Siemens 6SL3120-2TE21-8AA3 AC Servo Drive – SINAMICS S120

Siemens 6SL3120-2TE21-8AA3 Double Motor Module — Dual-Axis Torque Control Architecture in SINAMICS S120 Booksize Format

The Siemens 6SL3120-2TE21-8AA3 is a Double Motor Module within the SINAMICS S120 booksize drive line, designed to deliver independent field-oriented vector control across two servo axes from a single hardware slot. Each axis operates on a dedicated IGBT inverter bridge, sharing a common DC link rail at 600 V DC nominal. This architecture eliminates the need for two separate single-axis modules in dual-axis machine configurations, reducing panel width by approximately 40 mm while maintaining full per-axis current capacity of 18 A continuous.

In closed-loop servo applications — CNC spindle coordination, multi-axis gantry positioning, or synchronized winding tension control — the 6SL3120-2TE21-8AA3 maintains torque bandwidth sufficient for dynamic load changes without cross-axis interference. The internal current regulators on each axis operate at a 125 µs cycle time, independent of the position controller cycle running on the upstream Control Unit (CU320-2 or CU310-2). This decoupling ensures that a transient disturbance on Axis 1 does not propagate latency into the Axis 2 current loop.

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Technical Parameters

Hardware Logical Analysis

Dual IGBT Inverter Bridge Architecture: The 6SL3120-2TE21-8AA3 integrates two fully independent three-phase IGBT inverter bridges within a single booksize housing. Each bridge is driven by a dedicated gate driver circuit with isolated power supply, preventing a gate fault on one axis from propagating shoot-through conditions to the adjacent bridge. The IGBT modules are rated for the 600 V DC bus with a derating margin that accommodates regenerative voltage spikes up to approximately 720 V DC during rapid deceleration without triggering overvoltage protection.

EMC Design and Conducted Emission Suppression: The module’s internal PCB layout separates high-frequency switching nodes from the DRIVE-CLiQ signal traces using a ground plane partition strategy. The DC link capacitor bank is positioned physically close to the IGBT collector rails to minimize parasitic inductance in the commutation loop — a direct factor in reducing dV/dt-induced common-mode current that would otherwise couple into motor cable shields. The module meets EN 61800-3 Category C2 conducted emission limits without an external EMC filter when used with shielded motor cables ≤ 25 m.

Thermal Management and Derating Logic: An NTC thermistor mounted on the IGBT heatsink feeds the internal thermal model. The firmware implements a two-stage thermal response: at 80% of the thermal limit, switching frequency is automatically reduced from 8 kHz to 4 kHz to lower switching losses; at 95%, output current is linearly derated. This prevents hard thermal shutdown in applications with intermittent overload cycles, maintaining axis availability at the cost of a controlled performance reduction rather than a fault trip.

DRIVE-CLiQ Topology and Automatic Parameterization: Each DRIVE-CLiQ port on the module contains an embedded Electronic Nameplate (ENP) chip that stores the module’s rated data, firmware version, and serial number. When connected to a CU320-2, the Control Unit reads the ENP during power-up and automatically populates the drive object parameters — rated current, switching frequency limits, and STO wiring topology — without manual entry. This reduces commissioning errors in multi-axis systems where parameter mismatches between the motor module and the control unit are a common source of F07801 and F07802 fault codes.

STO Safety Circuit Implementation: The Safe Torque Off function is implemented via a dual-channel hardware path that disables the gate driver enable signals for both IGBT bridges simultaneously. The STO circuit is galvanically isolated from the 24 V control supply and operates independently of the firmware — meaning STO remains functional even during a CPU fault or firmware hang on the Control Unit. Response time from STO input de-energization to gate pulse inhibit is < 2 ms, meeting the stopping time requirements for Category 0 stop per IEC 60204-1.

System Integration Benefits

• Deterministic dual-axis synchronization: Both axes share the same DRIVE-CLiQ isochronous clock domain, ensuring position setpoints for Axis 1 and Axis 2 are applied within the same servo cycle — critical for electronic gearing and cam synchronization applications.
• Reduced DC bus wiring complexity: A single DC link connection feeds both inverter bridges. In a multi-module booksize rack, the shared DC bus bar eliminates the need for individual DC fusing per axis, reducing BOM cost and panel assembly time.
• Integrated diagnostic transparency: The module reports per-axis DC link voltage, output current (all three phases), IGBT junction temperature, and STO status as process data objects accessible via PROFIdrive telegrams — no additional measurement hardware required for commissioning diagnostics.
• Firmware-level fault isolation: A fault on Axis 1 (e.g., motor overcurrent F30001) does not automatically propagate a fault to Axis 2. The Control Unit can be configured to maintain Axis 2 operation while Axis 1 is in fault state, enabling partial machine availability in non-safety-critical axes.
• Plug-in motor encoder feedback: Compatible with SMC (Sensor Module Cabinet-Mounted) and SME (Sensor Module External) for resolvers, EnDat 2.1/2.2, SSI, and HTL/TTL incremental encoders — allowing the same module to drive motors with different feedback technologies across the two axes.
• Energy recovery via shared DC bus: Regenerative braking energy from one axis is directly available to the other axis on the same DC bus segment before it reaches the Line Module. In applications with alternating acceleration/deceleration profiles across axes, this reduces net energy drawn from the supply by up to 15–20% compared to individual single-axis modules with separate DC buses.
• TIA Portal V16+ integration: The module is fully supported in the SINAMICS S120 GSD/GSDML device library within TIA Portal, enabling hardware configuration, parameter download, and online diagnostics from a single engineering environment without switching to STARTER.
• Scalable safety expansion: The STO inputs on the 6SL3120-2TE21-8AA3 can be wired to a SIMATIC Safety Controller (F-CPU) via PROFIsafe, enabling software-controlled STO activation without additional safety relays — reducing the safety circuit component count and simplifying TÜV validation documentation.

Quality Assurance & Global Logistics

Every Siemens 6SL3120-2TE21-8AA3 unit dispatched from our Xiamen facility is a genuine Siemens AG manufactured component. Units are stored in a temperature-controlled warehouse (18–25 °C, < 60% RH) in original or equivalent ESD-protective packaging. Prior to shipment, each module undergoes a visual inspection checklist covering label authenticity, connector pin condition, housing integrity, and firmware version verification against the Siemens product lifecycle database.

Shipments originate from Xiamen, China with the following logistics options:

• Express air freight: DHL Express / FedEx International Priority — transit time 3–5 business days to EU, USA, Southeast Asia, and Middle East destinations.
• Economy air freight: 5–10 business days for cost-sensitive orders.
• Sea freight consolidation: Available for bulk orders ≥ 10 units; transit time varies by destination port.
• Export documentation: Commercial invoice, packing list, Certificate of Origin (CO), and HS Code 8537.10 declaration provided as standard. FORM E (ASEAN-China FTA) available on request.
• Warranty: 12 months from shipment date. DOA units replaced or credited within 7 business days of confirmed receipt of returned goods.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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