Siemens

SINAMICS G120 Modular VFD

Siemens' flagship mid-range modular variable frequency drive — a separate Control Unit and Power Module architecture enabling flexible integration with S7-1500 PLCs over PROFINET, with built-in STO safety, BICO signal routing, and TIA Portal drive parameterisation.

Modular CU+PMPROFINET IRTTIA PortalSTO/SS1 Built-in0.37–250 kW
CU250S-2 PN Control Unit PROFINET IRT RDY FLT 1450 RPM BOP-2 display DI DO AI AO terminals SINAMICS PM240-2 Power Module L1 L2 L3 PE 380–480 V AC DC Bus ~565 V DC STO-A STO-B SIL 2 / PLd built-in U V W PE 0–480 V 3φ output Siemens Motor IE3 G120 modular: swap CU for different fieldbus without changing power wiring
Power range0.37–250 kW
ArchitectureModular CU + PM
Fieldbus (CU250S-2 PN)PROFINET IRT
SafetySTO/SS1 SIL 2 built-in
Supply380–480 V AC, 3-phase
SoftwareTIA Portal + Startdrive

Overview

The Siemens SINAMICS G120 is the company's primary modular VFD for industrial applications in the 0.37 kW to 250 kW power range. Its defining characteristic is a two-part architecture separating the Control Unit (CU) — containing the microprocessor, fieldbus interface, and I/O — from the Power Module (PM) containing the rectifier, DC bus, IGBT inverter, and power terminals. This separation means the fieldbus protocol can be changed simply by replacing the Control Unit with a different variant, leaving all power wiring and the motor unchanged.

The CU250S-2 PN is the most common Control Unit for machine automation, providing PROFINET IRT connectivity for direct integration with S7-1500/1200 PLCs over PROFINET. The PROFINET IRT capability enables isochronous communication, making the G120 suitable for coordinated multi-drive speed synchronisation in conveyor and printing applications. An alternative CU250S-2 EtherNet/IP variant serves North American machine builders standardised on Rockwell architectures.

TIA Portal with the Startdrive add-in provides seamless drive parameterisation directly from the S7-1500 project. Drive parameters are visible in TIA Portal's project tree, shared tag addresses simplify control logic, and the same online diagnostics session covers both PLC and drives. This integration is a major productivity advantage over traditional drive commissioning with standalone PC tools and manual parameter entry.

Variable-frequency drive (VFD) unit, the same product class as the Siemens SINAMICS G120 for sensorless vector control of AC induction motors
Compact variable-frequency drive (VFD) unit for AC motor speed control.

Key Features

  • Modular CU+PM — fieldbus swap without rewiring
    Separating the Control Unit from the Power Module allows the fieldbus to be changed (e.g., PROFINET to EtherNet/IP) simply by swapping the CU — all power wiring, cable screen connections, and motor connections remain unchanged. This is a major advantage for OEMs building machines for different market regions with different preferred fieldbus standards.
  • TIA Portal Startdrive integration
    Startdrive is the TIA Portal add-in for SINAMICS drive engineering. It places the G120's full parameter set in the TIA Portal project tree, enables online drive commissioning through the PROFINET connection, and generates Startdrive reports for FAT documentation — all within the same engineering environment used for the S7-1500 PLC.
  • BICO signal routing
    BICO (Binector Connector) is Siemens' internal signal routing system — any output signal (speed actual, torque, current, status bit) can be connected to any input (setpoint, enable, PI controller input) through parameter settings without hardware wiring changes. BICO enables sophisticated control structures — cascaded PI loops, load sharing, electronic gearbox ratios — entirely within the drive firmware.
  • STO/SS1 Safety — SIL 2, PLd
    Both PM240-2 and PM250 Power Modules include hardwired STO (Safe Torque Off) terminals certified to SIL 2 / PLd without any additional safety relay. The CU250S-2 Control Unit adds SS1, SS2, SLS, SOS, SDI, and SBC safety functions (SIL 3 / PLe) via PROFIsafe over PROFINET — the full safety function suite within the same drive hardware.

Technical Specifications

SINAMICS G120 — CU250S-2 PN + PM240-2 Specifications
Power range (PM240-2)0.37–132 kW at 400 V; 0.55–250 kW at 690 V
Input voltage380–480 V AC ±10% (PM240-2); 500–690 V AC (PM260)
Output frequency0–650 Hz (vector); 0–300 Hz (V/Hz)
Control modesV/Hz (sensorless), Vector (sensorless), Vector (encoder)
Fieldbus (CU250S-2 PN)PROFINET RT and IRT, PROFIsafe (via PN)
Fieldbus alternativesCU240E-2 (PROFIBUS DP), CU250S-2 DP, CU250S-2 EtherNet/IP
Safety (PM built-in)STO SIL 2 / PLd (hardwired terminals)
Safety (CU250S-2)STO/SS1/SS2/SLS/SOS/SDI/SBC — SIL 3 / PLe via PROFIsafe
Degree of protectionIP20 (standard); IP55 (Push-through / Chassis)
Ambient temperature−10 °C to +50 °C (derating above 40 °C)
Commissioning SWTIA Portal V17+ with Startdrive V17+; STARTER (standalone)

Typical Applications

  • Conveyor systems: Multi-drive speed synchronisation over PROFINET IRT; line topology using PM built-in PROFINET switch
  • Pump and fan control: V/Hz energy-saving mode with integrated PID pressure/flow control; sleep/wake on demand
  • Compressor control: Speed control with torque limiting; envelope monitoring via BICO signal routing
  • Textile machinery: Encoder-based vector control for precise winder tension in thread and film winding
  • HVAC AHUs: G120C (compact variant) without separate CU for cost-optimised fan and pump applications

Sources & Further Reading

  • Siemens — SINAMICS G120 Operating Instructions (A5E03461182)
  • Siemens — TIA Portal Startdrive Getting Started Guide
  • IEC 61800-5-2:2016 — Adjustable speed drives: Functional safety
  • PROFINET Specification — PROFINET IRT (PROFIBUS International)