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Allen-Bradley MPL-B420P-RJ72AA Low-Inertia Servo Motor

1. Product Overview

The Allen-Bradley MPL-B420P-RJ72AA is a high-performance MP-Series MPL low-inertia brushless AC servo motor designed for precision motion-control applications that require high rotational speed, stable torque performance, accurate feedback, and reliable mechanical operation.

This model belongs to the 115 mm frame-size MPL family and uses a 50.8 mm magnet stack. It is designed for operation in the 460 V AC class and provides a rated speed of 5000 rpm. The motor uses a resolver feedback system, making it suitable for motion-control applications where dependable position and speed feedback are required.

The MPL-B420P-RJ72AA uses a keyed shaft configuration and does not include an integral holding brake. Its right-angle SpeedTEC DIN connector can be rotated through 180 degrees, providing additional flexibility when the motor is installed in machinery with limited cable-routing space.

The combination of a low-inertia rotor, 5000 rpm operating capability, 4.74 Nm continuous torque, and 13.5 Nm peak torque makes this motor suitable for a wide range of industrial automation systems, including machine tools, packaging equipment, material handling machinery, converting equipment, assembly machines, and other servo-driven production equipment.

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2. Brand and Product Series

Item	Details
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Servo Motors
Motor Type	Brushless AC Servo Motor
Product Category	Rotary Servo Motor
Model	MPL-B420P-RJ72AA
Voltage Class	460 V AC class
Frame Size	115 mm
Magnet Stack Length	50.8 mm
Feedback Type	Resolver
Shaft Type	Keyed shaft
Brake	No integral brake
Maximum/Rated Speed	5000 rpm
Mounting	Metric flange mounting
Connector	SpeedTEC DIN right-angle connector
Connector Rotation	180° rotatable
Mounting Hole Type	Free mounting holes / Type FF

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3. Detailed Technical Specifications

Parameter	MPL-B420P-RJ72AA Specification
Model	MPL-B420P-RJ72AA
Motor Type	Low-inertia brushless AC servo motor
Series	MP-Series MPL
Voltage Class	460 V AC
Rated Speed	5000 rpm
Maximum Speed	5000 rpm
Continuous Stall Torque	4.74 Nm
Peak Stall Torque	13.5 Nm
Continuous Rated Power	1.9 kW
Rotor Inertia	Approximately 0.00026 kg·m²
Frame Size	115 mm
Magnet Stack Length	50.8 mm
Feedback	Resolver
Feedback Category	Resolver-based position/speed feedback
Shaft	Keyed shaft extension
Shaft Seal	No shaft seal
Brake	No integral brake
Connector	SpeedTEC DIN connector
Connector Orientation	Right-angle
Connector Rotation	180° rotatable
Mounting	IEC metric flange mounting
Mounting Holes	Free mounting holes, Type FF
Motor Construction	Low-inertia servo motor
Typical Operating Temperature Limit	Up to approximately 40 °C
Approximate Overall Dimensions	133 × 187 × 98 mm
Approximate Weight	5.44 kg
Application Class	Industrial motion control
Compatible Drive Family	Kinetix and other compatible servo drive systems
Primary Application	Precision rotary motion control

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4. Dimensions and Weight

Dimensions are particularly important when replacing an existing servo motor because the mechanical envelope, mounting flange, shaft position, connector location, and cable-routing space all need to be considered.

For the MPL-B420P-RJ72AA, the 115 mm frame and 50.8 mm magnet stack place the motor in a medium-size industrial servo class. A practical overall envelope is approximately 133 × 187 × 98 mm, with an approximate motor weight of 5.44 kg.

Mechanical Parameter	Value
Frame Size	115 mm
Magnet Stack	50.8 mm
Approx. Overall Width	98 mm
Approx. Overall Height	133 mm
Approx. Overall Length	187 mm
Approx. Weight	5.44 kg
Shaft Configuration	Keyed
Mounting Style	Metric flange
Connector Style	Right-angle SpeedTEC DIN
Brake	None

The dimensions above should be treated as an approximate installation envelope rather than a substitute for the exact mechanical drawing. For machine redesign, replacement, or tight-clearance installation, the exact motor drawing should always be checked against the required mounting dimensions.

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5. Torque and Power Characteristics

The MPL-B420P-RJ72AA is positioned in the 1.9 kW class of the MPL low-inertia servo family.

Its continuous stall torque is approximately 4.74 Nm, while peak stall torque reaches approximately 13.5 Nm. This provides a useful combination of continuous operating capability and short-duration overload performance.

Performance Parameter	Value
Rated Speed	5000 rpm
Maximum Speed	5000 rpm
Continuous Torque	4.74 Nm
Peak Torque	13.5 Nm
Continuous Power	1.9 kW
Rotor Inertia	0.00026 kg·m²

The relatively low rotor inertia is particularly useful for applications involving frequent acceleration and deceleration. Lower motor inertia allows the servo system to change speed rapidly, which can improve cycle time and dynamic response when the drive, mechanical load, and control parameters are correctly matched.

The 13.5 Nm peak torque capability also provides additional short-duration torque capacity during acceleration, deceleration, positioning, and transient load conditions.

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6. Resolver Feedback System

One of the most important features of the MPL-B420P-RJ72AA is its resolver feedback configuration.

Unlike encoder-based versions of the MPL family, this model uses a resolver as its feedback device. Resolver feedback is well suited to industrial environments where robustness and dependable motor-position feedback are important considerations.

The resolver continuously provides feedback information to the servo drive so that the control system can regulate motor position, velocity, and torque.

This makes the motor suitable for applications where accurate closed-loop control is required but a resolver-based feedback architecture is preferred.

Typical applications include:

• Industrial machinery
• Machine tools
• Material handling equipment
• Packaging machinery
• Printing equipment
• Assembly systems
• Production machinery
• Automated positioning equipment
• Rotary indexing equipment
• Motion-control systems

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7. Keyed Shaft Configuration

The MPL-B420P-RJ72AA uses a keyed shaft extension.

A keyed shaft provides a mechanical interface in which the shaft key and matching coupling or hub transmit rotational torque between the servo motor and the driven mechanism.

This configuration is commonly used in industrial machinery where a conventional keyed coupling arrangement is preferred.

The keyed shaft can be advantageous in applications involving:

• Gearboxes
• Couplings
• Timing mechanisms
• Roll drives
• Conveyor systems
• Rotary tables
• Mechanical transmission assemblies
• Industrial machine axes

Proper shaft alignment remains important. Excessive radial or axial loading can negatively affect bearing life and motor performance, so the driven equipment should be aligned correctly during installation.

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8. No Integral Brake

The MPL-B420P-RJ72AA does not include an integral motor brake.

This configuration is appropriate for applications where the mechanical load does not need to be held by a motor-mounted holding brake when servo power is removed.

A no-brake configuration can be useful for:

• Horizontal machine axes
• Conveyor mechanisms
• Rotary mechanisms with independent mechanical holding devices
• Applications where gravity loading is not a concern
• Systems where external braking or mechanical locking is provided

If the servo axis is vertically mounted or carries a suspended load, the absence of an integral brake needs to be considered carefully. In such applications, a brake-equipped version of the same motor family may be more appropriate, depending on the machine design and safety requirements.

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9. SpeedTEC DIN Connector

The motor is equipped with a right-angle SpeedTEC DIN connector.

The connector design is particularly useful when installation space around the motor is limited. The connector can be rotated through approximately 180 degrees, allowing the cable exit direction to be adjusted to suit the machine layout.

This can simplify:

• Servo cable routing
• Cabinet-to-machine wiring
• Cable bend management
• Machine enclosure design
• Motor replacement
• Maintenance access
• Compact machine construction

The connector arrangement is especially useful when multiple servo motors are mounted close to one another or when the available cable-routing space is restricted.

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10. Product Introduction

The Allen-Bradley MPL-B420P-RJ72AA is designed as a precision industrial servo motor for applications requiring fast, repeatable, closed-loop rotary motion.

Its low-inertia construction allows the motor to respond quickly to command changes. When paired with an appropriate servo drive and properly tuned control system, the motor can provide precise acceleration, deceleration, speed regulation, and positioning.

The 5000 rpm speed rating provides a wide operating range for machinery requiring fast rotary movement.

At the same time, the 4.74 Nm continuous torque rating gives the motor sufficient continuous torque capacity for many medium-duty machine axes.

The 13.5 Nm peak torque rating allows the motor to accommodate short-term acceleration and transient load requirements.

The resolver feedback configuration provides a robust feedback solution for industrial environments where reliable closed-loop control is required.

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11. Main Product Advantages

11.1 High-Speed Operation

The 5000 rpm rated speed makes the motor suitable for high-cycle machinery and applications where rapid rotary movement is important.

High rotational speed can help reduce machine cycle time when the mechanical system is designed to take advantage of the available motor speed.

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11.2 Low-Inertia Rotor

The low-inertia rotor design helps the motor accelerate and decelerate quickly.

This is particularly valuable in machines that repeatedly move between different positions rather than operating at one constant speed.

Typical examples include indexing mechanisms, pick-and-place equipment, packaging machines, electronic assembly equipment, and automated production machinery.

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11.3 Strong Peak Torque Capability

The motor provides approximately 4.74 Nm of continuous torque and up to 13.5 Nm of peak torque.

This torque range allows the motor to handle short acceleration demands without requiring the motor to operate continuously at peak output.

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11.4 Resolver Feedback

The resolver provides closed-loop feedback for servo control.

Resolver-based systems are widely used in industrial machinery where reliable feedback performance is important.

The feedback system allows the servo drive to monitor motor operation and adjust the motor command accordingly.

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11.5 Flexible Connector Orientation

The 180-degree rotatable right-angle connector gives machine designers more flexibility when positioning the motor.

This can be particularly useful in compact machines where a straight connector could interfere with guarding, cable tracks, neighboring motors, or structural components.

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11.6 Keyed Shaft

The keyed shaft provides a conventional mechanical connection for many industrial coupling and transmission systems.

It is a familiar shaft configuration for machine builders and maintenance personnel and can simplify compatibility with existing mechanical components.

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11.7 Compact Industrial Design

The 115 mm frame size provides a relatively compact motor package for its performance class.

This makes the motor suitable for machinery where available installation space is limited but a high-speed servo axis is still required.

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12. Typical Applications

Packaging Machinery

The MPL-B420P-RJ72AA can be used for servo-controlled packaging mechanisms requiring accurate speed and positioning.

Typical applications include:

• Feeding systems
• Indexing mechanisms
• Cutting systems
• Sealing mechanisms
• Product positioning
• Conveyor synchronization

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Material Handling

Servo motors are frequently used in automated material-handling systems where speed and position need to be controlled precisely.

Possible applications include:

• Conveyor drives
• Transfer systems
• Rotary positioning
• Sorting equipment
• Automated handling mechanisms

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Machine Tools

The motor’s high-speed capability and closed-loop feedback make it suitable for certain machine-tool motion axes.

Potential uses include:

• Auxiliary machine axes
• Rotary mechanisms
• Feed systems
• Positioning mechanisms
• Automated tooling systems

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Assembly Machinery

The motor can be used in automated assembly equipment where repeatable positioning and controlled movement are required.

Typical functions include:

• Indexing
• Component positioning
• Rotary assembly
• Feeding
• Tool positioning
• Automated adjustment

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Printing and Converting Equipment

High-speed servo motors are often required in printing, winding, feeding, and converting machinery.

The MPL-B420P-RJ72AA can be applied to motion axes where accurate speed regulation and fast dynamic response are needed.

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General Industrial Automation

The motor is also suitable for many general-purpose industrial servo applications where the machine requires:

• Controlled acceleration
• Controlled deceleration
• Precise positioning
• Speed regulation
• Repeatable rotary motion
• Closed-loop operation

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13. Recommended Same-Series or Closely Related Models

The following models are useful alternatives or comparison models when selecting an MPL servo motor. They cover different feedback, shaft, and brake configurations within the same general motor family.

Model	Feedback	Shaft	Brake	Speed	Continuous Torque	Peak Torque	Power	Frame / Stack	Approx. Weight
MPL-B420P-RJ72AA	Resolver	Keyed	No	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 / 50.8 mm	5.44 kg
MPL-B420P-RJ74AA	Resolver	Keyed	24 V DC	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 / 50.8 mm	Approx. 5.8 kg
MPL-B420P-RK72AA	Resolver	Keyless	No	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 / 50.8 mm	Approx. 5.4 kg
MPL-B420P-MJ72AA	Multi-turn absolute	Keyed	No	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 / 50.8 mm	Approx. 5.4 kg
MPL-B420P-MJ74AA	Multi-turn absolute	Keyed	24 V DC	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 / 50.8 mm	Approx. 5.8 kg

Model Selection Notes

The MPL-B420P-RJ74AA is a natural alternative when the same basic resolver configuration is required but an integral 24 V DC holding brake is needed.

The MPL-B420P-RK72AA retains resolver feedback but changes the shaft from keyed to keyless.

The MPL-B420P-MJ72AA changes the feedback architecture from resolver to multi-turn high-resolution absolute feedback while retaining the keyed shaft and no-brake configuration.

The MPL-B420P-MJ74AA combines multi-turn absolute feedback, a keyed shaft, and an integral 24 V DC brake.

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14. Five More Popular Related Models

Model	Main Configuration	Feedback	Shaft	Brake	Speed	Continuous Torque	Peak Torque	Power	Dimensions / Frame	Approx. Weight
MPL-B310P-MJ74AA	Low-inertia servo	Multi-turn absolute	Keyed	24 V DC	5000 rpm	1.58 Nm	3.61 Nm	0.77 kW	100 mm frame / 25.4 mm stack	Approx. 2.7 kg
MPL-B320P-MK74AA	Low-inertia servo	Multi-turn absolute	Keyless	24 V DC	5000 rpm	3.05 Nm	7.91 Nm	1.5 kW	100 mm frame / 50.8 mm stack	Approx. 3.7 kg
MPL-B330P-MK74AA	Low-inertia servo	Multi-turn absolute	Keyless	24 V DC	5000 rpm	4.18 Nm	11.1 Nm	1.8 kW	100 mm frame / 76.2 mm stack	Approx. 4.6 kg
MPL-B430P-MK74AA	Low-inertia servo	Multi-turn absolute	Keyless	24 V DC	5000 rpm	6.55 Nm	19.8 Nm	2.2 kW	115 mm frame / 76.2 mm stack	Approx. 5.5 kg
MPL-B420P-SK72AA	Low-inertia servo	Single-turn high-resolution	Keyless	No	5000 rpm	4.74 Nm	13.5 Nm	1.9 kW	115 mm frame / 50.8 mm stack	Approx. 5.4 kg

These models are useful when the application requires a different motor size, torque range, feedback method, shaft configuration, or brake arrangement.

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15. Detailed Comparison of the B420P Family

Model	Feedback	Shaft	Brake	Main Difference
MPL-B420P-RJ72AA	Resolver	Keyed	No	Resolver + keyed shaft + no brake
MPL-B420P-RJ74AA	Resolver	Keyed	Yes	Resolver + keyed shaft + brake
MPL-B420P-RK72AA	Resolver	Keyless	No	Resolver + keyless shaft + no brake
MPL-B420P-RK74AA	Resolver	Keyless	Yes	Resolver + keyless shaft + brake
MPL-B420P-MJ72AA	Multi-turn absolute	Keyed	No	Absolute feedback + keyed shaft
MPL-B420P-MJ74AA	Multi-turn absolute	Keyed	Yes	Absolute feedback + keyed shaft + brake
MPL-B420P-MK72AA	Multi-turn absolute	Keyless	No	Absolute feedback + keyless shaft
MPL-B420P-MK74AA	Multi-turn absolute	Keyless	Yes	Absolute feedback + keyless shaft + brake
MPL-B420P-SJ72AA	Single-turn high-resolution	Keyed	No	Single-turn encoder + keyed shaft
MPL-B420P-SK72AA	Single-turn high-resolution	Keyless	No	Single-turn encoder + keyless shaft

This comparison shows why the final characters of an MPL model number are important. Small changes in the model code can indicate major differences in feedback technology, shaft configuration, or brake availability.

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16. Model Number Interpretation

The model number MPL-B420P-RJ72AA contains several configuration details.

Model Section	Meaning
MPL	MP-Series low-inertia servo motor family
B	Motor frame/performance family designation
420	Frame and stack configuration
P	Motor construction/configuration designation
R	Resolver feedback
J	Keyed shaft configuration
72	No-brake configuration
AA	Factory configuration suffix

The most important distinction for this model is the RJ72 configuration.

The “R” identifies the resolver feedback family, while the “J” corresponds to the keyed shaft configuration and the “72” configuration represents the no-brake version.

This makes the model particularly easy to distinguish from the closely related resolver/keyless and resolver/brake versions.

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17. Advantages for Machine Builders

Compact Servo Package

The 115 mm frame size provides a good balance between motor output and physical size.

For machinery where panel space and machine footprint are important, a compact servo motor can make mechanical packaging easier.

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Fast Dynamic Response

The low rotor inertia helps the motor respond rapidly to command changes.

This is useful when the machine performs repeated motion cycles.

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High-Speed Capability

The 5000 rpm rating provides flexibility for high-speed machine operation.

When a suitable mechanical transmission ratio is selected, the motor can support both high-speed and controlled-motion applications.

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Reliable Feedback Architecture

The resolver feedback system provides continuous feedback for closed-loop motion control.

This supports accurate servo operation without relying on open-loop motor control.

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Flexible Mechanical Installation

The keyed shaft and metric mounting configuration make the motor suitable for many conventional industrial mechanical designs.

The rotatable right-angle connector also helps simplify installation in confined spaces.

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18. Applications Where This Model Is Particularly Suitable

The MPL-B420P-RJ72AA can be considered for applications where the following characteristics are required:

Application Requirement	Suitability
High-speed rotation	Excellent
5000 rpm operation	Yes
Medium-power servo axis	Yes
Resolver feedback	Yes
Keyed shaft	Yes
Integral holding brake	No
Compact machine design	Yes
Repeated acceleration/deceleration	Yes
Precision positioning	Yes
Closed-loop speed control	Yes
Automated machinery	Yes
Packaging equipment	Yes
Material handling	Yes
Machine automation	Yes
Rotary positioning	Yes

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19. Installation Considerations

Correct installation is important for achieving the expected performance and service life of the MPL-B420P-RJ72AA.

The motor should be mounted on a rigid, properly aligned surface. The flange should sit evenly against the machine mounting surface, and the shaft should be aligned with the driven component.

Misalignment can create additional radial and axial forces on the motor shaft and bearings.

The driven coupling should also be selected according to the actual torque, speed, shaft diameter, radial loading, and axial loading requirements of the application.

Cable routing should take advantage of the rotatable right-angle connector. The servo cable should not be forced into a sharp bend immediately at the connector.

Because this model does not include an integral holding brake, applications involving vertical loads, suspended mechanisms, or gravity-driven motion should be evaluated separately.

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20. Maintenance Considerations

Servo motors are generally designed for long-term industrial operation, but the surrounding mechanical and electrical installation has a major influence on service life.

Regular inspection should include:

• Motor mounting condition
• Shaft and coupling alignment
• Cable condition
• Connector condition
• Excessive vibration
• Unusual bearing noise
• Excessive motor temperature
• Mechanical backlash
• Servo drive fault history
• Load changes
• Encoder/resolver feedback condition

A sudden increase in motor temperature, vibration, noise, or positioning error should be investigated rather than ignored.

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21. Recommended Drive and Control Environment

The MPL-B420P-RJ72AA is intended for closed-loop servo control and is associated with compatible motion-control drive systems.

A properly matched servo drive should provide:

• Motor current regulation
• Velocity control
• Position control
• Resolver feedback processing
• Acceleration and deceleration control
• Torque limitation
• Servo fault monitoring
• Motor thermal protection

The final drive selection should always be based on the actual motor configuration, feedback type, required voltage, continuous current, peak current, application duty cycle, and control architecture.

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22. Product Advantages at a Glance

Advantage	Description
5000 rpm speed	Suitable for high-speed motion applications
4.74 Nm continuous torque	Provides stable continuous output
13.5 Nm peak torque	Supports short-duration acceleration loads
1.9 kW power class	Suitable for medium-power servo applications
Low rotor inertia	Supports fast acceleration and deceleration
Resolver feedback	Reliable closed-loop feedback architecture
Keyed shaft	Conventional mechanical coupling interface
No integral brake	Suitable for applications not requiring motor holding brake
115 mm frame	Compact industrial servo package
50.8 mm stack	Balanced torque and physical size
Rotatable connector	Flexible cable-routing arrangement
Metric mounting	Suitable for metric machine construction

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23. Product Specification Summary

Category	Specification
Brand	Allen-Bradley
Series	MP-Series MPL
Model	MPL-B420P-RJ72AA
Motor Type	Low-inertia brushless AC servo motor
Voltage	460 V AC class
Speed	5000 rpm
Continuous Torque	4.74 Nm
Peak Torque	13.5 Nm
Rated Power	1.9 kW
Feedback	Resolver
Shaft	Keyed
Brake	None
Frame	115 mm
Stack	50.8 mm
Connector	SpeedTEC DIN, right angle
Connector Adjustment	180° rotatable
Mounting	Metric flange
Approx. Dimensions	133 × 187 × 98 mm
Approx. Weight	5.44 kg
Motor Class	Low-inertia servo
Primary Use	Industrial motion control

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24. Overall Product Description

The Allen-Bradley MPL-B420P-RJ72AA is a 5000 rpm, 1.9 kW-class low-inertia servo motor designed for industrial motion-control systems that require precise and repeatable rotary movement.

Its 115 mm frame, 50.8 mm magnet stack, 4.74 Nm continuous torque, and 13.5 Nm peak torque provide a balanced combination of speed, torque, and physical size.

The resolver feedback configuration makes this model particularly relevant to applications where resolver-based feedback is preferred. The keyed shaft provides a conventional mechanical connection, while the right-angle SpeedTEC DIN connector offers practical flexibility during machine installation.

Because the motor has no integral brake, it is best suited to machine axes where a motor-mounted holding brake is not required or where the machine incorporates another suitable method of holding the load.

Overall, the MPL-B420P-RJ72AA is a practical choice for high-speed industrial servo applications requiring a compact motor package, reliable closed-loop feedback, fast dynamic response, and straightforward mechanical integration.