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Allen-Bradley MPL-B4540F-SK72AA Low-Inertia Servo Motor – Technical Specifications, Applications and Model Selection Guide

1. Product Overview

The Allen-Bradley MPL-B4540F-SK72AA is a low-inertia AC rotary servo motor designed for precision industrial motion-control applications.

It belongs to the MP-Series MPL low-inertia servo motor family and uses a 130 mm metric frame with a 101.6 mm magnet stack. The motor is designed for 3000 rpm operation and incorporates a single-turn high-resolution encoder for closed-loop position and speed control.

A major characteristic of this model is its keyless shaft configuration. Instead of using a conventional shaft key, the motor is intended for mechanical connections based on suitable keyless clamping or coupling arrangements.

The motor also uses a right-angle SpeedTEC DIN connector that can be rotated through approximately 180°. This provides useful flexibility when the motor is installed in compact machinery where cable routing space is limited.

The SK72AA configuration does not include an integral holding brake. This makes it particularly suitable for horizontal axes, indexing systems, conveyors, packaging machinery and other applications where the motor does not need to mechanically hold a load after servo power is removed.

The motor operates in the 460 V AC / 480 V AC class and is intended to be used with a compatible servo drive and motion-control system.

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2. Brand and Series Information

Item	Specification
Brand	Allen-Bradley
Product Family	MP-Series
Motor Series	MPL Low-Inertia Servo Motors
Product Type	AC Rotary Servo Motor
Model	MPL-B4540F-SK72AA
Voltage Class	460 V AC / 480 V AC class
Rated Speed	3000 rpm
Feedback	Single-turn high-resolution encoder
Shaft Type	Keyless shaft extension
Brake	No integral brake
Connector	SpeedTEC DIN, right-angle
Connector Rotation	Approximately 180°
Mounting	IEC metric flange
Frame Size	130 mm
Magnet Stack Length	101.6 mm
Motor Design	Low-inertia brushless servo motor
Typical Duty	Industrial servo motion control

The model is part of the MPL low-inertia servo motor family, which is designed around compact permanent-magnet servo motor construction and dynamic motion performance.

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3. Detailed Technical Parameters

Electrical and Performance Specifications

Parameter	Specification
Model	MPL-B4540F-SK72AA
Motor Type	Brushless AC permanent-magnet servo motor
Voltage Class	460 V AC / 480 V AC class
Rated Speed	3000 rpm
Maximum Speed	3000 rpm class
Continuous Stall Torque	Approx. 10.2 N·m
Peak Torque	Approx. 27.1 N·m
Rated Continuous Output	Approx. 2.6 kW
Feedback Type	Single-turn high-resolution encoder
Feedback Resolution	1024 Sin/Cos class
Feedback System	Absolute single-turn
Feedback Protocol	Hiperface-type
Shaft Configuration	Keyless shaft extension
Shaft Key	None
Integral Brake	None
Connector	SpeedTEC DIN
Connector Style	Right-angle
Connector Rotation	Approximately 180°
Mounting	IEC metric flange
Frame Size	130 mm
Magnet Stack	101.6 mm
Duty	Continuous industrial servo duty
Motor Construction	Low-inertia design

The approximately 10.2 N·m continuous torque rating makes the motor suitable for many medium-duty servo axes.

The approximately 27.1 N·m peak torque capability provides additional short-duration torque for acceleration, deceleration and transient load conditions.

The approximately 2.6 kW output class provides a useful combination of motor size and mechanical output for automated industrial machinery.

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4. Mechanical Dimensions and Weight

Mechanical Parameter	Specification
Model	MPL-B4540F-SK72AA
Frame Size	130 mm
Frame Diameter/Class	130 mm class
Magnet Stack Length	101.6 mm
Magnet Stack	4.0 in.
Mounting Standard	IEC metric
Mounting Configuration	Free mounting holes, Type FF
Shaft Configuration	Keyless shaft extension
Shaft Key	None
Standard Shaft Seal	None
Connector	SpeedTEC DIN
Connector Position	Right-angle
Connector Rotation	Approximately 180°
Brake	None
Approx. Overall Dimensions	Approx. 204 × 345 × 245 mm class
Approx. Weight	9.07 kg
Approx. Weight in Pounds	20 lb
Installation Envelope	Depends on connector orientation, shaft coupling and mounting arrangement

The 130 mm frame and 101.6 mm magnet stack are the primary dimensions used when evaluating mechanical compatibility.

The approximate motor weight is 9.07 kg.

Because motor dimensions can be presented differently depending on whether the connector, shaft extension and mounting envelope are included, the machine designer should use the applicable dimensional drawing for final mechanical layout.

For practical machine planning, adequate space should be allowed around the shaft, connector and cable routing area.

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5. Model Number Breakdown

The designation MPL-B4540F-SK72AA provides a concise description of the motor configuration.

Model Section	Meaning
MPL	MPL low-inertia servo motor family
B	460 V class motor configuration
45	130 mm frame size
40	101.6 mm magnet stack
F	3000 rpm speed class
S	Single-turn high-resolution encoder
K	Keyless shaft extension
7	SpeedTEC DIN right-angle connector, 180° rotatable
2	No integral brake
AA	Configuration / revision designation

The most important configuration characteristics are therefore:

130 mm frame + 101.6 mm stack + 3000 rpm + single-turn high-resolution feedback + keyless shaft + no brake.

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6. Product Introduction

The MPL-B4540F-SK72AA is designed for servo applications where fast dynamic response, accurate positioning and compact mechanical integration are required.

The low-inertia motor construction allows the rotor to respond quickly to changes in commanded speed.

This is particularly useful in machinery that repeatedly accelerates, decelerates, indexes or reverses direction.

The 3000 rpm operating class provides a good balance between rotational speed and available torque.

With approximately 10.2 N·m of continuous torque and approximately 27.1 N·m of peak torque, the motor can support a wide range of medium-duty motion-control applications.

The single-turn high-resolution encoder provides feedback to the servo controller.

The controller can use this feedback to regulate position, speed and acceleration and to compensate for differences between commanded and actual motor movement.

The keyless shaft is a defining mechanical feature.

Rather than relying on a traditional shaft key, the motor can be integrated with an appropriate clamping coupling or keyless transmission component.

This configuration can be particularly useful where the machine designer wants a concentric mechanical connection and controlled clamping arrangement.

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7. Low-Inertia Design

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

Rotor inertia affects how much torque is required to accelerate or decelerate the motor itself.

A lower motor inertia can allow faster changes in speed and can improve dynamic response.

This characteristic is particularly valuable in:

• High-speed indexing
• Packaging machines
• Pick-and-place equipment
• Assembly equipment
• Labeling machines
• Automated inspection equipment
• Conveyor positioning
• Material handling
• Rotary indexing systems

The low-inertia construction is therefore one of the main reasons this motor is suitable for high-cycle automation.

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8. 3000 RPM Operating Class

The motor is designed for the 3000 rpm operating class.

This speed is widely used in industrial servo applications because it provides substantial mechanical speed while maintaining useful torque.

For belt-driven or gear-driven systems, the 3000 rpm motor speed can be converted into the required machine speed through the appropriate transmission ratio.

The actual machine speed will depend on the coupling, gearbox, pulley ratio, lead screw, belt system or other mechanical transmission.

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9. Continuous Torque Capability

The motor provides approximately 10.2 N·m of continuous stall torque.

This is a useful torque level for medium-duty industrial motion applications.

Continuous torque should be evaluated together with:

• Load torque
• Acceleration torque
• Deceleration torque
• Friction
• Transmission losses
• Duty cycle
• Operating temperature
• Reflected load inertia

A motor should normally be selected with an appropriate engineering margin rather than operated continuously at the absolute torque limit.

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10. Peak Torque Capability

The motor provides approximately 27.1 N·m of peak torque.

Peak torque is important when the machine requires rapid acceleration or deceleration.

For example, an indexing machine may require only moderate torque during constant-speed movement but require substantially more torque during the first portion of the motion cycle.

The additional peak torque capacity allows the servo system to handle short-duration dynamic loads without immediately requiring a larger motor.

The peak torque requirement should be evaluated against the actual motion profile and cycle frequency.

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11. Single-Turn High-Resolution Encoder

The motor uses a single-turn high-resolution encoder.

The feedback system provides the servo drive with motor position and speed information.

This enables closed-loop control.

The controller can compare the commanded position with the actual motor position and continuously adjust motor current and velocity to achieve the required motion.

The high-resolution feedback is useful for applications requiring:

• Repeatable positioning
• Accurate stopping
• Controlled acceleration
• Controlled deceleration
• Coordinated multi-axis movement
• Speed synchronization
• Electronic gearing

The single-turn configuration is appropriate where the application’s position reference is managed within one motor revolution or where the machine’s control architecture provides the required position management.

For applications requiring absolute multi-turn position retention, a multi-turn absolute motor configuration should be considered.

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12. Keyless Shaft Configuration

The K designation identifies the keyless shaft configuration.

This is one of the most important mechanical differences between the SK72AA and keyed-shaft MPL variants.

A keyless shaft can be connected through an appropriate clamping hub, shrink-fit coupling or other suitable keyless transmission system.

A properly selected keyless coupling can provide a concentric mechanical connection without relying on a traditional shaft key.

This can be advantageous for:

• High-speed rotary axes
• Precision positioning
• Belt-drive systems
• Direct coupling
• Compact mechanical assemblies
• Applications requiring simplified shaft alignment

The coupling manufacturer and machine designer must ensure that the selected connection can withstand the required torque, acceleration and operating speed.

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13. No Integral Brake

The 2 designation identifies the no-brake configuration.

The motor does not contain an integral holding brake.

This makes the model particularly appropriate for applications where the load does not need to be mechanically held when the servo drive is disabled.

Typical examples include many horizontal conveyor axes, rotary positioning systems and indexing mechanisms.

For vertical axes, the absence of a brake must be carefully considered.

If a load can move due to gravity after motor torque is removed, an external mechanical holding solution or a brake-equipped motor configuration may be required.

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14. Right-Angle SpeedTEC DIN Connector

The motor uses a SpeedTEC DIN right-angle connector.

The connector arrangement can be rotated through approximately 180°.

This provides useful flexibility when routing the motor cable.

In compact machinery, the direction of the connector can affect:

• Cable bend radius
• Drag-chain routing
• Cabinet access
• Motor-to-motor clearance
• Machine enclosure dimensions

The rotatable connector can therefore simplify mechanical installation without changing the fundamental motor mounting position.

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15. IEC Metric Mounting

The motor uses an IEC metric mounting configuration.

The 130 mm frame provides a standardized mechanical platform.

The free mounting hole arrangement gives machine builders flexibility when designing motor mounting plates.

The mounting structure should have sufficient rigidity to handle the reaction torque generated during acceleration and deceleration.

Correct alignment between the motor shaft and driven mechanism is also important for reducing vibration and bearing loads.

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16. Main Product Advantages

Advantage	Description
Low-inertia construction	Rapid acceleration and deceleration response
3000 rpm speed class	Suitable for high-cycle motion
10.2 N·m continuous torque	Useful for medium-duty servo axes
Approx. 27.1 N·m peak torque	Supports dynamic acceleration
High-resolution feedback	Precise closed-loop control
Keyless shaft	Flexible precision coupling options
No integral brake	Suitable for non-holding axes
130 mm frame	Compact industrial motor platform
101.6 mm stack	Balanced motor size and torque
Rotatable right-angle connector	Flexible cable routing
IEC metric mounting	Convenient mechanical integration
Approx. 9.07 kg	Moderate motor weight

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17. Typical Applications

Application	Typical Requirement	Suitability
Packaging machinery	High-cycle indexing	Excellent
Conveyor positioning	Speed and position control	Excellent
Rotary indexing	Fast acceleration and stopping	Excellent
Pick-and-place equipment	Dynamic response	Excellent
Assembly machinery	Accurate positioning	Excellent
Labeling machines	Repeatable motion	Excellent
Material handling	Controlled positioning	Excellent
Printing machinery	Speed synchronization	Very Good
Inspection equipment	Precise positioning	Excellent
Machine tools	Auxiliary positioning	Very Good
Winding equipment	Controlled speed	Good
General factory automation	Closed-loop motion	Excellent

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18. Packaging Machinery

Packaging equipment is one of the most suitable application areas for a low-inertia servo motor.

Packaging machines frequently operate with short motion cycles and high production rates.

The motor may control:

• Product indexing
• Film movement
• Cutting mechanisms
• Feeding systems
• Labeling mechanisms
• Conveyor positioning
• Rotary indexing

The low-inertia design helps the motor respond rapidly to repeated acceleration and deceleration commands.

The 3000 rpm operating class also provides sufficient speed for many packaging applications.

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19. Conveyor Positioning

The motor can be used for conveyor positioning and indexing applications.

Unlike a basic fixed-speed motor, a servo motor can provide controlled movement to a specific position.

This can be useful when products must be aligned with:

• Filling stations
• Inspection stations
• Pick-and-place systems
• Robotic arms
• Packaging stations
• Assembly tools

The no-brake configuration is generally suitable for horizontal conveyor systems where the load does not need to be mechanically held after power is removed.

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20. Rotary Indexing Systems

Rotary indexing tables often require rapid movement followed by precise stopping.

The low-inertia motor construction supports this type of operation.

The high-resolution feedback allows the servo controller to determine the motor’s actual position.

The keyless shaft can also be useful for direct or semi-direct mechanical coupling to rotary indexing mechanisms.

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21. Pick-and-Place Equipment

Pick-and-place systems require rapid movement between programmed positions.

A low-inertia servo motor can help reduce the time required to accelerate and decelerate the motor.

The high-resolution encoder supports accurate positioning.

The keyless shaft provides a flexible connection to suitable mechanical transmission components.

For vertical pick-and-place axes, however, the no-brake configuration should be evaluated carefully because the motor does not provide an integral holding brake.

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22. Automated Assembly

Assembly machines often use multiple servo axes working together.

Typical movements include:

• Feeding
• Positioning
• Clamping
• Indexing
• Tool movement
• Part transfer

The MPL-B4540F-SK72AA can provide the speed and feedback characteristics required for many of these axes.

The motor is particularly appropriate when the machine axis is horizontally oriented or when an independent mechanical holding mechanism is already present.

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23. Material Handling

Material-handling machinery often requires repeated acceleration and deceleration.

The low-inertia motor can provide good dynamic response for these cycles.

The motor can be used with belts, gearboxes, rollers, pulleys and other transmission components.

For horizontal material-handling axes, the no-brake configuration can be a practical choice.

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24. Printing and Web-Handling Systems

Servo motors used in printing and web-handling systems require accurate speed regulation.

The feedback system allows the controller to monitor motor speed and position.

This makes the motor suitable for applications where multiple machine axes need to remain synchronized.

The 3000 rpm speed class can also support relatively high production throughput.

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25. Machine Tool Applications

The motor can be used for machine-tool auxiliary axes and positioning mechanisms.

Possible applications include:

• Tool positioning
• Indexing
• Automatic loading
• Auxiliary rotary axes
• Feed mechanisms
• Material transfer

For high-precision machine-tool applications, the complete system should be evaluated for load inertia, transmission stiffness, positioning accuracy and servo-loop response.

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26. Application Suitability Guide

Machine Requirement	Suitability of MPL-B4540F-SK72AA
Horizontal servo axis	Excellent
High-speed indexing	Excellent
Packaging equipment	Excellent
Conveyor positioning	Excellent
Rotary indexing	Excellent
Pick-and-place horizontal axis	Excellent
Assembly machine	Excellent
Automated inspection	Very Good
Printing equipment	Very Good
Vertical lifting axis without external brake	Not recommended
Vertical axis with separate holding mechanism	Application dependent
Multi-turn absolute positioning	Consider another feedback configuration

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27. Mechanical Integration

The 130 mm frame size should be matched with the machine’s motor mounting plate.

The 101.6 mm magnet stack determines the active motor body length.

The machine layout should also allow sufficient clearance for the right-angle connector.

The keyless shaft requires a suitable coupling.

The coupling should be selected according to:

• Rated torque
• Peak torque
• Operating speed
• Shaft diameter
• Misalignment
• Axial movement
• Torsional stiffness
• Service factor

The mechanical transmission should be properly aligned to avoid excessive radial or axial loads on the motor shaft.

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28. Keyless Shaft Advantages

A keyless shaft can offer several practical benefits in precision motion systems.

A clamping-type connection can provide a highly concentric connection between the motor and driven component.

It can also eliminate the need to machine or align a conventional keyway in the driven component.

For precision servo systems, torsional stiffness and concentricity can be important.

A suitable keyless coupling can therefore provide a clean mechanical interface for the motor.

However, the keyless connection must be correctly installed and torqued according to the coupling manufacturer’s requirements.

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29. Electrical Integration

The motor is designed for the 460 V AC class and should be connected to an appropriate servo drive.

The servo drive should support the motor’s:

• Voltage class
• Current requirements
• Feedback technology
• Encoder interface
• Speed range
• Torque requirements

The feedback configuration should be checked carefully.

The SK72AA uses single-turn high-resolution feedback, so a drive configured for a fundamentally different feedback architecture should not be assumed to be directly compatible.

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30. Servo Drive and Motion Control

The motor is intended to operate as part of a complete motion-control system.

A typical system consists of:

1. Motion controller
2. Servo drive
3. Motor
4. Encoder feedback
5. Mechanical transmission
6. Machine load

The servo controller determines the desired position and velocity.

The drive converts these commands into controlled motor current.

The motor generates the required mechanical torque.

The encoder provides feedback to close the control loop.

This closed-loop arrangement allows much more precise motion than a simple open-loop motor system.

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31. Thermal Considerations

Thermal performance depends strongly on the machine’s duty cycle.

A motor operating at moderate torque continuously may have a different thermal profile from a motor repeatedly operating at high peak torque.

Important factors include:

• Continuous torque
• Peak torque
• Peak torque duration
• Acceleration rate
• Deceleration rate
• Cycle frequency
• Ambient temperature
• Mounting arrangement
• Motor ventilation
• Machine enclosure

The motor should be evaluated using the complete machine motion profile rather than only the nominal torque requirement.

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32. Load Inertia

Load inertia is one of the most important considerations when selecting a low-inertia servo motor.

The external load inertia must be reflected to the motor shaft through the transmission ratio.

If the reflected load inertia is very high compared with the motor inertia, the system may require additional tuning or a different mechanical ratio.

The motor’s low inertia is beneficial for dynamic response, but the overall motor-load inertia relationship still needs to be properly engineered.

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33. Acceleration and Deceleration

High acceleration requires additional motor torque.

The torque required for acceleration depends on:

• Motor inertia
• Load inertia
• Desired acceleration
• Transmission ratio
• Mechanical efficiency
• Friction
• External load torque

The approximately 27.1 N·m peak torque capability provides useful capacity for short acceleration events.

However, the actual torque requirement should always be calculated from the machine’s motion profile.

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34. No-Brake Configuration Considerations

The absence of an integral brake is both an advantage and a limitation depending on the application.

For horizontal axes, it can simplify the motor configuration.

For vertical axes, it means that the motor cannot mechanically hold a suspended load by means of an integral motor brake.

If the axis can move under gravity, an external holding mechanism or brake-equipped motor should be considered.

The motor’s no-brake configuration is therefore particularly well suited to:

• Horizontal conveyors
• Rotary indexing tables
• Horizontal positioning systems
• Packaging axes
• Printing axes
• Assembly transfer systems
• Non-gravity-loaded machine mechanisms

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35. Environmental Considerations

Before final installation, the complete application environment should be evaluated.

Important considerations include:

• Ambient temperature
• Humidity
• Dust
• Vibration
• Shock
• Chemical exposure
• Cable routing
• Washdown requirements
• Shaft sealing requirements
• Motor mounting orientation

The standard configuration should not automatically be assumed to satisfy every harsh-environment requirement.

Where the application requires enhanced environmental protection, the exact motor configuration should be checked against the machine’s environmental requirements.

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36. Five Recommended Related Models

The following five models are closely related to the MPL-B4540F-SK72AA and provide practical alternatives for different shaft, brake, feedback or torque requirements.

Model	Speed	Continuous Torque	Peak Torque	Power	Feedback	Shaft	Brake	Dimensions	Approx. Weight
MPL-B4540F-SJ72AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	Single-turn high-resolution	Keyed	No	130 × 101.6 mm	Approx. 8.6 kg
MPL-B4540F-SJ74AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	Single-turn high-resolution	Keyed	24 V DC	130 × 101.6 mm	Approx. 9.5 kg
MPL-B4540F-SK74AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	Single-turn high-resolution	Keyless	24 V DC	130 × 101.6 mm	Approx. 12–13 kg
MPL-B4530F-SK72AA	3000 rpm	Approx. 8.25 N·m	Approx. 20.3 N·m	Approx. 2.1 kW	Single-turn high-resolution	Keyless	No	130 × 76.2 mm	Approx. 7.3 kg
MPL-B4560F-SK72AA	3000 rpm	Approx. 14.1 N·m	Approx. 34.4 N·m	Approx. 3.2 kW	Single-turn high-resolution	Keyless	No	130 × 152.4 mm	Approx. 11–12 kg

The MPL-B4540F-SJ72AA is the closest equivalent when a keyed shaft is preferred.

The MPL-B4540F-SJ74AA is the appropriate related configuration when a holding brake is required.

The MPL-B4540F-SK74AA retains the keyless shaft while adding a 24 V DC brake.

The MPL-B4530F-SK72AA provides a shorter stack and lower torque capability.

The MPL-B4560F-SK72AA provides greater torque while retaining the keyless-shaft concept.

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37. Five Same-Brand Popular Models

The following models provide useful reference points across the broader Allen-Bradley servo motor range.

Model	Speed	Continuous Torque	Peak Torque	Power	Feedback	Shaft	Brake	Dimensions	Approx. Weight
MPL-B4540F-MJ74AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	Multi-turn absolute	Keyed	24 V DC	130 × 101.6 mm	Approx. 10–11 kg
MPL-B4540F-MK74AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	Multi-turn absolute	Keyless	24 V DC	130 × 101.6 mm	Approx. 10–12 kg
MPL-B4540F-HJ74AA	3000 rpm	10.2 N·m	27.1 N·m	2.6 kW	High-resolution incremental	Keyed	24 V DC	130 × 101.6 mm	Approx. 11 kg class
MPL-B4560F-MJ74AA	3000 rpm	14.1 N·m	34.4 N·m	3.2 kW	Multi-turn absolute	Keyed	24 V DC	130 × 152.4 mm	Approx. 12–13 kg
MPL-B540K-MJ74AA	4000 rpm	Approx. 19.4 N·m	Approx. 48.6 N·m	Approx. 5.4 kW	Multi-turn absolute	Keyed	24 V DC	Approx. 165 × 101.6 mm class	Approx. 15 kg

These models cover several common servo requirements, including multi-turn feedback, keyless mechanical connections, higher torque and higher-speed operation.

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38. Direct Comparison: SK72AA vs SJ72AA

The most direct alternative to the MPL-B4540F-SK72AA is the keyed-shaft MPL-B4540F-SJ72AA.

Parameter	MPL-B4540F-SK72AA	MPL-B4540F-SJ72AA
Speed	3000 rpm	3000 rpm
Continuous Torque	10.2 N·m	10.2 N·m
Peak Torque	27.1 N·m	27.1 N·m
Rated Power	2.6 kW	2.6 kW
Feedback	Single-turn high-resolution	Single-turn high-resolution
Shaft	Keyless	Keyed
Brake	None	None
Frame	130 mm	130 mm
Stack	101.6 mm	101.6 mm
Approx. Weight	9.07 kg	Approx. 8.6 kg
Typical Mechanical Connection	Clamping/keyless coupling	Keyed coupling

The two motors are closely matched in electrical and servo performance.

The primary difference is the mechanical shaft interface.

If the machine uses a conventional keyed coupling, the SJ72AA is the natural choice.

If the machine uses a clamping hub or keyless coupling, the SK72AA is more appropriate.

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39. Direct Comparison: SK72AA vs SK74AA

Parameter	MPL-B4540F-SK72AA	MPL-B4540F-SK74AA
Speed	3000 rpm	3000 rpm
Continuous Torque	10.2 N·m	10.2 N·m
Peak Torque	27.1 N·m	27.1 N·m
Rated Power	2.6 kW	2.6 kW
Feedback	Single-turn high-resolution	Single-turn high-resolution
Shaft	Keyless	Keyless
Brake	None	24 V DC
Frame	130 mm	130 mm
Stack	101.6 mm	101.6 mm
Approx. Weight	9.07 kg	Approx. 12–13 kg
Typical Use	Horizontal axes	Holding / vertical axes

The two models share the same basic motor performance but differ in brake configuration.

The SK72AA is intended for applications that do not require an integral holding brake.

The SK74AA is more suitable when the machine needs the combination of a keyless shaft and integral 24 V DC holding brake.

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40. Direct Comparison: SK72AA vs SJ74AA

Parameter	MPL-B4540F-SK72AA	MPL-B4540F-SJ74AA
Speed	3000 rpm	3000 rpm
Continuous Torque	10.2 N·m	10.2 N·m
Peak Torque	27.1 N·m	27.1 N·m
Power	2.6 kW	2.6 kW
Feedback	Single-turn high-resolution	Single-turn high-resolution
Shaft	Keyless	Keyed
Brake	None	24 V DC
Frame	130 mm	130 mm
Stack	101.6 mm	101.6 mm
Approx. Weight	9.07 kg	Approx. 9.53 kg
Main Difference	Keyless, no brake	Keyed, brake

The SK72AA is oriented toward non-holding applications where a keyless shaft is desired.

The SJ74AA is better suited to applications where a keyed shaft and holding brake are required.

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41. Direct Comparison: SK72AA vs B4560F

The B4560F family provides a larger motor stack and higher torque capability.

Parameter	MPL-B4540F-SK72AA	MPL-B4560F-SK72AA
Speed	3000 rpm	3000 rpm
Continuous Torque	10.2 N·m	Approx. 14.1 N·m
Peak Torque	27.1 N·m	Approx. 34.4 N·m
Rated Power	2.6 kW	Approx. 3.2 kW
Frame	130 mm	130 mm
Stack	101.6 mm	152.4 mm
Feedback	Single-turn high-resolution	Single-turn high-resolution
Shaft	Keyless	Keyless
Brake	None	None
Approx. Weight	9.07 kg	Approx. 11–12 kg

The B4560F is a logical step when the application needs more continuous torque but can accommodate a longer motor body.

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42. Application Selection Guide

Application Requirement	Recommended Model
Horizontal servo axis + keyless coupling	MPL-B4540F-SK72AA
Horizontal servo axis + keyed coupling	MPL-B4540F-SJ72AA
Vertical axis + keyless shaft	MPL-B4540F-SK74AA
Vertical axis + keyed shaft	MPL-B4540F-SJ74AA
Lower torque requirement	MPL-B4530F-SK72AA
Higher continuous torque	MPL-B4560F-SK72AA
Multi-turn absolute positioning	MPL-B4540F-MK74AA
High-resolution incremental feedback	MPL-B4540F-HJ74AA
Higher-speed / higher-output application	MPL-B540K-MJ74AA

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43. Important Engineering Considerations

Before selecting the MPL-B4540F-SK72AA, the complete machine motion profile should be evaluated.

The continuous torque requirement should be calculated first.

Peak acceleration torque should then be calculated.

The reflected load inertia should be evaluated.

The mechanical coupling must be selected for the required torque and speed.

The feedback system must be compatible with the servo drive.

The machine must also determine whether an integral holding brake is necessary.

Because this model has no brake, special attention should be given to vertical or gravity-loaded mechanisms.

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44. Mechanical Coupling Selection

The keyless shaft configuration requires an appropriate mechanical coupling.

The coupling should be selected based on:

• Motor shaft dimensions
• Driven shaft dimensions
• Continuous torque
• Peak torque
• Maximum speed
• Torsional stiffness
• Radial misalignment
• Angular misalignment
• Axial movement
• Environmental conditions

A properly selected coupling can help transfer torque efficiently while minimizing mechanical vibration.

For precision servo systems, coupling torsional stiffness can also affect positioning response and servo tuning.

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45. Advantages in High-Speed Indexing

High-speed indexing is one of the applications where the MPL-B4540F-SK72AA can provide significant practical benefits.

The motor’s low-inertia rotor allows rapid changes in speed.

The 3000 rpm operating class provides sufficient rotational speed for many indexing mechanisms.

The high-resolution encoder provides accurate feedback.

The keyless shaft can provide a concentric connection to the indexing mechanism when an appropriate coupling is used.

The no-brake configuration is suitable for many horizontal indexing systems.

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46. Advantages in Packaging Machinery

For packaging applications, the combination of low inertia and high-resolution feedback is particularly useful.

Packaging machines often operate continuously with very short motion cycles.

The motor can be used for:

• Feed rollers
• Indexing conveyors
• Film transport
• Cutting systems
• Labeling mechanisms
• Rotary mechanisms
• Product positioning

The absence of a brake is generally not a problem for horizontal machine axes.

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47. Advantages in Assembly Equipment

Automated assembly equipment often requires multiple servo axes with different motion requirements.

The MPL-B4540F-SK72AA can provide:

• Fast response
• Accurate positioning
• Repeatable motion
• High-speed operation
• Closed-loop feedback
• Flexible mechanical coupling

These characteristics make it suitable for many transfer, indexing and positioning axes.

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48. Advantages in Compact Machine Design

The 130 mm frame and 101.6 mm stack provide a relatively compact motor package for the available torque level.

The right-angle connector can further help reduce the space required around the motor.

The keyless shaft can also provide flexibility when designing compact transmission systems.

Together, these features make the motor practical for machinery where both performance and installation space are important.

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49. Advantages for Machine Builders

The MPL-B4540F-SK72AA gives machine builders several useful configuration characteristics in one motor.

The 130 mm frame provides a standardized mechanical platform.

The 101.6 mm stack provides a moderate torque level.

The single-turn encoder provides precise feedback.

The keyless shaft allows flexible coupling arrangements.

The no-brake configuration keeps the motor suited to non-holding axes.

The right-angle rotatable connector provides cable-routing flexibility.

These characteristics make the model a practical choice for a wide variety of automated machinery.

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50. Recommended Use Conditions

The motor is particularly appropriate when:

• The application requires approximately 10 N·m continuous torque.
• The application requires operation around 3000 rpm.
• Fast acceleration and deceleration are important.
• High-cycle motion is required.
• Single-turn high-resolution feedback is suitable.
• A keyless shaft is preferred.
• An integral holding brake is not required.
• A 130 mm frame is compatible with the machine.
• The machine uses a suitable 460 V / 480 V-class servo system.

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51. Applications Where Another Configuration May Be Better

The MPL-B4540F-SK72AA is not the ideal configuration for every machine.

A vertical axis carrying a suspended load may require the MPL-B4540F-SK74AA because it provides an integral brake.

A conventional keyed mechanical connection may favor the MPL-B4540F-SJ72AA.

A keyed shaft plus brake may favor the MPL-B4540F-SJ74AA.

A machine requiring multi-turn absolute feedback may require an M-series motor.

A machine requiring higher continuous torque may require the longer-stack B4560F family.

A higher-speed application may require a different MPL motor configuration.

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52. Key Specifications at a Glance

Key Parameter	MPL-B4540F-SK72AA
Brand	Allen-Bradley
Product Family	MP-Series
Motor Series	MPL Low-Inertia Servo Motors
Product Type	AC Rotary Servo Motor
Voltage Class	460 V AC / 480 V AC class
Rated Speed	3000 rpm
Continuous Torque	Approx. 10.2 N·m
Peak Torque	Approx. 27.1 N·m
Rated Power	Approx. 2.6 kW
Feedback	Single-turn high-resolution encoder
Feedback Resolution	1024 Sin/Cos class
Feedback Protocol	Hiperface-type
Shaft	Keyless
Shaft Key	None
Brake	None
Frame Size	130 mm
Magnet Stack	101.6 mm
Mounting	IEC metric
Connector	SpeedTEC DIN, right-angle
Connector Rotation	Approximately 180°
Shaft Seal	None as standard
Approx. Dimensions	Approx. 204 × 345 × 245 mm class
Approx. Weight	9.07 kg
Typical Application	Industrial servo motion control

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53. Overall Product Evaluation

The Allen-Bradley MPL-B4540F-SK72AA is a medium-frame, low-inertia servo motor designed for precise and dynamic industrial motion control.

Its 130 mm frame and 101.6 mm magnet stack provide a practical combination of physical size and torque capacity.

The approximately 10.2 N·m continuous torque and approximately 27.1 N·m peak torque provide useful performance for medium-duty servo axes.

The 3000 rpm operating class makes the motor suitable for high-cycle machinery.

The single-turn high-resolution encoder provides closed-loop feedback for position and speed control.

The keyless shaft is one of the model’s most distinctive features and makes it suitable for machine designs using clamping-type mechanical connections.

The right-angle SpeedTEC DIN connector, with approximately 180° rotational adjustment, provides useful flexibility for cable routing.

The absence of an integral brake makes the motor especially suitable for horizontal axes and other applications where mechanical load holding is not required.

For vertical or gravity-loaded axes, a brake-equipped configuration should be considered unless an appropriate external holding mechanism is already incorporated into the machine.

Overall, the MPL-B4540F-SK72AA can be characterized as a 130 mm-frame, 3000 rpm, approximately 2.6 kW low-inertia servo motor with approximately 10.2 N·m continuous torque, approximately 27.1 N·m peak torque, single-turn high-resolution feedback, keyless shaft, no integral brake, and a rotatable right-angle SpeedTEC DIN connector.

It is particularly well suited to packaging machinery, indexing systems, horizontal conveyors, automated assembly equipment, pick-and-place systems, material handling, inspection equipment and other industrial applications requiring fast, repeatable and accurately controlled servo motion.