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Allen-Bradley MPL-B320P-RK74AA Servo Motor – Detailed Product Information

1. Product Introduction

The Allen-Bradley MPL-B320P-RK74AA is a low-inertia AC rotary servo motor designed for industrial motion-control systems that require accurate positioning, controlled speed, rapid acceleration and deceleration, and reliable closed-loop feedback.

The motor belongs to the MP-Series MPL low-inertia brushless servo motor family. The B320P motor configuration uses a 100 mm frame size, a 50.8 mm magnetic stack, a 5000 RPM speed rating, resolver feedback, a keyless shaft extension, and a 24 V DC holding brake. The motor also uses a right-angle SpeedTEC DIN connector with 180° rotational flexibility.

The RK74AA configuration is particularly useful because it combines a keyless shaft with an integrated 24 V DC brake. This makes it different from the RK72AA version, which has the same general resolver/keyless configuration but does not include the integral brake.

The motor is designed to operate as part of a complete servo system. The motor, servo drive, controller, feedback system, cables, coupling, gearbox if required, and machine load must all be considered together when designing a motion-control axis.

The B320P motor family provides approximately 1.5 kW rated output, 3.05 N·m continuous stall torque, and 7.91 N·m peak stall torque, with a rated speed of 5000 RPM.

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2. Brand and Product Series

Brand

Brand: Allen-Bradley

Product Series

Series: MP-Series MPL Low-Inertia Servo Motors

The MPL family is a brushless permanent-magnet servo motor family intended for industrial motion applications.

The B320P configuration is a 5000 RPM motor with a 100 mm frame and 50.8 mm magnetic stack. Within the same family, different motor sizes and feedback configurations are available for different torque, power, inertia, shaft, and brake requirements.

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3. Basic Product Parameters

Parameter	Specification
Model	MPL-B320P-RK74AA
Brand	Allen-Bradley
Product Type	AC Rotary Servo Motor
Product Family	MP-Series MPL
Series Type	Low-Inertia Brushless Servo Motor
Motor Construction	Brushless Permanent-Magnet Servo Motor
Voltage Class	400 V AC class
Armature Voltage	460 V
Product Voltage Rating	480 V AC
Rated Power	1.5 kW
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Stall Torque	3.05 N·m
Peak Stall Torque	7.91 N·m
Feedback	Resolver
Feedback Type	2-pole resolver
Shaft	Keyless shaft extension
Shaft Seal	No shaft seal
Brake	24 V DC holding brake
Connector	SpeedTEC DIN
Connector Configuration	Right-angle
Connector Rotation	180° rotatable
Mounting	IEC metric flange
Mounting Hole Type	Free mounting holes, Type FF
Frame Size	100 mm
Frame Class	Frame 3
Magnetic Stack Length	50.8 mm
Phase	3-phase
Duty	S1 continuous-duty type
Rotor Inertia	Approx. 0.000078 kg·m²
Maximum Operating Temperature Reference	Approx. 40 °C
Approx. Dimensions	Approx. 42.8 × 21.7 × 26.0 cm, B320P family reference
Approx. Weight	Approx. 6.8 kg
Brake Supply	24 V DC
Typical Application	Industrial servo motion control

The exact product configuration identifies the motor as a 460 V-class B320P servo motor with resolver feedback, keyless shaft, right-angle SpeedTEC DIN connector, and 24 V DC brake.

The listed weight of 15 lb corresponds to approximately 6.8 kg.

The dimensional value shown above is a practical B320P-family envelope reference. For a machine installation, the exact mechanical drawing should always be used to confirm mounting dimensions, shaft projection, connector clearance, and cable bend space.

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4. Model Number Explanation

Understanding the model number is useful when comparing the RK74AA with other B320P configurations.

Model Code	Meaning
MPL	MPL low-inertia brushless servo motor family
B	460 V-class motor family
3	Frame size 3 / approximately 100 mm frame
20	50.8 mm magnetic stack
P	5000 RPM speed class
R	Resolver feedback
K	Keyless shaft extension
7	SpeedTEC DIN right-angle connector, 180° rotatable
4	24 V DC brake
AA	Standard catalog configuration

The most important configuration information in the final part of the model number is the combination of R, K, 7, and 4.

The R identifies resolver feedback.

The K identifies the keyless shaft configuration.

The 7 identifies the right-angle SpeedTEC DIN connector arrangement.

The 4 identifies the 24 V DC brake configuration.

This is why the RK74AA is mechanically different from the RJ74AA: the RJ74AA uses a keyed shaft, while the RK74AA uses a keyless shaft.

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5. Detailed Motor Performance

Performance Parameter	MPL-B320P-RK74AA
Rated Output	1.5 kW
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Stall Torque	3.05 N·m
Peak Stall Torque	7.91 N·m
Rotor Inertia	Approx. 0.000078 kg·m²
Frame Size	100 mm
Magnetic Stack Length	50.8 mm
Approx. Dimensions	42.8 × 21.7 × 26.0 cm, family reference
Approx. Weight	6.8 kg

The 1.5 kW output rating makes the B320P a useful mid-size configuration within the B-series MPL motor range.

The 3.05 N·m continuous stall torque provides the motor’s basic continuous torque capability, while the 7.91 N·m peak stall torque provides additional short-duration torque capability for acceleration, deceleration, indexing, and transient machine loads.

The motor’s rotor inertia is approximately 0.000078 kg·m², which is one of the reasons the B320P is suitable for applications requiring frequent changes in speed.

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6. Electrical Specifications

Electrical Parameter	Specification
Model	MPL-B320P-RK74AA
Motor Type	Brushless AC Servo Motor
Voltage Class	400 V AC
Armature Voltage	460 V
Product Rating	480 V AC
Rated Power	1.5 kW
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Phase	3-phase
Feedback	Resolver
Feedback Type	2-pole resolver
Brake	24 V DC holding brake
Duty	S1
Rotor Inertia	Approx. 0.000078 kg·m²
Approx. Dimensions	42.8 × 21.7 × 26.0 cm, family reference
Approx. Weight	6.8 kg

The motor should be operated through a compatible servo drive rather than treated as a conventional motor connected directly to a standard motor starter.

The servo drive manages current, torque, speed, feedback processing, acceleration, deceleration, and positioning functions.

The 24 V DC brake should be integrated into the complete machine control design. The motor brake is primarily a holding function and should not automatically be treated as a substitute for the machine’s independent safety stopping system.

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7. Mechanical Specifications

Mechanical Parameter	Specification
Model	MPL-B320P-RK74AA
Frame Size	100 mm
Frame Class	Frame 3
Magnetic Stack Length	50.8 mm
Shaft Type	Keyless shaft extension
Shaft Seal	No shaft seal
Mounting Flange	IEC metric
Mounting Hole Style	Free mounting holes, Type FF
Connector	SpeedTEC DIN
Connector Orientation	Right-angle
Connector Rotation	180°
Integral Brake	24 V DC
Approx. Overall Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg

The keyless shaft is an important mechanical feature of the RK74AA.

Instead of relying on a traditional shaft key to transmit torque, the machine normally uses a suitable clamping coupling or compatible mechanical transmission arrangement.

This can be advantageous when the machine builder wants a clean shaft interface without relying on a conventional key-and-keyway connection.

The coupling must be selected according to the actual continuous torque, peak torque, operating speed, shaft dimensions, misalignment, acceleration, and load characteristics.

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8. Keyless Shaft Configuration

The keyless shaft is one of the main features that distinguishes the RK74AA from the RJ74AA.

Feature	MPL-B320P-RK74AA	MPL-B320P-RJ74AA
Feedback	Resolver	Resolver
Shaft	Keyless	Keyed
Brake	24 V DC	24 V DC
Rated Speed	5000 RPM	5000 RPM
Rated Power	1.5 kW	1.5 kW
Continuous Torque	3.05 N·m	3.05 N·m
Peak Torque	7.91 N·m	7.91 N·m
Frame	100 mm	100 mm
Stack	50.8 mm	50.8 mm
Approx. Dimensions	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg	Approx. 6.8 kg

Both configurations provide the same general B320P motor performance, but the shaft interface is different.

A keyed shaft is generally used where the machine transmission already uses a conventional key.

A keyless shaft is generally used with a suitable clamping coupling or equivalent shaft connection.

Therefore, the shaft configuration should be treated as a mechanical selection parameter rather than simply an electrical option.

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9. Resolver Feedback

The MPL-B320P-RK74AA uses resolver feedback.

A resolver provides rotor position information to the servo drive and allows the drive to control the motor in a closed-loop configuration.

This is important for machine functions such as:

• Position control
• Speed control
• Torque control
• Indexing
• Electronic gearing
• Synchronized motion
• Controlled acceleration
• Controlled deceleration
• Repetitive positioning

The resolver is integrated into the motor configuration, so the motor and compatible servo drive must be treated as a matched feedback system.

For industrial equipment, resolver feedback can be useful when a robust and established rotary feedback technology is preferred.

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10. 24 V DC Holding Brake

The RK74AA includes a 24 V DC holding brake.

This is one of the most important differences between the RK74AA and RK72AA versions.

Brake Characteristic	MPL-B320P-RK74AA
Brake Included	Yes
Brake Voltage	24 V DC
Brake Type	Holding Brake
Shaft	Keyless
Feedback	Resolver
Rated Speed	5000 RPM
Rated Power	1.5 kW
Approx. Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg

The holding brake can be particularly useful in vertical-axis machinery.

For example, a vertical slide may tend to move downward under gravity when motor torque is removed. A motor-mounted holding brake can provide additional shaft-holding capability when the servo is disabled.

The brake should be controlled according to the complete servo system’s operating sequence.

For high-cycle applications, the brake should not be treated as a high-speed dynamic stopping device unless the complete brake specification and machine design specifically support that operating method.

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11. SpeedTEC DIN Connector

The motor uses a right-angle SpeedTEC DIN connector.

The connector is designed to provide flexibility during machine installation and can be rotated through 180 degrees.

This feature is useful when the motor is mounted close to:

• Machine frames
• Gearboxes
• Guarding
• Cable trays
• Linear modules
• Structural members
• Enclosures
• Other motors

The connector orientation can be selected to improve cable routing and reduce interference with surrounding equipment.

Servo cables should be properly supported and should not place excessive pulling force or bending force on the motor connector.

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12. Low-Inertia Motor Design

The MPL-B320P-RK74AA is part of the low-inertia MPL motor family.

The B320P rotor inertia is approximately:

0.000078 kg·m²

Low rotor inertia is valuable when the machine frequently changes motor speed.

For example, an indexing machine may accelerate rapidly, reach a target position, decelerate, stop, reverse direction, and repeat the cycle.

A lower motor inertia can help the servo system respond quickly to these commands when the mechanical load is appropriately matched.

However, the total machine response depends on more than the motor.

The following should also be considered:

• Load inertia
• Reflected inertia
• Gear ratio
• Coupling stiffness
• Mechanical resonance
• Load torque
• Acceleration rate
• Deceleration rate
• Servo gain settings
• Machine structure
• Required settling time

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13. Product Dimensions and Weight

Physical dimensions are especially important when this motor is being used as a replacement unit.

The B320P family uses a 100 mm frame and 50.8 mm magnetic stack.

Physical Parameter	MPL-B320P-RK74AA
Frame Size	100 mm
Frame Class	Frame 3
Magnetic Stack	50.8 mm
Mounting Type	IEC metric flange
Shaft Type	Keyless
Connector	Right-angle SpeedTEC DIN
Connector Rotation	180°
Approx. Overall Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg

The approximate weight is based on the listed 15 lb motor weight, equivalent to approximately 6.8 kg.

The dimensional figure should be treated as a B320P-family envelope reference. For an actual machine installation, the exact mechanical drawing should be used to verify flange dimensions, shaft projection, bolt locations, connector clearance, and cable bend radius.

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14. Typical Industrial Applications

14.1 Packaging Machinery

The MPL-B320P-RK74AA can be used in packaging machines where high-speed and repeatable servo movement are required.

Typical functions include:

• Product feeding
• Indexing
• Cutting
• Sealing
• Label positioning
• Conveyor synchronization
• Rotary positioning

The 5000 RPM rating provides useful speed capability for high-cycle packaging systems.

The integrated brake can also be useful when a machine axis needs additional holding capability during shutdown.

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14.2 Automated Assembly Equipment

Assembly machinery frequently requires precise coordination between multiple axes.

The motor can be used for:

• Rotary indexing tables
• Component feeding
• Transfer mechanisms
• Tool positioning
• Assembly stations
• Rotary actuators
• Automated fixtures

The resolver feedback supports closed-loop control of the motor position.

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14.3 Material Handling

The motor can be used for controlled movement in automated handling systems.

Typical applications include:

• Rollers
• Conveyors
• Transfer units
• Rotary handling mechanisms
• Positioning systems
• Lift mechanisms

The holding brake can be particularly useful when the motor is used on a vertical or inclined axis.

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14.4 Printing Machinery

Printing systems often require synchronized motion between multiple machine sections.

Servo motors can be used for:

• Feed rollers
• Registration mechanisms
• Web handling
• Rotary positioning
• Electronic gearing
• Synchronization

The low-inertia construction can be useful where the machine repeatedly changes speed.

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14.5 Converting Equipment

Converting machinery can include slitting, winding, cutting, feeding, indexing, and other controlled rotary processes.

The 5000 RPM speed class and servo feedback make the B320P suitable for a variety of controlled rotary axes, subject to actual load and speed requirements.

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14.6 Labeling Equipment

Labeling systems require controlled product movement and accurate timing.

The motor can be used for:

• Label feed rollers
• Product indexing
• Rotary feed systems
• Synchronization mechanisms
• Positioning axes

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14.7 Machine Tools

The motor can be used for machine-tool auxiliary axes and other controlled rotary mechanisms.

Potential uses include:

• Indexing
• Positioning
• Material transfer
• Tool handling
• Auxiliary feed systems

The exact selection depends on load inertia, required torque, speed, machine duty cycle, and servo-drive compatibility.

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14.8 Inspection and Test Equipment

Automated inspection equipment frequently requires precise movement of fixtures, rotary stages, sensors, or workpieces.

The B320P can be used where the machine needs repeatable servo-controlled movement.

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14.9 Electronics Manufacturing Equipment

Electronics production equipment often uses servo motors for:

• Component feeding
• Indexing
• Positioning
• Automated assembly
• Pick-and-place mechanisms
• Rotary stations

The compact 100 mm frame can be useful where machine space is restricted.

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15. Main Product Advantages

15.1 5000 RPM High-Speed Capability

The motor has a rated speed of 5000 RPM.

This provides a useful operating range for high-speed industrial automation.

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15.2 1.5 kW Rated Output

The 1.5 kW rating provides a practical balance between physical size, torque capability, and machine performance.

It is suitable for many general-purpose servo axes that require more power than smaller MPL configurations.

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15.3 3.05 N·m Continuous Torque

The B320P provides approximately 3.05 N·m of continuous stall torque.

This makes it suitable for a broad range of industrial rotary axes.

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15.4 7.91 N·m Peak Torque

The peak torque rating of approximately 7.91 N·m provides additional short-duration capability.

This can be useful during:

• Acceleration
• Deceleration
• Indexing
• Direction changes
• Short-duration overload events

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15.5 Low Rotor Inertia

The approximately 0.000078 kg·m² rotor inertia allows the motor to respond efficiently to speed changes when properly matched with the machine load.

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15.6 Resolver Feedback

Resolver feedback provides closed-loop rotor position information.

This enables the servo system to control motor speed and position rather than operating as a simple open-loop motor.

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15.7 Integrated 24 V DC Brake

The built-in 24 V DC brake is useful where the shaft needs additional holding capability.

This can be particularly important for vertical-axis applications.

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15.8 Keyless Shaft

The keyless shaft provides a clean mechanical interface for suitable clamp-style couplings and other compatible transmission arrangements.

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15.9 Flexible Connector Orientation

The 180° rotatable right-angle connector provides additional flexibility for cable routing.

This can make the motor easier to install in compact machine structures.

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16. Advantages for Machine Builders

The MPL-B320P-RK74AA provides several useful features for machine builders.

The 100 mm frame provides a relatively compact package for a 1.5 kW, 5000 RPM servo motor.

The keyless shaft can simplify certain mechanical transmission designs.

The resolver feedback provides closed-loop feedback for controlled motion.

The integral 24 V DC brake can eliminate the need for a separate motor-mounted holding brake in applications where the motor brake is appropriate.

The right-angle connector can improve cable routing in compact machine layouts.

The combination of these features makes the motor suitable for a variety of packaging, assembly, handling, positioning, and automated production systems.

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17. Advantages for Retrofit and Replacement Applications

When replacing an existing servo motor, matching the motor power alone is not sufficient.

The following characteristics should be compared.

Replacement Parameter	MPL-B320P-RK74AA
Brand	Allen-Bradley
Series	MP-Series MPL
Frame	100 mm
Stack	50.8 mm
Voltage Class	400 V AC
Armature Voltage	460 V
Rated Power	1.5 kW
Rated Speed	5000 RPM
Continuous Torque	3.05 N·m
Peak Torque	7.91 N·m
Feedback	Resolver
Shaft	Keyless
Brake	24 V DC
Connector	SpeedTEC DIN
Connector Style	Right-angle
Mounting	IEC metric
Approx. Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg

A replacement should also be checked against the existing servo drive.

The feedback system, brake circuit, connector configuration, shaft arrangement, mounting geometry, and machine load should all be compatible.

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18. Five Closely Related or Same-Series Models

The following models are closely related to the B320P-RK74AA configuration.

Model	Feedback	Shaft	Brake	Speed	Power	Continuous Torque	Frame / Stack	Approx. Dimensions	Approx. Weight
MPL-B320P-RK72AA	Resolver	Keyless	No brake	5000 RPM	1.5 kW	3.05 N·m	100 mm / 50.8 mm	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 3.7–3.9 kg
MPL-B320P-RJ74AA	Resolver	Keyed	24 V DC	5000 RPM	1.5 kW	3.05 N·m	100 mm / 50.8 mm	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 6.8 kg
MPL-B320P-RJ72AA	Resolver	Keyed	No brake	5000 RPM	1.5 kW	3.05 N·m	100 mm / 50.8 mm	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 3.85 kg
MPL-B320P-MK74AA	Multi-turn absolute	Keyless	24 V DC	5000 RPM	1.5 kW	3.05 N·m	100 mm / 50.8 mm	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 6–7 kg
MPL-B320P-MJ74AA	Multi-turn absolute	Keyed	24 V DC	5000 RPM	1.5 kW	3.05 N·m	100 mm / 50.8 mm	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 6–7 kg

The MPL-B320P-RK72AA is the closest no-brake counterpart to the RK74AA.

The MPL-B320P-RJ74AA retains the brake and resolver but changes the shaft from keyless to keyed.

The MPL-B320P-MK74AA retains the keyless shaft and brake but changes the feedback system from resolver to multi-turn absolute encoder.

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19. Related Model Comparison

Feature	MPL-B320P-RK74AA	MPL-B320P-RK72AA	MPL-B320P-RJ74AA	MPL-B320P-MK74AA	MPL-B320P-MJ74AA
Frame	100 mm	100 mm	100 mm	100 mm	100 mm
Stack	50.8 mm	50.8 mm	50.8 mm	50.8 mm	50.8 mm
Rated Speed	5000 RPM	5000 RPM	5000 RPM	5000 RPM	5000 RPM
Rated Power	1.5 kW	1.5 kW	1.5 kW	1.5 kW	1.5 kW
Continuous Torque	3.05 N·m	3.05 N·m	3.05 N·m	3.05 N·m	3.05 N·m
Peak Torque	7.91 N·m	7.91 N·m	7.91 N·m	7.91 N·m	7.91 N·m
Feedback	Resolver	Resolver	Resolver	Multi-turn absolute	Multi-turn absolute
Shaft	Keyless	Keyless	Keyed	Keyless	Keyed
Brake	24 V DC	No	24 V DC	24 V DC	24 V DC
Connector	SpeedTEC DIN	SpeedTEC DIN	SpeedTEC DIN	SpeedTEC DIN	SpeedTEC DIN
Approx. Dimensions	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg	3.7–3.9 kg	6.8 kg	6–7 kg	6–7 kg

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20. Five Same-Brand Common Models for Comparison

The following models provide useful comparison points within the same general servo motor portfolio.

Model	Series	Rated Speed	Rated Power	Continuous Torque	Peak Torque	Feedback	Shaft	Brake	Approx. Dimensions	Approx. Weight
MPL-B310P-MJ74AA	MPL B-Series	5000 RPM	0.77 kW	1.58 N·m	3.61 N·m	Multi-turn absolute	Keyed	24 V DC	Approx. B310 family envelope	Approx. 2.7 kg
MPL-B320P-MK74AA	MPL B-Series	5000 RPM	1.5 kW	3.05 N·m	7.91 N·m	Multi-turn absolute	Keyless	24 V DC	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 6–7 kg
MPL-B330P-MK74AA	MPL B-Series	5000 RPM	1.8 kW	4.18 N·m	11.1 N·m	Multi-turn absolute	Keyless	24 V DC	Approx. B330 family envelope	Approx. 6.1 kg
MPL-B420P-MJ74AA	MPL B-Series	5000 RPM	1.9 kW	4.74 N·m	13.5 N·m	Multi-turn absolute	Keyed	24 V DC	Approx. 46 × 23 × 28 cm	Approx. 6.4 kg
MPL-B430P-MJ72AA	MPL B-Series	5000 RPM	2.2 kW	6.55 N·m	19.8 N·m	Multi-turn absolute	Keyed	No brake	Approx. 46 × 23 × 28 cm	Approx. 9.2 kg

The B310P through B430P configurations represent progressively different motor sizes and performance levels within the same broad MPL B-series range.

The published family data lists the B310P at 0.77 kW, the B320P at 1.5 kW, the B330P at 1.8 kW, the B420P at 1.9 kW, and the B430P at 2.2 kW, all in the 5000 RPM class.

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21. B-Series Motor Performance Comparison

Motor Family	Model	Rated Speed	Rated Power	Continuous Stall Torque	Peak Stall Torque	Rotor Inertia	Approx. Dimensions	Approx. Weight
B310P	MPL-B310P	5000 RPM	0.77 kW	1.58 N·m	3.61 N·m	0.000044 kg·m²	B310 family envelope	Approx. 2.4 kg
B320P	MPL-B320P	5000 RPM	1.5 kW	3.05 N·m	7.91 N·m	0.000078 kg·m²	B320 family envelope	Approx. 4.5 kg
B330P	MPL-B330P	5000 RPM	1.8 kW	4.18 N·m	11.1 N·m	0.00012 kg·m²	B330 family envelope	Approx. 6.1 kg
B420P	MPL-B420P	5000 RPM	1.9 kW	4.74 N·m	13.5 N·m	0.00026 kg·m²	Approx. 46 × 23 × 28 cm	Approx. 6.4 kg
B430P	MPL-B430P	5000 RPM	2.2 kW	6.55 N·m	19.8 N·m	0.00038 kg·m²	Approx. 46 × 23 × 28 cm	Approx. 9.2 kg

The B320P is positioned between the smaller B310P and the larger B330P in terms of published power and torque.

The B320P provides 1.5 kW of rated output, 3.05 N·m continuous stall torque, and 7.91 N·m peak stall torque.

These figures make the B320P suitable for many general-purpose industrial servo axes while retaining the relatively low rotor inertia associated with the MPL family.

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22. RK74AA Versus RK72AA

Parameter	MPL-B320P-RK74AA	MPL-B320P-RK72AA
Feedback	Resolver	Resolver
Shaft	Keyless	Keyless
Rated Speed	5000 RPM	5000 RPM
Rated Power	1.5 kW	1.5 kW
Continuous Torque	3.05 N·m	3.05 N·m
Peak Torque	7.91 N·m	7.91 N·m
Frame	100 mm	100 mm
Stack	50.8 mm	50.8 mm
Brake	24 V DC	No brake
Connector	SpeedTEC DIN	SpeedTEC DIN
Connector	Right-angle, 180° rotatable	Right-angle, 180° rotatable
Approx. Dimensions	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg	3.7–3.9 kg

The major difference is the brake.

The RK74AA includes a 24 V DC brake, while the RK72AA is the no-brake configuration. The rest of the main B320P performance characteristics are closely related.

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23. RK74AA Versus RJ74AA

Parameter	MPL-B320P-RK74AA	MPL-B320P-RJ74AA
Feedback	Resolver	Resolver
Shaft	Keyless	Keyed
Brake	24 V DC	24 V DC
Rated Speed	5000 RPM	5000 RPM
Rated Power	1.5 kW	1.5 kW
Continuous Torque	3.05 N·m	3.05 N·m
Peak Torque	7.91 N·m	7.91 N·m
Frame	100 mm	100 mm
Stack	50.8 mm	50.8 mm
Connector	SpeedTEC DIN	SpeedTEC DIN
Approx. Dimensions	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg	Approx. 6.8 kg

The primary difference between these two models is the shaft configuration.

The RK74AA uses a keyless shaft, while the RJ74AA uses a keyed shaft.

The electrical and servo performance characteristics are closely related because both belong to the B320P 1.5 kW, 5000 RPM resolver configuration.

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24. RK74AA Versus MK74AA

Parameter	MPL-B320P-RK74AA	MPL-B320P-MK74AA
Feedback	Resolver	Multi-turn absolute encoder
Shaft	Keyless	Keyless
Brake	24 V DC	24 V DC
Rated Speed	5000 RPM	5000 RPM
Rated Power	1.5 kW	1.5 kW
Continuous Torque	3.05 N·m	3.05 N·m
Peak Torque	7.91 N·m	7.91 N·m
Frame	100 mm	100 mm
Stack	50.8 mm	50.8 mm
Connector	SpeedTEC DIN	SpeedTEC DIN
Approx. Dimensions	42.8 × 21.7 × 26.0 cm	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg	Approx. 6–7 kg

The major difference is the feedback system.

The RK74AA uses resolver feedback, while the MK74AA uses a multi-turn high-resolution absolute encoder.

This distinction can affect drive selection, feedback processing, commissioning, machine positioning strategy, and replacement compatibility.

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25. Application Selection Guide

Application Requirement	RK74AA Configuration
High-speed operation	5000 RPM
Servo positioning	Suitable
Repetitive indexing	Suitable
Closed-loop feedback	Resolver
Keyless mechanical connection	Yes
Integral holding brake	Yes
1.5 kW class motor	Yes
Continuous stall torque	3.05 N·m
Peak stall torque	7.91 N·m
Compact frame	100 mm
High-response motion	Low-inertia design
Vertical-axis holding	Brake-equipped configuration
Cable-routing flexibility	Right-angle, 180° rotatable connector
Approx. Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg

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26. Installation Considerations

The motor should be installed on a rigid mounting structure.

Correct mechanical alignment is important because servo motors can operate through rapid acceleration and deceleration cycles.

Misalignment between the motor shaft and driven equipment can increase:

• Bearing loading
• Coupling stress
• Vibration
• Mechanical noise
• Motor temperature
• Servo following error
• Mechanical wear

The keyless shaft should be connected with a properly selected coupling.

The coupling should be rated for the motor’s continuous torque, peak torque, maximum operating speed, and expected machine duty cycle.

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27. Brake Installation Considerations

The 24 V DC brake requires appropriate electrical control.

The brake should be coordinated with the servo enable and disable sequence.

For many vertical-axis applications, the brake is released when the servo drive is ready to control the motor and applied when the motor is no longer required to produce motion.

The exact brake-control sequence should follow the complete motion system design.

The brake should not be considered the only safety measure for a gravity-loaded machine.

Where personnel safety is involved, an independent machine safety system should be designed according to the applicable machinery requirements.

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28. Cable Routing

The right-angle connector provides useful flexibility, but the cable should still be installed carefully.

The cable should have adequate bend radius.

It should not be tightly wrapped around the motor connector.

It should be mechanically supported where necessary.

The cable should also be separated appropriately from sources of excessive electrical interference according to the machine’s electrical design.

A well-planned cable installation can reduce connector stress and improve long-term servo-system reliability.

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29. Servo Tuning Considerations

The motor’s low inertia can provide fast response, but the machine’s mechanical system determines the final motion characteristics.

Important factors include:

• Motor inertia
• Load inertia
• Reflected load inertia
• Gearbox ratio
• Coupling stiffness
• Mechanical resonance
• Acceleration
• Deceleration
• Positioning accuracy
• Settling time
• Machine cycle time
• Load torque
• Operating speed

The servo drive should be tuned with the actual machine load connected whenever possible.

A motor that performs well under no-load conditions can behave differently once connected to a high-inertia or mechanically flexible machine.

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30. Maintenance Considerations

Routine maintenance should focus on the motor, coupling, cables, connector, brake, and mechanical mounting system.

Recommended inspection points include:

• Motor mounting bolts
• Shaft connection
• Coupling
• Motor cable
• Feedback cable
• Connector condition
• Brake operation
• Abnormal vibration
• Abnormal noise
• Motor temperature
• Servo following error
• Positioning repeatability
• Mechanical alignment

The brake should also be monitored for correct release and holding behavior.

Because this configuration has a motor-mounted brake, the brake circuit should be included in preventive maintenance checks.

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31. Five Recommended Related Models

No.	Model	Feedback	Shaft	Brake	Power	Speed	Torque	Approx. Dimensions	Approx. Weight
1	MPL-B320P-RK72AA	Resolver	Keyless	No	1.5 kW	5000 RPM	3.05 N·m	Approx. 42.8 × 21.7 × 26.0 cm	3.7–3.9 kg
2	MPL-B320P-RJ74AA	Resolver	Keyed	24 V DC	1.5 kW	5000 RPM	3.05 N·m	Approx. 42.8 × 21.7 × 26.0 cm	6.8 kg
3	MPL-B320P-RJ72AA	Resolver	Keyed	No	1.5 kW	5000 RPM	3.05 N·m	Approx. 42.8 × 21.7 × 26.0 cm	3.85 kg
4	MPL-B320P-MK74AA	Multi-turn absolute	Keyless	24 V DC	1.5 kW	5000 RPM	3.05 N·m	Approx. 42.8 × 21.7 × 26.0 cm	6–7 kg
5	MPL-B320P-MJ74AA	Multi-turn absolute	Keyed	24 V DC	1.5 kW	5000 RPM	3.05 N·m	Approx. 42.8 × 21.7 × 26.0 cm	6–7 kg

These five models cover the principal B320P configuration changes involving shaft style, feedback technology, and brake configuration.

For an application already using the RK74AA, the RK72AA and RJ74AA are especially useful comparison models because they retain the same general B320P motor size and resolver feedback.

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32. Five Same-Brand Models for Comparison

Model	Series	Rated Speed	Rated Power	Continuous Torque	Peak Torque	Feedback	Shaft	Brake	Approx. Dimensions	Approx. Weight
MPL-B310P-MJ74AA	MPL B-Series	5000 RPM	0.77 kW	1.58 N·m	3.61 N·m	Multi-turn absolute	Keyed	24 V DC	B310 family envelope	Approx. 2.7 kg
MPL-B320P-MK74AA	MPL B-Series	5000 RPM	1.5 kW	3.05 N·m	7.91 N·m	Multi-turn absolute	Keyless	24 V DC	Approx. 42.8 × 21.7 × 26.0 cm	Approx. 6–7 kg
MPL-B330P-MK74AA	MPL B-Series	5000 RPM	1.8 kW	4.18 N·m	11.1 N·m	Multi-turn absolute	Keyless	24 V DC	B330 family envelope	Approx. 6.1 kg
MPL-B420P-MJ74AA	MPL B-Series	5000 RPM	1.9 kW	4.74 N·m	13.5 N·m	Multi-turn absolute	Keyed	24 V DC	Approx. 46 × 23 × 28 cm	Approx. 6.4 kg
MPL-B430P-MJ72AA	MPL B-Series	5000 RPM	2.2 kW	6.55 N·m	19.8 N·m	Multi-turn absolute	Keyed	No brake	Approx. 46 × 23 × 28 cm	Approx. 9.2 kg

These models represent different points within the same broad servo motor family.

The B310P is a lower-power configuration, while the B330P, B420P, and B430P provide progressively higher power and torque capability.

The B320P remains a 1.5 kW, 5000 RPM configuration and is therefore useful as a reference point when comparing different motor sizes.

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33. B-Series Technical Comparison

Motor Family	Model	Rated Speed	Rated Power	Continuous Stall Torque	Peak Stall Torque	Rotor Inertia	Approx. Dimensions	Approx. Weight
B310P	MPL-B310P	5000 RPM	0.77 kW	1.58 N·m	3.61 N·m	0.000044 kg·m²	B310 family envelope	Approx. 2.4–2.7 kg
B320P	MPL-B320P	5000 RPM	1.5 kW	3.05 N·m	7.91 N·m	0.000078 kg·m²	B320 family envelope	Approx. 4.5 kg
B330P	MPL-B330P	5000 RPM	1.8 kW	4.18 N·m	11.1 N·m	0.00012 kg·m²	B330 family envelope	Approx. 6.1 kg
B420P	MPL-B420P	5000 RPM	1.9 kW	4.74 N·m	13.5 N·m	0.00026 kg·m²	Approx. 46 × 23 × 28 cm	Approx. 6.4 kg
B430P	MPL-B430P	5000 RPM	2.2 kW	6.55 N·m	19.8 N·m	0.00038 kg·m²	Approx. 46 × 23 × 28 cm	Approx. 9.2 kg

The published B-series performance data shows the B320P at 1.5 kW, 3.05 N·m continuous torque, 7.91 N·m peak torque, and approximately 0.000078 kg·m² rotor inertia.

The B330P increases the torque capability, while the B420P and B430P move into larger motor configurations.

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34. Advantages in Packaging Applications

For packaging equipment, the motor’s high-speed capability can support fast machine cycles.

The resolver provides closed-loop feedback, while the low-inertia rotor supports repeated acceleration and deceleration.

The brake can be useful when the machine contains a vertical axis or another mechanism where additional holding capability is required.

The keyless shaft can also simplify certain coupling arrangements used with rollers and rotary feed mechanisms.

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35. Advantages in Material Handling

Material-handling systems often need accurate control of speed and position.

The B320P provides a combination of speed and torque suitable for many medium-sized servo axes.

The holding brake is particularly relevant for vertical lifting or positioning systems where the load can move under gravity when motor torque is removed.

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36. Advantages in Automated Assembly

Automated assembly equipment frequently uses multiple servo axes.

The motor can provide controlled rotary motion for:

• Indexing
• Feeding
• Positioning
• Tool movement
• Rotary assembly
• Transfer systems

The 5000 RPM speed class also allows the motor to participate in relatively fast production cycles.

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37. Advantages in Machine Integration

The 100 mm frame size is useful where the machine designer needs a relatively compact motor.

The right-angle connector can be oriented to reduce interference with surrounding components.

The keyless shaft can be matched with a suitable clamp-style coupling.

The brake is integrated into the motor rather than requiring a separate motor-mounted brake assembly.

Together, these features can simplify certain machine layouts.

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38. Final Detailed Specification Table

Specification	MPL-B320P-RK74AA
Brand	Allen-Bradley
Product Series	MP-Series MPL
Series Type	Low-Inertia Servo Motor
Product Type	AC Rotary Servo Motor
Voltage Class	400 V AC
Armature Voltage	460 V
Product Rating	480 V AC
Rated Power	1.5 kW
Rated Speed	5000 RPM
Maximum Speed	5000 RPM
Continuous Stall Torque	3.05 N·m
Peak Stall Torque	7.91 N·m
Rotor Inertia	Approx. 0.000078 kg·m²
Frame Size	100 mm
Frame Class	Frame 3
Magnetic Stack Length	50.8 mm
Feedback	Resolver
Resolver Type	2-pole
Shaft	Keyless
Shaft Seal	No shaft seal
Brake	24 V DC holding brake
Connector	SpeedTEC DIN
Connector Type	Right-angle
Connector Rotation	180°
Mounting	IEC metric flange
Mounting Hole Type	Free mounting holes, Type FF
Phase	3-phase
Duty	S1
Operating Temperature Reference	Approx. 40 °C maximum
Approx. Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg
Typical Applications	Packaging, assembly, handling, indexing, positioning, automation
Shaft Configuration	Keyless
Brake Supply	24 V DC
Feedback Technology	Resolver
Motor Construction	Brushless permanent-magnet servo

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39. Product Advantages Summary

Advantage	Description
Model	MPL-B320P-RK74AA
High Speed	5000 RPM
Rated Power	1.5 kW
Continuous Torque	3.05 N·m
Peak Torque	7.91 N·m
Low Rotor Inertia	Approx. 0.000078 kg·m²
Feedback	Resolver
Shaft	Keyless
Brake	24 V DC holding brake
Connector	Right-angle SpeedTEC DIN
Connector Flexibility	180° rotatable
Frame	100 mm
Stack	50.8 mm
Mounting	IEC metric
Approx. Dimensions	42.8 × 21.7 × 26.0 cm
Approx. Weight	6.8 kg
Typical Use	Industrial servo motion control

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40. Final Product Overview

The Allen-Bradley MPL-B320P-RK74AA is a 1.5 kW, 5000 RPM low-inertia AC rotary servo motor designed for industrial motion-control systems.

Its main configuration consists of a 100 mm frame, 50.8 mm magnetic stack, resolver feedback, keyless shaft, 24 V DC holding brake, and right-angle SpeedTEC DIN connector.

The motor provides approximately 3.05 N·m continuous stall torque and 7.91 N·m peak stall torque, giving it a useful combination of continuous and short-duration torque capability for automated machinery.

The low-inertia construction supports rapid speed changes and makes the motor suitable for applications with frequent acceleration and deceleration.

The resolver feedback provides the closed-loop feedback required for controlled servo operation.

The keyless shaft is an important mechanical characteristic and makes this configuration different from the keyed RJ74AA version.

The 24 V DC holding brake is another major feature of the RK74AA configuration. It can provide additional shaft-holding capability for applications such as vertical positioning systems and gravity-loaded machine axes.

The right-angle SpeedTEC DIN connector, with 180° rotational flexibility, provides additional freedom when designing cable routing around the motor.

For replacement applications, the most important points to verify are:

• Motor frame size
• Magnetic stack length
• Rated power
• Rated speed
• Continuous torque
• Peak torque
• Resolver feedback
• Keyless shaft
• Brake configuration
• Connector type
• Mounting arrangement
• Physical dimensions
• Motor weight
• Servo drive compatibility

The MPL-B320P-RK74AA therefore represents a B320P servo motor configuration intended for industrial machines requiring high-speed operation, closed-loop feedback, low-inertia response, a keyless mechanical interface, and an integrated 24 V DC holding brake.

Brand: Allen-Bradley

Series: MP-Series MPL Low-Inertia Servo Motors

Model: MPL-B320P-RK74AA

Rated Power: 1.5 kW

Rated Speed: 5000 RPM

Continuous Stall Torque: 3.05 N·m

Peak Stall Torque: 7.91 N·m

Feedback: Resolver

Shaft: Keyless

Brake: 24 V DC Holding Brake

Frame Size: 100 mm

Magnetic Stack: 50.8 mm

Approximate Dimensions: 42.8 × 21.7 × 26.0 cm

Approximate Weight: 6.8 kg

The combination of these specifications makes the MPL-B320P-RK74AA suitable for a broad range of industrial servo applications where controlled motion, high rotational speed, repeatable positioning, mechanical integration, and shaft-holding capability are required.