Reduced-voltage motor starting
SIRIUS 3RW Soft Starters
Solid-state soft starters for controlled starting and stopping of three-phase motors, reducing mechanical shock and line-voltage disturbance.
Used where a motor runs primarily at line speed but needs gentler acceleration or deceleration than direct or star-delta starting can provide.
Request exact article number Selection is confirmed against motor, I/O, network and destination data.
Technical parameters
Selection data
These values describe the product family and the decisions behind selection. The exact datasheet is tied to the complete Siemens article number.
ParameterFamily rangeEngineering note
Performance classesBasic, General and High Performance familiesMatch the family to starting difficulty, functions and communication.
Sizing basisMotor current and application dutyStarting time, current limit, starts/hour and ambient determine derating.
BypassIntegrated bypass on main product familiesBypass reduces steady-state heat but not starting thermal load.
ControlVoltage ramp, current limit and torque-control optionsAvailable methods depend on the 3RW family.
CommunicationOptional PROFINET, EtherNet/IP and other modules by familyConfirm protocol and diagnostic requirements before selection.
SafetyFailsafe/STO options on selected high-performance devicesSafety requires risk assessment and validation of the complete circuit.
Common search questions
Quick answers for SIRIUS 3RW Soft Starters.
Family guidance narrows the request. The exact Siemens article number remains the final commercial and technical identity.
What is SIRIUS 3RW Soft Starters best suited for?
Used where a motor runs primarily at line speed but needs gentler acceleration or deceleration than direct or star-delta starting can provide. Typical applications include water pumps, industrial fans, compressors.
Which information is required to select SIRIUS 3RW Soft Starters?
Start with motor nameplate, load torque and inertia, start/stop time and starts per hour, current limit and controlled-stop need. Final ratings and accessories are confirmed against the full article number and current manufacturer data.
Can SIRIUS 3RW Soft Starters be quoted from a model name only?
A model name identifies a family, not always the exact hardware. Honghao checks the complete article number, electrical data, options, accessories, lifecycle status, quantity and destination before confirming the offer.
Good fit
Use it when
- Pumps with controlled stop
- Fans and compressors
- Conveyors with gentle acceleration
- Crushers and demanding starts with correct sizing
Selection limits
Check before specifying
- A soft starter does not regulate running speed
- Heavy starts require thermal sizing from the full starting profile
- Exact ratings, functions, approvals and lifecycle status depend on the complete Siemens article number and firmware. Honghao confirms these against the requested BOM before quotation.
Strengths
Why this family
- Reduced mechanical stress
- Lower starting-current peaks
- Compact alternative to electromechanical starting methods
- Application-specific control and diagnostics
Typical BOM
Accessories
- Communication module
- Operator panel
- Motor and short-circuit protection
- Line/bypass contactors where required
- Panel cooling and ventilation
Application data
What to send
- Motor nameplate
- Load torque and inertia
- Start/stop time and starts per hour
- Current limit and controlled-stop need
- Ambient, altitude and communication
Technical basis
Manufacturer data remains the final reference.
Honghao uses family-level guidance to structure the enquiry. Final ratings, options, certificates and lifecycle status are checked against the exact article number and current manufacturer documentation.
Typical applications
Where it is used
RFQ checklist
Get a usable quotation
Send the full article number if it is a replacement. For a new application, send the project data listed above, quantity, destination country and required delivery date.
Send BOM or application dataExact configuration