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MPL-B520K-SK72AA Servo Motor

1. Product Overview

The MPL-B520K-SK72AA is a high-speed, low-inertia AC rotary servo motor designed for industrial motion-control applications where fast response, accurate positioning, repeatable movement, and stable closed-loop operation are important.

It belongs to the MP-Series MPL low-inertia brushless servo motor family and uses a 165 mm frame with a 50.8 mm magnetic stack. The motor is designed for the 460 V class and has a 4000 rpm speed configuration. It uses a single-turn high-resolution encoder, a keyless shaft extension, a right-angle SpeedTEC DIN connector with 180-degree rotational capability, and no integrated brake.

The key feature that distinguishes this model from the closely related MPL-B520K-SJ72AA is the shaft arrangement.

The SJ72AA uses a keyed shaft, while the SK72AA uses a keyless shaft.

This makes the SK72AA particularly interesting for machines that use clamping-type couplings, friction-fit mechanical connections, or other keyless transmission arrangements.

The motor’s low-inertia construction is intended for applications that require frequent acceleration and deceleration.

Typical machine movements may include rapid indexing, positioning, reversing, synchronization, pick-and-place operations, and repeated start-stop cycles.

The motor is normally used as part of a complete servo system consisting of a servo drive, motion controller, feedback circuit, motor power connection, mechanical coupling, and driven machine load.

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2. Brand and Product Series

Item	Specification
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Brushless Servo Motors
Product Type	AC Rotary Servo Motor
Motor Construction	Brushless Permanent-Magnet Servo Motor
Voltage Class	460 V
AC Product Designation	480 V AC
Frame Size	165 mm / 6.50 in
Magnetic Stack	50.8 mm / 2.0 in
Speed Class	4000 rpm
Feedback	Single-Turn High-Resolution Encoder
Shaft	Keyless Shaft Extension
Brake	No Brake
Connector	SpeedTEC DIN
Connector Style	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric
Mounting Hole Configuration	Free Mounting Holes / Type FF
Model	MPL-B520K-SK72AA

The product description identifies this model as a 460 V, 165 mm-frame, 50.8 mm-stack, 4000 rpm, single-turn high-resolution servo motor with a keyless shaft, right-angle rotatable SpeedTEC DIN connector, and no brake.

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3. Model Number Explanation

The model number MPL-B520K-SK72AA contains information about the motor’s basic construction and configuration.

Model Section	General Meaning
MPL	MPL low-inertia brushless servo motor family
B	460 V class
5	165 mm frame size
20	50.8 mm magnetic stack
K	4000 rpm speed class
S	Single-turn high-resolution encoder
K	Keyless shaft extension
7	SpeedTEC DIN right-angle connector
2	No brake
AA	Product configuration designation

The model number is particularly useful when comparing similar motors.

For example, the difference between MPL-B520K-SJ72AA and MPL-B520K-SK72AA is primarily the shaft configuration.

The SJ version uses a keyed shaft, while the SK version uses a keyless shaft.

Both are based on the same general B520K motor configuration, making them close alternatives when the electrical and performance requirements are similar.

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4. Main Technical Parameters

Parameter	Specification
Model	MPL-B520K-SK72AA
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia
Motor Type	Brushless AC Rotary Servo Motor
Voltage Class	460 V
AC Designation	480 V AC
Frame Size	165 mm / 6.50 in
Magnetic Stack Length	50.8 mm / 2.0 in
Maximum / Rated Speed Class	4000 rpm
Rated Motor Speed	4000 rpm configuration
Continuous Stall Torque	Approx. 10.7 N·m
Peak Stall Torque	Approx. 23 N·m
Power Class	Approx. 3.5 kW
Feedback	Single-Turn High-Resolution Encoder
Feedback Type	Absolute Single-Turn
Encoder Configuration	1024 Sin/Cos
Feedback Protocol	Hiperface
Shaft	Keyless Shaft Extension
Shaft Key	None
Shaft Seal	None
Brake	No Brake
Connector	SpeedTEC DIN
Connector Orientation	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric
Mounting Holes	Free Mounting Holes / Type FF
Frame Dimension	165 mm
Stack Dimension	50.8 mm
Approx. Weight	5.44 kg / 12.0 lb in some published listings
Other Listed Shipping Weights	Some distributors list different packaged weights
Overall Envelope	Verify with the applicable mechanical drawing
Primary Application	Industrial servo motion control

The basic motor data identifies the B520K configuration as a 4000 rpm, approximately 3.5 kW motor with approximately 10.7 N·m rated torque and approximately 23 N·m peak torque in the applicable motor/drive selection data.

The most consistent product-level specifications are the 165 mm frame, 50.8 mm magnetic stack, 4000 rpm speed, single-turn high-resolution encoder, keyless shaft, SpeedTEC DIN right-angle connector, and no brake.

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5. Dimensions and Mechanical Specifications

The MPL-B520K-SK72AA uses a 165 mm frame and a 50.8 mm magnetic stack.

These dimensions identify the main motor size within the MPL family.

Mechanical Parameter	Specification
Model	MPL-B520K-SK72AA
Frame Size	165 mm
Frame Size in Inches	6.50 in
Magnetic Stack Length	50.8 mm
Magnetic Stack in Inches	2.0 in
Mounting Standard	IEC Metric
Mounting Hole Style	Free Mounting Holes / Type FF
Shaft Configuration	Keyless
Shaft Key	None
Shaft Seal	None
Connector	SpeedTEC DIN
Connector Position	Right Angle
Connector Rotation	180°
Brake	None
Motor Frame	165 mm class
Overall Motor Envelope	Confirm from mechanical drawing
Installation Clearance	Must include connector and cable-routing space

The 165 mm frame and 50.8 mm stack length are directly associated with the B520K configuration.

The exact overall outside dimensions should not be inferred simply from the frame and stack dimensions.

For a machine drawing, the shaft projection, flange dimensions, mounting-hole locations, connector position, motor body length, and cable bend radius all need to be considered.

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6. Weight

Weight information for this model should be handled carefully because published listings are not completely consistent.

One commonly published specification lists the motor at approximately 12.00 lb, equivalent to approximately 5.44 kg.

Other commercial listings show substantially different figures that appear to represent packaged, shipping, or catalog-level weights rather than the bare motor itself.

For a clean product specification, the commonly listed motor weight can therefore be presented as:

Weight Parameter	Value
Model	MPL-B520K-SK72AA
Listed Motor Weight	Approx. 12.00 lb
Metric Equivalent	Approx. 5.44 kg
Packaging Weight	May be higher
Installation Weight	Use actual supplied unit for final structural calculations

For machine-frame calculations, it is preferable to use the actual motor’s nameplate or dimensional documentation if the weight is critical to the design.

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7. Electrical Characteristics

The MPL-B520K-SK72AA is a high-voltage AC servo motor in the 460 V class.

It is designed for use with a compatible servo drive rather than direct operation from a conventional motor starter.

Electrical Parameter	Specification
Model	MPL-B520K-SK72AA
Voltage Class	460 V
AC Product Designation	480 V AC
Supply Type	AC
Motor Type	Permanent-Magnet Servo Motor
Phase	Three-phase servo application
Power Class	Approx. 3.5 kW
Speed	4000 rpm
Continuous Torque Class	Approx. 10.7 N·m
Peak Torque Class	Approx. 23 N·m
Feedback	Absolute single-turn encoder
Brake	None
Control Type	Closed-loop servo control

Published product data identifies the motor as a 460 V-class servo motor with a 4000 rpm speed rating and approximately 3.5 kW power class.

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8. Low-Inertia Motor Construction

The low-inertia design is one of the main reasons to choose an MPL motor for dynamic motion applications.

In a conventional rotating system, the motor rotor itself has inertia.

Whenever the machine accelerates, the servo drive must provide torque to accelerate both the external load and the motor rotor.

When the rotor inertia is relatively low, the motor can respond more quickly to changes in the commanded speed.

This becomes especially valuable when the machine performs rapid repetitive movements.

For example, a packaging machine may accelerate a mechanism, move it to a target location, stop, reverse direction, and immediately begin another cycle.

The lower inertia of the servo motor helps support this type of operating pattern.

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9. 4000 RPM High-Speed Operation

The motor has a 4000 rpm speed configuration.

This makes it suitable for high-speed motion applications where machine productivity depends on rapid axis movement.

High motor speed can also reduce the amount of mechanical reduction needed in certain machine architectures.

However, the complete mechanical transmission must be evaluated.

The coupling, gearbox, pulley, belt, screw, bearings, and driven load must all be suitable for the intended operating speed.

A servo motor should therefore always be selected based on the complete motion system rather than speed alone.

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10. Single-Turn High-Resolution Encoder

The MPL-B520K-SK72AA uses a single-turn high-resolution encoder.

Published specifications commonly describe the feedback as a 1024 Sin/Cos absolute single-turn encoder using Hiperface protocol.

The encoder provides the servo system with information about actual motor position and movement.

This feedback is essential for closed-loop operation.

The controller can compare the commanded position with the actual position and adjust the drive output accordingly.

This allows the motor to perform controlled acceleration, deceleration, positioning, and speed regulation.

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11. Keyless Shaft Extension

The keyless shaft is the defining mechanical feature of the SK configuration.

Unlike a keyed shaft, the keyless shaft does not use a traditional shaft key to transmit torque.

Instead, a compatible clamping coupling or friction-based mechanical connection is normally used.

Shaft Parameter	Specification
Model	MPL-B520K-SK72AA
Shaft Type	Keyless
Shaft Key	None
Shaft Seal	None
Mechanical Connection	Suitable clamping/friction coupling
Main Advantage	Flexible precision coupling arrangement
Typical Use	Servo coupling and precision motion systems
Replacement Consideration	Existing coupling must be compatible

A keyless shaft can provide a clean mechanical interface and can be especially useful with precision couplings designed specifically for servo applications.

The absence of a shaft key can also reduce the possibility of mechanical play associated with an improperly fitted key and hub.

However, correct coupling selection and installation are essential.

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12. Keyless Shaft vs. Keyed Shaft

The keyless configuration should not be viewed as universally better than a keyed shaft.

The two configurations are intended for different mechanical designs.

Feature	MPL-B520K-SK72AA Keyless	Keyed Version
Shaft Key	None	Present
Coupling Type	Clamping / friction type	Keyed coupling
Mechanical Precision	Excellent with proper coupling	Excellent with proper coupling
Conventional Machine Compatibility	Moderate	High
Existing Keyed Equipment	May require modification	Very suitable
Servo Precision Coupling	Very suitable	Also suitable
Installation	Requires proper clamping procedure	Conventional
Main Advantage	Clean keyless connection	Familiar mechanical interface

For a new machine design, the keyless configuration can be attractive when the mechanical engineer is already using precision clamping couplings.

For a replacement application, however, the existing shaft and coupling should be checked first.

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13. No-Brake Configuration

The MPL-B520K-SK72AA is a no-brake motor.

This means there is no integrated holding brake on the motor shaft.

A no-brake configuration can be advantageous for applications where the mechanical load does not need to be held after servo torque is removed.

It also simplifies the motor configuration.

Brake Parameter	Specification
Model	MPL-B520K-SK72AA
Integrated Brake	No
Holding Brake	None
Brake Supply	Not applicable
Typical Application	Horizontal motion
Main Benefit	Simple motor configuration
Vertical Axis Requirement	May require separate holding mechanism

For vertical or gravity-loaded axes, the absence of a brake must be considered carefully.

If the machine can move when servo torque is removed, a separate mechanical holding solution may be required.

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14. SpeedTEC DIN Right-Angle Connector

The motor uses a SpeedTEC DIN connector with a right-angle configuration and 180-degree rotational capability.

This is particularly useful in compact machinery.

A straight connector may require considerable space behind the motor.

A right-angle connector allows the cable to leave the motor in a direction that can better suit the machine layout.

The 180-degree rotational capability also gives the installer additional flexibility.

This can simplify cable routing and help prevent the motor cable from interfering with adjacent machine components.

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15. IEC Metric Mounting

The motor uses an IEC metric mounting arrangement with free mounting holes identified as Type FF.

This is useful for industrial machinery designed around metric mechanical dimensions.

The mounting plate should be sufficiently rigid to handle the motor’s static weight and dynamic reaction forces.

Servo motors can generate rapid torque changes during acceleration and deceleration.

A weak mounting structure can introduce vibration, mechanical resonance, or positioning errors.

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16. Typical Applications

The MPL-B520K-SK72AA can be used in many industrial motion-control applications.

Its most useful characteristics are its low-inertia design, 4000 rpm speed capability, single-turn high-resolution feedback, keyless shaft, and compact right-angle connector arrangement.

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16.1 Packaging Machinery

Packaging machines often require rapid and repeatable motion.

A typical packaging cycle may involve:

• Product positioning
• Film feeding
• Cutting
• Sealing
• Indexing
• Product transfer
• Label positioning

These operations often require the motor to accelerate and decelerate repeatedly.

The low-inertia design is well suited to this type of application.

The 4000 rpm speed class can also help reduce cycle time where the machine requires rapid rotary motion.

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16.2 Automated Assembly Equipment

Automated assembly machines use servo motors to position components accurately.

The motor may drive a linear slide, rotary table, insertion mechanism, or transfer unit.

The encoder provides the feedback required for accurate closed-loop control.

The keyless shaft can be advantageous when the machine uses a precision clamping coupling.

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16.3 CNC Equipment

CNC machines require precise motion and repeatable positioning.

The motor can be used for appropriate machine axes where the required torque and speed fall within its operating range.

The high-speed configuration is particularly useful for rapid positioning movements.

Actual CNC suitability depends on the axis load, screw pitch, cutting force, gearbox ratio, reflected inertia, and servo tuning.

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16.4 Indexing Machines

Indexing systems repeatedly move between defined positions.

Examples include:

• Rotary indexing tables
• Assembly stations
• Transfer systems
• Automated inspection stations
• Filling machines
• Production-line positioning mechanisms

The low-inertia design supports rapid acceleration and deceleration.

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16.5 Pick-and-Place Equipment

Pick-and-place machines require rapid movement between two or more locations.

Reducing unnecessary motor inertia can help the servo system respond quickly.

This can improve machine cycle time when properly matched to the load.

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16.6 Material Handling

Servo motors can be used in automated material transfer systems where conventional constant-speed motors do not provide sufficient positioning control.

The motor can control:

• Transfer conveyors
• Positioning axes
• Rotary tables
• Lift mechanisms with external holding systems
• Sorting mechanisms
• Automated transfer stations

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16.7 Printing and Converting Machinery

Printing and converting equipment often requires synchronized motion between multiple machine sections.

Servo motors can be used to control speed and position precisely.

The high-speed capability of the MPL-B520K-SK72AA makes it suitable for appropriate high-cycle applications.

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17. Main Product Advantages

Advantage	Description
Low-Inertia Design	Supports rapid acceleration and deceleration
4000 rpm Speed	Suitable for high-speed motion
High-Resolution Feedback	Supports accurate closed-loop control
Single-Turn Absolute Encoder	Provides absolute position information within one revolution
Keyless Shaft	Well suited to precision clamping couplings
No Brake	Simple configuration for applications without holding-brake requirements
Right-Angle Connector	Helps reduce installation space
180° Connector Rotation	Improves cable-routing flexibility
165 mm Frame	Provides a substantial industrial motor platform
50.8 mm Stack	Short-stack configuration within the frame class
IEC Metric Mounting	Suitable for metric machine construction
Approx. 5.44 kg Listed Motor Weight	Relatively manageable motor mass
3.5 kW Class	Suitable for substantial industrial motion applications
10.7 N·m Torque Class	Useful for medium-duty servo motion
Peak Torque Capability	Supports short-duration acceleration demands

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18. Advantage of the Keyless Shaft

The keyless shaft is particularly useful in precision motion systems.

A suitable clamping coupling can provide a rigid mechanical connection between the motor and driven load.

This arrangement can reduce mechanical play and is commonly preferred for certain precision servo applications.

The absence of a key also eliminates the need to align a keyway between the motor shaft and the coupling hub.

However, the coupling must be installed according to its specified tightening and alignment requirements.

Incorrect installation can cause shaft slip, vibration, coupling damage, or inaccurate motion.

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19. Advantage of Low Inertia in Repetitive Motion

Low inertia becomes particularly valuable when the machine repeatedly changes speed.

Suppose an indexing axis accelerates to operating speed, stops at a target location, waits briefly, and then accelerates again.

The motor must continuously change its rotational state.

A low-inertia rotor makes those changes easier for the servo drive to control.

This is why low-inertia motors are commonly associated with high-cycle machinery.

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20. Advantage of High-Speed Operation

A 4000 rpm speed class provides a useful combination of speed and motor size.

For applications where machine output depends on cycle time, high rotational speed can help shorten motion periods.

It can also provide greater flexibility when selecting mechanical reduction ratios.

The actual machine speed must still be determined by the complete mechanical system.

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21. Advantage of Single-Turn Absolute Feedback

The single-turn absolute encoder provides the control system with absolute position information within one motor revolution.

This can be useful for rotary positioning and for machine axes where the control architecture handles the overall machine reference position.

The high-resolution feedback also supports smooth speed control.

For applications requiring position tracking over multiple motor revolutions without losing absolute information, a multi-turn configuration from the same family may be more appropriate.

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22. Advantage of the Compact Connector Arrangement

The right-angle connector is useful when the motor is installed close to:

• Machine guards
• Structural brackets
• Other motors
• Gearboxes
• Cable trays
• Moving mechanisms

The 180-degree rotational feature provides additional freedom when choosing the cable exit direction.

This can make the motor easier to install in compact automation equipment.

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23. Five Same-Series or Closely Related Models

The following models are useful alternatives when comparing the MPL-B520K-SK72AA with nearby configurations.

Model	Series	Frame	Stack	Speed	Feedback	Shaft	Brake	Main Difference
MPL-B520K-SJ72AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyed	No	Keyed shaft
MPL-B520K-SJ74AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyed	24 V DC	Keyed + brake
MPL-B520K-SK72AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyless	No	Reference model
MPL-B520K-SK74AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyless	24 V DC	Keyless + brake
MPL-B540K-SK72AA	MPL Low-Inertia	165 mm	101.6 mm	4000 rpm	Single-turn	Keyless	No	Longer stack / higher output class

The first four models are particularly close because they share the B520K basic configuration.

The shaft and brake options provide the primary differences.

The B540K family uses a longer magnetic stack and therefore moves into a higher motor-output class while retaining the 165 mm frame family.

The published motor selection data lists the B520K at approximately 10.7 N·m continuous torque and 3.5 kW, while the B540K configuration is approximately 19.4 N·m and 5.4 kW.

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24. Five Popular Models for Broader Brand Comparison

Model	Product Family	Frame Class	Stack	Speed	Torque Class	Feedback	Shaft	Brake
MPL-B520K-SK72AA	MP-Series MPL	165 mm	50.8 mm	4000 rpm	10.7 N·m	Single-turn	Keyless	No
MPL-B520K-SJ72AA	MP-Series MPL	165 mm	50.8 mm	4000 rpm	10.7 N·m	Single-turn	Keyed	No
MPL-B540K-MJ72AA	MP-Series MPL	165 mm	101.6 mm	4000 rpm	19.4 N·m class	Multi-turn	Keyed	No
MPL-B560F-MJ72AA	MP-Series MPL	165 mm class	152.4 mm	3000 rpm	26.8 N·m class	Multi-turn	Keyed	No
MPL-B580F-MJ72AA	MP-Series MPL	Larger frame	Extended stack	3000 rpm	34.0 N·m class	Multi-turn	Keyed	No

These models cover several different motor-output levels.

The B520K configuration is a good choice when high speed and relatively compact motor construction are priorities.

The B540K configuration moves toward higher torque while retaining 4000 rpm operation.

The B560F and B580F configurations move further toward higher torque and larger motor capacity, with a lower 3000 rpm speed class.

The selection data lists approximately 10.7 N·m for B520K, 19.4 N·m for B540K, 26.8 N·m for B560F, and 34.0 N·m for B580F.

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25. B520K Family Comparison

Feature	MPL-B520K-SK72AA	MPL-B520K-SJ72AA	MPL-B520K-SK74AA	MPL-B520K-SJ74AA
Frame	165 mm	165 mm	165 mm	165 mm
Stack	50.8 mm	50.8 mm	50.8 mm	50.8 mm
Speed	4000 rpm	4000 rpm	4000 rpm	4000 rpm
Feedback	Single-turn	Single-turn	Single-turn	Single-turn
Shaft	Keyless	Keyed	Keyless	Keyed
Brake	No	No	24 V DC	24 V DC
Connector	Right-angle DIN	Right-angle DIN	Right-angle DIN	Right-angle DIN
Best Feature	Keyless simplicity	Keyed compatibility	Keyless + brake	Keyed + brake

The four B520K models provide a useful combination of mechanical choices.

If the machine uses a keyless coupling and does not need a brake, the SK72AA is the logical configuration.

If the same machine requires a holding brake, the SK74AA is the more suitable choice.

If the machine uses a traditional keyed coupling, the SJ72AA or SJ74AA may be more appropriate depending on whether a brake is required.

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26. Keyless Coupling Applications

The SK72AA is particularly suitable for machinery that uses precision servo couplings.

Typical applications include:

• Ball-screw drives
• Linear stages
• Precision positioning tables
• Rotary indexing systems
• Servo-driven gearboxes
• Direct mechanical couplings
• Automated inspection mechanisms

A properly selected keyless coupling can provide a rigid and accurate connection between the motor shaft and driven mechanism.

This can be particularly useful where backlash and mechanical play need to be minimized.

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27. CNC and Linear-Axis Applications

A servo motor is often connected to a ball screw through a coupling.

In this arrangement, the motor rotates the ball screw and the ball screw converts rotary motion into linear movement.

The MPL-B520K-SK72AA can be considered for suitable linear axes where the required torque and speed fall within the motor’s operating range.

The keyless shaft can work well with a precision clamping coupling.

The servo feedback system then allows the drive to regulate motor position and speed.

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28. Rotary Indexing Applications

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

A low-inertia 4000 rpm motor can be useful for this type of operation.

The motor can accelerate the table through a mechanical transmission and then decelerate it to the target position.

The encoder provides the feedback needed for closed-loop control.

The exact performance depends on the indexing-table inertia and transmission ratio.

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29. High-Cycle Automation

High-cycle automation is one of the strongest application areas for this motor.

A machine operating continuously may perform tens of thousands or even millions of motion cycles over its service life.

In such machinery, the motor needs to withstand repeated acceleration and deceleration while maintaining predictable motion.

Low-inertia construction is particularly useful in this environment.

Correct servo tuning, mechanical alignment, lubrication, thermal management, and appropriate load sizing are equally important for long-term reliability.

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30. Machine Integration

A typical installation may include:

1. Motion controller
2. Servo drive
3. Motor power cable
4. Feedback cable
5. MPL-B520K-SK72AA motor
6. Keyless coupling
7. Gearbox or direct-drive mechanism
8. Driven load
9. Machine safety system
10. Proper grounding and cable management

The motor should be considered one component within this complete system.

A correctly selected motor can still perform poorly if the coupling is incorrectly installed, the load inertia is excessive, or the servo drive is poorly tuned.

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31. Mechanical Installation Considerations

The motor mounting structure should be rigid.

Servo systems can generate rapid changes in torque.

If the mounting plate flexes, the machine can experience vibration or positioning errors.

The coupling should be accurately aligned.

Misalignment can place excessive radial or axial loads on the motor bearings.

Cable routing should also be considered.

The right-angle connector helps with cable positioning, but the cable should still have sufficient bend radius and should not be exposed to unnecessary mechanical stress.

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32. Environmental Considerations

The motor’s installation environment should be considered carefully.

Important factors include:

• Ambient temperature
• Dust
• Oil
• Coolant
• Humidity
• Vibration
• Shock
• Cable contamination
• Mechanical impact

The motor’s standard enclosure arrangement should be checked against the actual machine environment.

Where additional protection is required, the machine may need suitable guarding or environmental protection.

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33. Maintenance Considerations

Servo motors generally require less routine mechanical maintenance than many mechanically commutated motor designs, but the complete installation still requires inspection.

Important inspection points include:

• Coupling condition
• Shaft alignment
• Mounting bolts
• Motor temperature
• Cable condition
• Connector condition
• Encoder feedback stability
• Bearing condition
• Mechanical vibration
• Servo following error

Early detection of abnormal vibration, temperature, or feedback behavior can help prevent larger machine problems.

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34. Important Replacement Considerations

When replacing an existing servo motor, do not compare only the model number’s voltage and speed.

The following characteristics should all be checked:

Replacement Parameter	Requirement
Model	MPL-B520K-SK72AA
Voltage	460 V class
Frame	165 mm
Stack	50.8 mm
Speed	4000 rpm
Feedback	Single-turn high-resolution
Shaft	Keyless
Brake	None
Connector	SpeedTEC DIN right angle
Mounting	IEC Metric
Mechanical Coupling	Must support keyless shaft
Torque	Must meet machine load requirement
Inertia	Must be suitable for load inertia
Weight	Approx. 5.44 kg listed motor value
Overall Dimensions	Must match installation envelope

The shaft configuration is particularly important.

A keyed motor and keyless motor should not automatically be considered direct mechanical replacements for one another.

The coupling must match the actual motor shaft.

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35. Selection by Application

Application	Recommended Configuration
High-speed horizontal axis	MPL-B520K-SK72AA
Precision ball-screw axis	MPL-B520K-SK72AA
Keyless precision coupling	MPL-B520K-SK72AA
Rotary indexing	MPL-B520K-SK72AA
Packaging machine	MPL-B520K-SK72AA
Keyed mechanical coupling	MPL-B520K-SJ72AA
Keyless shaft + brake	MPL-B520K-SK74AA
Keyed shaft + brake	MPL-B520K-SJ74AA
Higher torque requirement	MPL-B540K family
Higher torque + lower speed	MPL-B560F / B580F family

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36. Product Advantages at a Glance

Feature	Benefit
165 mm Frame	Provides a substantial industrial motor platform
50.8 mm Stack	Compact B520K stack configuration
4000 rpm	Supports fast machine cycles
3.5 kW Class	Suitable for medium-duty industrial motion
10.7 N·m Torque Class	Provides useful continuous torque
High Peak Torque	Supports rapid acceleration
Low Inertia	Improves dynamic response
Single-Turn Feedback	Provides accurate position feedback
Keyless Shaft	Works well with precision clamping couplings
No Brake	Simplifies applications that do not require holding
Right-Angle Connector	Helps in compact machine layouts
180° Rotation	Improves cable-routing flexibility
IEC Metric Mounting	Suitable for metric industrial machinery

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37. Final Technical Specification

Category	Specification
Model	MPL-B520K-SK72AA
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Brushless Servo Motors
Product Type	AC Rotary Servo Motor
Voltage Class	460 V
AC Designation	480 V AC
Frame Size	165 mm / 6.50 in
Magnetic Stack	50.8 mm / 2.0 in
Speed	4000 rpm
Power Class	Approx. 3.5 kW
Continuous Torque Class	Approx. 10.7 N·m
Peak Torque Class	Approx. 23 N·m
Feedback	Single-turn high-resolution encoder
Feedback Type	Absolute single-turn
Encoder	1024 Sin/Cos
Feedback Protocol	Hiperface
Shaft	Keyless shaft extension
Shaft Key	None
Shaft Seal	None
Brake	No brake
Connector	SpeedTEC DIN
Connector Style	Right angle
Connector Rotation	180°
Mounting	IEC Metric
Mounting Holes	Free Mounting Holes / Type FF
Frame Dimension	165 mm
Stack Dimension	50.8 mm
Listed Motor Weight	Approx. 5.44 kg
Listed Weight	12.0 lb
Main Application	Industrial motion control
Primary Characteristics	Low inertia, high speed, precision feedback, keyless shaft

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38. Conclusion

The MPL-B520K-SK72AA is a high-speed, low-inertia servo motor intended for industrial motion applications where rapid response, precise feedback, and reliable mechanical transmission are important.

Its principal configuration consists of a 165 mm frame, 50.8 mm magnetic stack, 4000 rpm speed class, single-turn high-resolution encoder, keyless shaft extension, right-angle SpeedTEC DIN connector, and no integrated brake.

The keyless shaft is the most distinctive mechanical characteristic of this model.

It makes the motor particularly suitable for applications using precision clamping couplings rather than conventional keyed couplings.

The low-inertia rotor design supports rapid acceleration and deceleration.

The 4000 rpm speed capability makes the motor suitable for high-cycle machinery.

The single-turn high-resolution encoder provides the feedback required for closed-loop servo control.

The right-angle connector helps simplify installation in compact machinery.

The no-brake configuration keeps the motor relatively straightforward for applications where a holding brake is not required.

With an approximately 3.5 kW power class and 10.7 N·m continuous torque class, the B520K configuration occupies a useful position in the MPL motor range between smaller compact servo motors and larger, higher-torque configurations.

For applications requiring a similar motor but a keyed shaft, the MPL-B520K-SJ72AA is the natural comparison.

For applications requiring a keyless shaft together with a holding brake, the MPL-B520K-SK74AA is the more appropriate related configuration.

When higher torque is required, the longer-stack B540K family can provide a higher output class while retaining the general 165 mm frame concept.

Overall, the MPL-B520K-SK72AA is best suited to high-speed industrial automation, precision positioning, packaging machinery, assembly equipment, indexing systems, CNC-related motion, material handling, and servo-driven linear or rotary mechanisms where a keyless mechanical connection is preferred.