SINAMICS S120 Double Motor Module: Which Variant Fits?

What a SINAMICS S120 Double Motor Module Actually Does in Your Cabinet

A line stops because one axis drive has failed, the OEM quotes a 20-week lead time, and the replacement module in the cabinet next door is a SINAMICS S120 double motor module with two outputs you are not sure you can use. That is the situation this article addresses. A double motor module is one Booksize drive unit that carries two independent motor outputs in a single slot, and getting the variant right the first time is the difference between a weekend repair and a month of chasing part numbers.

At Automa.Net we see this constantly in obsolete and legacy Siemens stock: buyers order a double module because it matches the slot, then discover the per-output current rating does not cover both axes. Siemens designed these modules to reduce the width of Booksize Compact and Booksize devices compared with separate single modules, per the SINAMICS S120 product brochure product-family description. Less cabinet width is the point. Two separately rated outputs are the constraint you have to check.

Two axes, one slot: the space argument

Cabinet space is the real driver behind the double module. One Booksize unit, one set of DC-link and DRIVE-CLiQ connections, two motor outputs. In a multi-axis drive lineup where you are stacking modules side by side, that width saving compounds across the cabinet. The trade-off is that both axes now share one module's thermal envelope and one replacement part.

Where the module sits in the drive train

The module takes DC from the DC link and produces three-phase output for each motor. It communicates over DRIVE-CLiQ and reports into the drive configuration in your engineering tool.

For a broader walkthrough of the family, see our companion piece on the Siemens Double Motor Module: Specs, Setup & Sourcing.

Variant Comparison: 5 A, 9 A and 18 A per Output Side by Side

The variants differ mainly in rated current per motor output, and that single number decides whether a module fits your axes. The table below consolidates the ratings and part numbers we can verify from supplier listings and Siemens documentation.

Size each output against its own motor's continuous current, not the combined load, and leave margin for duty cycle and ambient temperature.

Confirm the full part-number string against the manufacturer's documentation before you order.

Decoding the SINAMICS S120 Double Motor Module Part Number

Read the full part number before you order, because it identifies the variant you need.

A common mistake is copying the first ten characters of a part number from a nameplate photo and assuming the rest is generic. It is not. Confirm the full string against Siemens documentation for the exact variant, and where a nameplate is worn, use AutomaSnap to read it rather than guessing.

SINAMICS S120 Motor Module Compatibility: What to Verify Before Ordering

Compatibility failures usually trace to a handful of checks, and skipping any one of them is how a correct-looking module ends up back in its box. Work through these before you commit:

• [ ] Full part number matches, including the suffix after the current digit
• [ ] Rated current per output covers both axes, not just the larger one
• [ ] Form factor fits the slot: Booksize versus Booksize Compact
• [ ] DC-link and motor connections match your existing wiring
• [ ] DRIVE-CLiQ topology and firmware accept the module in your engineering tool
• [ ] Ambient temperature and cabinet cooling support the rated current (derating applies above the reference ambient)

Confirm the firmware level your drive configuration expects, and check that the DRIVE-CLiQ cabling and node addresses in your topology match the replacement. Once the checks pass, browse the Siemens spare parts category to confirm available modules and part numbers.

Verify the ambient temperature and installation spacing against the documentation for the exact variant before you commit.

Find it on Automa.Net →

Buying a Used SINAMICS S120 Double Motor Module: Risks and Checks

Used and surplus modules can be a route when OEM lead times are long, but the checks differ from buying new. Ask for the exact part number, photos of the nameplate, and any test record the seller holds. Confirm the module's current class matches what you need, because a used 9 A unit will not cover an 18 A axis.

Watch out: a module pulled from a working machine and stored without protection can carry handling damage that only shows at commissioning. For a deeper look at whether refurbished industrial electronics are worth it, read our guide to buying refurbished industrial electronics.

Filing an Industrial Automation Parts RFQ That Gets a Useful Answer

An RFQ that gets a fast, useful quote contains the full part number, the quantity, the application, and the deadline. Vague requests like "Siemens double module" get vague answers. Give suppliers the complete string, the axis current requirements, and whether you need new, refurbished, or surplus stock.

A short template works:

Part number: [full string, including suffix]

Quantity: [number]

Required by: [date]

Condition: [new / refurbished / surplus acceptable]

Application: [axis rating and duty]

When you are ready to request a specific variant, submit it through the Request Board.

Match Your Axis Load to the Right Module

Selection comes down to per-axis current, form factor, and availability, in that order. Size each output against its own motor's continuous current, not the combined load. If both axes sit comfortably under the rating with headroom for duty cycle and ambient conditions, the double module is the efficient choice. If one axis runs near the limit, a single module for that axis plus a double module for the lighter pair often beats over-speccing one unit.

Before you commit to a supplier, vet their listings against the part number and rating you have confirmed. When you have the part number and the rating confirmed, AutomaSEARCH lets you search for the exact module across the supplier network.

Frequently Asked Questions

What is a SINAMICS S120 double motor module?

It is a drive module that controls two motors from a single slot in a SINAMICS S120 system. It controls two motors from a single slot in a SINAMICS S120 system and delivers two separate motor outputs, each with its own rated current. Because both axes share one housing, you save cabinet width compared with two single motor modules, but you size each axis separately against its own motor current.

How do I identify the correct SINAMICS S120 double motor module part number?

Start with the nameplate on the failed module and read the full 6SL3120 order number, not just the first block. The digits after 2TE21 encode the current rating and design, so confirm the rating for your exact variant. Write the number down character by character, then confirm the rating against Siemens documentation for that exact variant before you search.

What should I check before buying a used SINAMICS S120 double motor module?

Ask for the exact part number from the unit's own label, a photo of the nameplate, and the firmware or DRIVE-CLiQ identification where available. Ask the seller where the module came from and check its physical condition before you commit. A used module is only a safe swap if the rating matches your motor and the unit is physically undamaged.

Can a discontinued SINAMICS S120 double motor module be replaced with another model?

Sometimes, but not by matching current alone. A higher-rated variant in the same form factor may fit mechanically, yet the configured drive topology, firmware and Safety Integrated settings must still accept it. Confirm any substitution against your drive configuration before you power up. Confirm the substitution in the project before you power up.

Which details should I include in an RFQ for a SINAMICS S120 double motor module?

Give the full order number, the quantity, the machine or line it serves, and the required delivery window. Add the motor ratings on each axis, the cabinet form factor (Booksize or Booksize Compact), and whether you need a new, refurbished or surplus unit. A photo of the old nameplate removes most ambiguity. With those details a supplier can quote a verified match instead of a near-miss, and you avoid a second round of questions.

The hard part is not choosing between 5 A, 9 A, and 18 A. It is finding the exact variant, with the right suffix, in stock before the line stays down another week. Automa.Net connects you to a verified network of suppliers listing real inventory, with AutomaSEARCH for part matching and the Request Board for RFQs when a specific module is scarce. Get started with Automa.Net and turn a discontinued part number into a sourced component.

Find it on Automa.Net →