Integrating Siemens SIRIUS Soft Starters via PROFINET in SIMATIC PCS 7

To integrate a Siemens SIRIUS 3RW44 or 3RW55 soft starter via PROFINET into SIMATIC PCS 7, install the dedicated 'SIMATIC PCS 7 Block Library SIRIUS Soft Starter' and import the device GSDML file into STEP 7 HW Config. Configure the PROFINET IO station with standard cyclic telegrams for motor control and fault status, and instantiate the driver block SS_DIR in Continuous Function Chart (CFC). To retrieve actual operating currents, active power, and line voltages without consuming cyclic bus bandwidth, instantiate the measurement block SS_MEAS, which issues acyclic data record read requests (RDREC, SFB52) targeting data record index 92 or 94. Compile the OS to generate APL-style WinCC faceplates.

Architecture of SIRIUS Soft Starter Integration in PCS 7

Siemens SIRIUS 3RW44 and 3RW55 soft starters provide torque-controlled soft starting, dynamic DC braking, and comprehensive motor thermal monitoring for three-phase induction drives. In SIMATIC PCS 7, these intelligent motor controllers connect directly to the PROFINET IO fieldbus downstream of S7-400 or CPU 410-5H controllers.

Standard PROFINET IO engineering requires two distinct software packages: the device GSDML file for hardware catalog registration, and the 'SIMATIC PCS 7 Block Library SIRIUS Soft Starter' (Order Number 3ZS1633-1XX02-0YB0 for 3RW44, or 3ZS1633-1XX03-0YB0 for 3RW5). The dedicated block library provides APL-compliant driver blocks, message configuration, and pre-engineered WinCC faceplates that display motor state, electrical metrics, and alarm diagnostics seamlessly.

Cyclic Telegrams vs Acyclic Data Record Reading

PROFINET fieldbus communication is split into cyclic process data exchange and acyclic dataset communication:

Cyclic Process Data (Telegrams): Exchanged deterministically on every I/O cycle via the controller's peripheral input and output image. Cyclic telegrams carry mission-critical real-time commands such as start forward (FwdAut), start reverse (RevAut), emergency stop, reset, and basic feedback signals (motor running, ready, group fault, group warning).
Acyclic Data Records (RDREC / WRREC): High-volume diagnostic and statistical metrics are transferred on demand using system function blocks SFB52 (RDREC) and SFB53 (WRREC). The soft starter stores actual phase currents, line voltages, active power, power factor, thermal motor model percentage, and trip logs in predefined data records (such as Index 92 and 94). Acyclic polling prevents saturation of cyclic PROFINET IO bandwidth.

SIRIUS Library Block Functions and Parameter Mapping

The table below details the core function blocks included in the PCS 7 SIRIUS Soft Starter Library, along with their communication mechanism and parameter mappings.

Block NameFunction DescriptionCommunication MechanismKey Parameters & I/O PinsSS_DIRMotor forward/reverse start, stop, and trip evaluationCyclic PROFINET Telegram (I/O Image)FwdAut, RevAut, StopAut, Trip, MotorAct, PdrvSS_MEASReads 3-phase currents, line voltages, and active powerAcyclic Data Records via RDREC (Index 92/94)I_L1, I_L2, I_L3, V_L1_L2, P_Act, CosPhiSS_DIAGFieldbus device diagnostics and communication healthAcyclic Diagnostics (RDREC / SFB54)DiagAct, ErrComm, FaultAct, WarnAct, DevStateSS_STATStatistical operating data, run hours, and start countsAcyclic Reading via RDREC (Index 95)OpHours, OperCycles, TripCount, MotorStartsSS_DIR_LExtended direct starter block with full APL interlockingCyclic Telegrams & Acyclic Dataset AccessIntlock, Permit, Protect, RstLi, LocalLi

Step-by-Step PROFINET Integration and CFC Configuration

Execute the following steps to configure the SIRIUS soft starter in SIMATIC PCS 7:

Install Hardware Support and Library:
- Install the PROFINET GSDML file for the 3RW soft starter in STEP 7 HW Config via Options -> Install GSD Files.
- Run the setup for the SIMATIC PCS 7 Block Library SIRIUS Soft Starter on the Engineering Station.
Configure HW Config:
- Drag the 3RW soft starter from PROFINET IO -> Additional Field Devices -> Drives -> SIRIUS onto the PROFINET IO rail.
- Assign device name and IP address matching the physical station label.
- Insert standard cyclic telegrams (e.g., Basic Parameters 4-byte I / 4-byte Q) into the device slots.
- Save and compile HW Config, then download the station configuration to the automation system.
Instantiate Driver Blocks in CFC:
- Open the target CFC chart. From the SIRIUS library, drag SS_DIR onto the sheet.
- Interconnect the logical address input LADDR to the hardware start address of the input telegram configured in HW Config.
- Drag SS_MEAS onto the chart and interconnect its LADDR pin to the same hardware diagnostic address.
- Interconnect the SS_DIR motor control outputs (FwdAut, RevAut, StopAut) to your technological process interlocks.
Compile AS and OS:
- Execute Generate Module Drivers during CFC compilation: driver blocks link automatically to the diagnostic tree.
- Run OS Compilation (Entire OS with memory tags). Open the WinCC Graphics Designer to position the generated APL block icon.

Verification

Verify soft starter integration through the following systematic checks:
1. Confirm PROFINET communication: in HW Config online view, verify that the soft starter icon displays a green checkmark without bus errors.
2. In the CFC editor online test mode, verify that SS_DIR.Trip = 0 and SS_DIR.DevState indicates 'Ready to Start'.
3. In SS_MEAS, verify that live motor current pins (I_L1, I_L2, I_L3) display realistic non-zero values during test motor rotation.
4. On the WinCC runtime client, open the soft starter APL faceplate: verify that motor state, phase currents, and alarm acknowledgment respond dynamically to operator commands.

Limitations and Operational Precautions

Acyclic data reading via SFB52 (RDREC) consumes CPU communication resources and is throttled by the controller operating system. Never execute RDREC continuously on every OB35 cyclic scan; instantiate SS_MEAS with cyclic polling intervals no faster than 1 to 2 seconds. In multi-device installations with dozens of soft starters, stagger measurement acquisition to prevent buffer overflows in CPU communication buffers. Furthermore, verify that the 3RW soft starter PROFINET communication module firmware matches the version defined in HW Config.

Engineer FAQ

Can I read phase currents using cyclic telegrams without SS_MEAS?

Yes, if the soft starter GSDML configuration supports an extended cyclic telegram that includes current measurement words. However, doing so increases continuous PROFINET cyclic bus load. Using SS_MEAS with acyclic reading is the standard Siemens best practice.

What happens if PROFINET communication to the soft starter is interrupted?

The SS_DIR driver block detects connection loss via system OB86/OB82, sets Trip = 1, drives Bad = 1, and raises a communication alarm on the OS. The physical soft starter enters a safe shutdown state according to its parameterised fieldbus watchdog setting.

Can SIRIUS 3RW soft starters be connected via PROFIBUS DP instead of PROFINET?

Yes. The SIMATIC PCS 7 Block Library SIRIUS Soft Starter supports both PROFIBUS DP and PROFINET IO communication architectures using identical block interfaces.