Introduction

The Allen Bradley MPL-B310P-RJ74AA Servo Motor belongs to the MP-Series MPL family of low-inertia brushless servo motors. It is engineered for industrial motion systems that require controlled rotary movement and dependable closed-loop feedback.

The defining characteristic of the RJ74AA configuration is its 2-pole resolver feedback. This distinguishes it from other MPL-B310P variants that use incremental or high-resolution absolute feedback. For equipment already designed around resolver-based motion control, retaining the same feedback technology can simplify replacement and maintenance planning.

The motor uses a 100 mm frame with a 25.4 mm magnet stack and provides a rated speed of up to 5000 RPM. Its low-inertia design supports responsive servo operation, making it appropriate for applications involving frequent acceleration, deceleration, indexing, and coordinated movement.

Another important feature is the integrated 24 V DC holding brake. The brake provides a mechanical holding function that can be valuable on vertical or gravity-sensitive axes and other machinery where the load should remain stationary after servo power is disabled. Proper brake sequencing is essential, and the brake should not be treated as a substitute for controlled servo deceleration.

The keyed shaft extension provides a familiar mechanical connection for compatible couplings, while the right-angle SpeedTEC DIN connector can be rotated 180 degrees. This provides greater freedom when designing cable routing and machine layouts.

For industrial spare-parts management, the MPL-B310P-RJ74AA is a useful motor to identify by its complete catalog number rather than by frame size alone. Feedback technology, brake configuration, shaft type, and stack length all affect system compatibility.

Technical Specifications

Specification	MPL-B310P-RJ74AA
Brand	Allen Bradley / Rockwell Automation
Product Family	MP-Series MPL
Product Type	Low-Inertia AC Rotary Servo Motor
Catalog Number	MPL-B310P-RJ74AA
Armature Voltage	460 V AC
Voltage Class	400 V class
Rated Speed	5000 RPM
Rated Torque	1.58 N·m
Frame Size	100 mm (3.94 in.)
Magnet Stack Length	25.4 mm (1.0 in.)
Feedback	2-Pole Resolver
Shaft Configuration	Keyed Shaft Extension
Brake	24 V DC Holding Brake
Connector	SpeedTEC DIN Connector
Connector Configuration	Right Angle
Connector Rotation	180° Rotatable
Mounting	IEC Metric, Free Mounting Holes, Type FF
Motor Type	Brushless Permanent-Magnet Servo Motor
Frame Dimension	100 mm
Magnet Stack Dimension	25.4 mm
Weight	2.70 kg (5.95 lb)

The actual servo performance depends on the connected drive, feedback configuration, mechanical load, duty cycle, ambient temperature, acceleration profile, and machine tuning.

Recommended Related Models

Model	Product Type	Key Configuration
MPL-B310P-RJ72AA	Servo Motor	Resolver, keyed shaft, no brake
MPL-B310P-RJ74AA	Servo Motor	Resolver, keyed shaft, 24 V DC brake
MPL-B310P-RK72AA	Servo Motor	Resolver, keyless shaft, no brake
MPL-B310P-RK74AA	Servo Motor	Resolver, keyless shaft, 24 V DC brake
MPL-B310P-HJ72AA	Servo Motor	Incremental feedback, keyed shaft, no brake
MPL-B310P-HJ74AA	Servo Motor	Incremental feedback, keyed shaft, brake
MPL-B310P-HK74AA	Servo Motor	Incremental feedback, keyless shaft, 24 V DC brake

These models are useful alternatives when a project requires a different shaft arrangement, feedback technology, or brake configuration.

Popular Related Models

Model	Product Family	Typical Configuration
MPL-B310P-MJ72AA	MP-Series MPL	Multi-turn high-resolution feedback, keyed shaft, no brake
MPL-B310P-MJ74AA	MP-Series MPL	Multi-turn high-resolution feedback, keyed shaft, brake
MPL-B310P-MK72AA	MP-Series MPL	Multi-turn high-resolution feedback, keyless shaft, no brake
MPL-B310P-MK74AA	MP-Series MPL	Multi-turn high-resolution feedback, keyless shaft, brake
MPL-B310P-HJ74AA	MP-Series MPL	Incremental feedback, keyed shaft, brake
MPL-B310P-HK74AA	MP-Series MPL	Incremental feedback, keyless shaft, brake
MPL-B310P-SK74AA	MP-Series MPL	Single-turn high-resolution feedback, keyless shaft, brake

The MPL-B310P-RJ74AA is especially suited to systems that specifically require resolver feedback and a 24 V DC holding brake. When selecting a replacement or spare motor, always match the complete catalog number and verify the servo-drive feedback interface rather than relying only on the 100 mm frame size.

Applications

Packaging and Processing Machinery
The MPL-B310P-RJ74AA can be used for indexing, feeding, cutting, sealing, labeling, and other repetitive machine movements. Its high-speed capability helps support short machine cycles while maintaining controlled servo motion.

Automated Assembly Systems
Assembly machines often require repeatable positioning and controlled acceleration. The resolver feedback system provides the servo drive with motor position information for closed-loop control.

Material Handling Equipment
Conveyors, transfer mechanisms, indexing tables, and automated positioning equipment can use this servo motor for controlled rotary movement.

Printing and Converting Machinery
The motor is suitable for applications involving rollers, feeders, cutters, and other synchronized rotary mechanisms where speed and position control are important.

Machine Tools
With a maximum rated speed of 5000 RPM and low-inertia construction, the motor can be applied to suitable machine-tool axes where rapid acceleration and deceleration are required.

Industrial Automation Retrofits
The MPL-B310P-RJ74AA can be considered for replacement projects involving existing Allen-Bradley MP-Series motion equipment, particularly where resolver feedback and a 24 V DC brake are required.

Advantages

Low-Inertia Motion Performance
The MPL series uses a low-inertia servo design that supports fast response to changes in speed and position commands. This is valuable in machines with frequent starts, stops, indexing operations, and direction changes.

2-Pole Resolver Feedback
The MPL-B310P-RJ74AA uses resolver feedback rather than an incremental or absolute encoder. Resolver technology is well suited to industrial motion applications requiring robust position feedback and a compatible resolver-input drive architecture.

5000 RPM Operating Capability
The 5000 RPM rating provides the speed range required by many high-cycle automated machines. Actual operating speed should always be determined by the complete motor-drive-load combination.

Integrated 24 V DC Holding Brake
The built-in 24 V DC brake provides mechanical holding capability when the servo axis is not actively controlling motion. This is particularly useful for applications where the load needs to remain stationary when servo power is removed.

Keyed Shaft Extension
The keyed shaft provides a conventional mechanical interface for compatible couplings and transmission components, making it convenient for many industrial machine designs.

Flexible Connector Orientation
The right-angle SpeedTEC DIN connector can be rotated 180 degrees, providing additional flexibility for cable routing and machine installation.

IEC Metric Mounting
The 100 mm IEC metric frame and free mounting-hole arrangement make the motor suitable for integration into a variety of industrial equipment.

Technical FAQs

1. What type of feedback does the MPL-B310P-RJ74AA use?
The MPL-B310P-RJ74AA uses a 2-pole resolver for motor feedback. The connected servo drive must be capable of correctly interfacing with the resolver feedback device.

2. What is the maximum rated speed of this servo motor?
The MPL-B310P-RJ74AA is rated for 5000 RPM. The actual operating speed should be determined according to the servo drive configuration, mechanical load, duty cycle, and application requirements.

3. Does the MPL-B310P-RJ74AA have an integrated brake?
Yes. This model includes a 24 V DC holding brake. The brake is primarily intended for holding the axis when the motor is not actively producing controlled torque and should not normally be used as the primary dynamic stopping mechanism.

4. What shaft configuration does the RJ74AA use?
The motor has a keyed shaft extension. The coupling or transmission component should be correctly matched to the shaft and installed according to the mechanical manufacturer's requirements.

5. Can the MPL-B310P-RJ74AA be used with an encoder-based servo drive?
Not necessarily. The RJ74AA uses resolver feedback, so the servo drive must support the appropriate resolver interface. A physically similar encoder-based MPL motor is not automatically interchangeable.

6. What should be checked before replacing an existing MPL servo motor with this model?
Verify the motor catalog number, voltage, frame size, magnet stack, feedback type, shaft configuration, brake option, connector arrangement, and servo-drive compatibility. Matching only the frame size is not sufficient for a reliable replacement.

7. How should the 24 V DC brake be controlled?
The brake should be controlled according to the applicable motor and servo-drive architecture. The brake release and servo-enable sequence should be coordinated to prevent unintended axis movement or mechanical shock.

8. What can cause a resolver feedback fault?
Common possibilities include damaged feedback cables, loose connectors, incorrect resolver wiring, poor shielding or grounding, excessive electrical interference, or incorrect drive feedback configuration. Servo diagnostics should be checked together with the physical wiring.

9. What should be checked if the motor vibrates during operation?
Inspect mechanical alignment, coupling installation, load inertia, motor mounting, servo tuning, and resolver feedback. Excessive vibration can also occur when the control loop is improperly tuned or when the mechanical system has a resonance condition.

10. How can the motor be maintained properly?
Regularly inspect the mounting hardware, shaft coupling, motor connectors, power cables, resolver cable, and brake operation. Monitor unusual vibration, noise, temperature, or changes in positioning performance and investigate abnormal conditions before they result in an unexpected shutdown.

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