Siemens 3RW5 Series Motor Soft Starter Specifications

Siemens 3RW5 — SIRIUS Soft Starter for Smooth Motor Starting and Stopping

Siemens 3RW5 series with over 710 variants provides electronic soft starting for three-phase induction motors from 3kW to 1200kW at 400V. Soft starters reduce mechanical stress on couplings, belts, and gears during motor starting by ramping up voltage gradually — eliminating the 6-8× full-load current surge of direct-on-line (DOL) starting.

Soft Starter vs VFD: When to Choose Each

Feature	Soft Starter (3RW5)	VFD (SINAMICS G120)
Speed control	No — fixed speed after start	Yes — variable speed continuously
Starting current	Reduced (typically 3-4× FLA)	Programmable, typically 1.0-1.5× FLA
Cost (relative)	~0.3-0.5×	~1.0×
Energy savings during run	None	20-60%

Select a soft starter when the application requires only smooth starting and stopping — pumps, fans, compressors, and conveyors where speed is constant and the primary goal is reducing mechanical shock and limiting inrush current. Select a VFD when the process requires continuous speed control for throughput regulation, energy savings, or soft stopping.

Availability

3RW5 soft starters: broadly stocked at Siemens distributors. SIRIUS Soft Starter ES (engineering software) for parameter setting.

About the Siemens 3RW5 Series

The Siemens 3RW5 Series series groups 712 related part numbers, each listed with full specifications, a datasheet where available, and an RFQ option. The listed variants share a common mounting of screw fixing. Variants differ by depth, height and width, so you can match the exact depth your application requires using the selection guide below.

Select a variant by

Depth: 82 mm · 152 mm · 203 mm · 249 mm
Height: 126 mm · 198 mm · 275 mm · 306 mm
Width: 28 mm · 120 mm · 170 mm · 185 mm
Service factor: 1 · 1.15
Trip class: CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2 · CLASS 10 A / 10E (preset) / 20E; acc. to IEC 60947-4-2

Shared specifications

Mounting: screw fixing

Variant comparison

Parameter	3RW5526-1HA14	3RW5525-1HA14	3RW5517-1HA14	3RW5516-1HA14	3RW5524-1HA14	3RW5527-1HA14
Depth	203 mm	203 mm	152 mm	152 mm	203 mm	203 mm
Height	306 mm	306 mm	275 mm	275 mm	306 mm	306 mm
Width	185 mm	185 mm	170 mm	170 mm	185 mm	185 mm
Service factor	1.15	1.15	1.15	1.15	1.15	1.15
Trip class	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2	CLASS 10 A / 10E (default) / 20E / 30E; acc. to IEC 60947-4-2

Request a quote on any Siemens 3RW5 Series part number and we confirm price, availability and lead time per line — including end-of-life and allocation-constrained variants.

All variants