Replacement Servo Drive Module 6SL3120-2TE21-8AA3 Siemens OEM

Siemens 6SL3120-2TE21-8AA3 | SINAMICS S120 Booksize Double Motor Module — 2×18A / 600V DC / Drive-CLiQ / Safety Integrated

Two Servo Axes, One Booksize Slot

The 6SL3120-2TE21-8AA3 is a Double Motor Module from the SINAMICS S120 booksize series — a single module that drives two independent servo axes at 18A each from one cabinet slot. The module draws from the shared DC bus established by the upstream Line Module, converts 600V DC into two independent 3-phase 400V AC outputs, and communicates with the Control Unit via Drive-CLiQ.

Both channels operate fully independently — different motor types, speeds, and load profiles are supported. The only shared element is the DC bus input. A two-axis machine section (X and Y on a machining centre, two adjacent joints on a robot arm, two axes on a packaging line) consolidates into one module width rather than two separate single-axis modules, reducing cabinet slots, simplifying DC bus connections, and halving the Drive-CLiQ connections from this section.

Key Specifications

Drive-CLiQ — Automatic Module Identification

Each S120 module contains an electronic type plate that the Control Unit reads via Drive-CLiQ at startup — hardware identification is automatic, without manual parameter entry. For the 6SL3120-2TE21-8AA3, this means commissioning a new module or swapping a failed one takes minutes. The Drive-CLiQ cable pre-cut to the module width for adjacent booksize connection is included with the module.

The AA3 hardware generation and its direct successor AC0 (6SL3120-2TE21-8AC0) share identical electrical specifications — 2×18A, 600V DC input, booksize format, same Drive-CLiQ interface. Drive-CLiQ's automatic type plate identification handles both generations transparently, making the AC0 a straightforward hardware swap for AA3 units when AA3 stock is exhausted.

Extended Safety Integrated — No External Safety Relays

Safety functions run internally within the drive without requiring external safety relays or PLC safety modules:

• STO (Safe Torque Off) — removes motor power without a mechanical brake
• SS1 (Safe Stop 1) — controlled deceleration then STO
• SLS (Safely Limited Speed) — monitored speed limit
• SBC (Safe Brake Control) — safe brake activation

Performance Level d (PL d), Category 3 per EN ISO 13849-1. The safety logic runs in the drive, reducing safety chain wiring complexity and component count.

FAQ

Q1: Can both channels drive completely different motors with different ratings?

Yes. Both channels operate independently with their own control loop and parameter set in the Control Unit. Different motor types, speeds, and load profiles are supported simultaneously. The only shared element is the DC bus input — neither motor's continuous current demand should exceed 18A and the combined peak demand must stay within DC link capacity.

Q2: What Control Unit pairs with this module?

Any SINAMICS S120-compatible Control Unit: CU320-2 (multi-axis systems), CU310-2 (simpler configurations), SIMOTION D, and SINUMERIK integrated control units. The Control Unit must support Extended Safety Integrated to utilise the module's safety functions.

Q3: How does the AA3 generation compare to the AC0 replacement?

Electrically and functionally identical — same 2×18A rating, booksize format, Drive-CLiQ, and Safety Integrated feature set. The AC0 incorporates component-level hardware updates. Drive-CLiQ's automatic type plate identification means no parameter changes when swapping between AA3 and AC0 in an existing system.

Q4: Is the Drive-CLiQ inter-module cable included?

Yes. Each module ships with a Drive-CLiQ cable pre-cut to connect it to adjacent modules in the booksize stack. Cables to the Control Unit or non-adjacent components must be ordered separately.

Q5: For a refurbished unit, what should be verified before commissioning?

DC bus capacitors should have been replaced (electrolytic capacitors degrade with age regardless of operating hours). Verify Drive-CLiQ interface function and confirm safety function operation (STO at minimum) through a controlled test. Request documentation of replaced components and testing procedures from the supplier.