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MPL-B520K-SJ74AA Servo Motor

1. Product Overview

The MPL-B520K-SJ74AA is a high-performance low-inertia AC rotary servo motor designed for industrial motion-control applications that require accurate positioning, fast acceleration and deceleration, stable speed control, and dependable repetitive operation.

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 rated for the 460 V class and has a 4000 rpm maximum speed configuration. It uses a single-turn high-resolution absolute encoder, a keyed shaft extension, a right-angle rotatable SpeedTEC DIN connector, and an integrated 24 V DC holding brake.

Compared with the closely related no-brake MPL-B520K-SJ72AA, the most obvious difference is the brake configuration. The SJ74AA incorporates a 24 V DC holding brake, making it more suitable for applications where the motor or machine axis needs additional holding capability when servo torque is removed.

The motor is intended for closed-loop motion systems rather than simple fixed-speed motor applications. In a typical installation, the motor works together with a compatible servo drive, motion controller, feedback system, mechanical coupling, and machine load.

The low-inertia design is particularly useful for machines that repeatedly accelerate, decelerate, stop, reverse, and reposition. Such applications are common in packaging machinery, assembly equipment, indexing systems, material handling equipment, machine tools, and other automated production machinery.

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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 Design	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	4000 rpm
Feedback	Single-Turn High-Resolution Encoder
Shaft	Keyed Shaft Extension
Brake	24 V DC Holding Brake
Connector	SpeedTEC DIN
Connector Style	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric
Mounting Hole Style	Free Mounting Holes / Type FF
Model	MPL-B520K-SJ74AA

The product belongs to the MPL low-inertia servo motor range. Its configuration is aimed at applications where high-speed operation and dynamic response are important, while the integrated brake adds another level of mechanical holding capability.

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3. Product Identification

The complete model number is:

MPL-B520K-SJ74AA

The individual sections of the model designation identify different characteristics of the motor.

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
J	Keyed shaft extension
7	SpeedTEC DIN right-angle connector
4	24 V DC holding brake
AA	Product configuration designation

This makes the model number useful when comparing closely related motors.

For example, the difference between SJ72AA and SJ74AA is particularly important. Both models share the same basic frame, stack, speed class, single-turn feedback, keyed shaft, and connector arrangement, but the SJ74AA includes a 24 V DC brake, while the SJ72AA is the no-brake version.

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4. Main Technical Parameters

Parameter	Specification
Model	MPL-B520K-SJ74AA
Brand	Allen-Bradley
Product Family	MP-Series
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
Speed Class	4000 rpm
Rated Rotor Speed	Commonly listed as 4000 rpm maximum configuration
Continuous Stall Torque	Approximately 10.7 N·m
Peak Stall Torque	Approximately 23 N·m
Power Class	Approximately 3.5 kW
Feedback	Single-turn high-resolution absolute encoder
Encoder Type	1024 Sin/Cos absolute single-turn encoder
Communication / Feedback Protocol	Hiperface configuration
Shaft	Keyed Shaft Extension
Shaft Seal	None
Brake	24 V DC Holding Brake
Brake Type	Integrated Holding Brake
Connector	SpeedTEC DIN
Connector Orientation	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric
Mounting Holes	Free Mounting Holes / Type FF
Flange	Metric flange mounting
Frame Diameter / Size Class	165 mm
Magnetic Stack	50.8 mm
Approx. Weight	9.07 kg
Approx. Weight in Pounds	20.0 lb
Protection	IP50 class in standard configuration
Overall Installation Dimensions	Must be checked against the mechanical drawing
Shaft Configuration	Keyed
Brake Voltage	24 V DC

The principal factory configuration identifies the motor as a 460 V class, 165 mm-frame, 50.8 mm-stack, 4000 rpm MPL servo motor with single-turn high-resolution feedback, keyed shaft, SpeedTEC DIN right-angle connector, and 24 V DC brake.

Commonly published technical data also lists approximately 10.7 N·m continuous stall torque, approximately 23 N·m peak stall torque, and approximately 3.5 kW power output, although exact performance values should always be matched to the applicable drive and motor data for final engineering selection.

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5. Dimensions and Weight

The motor uses a 165 mm frame size and a 50.8 mm magnetic stack length.

These are the two most important basic dimensional identifiers for this particular B520K configuration.

Mechanical Parameter	Specification
Model	MPL-B520K-SJ74AA
Frame Size	165 mm
Frame Size	6.50 in
Magnetic Stack Length	50.8 mm
Magnetic Stack	2.0 in
Mounting	IEC Metric
Mounting Style	Free Mounting Holes / Type FF
Shaft	Keyed
Shaft Seal	None
Connector	Right-angle SpeedTEC DIN
Connector Rotation	180°
Brake	Integrated 24 V DC holding brake
Approx. Weight	9.07 kg
Approx. Weight	20.0 lb
Complete Overall Dimensions	Refer to mechanical drawing for exact envelope
Installation Clearance	Must account for connector, shaft and cable routing

The commonly published product weight is approximately 9.07 kg, equivalent to about 20.0 lb.

The 165 mm frame and 50.8 mm stack length should not be treated as the complete outside dimensions of the finished motor.

When designing a machine mounting plate, motor guard, cable path, or replacement installation, the shaft projection, flange pattern, connector clearance, motor body length, and cable bend radius should also be considered.

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6. Electrical Characteristics

The MPL-B520K-SJ74AA is designed as a high-voltage industrial servo motor in the 460 V class.

The product is also commonly described as a 480 V AC rotary servo motor.

Electrical Item	Specification
Model	MPL-B520K-SJ74AA
Motor Supply Class	460 V
AC Product Rating	480 V AC
Motor Type	Permanent-Magnet AC Servo
Control	Closed-Loop Servo Control
Feedback	Single-Turn Absolute Encoder
Feedback Resolution	High Resolution
Brake Supply	24 V DC
Brake	Holding Brake
Maximum Speed Class	4000 rpm
Motor Construction	Low Inertia
Rotor Type	Permanent Magnet
Control System	Servo Drive Based

The motor is not intended to be operated as a conventional induction motor with a standard motor starter.

It is designed to operate as part of a servo control system where the drive controls motor current, torque, speed, and position.

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7. Low-Inertia Design

The low-inertia construction is one of the most important features of the MPL-B520K-SJ74AA.

In a servo application, the motor must often change speed very quickly.

A machine may accelerate from a low speed to a high speed, stop, reverse direction, and then return to the original position in a very short period.

The lower the motor’s own rotational inertia, the easier it is for the servo system to change motor speed.

This is particularly useful for high-cycle automation.

For example, a packaging machine may perform several motion cycles per second. Each cycle can involve acceleration, deceleration, positioning, dwell, and reversal.

A low-inertia motor is well suited to this type of operating profile.

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8. 4000 RPM Speed Capability

The 4000 rpm speed class is another important characteristic.

High motor speed can reduce the amount of mechanical reduction required in certain applications.

It can also allow a machine axis to complete its movement more quickly.

For applications where production cycle time is important, this can be a significant advantage.

However, the machine designer should consider the entire mechanical transmission.

The coupling, gearbox, pulley, belt, screw, bearing system, and driven mechanism must all be suitable for the required rotational speed.

The servo motor’s speed rating should therefore never be considered separately from the mechanical system.

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9. Single-Turn High-Resolution Encoder

The MPL-B520K-SJ74AA uses a single-turn high-resolution absolute encoder.

The encoder is an essential part of the servo system.

It provides the control system with information about the actual motor position and motion.

The commonly listed configuration uses a 1024 Sin/Cos absolute single-turn encoder with Hiperface protocol.

This feedback arrangement allows the servo system to compare commanded motion with actual motor movement.

As a result, the system can regulate speed and position much more precisely than a simple open-loop motor arrangement.

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10. Keyed Shaft Extension

The motor is supplied with a keyed shaft extension.

A keyed shaft is a familiar mechanical connection method in industrial machinery.

It allows a suitable coupling, pulley, gear, or other mechanical component to transmit torque through a keyed connection.

Shaft Feature	Specification
Model	MPL-B520K-SJ74AA
Shaft Type	Keyed
Shaft Extension	Keyed Shaft Extension
Shaft Seal	None
Typical Connection	Coupling, pulley, gear or mechanical transmission
Main Benefit	Positive mechanical torque transmission
Replacement Consideration	Existing coupling must match shaft configuration

The keyed shaft is particularly useful when replacing another motor that already uses a keyed mechanical connection.

However, shaft diameter, key dimensions, shaft length, coupling type, and allowable radial and axial loading should all be checked before installation.

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11. Integrated 24 V DC Holding Brake

The most important difference between the SJ74AA and the closely related SJ72AA is the integrated brake.

The MPL-B520K-SJ74AA has a 24 V DC holding brake.

This brake is designed primarily for holding rather than for repeatedly stopping a rotating machine under normal operating conditions.

In a typical servo application, the motor provides the dynamic stopping and positioning function while the brake provides additional holding capability when motor torque is removed.

This distinction is important.

A holding brake should not automatically be treated as a substitute for a machine safety brake or a dynamic stopping device.

The exact brake control sequence should be designed according to the machine’s safety requirements and the servo drive’s control architecture.

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12. Advantages of the Brake Configuration

The integrated brake can be especially useful in applications involving vertical or gravity-loaded axes.

For example, a vertical slide may tend to move downward if motor torque disappears.

In such a situation, a holding brake can provide an additional mechanical means of keeping the axis in position.

The brake can also be useful during machine shutdown, maintenance conditions, or controlled power-down sequences where mechanical holding is required.

This makes the SJ74AA more versatile than an otherwise similar no-brake motor for certain machine designs.

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13. SpeedTEC DIN Right-Angle Connector

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

This configuration can be valuable when machine space is limited.

A straight connector can require considerable clearance behind the motor.

A right-angle connector allows the cable to leave the motor in a more controlled direction.

The 180-degree rotation capability also provides flexibility during machine installation.

This can simplify cable routing and reduce the possibility of cables interfering with guards, brackets, adjacent motors, or moving machine components.

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14. Protection and Environmental Considerations

Published specifications commonly identify the motor with an IP50 standard protection level.

This is an important consideration when choosing the motor for the installation environment.

The motor should not simply be selected based on torque and speed.

The surrounding environment may contain dust, oil, coolant, moisture, vibration, heat, or other contaminants.

Where the machine operates in a harsh environment, appropriate shaft sealing, cable protection, enclosure design, and installation orientation should be considered.

The motor’s standard protection level should therefore be matched to the actual machine environment.

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15. Typical Applications

The MPL-B520K-SJ74AA is suitable for a wide range of industrial automation applications.

Its combination of low inertia, high speed, high-resolution feedback, keyed shaft, and holding brake makes it particularly useful for demanding motion-control systems.

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15.1 Packaging Machinery

Packaging equipment is one of the most suitable applications for a high-speed low-inertia servo motor.

Machines such as filling equipment, labeling machines, wrapping systems, sealing machines, cartoners, and indexing equipment often require fast repetitive motion.

The motor can accelerate rapidly, move to a defined position, stop, and repeat the same cycle.

The brake option can also be useful where a machine axis needs to remain mechanically held during a stop or power-down condition.

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15.2 Automated Assembly Equipment

Automated assembly machines often have several servo axes operating simultaneously.

One axis may move a component into position while another axis performs insertion, fastening, pressing, or inspection.

High-resolution feedback allows the servo system to coordinate these movements.

The low-inertia design is useful when the machine must perform these actions quickly.

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15.3 CNC and Machine Tools

The motor can also be used in suitable CNC-related motion applications.

A servo motor in a machine tool must provide controlled acceleration, deceleration, positioning, and speed regulation.

The 4000 rpm capability can be advantageous for high-speed positioning axes.

The exact suitability depends on the machine’s required torque, axis inertia, screw pitch, cutting force, reduction ratio, and servo tuning requirements.

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15.4 Vertical Motion Systems

The integrated holding brake makes this model particularly interesting for vertical-axis applications.

Examples include:

• Vertical slides
• Lifting mechanisms
• Automated handling axes
• Z-axis positioning systems
• Vertical assembly mechanisms
• Machine-tool vertical axes

In such applications, the brake can provide holding capability when servo torque is not being applied.

The complete machine safety system should still be designed independently of the motor brake.

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15.5 Material Handling Equipment

Servo-controlled material handling equipment can benefit from accurate position control.

Examples include:

• Transfer mechanisms
• Indexing conveyors
• Automated positioning systems
• Pick-and-place equipment
• Sorting mechanisms
• Transfer tables

The motor’s high-speed capability allows fast movement, while the feedback system provides closed-loop position information.

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15.6 Robotics and Pick-and-Place Systems

Pick-and-place machines require repeated acceleration and deceleration.

A low-inertia motor can help reduce the time required to complete each movement.

The holding brake can also be useful on axes where position must be maintained during a power-off condition.

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15.7 Printing and Converting Machinery

Printing, cutting, slitting, winding, and converting machinery often require accurate speed and position control.

Servo motors can be used to synchronize different mechanical sections of the machine.

The high-speed capability of the MPL-B520K-SJ74AA can be beneficial where rapid response and repeated positioning are required.

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16. Main Product Advantages

Advantage	Description
Low-Inertia Design	Provides fast dynamic response
4000 rpm Speed Class	Suitable for high-speed machinery
Single-Turn High-Resolution Encoder	Provides precise feedback
Keyed Shaft	Convenient for conventional mechanical transmission
24 V DC Holding Brake	Provides additional mechanical holding capability
Right-Angle Connector	Helps with compact machine installation
180° Connector Rotation	Gives greater cable-routing flexibility
165 mm Frame	Suitable for substantial industrial motion applications
50.8 mm Stack	Compact stack configuration within the 165 mm frame
IEC Metric Mounting	Suitable for metric machine construction
Approx. 9.07 kg Weight	Practical for industrial machine mounting
Absolute Single-Turn Feedback	Supports closed-loop positioning
High-Speed Response	Well suited to repetitive machine cycles

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17. Advantage of the Holding Brake

The integrated brake is one of the strongest reasons to select the SJ74AA instead of a no-brake version.

When a machine axis needs to remain stationary after servo torque is removed, the brake can provide additional holding capability.

This can be valuable for vertical axes and mechanisms that are influenced by gravity.

It can also help simplify the machine’s mechanical design because a separate external motor brake may not be required.

However, the brake should be treated as a holding device and not automatically as the primary safety stopping mechanism.

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18. Advantage of the Keyed Shaft

The keyed shaft is particularly useful in conventional industrial machine construction.

Many couplings, pulleys, and mechanical transmission components are designed around keyed shafts.

This can make the motor easier to integrate into existing equipment.

For replacement applications, this can be a significant advantage because the mechanical interface may already be designed around a keyed motor shaft.

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19. Advantage of High-Resolution Feedback

High-resolution feedback gives the servo controller detailed information about actual motor movement.

This is particularly important in precision machinery.

The controller can continuously evaluate motor position and adjust the drive output accordingly.

The result is controlled motion rather than simply applying a fixed amount of electrical power to the motor.

This is one of the fundamental characteristics that distinguishes a servo motor from many conventional motor types.

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20. Advantage of Low Rotor Inertia

Low rotor inertia becomes especially valuable during rapid reversals.

Imagine a machine moving forward at high speed and then immediately reversing.

The servo drive must first decelerate the rotating system before accelerating it in the opposite direction.

Lower motor inertia makes this process easier.

This can reduce the amount of torque required simply to change the motor’s own speed and can leave more available torque for the machine load.

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21. Five Related Models in the Same or Closely Related Series

The following models are useful for comparison when selecting an MPL motor around the same general performance range.

Model	Series	Frame	Stack	Speed Class	Feedback	Shaft	Brake	Typical Configuration
MPL-B520K-SJ72AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyed	No	Similar motor without brake
MPL-B520K-SJ74AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyed	24 V DC	Reference model
MPL-B520K-SK72AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyless	No	Similar no-brake/keyless version
MPL-B520K-SK74AA	MPL Low-Inertia	165 mm	50.8 mm	4000 rpm	Single-turn	Keyless	24 V DC	Brake/keyless configuration
MPL-B540K-SJ74AA	MPL Low-Inertia	165 mm	101.6 mm	4000 rpm	Single-turn	Keyed	24 V DC	Longer-stack, higher-output configuration

The B520K models share the same basic 165 mm frame and 50.8 mm magnetic stack.

The main differences are feedback configuration, shaft arrangement, and brake selection.

The B540K models use a longer 101.6 mm magnetic stack, making them a useful alternative when a higher motor-output class is required while retaining the general 165 mm frame family.

The related model descriptions identify the B520K SJ/SK configurations as 165 mm-frame, 50.8 mm-stack, 4000 rpm single-turn models, while the B540K family uses a 101.6 mm stack and remains in the 4000 rpm single-turn configuration.

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22. Five Popular Models for Broader Brand Comparison

Model	Product Family	Frame / Size Class	Stack	Speed	Feedback	Shaft	Brake	Typical Application
MPL-B520K-SJ74AA	MP-Series MPL	165 mm	50.8 mm	4000 rpm	Single-turn	Keyed	24 V DC	High-speed precision motion
MPL-B520K-MJ74AA	MP-Series MPL	165 mm	50.8 mm	4000 rpm	Multi-turn	Keyed	24 V DC	Absolute multi-turn motion
MPL-B540K-MJ74AA	MP-Series MPL	165 mm	101.6 mm	4000 rpm	Multi-turn	Keyed	24 V DC	Higher-output motion systems
MPL-B540K-SJ74AA	MP-Series MPL	165 mm	101.6 mm	4000 rpm	Single-turn	Keyed	24 V DC	Higher-output single-turn axes
MPL-B560F-MJ74AA	MP-Series MPL	165 mm	152.4 mm	3000 rpm	Multi-turn	Keyed	24 V DC	Higher-torque industrial axes

The B520K models are more speed-oriented.

The B540K models use a longer magnetic stack and are more suitable when the application requires greater motor output.

The B560F configuration moves toward a longer-stack, lower-speed motor arrangement and is useful for applications where torque capability is more important than maximum motor speed.

The broader MPL family includes B540K and B560F configurations with different stack lengths and speed classes, allowing the motor to be selected according to the required combination of torque, speed, feedback, and mechanical configuration.

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23. Detailed Comparison: SJ74AA vs. SJ72AA

Parameter	MPL-B520K-SJ74AA	MPL-B520K-SJ72AA
Frame	165 mm	165 mm
Stack	50.8 mm	50.8 mm
Speed	4000 rpm class	4000 rpm class
Feedback	Single-turn high-resolution	Single-turn high-resolution
Shaft	Keyed	Keyed
Connector	Right-angle SpeedTEC DIN	Right-angle SpeedTEC DIN
Connector Rotation	180°	180°
Brake	24 V DC holding brake	No brake
Approx. Weight	9.07 kg	Approx. 9.98 kg commonly listed
Best Feature	Holding capability	Simpler no-brake configuration
Typical Selection	Vertical/holding axes	Horizontal/high-speed axes

The two models are extremely similar mechanically.

The principal functional difference is the brake.

This makes the SJ74AA the more appropriate choice when the machine requires a holding brake.

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24. Detailed Comparison: Keyed vs. Keyless

Feature	Keyed Configuration	Keyless Configuration
Mechanical Interface	Shaft key	Clamping/friction connection
Conventional Couplings	Excellent compatibility	Depends on coupling
Replacement Use	Very convenient when existing motor is keyed	Better where keyless coupling is already installed
Torque Transmission	Positive keyed connection	Friction/clamping transmission
Installation	Familiar	Requires appropriate clamping component
Maintenance	Straightforward	Depends on coupling design
Main Advantage	Conventional industrial interface	Flexible precision coupling

The SJ74AA is the keyed version.

This is particularly useful when the motor is replacing an existing keyed-shaft servo motor.

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25. Detailed Comparison: Brake vs. No Brake

Feature	Brake Version	No-Brake Version
Motor Brake	Yes	No
Brake Voltage	24 V DC	Not applicable
Holding Function	Yes	No integrated holding brake
Vertical Axis	More suitable	Requires separate holding solution
Horizontal Axis	Suitable	Often sufficient
Motor Complexity	Higher	Simpler
Main Benefit	Holding capability	Simpler configuration
Typical Selection	Gravity-loaded or holding axes	Standard high-speed motion

The brake version should be selected when the machine’s operating conditions justify a holding function.

If the machine does not require a brake, the no-brake version may provide a simpler solution.

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26. Application in Vertical Axes

Vertical machine axes are one of the strongest application cases for the SJ74AA.

Consider a vertical slide carrying a significant load.

When the servo drive is actively producing torque, the motor can control the axis normally.

When the machine enters a stopped or powered-down condition, however, gravity can cause the axis to move.

The integrated holding brake can provide additional mechanical holding capability.

This is why brake-equipped servo motors are commonly considered for vertical axes.

The final machine safety design should still include appropriate safety devices and procedures rather than depending solely on the motor brake.

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27. Application in High-Speed Indexing

High-speed indexing machines repeatedly move between predetermined positions.

A typical cycle might be:

1. Accelerate rapidly.
2. Move to the target position.
3. Decelerate.
4. Stop.
5. Perform the machine operation.
6. Accelerate again.
7. Move to the next position.

The low-inertia design and high-speed capability of the MPL-B520K-SJ74AA are well suited to this type of motion.

The brake is not necessarily used during every cycle.

Instead, it can provide holding capability when the machine enters an appropriate stopped or power-off condition.

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28. Application in Automated Pressing and Assembly

Automated pressing and assembly equipment often requires accurate movement toward a component.

The servo motor can control approach speed, position, and stopping.

High-resolution feedback helps the control system monitor actual motor movement.

The brake can provide additional holding capability when required by the machine’s mechanical design.

For force-sensitive applications, however, motor torque alone should not be assumed to be equivalent to a dedicated force-control system.

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29. Application in Material Transfer Systems

Material transfer equipment often needs to move loads quickly but stop them accurately.

The motor can drive a transfer axis, rotary indexing table, conveyor, or positioning mechanism.

The high-speed capability is useful for reducing cycle time.

The encoder provides feedback for accurate movement.

The brake provides an additional option for holding the mechanism during machine stoppage.

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30. Application in Automated Inspection Machines

Inspection equipment often requires a component to be positioned accurately before a camera, sensor, measuring device, or testing mechanism performs its operation.

The servo motor can move the workpiece or inspection mechanism into position.

After reaching the target position, the servo system can maintain the commanded position.

For mechanisms that must remain mechanically held during certain conditions, the brake configuration can provide an additional advantage.

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31. Advantages for Machine Builders

From a machine-builder perspective, the MPL-B520K-SJ74AA offers several practical advantages.

The 165 mm frame gives the motor a substantial industrial mounting platform.

The 50.8 mm stack keeps the motor in a relatively short-stack configuration.

The 4000 rpm speed capability supports high-cycle machinery.

The keyed shaft simplifies conventional mechanical transmission.

The right-angle connector helps with cable routing.

The 24 V DC brake provides an additional holding option.

Together, these features make the motor a flexible choice for industrial automation machinery.

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32. Advantages for Replacement Applications

Replacement work requires more than matching a motor’s nominal voltage.

The replacement motor should also match:

• Frame size
• Mounting pattern
• Shaft type
• Shaft dimensions
• Feedback configuration
• Connector arrangement
• Brake configuration
• Speed
• Torque
• Motor inertia
• Cable arrangement
• Environmental requirements

The MPL-B520K-SJ74AA can be particularly attractive as a replacement when the existing motor requires a 165 mm frame, 50.8 mm stack, keyed shaft, single-turn feedback, and 24 V DC holding brake.

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33. Weight and Mechanical Integration

The approximate motor weight is 9.07 kg.

For a fixed machine axis, this is primarily a structural mounting consideration.

For a moving axis, however, motor weight becomes part of the moving mass.

This can affect acceleration requirements.

For example, if the motor is mounted directly on a moving carriage, the servo system must accelerate the motor mass together with the carriage and workpiece.

Therefore, machine designers should consider motor location carefully.

In some machine architectures, mounting the motor on the stationary frame and transferring motion through a mechanical transmission can reduce moving mass.

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34. Important Engineering Selection Factors

Before ordering or installing the MPL-B520K-SJ74AA, the following factors should be checked.

34.1 Voltage Compatibility

The servo drive must be suitable for the motor’s 460 V class.

34.2 Speed Requirement

The machine’s maximum required speed should remain within the motor’s applicable speed range.

34.3 Continuous Torque

The continuous load torque should be compared with the motor’s continuous torque capability.

34.4 Peak Torque

Acceleration, deceleration, and short-duration overload requirements should be evaluated against peak torque capability.

34.5 Load Inertia

The reflected mechanical load inertia should be considered when determining servo performance.

34.6 Feedback Compatibility

The drive and controller must support the motor’s single-turn high-resolution feedback arrangement.

34.7 Brake Compatibility

The machine control system must properly control the 24 V DC holding brake.

34.8 Shaft Compatibility

The machine coupling must match the keyed shaft.

34.9 Mounting Compatibility

The 165 mm frame and mounting-hole arrangement must match the machine.

34.10 Environmental Conditions

Temperature, humidity, dust, oil, coolant, vibration, and contamination should be considered.

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35. Recommended Model Selection

Application Requirement	Recommended Model
165 mm frame + 50.8 mm stack + keyed shaft + brake	MPL-B520K-SJ74AA
Same basic motor without brake	MPL-B520K-SJ72AA
165 mm frame + 50.8 mm stack + keyless shaft + brake	MPL-B520K-SK74AA
Same general B520K configuration without brake/keyless	MPL-B520K-SK72AA
Longer stack and higher output requirement	MPL-B540K-SJ74AA
Multi-turn feedback requirement	MPL-B520K-MJ74AA / related M-series
Higher torque requirement	MPL-B540K or larger frame/stack models
Lower speed but higher torque-oriented configuration	MPL-B560F family

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36. Product Specification Summary

Category	Specification
Model	MPL-B520K-SJ74AA
Brand	Allen-Bradley
Family	MP-Series
Series	MPL Low-Inertia Brushless Servo Motors
Motor 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
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 absolute encoder
Feedback Resolution	1024 Sin/Cos configuration
Feedback Protocol	Hiperface
Shaft	Keyed
Shaft Seal	None
Brake	24 V DC holding brake
Connector	SpeedTEC DIN
Connector Type	Right Angle
Connector Rotation	180°
Mounting	IEC Metric
Mounting Hole Type	Free Mounting Holes / Type FF
Frame Dimension	165 mm
Stack Dimension	50.8 mm
Approx. Weight	9.07 kg
Approx. Weight	20.0 lb
Protection	IP50 standard class
Primary Application	Industrial servo motion
Main Characteristics	Low inertia, high speed, high-resolution feedback, keyed shaft, holding brake

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37. Final Product Assessment

The MPL-B520K-SJ74AA is a strong choice for industrial machinery that requires fast servo response while also benefiting from an integrated holding brake.

Its 165 mm frame, 50.8 mm magnetic stack, 4000 rpm speed class, single-turn high-resolution absolute encoder, keyed shaft, right-angle rotatable connector, and 24 V DC holding brake give the motor a well-balanced configuration for demanding automation equipment.

The low-inertia design makes it particularly suitable for machines that perform frequent acceleration and deceleration.

The high-speed capability makes it attractive for high-cycle production equipment.

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

The keyed shaft provides a conventional mechanical connection.

The right-angle connector provides flexibility when cable space is limited.

Most importantly, the integrated 24 V DC holding brake gives this model an advantage in applications where the machine must maintain position when motor torque is removed.

For horizontal-axis applications where a brake is not required, a no-brake model from the same family may be simpler.

For vertical-axis or gravity-loaded applications, the SJ74AA becomes particularly attractive because the brake provides additional holding capability.

The motor’s approximately 9.07 kg weight should also be included in machine structural and moving-mass calculations.

Overall, the MPL-B520K-SJ74AA is best suited to high-speed industrial motion systems where rapid response, accurate feedback, conventional keyed mechanical integration, and motor holding capability are all important.

It is a particularly practical configuration for packaging machinery, automated assembly equipment, indexing systems, material-handling machinery, vertical positioning axes, CNC-related motion systems, and other automated production equipment requiring dependable servo control.