactors for protection against overload

can be mounted on the 3RT1 contactors for protection against overload.

Plant and application monitoring

For monitoring and measuring in the application, can be mounted on the 3RT2 contactors.

Ratings of three-phase motors

The quoted rating (in kW) refers to the output power on the motor shaft (according to the nameplate).

The power rating specifications of the contactors in kW (in accordance with IEC 60947-4-1, Table G) are guide values for 4-pole standard motors at 50 Hz AC and specified voltage (e.g. 400 V AC). The actual starting and rated data of the motor to be switched must be considered when selecting the units. The motor current, motor protection device and the permissible contactor current according to the utilization category must be aligned with each other.

Surge suppression

3RT contactors supplied without a coil circuit can be retrofitted with RC elements, varistors, diodes or diode assemblies (assembly of diode and Zener diode for short break times) for damping opening surges in the coil.

  • Size S00: the surge suppressors are plugged onto the front of the contactors here. Space is provided for them next to a snap-on auxiliary switch.
  • Sizes S0 and S2: surge suppressors (varistors, RC elements or diode combinations) can be plugged into the front of the contactors.
  • Sizes S3: the varistors and diode combinations are plugged into the front of the contactors. The RC element is plugged into the two recesses on the front of the contactor to the left of the connection block for the auxiliary switches.
  • Sizes S6 to S12: replaceable operating mechanisms with integrated coil circuit (varistor)


The OFF-delay of the NO contact and the ON-delay of the NC contact are increased if the contactor coils are attenuated against voltage peaks (for details, see the relevant manual → Technical specifications).

Contactors with voltage tap-off

3RT2 contactors

The contactors in sizes S00 to S3 with voltage tap-off are special versions for mounting the for connection to the control system through IO‑Link or AS‑Interface.

Without a function module, the contactors can be used like the standard versions.

For more information on IO‑Link and AS‑Interface, see .

Operating mechanism types

3RT2 contactors

The contactors are available as standard versions with AC or DC operating mechanisms or as versions with a wide-range solid-state operating mechanism and a universal actuating voltage (AC or DC operation possible).

In addition, for sizes S2 and S3, variants with electronic operating mechanism for AC or DC operation with a fail-safe PLC input are available.

Control takes place via the control supply voltage connection A1 ‑ A2 with different operating ranges (for details on this, see the respective product data sheet).

DC coupling contactors with reduced power consumption are also ideally suited for connection to the controller.

3RT1 contactors

The following control and/or operating mechanism versions are available in sizes S6 to S12:

  • Standard operating mechanism with economy circuit for AC and DC operation (switchover from closing coil to holding coil)
  • Solid-state operating mechanism
    Overvoltage damping of the operating mechanism coil is already integrated in the electronics for contactors with solid state operating mechanisms. The operating mechanisms are powered via a supply voltage with an operating range from 0.8 to 1.1 x Us, optionally also controlled depending on the chosen mode of operation. Alternatively, control is also possible via the separate 24 V DC control signal input. Various rated voltage ranges for AC/DC control are available.The following versions are available:

    • With two operating modes: Direct control or via PLC input
    • As above, but with additional remaining lifetime indicator (RLT)
    • With fail-safe PLC input for simplification of safety applications (without mode of operation selection)
Solenoid coils/operating mechanisms

3RT2 contactors

Coil replacement is possible for sizes S0 to S3.

3RT1 contactors

The operating mechanisms for 3RT10..‑.A/‑.N/‑.P contactors are removable and can be replaced simply by unlocking and pulling them out.

NOTICE: Removal or changing of the operating mechanism is not permitted for 3RT10..‑.S contactors with fail-safe control.

Contactors in safety-related applications

Contactors are a significant part of safety-related applications. They are generally the actuators that perform the switching operation leading to the safe disconnection of the corresponding application or system.

Contactors with mirror contacts according to IEC 60947-4-1 are generally required for use in safety-related applications. Most of our contactors meet this requirement; a corresponding note can be found in the technical product data sheet.

Contactors with increased tamper protection

Increased tamper protection can be ensured either by using our contactor versions with factory-fitted, permanently mounted auxiliary switches which are protected against mechanical external operation (e.g. 3RT2…‑…..‑3MA0 or 3RT1…‑…..‑3PA0 contactors), or by using the or sealable cover as an accessory.

Connection of contactors to fail-safe control modules

While contactors with small powers can be connected directly to the outputs of a fail-safe controller, implementing safety-related applications with standard contactors with higher power is much more complicated and elaborate because of the necessary coupling links.

Due to their fail-safe control input, special contactors provide a much simpler way of doing this:

  • 3RT20..‑.S contactors in sizes S2 and S3
  • 3RT10..‑.S contactors in sizes S6 to S12

For more information, see .

Example for SIL 2 and SIL 3 / PL e application – previously:

Application with safety-related disconnection with standard contactors using the example of a 3RT105 contactor

Example for SIL 3 / PL e (left-hand side) and SIL 2 / PL c (right-hand side) Application – new:

Application with safety-related disconnection with contactors with fail-safe control using the example of a 3RT105 contactor

Contactors for special applications
Article No. scheme


The Article No. scheme shows an overview of product versions for better understanding of the logic behind the article numbers.

Please use the article numbers specified in the selection and ordering data for your order.

Technical specifications


Power contactor, AC-3 7 A, 3 kW / 400 V 1 NC, 24 V DC 3-pole, Size S00 Spring-type terminal


DataSheet in PDF

Weight 0.312 kg
Dimensions 50.00 × 73.50 × 77.50 mm


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