Hardware Comparison: MPL Servo Motor Selection Guide

Motion control sits at the heart of most manufacturing and warehousing applications.  With accurate motion control, system designers can create closed loop, efficient systems that optimize performance across a wide range of industries.  One common requirement for many systems is for low inertia servo motors.

Depending on the final product or application, low inertia servo motors are used in a variety of applications.  These applications range from packaging and converting where consistent, high speed high torque requirements drive the value of the system.  They are also used for electronics assembly, as well as in big ticket items such as automotive and metal forming where consistent performance and reliability are key.

The Value of Low Inertia Motors

Simply stated, low inertia motors are small and have a small spindle inertia.  In high volume environments when the motor is operated almost continuously, a low inertia motor will impart both low inertia and heat to the system.  In systems that have high reciprocating motion, a low inertia motor will put less stress on the system overall while completing the task and remaining reliable.

This means that for systems that require fast start and acceleration and fast stopping or positioning, low inertia motors are a good solution.  This includes both light and medium sized loads as well as those requiring superior fast braking or positioning.

Allen Bradley Low Inertia MPL Motors

The Allen Bradley MPL low inertia servo motor line is ideal for the applications mentioned above.  The MP series is compact yet delivers a wide torque range making it suitable for motion systems requiring high-performance and superior reliability.  The high torque to size ration means that size considerations are reduced in control system design. 

The MPL series is commonly used with Allen Bradley’s Kinetix servo drives.  This combination of MPL low inertia motors and Kinetix drives is part of Allen Bradley’s Kinetix Integrated Motion solutions and is part of Allen Bradley’s and Rockwell’s Rockwell Integrated Architecture.  By combining the MPL servo motors with Kinetix controllers, control systems can leverage integration with Logix PLCs, advanced networks such as NetLinx and the RSLogix 5000 series software for a comprehensive control system.

Allen Bradley MPL Low Inertia Motor Common Features

Allen Bradley’s low inertia MPL series motors offer several advantages regardless of frame size and voltage.  These include:

  • Winding – The MPL series has an innovative and unique winding technology.  This means that it can deliver as much as 40% more torque than other low inertia servo motors. 
  • Thermal Management – The MPL series also excels at thermal management.  With advanced winding insulation, thew MPL series can deliver higher performance by effectively managing heat transfer.
  • Rare Earth Magnets – Rare earth magnets are extremely strong alloys of rare-earth elements.  They are the strongest magnets made and their use in MPL series low inertia motors allow for faster acceleration compared to standard magnet servo motors.
  • Cabling – Allen Bradley’s MPL series low inertia motors allow the use of a single cable group to help ease of installation and lower cost for cabling.
  • Braking – All MPL motors come with integrated 24V braking onboard.

MPL Series Encoders

In today’s control systems, a motor’s utility goes beyond just its speed, torque and inertia.  It must also provide reliability for encoders to function properly.  The MPL series comes with high-performance encoders to allow a broader use across applications.  This integration with encoding can take the form of single-turn or multi-turn resolution.

 The MPL series offers a wide range of counts per revolution beginning with lower end applications that deliver up to 260,000 counts per revolution (CPR).  Higher end versions can deliver up to 2 million CPR.  This means that regardless the system, both performance and precise control are possible with MPL series motors.  Allen Bradley MPL series motors also allow absolute position feedback for 4096 turns.

MPL Series motors are also “smart” motors, fitting well into today’s connected factory and IoT enabled operations.  Each motor has embedded capability to retain its motor identity in the case of power loss.  And when the system is started, MPL low inertia motors can self-identify to the system for reduced start up time.

Voltage Differences

The Allen Bradley MPL series low inertia servo motors come in two different armature voltage.  Each voltage has several size ranges to choose from depending on application.

230 Volts

MPL low inertia motors with a 230-volt armature voltage come in five frame sizes:

  • 15 – 2.48 in.
  • 2 – 1.95 in.
  • 3 – 3.94 in.
  • 4 – 4.53 in.
  • 45 – 5.12 in.

230 Volt speed ratings include:

  • 1500 RPM
  • 2800 RPM
  • 3000 RPM
  • 3500 RPM
  • 5000 RPM
  • 6000 RPM
  • 7000 RPM
  • 8000 RPM

For feedback, the 230-volt line can include either a 2000-line incremental encoder, a multi-turn high-resolution encoder for applications requiring absolute feedback, or a single-turn high-resolution encoder.

Enclosures for the 230 voltage lines include both keyed and keyless shaft extensions.  And the 230-volt versions can have either 24V DC braking or no braking.

One of the key features of the MPL series low inertia motors is its torque to size ration and low inertia.  The ability to deliver torque over a very wide and controlled range means motion system designers can rely on the MPL series’ having a solution for almost any need.  Torque ranges on the 230-volt versions range from as low as 2.3 lb./in. of continuous stall and 6.8 lb./in. peak stall torque at 8000 RPM models to as high as 237 continuous stall and 540 peak stall torque on 3000 RPM versions.

460 Volts

MPL low inertia motors with a 460-volt armature voltage come in seven frame sizes.  These include:

  • 15 – 2.48 in.
  • 2 – 2.95 in.
  • 3 – 3.94 in.
  • 4 – 4.53 in.
  • 45 – 5.12 in.
  • 5 – 6.50 in.
  • 6 – 8.48 in.

Speed ratings for 460-volt MPL motors include:

  • 1000 RPM
  • 1200 RPM
  • 1500 RPM
  • 2000 RPM
  • 3000 RPM
  • 3500 RPM
  • 3800 RPM
  • 4000 RPM
  • 5000 RPM
  • 6000 RPM
  • 7000 RPM
  • 8000 RPM

Like the 230-volt line, the 460-volt MPL low inertia motors include either a 2000-line incremental encoder, a multi-turn high-resolution encoder for applications requiring absolute feedback, or a single-turn high-resolution encoder.  The 460s also allow both keyed and keyless shaft extensions and either a 24V DC braking or no braking option.

The 460-volt line also delivers on the same wide range torque options as the 230-volt series.  This ranges from 2.3 lb./in. continuous stall torque and 6.8 lb./in. peak stall torque on 8000 RPM motors to as high as 1250 lb./in. continuous stall torque and 2100 lb./in. peak stall torque on versions at 2750 RPM

Special Control Systems

Many industries have special requirements due to sanitary regulations or compliance requirements.  For these special industries, Allen Bradley has designed low inertia MP series motors to meet these rigid requirements. 

MP Series Food Grade Motors – These motors are used in food packaging, filling, handling, and sealing within the meat, poultry and dairy industries.  They are constructed with industry compliant components that deliver the same performance as regular MPL motors while allowing the motors to be used near food.  These motors only range to 5000 RPMs but can still offer high-resolution feedback.

These added features include:

  • Use of special food-grade grease.
    • Use of stainless steel for both shaft and fasteners.
    • Food grade casing epoxy
    • High resistance to cleaning compounds.

Stainless Steel Motors – Also used predominantly in the food industry, stainless steel motors are used in food and other environments where hygienic needs dictate frequent washing via pressure washing or caustic washdowns.  These industries include applications such as food prep, food cutting, enclosed equipment, life sciences and other food related consumer products.  Strengthened features for stainless steel motors include:

  • Motors are sealed and leak tested.
    • High resistance to caustic washdowns
    • Enclosed stainless-steel exterior

Low inertia MPL series motors from Allen Bradley can deliver superior performance over a wide torque range depending on the application.  The MPL series is an integral part of control systems that use the Allen Bradley Kinetix servo drive family and can deliver high-performance within the most demanding environments.

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