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MPL-B420P-HJ74AA Low-Inertia Servo Motor

1. Product Overview

The MPL-B420P-HJ74AA is a high-speed, low-inertia brushless servo motor designed for industrial motion-control applications requiring accurate positioning, rapid acceleration and deceleration, and stable continuous torque.

It belongs to the MP-Series MPL Low-Inertia Servo Motor family and uses a 115 mm frame with a 50.8 mm magnet stack. The motor is rated for approximately 5000 RPM, provides 4.74 N·m of continuous torque, and uses a 2000-line incremental encoder for closed-loop motion control.

A major characteristic of the HJ74AA configuration is its integrated 24 V DC holding brake. This distinguishes it from the closely related HJ72AA configuration, which does not have an integrated holding brake.

The motor uses a keyed shaft, a SpeedTec DIN circular connector, and an IEC metric Type FF mounting arrangement. The connector is positioned at a right angle and can be rotated to accommodate different cable-routing requirements.

The MPL-B420P-HJ74AA is particularly suitable for industrial machinery that requires high-speed rotary motion, repeatable positioning, rapid indexing, and load holding when the servo system is not actively generating torque.

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2. Brand and Product Classification

Parameter	Specification
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Servo Motors
Product Type	Rotary Servo Motor
Model	MPL-B420P-HJ74AA
Motor Technology	Brushless Permanent-Magnet Servo Motor
Application	Industrial Motion Control
Frame Size	115 mm
Magnet Stack Length	50.8 mm / 2.0 in.
Voltage Class	400 V AC
Nominal Voltage	460 V AC
Phase	Three Phase
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Torque	4.74 N·m
Peak Torque	Approximately 13.5 N·m
Continuous Power	Approximately 1.9 kW
Feedback	2000-Line Incremental Encoder
Encoder Resolution	2000 Lines/Revolution
Shaft	Keyed
Shaft Seal	No Shaft Seal
Brake	Integrated Holding Brake
Brake Voltage	24 V DC
Connector	Circular SpeedTec DIN
Connector Orientation	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric, Type FF
Rotor Inertia	Approximately 0.00026 kg·m²
Approximate Weight	7.29 kg
Dimensions	115 mm frame class; 50.8 mm magnet stack; complete envelope configuration-dependent
Typical Application	Servo-driven industrial machinery

The exact HJ74AA configuration is listed with a 115 mm frame, 50.8 mm magnet stack, 5000 RPM speed, 2000-line incremental encoder, keyed shaft, 24 V DC holding brake, and SpeedTec DIN connector.

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3. Detailed Technical Specifications

Technical Parameter	MPL-B420P-HJ74AA
Model	MPL-B420P-HJ74AA
Product Family	MP-Series
Product Series	MPL Low-Inertia
Motor Type	Rotary Servo Motor
Motor Construction	Brushless Permanent-Magnet
Voltage Class	400 V AC
Operating Voltage	400/460 V AC
Phase	Three Phase
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Torque	4.74 N·m
Peak Torque	Approximately 13.5 N·m
Rated Power	Approximately 1.9 kW
Feedback Type	Incremental Encoder
Encoder Resolution	2000 lines/revolution
Rotor Inertia	Approximately 0.00026 kg·m²
Shaft	Keyed
Shaft Seal	None
Brake	Holding Brake
Brake Voltage	24 V DC
Connector	Circular SpeedTec DIN
Connector Position	Right Angle
Connector Rotation	180°
Mounting	IEC Metric Type FF
Frame Size	115 mm
Magnet Stack	50.8 mm
Magnet Stack	2.0 in.
Approximate Weight	7.29 kg
Dimensions	115 mm frame class; 50.8 mm stack; complete envelope depends on configuration
Motor Type	Low-Inertia Servo
Typical Drive Application	Industrial Servo Drive
Typical Motion	High-Speed Rotary Motion
Load-Holding Function	Yes, through integrated 24 V brake

The published product information lists the HJ74AA at 4.74 N·m continuous torque, 5000 RPM, 2000 lines/revolution, 115 mm frame size, 50.8 mm stack length, keyed shaft, and 24 V DC holding brake.

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4. Dimensions and Weight

The MPL-B420P-HJ74AA uses a 115 mm frame and a 50.8 mm magnet stack.

The 115 mm figure represents the motor’s frame-size class and is one of the most important dimensions when determining whether the motor can physically replace another B420P motor.

The 50.8 mm magnet-stack dimension corresponds to the 2.0-inch stack configuration used in this motor.

The complete motor envelope is larger than the frame and magnet-stack dimensions alone because the physical assembly also includes the mounting flange, shaft, rear housing, connector, brake assembly, and associated mechanical features.

For an actual replacement project, the exact mechanical drawing should therefore be used for mounting-hole dimensions, shaft extension, shaft diameter, overall length, connector clearance, and cable-routing space.

Mechanical Parameter	Specification
Model	MPL-B420P-HJ74AA
Frame Size	115 mm
Frame Class	B420P
Magnet Stack	50.8 mm
Magnet Stack Length	2.0 in.
Mounting Type	IEC Metric Type FF
Shaft Type	Keyed
Shaft Seal	No
Brake Housing	Integrated 24 V DC holding brake
Connector	SpeedTec DIN
Connector Position	Right Angle
Connector Rotation	180°
Overall Dimensions	Configuration-dependent
Frame Dimension	Approximately 115 mm class
Approximate Weight	7.29 kg
Approximate Shipping/Product Weight	Approximately 7.3 kg

The listed product weight is 16.06 lb, equivalent to approximately 7.29 kg.

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5. Product Series

The MPL-B420P-HJ74AA belongs to the MPL Low-Inertia Servo Motor series within the MP-Series product family.

The MPL series consists of brushless permanent-magnet servo motors designed for industrial motion-control systems.

The series covers multiple motor frame sizes and performance levels. Different suffixes can specify different feedback technologies, shaft configurations, brake arrangements, connector configurations, and voltage-related characteristics.

The B420P motor size provides a combination of relatively high rotational speed, moderate continuous torque, substantial peak torque, and low rotor inertia.

The HJ74AA is therefore a specific B420P configuration rather than a generic motor designation.

This distinction is important when purchasing replacement motors. Two motors can both be identified as B420P but still have different feedback systems, shafts, brakes, or electrical characteristics.

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6. Understanding the Model Number

The model number MPL-B420P-HJ74AA contains several configuration identifiers.

MPL identifies the MPL low-inertia servo motor family.

B420P identifies the motor size and performance class.

HJ74AA identifies the specific configuration, including feedback, shaft, brake, connector, and related electrical and mechanical characteristics.

The HJ74AA configuration is particularly notable for its combination of:

• 2000-line incremental encoder
• Keyed shaft
• 24 V DC holding brake
• SpeedTec DIN connector
• 115 mm frame
• 50.8 mm magnet stack
• 5000 RPM operating speed

When ordering a replacement, the complete MPL-B420P-HJ74AA model number should be matched rather than relying only on the B420P designation.

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7. Motor Performance

7.1 5000 RPM Rated Speed

The MPL-B420P-HJ74AA is designed for operation up to approximately 5000 RPM.

This high rotational speed makes the motor suitable for machinery requiring fast rotary movement and short operating cycles.

High-speed operation can be useful for:

• Indexing
• Feed mechanisms
• Packaging equipment
• Printing machinery
• Converting equipment
• Automated assembly
• Rotary positioning
• High-speed material handling

A servo system can use controlled acceleration and deceleration to bring the motor rapidly between different operating speeds.

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8. Continuous Torque

The motor provides approximately 4.74 N·m continuous torque.

Continuous torque represents the motor’s sustained torque capability under its specified operating conditions.

This level of torque is suitable for many medium-power industrial servo applications.

The actual torque available at a given speed depends on the motor’s operating curve, drive configuration, ambient conditions, duty cycle, and thermal conditions.

For proper motor sizing, the machine’s continuous torque requirement should be evaluated separately from its short-duration acceleration torque.

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9. Peak Torque

The B420P motor family is associated with approximately 13.5 N·m peak torque.

Peak torque is important during short-duration high-load events such as:

• Rapid acceleration
• Rapid deceleration
• Direction reversal
• Indexing
• Load disturbances
• Short-duration process loads

The peak torque capability allows the motor to handle transient loads that are substantially higher than the continuous torque requirement.

The actual allowable peak torque duration depends on the motor, drive, operating speed, thermal conditions, and application duty cycle.

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10. 1.9 kW Power Class

The B420P motor family is rated at approximately 1.9 kW continuous power.

This power level makes the motor suitable for medium-power industrial servo applications.

The combination of approximately 1.9 kW power, 4.74 N·m continuous torque, and 5000 RPM speed provides a useful balance between high-speed operation and continuous mechanical output.

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11. Low-Inertia Construction

The MPL series is designed around low-inertia servo-motor technology.

The B420P family has a listed rotor inertia of approximately:

0.00026 kg·m²

Low rotor inertia is useful for machines that repeatedly accelerate and decelerate.

For example, in a high-speed indexing machine, the motor may need to accelerate rapidly, reach operating speed, decelerate, stop at a defined position, and then immediately repeat the cycle.

A low-inertia motor can reduce the rotating mass that the servo drive must accelerate and decelerate.

This can contribute to:

• Faster dynamic response
• Rapid acceleration
• Rapid deceleration
• Shorter machine cycles
• Responsive positioning
• Reduced mechanical stress during repeated speed changes

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12. 2000-Line Incremental Encoder

The HJ74AA uses a 2000-line incremental encoder.

The encoder provides feedback to the servo-control system, allowing the drive to monitor motor movement and regulate the motor’s operation.

The feedback is used for:

• Position control
• Speed control
• Acceleration control
• Deceleration control
• Direction control
• Motion synchronization

The incremental feedback configuration is different from absolute single-turn and absolute multi-turn configurations found on other MPL models.

Therefore, feedback compatibility must be checked carefully before selecting a replacement.

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13. Integrated 24 V DC Holding Brake

The HJ74AA includes an integrated 24 V DC holding brake.

This is one of the most important differences between the HJ74AA and the closely related HJ72AA configuration.

The brake can mechanically hold the motor shaft when servo torque is not being actively applied.

This is useful for applications where the load must remain stationary after the servo system is disabled.

Typical examples include:

• Vertical axes
• Lifting mechanisms
• Positioning systems
• Machine fixtures
• Material-handling axes
• Gravity-loaded mechanisms
• Automated assembly equipment

The holding brake should generally be regarded as a holding mechanism rather than a substitute for controlled servo deceleration or a machine safety braking system.

The servo system should normally control the motion to a stop before the holding brake is engaged.

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14. HJ74AA Compared with HJ72AA

The HJ74AA and HJ72AA are closely related B420P configurations.

The principal difference is the brake arrangement.

Parameter	MPL-B420P-HJ72AA	MPL-B420P-HJ74AA
Motor Family	MPL-B420P	MPL-B420P
Frame Size	115 mm	115 mm
Magnet Stack	50.8 mm	50.8 mm
Rated Speed	5000 RPM	5000 RPM
Continuous Torque	4.74 N·m	4.74 N·m
Peak Torque	Approx. 13.5 N·m	Approx. 13.5 N·m
Power	Approx. 1.9 kW	Approx. 1.9 kW
Feedback	2000-Line Incremental	2000-Line Incremental
Shaft	Keyed	Keyed
Shaft Seal	None	None
Brake	No Brake	24 V DC Holding Brake
Connector	SpeedTec DIN	SpeedTec DIN
Mounting	IEC Metric	IEC Metric
Approx. Weight	Approx. 4.56 kg	Approx. 7.29 kg

The HJ74AA therefore provides the same general B420P servo-motor performance class while adding the integrated 24 V holding-brake configuration.

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15. Applications

15.1 Industrial Automation

The MPL-B420P-HJ74AA is suitable for industrial automation equipment requiring controlled rotary motion.

Typical functions include:

• Machine-axis control
• Positioning
• Indexing
• Synchronization
• Rotary transfer
• Feed control
• Automated production movement

The high-speed motor and feedback system allow the servo drive to control the axis accurately.

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15.2 Packaging Machinery

Packaging machinery often requires repeated high-speed movement.

The 5000 RPM operating speed and low-inertia design are useful for high-cycle equipment.

Typical applications include:

• Film feeding
• Product positioning
• Sealing mechanisms
• Cutting systems
• Labeling systems
• Rotary indexing
• Packaging transfer
• Feed rollers

The holding brake can also be useful where a machine axis needs to remain stationary during a controlled stop or power-off condition.

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15.3 Printing Machinery

Printing equipment frequently requires synchronized rotary movement between rollers and other mechanical sections.

Servo motors can be used for:

• Feed rollers
• Registration systems
• Web handling
• Cutter positioning
• Roller synchronization
• Indexing mechanisms

The incremental encoder provides feedback for closed-loop motion control.

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15.4 Converting Equipment

Converting machinery processes materials such as paper, film, foil, labels, and similar continuous products.

Servo-controlled motors can be used for:

• Feeding
• Cutting
• Slitting
• Positioning
• Roller synchronization
• Registration

The B420P’s high-speed capability can be useful in machines where the production line operates continuously at elevated speed.

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15.5 Automated Assembly

Assembly machines often require precise and repeatable rotary motion.

Potential uses include:

• Rotary indexing tables
• Component insertion
• Automated fixtures
• Rotary positioning
• Screwdriving systems
• Component transfer
• Clamping mechanisms

The holding brake can be advantageous where a fixture or axis must remain stationary when motor torque is removed.

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15.6 Material Handling

The motor can be used in material-handling systems where servo-controlled rotary movement is required.

Examples include:

• Conveyor systems
• Rotary transfer units
• Feed rollers
• Positioning mechanisms
• Automated handling equipment
• Lifting-related mechanisms

For vertical movement, the integrated holding brake can provide an additional load-holding function.

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15.7 Machine Tools

The MPL-B420P-HJ74AA can be considered for auxiliary machine-tool motion where rapid positioning and controlled rotary movement are required.

Potential applications include:

• Rotary positioning
• Feed mechanisms
• Tool handling
• Workpiece positioning
• Auxiliary axes

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15.8 Inspection Equipment

Inspection machines often require precise movement of cameras, sensors, fixtures, or workpieces.

Servo motors provide repeatable motion that can be synchronized with inspection cycles.

The B420P configuration can be useful where the equipment requires relatively high speed combined with accurate feedback.

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16. Product Advantages

16.1 High-Speed Operation

The 5000 RPM rating allows the motor to support fast machine cycles.

This is useful for high-speed indexing, feeding, positioning, and synchronized rotary movement.

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16.2 Low-Inertia Design

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

This is especially useful in machines that perform frequent start-stop operations.

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16.3 Integrated Holding Brake

The 24 V DC brake provides a mechanical holding function.

This is particularly useful for vertical axes and other applications where the load needs to remain stationary when motor torque is unavailable.

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16.4 4.74 N·m Continuous Torque

The continuous torque rating provides a useful level of sustained mechanical output for medium-power industrial applications.

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16.5 High Peak Torque

The B420P’s approximately 13.5 N·m peak torque capability provides additional short-duration torque for acceleration and transient load conditions.

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16.6 2000-Line Encoder

The incremental encoder provides closed-loop feedback for precise control of motor position and speed.

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16.7 Keyed Shaft

The keyed shaft provides a conventional mechanical connection for compatible couplings, pulleys, gears, and other transmission components.

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16.8 Rotatable Right-Angle Connector

The right-angle SpeedTec DIN connector can be rotated to help accommodate different machine layouts and cable-routing requirements.

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16.9 IEC Metric Mounting

The IEC metric Type FF mounting configuration is suitable for industrial machine designs using metric mechanical dimensions.

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17. Five Related or Same-Series Models

The following models are closely related to the MPL-B420P-HJ74AA and are useful for comparison when selecting feedback, shaft, or motor-size configurations.

Model	Series	Speed	Continuous Torque	Peak Torque	Power	Feedback	Shaft	Brake	Dimensions	Weight
MPL-B420P-HJ72AA	MPL B420P	5000 RPM	4.74 N·m	Approx. 13.5 N·m	1.9 kW	2000-line Incremental	Keyed	No	115 mm frame / 50.8 mm stack	Approx. 4.56 kg
MPL-B420P-MJ72AA	MPL B420P	5000 RPM	4.74 N·m	Approx. 13.5 N·m	1.9 kW	Absolute Multi-Turn	Keyed	No	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-MJ74AA	MPL B420P	5000 RPM	4.74 N·m	Approx. 13.5 N·m	1.9 kW	Absolute Multi-Turn	Keyed	24 V DC	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-SJ72AA	MPL B420P	5000 RPM	4.74 N·m	Approx. 13.5 N·m	1.9 kW	Absolute Single-Turn	Keyed	No	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-SJ74AA	MPL B420P	5000 RPM	4.74 N·m	Approx. 13.5 N·m	1.9 kW	Absolute Single-Turn	Keyed	24 V DC	115 mm frame / 50.8 mm stack	Configuration-dependent

The B420P family includes multiple feedback and brake configurations. The exact suffix should be matched to the servo drive and machine requirements.

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18. B420P Configuration Comparison

Model	Feedback	Shaft	Brake	Speed	Continuous Torque	Peak Torque	Power
MPL-B420P-HJ72AA	2000-Line Incremental	Keyed	No	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW
MPL-B420P-HJ74AA	2000-Line Incremental	Keyed	24 V DC	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW
MPL-B420P-MJ72AA	Absolute Multi-Turn	Keyed	No	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW
MPL-B420P-MJ74AA	Absolute Multi-Turn	Keyed	24 V DC	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW
MPL-B420P-SJ72AA	Absolute Single-Turn	Keyed	No	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW
MPL-B420P-SJ74AA	Absolute Single-Turn	Keyed	24 V DC	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW

This comparison shows why the complete suffix matters. The motor size and basic torque class may remain similar while the feedback and brake configurations change.

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19. Five Representative Same-Brand Models

The following models are representative models from the same servo-motor portfolio and can be used as comparison points for different power and torque requirements.

Model	Series	Speed	Continuous Torque	Peak Torque	Power	Rotor Inertia	Approx. Weight	Dimensions
MPL-B310P	MPL Low-Inertia	5000 RPM	1.58 N·m	3.61 N·m	0.77 kW	0.000044 kg·m²	2.7 kg	Approx. 100 mm frame class; exact envelope configuration-dependent
MPL-B320P	MPL Low-Inertia	5000 RPM	3.05 N·m	7.91 N·m	1.5 kW	0.000078 kg·m²	3.7 kg	Approx. 100 mm frame class; exact envelope configuration-dependent
MPL-B330P	MPL Low-Inertia	5000 RPM	4.18 N·m	11.1 N·m	1.8 kW	0.00012 kg·m²	4.6 kg	Approx. 100 mm frame class; exact envelope configuration-dependent
MPL-B420P	MPL Low-Inertia	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW	0.00026 kg·m²	4.3 kg family value	115 mm frame class; exact envelope configuration-dependent
MPL-B430P	MPL Low-Inertia	5000 RPM	6.55 N·m	19.8 N·m	2.2 kW	0.00038 kg·m²	5.5 kg	Larger B430 frame class; exact envelope configuration-dependent

The published MPL technical data gives the listed speed, torque, power, rotor-inertia, and family weight values for these motor sizes.

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20. Same-Series Performance Comparison

Model	Speed	Continuous Torque	Peak Torque	Power	Rotor Inertia	Weight
MPL-B310P	5000 RPM	1.58 N·m	3.61 N·m	0.77 kW	0.000044 kg·m²	2.7 kg
MPL-B320P	5000 RPM	3.05 N·m	7.91 N·m	1.5 kW	0.000078 kg·m²	3.7 kg
MPL-B330P	5000 RPM	4.18 N·m	11.1 N·m	1.8 kW	0.00012 kg·m²	4.6 kg
MPL-B420P	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW	0.00026 kg·m²	4.3 kg
MPL-B430P	5000 RPM	6.55 N·m	19.8 N·m	2.2 kW	0.00038 kg·m²	5.5 kg

The B420P is positioned between the B330P and B430P in terms of continuous torque and power.

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21. Application Selection Guide

Application Requirement	Suitable Model / Configuration
Lower-power high-speed motion	MPL-B310P
Medium-power motion	MPL-B320P
Higher torque in the smaller MPL range	MPL-B330P
4.74 N·m continuous torque with incremental feedback	MPL-B420P-HJ74AA
B420P without integrated brake	MPL-B420P-HJ72AA
B420P with multi-turn feedback	MPL-B420P-MJ72AA / MJ74AA
B420P with single-turn feedback	MPL-B420P-SJ72AA / SJ74AA
Higher torque and power	MPL-B430P

The final motor selection should be based on the complete catalog number, drive compatibility, machine mechanics, load profile, feedback requirements, and brake requirements.

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22. Drive Compatibility Considerations

The MPL-B420P-HJ74AA is intended for use within compatible industrial servo-control systems.

Before installation, the following should be checked:

• Servo-drive model
• Drive voltage class
• Motor feedback interface
• Encoder resolution
• Motor cable
• Feedback cable
• Brake wiring
• Motor parameters
• Drive firmware or configuration requirements
• Motor thermal requirements
• Machine safety requirements

The fact that two motors have the same frame and torque rating does not necessarily mean that they are electrically interchangeable.

The HJ74AA’s 2000-line incremental encoder and 24 V brake should be specifically supported by the selected servo system.

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23. Mechanical Installation

The motor uses an IEC metric Type FF mounting arrangement.

The mounting surface should be properly aligned to prevent mechanical stress on the motor shaft.

When installing the motor, attention should be paid to:

• Mounting-hole alignment
• Flange flatness
• Shaft alignment
• Coupling alignment
• Shaft loading
• Connector clearance
• Cable bending radius
• Brake wiring
• Motor cable routing

The keyed shaft should be used with a compatible coupling or transmission component.

Excessive radial or axial loading on the shaft can reduce bearing life and affect motor performance.

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24. Brake Operation

The integrated 24 V DC brake is intended primarily as a holding brake.

A typical sequence for a controlled axis can involve:

1. Servo drive decelerates the motor.
2. Motor reaches the commanded stop position.
3. Servo torque is maintained as required.
4. Holding brake is engaged.
5. Servo output can then be disabled according to the machine-control sequence.

The exact sequence depends on the servo drive and machine control architecture.

For safety-critical applications, the brake should not be treated as the sole protective measure. Appropriate safety-rated stopping and load-holding methods should be designed according to the machine requirements.

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25. Maintenance Considerations

Regular inspection can help maintain reliable operation.

Recommended inspection points include:

• Motor mounting bolts
• Shaft coupling
• Encoder cable
• Motor power cable
• Brake wiring
• Connector condition
• Grounding
• Abnormal vibration
• Unusual motor noise
• Excessive temperature
• Positioning accuracy
• Brake holding performance
• Mechanical wear
• Cable insulation

The brake should also be checked periodically in applications where reliable holding performance is important.

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26. Typical Equipment

Equipment	Typical Servo Function
Packaging Machinery	Indexing and product positioning
Labeling Machinery	Feed and registration
Printing Machinery	Roller synchronization
Converting Machinery	Feed and cutting
Assembly Machinery	Rotary positioning
Material Handling	Controlled rotary movement
Machine Tools	Auxiliary positioning
Inspection Equipment	Fixture and sensor positioning
Automated Production Lines	Synchronized motion
Rotary Tables	Indexing
Automated Fixtures	Positioning and clamping
Feed Systems	Controlled roller movement

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27. Advantages for High-Speed Automation

The combination of 5000 RPM speed and low rotor inertia is particularly useful for high-cycle machinery.

In applications where the motor repeatedly accelerates, moves, stops, and reverses direction, the motor’s low-inertia construction can support responsive motion control.

The 4.74 N·m continuous torque rating provides sustained output, while the higher peak torque capability supports short acceleration and transient load requirements.

The 24 V holding brake adds another useful function for applications where the axis must remain mechanically stationary after the servo motor stops.

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28. Advantages for Vertical Applications

The integrated brake is especially relevant to vertical axes.

A vertical load can generate gravitational torque on the motor even when the motor is not commanded to move.

In such applications, the brake can provide a mechanical holding function after the motor has been brought to a controlled stop.

Potential applications include:

• Vertical lifting
• Automated elevators within machinery
• Vertical positioning
• Lift tables
• Material transfer
• Vertical fixtures
• Automated loading systems

The complete load-holding and safety design should consider the mechanical transmission, load mass, axis orientation, emergency-stop behavior, and machine safety requirements.

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29. HJ74AA Mechanical and Electrical Advantages

Feature	Benefit
115 mm Frame	Suitable for medium-size industrial servo installations
50.8 mm Stack	B420P performance configuration
5000 RPM	High-speed operation
4.74 N·m Continuous Torque	Sustained mechanical output
Approx. 13.5 N·m Peak Torque	Short-duration acceleration capability
1.9 kW Power	Medium-power servo operation
Low Rotor Inertia	Rapid dynamic response
2000-Line Encoder	Closed-loop feedback
Keyed Shaft	Conventional mechanical coupling
24 V DC Brake	Load-holding function
SpeedTec DIN Connector	Industrial connection system
180° Connector Rotation	Flexible cable routing
IEC Metric Type FF	Standardized mounting arrangement

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30. Replacement Considerations

The MPL-B420P-HJ74AA should be replaced with a motor having compatible:

• Frame size
• Stack length
• Voltage
• Speed
• Torque
• Feedback
• Encoder resolution
• Shaft design
• Brake configuration
• Connector
• Mounting arrangement
• Drive compatibility

The suffix is particularly important.

For example, the HJ74AA configuration uses a 2000-line incremental encoder, keyed shaft, and 24 V holding brake.

A different B420P suffix may use absolute single-turn feedback, absolute multi-turn feedback, a keyless shaft, or a different brake configuration.

Therefore, replacing the motor based only on the B420P designation can result in an incompatible installation.

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31. Five Related Models – Detailed Comparison

Model	Feedback	Brake	Shaft	Speed	Continuous Torque	Power	Dimensions	Weight
MPL-B420P-HJ72AA	2000-Line Incremental	No	Keyed	5000 RPM	4.74 N·m	1.9 kW	115 mm frame / 50.8 mm stack	Approx. 4.56 kg
MPL-B420P-MJ72AA	Absolute Multi-Turn	No	Keyed	5000 RPM	4.74 N·m	1.9 kW	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-MJ74AA	Absolute Multi-Turn	24 V DC	Keyed	5000 RPM	4.74 N·m	1.9 kW	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-SJ72AA	Absolute Single-Turn	No	Keyed	5000 RPM	4.74 N·m	1.9 kW	115 mm frame / 50.8 mm stack	Configuration-dependent
MPL-B420P-SJ74AA	Absolute Single-Turn	24 V DC	Keyed	5000 RPM	4.74 N·m	1.9 kW	115 mm frame / 50.8 mm stack	Configuration-dependent

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32. Five Representative Same-Brand Models – Detailed Comparison

Model	Speed	Continuous Torque	Peak Torque	Power	Rotor Inertia	Weight	Dimensions
MPL-B310P	5000 RPM	1.58 N·m	3.61 N·m	0.77 kW	0.000044 kg·m²	2.7 kg	Approx. 100 mm frame class; full dimensions configuration-dependent
MPL-B320P	5000 RPM	3.05 N·m	7.91 N·m	1.5 kW	0.000078 kg·m²	3.7 kg	Approx. 100 mm frame class; full dimensions configuration-dependent
MPL-B330P	5000 RPM	4.18 N·m	11.1 N·m	1.8 kW	0.00012 kg·m²	4.6 kg	Approx. 100 mm frame class; full dimensions configuration-dependent
MPL-B420P	5000 RPM	4.74 N·m	13.5 N·m	1.9 kW	0.00026 kg·m²	4.3 kg family value	115 mm frame class; full dimensions configuration-dependent
MPL-B430P	5000 RPM	6.55 N·m	19.8 N·m	2.2 kW	0.00038 kg·m²	5.5 kg	Larger B430 frame class; full dimensions configuration-dependent

The published MPL technical data gives the listed performance values for the B310P through B430P motor families.

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33. Technical Specification Summary

Item	MPL-B420P-HJ74AA
Brand	Allen-Bradley
Product Family	MP-Series
Product Series	MPL Low-Inertia Servo Motors
Model	MPL-B420P-HJ74AA
Product Type	Rotary Servo Motor
Motor Technology	Brushless Permanent-Magnet Servo
Voltage Class	400 V AC
Operating Voltage	400/460 V AC
Phase	Three Phase
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Torque	4.74 N·m
Peak Torque	Approximately 13.5 N·m
Continuous Power	Approximately 1.9 kW
Rotor Inertia	Approximately 0.00026 kg·m²
Feedback	2000-Line Incremental Encoder
Encoder Resolution	2000 Lines/Revolution
Shaft	Keyed
Shaft Seal	No Shaft Seal
Brake	Integrated Holding Brake
Brake Voltage	24 V DC
Connector	Circular SpeedTec DIN
Connector Style	Right Angle
Connector Rotation	180°
Mounting	IEC Metric Type FF
Frame Size	115 mm
Magnet Stack	50.8 mm / 2.0 in.
Dimensions	115 mm frame class; 50.8 mm stack; complete envelope configuration-dependent
Weight	Approximately 7.29 kg
Typical Application	Industrial Motion Control
Typical Machines	Packaging, assembly, printing, converting, material handling, machine tools
Closely Related Model	MPL-B420P-HJ72AA
Main Difference from HJ72AA	HJ74AA includes 24 V DC holding brake

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34. Final Product Description

The MPL-B420P-HJ74AA is a 115 mm-frame, low-inertia industrial servo motor designed for demanding rotary motion-control applications.

Its main performance characteristics include approximately 5000 RPM rated speed, 4.74 N·m continuous torque, approximately 13.5 N·m peak torque, and approximately 1.9 kW continuous power.

The motor uses a 2000-line incremental encoder, providing closed-loop feedback for position and speed control.

Its keyed shaft provides a conventional mechanical interface for couplings and other rotating transmission components.

The integrated 24 V DC holding brake is one of the most important characteristics of the HJ74AA configuration. It provides a mechanical holding function when the motor is not actively producing servo torque and is particularly useful for vertical or gravity-loaded axes.

The SpeedTec DIN right-angle connector can be rotated through approximately 180°, giving the installer additional flexibility when routing motor cables inside a machine.

The motor’s low-inertia design is useful for applications involving repeated acceleration, deceleration, indexing, and direction changes.

Typical applications include packaging equipment, automated assembly machines, printing and converting equipment, material-handling systems, machine tools, inspection machinery, rotary positioning systems, and other industrial automation equipment.

For replacement purposes, the complete MPL-B420P-HJ74AA model number should be matched carefully. The B420P family includes multiple configurations with different feedback systems, brake options, and shaft arrangements.

The HJ74AA should therefore be identified specifically by its 2000-line incremental encoder, keyed shaft, 24 V DC holding brake, 115 mm frame, 50.8 mm magnet stack, and 5000 RPM operating class.

In practical terms, the MPL-B420P-HJ74AA can be summarized as a high-speed, low-inertia, 1.9 kW-class industrial servo motor with 4.74 N·m continuous torque, approximately 13.5 N·m peak torque, 5000 RPM speed, incremental encoder feedback, keyed shaft, and integrated 24 V holding brake.