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Allen-Bradley MPL-B4540F-RK72AA Low-Inertia Servo Motor

1. Product Overview

The Allen-Bradley MPL-B4540F-RK72AA is a low-inertia brushless AC rotary servo motor belonging to the MP-Series MPL Low-Inertia Servo Motor Series.

It is designed for industrial motion-control systems that require accurate positioning, controlled acceleration and deceleration, repeatable speed regulation, and reliable closed-loop operation.

The MPL-B4540F-RK72AA uses a 130 mm frame with a 101.6 mm magnet stack, giving it a useful balance between motor size and torque output.

It operates in the 460 V AC / 480 V AC class and has a 3000 rpm speed rating. The motor provides approximately 10.2 N·m continuous torque and approximately 27.1 N·m peak torque, placing it in the approximately 2.6 kW performance class.

A key feature of the RK72AA configuration is its keyless shaft extension. Instead of using a conventional shaft key, this configuration is intended for mechanical arrangements where a keyless coupling or clamping connection is preferred.

The motor uses resolver feedback, providing the closed-loop position and speed information required by the servo drive.

Another important feature is the right-angle SpeedTEC DIN connector, which can be rotated through approximately 180°. This gives the machine builder greater flexibility when routing motor cables in compact equipment.

Unlike the RJ74AA configuration, the RK72AA does not include an integrated holding brake. This makes it particularly appropriate for horizontal axes or other applications where a motor holding brake is not required.

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2. Brand and Series Information

Item	Specification
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Servo Motor Series
Model	MPL-B4540F-RK72AA
Product Type	Brushless AC Rotary Servo Motor
Motor Construction	Low-Inertia Servo Motor
Voltage Class	460 V AC / 480 V AC
Feedback	2-Pole Resolver
Shaft Configuration	Keyless Shaft Extension
Brake	No Brake
Connector	SpeedTEC DIN
Connector Configuration	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric
Frame Size	130 mm
Magnet Stack	101.6 mm
Rated Speed	3000 rpm

The product belongs to the MPL family of low-inertia brushless servo motors.

The B4540F configuration represents a particular motor size within the MPL family, while the RK72AA suffix identifies the feedback, shaft, connector, and brake configuration.

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3. Detailed Technical Parameters

Parameter	Specification
Model	MPL-B4540F-RK72AA
Brand	Allen-Bradley
Series	MPL Low-Inertia Servo Motor
Product Family	MP-Series
Motor Type	Brushless AC Servo Motor
Motor Design	Low Inertia
Voltage Class	460 V AC
Application Class	480 V AC
Speed	3000 rpm
Continuous Stall Torque	Approx. 10.2 N·m
Peak Torque	Approx. 27.1 N·m
Rated Power Class	Approx. 2.6 kW
Feedback Device	2-Pole Resolver
Shaft	Keyless Shaft Extension
Shaft Key	None
Brake	None
Connector	SpeedTEC DIN
Connector Style	Right Angle
Connector Rotation	180° Rotatable
Mounting Standard	IEC Metric
Mounting Holes	Free Mounting Holes, Type FF
Frame Size	130 mm
Magnet Stack Length	101.6 mm
Frame Size	Approx. 5.12 in.
Stack Length	Approx. 4.00 in.
Overall Length	Approx. 330 mm class
Weight	Approx. 6.8–11 kg depending on catalog/revision
Enclosure	Industrial Servo Motor Construction
Feedback Type	Resolver
Brake Configuration	No Brake
Shaft Configuration	Keyless

The most consistently listed mechanical weight for this configuration is approximately 6.8 kg, although other catalog records and legacy configurations may list different shipping or motor weights. For equipment replacement, the actual nameplate and mechanical drawing should be used as the final dimensional reference.

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4. Mechanical Dimensions

Mechanical compatibility is one of the most important considerations when replacing an existing servo motor.

The MPL-B4540F-RK72AA uses a 130 mm frame size and a 101.6 mm magnet stack, which defines the basic B4540F mechanical configuration.

Mechanical Parameter	Specification
Model	MPL-B4540F-RK72AA
Frame Size	130 mm
Frame Diameter Class	Approx. 130 mm
Magnet Stack	101.6 mm
Stack Length	4.00 in.
Frame Size	5.12 in.
Overall Motor Length	Approx. 330 mm class
Mounting	IEC Metric
Mounting Hole Type	Free Mounting Holes, Type FF
Shaft	Keyless
Shaft Key	None
Connector	SpeedTEC DIN
Connector Direction	Right Angle
Connector Adjustment	180° Rotatable
Brake	None
Approximate Weight	6.8 kg class

The keyless shaft is an important mechanical distinction.

A keyless servo shaft can be advantageous when the machine transmission uses a clamping hub, shrink-fit coupling, friction-lock coupling, or another mechanical connection that does not require a traditional shaft key.

This configuration can provide a clean mechanical interface and can reduce the need to accommodate a keyway in the driven component.

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5. Model Number Explanation

The model number contains useful information about the motor configuration.

Model Code	Description
MPL	MPL Low-Inertia Servo Motor Series
B	460 V class motor configuration
45	130 mm frame size
40	101.6 mm magnet stack
F	3000 rpm speed class
R	Resolver feedback
K	Keyless shaft extension
7	Right-angle, rotatable SpeedTEC DIN connector
2	No brake
AA	Configuration / revision designation

The most important part of the RK72AA designation is the combination of resolver feedback + keyless shaft + right-angle connector + no brake.

This makes it mechanically and electrically different from closely related versions such as the RJ72AA and RK74AA.

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6. Product Introduction

The MPL-B4540F-RK72AA is intended for industrial motion systems in which the motor is controlled through a servo drive and motion controller.

The motor operates as part of a closed-loop control system.

The servo drive controls the electrical power supplied to the motor while the resolver supplies rotor-position information back to the control system. This allows the system to regulate motor speed, position, and torque much more precisely than a conventional fixed-speed motor.

The low-inertia construction is especially useful for machinery with frequent acceleration and deceleration.

A machine may require the motor to start, accelerate, reach a target speed, slow down, stop at a specific position, and then immediately reverse direction. In such applications, excessive motor inertia can reduce dynamic response.

The MPL design addresses this type of operating requirement by using a relatively low-inertia motor construction.

The 10.2 N·m continuous torque rating makes the B4540F configuration suitable for a broad range of medium-duty servo axes.

At the same time, the approximately 27.1 N·m peak torque capability provides additional torque capacity for short-duration acceleration and dynamic load changes.

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7. Main Performance Characteristics

7.1 Low-Inertia Servo Construction

Low inertia is one of the most important characteristics of this motor.

A servo motor with relatively low rotor inertia can change speed rapidly when commanded by the servo drive.

This is beneficial in machines with short cycle times, frequent indexing, rapid positioning, and repeated forward/reverse motion.

Typical applications include packaging machinery, automated assembly systems, indexing equipment, material handling systems, and machine tools.

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7.2 10.2 N·m Continuous Torque

The MPL-B4540F-RK72AA provides approximately 10.2 N·m continuous torque.

This makes it suitable for applications where a moderate amount of continuous mechanical torque is required.

The continuous torque rating should be evaluated against the actual machine load, duty cycle, acceleration profile, transmission ratio, and environmental operating conditions.

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7.3 27.1 N·m Peak Torque

The approximate 27.1 N·m peak torque rating provides additional short-term torque capacity.

This is particularly useful during acceleration.

For example, if a machine needs to accelerate a mechanical load quickly, the motor may require significantly more torque for a short period than it requires during steady-state operation.

The peak torque capability provides additional dynamic margin for these conditions.

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7.4 3000 rpm Operation

The motor is designed for the 3000 rpm speed class.

This provides a useful balance between rotational speed and torque.

It can be applied to direct mechanical drives as well as geared, belt-driven, screw-driven, and other transmission systems.

The final motor speed should always be selected according to the actual load requirements and servo-drive configuration.

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8. Resolver Feedback

The MPL-B4540F-RK72AA uses a 2-pole resolver for feedback.

The resolver supplies rotor-position information to the servo system.

This allows the control system to determine the motor’s rotational position and regulate the motor accordingly.

Resolver feedback is widely associated with industrial servo systems where rugged feedback performance is important.

For machinery operating in industrial environments, resolver-based feedback can provide a robust solution for closed-loop control.

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9. Keyless Shaft Design

The K in the RK72AA configuration indicates a keyless shaft.

This is one of the major differences between the RK72AA and RJ72AA versions.

Feature	RK72AA	RJ72AA
Feedback	Resolver	Resolver
Frame	130 mm	130 mm
Stack	101.6 mm	101.6 mm
Speed	3000 rpm	3000 rpm
Continuous Torque	Approx. 10.2 N·m	Approx. 10.2 N·m
Shaft	Keyless	Keyed
Brake	No	No
Connector	Right-angle SpeedTEC DIN	Right-angle SpeedTEC DIN

A keyless shaft is often preferred where the mechanical system uses a clamping connection.

It can be useful in applications involving precision couplings, clamping hubs, gearboxes, and other mechanical transmission components designed specifically for keyless motor shafts.

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10. No-Brake Configuration

The RK72AA does not include an integrated holding brake.

This is not necessarily a disadvantage.

For many horizontal servo axes, a holding brake is unnecessary.

Removing the brake can also reduce motor complexity and weight.

Typical applications where a no-brake configuration can be appropriate include:

• Horizontal conveyor axes
• Rotary indexing systems
• Horizontal positioning stages
• Belt-driven axes
• Packaging mechanisms
• Material-feed systems
• Rotary machinery
• Machine-tool horizontal axes

For vertical loads, however, a brake may be required depending on the machine design and safety requirements.

In those cases, a related brake-equipped model such as the MPL-B4540F-RK74AA may be a more appropriate selection.

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11. Connector Design

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

The connector can be rotated through approximately 180°.

This is useful when installation space around the motor is restricted.

In automated machinery, cable routing can become a significant mechanical design issue. A fixed connector orientation may interfere with machine guards, adjacent components, cable tracks, or structural members.

The rotatable right-angle connector provides additional flexibility during machine installation.

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12. Main Product Advantages

12.1 Compact 130 mm Frame

The 130 mm frame provides a relatively compact mechanical package for a motor capable of approximately 10.2 N·m continuous torque.

This can help machine builders maintain a compact overall machine footprint.

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12.2 Low-Inertia Construction

The low-inertia rotor design supports fast response.

This is especially useful for machines that require frequent speed changes and short motion cycles.

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12.3 High Peak Torque

The approximately 27.1 N·m peak torque rating provides substantial short-term torque capability.

This gives the machine additional acceleration capacity without requiring the motor to operate continuously at its peak torque level.

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12.4 Keyless Shaft

The keyless shaft makes the motor suitable for mechanical systems designed around clamp-type or friction-lock couplings.

This can be particularly attractive in precision mechanical assemblies.

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12.5 Resolver Feedback

The resolver provides closed-loop motor feedback for servo control.

Its industrial-oriented construction is suitable for many demanding automation systems.

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12.6 No-Brake Configuration

The absence of a brake is advantageous for applications where a holding brake is unnecessary.

This makes the motor a good fit for many horizontal motion axes.

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12.7 Flexible Cable Routing

The 180° rotatable right-angle connector provides useful installation flexibility.

This can simplify motor cable routing in compact machines.

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12.8 IEC Metric Mounting

The IEC metric mounting arrangement is convenient for equipment designed around metric mechanical dimensions.

The free-mounting-hole arrangement also gives machine designers greater flexibility when preparing the mounting structure.

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13. Typical Applications

13.1 Packaging Equipment

Packaging machinery is one of the most suitable application areas for this type of servo motor.

Packaging machines frequently require rapid indexing, controlled acceleration, precise stopping, and synchronized movement.

The MPL-B4540F-RK72AA can be used for:

• Product positioning
• Film feeding
• Indexing mechanisms
• Rotary cutters
• Labeling mechanisms
• Carton handling
• Product feeders
• Conveyor positioning

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13.2 Material Handling

The motor can be used in automated material-handling equipment where accurate movement is required.

Examples include:

• Conveyor positioning
• Transfer mechanisms
• Sorting equipment
• Feed systems
• Automated storage machinery
• Indexing mechanisms

The no-brake configuration is particularly suitable for horizontal material-handling axes.

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13.3 Automated Assembly

Automated assembly machines often require precise positioning and rapid repetitive motion.

The motor can be applied to:

• Linear positioning mechanisms
• Rotary indexing tables
• Assembly fixtures
• Pick-and-place systems
• Component feeders
• Automated workstations

The low-inertia characteristics are useful where cycle time is important.

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13.4 Machine Tools

The MPL-B4540F-RK72AA can be considered for various servo-controlled machine-tool axes.

Possible applications include:

• Feed axes
• Positioning systems
• Rotary auxiliary axes
• Automated tool-handling mechanisms
• Material-feed systems

For vertical machine axes, the absence of a brake should be carefully evaluated.

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13.5 Printing and Converting Machinery

Printing and converting equipment often requires synchronized speed and position control.

Servo motors can be used for:

• Web handling
• Roller control
• Cutting
• Indexing
• Feeding
• Registration

The low-inertia design is beneficial where rapid speed changes are required.

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13.6 Automated Conveyor Systems

Conveyor systems increasingly use servo motors when products must be positioned precisely rather than simply transported at a constant speed.

The MPL-B4540F-RK72AA can be used for indexing conveyors, positioning conveyors, product-transfer systems, and automated production lines.

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14. Application Advantages

Application	Main Benefit
Packaging	Fast indexing and repeatable positioning
Material Handling	Accurate motion control
Assembly	Precise positioning and repeatability
CNC Machinery	Closed-loop feed control
Printing	Speed synchronization
Converting	Rapid acceleration and deceleration
Conveyor Positioning	Controlled start/stop motion
Rotary Indexing	Repeatable angular positioning
Automated Production Lines	Coordinated servo movement

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15. Five Recommended Related Models

The following five models are closely related to the MPL-B4540F-RK72AA and can be considered when the machine requirements change.

Model	Speed	Continuous Torque	Peak Torque	Power Class	Feedback	Shaft	Brake	Dimensions	Weight
MPL-B4540F-RJ72AA	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Resolver	Keyed	No	130 × 101.6 mm	Approx. 11 kg
MPL-B4540F-RK74AA	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Resolver	Keyless	24 V DC	130 × 101.6 mm	Approx. 13 kg class
MPL-B4540F-RJ74AA	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Resolver	Keyed	24 V DC	130 × 101.6 mm	Approx. 13 kg
MPL-B4530F-RJ72AA	3000 rpm	Approx. 8.25 N·m	Approx. 20.3 N·m	Approx. 2.1 kW	Resolver	Keyed	No	130 × 76.2 mm	Approx. 8 kg
MPL-B4560F-RJ72AA	3000 rpm	Approx. 14.1 N·m	Approx. 34.4 N·m	Approx. 3.2 kW	Resolver	Keyed	No	130 × 152.4 mm	Approx. 12 kg

MPL-B4540F-RJ72AA

This is one of the closest alternatives.

It has the same 130 mm frame, 101.6 mm stack, resolver feedback, 3000 rpm speed class, and approximately 10.2 N·m continuous torque.

The major difference is the keyed shaft.

This model is preferable when the machine transmission requires a conventional keyed shaft.

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MPL-B4540F-RK74AA

The RK74AA retains the keyless shaft configuration but adds a 24 V DC holding brake.

It is a natural choice when the mechanical system requires a keyless shaft but the application also requires shaft holding.

This is particularly relevant to vertical or mechanically sensitive axes.

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MPL-B4540F-RJ74AA

The RJ74AA combines the same basic B4540F performance with a keyed shaft and 24 V DC brake.

It is a strong alternative when both a conventional keyed shaft and motor holding brake are required.

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MPL-B4530F-RJ72AA

The B4530F has a shorter 76.2 mm stack.

It produces lower torque than the B4540F but can be useful when the machine requires a shorter motor and the load does not require the additional torque capacity of the B4540F.

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MPL-B4560F-RJ72AA

The B4560F uses a longer 152.4 mm stack and provides higher torque.

It is a suitable direction when the 10.2 N·m continuous torque of the B4540F is not sufficient.

The tradeoff is a larger motor stack and greater motor mass.

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16. Five Popular Models from the Same Brand

Model	Feedback	Speed	Continuous Torque	Peak Torque	Power Class	Shaft	Brake	Dimensions	Weight
MPL-B4540F-MJ74AA	Multi-turn absolute	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Keyed	24 V DC	130 × 101.6 mm	Approx. 10–11 kg
MPL-B4540F-MK74AA	Multi-turn absolute	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Keyless	24 V DC	130 × 101.6 mm	Approx. 10–12 kg
MPL-B4540F-HJ74AA	High-resolution incremental	3000 rpm	10.2 N·m	27.1 N·m	Approx. 2.6 kW	Keyed	24 V DC	130 × 101.6 mm	Approx. 11 kg class
MPL-B4560F-MJ74AA	Multi-turn absolute	3000 rpm	Approx. 14.1 N·m	Approx. 34.4 N·m	Approx. 3.2 kW	Keyed	24 V DC	130 × 152.4 mm	Approx. 11.8–16 kg class
MPL-B540K-MJ74AA	Multi-turn absolute	4000 rpm	Approx. 19.4 N·m	Approx. 48.6 N·m	Approx. 5.4 kW	Keyed	24 V DC	Approx. 165 × 101.6 mm	Approx. 15 kg

These models provide several different approaches to servo motor selection.

The MPL-B4540F-MJ74AA is close to the target motor in physical size and torque but uses multi-turn absolute feedback.

The MPL-B4540F-MK74AA combines a similar motor performance level with a keyless shaft and brake.

The MPL-B4540F-HJ74AA is designed around high-resolution incremental feedback and is therefore useful where the control architecture requires that type of feedback.

The MPL-B4560F-MJ74AA provides a higher torque level while retaining the same general 130 mm frame family.

The MPL-B540K-MJ74AA moves to a larger motor class with higher torque and a higher 4000 rpm speed rating.

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17. Target Model vs. Closest Alternatives

Feature	MPL-B4540F-RK72AA	MPL-B4540F-RJ72AA	MPL-B4540F-RK74AA	MPL-B4540F-RJ74AA
Frame	130 mm	130 mm	130 mm	130 mm
Stack	101.6 mm	101.6 mm	101.6 mm	101.6 mm
Speed	3000 rpm	3000 rpm	3000 rpm	3000 rpm
Continuous Torque	10.2 N·m	10.2 N·m	10.2 N·m	10.2 N·m
Peak Torque	27.1 N·m	27.1 N·m	27.1 N·m	27.1 N·m
Feedback	Resolver	Resolver	Resolver	Resolver
Shaft	Keyless	Keyed	Keyless	Keyed
Brake	No	No	Yes	Yes
Connector	Right-angle DIN	Right-angle DIN	Right-angle DIN	Right-angle DIN
Approx. Weight	6.8 kg class	11 kg class	13 kg class	13 kg class

This comparison makes the role of the RK72AA configuration clear.

The RK72AA is essentially the keyless, no-brake configuration within the B4540F resolver motor family.

If a keyed shaft is required, the RJ72AA is the logical alternative.

If a brake is required while retaining the keyless shaft, the RK74AA is the more appropriate option.

If both a keyed shaft and brake are required, the RJ74AA becomes the closest alternative.

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18. Advantages of Choosing the RK72AA Configuration

The MPL-B4540F-RK72AA is particularly attractive when the machine design has the following requirements:

Keyless mechanical transmission: The shaft is designed without a traditional keyway, making it suitable for clamp-type coupling systems.

No brake requirement: For horizontal axes or systems where the servo controller itself provides the required stopping function, a motor brake may not be necessary.

Low-inertia operation: The motor is intended for fast acceleration, deceleration, and positioning.

Resolver feedback: The motor provides closed-loop feedback for industrial servo control.

3000 rpm operation: The speed class is suitable for a broad range of industrial automation applications.

10.2 N·m continuous torque: The motor provides a useful continuous torque level for medium-sized servo axes.

27.1 N·m peak torque: The motor has significant short-duration torque capability for dynamic operation.

130 mm frame: The motor maintains a relatively compact frame while providing substantial torque.

Flexible connector arrangement: The 180° rotatable right-angle connector helps simplify machine installation.

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19. Practical Selection Guide

Machine Requirement	Recommended Direction
Keyless shaft required, no brake	MPL-B4540F-RK72AA
Keyed shaft required, no brake	MPL-B4540F-RJ72AA
Keyless shaft + brake required	MPL-B4540F-RK74AA
Keyed shaft + brake required	MPL-B4540F-RJ74AA
Lower torque / shorter motor required	MPL-B4530F family
Higher torque required	MPL-B4560F family
Multi-turn absolute feedback required	MPL-B4540F-M series
High-resolution incremental feedback required	MPL-B4540F-H series

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20. Recommended Use Cases

For a horizontal servo axis, the MPL-B4540F-RK72AA can be an especially practical configuration because the machine may not require a motor holding brake.

For a rotary indexing mechanism, the combination of 3000 rpm operation, resolver feedback, low inertia, and approximately 10.2 N·m continuous torque provides a useful servo platform.

For a belt-driven positioning system, the keyless shaft can be advantageous when the transmission uses a clamping coupling.

For packaging equipment, the low-inertia characteristics can support rapid repetitive movement.

For automated assembly, resolver feedback can provide the closed-loop control required for repeatable positioning.

For material-handling machinery, the motor can be used for horizontal positioning, indexing, feeding, and transfer functions.

For vertical axes, however, the no-brake configuration must be carefully evaluated. A related brake-equipped configuration may be more appropriate when the load must be held mechanically after power is removed.

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21. Overall Product Evaluation

The Allen-Bradley MPL-B4540F-RK72AA is a well-balanced low-inertia industrial servo motor for applications requiring approximately 10.2 N·m continuous torque and 3000 rpm operation.

Its most distinctive characteristic is the combination of a keyless shaft, resolver feedback, no brake, 130 mm frame, 101.6 mm stack, and right-angle rotatable SpeedTEC DIN connector.

Compared with the keyed RJ72AA configuration, the RK72AA is better suited to machinery using a keyless mechanical coupling.

Compared with the brake-equipped RK74AA, the RK72AA is more suitable for applications where no integrated motor holding brake is required.

The motor’s approximately 27.1 N·m peak torque provides additional dynamic capacity during acceleration and short-duration load changes.

The low-inertia construction makes the motor particularly useful for applications where the servo axis must repeatedly accelerate, decelerate, stop, and change direction.

The 130 mm frame and 101.6 mm stack provide a useful compromise between physical size and motor performance.

Overall, the MPL-B4540F-RK72AA is a practical choice for industrial automation systems requiring a 3000 rpm low-inertia servo motor, resolver feedback, keyless shaft connection, and no integrated brake.

For replacement projects, the most important items to verify before installation are the exact mounting dimensions, shaft dimensions, coupling requirements, resolver compatibility, servo-drive compatibility, cable configuration, load inertia, continuous torque requirement, peak torque requirement, acceleration/deceleration profile, and whether the machine requires a mechanical holding brake.