The Siemens MICROMASTER 440 (MM440) is a variable frequency drive used to control AC motor speed and performance in industrial machinery. For maintenance teams and purchasing managers, however, finding an MM440 today involves more than checking its power rating. The series has entered the product phase-out and cancellation process, so confirming the exact order number, product condition, and application requirements is essential before ordering a replacement.
This guide explains how to identify an existing MM440, check the specifications that affect compatibility, and compare repair, like-for-like replacement, and migration to a newer drive platform. It also outlines the information buyers should prepare when requesting a quotation from CHENTUO.
Quick answer: Start with the complete Siemens article number, also known as the MLFB, on the drive nameplate. Verify voltage, rated output current, load duty, control interfaces, and accessories before ordering. If you are considering SINAMICS G120, treat it as a migration project that requires compatibility checks rather than assuming a direct replacement.
1. What Is the Siemens MICROMASTER 440 and Where Is It Used?
Understanding the MM440 as a Variable Frequency Drive
The MICROMASTER 440 is an AC drive designed to regulate motor speed and support different industrial control requirements. It adjusts the frequency and voltage supplied to an AC motor according to the configured operating conditions.
Unlike a fixed-speed motor starter, a VFD allows the machine to change speed during operation. Depending on the configuration and application, this can support controlled acceleration, deceleration, and more demanding motor control.
If you need a general explanation of drive operation and selection principles, see our guide to what a variable frequency drive is and how to choose one. This article focuses specifically on MM440 identification, sourcing, and replacement decisions.
Common Industrial Applications
MM440 drives may be encountered in existing conveyor systems, packaging machinery, textile equipment, pumps, fans, and other industrial machines.
The selection requirements differ by application. A conveyor may need sufficient starting torque and controlled deceleration. A pump may place greater emphasis on continuous operation and process speed regulation. A machine with frequent stops may require closer attention to braking performance and operating cycles.
These examples describe typical application requirements, not a guarantee that every MM440 configuration is suitable for every machine.
Key Control Capabilities at a Glance
MM440 supports different motor control approaches, including V/f control and vector control. The appropriate method depends on the required speed and torque behavior. Encoder feedback, where needed, must be assessed against the relevant drive configuration and feedback hardware.
For a replacement project, do not select a drive based on its control mode alone. Also check the existing I/O signals, PLC communication, braking arrangement, and parameter configuration.
2. Is the Siemens MICROMASTER 440 Discontinued?
Understanding the MICROMASTER 440 Product Lifecycle
Siemens announced the withdrawal of MICROMASTER 420, 430, and 440 standard drives from the active marketing phase, effective October 1, 2017. A subsequent notice announced the cancellation of the MICROMASTER 4 drive family, including options, selected accessories, and spare parts, effective October 1, 2019.
These dates establish the series' lifecycle history. They do not prove that every individual part number is unavailable everywhere today. Siemens catalog records may identify particular configurations as spare parts, and product status can differ by article number.
For the official notices, consult the Siemens product lifecycle information. Always verify the exact part number rather than relying only on the family name.
What Discontinued Status Means for Maintenance and Purchasing
For an existing installation, lifecycle status affects spare parts planning, maintenance decisions, and the time required to restore equipment after a failure.
A replacement MM440 may still be obtainable through a suitable supplier, but buyers should confirm the exact model, product condition, included accessories, and applicable warranty terms. A listing or a general statement that a product is available does not establish that a specific unit is ready to ship.
For critical equipment, compare the cost and risk of sourcing the original model with the potential engineering work involved in moving to a newer platform.
When Should You Consider a Replacement or Migration?
Consider a replacement assessment when a drive fails repeatedly, sourcing becomes uncertain, production downtime is costly, or the plant is planning a wider control system upgrade.
An immediate replacement is not always necessary. If the existing drive operates reliably and the maintenance team has a workable spare parts strategy, continued operation may remain practical.
The decision should reflect machine criticality, repair feasibility, spare parts availability, and the expected service life of the wider system.
3. How to Identify the Correct MICROMASTER 440 Model Number
Find the Full 6SE6440 Order Number
The complete Siemens article number is one of the most useful identifiers when sourcing an MM440. Many models use the 6SE6440 prefix, but the remaining characters distinguish specific configurations.
For example, Siemens lists 6SE6440-2AD32-2DA1 as an MM440 configuration with a 380 to 480 V three-phase supply class, a built-in Class A filter, and different constant torque and square-law torque ratings. Those details belong to that specific order number and should not be generalized to the whole family.
You can review the official Siemens catalog entry for this example.
Do not request a replacement using only a description such as "MM440, 22 kW." Record the complete article number, including every suffix.
Read the Drive Nameplate Before Ordering
Locate the drive nameplate and record the available identification and rating information. If the label is difficult to read, take a clear photograph without removing covers or exposing yourself to electrical hazards.
Prioritize these details:
- Complete article number or MLFB.
- Input voltage, phase, and frequency.
- Rated output current and power rating.
- Relevant product and hardware identification details.
- Any additional labels that identify the installed configuration.
Compare the drive nameplate with the motor nameplate. They provide different information: the drive label identifies the installed converter, while the motor label helps establish the electrical and operating requirements of the load.
Check the Accessories That May Affect Compatibility
The drive body is only part of the installed system. Check whether the existing installation uses a Basic Operator Panel (BOP), Advanced Operator Panel (AOP), communication modules, braking components, or encoder feedback hardware.
Do not assume that a replacement includes the same accessories as the original unit. Confirm the exact product description and the scope of supply before placing an order.
For migration projects, also document the PLC interface and control wiring. These details may affect the replacement configuration even when the motor rating remains unchanged.
4. MICROMASTER 440 Specifications That Matter for Selection
Voltage, Rated Current and Power Range
MM440 configurations were produced for different supply voltage classes, including 200 to 240 V, 380 to 480 V, and 500 to 600 V variants. These are family-level examples, not interchangeable supply options for every model.
Check three separate values before ordering:
- Input voltage: Must suit the site's electrical supply.
- Motor power: Useful for initial screening, but not sufficient for final selection.
- Rated output current: Must support the motor and required operating duty.
A drive with the same kW rating as the existing unit may still be unsuitable if its voltage class, output current, or overload capability does not meet the application requirements.
Use the Siemens MICROMASTER 440 operating instructions and the documentation for the exact article number to confirm technical values.
Constant Torque vs. Variable Torque Ratings
Constant torque (CT) and variable torque (VT) describe different load and rating conditions. The correct rating depends on how the machine operates, not simply on its industry or motor power.
Conveyors and mixers may require sustained torque or higher starting torque. Centrifugal pumps and fans commonly have variable torque characteristics, although the actual operating conditions still need to be checked.
Some MM440 configurations have different power ratings for constant torque and square-law torque operation. Compare the appropriate output current, overload capability, and duty requirements rather than selecting a drive based on the highest power figure in a catalog.
Vector Control, I/O and Communication Interfaces
Confirm how the existing drive receives commands and exchanges information with the machine controller.
Check whether the application uses terminal control, digital inputs, analog references, a fieldbus connection, or feedback devices. Where a communication module is installed, record its exact type and the protocol used by the PLC.
A replacement must satisfy the machine's functional requirements, not merely provide a similar headline feature. Confirm the relevant interfaces and configuration against the manufacturer's documentation.
Braking, EMC and Installation Requirements
Review the installation conditions before confirming a replacement. Important factors include braking requirements, EMC filtering, grounding, enclosure protection, cabinet dimensions, ventilation, ambient temperature, and any applicable derating conditions.
A machine that decelerates frequently may need a different braking assessment from one that runs at a relatively stable speed. Likewise, a drive that fits electrically may still require cabinet modifications if its dimensions or cooling requirements differ.
Braking and safety functions must also be evaluated separately. A drive's braking capability should not be treated as proof that the machine's required safety stopping function is satisfied.
5. How to Select or Verify an MM440 Drive for Your Application
Start with Motor and Load Requirements
Begin with the existing motor nameplate and operating conditions. Record supply voltage, motor current, rated power, frequency, and the load's starting and running requirements.
Then establish how the machine operates. Consider acceleration time, deceleration frequency, continuous duty, overload requirements, and whether the process needs precise speed or torque control.
Use these details to compare candidate drives with the correct Siemens technical documentation. If the original configuration is unknown, gather the available information before assuming a replacement rating.
Match the Control and Installation Requirements
After checking the electrical ratings, compare the existing control architecture and physical installation.
Confirm the required I/O, PLC communication, feedback devices, braking components, mounting dimensions, and cooling arrangements. Review the existing parameter backup and control logic if available.
This step is particularly important when moving to a different drive family. A technically suitable replacement may still require wiring changes, parameter configuration, or commissioning work.
Example A: A Conveyor with Frequent Deceleration
Consider a conveyor that starts and stops frequently and carries a load with significant inertia. Matching the original drive's power rating is only the first check.
The assessment should also cover deceleration time, stopping frequency, load behavior, and the braking arrangement. The engineering team can then determine whether the proposed drive and braking components meet the application's requirements.
The purchasing lesson is straightforward: provide operating details alongside the original part number.
Example B: A Pump in Continuous Operation
A pump that runs for long periods at varying speeds presents a different selection problem. The assessment should focus on the actual load characteristics, required output current, control requirements, and operating environment.
Do not assume that every pump automatically uses a variable torque rating or that a drive with a matching kW value will be suitable. Verify the motor and application data against the candidate model's ratings.
These examples illustrate why application requirements should guide model verification rather than the other way around.
6. Repair, Like-for-Like Replacement or Upgrade: Which Route Makes Sense?
Option 1: Repair the Existing Drive
Repair may be worth evaluating when the fault can be diagnosed, suitable repair capability is available, and the expected repair time fits the plant's downtime limits.
Before choosing this route, consider the condition of the drive, the availability of replacement components, the required post-repair testing, and the consequences of another failure.
Repair should be based on a technical assessment rather than an assumption that it will always be cheaper than replacement.
Option 2: Source the Same MM440 Part Number
A like-for-like replacement aims to source the same complete article number as the installed drive. This can reduce some configuration changes, but it does not guarantee that the new unit can be installed without checks.
Verify the product condition, suffix, included accessories, ratings, and parameter requirements. Also confirm the supplier's documentation, warranty conditions, and actual availability.
For older equipment, distinguish between new original stock, used products, and refurbished units. These categories should not be treated as equivalent.
Option 3: Migrate to a Newer Drive Platform
Migration may be appropriate when long-term support, system modernization, or future maintenance planning makes continued reliance on the old platform less attractive.
However, a new drive may require changes to the electrical installation, control interface, cabinet layout, parameters, or commissioning process. The engineering effort should be considered alongside the hardware price.
The right route depends on machine requirements, downtime tolerance, technical compatibility, and sourcing conditions. No single option is best for every MM440 installation.
7. Can a SINAMICS G120 Replace a MICROMASTER 440?
Why G120 Is a Migration Option, Not a Universal Drop-In Replacement
SINAMICS G120 is a possible platform to evaluate when planning an MM440 migration. However, a G120 configuration should not be treated as a universal direct replacement.
The G120 family uses a modular architecture in relevant configurations, with components such as a Power Module and Control Unit. The selected components, accessories, and control arrangements must suit the application.
Differences in dimensions, terminals, communication, parameterization, braking, and control functions can affect the migration. A similar power rating does not establish complete compatibility.
Key Compatibility Checks Before Migration
Before choosing a G120 configuration, compare the existing installation with the proposed system across these areas:
|
Compatibility area |
What to verify |
|
Electrical ratings |
Supply voltage, motor current, duty, and overload requirements |
|
Drive configuration |
Suitable Power Module, Control Unit, and required accessories |
|
Control system |
I/O, PLC interface, fieldbus, and feedback requirements |
|
Braking |
Required braking performance and associated hardware |
|
Mechanical installation |
Dimensions, mounting, wiring, and ventilation |
|
Parameters |
Available backups, control logic, and configuration changes |
|
Safety |
Existing machine safety requirements and validation process |
For detailed differences between G120 Power Module families, see CHENTUO's guide to Siemens SINAMICS G120 Power Modules. That article covers module selection in more detail, while this guide focuses on the migration from an existing MM440 system.
A Practical MM440 to G120 Migration Workflow
A migration assessment should begin by documenting the installed drive, motor, control wiring, communication settings, and operating requirements.
Next, define the required performance and select a candidate G120 configuration for verification. Review the proposed components, installation requirements, control integration, braking, and safety functions before implementation.
The final stage involves installation, configuration, commissioning, and functional validation by qualified personnel. Existing MM440 parameters should not be assumed to transfer directly to the new platform.
When to Seek Engineering Support
Professional engineering review is especially important when the machine uses demanding braking, encoder feedback, complex PLC integration, or safety-related functions.
Provide the existing drive article number, motor nameplate, control system details, and application requirements. This gives the engineering team a basis for assessing the proposed configuration instead of relying on a series-level comparison.
For buyers evaluating a new platform, CHENTUO's SINAMICS G120 product information provides a starting point for further product research.
8. What to Check When an MM440 Drive Fails
Record Fault Codes and Operating Conditions
Before requesting repair or replacement, record the exact fault or alarm code displayed by the drive. Note when the problem occurs, such as during startup, acceleration, normal operation, or deceleration.
Also record the load condition, recent maintenance work, parameter changes, and any changes to the electrical installation. These details help distinguish a recurring operational problem from an isolated event.
Distinguish Drive Failure from System-Level Problems
A drive fault does not automatically prove that the converter itself has failed. Supply conditions, motor problems, wiring changes, control signals, and mechanical load issues may also contribute.
Qualified personnel should assess the available evidence and follow the manufacturer's safety procedures. Do not open or test energized equipment unless authorized and properly equipped.
Prepare Evidence Before Requesting a Replacement
Collect the full drive nameplate, motor nameplate, fault history, and relevant installation photographs. If the original parameters are available, preserve a backup for technical review.
This information supports both fault assessment and replacement selection. It can also reduce the risk of ordering a drive that matches the series name but not the installed configuration.
9. How to Request the Right MICROMASTER 440 Drive or Replacement Quote
Information to Include in Your RFQ
A useful MM440 inquiry should include:
- Complete Siemens article number or MLFB.
- Clear drive nameplate photograph.
- Required quantity and product condition.
- Motor nameplate and application details.
- Supply voltage and control system requirements.
- Required accessories and communication options.
- Destination country and required delivery date.
- Whether you need the same model or are considering a migration.
If the original part number is unclear, explain what is known and attach photographs. It is better to identify missing information early than to assume a model based on incomplete details.
What to Verify Before Confirming an Order
Confirm the exact article number, product condition, included accessories, and the scope of supply. Ask which inspection or testing records are available and clarify the applicable warranty and delivery terms.
For a migration, separately confirm the proposed configuration and the engineering work required. Hardware supply and successful system integration are different deliverables.
Request a Model and Availability Check from CHENTUO
CHENTUO supplies industrial automation products, including Siemens variable frequency drives, and provides an inquiry channel for product and quotation requests.
Send your complete MM440 part number, quantity, nameplate photograph, and application requirements through the CHENTUO Request a Quote page. If you are considering a G120 migration, state that clearly so the request can be assessed as a replacement project rather than a simple same-model purchase.
FAQ
Is the Siemens MICROMASTER 440 discontinued?
What replaces the Siemens MICROMASTER 440?
Can a SINAMICS G120 directly replace an MM440?
How do I identify my Siemens MM440 part number?
What is the difference between CT and VT ratings?
Does an MM440 include a BOP or AOP?
Conclusion: Confirm the Drive Requirements Before Ordering
Selecting a Siemens MICROMASTER 440 replacement starts with identifying the exact installed model and verifying the electrical, control, and application requirements. Depending on the equipment's condition and maintenance strategy, repair, sourcing the same model, or migrating to SINAMICS G120 may each deserve consideration.
Before ordering, gather the complete article number, nameplate photographs, motor data, and relevant control details. If you need help checking a model or discussing replacement options, contact CHENTUO through the inquiry page with your available technical information.
