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MPL-B540K-SJ74AA Low-Inertia Servo Motor

1. Product Overview

The MPL-B540K-SJ74AA is a high-performance low-inertia rotary servo motor from the MP-Series MPL servo motor family. It is designed for industrial motion-control systems that require accurate positioning, high rotational speed, strong torque capability, and repeatable dynamic performance.

The motor is part of the frame-5 MPL range and uses a 165 mm frame size with a 101.6 mm magnet stack length. It operates in the 400 V AC class and is designed for the 460/480 V-class MPL servo system environment. The motor has a 4000 rpm rated and maximum speed, making it particularly suitable for high-speed positioning and production machinery.

The B540K motor family provides approximately 19.4 N·m continuous stall torque, 48.6 N·m peak torque, and 5.4 kW rated output. These characteristics place the B540K in a useful middle-to-high performance range within the MPL family: it provides considerably more torque than the smaller B520K while remaining faster and lighter than many of the larger high-torque MPL motors.

The SJ74AA configuration is particularly identifiable by its single-turn high-resolution absolute encoder, keyed shaft, 24 V DC holding brake, and right-angle SpeedTEC DIN connector with 180° rotation capability. The combination is well suited to machines where precise single-turn position feedback and a mechanical holding brake are both required.

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2. Brand

Brand: Allen-Bradley

The MPL-B540K-SJ74AA belongs to the industrial automation and motion-control product range associated with the Allen-Bradley brand.

When identifying or replacing this motor, the complete catalog number should be used:

MPL-B540K-SJ74AA

The complete suffix is important because other B540K models may have different feedback arrangements, shaft configurations, brake options, or connector configurations.

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3. Product Series

Product Series: MP-Series MPL

Product Type: Low-Inertia Brushless Servo Motor

The MPL family is intended for industrial servo applications where the motor must operate under controlled speed, torque, and position conditions.

The B540K section of the family is characterized by a 4000 rpm speed class, approximately 19.4 N·m continuous torque, approximately 48.6 N·m peak torque, and approximately 5.4 kW rated output.

Compared with smaller MPL motors, the B540K provides substantially greater torque. Compared with larger F-series motors, it provides a relatively high-speed operating range and a comparatively compact motor package.

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4. Complete Model Identification

Parameter	Specification
Model	MPL-B540K-SJ74AA
Brand	Allen-Bradley
Product Series	MP-Series MPL
Motor Type	Low-Inertia Brushless Rotary Servo Motor
Voltage Class	400 V AC
System Voltage Class	460/480 V class
Frame Size	Frame 5
Frame Dimension	165 mm
Magnet Stack Length	101.6 mm
Maximum Speed	4000 rpm
Rated Speed	4000 rpm
Rated Output	5.4 kW
Continuous Stall Torque	19.4 N·m
Peak Stall Torque	48.6 N·m
Rotor Inertia	Approximately 0.00157 kg·m²
Feedback	Absolute single-turn
Feedback Resolution	1024 Sin/Cos cycles/rev
Feedback Protocol	Hiperface
Shaft	Keyed shaft extension
Brake	24 V DC integral brake
Connector	SpeedTEC DIN
Connector Orientation	Right angle
Connector Rotation	180° rotatable
Mounting	IEC metric flange mount
Mounting Holes	Free mounting holes, Type FF
Shaft Seal	No
Maximum Operating Temperature	40 °C
Approximate Weight	Approximately 19 kg with brake
Magnet Stack Code	40
Application	Industrial servo motion

The exact product description identifies the SJ74AA configuration as a frame-5, 165 mm motor with a 101.6 mm stack, 4000 rpm operation, single-turn high-resolution feedback, keyed shaft, SpeedTEC DIN right-angle connector, 24 V DC brake, and metric mounting.

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5. Main Technical Parameters

Technical Parameter	MPL-B540K-SJ74AA
Model	MPL-B540K-SJ74AA
Rated Output	5.4 kW
Rated Speed	4000 rpm
Maximum Speed	4000 rpm
Continuous Stall Torque	19.4 N·m
Peak Torque	48.6 N·m
Continuous Stall Current	Approximately 20.5 A, 0-peak
Rotor Inertia	Approximately 0.00157 kg·m²
Voltage Class	400 V AC
Armature Voltage	460 V
Frame Size	165 mm
Magnet Stack Length	101.6 mm
Feedback	Absolute single-turn
Encoder Resolution	1024 Sin/Cos cycles/rev
Feedback Protocol	Hiperface
Shaft	Keyed
Brake	24 V DC
Shaft Seal	No
Connector	SpeedTEC DIN
Connector Type	Right angle
Connector Rotation	180°
Mounting	IEC metric
Mounting Holes	Free mounting holes, Type FF
Operating Temperature	Maximum 40 °C
Approximate Weight	Approximately 19 kg
Motor Construction	Low-inertia brushless servo
Intended Duty	Industrial servo motion

The B540K performance figures of 4000 rpm, 19.4 N·m continuous torque, 48.6 N·m peak torque, and 5.4 kW output are established by the B540K technical data.

The SJ74AA version adds the 24 V DC brake and keyed-shaft configuration.

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6. Dimensions

The confirmed primary mechanical dimensions for this motor are the 165 mm frame size and 101.6 mm magnet stack length.

Dimension Item	Specification
Model	MPL-B540K-SJ74AA
Frame Size	165 mm
Frame Size in Inches	6.50 in
Magnet Stack Length	101.6 mm
Magnet Stack Length in Inches	4.0 in
Mounting Standard	IEC metric
Mounting Style	Flange mount
Mounting Hole Type	Free mounting holes, Type FF
Shaft Type	Keyed
Shaft Projection	Refer to mechanical drawing
Flange Dimensions	Refer to mechanical drawing
Overall Motor Envelope	Refer to mechanical drawing
Connector Clearance	Allow additional installation space
Brake Housing	Included in overall mechanical arrangement

The 165 mm frame and 101.6 mm stack are directly identified in the product configuration.

It is important not to treat the 165 mm frame size as the complete overall motor length. The total installation envelope also depends on the shaft extension, mounting flange, rear housing, brake assembly, connector, and required cable clearance.

For machine design, the mechanical drawing should therefore be used for the exact overall length, shaft dimensions, mounting-hole spacing, flange dimensions, and connector clearance.

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7. Weight

The MPL-B540K-SJ74AA includes an integral 24 V DC brake, so its actual configuration weight is higher than the basic no-brake B540K motor.

The B540K family is approximately 15 kg in its basic configuration, while the brake-equipped version is approximately 19 kg, depending on the specific catalog configuration and measurement convention. Family documentation notes that brake rotor inertia and brake motor weight are configuration-dependent.

Weight Parameter	Specification
Model	MPL-B540K-SJ74AA
Basic B540K Motor Reference	Approximately 15 kg
Brake-Equipped Configuration	Approximately 19 kg
Approximate Weight in Pounds	Approximately 42 lb
Integral Brake	Yes
Brake Voltage	24 V DC
Shipping Weight	Higher than motor-only weight

For machine-frame calculations, the brake-equipped weight should be used rather than the approximately 15 kg no-brake family value.

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8. Motor Power

The MPL-B540K-SJ74AA is a 5.4 kW rated-output servo motor.

This output level makes it suitable for demanding industrial motion applications where smaller motors may not provide sufficient continuous torque.

The motor is especially useful when a machine requires both substantial torque and a relatively high rotational speed.

The 5.4 kW rating also gives the B540K a useful position between lower-power motors such as the B520K and higher-torque models such as the B560F and B580F.

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9. Speed Performance

The rated and maximum speed of the MPL-B540K-SJ74AA are approximately 4000 rpm.

This high-speed capability makes the motor suitable for production equipment where cycle time and rapid mechanical movement are important.

Typical applications include:

• High-speed packaging
• Rotary indexing
• Conveyor positioning
• Ball-screw positioning
• Automated assembly
• Material handling
• Machine-tool feed axes
• High-speed inspection mechanisms

The 4000 rpm capability also distinguishes the B540K from the lower-speed B540D, which is rated around 2000 rpm.

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10. Torque Performance

The motor provides approximately 19.4 N·m continuous stall torque and 48.6 N·m peak torque.

Torque Characteristic	Value
Model	MPL-B540K-SJ74AA
Continuous Stall Torque	19.4 N·m
Peak Torque	48.6 N·m
Peak-to-Continuous Ratio	Approximately 2.5:1
Continuous Torque Capability	High
Acceleration Capability	High
Dynamic Load Capability	High

The continuous torque figure is important for determining the long-term load capability of the axis.

The peak torque figure is especially relevant during acceleration, deceleration, rapid direction changes, and short-duration transient loads.

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11. Rotor Inertia

The B540K motor family has a relatively low rotor inertia for its torque class.

The SJ74AA configuration is listed with rotor inertia of approximately 0.00157 kg·m².

Parameter	Value
Model	MPL-B540K-SJ74AA
Rotor Inertia	Approximately 0.00157 kg·m²
Motor Type	Low-inertia servo
Main Benefit	Rapid acceleration/deceleration
Typical Use	Dynamic servo axes

Low rotor inertia is useful in machinery that repeatedly changes speed.

Examples include:

• Pick-and-place systems
• Indexing mechanisms
• Packaging equipment
• Electronic assembly
• Short-travel linear axes
• Reciprocating mechanisms
• High-speed rotary positioning

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12. Single-Turn Absolute Feedback

One of the defining characteristics of the SJ74AA model is its single-turn high-resolution absolute feedback system.

The specified feedback is based on a 1024-cycle-per-revolution Sin/Cos encoder using Hiperface protocol.

This feedback system provides precise shaft-position information within one revolution.

It is particularly useful when the application requires:

• Accurate angular position
• Servo synchronization
• High-resolution positioning
• Repeatable rotary movement
• Electronic gearing
• Coordinated motion
• Precise machine indexing

Single-turn feedback is different from a multi-turn feedback system because the positional information is referenced within a single motor revolution rather than maintaining a multi-revolution absolute position range.

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13. Feedback Advantages

The high-resolution feedback system contributes directly to the motor’s usefulness in precision automation.

The servo controller can use feedback information to regulate:

• Position
• Speed
• Torque
• Acceleration
• Deceleration
• Following error

This closed-loop operation allows the machine to respond to changing mechanical loads while maintaining the commanded motion profile.

For high-speed machines, feedback accuracy becomes particularly important because even a relatively small position error can become significant when the machine is operating through thousands of cycles.

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14. Keyed Shaft

The MPL-B540K-SJ74AA uses a keyed shaft extension.

A keyed shaft is a conventional mechanical interface that allows the motor to transfer torque through a coupling or transmission component.

Typical connections include:

• Servo couplings
• Gearboxes
• Timing pulleys
• Ball screws
• Rotary tables
• Mechanical transmissions
• Other machine shafts

The keyed design can also be advantageous when replacing an older motor with an existing keyed mechanical interface.

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15. Integral 24 V DC Brake

The SJ74AA configuration includes an integral 24 V DC brake.

This is one of the most important differences between the SJ74AA and the SJ72AA version.

The brake can be particularly useful for applications where the motor must help hold a load when servo power is removed.

Typical applications include:

• Vertical axes
• Lifting mechanisms
• Z-axis positioning
• Gravity-loaded machinery
• Vertical ball screws
• Material-handling lifts
• Machines requiring controlled stopping

The brake should be regarded as a holding mechanism rather than a substitute for normal servo deceleration.

Machine safety requirements should always determine whether an additional mechanical safety brake or locking device is required.

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16. SJ72AA Versus SJ74AA

The SJ72AA and SJ74AA models are closely related.

Feature	MPL-B540K-SJ72AA	MPL-B540K-SJ74AA
Speed	4000 rpm	4000 rpm
Rated Output	5.4 kW	5.4 kW
Continuous Torque	19.4 N·m	19.4 N·m
Peak Torque	48.6 N·m	48.6 N·m
Feedback	Single-turn absolute	Single-turn absolute
Feedback Resolution	1024 Sin/Cos cycles/rev	1024 Sin/Cos cycles/rev
Shaft	Keyed	Keyed
Brake	No	24 V DC
Frame	165 mm	165 mm
Stack	101.6 mm	101.6 mm
Weight	Approximately 15 kg	Approximately 19 kg

The primary practical difference is the integral brake.

If the machine requires a motor-mounted holding brake, the SJ74AA is the appropriate configuration.

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17. Connector Configuration

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

The connector can be rotated through approximately 180°, providing installation flexibility.

This is useful when machine space is limited.

A flexible connector arrangement can help:

• Reduce cable interference
• Improve cable routing
• Keep cables away from moving parts
• Simplify installation
• Reduce unnecessary bending
• Improve machine serviceability

For multi-axis machinery, connector orientation can have a significant effect on overall cable-management requirements.

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18. Mounting Configuration

The motor uses IEC metric mounting with free mounting holes, Type FF.

This configuration is convenient for metric machine construction.

The motor mounting surface should be rigid and accurately aligned.

Poor mechanical alignment can result in:

• Excessive bearing loading
• Coupling wear
• Increased vibration
• Positioning errors
• Increased noise
• Reduced service life

Correct mechanical alignment is therefore just as important as selecting the correct motor rating.

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19. Environmental Characteristics

The available technical specification identifies a maximum operating temperature of approximately 40 °C.

Environmental Parameter	Specification
Model	MPL-B540K-SJ74AA
Maximum Operating Temperature	40 °C
Shaft Seal	No
Industrial Environment	Suitable
Mounting Environment	Machine enclosure / industrial equipment
Cooling	Motor thermal design
Contamination Consideration	Protect from unsuitable fluids and contaminants

Because this configuration does not have a shaft seal, the machine designer should pay particular attention to exposure to coolant, oil, washdown fluid, dust, and other contaminants.

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20. Main Product Advantages

20.1 High-Speed 4000 rpm Operation

The 4000 rpm speed rating makes the motor suitable for high-throughput equipment.

It can support fast mechanical cycles and rapid positioning movements.

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20.2 Strong Continuous Torque

The 19.4 N·m continuous torque rating gives the motor substantial load-handling capability.

This is useful for applications requiring continuous torque rather than only short acceleration peaks.

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20.3 High Peak Torque

The 48.6 N·m peak torque provides a substantial transient torque reserve.

This is useful during acceleration, deceleration, indexing, and rapid load changes.

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20.4 Low Rotor Inertia

The low-inertia design supports fast changes in motor speed.

This is particularly valuable in applications with frequent starts, stops, and reversals.

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20.5 Single-Turn Absolute Feedback

The high-resolution single-turn feedback provides accurate angular-position information.

This is useful for high-speed positioning and synchronized machine operation.

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20.6 Integral 24 V Brake

The integrated brake is a major advantage for applications requiring holding capability.

It can be especially useful for vertical axes and gravity-loaded mechanisms.

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20.7 Keyed Shaft

The keyed shaft provides a familiar industrial mechanical connection.

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20.8 Flexible Connector Orientation

The 180° rotatable right-angle connector helps simplify cable installation.

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20.9 Compact Frame Relative to Torque

The 165 mm frame provides a useful balance between physical size and performance.

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21. Typical Applications

21.1 Packaging Machinery

The MPL-B540K-SJ74AA is well suited to packaging machinery that requires high-speed servo movement.

Typical applications include:

• Product indexing
• Feed mechanisms
• Film transport
• Cutting mechanisms
• Labeling systems
• Carton positioning
• Wrapping machinery
• Rotary packaging systems

The high speed and high peak torque make it useful for rapidly repeated machine cycles.

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22. Material Handling

Material-handling equipment often requires controlled acceleration and deceleration.

The motor can be used for:

• Transfer mechanisms
• Conveyor positioning
• Automated storage systems
• Pick-and-place systems
• Rotary transfer mechanisms
• Lift positioning
• Linear handling systems

The integral brake becomes particularly useful when the machine includes a vertical axis.

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23. Ball-Screw Systems

The motor is well suited to ball-screw-driven linear axes.

Typical applications include:

• Machine slides
• Linear positioning tables
• Automated inspection
• Drilling systems
• Cutting systems
• Assembly stations
• Dispensing equipment
• Precision positioning equipment

The motor’s 4000 rpm capability can provide high linear speed when used with an appropriate ballscrew pitch and transmission arrangement.

The actual screw operating speed must still be checked against the critical speed, screw length, screw diameter, bearing arrangement, lubrication, and mechanical vibration.

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24. Vertical Axis Applications

The integral brake makes the SJ74AA particularly interesting for vertical axes.

Potential applications include:

• Z-axis positioning
• Lift mechanisms
• Vertical ball screws
• Elevators within automated machinery
• Vertical handling systems
• Press mechanisms
• Gravity-loaded positioning systems

The brake can help hold the axis when servo power is removed.

However, the brake should not automatically be treated as the sole safety device. The final machine safety architecture should determine whether an additional mechanical locking or safety-braking system is required.

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25. Machine Tool Applications

The B540K is suitable for selected machine-tool feed and positioning axes.

Potential applications include:

• Feed axes
• Tool positioning
• Rotary positioning
• Workpiece positioning
• Automated fixture movement
• Auxiliary machine axes

The high-speed 4000 rpm capability can be useful for rapid traversing and positioning.

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26. Automated Assembly

Automated assembly systems often require fast and accurate motion.

The motor can be considered for:

• Component insertion
• Part positioning
• Fixture movement
• Press positioning
• Rotary indexing
• Inspection stations
• Pick-and-place systems
• Automated feeding

The high-resolution feedback system supports precise closed-loop motion.

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27. Printing and Converting Machinery

Printing and converting machines often require coordinated high-speed rotary motion.

Potential applications include:

• Feed rollers
• Registration systems
• Cutting mechanisms
• Web-handling axes
• Rotary positioning
• Synchronized rollers

The B540K’s high-speed characteristics make it suitable for many such applications when the mechanical load is properly matched.

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28. Electronic Assembly Equipment

Electronic assembly equipment often requires rapid positioning with short settling times.

The low-inertia design can be advantageous for:

• Component positioning
• Inspection stages
• Precision indexing
• Automated fixtures
• Small linear stages
• Pick-and-place mechanisms

The motor’s feedback system also allows the servo controller to continuously monitor and correct the axis position.

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29. Five Related or Same-Series Models

The following five models are closely related to the MPL-B540K-SJ74AA and are useful alternatives when the machine requires a different brake, shaft, or feedback configuration.

Model	Speed	Output	Continuous Torque	Peak Torque	Feedback	Shaft	Brake	Frame / Stack	Approx. Weight
MPL-B540K-SJ72AA	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	Single-turn absolute	Keyed	None	165 / 101.6 mm	~15 kg
MPL-B540K-SK72AA	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	Single-turn absolute	Keyless	None	165 / 101.6 mm	~15 kg
MPL-B540K-SK74AA	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	Single-turn absolute	Keyless	24 V DC	165 / 101.6 mm	~19–20 kg
MPL-B540K-MJ74AA	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	Multi-turn absolute	Keyed	24 V DC	165 / 101.6 mm	~19 kg
MPL-B540K-MK74AA	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	Multi-turn absolute	Keyless	24 V DC	165 / 101.6 mm	~19 kg

The B540K family includes multiple combinations of single-turn and multi-turn feedback, keyed and keyless shafts, and brake/no-brake configurations.

The exact motor weight can vary according to feedback and brake configuration, so the values in the comparison table should be treated as approximate selection figures rather than shipping weights.

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30. Five Popular Models from the Same Brand

The following five MPL motor families are useful for comparing different speed, torque, and power requirements.

Model	Maximum Speed	Rated Output	Continuous Torque	Peak Torque	Rotor Inertia	Weight	Dimension Reference
MPL-B520K	4000 rpm	3.5 kW	10.7 N·m	23.2 N·m	0.000783 kg·m²	9.8 kg	165 mm frame / shorter stack
MPL-B540D	2000 rpm	3.4 kW	19.4 N·m	41.0 N·m	0.00147 kg·m²	15.0 kg	165 / 101.6 mm
MPL-B540K	4000 rpm	5.4 kW	19.4 N·m	48.6 N·m	~0.00147 kg·m²	~15 kg basic	165 / 101.6 mm
MPL-B560F	3000 rpm	5.5 kW	26.8 N·m	67.8 N·m	0.00213 kg·m²	20.2 kg	165 mm / longer stack
MPL-B580F	3000 rpm	7.1 kW	34.0 N·m	87.0 N·m	0.00289 kg·m²	25.4 kg	Larger frame / longer stack

These values show the progression through the MPL family from smaller, lighter motors toward larger motors with greater continuous and peak torque capability.

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31. MPL-B520K Comparison

The B520K is a smaller and lighter option.

Parameter	MPL-B520K	MPL-B540K-SJ74AA
Maximum Speed	4000 rpm	4000 rpm
Rated Output	3.5 kW	5.4 kW
Continuous Torque	10.7 N·m	19.4 N·m
Peak Torque	23.2 N·m	48.6 N·m
Rotor Inertia	0.000783 kg·m²	~0.00157 kg·m²
Weight	9.8 kg	~19 kg with brake

The B520K is preferable when the machine has a lower torque requirement and weight is a major consideration.

The B540K becomes more attractive when the machine requires significantly greater torque and power.

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32. MPL-B540D Comparison

The B540D provides similar continuous torque but operates at approximately half the maximum speed.

Parameter	MPL-B540D	MPL-B540K-SJ74AA
Maximum Speed	2000 rpm	4000 rpm
Rated Output	3.4 kW	5.4 kW
Continuous Torque	19.4 N·m	19.4 N·m
Peak Torque	41.0 N·m	48.6 N·m
Rotor Inertia	0.00147 kg·m²	~0.00157 kg·m²
Weight	~15 kg	~19 kg with brake

The B540K is the stronger choice for high-speed applications.

The B540D can be more appropriate when the mechanical system operates at a lower speed and does not require 4000 rpm.

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33. MPL-B560F Comparison

The B560F provides greater torque capability.

Parameter	MPL-B540K-SJ74AA	MPL-B560F
Maximum Speed	4000 rpm	3000 rpm
Rated Output	5.4 kW	5.5 kW
Continuous Torque	19.4 N·m	26.8 N·m
Peak Torque	48.6 N·m	67.8 N·m
Rotor Inertia	~0.00157 kg·m²	0.00213 kg·m²
Weight	~19 kg with brake	20.2 kg basic family reference

The B560F should be considered when torque capacity is more important than achieving 4000 rpm.

The B540K is more attractive for high-speed applications requiring a relatively fast response.

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34. MPL-B580F Comparison

The B580F is a higher-torque alternative.

Parameter	MPL-B540K-SJ74AA	MPL-B580F
Maximum Speed	4000 rpm	3000 rpm
Rated Output	5.4 kW	7.1 kW
Continuous Torque	19.4 N·m	34.0 N·m
Peak Torque	48.6 N·m	87.0 N·m
Rotor Inertia	~0.00157 kg·m²	0.00289 kg·m²
Weight	~19 kg with brake	25.4 kg basic family reference

The B580F is suitable for heavier loads where greater continuous and peak torque are required.

The B540K remains preferable where speed, compactness, and dynamic response are more important.

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35. Why Choose MPL-B540K-SJ74AA?

The MPL-B540K-SJ74AA is particularly attractive when a machine needs all of the following characteristics:

• 4000 rpm maximum speed
• 5.4 kW output
• 19.4 N·m continuous torque
• 48.6 N·m peak torque
• Low rotor inertia
• Single-turn absolute feedback
• 1024-cycle Sin/Cos encoder
• Hiperface feedback
• Keyed shaft
• Integral 24 V DC brake
• 165 mm frame
• 101.6 mm magnet stack
• Right-angle connector
• Rotatable connector
• IEC metric mounting
• Approximately 19 kg brake-equipped weight

This combination makes the model particularly useful for demanding servo axes where both high-speed performance and holding-brake capability are required.

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36. Servo Drive Compatibility

The technical specification identifies the B540K family as compatible with several servo-drive families, including the Kinetix 5500, 6200/6500, 6000, 300, 350, 2000, 7000, and Ultra 3000 families.

This allows the motor to be incorporated into a broad range of industrial motion-control systems.

Before commissioning, the exact motor catalog number and servo-drive catalog number should always be checked together.

Important compatibility parameters include:

• Motor voltage
• Motor current
• Feedback interface
• Feedback protocol
• Brake voltage
• Motor thermal characteristics
• Drive firmware
• Motor identification data
• Cable configuration

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37. Mechanical Installation

The motor should be installed on a rigid machine surface with accurate alignment between the motor shaft and driven mechanism.

Incorrect alignment can result in:

• Excessive bearing load
• Coupling wear
• Shaft vibration
• Positioning error
• Increased acoustic noise
• Reduced mechanical life

The keyed shaft should be connected using an appropriate coupling or transmission component designed for the motor’s torque and speed.

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38. Brake Wiring Considerations

The 24 V DC brake is an important part of the SJ74AA configuration.

The brake circuit should be integrated into the machine control architecture according to the applicable motion-control design.

The brake should not be treated as a normal dynamic stopping device.

A typical machine sequence may involve controlled servo deceleration followed by application of the holding brake.

This approach helps avoid unnecessary mechanical stress on the brake assembly.

The exact brake-control timing should be established according to the drive, machine, and safety requirements.

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39. Vertical-Axis Installation

The integral brake makes the SJ74AA especially useful for vertical axes.

However, the designer should still consider:

• Total vertical load
• Gravity torque
• Ball-screw efficiency
• Gear ratio
• Counterbalance
• Brake holding capacity
• Emergency stop behavior
• Servo-off behavior
• Mechanical safety requirements
• Potential uncontrolled descent

The brake is an important feature, but it should not automatically be regarded as the only safety mechanism for a gravity-loaded axis.

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40. Cable Routing

The right-angle connector can be rotated through approximately 180°.

This allows the installer to select a cable direction that best matches the machine structure.

Good cable routing should ensure that:

• Cables do not rub against moving parts.
• Minimum bend radius is respected.
• Cables are not placed under unnecessary tension.
• Connectors are protected from mechanical impact.
• Power and feedback wiring are appropriately managed.
• Moving-axis cables are properly supported.

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41. Maintenance

Regular inspection should cover both the motor and the mechanical transmission.

Recommended checks include:

• Motor mounting bolts
• Shaft coupling
• Shaft key
• Feedback connector
• Power connector
• Brake operation
• Cable condition
• Motor temperature
• Mechanical vibration
• Bearing noise
• Positioning accuracy
• Servo drive alarms
• Mechanical alignment

Because the motor has no shaft seal, exposure to oil, coolant, and other liquids should also be controlled.

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42. Replacement Checklist

When replacing an existing MPL-B540K-SJ74AA, the following parameters should be matched.

Replacement Parameter	Required Specification
Model	MPL-B540K-SJ74AA
Voltage Class	400 V AC
Armature Voltage	460 V
Rated Speed	4000 rpm
Maximum Speed	4000 rpm
Rated Output	5.4 kW
Continuous Torque	19.4 N·m
Peak Torque	48.6 N·m
Feedback	Single-turn absolute
Feedback Resolution	1024 Sin/Cos cycles/rev
Protocol	Hiperface
Shaft	Keyed
Brake	24 V DC
Connector	SpeedTEC DIN
Connector Orientation	Right angle
Connector Rotation	180°
Frame	165 mm
Stack	101.6 mm
Weight	Approximately 19 kg
Mounting	IEC metric
Mounting Holes	Type FF
Shaft Seal	No

The full catalog number should be checked before replacement because B540K motors with similar power and torque ratings can have different feedback, shaft, and brake configurations.

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43. Application Selection Guide

Application	Suitability
High-speed packaging	Excellent
Rotary indexing	Excellent
Ball-screw positioning	Excellent
Vertical positioning	Very good, especially because of the brake
Automated assembly	Excellent
Material handling	Excellent
Machine-tool feed axis	Very good
Printing/converting	Very good
Precision inspection	Very good
Gravity-loaded axis	Very good with correct safety design
Constant-speed pump duty	Generally not the primary application
Simple fan duty	Generally unnecessary for this servo motor

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44. Main Advantages at a Glance

Advantage	Description
High-Speed Performance	Up to 4000 rpm
5.4 kW Output	Suitable for demanding servo applications
19.4 N·m Continuous Torque	Strong continuous load capability
48.6 N·m Peak Torque	High transient acceleration capability
Low Rotor Inertia	Fast dynamic response
Single-Turn Absolute Feedback	Accurate within-one-revolution position information
1024 Sin/Cos Feedback	High-resolution feedback
Hiperface Protocol	Industrial servo feedback interface
Keyed Shaft	Conventional mechanical connection
24 V DC Brake	Useful for holding and vertical-axis applications
165 mm Frame	Compact relative to torque output
101.6 mm Stack	Frame-5 B540K construction
Rotatable Connector	Flexible cable routing
IEC Metric Mounting	Convenient industrial installation

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45. Complete Technical Summary

Category	Specification
Model	MPL-B540K-SJ74AA
Brand	Allen-Bradley
Product Series	MP-Series MPL
Motor Type	Low-Inertia Brushless Rotary Servo Motor
Voltage Class	400 V AC
Armature Voltage	460 V
Frame Size	Frame 5
Frame Dimension	165 mm
Magnet Stack Length	101.6 mm
Rated Speed	4000 rpm
Maximum Speed	4000 rpm
Rated Output	5.4 kW
Continuous Stall Torque	19.4 N·m
Peak Torque	48.6 N·m
Continuous Stall Current	Approximately 20.5 A
Rotor Inertia	Approximately 0.00157 kg·m²
Feedback	Absolute single-turn
Feedback Resolution	1024 Sin/Cos cycles/rev
Feedback Protocol	Hiperface
Shaft	Keyed
Brake	24 V DC integral brake
Shaft Seal	No
Connector	SpeedTEC DIN
Connector Orientation	Right angle
Connector Rotation	180° rotatable
Mounting	IEC metric
Mounting Holes	Free mounting holes, Type FF
Maximum Operating Temperature	40 °C
Approximate Weight	Approximately 19 kg
Primary Application	Industrial servo motion
Main Strength	High-speed precision motion with integral holding brake

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46. Final Product Assessment

The MPL-B540K-SJ74AA is a strong industrial servo motor for applications that require a combination of high speed, substantial torque, precise single-turn feedback, and an integral holding brake.

Its 5.4 kW output, 4000 rpm maximum speed, 19.4 N·m continuous stall torque, and 48.6 N·m peak torque provide a strong performance combination for demanding machine axes.

The 165 mm frame and 101.6 mm magnet stack provide a useful physical balance between motor size and torque capacity.

The single-turn absolute feedback system is an important feature of this specific configuration. The 1024-cycle Sin/Cos encoder and Hiperface interface provide the feedback resolution required for accurate servo positioning and coordinated motion.

The keyed shaft makes the motor convenient for conventional industrial mechanical transmissions, while the 24 V DC integral brake makes the model particularly attractive for vertical axes, lifting mechanisms, and other applications where the motor must provide holding capability after controlled stopping.

The right-angle SpeedTEC DIN connector with approximately 180° rotational flexibility also makes the motor easier to integrate into compact machinery where cable space is limited.

Compared with the MPL-B540K-SJ72AA, the most significant difference is the integral 24 V DC brake. If the machine does not require a holding brake, the SJ72AA can provide a simpler and lighter configuration. If the machine requires motor-mounted holding capability, the SJ74AA is the more appropriate configuration.

Overall, the MPL-B540K-SJ74AA is best suited to high-speed industrial servo applications such as packaging, material handling, automated assembly, ball-screw positioning, machine-tool axes, rotary indexing, printing and converting equipment, and vertical motion systems where a high-performance servo motor with an integral brake is required.