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Allen-Bradley MPL-B680D-SJ72AA Servo Motor – Detailed Product Specifications, Introduction, Applications, Advantages, and Model Comparison

1. Product Overview

The Allen-Bradley MPL-B680D-SJ72AA is a large-frame MP-Series MPL low-inertia brushless AC servo motor designed for industrial motion-control systems that require high torque, accurate feedback, controlled acceleration, and reliable positioning.

This model belongs to the larger end of the MPL servo motor family. It uses a 215 mm frame size, an approximately 203.2 mm magnet stack, and a 2000 rpm speed class. With approximately 62.8 N·m of continuous stall torque and 154.2 N·m of peak torque, it is intended for considerably heavier servo applications than the smaller MPL motor configurations.

One of the most important characteristics of the MPL-B680D-SJ72AA is its single-turn high-resolution absolute encoder. The motor also uses a keyed shaft, a right-angle SpeedTEC DIN connector, and a no-brake configuration.

The model is particularly suitable for machines where the servo axis requires substantial continuous torque but does not need an integrated holding brake. Typical applications include large horizontal positioning axes, material-handling machinery, packaging equipment, rotary mechanisms, machine tools, printing and converting equipment, and other industrial automation systems.

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2. Brand and Product Series

The MPL series is designed specifically for servo applications where the motor must respond accurately to commands from a compatible servo drive.

Instead of simply running at a fixed speed, the motor operates as part of a closed-loop motion system. The encoder continuously provides feedback to the servo control system, allowing the drive to regulate motor position, velocity, and torque.

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3. Detailed Technical Parameters

The values above describe the normal B680D-SJ72AA configuration. For engineering replacement work, the complete motor nameplate and actual machine configuration should be checked, especially for current, thermal ratings, connector arrangement, and exact overall dimensions.

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4. Physical Dimensions

The MPL-B680D-SJ72AA uses a Frame 6 / 215 mm mechanical configuration with an 80-series / 203.2 mm magnet stack.

The 215 × 203.2 mm dimensions represent the principal frame and magnet-stack dimensions rather than every external dimension of the installed motor.

When designing a machine around this motor, sufficient space should be reserved for the shaft, coupling, mounting hardware, connector, feedback cable, power cable, cable bend radius, and maintenance access.

This is particularly important in compact machine cabinets or enclosed mechanical assemblies.

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5. Weight

The MPL-B680D-SJ72AA is a large servo motor and has a relatively substantial mechanical mass.

For preliminary engineering and equipment layout, a practical value is approximately 45 kg class.

Actual shipping or packaged weight can be different from the bare motor weight.

For machine installation, lifting and mounting provisions should be considered in advance because this is not a lightweight servo motor.

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6. Model Number Interpretation

The model number is:

MPL-B680D-SJ72AA

The major sections can be interpreted as follows.

The model number is useful because it identifies the major mechanical, feedback, connector, and brake characteristics of the motor.

For a replacement application, it is important to match the complete catalog number rather than selecting a motor based only on the frame size.

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7. Product Introduction

The MPL-B680D-SJ72AA is designed around a brushless permanent-magnet motor structure.

The rotor uses permanent magnets, while the stator windings generate the rotating magnetic field required to produce torque.

The brushless architecture eliminates the conventional brush and commutator arrangement found in older brushed motor technologies.

This makes the motor well suited to continuous industrial operation and repeated acceleration/deceleration cycles.

The motor is intended to operate together with a compatible servo drive and motion controller. The drive supplies controlled current to the motor while the feedback device reports the actual motor position.

This closed-loop arrangement allows the machine to maintain accurate motion even when the mechanical load changes.

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8. Single-Turn High-Resolution Encoder

One of the defining characteristics of the MPL-B680D-SJ72AA is its single-turn high-resolution absolute encoder.

The encoder provides the servo drive with detailed information about the motor shaft position.

Because the feedback is absolute within one mechanical revolution, the control system can distinguish the motor’s position within that revolution rather than relying only on incremental pulse counting.

This is useful in positioning systems where accurate shaft feedback is required for repeatable machine movement.

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9. Single-Turn Versus Multi-Turn Feedback

The single-turn configuration is an important distinction when comparing the MPL-B680D-SJ72AA with multi-turn models.

For applications where the motor mechanically rotates many revolutions and the control system needs absolute multi-revolution information, a multi-turn MPL configuration may be more appropriate.

For applications where the control architecture already manages axis referencing or where single-turn feedback is sufficient, the SJ72AA can be an effective choice.

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10. Torque Performance

Torque is one of the strongest characteristics of the B680D motor family.

The MPL-B680D-SJ72AA provides approximately:

• 62.8 N·m continuous stall torque
• 154.2 N·m peak torque

The continuous torque rating is important for applications where the motor must maintain substantial torque for extended periods.

Peak torque becomes important when the machine needs rapid acceleration, rapid deceleration, high-force indexing, or temporary high-load operation.

The peak torque rating should not be treated as a continuous operating point. The actual allowable duration depends on the drive, thermal conditions, duty cycle, motor temperature, and machine load.

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11. Rated Power

The motor is approximately a 9.3 kW continuous-output class servo motor.

This power level makes the motor suitable for relatively large automation systems.

It is more appropriate for substantial mechanical loads than small indexing or light-duty servo axes.

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12. 2000 rpm Speed Class

The D in the model designation identifies the 2000 rpm class.

The 2000 rpm configuration provides a useful balance between rotational speed and torque.

For applications that need more rotational speed, the 3000 rpm B680F configuration or the 3500 rpm B680H configuration may be worth considering.

For applications where high torque and moderate servo speed are more important, the B680D is a particularly logical choice.

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13. Low-Inertia Rotor

The motor has an approximate rotor inertia of 0.00775 kg·m².

Low rotor inertia allows the motor to change speed efficiently.

This is valuable in applications that repeatedly accelerate, decelerate, stop, reverse, or index.

The actual system inertia, however, includes much more than the motor rotor.

The inertia of gears, couplings, rollers, screws, rotary tables, pulleys, and the driven load must all be considered.

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14. Keyed Shaft

The MPL-B680D-SJ72AA uses a keyed shaft extension.

A keyed shaft is a familiar mechanical interface and is particularly useful for applications where the motor must transmit significant torque.

Correct shaft alignment is essential.

Incorrect coupling alignment can increase bearing loading, vibration, temperature, and mechanical wear.

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15. No Integral Brake

The MPL-B680D-SJ72AA is a no-brake configuration.

The absence of a brake is not necessarily a disadvantage.

For horizontal axes, conveyors, rotary systems, and many machine-tool applications, a motor-mounted holding brake may not be required.

For a vertical axis carrying a suspended load, however, the machine designer must determine how the load will be held safely when servo torque is removed.

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16. SpeedTEC DIN Connector

The motor uses a SpeedTEC DIN connector in a right-angle configuration.

The rotatable connector is useful when the motor is installed in different orientations.

It can help reduce cable-routing restrictions and make it easier to position the power and feedback cables within the machine.

Cable clearance should still be checked carefully during mechanical design.

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17. Mounting Arrangement

The MPL-B680D-SJ72AA uses an IEC metric flange mounting arrangement.

The machine mounting plate should be sufficiently rigid to support the motor and maintain shaft alignment.

A flexible mounting structure can introduce vibration and mechanical resonance, which can affect servo performance.

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18. Main Product Advantages

18.1 High Torque Capability

The approximately 62.8 N·m continuous torque makes this motor suitable for heavy-duty servo axes.

The approximately 154.2 N·m peak torque provides substantial dynamic torque during acceleration and short-duration high-load conditions.

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18.2 High Power in a Servo Package

With approximately 9.3 kW continuous output, the motor can handle considerably larger mechanical loads than smaller MPL configurations.

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18.3 High-Resolution Feedback

The 1024 Sin/Cos cycles-per-revolution feedback provides detailed shaft-position information.

This supports accurate closed-loop control.

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18.4 Low-Inertia Construction

The low-inertia rotor helps the motor respond quickly to speed and position commands.

This is especially useful for machines with frequent acceleration and deceleration.

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18.5 Keyed Mechanical Interface

The keyed shaft is practical for industrial couplings, gears, pulleys, and other mechanical transmission systems.

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18.6 Flexible Connector Arrangement

The right-angle, rotatable DIN connector makes cable routing easier in many machine configurations.

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18.7 No-Brake Configuration

For machines that do not require a holding brake, the no-brake configuration keeps the motor arrangement straightforward.

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19. Typical Industrial Applications

The MPL-B680D-SJ72AA can be considered for a wide range of industrial motion applications.

Packaging Machinery

Large packaging machines often contain servo-driven indexing, feeding, forming, cutting, or positioning mechanisms.

The B680D motor is particularly suited to the larger axes where substantial torque is required.

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Material Handling

Potential applications include:

• Heavy conveyors.
• Transfer systems.
• Roller mechanisms.
• Positioning units.
• Large handling axes.
• Automated storage equipment.

The motor’s high continuous torque is useful when the machine must repeatedly move substantial loads.

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Machine Tools

Possible applications include:

• Large auxiliary axes.
• Rotary positioning mechanisms.
• Heavy horizontal axes.
• Servo-driven mechanical assemblies.
• Large indexing systems.

The feedback system can support accurate servo positioning when correctly matched with the drive and machine mechanics.

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Printing and Converting Equipment

Printing and converting machines often require coordinated servo movement.

Typical applications can include:

• Roll drives.
• Web-handling axes.
• Positioning mechanisms.
• Cutting systems.
• Indexing mechanisms.

The 2000 rpm speed class is particularly appropriate where torque is more important than very high shaft speed.

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Rotary Tables

Large rotary tables can have significant inertia.

The B680D’s high peak torque can help accelerate and decelerate such mechanisms.

Correct inertia matching and mechanical transmission design remain important.

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Linear Servo Axes

The motor can be coupled to:

• Ball screws.
• Rack-and-pinion mechanisms.
• Timing belts.
• Gearboxes.
• Roller drives.

This makes it suitable for long-travel positioning systems and large linear machine axes.

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20. Applications Where This Motor Is Particularly Attractive

The motor should not be selected simply because it provides a large torque rating.

If the machine requires much less torque, a smaller motor can provide a more compact solution with lower mechanical mass.

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21. Five Related MPL Models

The following five models are useful when comparing the MPL-B680D-SJ72AA with other motors from the same family.

The closest comparison is the MPL-B680D-SJ74AA, because it has the same general B680D frame, stack, speed, and single-turn feedback arrangement but adds an integral 24 V DC brake.

The MPL-B680D-MJ72AA is useful when the application needs multi-turn feedback instead of single-turn feedback.

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22. Five Same-Brand Commonly Compared Models

These are useful same-brand comparison models because they cover different combinations of frame stack, speed, torque, feedback, and brake configuration.

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23. B640F, B660F, and B680D Comparison

The comparison shows the role of the longer B680D stack.

The B640F is substantially shorter and lighter.

The B660F provides an intermediate mechanical package.

The B680D provides the highest torque and power of these three configurations.

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24. B680D Single-Turn Versus Multi-Turn

The main difference is the feedback configuration rather than the basic motor power class.

When selecting between them, the motion-control architecture should be considered first.

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25. B680D No-Brake Versus Brake Configuration

The SJ72AA is preferable when no integrated holding brake is required.

The SJ74AA becomes more attractive when the machine needs motor-mounted holding capability, particularly for applications where gravity can move the axis when servo torque is removed.

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26. Product Advantages in Practical Machine Design

The MPL-B680D-SJ72AA has several characteristics that make it particularly useful in large automation equipment.

The first is its torque capacity.

A continuous torque of approximately 62.8 N·m gives the motor enough capacity for substantial mechanical loads without immediately requiring a gearbox simply to increase motor torque.

The second major advantage is its peak torque capability.

Approximately 154.2 N·m of peak torque provides significant acceleration capability, which can be useful when a heavy mechanical load must be moved quickly.

The third advantage is the low-inertia design.

Even though the motor itself is physically large, its low-inertia rotor helps maintain a responsive servo system.

The fourth advantage is the high-resolution single-turn absolute feedback.

This provides the servo drive with detailed motor position information and supports accurate closed-loop control.

The fifth advantage is the keyed shaft.

For industrial machinery, keyed shaft interfaces remain practical because they work well with a wide range of couplings and mechanical transmission components.

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27. Mechanical Design Considerations

Because the MPL-B680D-SJ72AA is a large motor, the machine structure should be designed accordingly.

The mounting plate needs sufficient rigidity.

The motor flange must be supported correctly.

The shaft and driven mechanism should be properly aligned.

The coupling should be suitable for the motor’s torque and speed.

Radial and axial shaft loading should remain within the applicable mechanical limits.

Cable routing should prevent excessive force from being transferred into the motor connector.

The motor should also have enough surrounding space for heat dissipation and maintenance.

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28. Inertia Matching

One of the most important parts of servo motor selection is matching the motor inertia to the reflected load inertia.

The motor rotor itself has approximately 0.00775 kg·m² of inertia.

However, the driven load may have significantly greater inertia.

For example, a large rotary table, roller, flywheel, gearbox, or screw-driven axis can produce substantial reflected inertia at the motor shaft.

The transmission ratio must therefore be considered when calculating the effective motor-side load inertia.

Correct inertia matching can improve:

• Acceleration.
• Deceleration.
• Settling time.
• Positioning accuracy.
• Servo stability.
• Mechanical smoothness.
• Motor thermal performance.

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29. Thermal Considerations

The continuous torque rating is based on thermal conditions and the applicable motor operating environment.

Actual machine operation should therefore be evaluated according to the complete duty cycle.

Important factors include:

• Ambient temperature.
• Motor mounting orientation.
• Machine enclosure.
• Cooling conditions.
• Continuous load.
• Acceleration frequency.
• Deceleration frequency.
• Peak torque duration.
• Motor temperature.
• Surrounding heat sources.

A machine that repeatedly operates near the continuous torque limit may require more careful thermal evaluation than a machine with short intermittent loads.

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30. No-Brake Application Considerations

The no-brake design is particularly convenient for horizontal applications.

Examples include:

• Horizontal conveyors.
• Horizontal positioning axes.
• Rotary rollers.
• Machine-tool axes.
• Packaging axes.
• Horizontal transfer units.

For vertical applications, the machine designer should consider whether an external mechanical holding device, counterbalance, or other load-retention mechanism is necessary.

The motor should not be expected to provide mechanical load holding when the servo system is de-energized.

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31. Maintenance Considerations

Because this is a brushless servo motor, there are no conventional motor brushes to replace as part of normal operation.

Routine inspection should instead focus on the overall servo system.

Recommended inspection areas include:

• Motor mounting bolts.
• Shaft coupling.
• Mechanical alignment.
• Bearing condition.
• Abnormal vibration.
• Motor temperature.
• Encoder feedback.
• Power cable condition.
• Feedback cable condition.
• Connector condition.
• Servo following error.
• Mechanical backlash.
• Unusual acoustic noise.

Changes in vibration, temperature, positioning accuracy, or following error can indicate a developing problem in the motor or in the connected mechanical system.

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32. Servo Drive Compatibility

The MPL-B680D-SJ72AA should be paired with a compatible servo drive that supports the motor’s electrical characteristics and single-turn high-resolution feedback arrangement.

Commonly associated compatible drive families include Kinetix and other compatible servo drive platforms used with MPL motors.

The exact drive selection should be based on:

A motor with the same frame and torque rating is not automatically electrically interchangeable.

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33. Recommended Model Selection Guide

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34. Overall Technical Summary

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35. Final Assessment

The Allen-Bradley MPL-B680D-SJ72AA is a powerful large-frame servo motor intended for applications where torque, positioning accuracy, and dynamic response are more important than having a compact motor package.

Its combination of approximately 62.8 N·m continuous torque, 154.2 N·m peak torque, 9.3 kW rated output, 2000 rpm speed, 215 mm frame size, 203.2 mm magnet stack, and high-resolution single-turn absolute feedback makes it a strong choice for heavy industrial motion systems.

The low-inertia rotor helps the motor respond effectively to acceleration and deceleration commands, while the keyed shaft provides a familiar mechanical connection for industrial transmissions.

The no-brake configuration is especially suitable for horizontal axes where a holding brake is not required.

For machines requiring a brake, the MPL-B680D-SJ74AA is a natural comparison.

For applications requiring multi-turn absolute feedback, the MPL-B680D-MJ72AA or MPL-B680D-MJ74AA should be considered.

For applications requiring higher speed, the B680F and B680H configurations provide alternative directions.

Overall, the MPL-B680D-SJ72AA is best viewed as a high-torque, 2000 rpm, low-inertia, single-turn absolute servo motor for demanding industrial automation equipment, particularly where the machine needs substantial continuous torque without an integrated motor brake.