Siemens sl3120-2te21-8aa3

By Abdullah Zahid
12 min read
Siemens 6SL3120-2TE21-8AA3 SINAMICS S120 booksize double motor module for dual-axis industrial drive applications

Siemens 6SL3120-2TE21-8AA3 SINAMICS S120 Double Motor Module, Booksize Format: Specifications, Selection, and Procurement Guide

If you are specifying or procuring a dual motor drive module for a SINAMICS S120 modular system, the Siemens 6SL3120-2TE21-8AA3 is one of the most searched parts at this power tier — and for good reason. This booksize format Double Motor Module accepts a DC 600V input and delivers regulated 400V 3-phase AC output at 18A per motor channel across two independent motor drives, all from a single compact panel-mounted unit. Whether you are upgrading a multi-motor conveyor line, designing a dual-axis motion system, or retrofitting a legacy dual-drive installation into a tighter enclosure, understanding exactly what this module does — and what it does not do — determines whether this is the right part number for your order.

If you have already confirmed this is the correct part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the 6SL3120-2TE21-8AA3 — and Who Shouldn't

This module is the right choice when all of the following apply to your application:

  • You need independent control of two three-phase AC motors from a single drive module, each drawing up to 18A continuously
  • Your DC bus voltage is 600V — fed from an upstream S120 power module or external rectifier (not raw 400V AC mains)
  • Your output requirement is 400V 3-phase AC per motor channel
  • Your panel uses a ventilated enclosure with internal air circulation — not a sealed or moisture-saturated cabinet
  • Your architecture is built on the SINAMICS S120 modular ecosystem with DRIVE-CLiQ control interface
  • Your panel geometry accommodates the booksize form factor

If your enclosure is sealed or operates in a moisture-heavy environment, the external cooling variant 6SL3121-2TE21-8AA3 is the correct selection. If you only need a single motor at 18A, or two motors at 9A each, other S120 variants will better match your application and budget.

On this page:

What the 6SL3120-2TE21-8AA3 Actually Does in a Drive System

The Siemens 6SL3120-2TE21-8AA3 is a power electronics module within the SINAMICS S120 modular drive family. Its core function is accepting a DC 600V input from an upstream power supply or S120 main power module and converting that DC bus power into regulated 3-phase AC output — 400V at up to 18A — delivered independently to two separate motor loads. This is not a standalone variable frequency drive. It is a modular drive component that requires an S120 CPU or master controller, a DRIVE-CLiQ control connection, and an upstream DC power source to operate.

Each of the two motor channels is independently controllable, meaning Motor 1 and Motor 2 can run at different speeds, follow different ramp profiles, or respond to different command signals — all managed by the supervisory S120 controller through the DRIVE-CLiQ high-speed fieldbus interface. The module supports advanced integrated safety functions including Safe Torque Off rated up to SIL 3 / PLd per ISO 13849-1, reducing the external safety relay hardware required to achieve machinery safety compliance. Internal air cooling handles thermal dissipation under normal duty cycles in a ventilated enclosure, without requiring external cooling infrastructure.

For context on market deployment: Siemens SINAMICS S120 modular drives represent approximately 35–40% of mid-range industrial AC drive deployments in European and North American automotive and packaging sectors, where OEMs and end-users value the scalability, integrated safety, and commissioning standardization this ecosystem provides. Approximately 25–30% of multi-motor production lines in food and beverage and automotive sub-assembly use coordinated dual-motor drives rather than two separate single-motor drives, specifically to reduce panel footprint and simplify supervisory control logic — exactly the scenario this module addresses.

Typical S120 System Architecture with This Module

The 6SL3120-2TE21-8AA3 sits between the DC power distribution bus and the motor loads, acting as the final power conversion stage in the S120 modular signal and power chain. Here is how a typical deployment is structured:

  • AC mains supply feeds into an S120 main power module or external rectifier, which generates the DC 600V bus
  • The DC 600V bus connects to the 6SL3120-2TE21-8AA3 motor module input terminals via an external disconnect or circuit breaker (mandatory — no internal protection)
  • An S120 CPU or control unit connects to the motor module via DRIVE-CLiQ cable, providing real-time speed commands, feedback processing, and safety signal management
  • Motor output terminals (two independent 3-phase sets) connect to Motor 1 and Motor 2 loads — conveyors, pumps, spindles, or other driven equipment
  • Optional motor feedback encoders or thermal sensors connect back to the control unit, completing the closed-loop drive architecture

Where Engineers Deploy the S120 Double Motor Module

In material handling and conveyor systems, the 6SL3120-2TE21-8AA3 allows two conveyor drive motors to operate at different speeds within one modular drive enclosure — eliminating the need for two separate single-motor drives and reducing both panel footprint and wiring complexity. This is one of the most common deployment scenarios in food and beverage packaging lines and automotive parts transfer systems.

In process industries, dual pump control is a primary application: primary and standby pump configurations, counter-rotating pump arrangements, or two parallel pumps with independent flow regulation. Water treatment facilities and process cooling systems frequently use this configuration to maintain redundancy without doubling the drive cabinet size.

For CNC and precision machining, the module supports twin spindle or dual-axis motion — whether coordinated or operating independently. Secondary spindle drives and precision feed mechanisms with independent speed control are typical deployments in machine tool environments where panel space and control architecture simplicity are both constraints.

In retrofit projects, the booksize form factor is a direct enabler: replacing legacy dual-drive systems where the original hardware occupied more panel volume. The modular S120 architecture allows this module to slot into existing DRIVE-CLiQ networks without redesigning the full control hierarchy.

Application Typical Deployment
Conveyor and material handling Two conveyor motors at independent speeds in one panel; food and beverage or automotive lines
Dual pump process control Primary and standby or counter-rotating pumps; water treatment, process cooling, media circulation
CNC / precision machining Twin spindle or dual-axis positioning; independent speed and ramp control per axis
Redundancy architecture Two motors sharing load; automatic failover logic via S120 controller for mission-critical processes
Legacy dual-drive retrofit Compact booksize replacement for two older single-motor drives in space-constrained panels
Packaging machinery Printing, labeling, or precision feed mechanisms with dual independent drive outputs

Key Specifications: What Matters for Your Purchase Decision

Specification Value
Model Number 6SL3120-2TE21-8AA3
Product Family SINAMICS S120
Form Factor Booksize (compact panel-mountable)
DC Input Voltage 600V DC
AC Output Voltage 400V, 3-phase
Output Current Per Motor Channel 18A
Motor Channels 2 independent
Cooling Method Internal air cooling
Communication Interface DRIVE-CLiQ
Safety Rating Up to SIL 3 / PLd (Safe Torque Off)

Full technical specifications are available on the product page at LeadTime.ca.

6SL3120-2TE21-8AA3 vs. S120 Variants: Which Module Do You Actually Need?

Variant Motor Channels / Current Cooling Best For
6SL3120-2TE21-8AA3 (this unit) 2 channels / 18A each Internal air cooling Standard dual-motor applications in ventilated enclosures
6SL3121-2TE21-8AA3 2 channels / 18A each External air cooling Sealed, confined, or high-ambient-temperature environments
6SL3120-2TE21-0AA3 2 channels / 9A each Internal air cooling Lower power dual-motor applications; same booksize form factor
Single Motor S120 Variants 1 channel Variable Retrofit or single-drive applications; no dual channel required
SINAMICS G120 1 channel Variable Greenfield standalone VFD; no S120 infrastructure needed

If your system is built on S120 DRIVE-CLiQ architecture and your enclosure is ventilated, the 6SL3120-2TE21-8AA3 is the correct dual-motor module at this power tier — check current availability at LeadTime.ca.

Expert Verdict: Honest Assessment and Procurement Reality

The 6SL3120-2TE21-8AA3 does exactly what engineers who already operate SINAMICS S120 systems need from a dual-motor module: compact booksize form factor, two fully independent 18A motor channels, integrated STO safety up to SIL 3 / PLd, and native DRIVE-CLiQ communication that eliminates separate fieldbus adapters or gateway hardware. For systems integrators and plant engineers who already have an S120 control infrastructure, this is the logical dual-motor module at this current rating — adding it to an existing DRIVE-CLiQ network is straightforward, and the commissioning toolchain through Siemens STARTER or TIA Portal is well-established.

Where this module has real constraints: it is not a standalone solution. Without an upstream S120 power module delivering DC 600V, it does nothing — greenfield projects without existing S120 infrastructure face significantly higher system cost and integration effort compared to selecting a standalone VFD like the SINAMICS G120. The internal air cooling also draws a hard line: sealed or moisture-heavy enclosures require the 6SL3121-2TE21-8AA3 external cooling variant, and substituting this unit in those environments will result in thermal shutdown under sustained load. If your motor loads exceed 18A per channel, this module is also the wrong tier — full-size S120 drive modules are the correct path.

On the procurement side, the 6SL3120-2TE21-8AA3 is stocked by major automation distributors with typical delivery windows of a few days for in-stock units. Special order or low-volume procurement runs typically fall in the 4–8 week range based on general market patterns. Certified repair and remanufactured units are available with a 2-year market-standard warranty, representing meaningful cost savings at 40–60% below new unit pricing for maintenance-driven purchasing. If you are buying for a multi-system project or need volume pricing, bundling motor modules with upstream power components is a practical option. View current stock and pricing at LeadTime.ca to confirm availability before committing to a build timeline.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

Wiring and Installation: What to Verify Before You Connect

  • Confirm DC 600V is present and stable at the motor module input terminals using a calibrated multimeter before connection — do not assume the upstream power module output is correct without verification
  • Install an external motorized circuit breaker, MCCB, or fused disconnect upstream of the DC input — no internal overcurrent protection exists in this module; external protection is mandatory
  • Connect Motor 1 and Motor 2 to their respective independent 3-phase terminal sets — do not cross-connect or parallel the two motor output channels
  • Route DRIVE-CLiQ cable away from high-voltage power conductors; use shielded industrial-grade cable with proper shield grounding at one end to maintain noise immunity
  • Verify protective earth (PE) bonding to panel frame and both motor enclosures before energizing — proper grounding is required for fault current clearance and EMC compliance per directive 2014/30/EU

Compatible S120 System Components and Expansion

The 6SL3120-2TE21-8AA3 integrates within the broader SINAMICS S120 modular ecosystem. The following system components are part of the typical architecture built around this motor module:

  • S120 Main Power Module — upstream DC 600V bus source; AC/DC conversion stage required before the motor module input
  • S120 CPU / Control Unit — supervisory controller communicating via DRIVE-CLiQ; manages speed commands, fault handling, and safety functions for both motor channels
  • DRIVE-CLiQ Cables — shielded high-speed data cables connecting the motor module to the S120 CPU; industrial-grade, point-to-point connection
  • Motor Encoder Feedback Modules — optional closed-loop speed/position feedback for precision applications; integrates into the DRIVE-CLiQ topology
  • Safety Relay or Safety PLC — external safety input circuit connecting to the STO function; required for SIL 3 / PLd safety architecture implementation

Wrong-Part Checklist: Final Confirmation Before You Order

Before placing your purchase order for the 6SL3120-2TE21-8AA3, confirm every item on this checklist to avoid specification mismatches, installation delays, or equipment damage:

  1. Verify DC bus voltage is 600V; units fed from 400V AC primary power require separate rectifier/power module (common mistake: assuming the 400V output means 400V input)
  2. Confirm two independent motor channels needed or single motor at 18A is sufficient; single-motor applications may suit smaller modules
  3. Check that enclosure accommodates internal air cooling (no sealed or moisture-saturated environment without external cooling upgrade)
  4. Verify DRIVE-CLiQ cable and control interface compatibility with existing S120 master controller (CPU module)
  5. Ensure frame size (booksize) fits panel geometry; full-size modules required for very high-density installations
  6. Confirm load profile; cyclic/intermittent duty may allow lower-cost variant; continuous high-duty may require thermal analysis
  7. Cross-check procurement part number casing (6SL3120-2TE21-8AA3, not sl3120 or other case variants) to avoid specification mismatch

If any item on this checklist raises a question about fit, contact the LeadTime.ca team before ordering — our technical team can confirm the correct variant for your application and check real-time availability worldwide.

Frequently Asked Questions

Can the 6SL3120-2TE21-8AA3 be used without an existing S120 power module?

No. This motor module requires a stable DC 600V input, which must come from an upstream S120 main power module or a separately installed external rectifier. It does not perform AC-to-DC conversion internally. Installing this module without the correct upstream power source will result in no output and potential module fault at energization.

What is the difference between the 6SL3120-2TE21-8AA3 and the 6SL3121-2TE21-8AA3?

Both modules are 18A per channel dual-motor booksize variants within the SINAMICS S120 family. The 6SL3120-2TE21-8AA3 uses internal air cooling and is suitable for standard ventilated panel enclosures. The 6SL3121-2TE21-8AA3 uses external air cooling and is required for sealed, confined, or moisture-heavy environments where internal circulation is insufficient. Selecting the wrong cooling variant for your enclosure type will result in thermal overload under sustained load.

Does this module require a separate safety relay for the STO function, or is safety fully integrated?

The STO (Safe Torque Off) function is integrated into the module and rated up to SIL 3 / PLd per ISO 13849-1. However, an external safety input circuit — typically a safety relay or safety PLC — must provide the STO command signal. The module contains the safety execution hardware; the triggering logic and E-stop circuit must be externally designed and wired per your machinery safety requirements.

What commissioning software is required for the 6SL3120-2TE21-8AA3?

The module is configured using Siemens STARTER software or the SINAMICS S120 add-on within TIA Portal. Motor nameplate data for both Motor 1 and Motor 2 channels must be entered separately, including rated voltage of 400V, rated current of 18A per channel, frequency, pole count, and rated power. Parameter blocks are uploaded to the S120 CPU via DRIVE-CLiQ after configuration.

Is a 9A per channel variant available if 18A is more than my application requires?

Yes. The 6SL3120-2TE21-0AA3 is the 9A per channel dual-motor variant in the same booksize form factor with internal air cooling. If your motor loads draw significantly less than 18A per channel, this lower-rated variant may be the more economical and appropriately sized selection. Verify your motor full-load current and application duty cycle before selecting between the two variants.

What is a realistic lead time for the 6SL3120-2TE21-8AA3 from a distributor?

For in-stock units held at regional distribution warehouses, delivery typically runs a few days. Low-volume or special order procurement follows a 4–8 week lead time based on general market patterns. Certified remanufactured or repaired units are also available with a 2-year market-standard warranty, often with faster availability and a 40–60% cost reduction versus new units. Contact LeadTime.ca directly to confirm current stock status before scheduling your installation timeline.

Why Source the 6SL3120-2TE21-8AA3 from LeadTime.ca

  • Worldwide shipping — LeadTime.ca ships to customers globally, not limited to any single region or market
  • Hard-to-find and short lead-time SINAMICS S120 modules sourced through established distributor and repair networks
  • Volume pricing available for multi-module or system-level orders — contact the team before committing to a bill of materials
  • Fast response on stock confirmation and lead-time quotes — reduces the risk of build timeline disruptions
  • Remanufactured unit availability with 2-year warranty for cost-sensitive maintenance procurement

At-a-Glance Summary

  • Model: 6SL3120-2TE21-8AA3 — SINAMICS S120 Double Motor Module, Booksize Format
  • DC input voltage: 600V — requires upstream S120 power module or external rectifier; no internal AC/DC conversion
  • AC output: 400V 3-phase at 18A per motor channel — two independent channels, total 36A dual-motor capacity
  • Form factor: Booksize — compact panel-mountable; reduced footprint versus two separate single-motor drives
  • Cooling: Internal air cooling — ventilated enclosures only; sealed environments require 6SL3121-2TE21-8AA3
  • Control interface: DRIVE-CLiQ — high-speed point-to-point connection to S120 CPU; no separate fieldbus adapter needed
  • Safety: Up to SIL 3 / PLd — integrated Safe Torque Off (STO); external safety input circuit still required
  • External protection: Mandatory — no internal circuit breaker; install MCB, MCCB, or fused disconnect upstream
  • Lower-power alternative: 6SL3120-2TE21-0AA3 at 9A per channel — same booksize, same cooling, lower cost
  • External cooling alternative: 6SL3121-2TE21-8AA3 — same 18A dual-motor rating; required for sealed or moisture-heavy enclosures
  • Market deployment: SINAMICS S120 represents approximately 35–40% of mid-range industrial AC drive deployments in automotive and packaging sectors in European and North American markets