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Allen-Bradley MPL-B680F-MJ72AA Servo Motor — Detailed Product Guide

1. Product Overview

The Allen-Bradley MPL-B680F-MJ72AA is a high-power, low-inertia AC rotary servo motor belonging to the MP-Series MPL low-inertia brushless servo motor family. It is designed for motion-control systems that need a combination of substantial continuous torque, high peak torque capability, relatively high operating speed, accurate position feedback, and a mechanically robust motor construction.

The MPL-B680F-MJ72AA is particularly suited to demanding industrial motion applications where the motor must repeatedly accelerate, decelerate, position, and reverse a substantial mechanical load. Its large 215 mm frame and long 203.2 mm motor stack give it considerably more torque capability than the shorter MPL frame variants.

This particular model uses a 3000 rpm-class speed rating, multi-turn absolute feedback, a keyed shaft, and no integral holding brake. That combination makes it a practical choice for machine axes where multi-turn position information is important and where an electrically released holding brake is not required.

The motor is also part of the low-inertia MPL design philosophy. Compared with conventional high-inertia industrial motors, a low-inertia servo motor can provide faster dynamic response when the servo system is properly matched to the driven load and configured with an appropriate servo drive.

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2. Basic Product Information

The numerical values above should be treated as engineering-class/typical values rather than a substitute for the exact motor and drive configuration data used for final machine design. Actual system performance depends on the servo drive, feedback configuration, ambient conditions, cable arrangement, load profile, duty cycle, and installation method.

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3. Brand and Product Series

Brand: Allen-Bradley

Product Series: MP-Series

Motor Family: MPL Low-Inertia Brushless Servo Motors

The MPL family is designed around the requirements of modern industrial motion control. Instead of treating the motor simply as a rotating power source, the design focuses on dynamic response, feedback accuracy, acceleration capability, and compatibility with servo-control systems.

The MPL-B680F-MJ72AA belongs to the larger-frame end of the MPL family. Its 215 mm frame and approximately 203.2 mm stack length provide a substantial electromagnetic package capable of delivering high continuous torque while maintaining the characteristics expected from a servo motor.

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4. Model Number Interpretation

The model designation MPL-B680F-MJ72AA contains useful information about the motor configuration.

The most important distinction in this model is the combination of F speed class + M multi-turn feedback + J keyed shaft + 2 no-brake configuration.

That combination is useful for applications where the machine needs absolute multi-turn position information but does not need a motor-mounted holding brake.

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5. Detailed Technical Specifications

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6. Dimensions

The physical size of the MPL-B680F-MJ72AA is an important consideration during machine design because this is a relatively large servo motor.

The 215 mm frame provides the mechanical mounting reference, while the 203.2 mm stack length identifies the long motor body used for this torque class.

When designing a cabinet or machine frame, the complete motor envelope should be checked rather than relying only on the frame and stack dimensions. Connector clearance, cable bending radius, shaft extension, coupling dimensions, and maintenance access can all increase the actual installation space required.

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7. Weight

The MPL-B680F-MJ72AA is approximately 40.4 kg in the corresponding configuration class.

At roughly 40 kg, this is not a small machine motor. Mechanical installation should therefore be planned carefully, especially when the motor is installed vertically, inside a machine enclosure, or at a location where technicians need to remove it for maintenance.

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8. Torque Performance

One of the strongest characteristics of the MPL-B680F-MJ72AA is its torque capability.

The motor provides approximately 60 N·m of continuous torque class capability, while its peak torque capability is approximately 108.5 N·m class.

The difference between continuous and peak torque is particularly important in servo applications.

Continuous torque relates to the motor’s ability to produce torque over sustained operation under appropriate thermal conditions. Peak torque is more relevant during short acceleration, deceleration, positioning, or disturbance events.

For example, a machine may operate continuously at a moderate torque level but require a much larger torque for a short period when accelerating a heavy roller, indexing a large mechanism, or rapidly changing direction.

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9. Rated Speed and Power

The F configuration places this motor in the approximately 3000 rpm speed class.

The rated output is approximately 7.5 kW class, which makes this motor suitable for applications requiring substantial mechanical power while retaining servo-control characteristics.

The 3000 rpm class is a useful compromise between torque and speed. It is faster than a 2000 rpm torque-oriented version while still providing substantial torque for heavy-duty servo axes.

This makes the MPL-B680F-MJ72AA particularly interesting when a machine requires both significant mechanical power and reasonably high axis speed.

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10. Low-Inertia Motor Design

The MPL family is designed around a low-inertia servo motor concept.

Rotor inertia is approximately 0.00775 kg·m² for this model class.

Low rotor inertia can be beneficial when the motor needs to accelerate and decelerate frequently. A servo system can potentially respond more quickly when the motor and load inertia are appropriately matched.

This is particularly useful for machines that repeatedly perform movements such as:

• Start → accelerate → position → stop.
• Forward → reverse → position.
• Index → stop → index again.
• Rapid acceleration → constant-speed movement → rapid deceleration.

However, low motor inertia does not automatically mean that every application will have ideal dynamic performance. Load inertia, gearbox ratio, coupling stiffness, mechanical backlash, friction, and servo tuning all have a major effect on the final machine response.

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11. Multi-Turn Absolute Feedback

The MPL-B680F-MJ72AA uses multi-turn absolute feedback.

This is one of the most important differences between this model and the corresponding single-turn versions.

A multi-turn absolute encoder can maintain positional information across multiple shaft revolutions. This is especially useful on servo axes where the mechanical position can change by many revolutions and where the control system benefits from absolute position information.

Typical applications include:

• Long-travel linear axes.
• Ball-screw positioning systems.
• Vertical lifting mechanisms.
• Material-handling axes.
• Large rotary indexing mechanisms.
• Machine-tool axes.
• Automated storage mechanisms.
• Long-stroke transfer systems.

For these applications, multi-turn feedback can simplify the management of machine position because the encoder provides more than just a single revolution of positional information.

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12. Single-Turn vs. Multi-Turn Configuration

The M in MPL-B680F-MJ72AA indicates the multi-turn configuration.

For a machine with a long mechanical travel, multi-turn feedback can be particularly useful because the motor shaft may rotate through many complete revolutions during normal machine operation.

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13. No Integral Holding Brake

The MPL-B680F-MJ72AA does not include an integral holding brake.

This is represented by the 2 portion of the configuration.

A no-brake motor can be advantageous for horizontal applications where the mechanical load does not need to be held in place by the motor when servo power is removed.

For a vertical axis, however, the absence of an integral brake needs careful consideration. If gravity can cause the axis to move when the motor is disabled, the machine designer may need a separate mechanical holding solution or a motor configuration equipped with an appropriate brake.

The choice should therefore be based on the actual mechanical safety requirements of the machine rather than simply selecting the motor with the highest available torque.

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14. Keyed Shaft

The MPL-B680F-MJ72AA uses a keyed shaft.

A keyed shaft is particularly useful in applications where a positive mechanical connection between the servo shaft and coupling, pulley, gearbox, or other transmission component is desired.

Typical applications include:

• Gearbox input drives.
• Belt-driven systems.
• Roller drives.
• Pulley systems.
• Mechanical couplings.
• Indexing mechanisms.
• Machine-tool axes.

The shaft key must be correctly matched with the coupling or transmission component. Proper shaft alignment is also important because excessive radial or axial loading can shorten bearing life.

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15. Connector Configuration

The model uses a SpeedTEC DIN right-angle connector configuration.

The right-angle connector arrangement can be beneficial when cabinet or machine space is limited.

Instead of having a straight connector extending directly away from the motor, the cable exits through a right-angle arrangement, which can help keep the cable routing closer to the machine structure.

This is especially useful in compact machine frames, enclosed axes, and applications where the motor is mounted close to guarding or structural members.

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16. Mounting

The motor uses an IEC metric flange mounting arrangement.

A rigid mounting structure is important because a high-performance servo motor can generate rapid torque changes. Any unwanted mechanical movement between the motor and machine structure can affect positioning accuracy, vibration, and servo tuning.

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17. Product Introduction in Practical Terms

In practical terms, the MPL-B680F-MJ72AA can be viewed as a large-frame, high-torque servo motor for demanding industrial motion axes.

It is not intended simply to run a load at a constant speed like a conventional induction motor. Its real strength appears when the machine needs controlled acceleration, controlled deceleration, precise positioning, frequent speed changes, and closed-loop feedback.

The combination of approximately 60 N·m continuous torque, approximately 108.5 N·m peak torque, 3000 rpm-class operation, multi-turn absolute feedback, and low-inertia construction gives this motor a broad range of potential applications.

The absence of an integral brake also makes the configuration particularly suitable for horizontal machine axes where a holding brake is not required.

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18. Main Product Advantages

18.1 High Continuous Torque

The approximately 60 N·m continuous torque class gives the motor enough capacity for substantial industrial loads.

This is useful for applications where the axis must maintain significant torque for extended periods rather than only requiring short acceleration bursts.

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18.2 Strong Peak Torque Capability

With approximately 108.5 N·m peak torque class capability, the motor has considerable short-duration torque reserve.

This can help during:

• Rapid acceleration.
• Rapid deceleration.
• Position correction.
• Load disturbance recovery.
• High-speed indexing.
• Direction reversal.

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18.3 3000 rpm-Class Operation

The 3000 rpm speed class provides more speed capability than the 2000 rpm versions of the same general frame and stack configuration.

This can be beneficial when the machine requires both high torque and relatively high mechanical speed.

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18.4 Multi-Turn Absolute Feedback

The multi-turn absolute encoder configuration is one of the model’s most useful features.

It is especially attractive for long-travel axes and mechanisms in which the motor may rotate through many revolutions during normal operation.

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18.5 Low-Inertia Rotor

The low-inertia design helps the servo system achieve responsive acceleration and deceleration when correctly matched to the load.

This is particularly useful for machines with frequent positioning movements.

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18.6 Keyed Shaft

The keyed shaft provides a familiar mechanical interface for industrial couplings, gearboxes, pulleys, and other transmission components.

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18.7 Large 215 mm Frame

The large frame provides the physical motor size needed to achieve substantial torque output.

For demanding axes, this can be an advantage because the motor has considerably more torque capability than smaller MPL frame sizes.

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18.8 Right-Angle Connector

The right-angle connector arrangement can make cable routing easier in compact industrial machinery.

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18.9 No-Brake Configuration

Although the lack of a brake is a limitation for some applications, it is an advantage when a brake is not required.

The configuration avoids unnecessary brake hardware and is well suited to horizontal axes where the mechanical system does not need motor-mounted holding capability.

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19. Typical Applications

Packaging Machinery

The motor can be considered for heavy-duty packaging axes where substantial torque is needed for indexing, feeding, conveying, or positioning.

Examples include:

• Packaging conveyors.
• Film transport systems.
• Product positioning mechanisms.
• Rotary indexing units.
• Large feeding mechanisms.

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Automated Assembly

Automated assembly equipment can require high acceleration, repeatable positioning, and accurate feedback.

The MPL-B680F-MJ72AA can be considered for larger assembly axes where a smaller servo motor would not provide enough continuous torque.

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Material Handling

Material-handling machinery is another suitable application category.

Potential uses include:

• Transfer axes.
• Heavy conveyors.
• Large positioning mechanisms.
• Automated storage systems.
• Lift-related horizontal mechanisms.

For vertical applications, the absence of an integral brake must be evaluated carefully.

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Machine Tools

The motor can be considered for certain machine-tool axes where the required torque, speed, and feedback characteristics match the application.

The keyed shaft and high-resolution feedback are useful characteristics for mechanical transmission systems.

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Printing and Converting

Printing, coating, slitting, and converting machinery often requires accurate speed and position control.

The 3000 rpm speed class gives the motor useful operating flexibility for rotating mechanisms and feed axes.

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Rotary Indexing

Rotary indexing equipment can benefit from high peak torque because the motor may need to accelerate a large mechanism quickly and then stop it accurately.

The peak torque capability is particularly relevant to such duty cycles.

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Long-Travel Servo Axes

The multi-turn absolute feedback makes the motor an interesting choice for long-travel axes.

Potential mechanisms include:

• Ball-screw axes.
• Large linear stages.
• Transfer mechanisms.
• Automated positioning systems.
• Long-travel material-handling axes.

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20. Applications Where This Model Is Particularly Attractive

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21. Five Closely Related Models

The following models are useful comparison choices because they are from the same MPL family and share many of the same mechanical or electrical characteristics.

Among these, MPL-B680D-MJ72AA is the closest conceptual comparison because it retains the multi-turn feedback and no-brake configuration while moving to the lower 2000 rpm speed class.

The MPL-B680D-MJ74AA is useful when the application needs both multi-turn feedback and an integral 24 V DC holding brake.

The MPL-B680F-SJ74AA is useful for comparing the same basic 3000 rpm motor class with a single-turn encoder and brake.

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22. Five Same-Brand Commonly Compared Models

The following models are useful same-brand comparison choices when evaluating servo motor size, torque, feedback, speed, and brake requirements.

These models provide a useful progression through different motor stack lengths.

The MPL-B640F is the shorter-stack option and is appropriate when approximately 36.7 N·m of continuous torque is sufficient.

The MPL-B660F sits between the B640F and B680F in physical motor length and torque capability.

The MPL-B680 family provides the largest motor stack in this comparison and therefore offers the highest torque capability among these particular configurations.

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23. B640F vs. B660F vs. B680F

One of the easiest ways to understand the MPL family is to compare the motor stack length.

The longer stack generally means a larger electromagnetic package and greater torque capability.

Therefore, if the B640F is close to the required torque limit, moving to the B660F can provide additional margin. If the application requires still more torque, the B680F is the larger option.

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24. MPL-B680F-MJ72AA vs. MPL-B680D-MJ72AA

These two models are particularly useful to compare because the general configuration is similar while the speed class differs.

The B680F is the more speed-oriented choice, while the B680D emphasizes torque and power at a lower speed class.

If the machine needs more rapid rotational movement, the B680F can be attractive. If the application is heavily torque-oriented, the B680D can offer a stronger torque profile.

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25. MPL-B680F-MJ72AA vs. MPL-B680F-SJ74AA

These two motors are also closely related.

The key decision is therefore not primarily torque or motor size.

It is feedback type versus brake requirement.

Choose the multi-turn configuration when multi-revolution absolute position information is important.

Choose the brake configuration when the machine requires an integral motor holding brake.

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26. Why the MPL-B680F-MJ72AA Can Be a Good Choice

The motor is particularly attractive when the application has the following characteristics:

• High mechanical load.
• Frequent acceleration and deceleration.
• Need for approximately 3000 rpm operation.
• Need for substantial continuous torque.
• Need for high short-duration torque.
• Long mechanical travel.
• Multi-revolution motor movement.
• Requirement for absolute feedback.
• Horizontal axis where no motor brake is required.
• Industrial machine environment.

A machine matching these characteristics can take advantage of most of the strengths built into the MPL-B680F-MJ72AA configuration.

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27. Situations Where Another Model May Be Better

Despite its strong specifications, the MPL-B680F-MJ72AA is not automatically the best choice for every machine.

A smaller MPL-B640F may be more appropriate when approximately 36.7 N·m continuous torque is enough. Using a B680F in such an application could result in an unnecessarily large and heavy motor.

A B660F can be a useful middle ground when the B640F does not provide sufficient torque but the B680F is more motor than necessary.

A B680D may be more appropriate when the machine prioritizes torque over rotational speed.

A brake-equipped MPL configuration should be considered when the machine needs the motor itself to provide holding capability after servo power is removed.

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28. Installation Considerations

Because the MPL-B680F-MJ72AA weighs approximately 40.4 kg, installation should be treated as a mechanical engineering task rather than simply an electrical installation.

The mounting surface should be rigid enough to withstand repeated servo torque changes.

The shaft coupling should be correctly aligned. Excessive angular or parallel misalignment can introduce unwanted bearing loads and vibration.

Cable routing should also be planned before installation. The right-angle connector is helpful, but adequate clearance must still be provided for the connector and cable bend radius.

The motor should not be installed in a location where excessive heat from nearby equipment causes the motor to operate outside its intended thermal conditions.

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29. Servo Drive Matching

The motor should be paired with a compatible servo drive capable of supporting its voltage class, continuous current requirements, peak current requirements, feedback interface, and motor configuration.

Motor selection should therefore not be based only on horsepower or torque.

A proper motor/drive combination should consider:

The drive must have enough continuous and peak current capacity to operate the motor correctly under the actual load profile.

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30. Load Inertia and Servo Tuning

The motor’s low rotor inertia should not be considered separately from the machine load.

For a high-performance servo axis, the relationship between motor inertia and reflected load inertia has a major influence on tuning.

A system with a very large load relative to motor inertia can still be difficult to tune, even when the motor itself has excellent dynamic characteristics.

Mechanical transmission ratios can significantly change the inertia reflected back to the motor.

Therefore, when selecting the MPL-B680F-MJ72AA, engineers should evaluate:

• Motor rotor inertia.
• Load inertia.
• Gear ratio.
• Screw lead.
• Pulley ratio.
• Coupling stiffness.
• Mechanical backlash.
• Friction.
• Required acceleration.
• Required deceleration.
• Positioning accuracy.
• Settling time.

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31. Maintenance Considerations

Servo motors generally require less routine mechanical maintenance than many traditional motor systems, but the machine environment still matters.

Important inspection points include:

• Motor mounting bolts.
• Shaft coupling condition.
• Cable and connector condition.
• Excessive vibration.
• Abnormal bearing noise.
• Motor temperature.
• Encoder feedback stability.
• Mechanical alignment.
• Contamination around the shaft area.
• Unexpected servo following error.

Because the MPL-B680F-MJ72AA does not include an integral holding brake, there is no motor-mounted brake mechanism to maintain or replace in this particular configuration.

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32. Selection Guide

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33. Final Technical Summary

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34. Overall Evaluation

The Allen-Bradley MPL-B680F-MJ72AA is a substantial industrial servo motor intended for applications where a smaller servo motor may not provide enough torque or mechanical power.

Its combination of a 215 mm frame, approximately 203.2 mm stack, 3000 rpm-class operation, approximately 60 N·m continuous torque, approximately 108.5 N·m peak torque, low rotor inertia, multi-turn absolute feedback, and keyed shaft gives it a strong position within the larger MPL servo motor range.

Its multi-turn feedback is particularly useful for long-travel and multi-revolution axes, while the 3000 rpm speed class makes it more speed-oriented than the comparable 2000 rpm B680D models.

The most important limitation is that this particular MJ72AA configuration does not include an integral holding brake. That is not necessarily a disadvantage; for many horizontal servo axes it is exactly the configuration required. However, for vertical or gravity-loaded mechanisms, the machine designer should carefully evaluate whether a brake or another independent mechanical holding mechanism is required.

Overall, the MPL-B680F-MJ72AA is best viewed as a large-frame, high-torque, 3000 rpm-class, multi-turn absolute servo motor for demanding industrial motion applications, particularly where strong dynamic performance and multi-revolution position feedback are more important than having a motor-mounted holding brake.