Company Information
E-mail		[email protected]
Mobile		+8615980777398
Whatsapp		+8615980777398
WeChat		15980777398

MPL-B520K-SK74AA Servo Motor – Complete Product Introduction and Technical Guide

1. Product Overview

The MPL-B520K-SK74AA is a high-speed, low-inertia rotary servo motor designed for precision motion-control applications where fast acceleration, accurate positioning, stable speed control, and reliable mechanical holding are important.

It belongs to the MPL Series low-inertia brushless servo motor family and uses a 165 mm frame with a 50.8 mm magnetic stack. The motor is designed for a 460 V class / 480 V AC servo system and has a rated maximum speed of 4000 rpm. Its standard configuration combines a single-turn high-resolution encoder, a keyless shaft extension, a right-angle rotatable SpeedTEC DIN connector, and an integrated 24 V DC holding brake.

The SK74AA configuration is particularly useful when the machine requires both a keyless mechanical connection and a motor-mounted holding brake. This makes it different from the SK72AA version, which uses the same general motor platform but does not include the brake.

The motor is intended for applications where the servo axis must repeatedly start, stop, accelerate, decelerate, and hold its position without excessive rotor inertia. Typical examples include CNC equipment, machine tools, packaging machinery, indexing systems, precision assembly equipment, automated production lines, and other high-cycle motion-control machines.

---

2. Brand and Product Series

Item	Specification
Brand	Allen-Bradley
Product Series	MPL Series
Product Family	MP-Series Low-Inertia Servo Motors
Motor Type	Brushless AC Rotary Servo Motor
Product Type	Rotary Servo Motor
Model	MPL-B520K-SK74AA
Voltage Class	460 V class / 480 V AC
Frame Size	165 mm
Magnetic Stack	50.8 mm
Speed Class	4000 rpm
Feedback	Single-turn high-resolution encoder
Shaft	Keyless shaft extension
Brake	24 V DC holding brake
Connector	SpeedTEC DIN, right-angle
Mounting	IEC metric, free mounting holes, Type FF

The MPL Series is positioned around low-inertia servo performance. The B520K motor class is one of the 4000 rpm motor configurations within this family, providing a combination of relatively high rotational speed, moderate continuous torque, and low rotor inertia.

---

3. Model Number Explanation

The model number MPL-B520K-SK74AA contains several pieces of configuration information.

Model Code	General Meaning
MPL	MPL low-inertia brushless servo motor family
B	460 V class motor family
5	165 mm frame-size class
20	50.8 mm magnetic-stack class
K	4000 rpm speed class
S	Single-turn high-resolution feedback
K	Keyless shaft configuration
7	SpeedTEC DIN right-angle connector configuration
4	24 V DC holding brake
AA	Standard configuration suffix

The most important configuration characteristics are therefore easy to summarize: 4000 rpm + single-turn feedback + keyless shaft + right-angle connector + 24 V DC brake.

This combination makes the SK74AA configuration particularly useful when the machine builder needs a compact high-speed servo motor with an integrated holding function while avoiding a keyed shaft connection.

---

4. Main Technical Specifications

The core B520K motor data identifies a rated output of approximately 3.5 kW, a continuous stall torque of 10.7 N·m, a peak stall torque of approximately 23.2 N·m, and a rotor inertia of approximately 0.000783 kg·m². The motor’s maximum operating speed is 4000 rpm.

Parameter	MPL-B520K-SK74AA
Model	MPL-B520K-SK74AA
Brand	Allen-Bradley
Series	MPL Series
Motor Type	Low-inertia brushless AC servo motor
Rated Power	Approx. 3.5 kW
Motor Voltage	460 V class
System Voltage	480 V AC
Rated Speed Class	4000 rpm
Maximum Speed	4000 rpm
Continuous Stall Torque	10.7 N·m
Peak Stall Torque	Approx. 23.2 N·m
Rotor Inertia	Approx. 0.000783 kg·m²
Frame Size	165 mm
Magnetic Stack Length	50.8 mm
Feedback	Single-turn high-resolution encoder
Encoder Type	Absolute single-turn, high-resolution
Shaft	Keyless shaft extension
Brake	24 V DC holding brake
Connector	SpeedTEC DIN
Connector Position	Right-angle
Connector Rotation	180° rotatable
Mounting Standard	IEC metric
Mounting Hole Style	Free mounting holes, Type FF
Shaft Key	None
Shaft Seal	None
Motor Construction	Low-inertia brushless
Approx. Motor Weight	About 13.1 kg for the brake-equipped configuration
Frame Width Class	165 mm frame
Stack Dimension	50.8 mm
Overall Envelope	Verify against the specific mechanical drawing

The published product data confirms the 165 mm frame, 50.8 mm stack, 4000 rpm speed class, keyless shaft, single-turn encoder, right-angle connector, and 24 V DC brake configuration.

---

5. Dimensions and Mechanical Characteristics

The most important mechanical dimensions for selection are the 165 mm frame size and 50.8 mm magnetic-stack length.

The 165 mm frame places this motor in a relatively substantial industrial servo-motor size class, while the 50.8 mm stack corresponds to the B520K configuration.

Mechanical Parameter	Value
Model	MPL-B520K-SK74AA
Frame Size	165 mm
Frame Size, Imperial	Approx. 6.50 in
Magnetic Stack Length	50.8 mm
Stack Length, Imperial	Approx. 2.0 in
Mounting System	IEC metric
Mounting Hole Type	Free mounting holes / Type FF
Shaft Type	Keyless
Shaft Key	No
Shaft Seal	No
Connector	SpeedTEC DIN
Connector Style	Right-angle
Connector Rotation	180°
Brake	Integrated 24 V DC
Approx. Weight	13.1 kg
Full Overall Length	Verify from mechanical drawing
Full Housing Width	Verify from mechanical drawing
Full Housing Height	Verify from mechanical drawing

For engineering drawings, enclosure design, mounting-plate preparation, shaft-coupling clearance, and cable-clearance calculations, the complete mechanical drawing should be used rather than estimating the overall motor envelope from the frame and stack dimensions alone.

---

6. Weight

Weight is particularly important when this motor is installed on a moving machine axis, robotic mechanism, vertical axis, linear slide, or compact machine frame.

A published listing for the exact SK74AA configuration gives a weight of approximately 13.13 kg, including the brake-equipped configuration.

The general B520K motor family documentation lists approximately 9.8 kg for the base B520K motor configuration, while brake-equipped configurations can be heavier. Therefore, for mechanical load calculations involving the exact MPL-B520K-SK74AA, approximately 13.1 kg is a practical catalog reference, but the final machine design should use the exact product drawing and nameplate data.

---

7. Electrical Characteristics

The MPL-B520K motor class is designed around a 460 V line-to-line motor voltage and a 480 V AC system environment. The published motor data gives approximately 3.5 kW of rated output, with a continuous stall torque of 10.7 N·m.

Electrical Parameter	Specification
Model	MPL-B520K-SK74AA
Motor Voltage	460 V
System Voltage	480 V AC
Rated Output	Approx. 3.5 kW
Motor Poles	8
Operating Speed	Up to 4000 rpm
Continuous Stall Torque	10.7 N·m
Peak Stall Torque	Approx. 23.2 N·m
Continuous Stall Current	Approx. 11.5 A
Peak Stall Current	Approx. 33.0 A
Rotor Inertia	Approx. 0.000783 kg·m²
Brake Voltage	24 V DC

The actual drive-side current, operating point, acceleration profile, load inertia, and duty cycle must be evaluated together when selecting the matching servo drive.

---

8. Low-Inertia Motor Design

One of the most important characteristics of the MPL-B520K platform is its low-inertia rotor design.

Low rotor inertia means the servo system does not have to spend as much torque accelerating and decelerating the motor rotor itself. This can be especially valuable in machines with frequent reversals, rapid indexing, short positioning cycles, and high-speed start-stop operation.

The published rotor inertia for the B520K motor class is approximately 0.000783 kg·m².

This characteristic can improve the dynamic behavior of a properly tuned servo system. In practical machinery, the benefit is often most noticeable when the load itself is not excessively large and the machine requires repeated rapid changes in velocity.

---

9. 4000 RPM High-Speed Performance

The B520K configuration is a 4000 rpm servo motor class.

A 4000 rpm maximum-speed capability gives machine designers additional flexibility when selecting transmission ratios. Instead of relying entirely on a large mechanical reduction ratio, the motor can provide useful mechanical speed directly at the servo shaft.

This can be advantageous in applications such as high-speed rotary indexing, spindle-like auxiliary axes, winding mechanisms, cutting mechanisms, belt-driven axes, and compact rotary positioning systems.

The motor class is specified at approximately 3.5 kW with 10.7 N·m continuous stall torque and approximately 23.2 N·m peak stall torque.

---

10. Single-Turn High-Resolution Encoder

The S configuration in the model number identifies the single-turn high-resolution feedback configuration.

The feedback system is designed to provide accurate rotor-position information to the servo control system. Published technical listings identify this configuration as an absolute single-turn encoder, with one listing specifying a 1024 Sin/Cos absolute single-turn encoder using Hiperface protocol.

For normal servo applications, this type of feedback supports accurate velocity regulation, positioning, acceleration control, deceleration control, and repeatable motion.

The single-turn arrangement is particularly appropriate when the machine’s position requirements are managed within one mechanical revolution of the feedback reference or when the machine’s overall position-management strategy does not require motor-side multi-turn position memory.

---

11. Keyless Shaft Configuration

The K shaft designation indicates the keyless shaft configuration.

A keyless shaft can be useful when the mechanical transmission is designed around a clamp-style coupling, shrink disc, clamping hub, or other precision shaft-locking method.

Compared with a traditional keyed connection, a properly designed keyless coupling can provide excellent concentricity and can simplify certain precision transmission arrangements.

Mechanical Feature	MPL-B520K-SK74AA
Model	MPL-B520K-SK74AA
Shaft Type	Keyless
Shaft Key	None
Coupling Style	Compatible with suitable keyless/clamping coupling systems
Main Benefit	Flexible precision coupling arrangement
Typical Use	Servo couplings, precision rotary transmission, compact machine axes
Important Consideration	Coupling must be correctly sized and torqued

A keyless shaft does not mean that the motor can be connected directly to any arbitrary coupling. The coupling must be correctly matched to the shaft diameter, torque, speed, allowable radial load, allowable axial load, and installation requirements.

---

12. Integrated 24 V DC Holding Brake

The SK74AA suffix is particularly important because this configuration includes a 24 V DC holding brake.

The brake is useful when the motor must hold a load when servo torque is removed. This is especially important for vertical axes, lifting mechanisms, indexing mechanisms, and machines where the axis must remain mechanically held during a stop or power-off condition.

The product description specifically identifies the brake as a 24 V DC brake.

The brake should primarily be treated as a holding device rather than as the normal method for stopping a high-speed moving load. The servo drive should normally control deceleration, while the brake is applied according to the machine’s safety and motion-control sequence.

---

13. SpeedTEC DIN Right-Angle Connector

The motor uses a SpeedTEC DIN connector in a right-angle arrangement, with a 180° rotatable connector configuration.

This is valuable in machines where cable routing is restricted.

A right-angle connector can help keep motor cables closer to the machine structure rather than extending straight out from the rear of the motor. The 180° rotation capability also provides additional flexibility when routing cables around machine frames, guards, slides, or other mechanical structures.

This can make a significant difference in compact machine layouts where connector orientation is otherwise difficult to accommodate.

---

14. IEC Metric Mounting

The MPL-B520K-SK74AA uses an IEC metric mounting arrangement with free mounting holes, identified as Type FF in the product description.

This makes the motor suitable for conventional industrial machine mounting plates and mechanical structures designed around metric dimensions.

When replacing an existing servo motor, the mounting pattern, shaft geometry, shaft projection, coupling position, motor body clearance, connector clearance, and brake clearance should all be checked rather than relying only on the nominal frame size.

---

15. Main Product Advantages

15.1 High-Speed Operation

The 4000 rpm speed class is one of the main advantages of the B520K configuration.

High motor speed can reduce the need for excessive mechanical gearing and can support short machine cycles.

For high-speed rotary applications, this can help increase productivity while maintaining controlled servo positioning.

---

15.2 Low Rotor Inertia

The low-inertia design is another major advantage.

With approximately 0.000783 kg·m² rotor inertia, the B520K motor is designed for responsive servo dynamics.

This is useful when the machine frequently changes speed or direction.

Typical examples include indexing tables, pick-and-place mechanisms, cutting axes, packaging machines, and high-cycle assembly systems.

---

15.3 Integrated Holding Brake

The SK74AA configuration includes a 24 V DC holding brake.

This provides an important advantage for applications where the motor must maintain its mechanical position when servo torque is removed.

Vertical axes are a particularly important example because gravity can cause an uncontrolled downward movement if no suitable holding mechanism is provided.

---

15.4 Keyless Shaft

The keyless shaft arrangement provides more flexibility for precision coupling arrangements.

This can be useful when the machine builder prefers clamp-style couplings and wants to minimize the mechanical complications associated with a conventional keyway.

---

15.5 Single-Turn High-Resolution Feedback

The single-turn high-resolution feedback configuration supports precise servo control.

It is well suited to applications that require accurate positioning and repeatability without requiring a multi-turn feedback architecture.

---

15.6 Compact Cable Arrangement

The right-angle rotatable connector is useful in compact machinery.

It can make cable routing easier and reduce the amount of space needed behind the motor.

---

16. Typical Applications

CNC Machines

The motor can be used for CNC-related motion axes where rapid acceleration, precise positioning, and repeatable operation are required.

The 4000 rpm speed capability is useful for fast auxiliary axes and rotary mechanisms.

---

Packaging Machinery

Packaging machines frequently perform repetitive movements with short cycle times.

The low-inertia characteristics and high-speed operation of the B520K platform are well suited to these conditions.

Typical applications include indexing, cutting, sealing, feeding, labeling, and synchronized rotary mechanisms.

---

Material Handling Equipment

The motor can be applied to automated conveyors, indexing systems, transfer mechanisms, and positioning units.

The integrated brake can be particularly useful when an axis needs to remain stationary during a machine stop.

---

Vertical Motion Axes

The holding brake makes the SK74AA configuration particularly attractive for certain vertical-axis applications.

Examples include vertical slides, lifting mechanisms, Z-axis arrangements, and other gravity-loaded mechanisms.

Proper safety engineering and brake sizing are still required.

---

Rotary Indexing

Rotary indexing equipment often requires repeated acceleration and deceleration.

The low-inertia rotor can support responsive motion, while the high-resolution feedback allows the control system to maintain accurate angular positioning.

---

Automated Assembly Equipment

Automated assembly systems often require many fast and repeatable movements.

The motor can be used for rotary positioning, feeder mechanisms, indexing systems, tooling axes, and other servo-controlled movements.

---

Robotics and Automated Handling

The motor can also be considered for robotic or automated handling mechanisms where the mechanical load, motor inertia, speed, and torque requirements are appropriate.

For robot joints, the complete inertia ratio and mechanical transmission should be evaluated carefully.

---

17. Recommended Same-Series or Closely Related Models

The following models are useful when comparing configurations within the B520K family or moving to a higher-torque member of the same MPL family.

The B520K family shares the same general 165 mm frame and 50.8 mm stack platform, while different suffixes change feedback, shaft, and brake configurations. The B540K moves to a longer 101.6 mm stack and provides substantially higher torque and power.

Model	Speed	Continuous Torque	Peak Torque	Power	Feedback	Shaft	Brake	Frame / Stack	Weight
MPL-B520K-SJ72AA	4000 rpm	10.7 N·m	23.2 N·m	3.5 kW	Single-turn	Keyed	No	165 / 50.8 mm	Approx. 9.8 kg
MPL-B520K-SJ74AA	4000 rpm	10.7 N·m	23.2 N·m	3.5 kW	Single-turn	Keyed	24 V DC	165 / 50.8 mm	Approx. 13 kg class
MPL-B520K-SK72AA	4000 rpm	10.7 N·m	23.2 N·m	3.5 kW	Single-turn	Keyless	No	165 / 50.8 mm	Approx. 9.8 kg class
MPL-B520K-MK74AA	4000 rpm	10.7 N·m	23.2 N·m	3.5 kW	Multi-turn	Keyless	24 V DC	165 / 50.8 mm	Approx. 13–14 kg
MPL-B540K-SK74AA	4000 rpm	19.4 N·m	48.6 N·m	5.4 kW	Single-turn	Keyless	24 V DC	165 / 101.6 mm	Higher than B520K

The first three alternatives are particularly useful when the main requirement is changing the shaft or brake configuration without changing the fundamental B520K performance class.

The B540K-SK74AA is the more appropriate direction when the application requires significantly more torque while retaining a high-speed, keyless-shaft, brake-equipped arrangement. The B540K family is rated at approximately 5.4 kW, 19.4 N·m continuous torque, and 48.6 N·m peak torque.

---

18. Five Popular Models for Broader Brand Comparison

The following models provide a useful comparison across different motor sizes and performance classes.

Model	Speed	Continuous Torque	Peak Torque	Rated Power	Feedback / Configuration	Frame / Stack	Approx. Weight
MPL-B4530K	4000 rpm	8.25 N·m	20.3 N·m	2.6 kW	Low-inertia servo	Smaller frame class	Approx. 11.0 kg*
MPL-B520K	4000 rpm	10.7 N·m	23.2 N·m	3.5 kW	Low-inertia servo	165 / 50.8 mm	9.8 kg
MPL-B540K	4000 rpm	19.4 N·m	48.6 N·m	5.4 kW	Low-inertia servo	165 / 101.6 mm	Approx. 15 kg class
MPL-B560F	3000 rpm	26.8 N·m	67.8 N·m	5.5 kW	Low-inertia servo	165 / 152.4 mm	20.2 kg
MPL-B580F	3000 rpm	34.0 N·m	87.0 N·m	7.1 kW	Low-inertia servo	165 / 203.2 mm	25.4 kg

*Weight values can vary with feedback, shaft, and brake configuration. The exact configuration should be checked before mechanical design.

The B520K is positioned between smaller MPL motors and higher-torque B540K/B560F/B580F motors. Published family data lists 3.5 kW for B520K, 5.4 kW for B540K, 5.5 kW for B560F, and 7.1 kW for B580F.

---

19. B520K vs. B540K

The B540K is an important upgrade option.

Parameter	MPL-B520K-SK74AA	MPL-B540K-SK74AA
Speed	4000 rpm	4000 rpm
Continuous Torque	10.7 N·m	19.4 N·m
Peak Torque	Approx. 23.2 N·m	Approx. 48.6 N·m
Power	3.5 kW	5.4 kW
Frame	165 mm	165 mm
Stack	50.8 mm	101.6 mm
Feedback	Single-turn	Single-turn
Shaft	Keyless	Keyless
Brake	24 V DC	24 V DC
Connector	Right-angle SpeedTEC DIN	Right-angle SpeedTEC DIN

The B540K provides substantially greater torque while maintaining the same 4000 rpm speed class.

Therefore, the B540K is a natural upgrade when the B520K has adequate speed but insufficient torque.

---

20. B520K vs. B560F

The B560F moves the application toward higher torque.

Parameter	MPL-B520K-SK74AA	MPL-B560F
Speed	4000 rpm	3000 rpm
Continuous Torque	10.7 N·m	26.8 N·m
Peak Torque	23.2 N·m	67.8 N·m
Power	3.5 kW	5.5 kW
Rotor Inertia	0.000783 kg·m²	0.00213 kg·m²
Stack	50.8 mm	152.4 mm
Approx. Weight	13.1 kg class with brake	20.2 kg family value

The B560F is better suited to applications where torque is more important than the 4000 rpm capability of the B520K.

---

21. Application Selection Guide

Application Requirement	Recommended Direction
High speed with moderate torque	MPL-B520K-SK74AA
Keyless shaft required	MPL-B520K-SK74AA
Motor holding brake required	MPL-B520K-SK74AA
Single-turn feedback required	MPL-B520K-SK74AA
Same performance without brake	MPL-B520K-SK72AA
Keyed shaft required	MPL-B520K-SJ74AA
Multi-turn feedback required	B520K-MK/MJ configurations
More continuous torque required	B540K family
Much higher torque required	B560F / B580F family
Lower-speed, higher-torque application	B540D / B560F family

---

22. Installation Considerations

Mechanical installation should begin with verification of the 165 mm frame size and 50.8 mm stack configuration.

The motor should be mounted on a rigid, properly aligned machine structure.

Shaft alignment is especially important when using a precision keyless coupling. Excessive radial or angular misalignment can increase bearing loads and reduce the service life of the motor and coupling.

The brake wiring should be designed according to the machine’s control sequence.

The brake should not normally be used as the primary means of repeatedly stopping a high-speed rotating load.

---

23. Cable and Connector Considerations

The right-angle SpeedTEC DIN connector provides useful installation flexibility.

Before finalizing the machine layout, sufficient clearance should be provided around the connector for cable installation, connector engagement, service access, and cable bending radius.

The 180° rotatable connector arrangement can be particularly helpful when the motor is installed close to a machine frame or protective enclosure.

Cable routing should also keep motor power and feedback cables away from sources of excessive electrical noise whenever practical.

---

24. Brake Application Considerations

The 24 V DC brake is one of the most important reasons to select the SK74AA rather than the SK72AA configuration.

The brake can be valuable for:

• Vertical servo axes
• Gravity-loaded mechanisms
• Lift mechanisms
• Z-axis machine tools
• Position-holding mechanisms
• Indexing systems requiring mechanical holding
• Equipment requiring a defined holding state during shutdown

The brake must nevertheless be correctly sized for the actual static load and safety requirements of the machine.

---

25. Maintenance Considerations

Routine maintenance should focus on the mechanical and electrical condition of the entire servo axis rather than the motor alone.

Important inspection points include:

• Motor mounting bolts
• Shaft coupling condition
• Coupling alignment
• Cable and connector condition
• Brake operation
• Feedback signal stability
• Abnormal vibration
• Bearing noise
• Excessive temperature
• Unusual acceleration or deceleration behavior
• Servo following error
• Mechanical backlash

A change in servo behavior should not automatically be attributed to the motor. Couplings, bearings, machine mechanics, drive tuning, cables, feedback devices, and load conditions can all influence servo performance.

---

26. Replacement and Substitution

When replacing an existing B520K servo motor, the model number should be compared character by character.

The difference between SK72AA and SK74AA, for example, is highly important because the SK74AA version includes a 24 V DC brake.

Similarly, the difference between SJ74AA and SK74AA concerns the shaft configuration.

Configuration	Shaft	Brake	Feedback
MPL-B520K-SJ72AA	Keyed	No	Single-turn
MPL-B520K-SJ74AA	Keyed	24 V DC	Single-turn
MPL-B520K-SK72AA	Keyless	No	Single-turn
MPL-B520K-SK74AA	Keyless	24 V DC	Single-turn
MPL-B520K-MK74AA	Keyless	24 V DC	Multi-turn

This is why replacing a servo motor solely according to frame size and power rating can be risky.

The feedback type, shaft arrangement, brake, connector arrangement, and mechanical dimensions must all be checked.

---

27. Why Choose MPL-B520K-SK74AA?

The MPL-B520K-SK74AA is a strong choice when an application needs the following combination:

3.5 kW class + 4000 rpm + low inertia + single-turn high-resolution feedback + keyless shaft + 24 V DC holding brake.

This combination is particularly useful for high-cycle automation machinery.

It offers a good balance between speed, torque, mechanical compactness, and motion-control performance.

The integrated brake adds an additional level of mechanical holding capability, while the keyless shaft provides flexibility for precision coupling arrangements.

---

28. Product Advantages at a Glance

Advantage	Description
High Speed	Up to 4000 rpm
Low Inertia	Designed for fast acceleration and deceleration
3.5 kW Class Output	Suitable for many medium-duty servo axes
10.7 N·m Continuous Torque	Useful continuous torque capability
23.2 N·m Peak Torque	Supports short-duration dynamic loads
Single-Turn Feedback	Accurate rotor-position feedback
Keyless Shaft	Flexible coupling arrangements
24 V DC Brake	Mechanical holding capability
Right-Angle Connector	Easier cable routing in compact machines
180° Rotatable Connector	Additional installation flexibility
165 mm Frame	Standardized industrial mechanical class
50.8 mm Stack	Compact B520K stack configuration
IEC Metric Mounting	Convenient machine integration

---

29. Final Technical Specification Table

Category	Specification
Model	MPL-B520K-SK74AA
Brand	Allen-Bradley
Series	MPL Series
Product Family	MP-Series Low-Inertia Brushless Servo Motors
Motor Type	Rotary AC Servo Motor
Voltage	460 V class
System	480 V AC
Rated Power	Approx. 3.5 kW
Maximum Speed	4000 rpm
Continuous Stall Torque	10.7 N·m
Peak Stall Torque	Approx. 23.2 N·m
Rotor Inertia	Approx. 0.000783 kg·m²
Frame Size	165 mm
Stack Length	50.8 mm
Feedback	Single-turn high-resolution encoder
Feedback Type	Absolute single-turn
Shaft	Keyless
Brake	24 V DC holding brake
Connector	SpeedTEC DIN
Connector Orientation	Right-angle
Connector Rotation	180° rotatable
Mounting	IEC metric
Mounting Holes	Free mounting holes, Type FF
Shaft Key	None
Shaft Seal	None
Approx. Weight	13.1 kg
Typical Application	Precision industrial motion control
Speed Class	High-speed servo
Motor Construction	Low-inertia brushless
Overall Dimensions	Verify exact envelope from mechanical drawing

The core B520K performance values are supported by the family technical data, while the exact SK74AA configuration is identified as the 165 mm, 50.8 mm-stack, 4000 rpm, single-turn, keyless-shaft, 24 V DC brake version.

---

30. Conclusion

The MPL-B520K-SK74AA is a high-speed, low-inertia servo motor designed for demanding industrial motion applications.

Its combination of 4000 rpm operation, approximately 3.5 kW output, 10.7 N·m continuous torque, approximately 23.2 N·m peak torque, single-turn high-resolution feedback, keyless shaft construction, right-angle rotatable connector, and 24 V DC holding brake makes it a versatile option for automated machinery.

The key advantage of this particular configuration is that it combines the dynamic characteristics of the B520K motor platform with a motor-mounted holding brake and keyless shaft.

For high-cycle equipment, the low-inertia rotor can help achieve rapid motion changes. For vertical or gravity-loaded mechanisms, the holding brake can provide useful mechanical holding capability. For precision rotary transmission, the keyless shaft can offer a flexible coupling solution.

When selecting this motor for a new machine or as a replacement, the most important items to verify are the 165 mm frame size, 50.8 mm stack length, 4000 rpm speed, 3.5 kW power class, torque requirements, single-turn feedback, keyless shaft, 24 V DC brake, connector orientation, mounting dimensions, and actual motor weight.

For applications that require more torque while maintaining a similar high-speed architecture, the B540K family is the logical next step. For applications that require substantially higher torque and can accept a lower speed, the B560F and B580F families provide larger torque capacities.

Overall, the MPL-B520K-SK74AA is best viewed as a compact high-speed servo solution for machines that need fast dynamic response together with accurate feedback, a keyless mechanical interface, and integrated holding capability.