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20P21AD086RA0NNN PowerFlex DC Drive

Product Parameters, Introduction, Applications, Advantages, Series Information and Related Model Recommendations

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1. Product Overview

The 20P21AD086RA0NNN is a high-capacity industrial DC drive designed for controlling DC motors in demanding industrial machinery.

It belongs to the PowerFlex DC series and is rated at 86 A, with a normal-duty motor rating of 50 HP / 37 kW at the 460 VAC input class.

The drive uses a three-phase, 480 VAC-class, six-pulse input and provides two-quadrant, non-regenerative operation.

The unit is designed for applications where an existing DC motor needs controlled starting, acceleration, deceleration, speed regulation and current control.

The product is particularly relevant to DC motor retrofit projects. It can be used in machinery where replacing the complete motor and mechanical transmission would be considerably more complicated than modernizing the drive system.

The standard configuration is an IP20, NEMA/UL Type Open drive with a Frame A construction, conformal coating, blank front plate, user documentation and no communication module in the base configuration.

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2. Brand and Series

Item	Specification
Model	20P21AD086RA0NNN
Brand	Allen-Bradley
Product family	PowerFlex
Series	PowerFlex DC
Product type	Industrial DC Drive
Drive category	Digital DC Drive
Motor type	DC Motor
Current class	86 A
Motor rating	50 HP
Metric motor rating	37 kW
Input voltage class	460/480 VAC
Input phase	Three-phase
Input topology	Six-pulse
Operating mode	Two-quadrant
Regeneration	Non-regenerative
Frame	Frame A
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Cooling	Air cooled
Front interface	Blank plate
HIM	Not included
Communication module	Not included
Field supply	Single-phase regulated
Feedback capability	DC tachometer / encoder capable
Conformal coating	Yes

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3. Main Technical Parameters

Parameter	Specification
Model	20P21AD086RA0NNN
Series	PowerFlex DC
Product type	Digital DC Drive
Input voltage	380–480 VAC class
Nominal input	460/480 VAC
Input frequency	50/60 Hz
Input phase	Three-phase
Input type	Six-pulse
Output current	86 A
Normal-duty motor rating	50 HP
Metric motor rating	37 kW
Motor operation	Two-quadrant
Regenerative operation	No
Field supply	Single-phase regulated
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Frame size	Frame A
Cooling method	Air cooled
Front display	Blank plate
HIM	Not included
Communication module	Not included
Feedback	Tachometer / encoder capable
Conformal coating	Yes
Installation	Panel / cabinet mounted
Height	Approx. 279 mm
Width	Approx. 381 mm
Depth	Approx. 279 mm
Dimensions	Approx. 279 × 381 × 279 mm
Weight (kg)	Approx. 14.5 kg

The dimensional figure corresponds to approximately 11.0 × 15.0 × 11.0 in.

The weight should be treated as an approximate unit weight for planning purposes. Actual shipping weight can be higher because of packaging and associated materials.

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4. Product Introduction

The 20P21AD086RA0NNN is designed for industrial DC motor control where a relatively high armature current is required.

With an 86 A output rating, it sits above the 73 A model and below the 100 A configuration within the same general non-regenerative PowerFlex DC range.

Its 50 HP / 37 kW rating makes it suitable for larger industrial machinery.

The basic purpose of the drive is to take incoming three-phase AC power and provide controlled electrical power to the DC motor.

Instead of allowing the motor to operate simply at full power whenever it is energized, the drive provides a controlled interface between the electrical supply and the motor.

This allows the machine designer to control important operating characteristics such as:

• Motor starting
• Acceleration
• Deceleration
• Speed
• Armature current
• Torque-producing current
• Field operation
• Motor protection
• Speed feedback
• Machine interlocking
• Fault handling

The result is a controlled motor system that can be integrated into a larger industrial automation process.

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5. 86 A Current Rating

The most important electrical characteristic of the 20P21AD086RA0NNN is its 86 A output-current rating.

This rating makes the drive suitable for DC motors in the approximately 50 HP / 37 kW range under the appropriate operating conditions.

The current rating is important because the armature current of a DC motor is directly associated with its torque-producing capability.

For that reason, the drive should not be selected by horsepower alone.

The motor nameplate should be checked for:

• Armature voltage
• Armature current
• Field voltage
• Field current
• Base speed
• Maximum speed
• Motor duty
• Feedback requirements
• Cooling requirements

The 86 A rating provides a useful margin above the 73 A model for applications where additional current capacity is required.

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6. 50 HP / 37 kW Motor Class

The drive is associated with a 50 HP / 37 kW normal-duty motor rating.

This places the product in a substantial industrial power range.

Typical machinery at this power level may include:

• Heavy conveyors
• Large material feeders
• Industrial rollers
• Paper-processing equipment
• Printing machinery
• Textile machinery
• Production lines
• Material-handling systems
• Process machinery
• Large machine tools
• Industrial winding equipment

The exact suitability depends on the motor’s electrical characteristics and the mechanical load.

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7. Input Voltage

The drive is designed for the 380–480 VAC three-phase class, with 460/480 VAC being the principal nominal input range.

Three-phase industrial power is commonly used for medium- and high-power equipment.

Before installation, the electrical system should be checked for:

• Nominal voltage
• Frequency
• Phase balance
• Grounding
• Available fault current
• Disconnect requirements
• Branch circuit protection
• Power wiring
• Cabinet temperature
• Drive cooling

A correct electrical installation is essential for safe and reliable operation.

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8. Six-Pulse Input

The 20P21AD086RA0NNN uses a six-pulse input topology.

This is a conventional architecture for industrial DC drives.

The three-phase AC input is converted into controlled DC power for the motor armature.

The six-pulse configuration is particularly relevant when modernizing older DC drive systems because it provides a familiar electrical architecture for conventional DC motor applications.

When replacing an older drive, engineers should compare:

• AC input voltage
• AC input phase
• Motor armature voltage
• Motor armature current
• Field voltage
• Field current
• Feedback device
• Control signals
• Braking arrangement
• Motor speed
• Machine inertia

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9. Two-Quadrant Operation

The 20P21AD086RA0NNN is a two-quadrant drive.

Two-quadrant operation is suitable for applications where the motor primarily operates in the motoring direction and the machine does not require continuous regenerative operation.

Typical applications include:

• Conveyors
• Feeders
• Rollers
• Fans
• Pumps
• Material transport systems
• Processing equipment
• Production machinery

The two-quadrant configuration can provide a practical and economical solution for conventional DC motor applications.

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10. Non-Regenerative Operation

The drive is a non-regenerative configuration.

This means that it is not designed to continuously return regenerative energy from the motor to the AC supply.

This is important when evaluating machines with substantial mechanical inertia.

During deceleration, a high-inertia machine can cause the motor to act as a generator.

Applications that require careful regenerative analysis include:

• Winders
• Unwinders
• Hoists
• Cranes
• Large rollers
• High-inertia conveyors
• Rapid stopping systems
• Frequent reversing systems
• Downhill conveyors
• Machines with frequent braking

If the machine regularly produces significant regenerative energy, a regenerative drive configuration should be considered.

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11. Regulated Field Supply

The product includes a single-phase regulated field supply.

The field circuit is a critical part of a conventional DC motor.

The field establishes the magnetic flux necessary for proper motor operation.

The field supply must therefore be matched to the motor.

Important parameters include:

Field Parameter	Design Consideration
Field voltage	Must match motor requirements
Field current	Must remain within motor rating
Field polarity	Verify during installation
Field wiring	Verify terminal arrangement
Field-loss protection	Verify configuration
Field weakening	Verify motor capability
Maximum speed	Must remain within motor limits
Motor cooling	Must be adequate

Incorrect field settings can cause unstable motor operation, overspeed conditions or motor damage.

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12. Speed Feedback

The PowerFlex DC family provides feedback capabilities suitable for applications requiring accurate speed regulation.

Feedback may be provided by:

• DC tachometer
• Encoder

Depending on the machine configuration.

The drive can compare the commanded speed with the measured motor speed.

If the load increases and the motor begins to slow down, the control system can respond by adjusting the motor operating point.

This is especially valuable for:

• Printing machinery
• Paper machinery
• Textile machinery
• Roller systems
• Feed systems
• Precision conveyors
• Production lines
• Material processing equipment

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13. Control and Integration

The standard configuration does not include a communication module.

This does not prevent the drive from being integrated into an industrial control system.

Hardwired control can be used for functions such as:

• Start
• Stop
• Enable
• Reset
• Direction
• Speed reference
• Fault status
• Drive ready
• Running status

Analog references can also be used where required.

This makes the drive suitable for retrofit projects where an existing PLC or machine controller is already installed.

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14. Blank Front Plate

The standard configuration has a blank front plate rather than a local HIM.

This arrangement is useful when the machine has a separate operator interface.

For example, the drive may be installed inside a cabinet while the operator controls the machine through:

• HMI
• PLC
• Pushbuttons
• Selector switches
• Remote control panel
• External speed reference

This keeps the drive itself relatively simple and allows the machine’s main control system to handle the operator interface.

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15. Communication Options

The base configuration does not include a communication module.

This can be useful for installations that primarily use hardwired I/O.

For larger automation systems, an appropriate communication option can be selected separately when required.

Potential integration functions include:

• Start/stop commands
• Speed references
• Fault monitoring
• Actual speed monitoring
• Current monitoring
• Drive status
• Alarm monitoring
• Process interlocking

The appropriate communication architecture depends on the PLC and automation platform used by the machine.

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16. IP20 Enclosure

The drive uses an IP20, NEMA/UL Type Open enclosure.

This means it should normally be installed inside a suitable electrical cabinet or protected enclosure.

It is not intended to be directly exposed to:

• Water
• Washdown spray
• Condensation
• Conductive dust
• Corrosive contamination
• Heavy airborne particles
• Outdoor weather

The cabinet should provide suitable environmental protection and sufficient cooling.

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17. Conformal Coating

The product includes conformal coating.

Conformal coating provides additional protection to electronic components against certain industrial environmental conditions.

This can be beneficial in applications where the electronics may encounter:

• Humidity
• Dust
• Airborne contaminants
• Industrial atmosphere
• Production particles

However, conformal coating does not turn an IP20 drive into a waterproof product.

The drive still needs a properly designed enclosure.

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18. Frame A Construction

The 20P21AD086RA0NNN uses Frame A construction.

Approximate mechanical dimensions are:

279 mm high

381 mm wide

279 mm deep

The approximate unit weight is:

14.5 kg

This makes the product relatively compact considering its 50 HP / 37 kW power class.

The cabinet should nevertheless provide additional clearance for:

• Power cables
• Control wiring
• Feedback wiring
• Air circulation
• Maintenance
• Terminal access
• Cable bending radius
• Cooling

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19. Dimensions and Weight

Mechanical Parameter	Approximate Specification
Model	20P21AD086RA0NNN
Frame	Frame A
Height	279 mm
Width	381 mm
Depth	279 mm
Dimensions	279 × 381 × 279 mm
Weight (kg)	Approx. 14.5 kg
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Cooling	Air cooled
Installation	Panel / cabinet
Mounting environment	Protected industrial enclosure

For final cabinet fabrication, the mechanical drawing for the specific unit should be used to confirm mounting-hole locations, clearances and cable-entry requirements.

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20. Main Product Applications

20.1 Heavy Conveyor Systems

The 86 A capacity makes this drive suitable for larger conveyor applications.

Potential applications include:

• Heavy belt conveyors
• Roller conveyors
• Transfer conveyors
• Bulk material conveyors
• Production conveyors
• Assembly conveyors
• Packaging conveyors
• Material transport systems

Controlled acceleration can help reduce mechanical shock to belts, couplings and gearboxes.

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21. Industrial Roller Systems

Industrial rollers often require stable speed and reliable torque control.

Potential applications include:

• Process rollers
• Feed rollers
• Paper rollers
• Printing rollers
• Textile rollers
• Material transport rollers
• Production rollers

Feedback can be particularly valuable when the machine must maintain consistent speed despite changing load conditions.

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22. Paper and Material Processing

The drive is well suited for compatible DC motor applications in paper and material-processing machinery.

Potential applications include:

• Feed rollers
• Process rollers
• Paper transport
• Material handling
• Production equipment
• Auxiliary drives
• Processing systems

The ability to maintain controlled speed can be important when the material must move through several processing stages at a consistent rate.

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23. Printing Machinery

Printing equipment can require stable roller speed and predictable acceleration.

Potential applications include:

• Printing rollers
• Feed mechanisms
• Paper transport
• Material handling
• Processing rollers
• Auxiliary machinery

A feedback-equipped configuration may be especially useful where speed accuracy affects print quality or material registration.

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24. Textile Machinery

The product can be applied to suitable DC motors used in textile production.

Possible uses include:

• Textile rollers
• Feed mechanisms
• Material transport
• Processing equipment
• Production machinery
• Specialized textile systems

However, winding and unwinding applications should be evaluated carefully because they can generate significant regenerative energy.

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25. Material-Handling Equipment

The 86 A capacity provides a useful power level for heavier material-handling equipment.

Potential applications include:

• Heavy feeders
• Transfer systems
• Conveyors
• Rollers
• Production transport
• Industrial handling equipment
• Sorting systems
• Heavy production lines

The higher current rating provides additional capacity compared with smaller PowerFlex DC configurations.

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26. Machine Tools

The drive can also be considered for compatible industrial machine tools.

Possible applications include:

• Grinding equipment
• Feed systems
• Cutting equipment
• Processing machines
• Specialized machine tools
• Production equipment

When accurate speed regulation is required, feedback should be evaluated as part of the complete motor-control design.

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27. Product Advantages

27.1 High 86 A Current Capacity

The 86 A output rating is the key advantage of the model.

It allows the drive to control larger DC motors than the 45 A, 52 A and 73 A configurations.

This makes it a practical choice for machines requiring approximately 50 HP of DC motor power.

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27.2 50 HP / 37 kW Capacity

The 50 HP / 37 kW rating places the drive in a substantial industrial power category.

It can provide a good balance between motor capacity and physical drive size for medium-heavy machinery.

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27.3 480 VAC-Class Input

The 480 VAC three-phase input class is suitable for many industrial power systems.

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27.4 Two-Quadrant Architecture

Two-quadrant operation is appropriate for conventional motoring applications where regenerative operation is not continuously required.

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27.5 Regulated Field Supply

The regulated field supply provides controlled field operation for compatible DC motors.

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27.6 Feedback Capability

Tachometer and encoder capability makes the drive suitable for applications where speed stability is important.

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27.7 Flexible I/O

The drive can be integrated into machine-control systems using digital and analog signals.

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27.8 Compact Frame A Construction

The Frame A design offers a relatively compact physical package for a 50 HP DC drive.

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27.9 Conformal Coating

Conformal coating provides additional protection for electronic components in suitable industrial environments.

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27.10 Retrofit Potential

The product is particularly attractive when an existing DC motor remains mechanically sound.

A drive retrofit can potentially preserve:

• Existing motor
• Gearbox
• Coupling
• Conveyor
• Rollers
• Shafts
• Bearings
• Mechanical transmission
• Existing PLC
• Existing HMI

This can significantly reduce mechanical modification during modernization.

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28. Product Advantages Summary

Feature	Practical Benefit
86 A output	Suitable for high-current DC motors
50 HP / 37 kW	Suitable for heavy industrial machinery
480 VAC-class input	Compatible with common industrial power systems
Three-phase input	Suitable for industrial installations
Six-pulse topology	Established DC drive architecture
Two-quadrant operation	Suitable for conventional motoring applications
Non-regenerative design	Appropriate where regeneration is not required
Regulated field	Controlled DC motor field operation
Encoder/tachometer capability	Improved speed regulation
Flexible control I/O	Easy integration into machine systems
Frame A	Compact mechanical configuration
IP20	Suitable for cabinet installation
Conformal coating	Additional electronics protection
Blank front plate	Suitable for external operator control

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29. Five Same-Series or Closely Related Models

The following models are useful when comparing the 20P21AD086RA0NNN with nearby ratings and functional alternatives.

Model	Series	Current	Motor Rating	Approx. Power	Input	Operation	Regenerative	Frame
20P21AD052RA0NNN	PowerFlex DC	52 A	30 HP	22 kW	460/480 VAC	Two-quadrant	No	A
20P21AD073RA0NNN	PowerFlex DC	73 A	40 HP	30 kW	460/480 VAC	Two-quadrant	No	A
20P21AD086RA0NNN	PowerFlex DC	86 A	50 HP	37 kW	460/480 VAC	Two-quadrant	No	A
20P21AD100RA0NNN	PowerFlex DC	100 A	60 HP	45 kW	460/480 VAC	Two-quadrant	No	A
20P41AD086RA0NNN	PowerFlex DC	86 A	50 HP class	37 kW	460/480 VAC	Regenerative	Yes	A

The first four models form a useful progression through the standard non-regenerative range.

The 20P41AD086RA0NNN is particularly relevant when the machine requires regenerative operation.

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30. Related Model 1 — 20P21AD052RA0NNN

The 20P21AD052RA0NNN is a lower-capacity model rated at approximately:

52 A

and:

30 HP / 22 kW

It is appropriate for smaller DC motors where the 86 A capacity would be unnecessary.

Typical applications include:

• Medium conveyors
• Feeders
• Rollers
• Production machinery
• Printing equipment
• Textile equipment

Its main advantage is more appropriately sized capacity for smaller motors.

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31. Related Model 2 — 20P21AD073RA0NNN

The 20P21AD073RA0NNN is rated at approximately:

73 A

and:

40 HP / 30 kW

It sits directly below the 86 A model.

This makes it a natural comparison when the motor is close to the 40 HP range.

The 73 A model can be selected when 86 A capacity is unnecessary.

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32. Related Model 3 — 20P21AD100RA0NNN

The 20P21AD100RA0NNN provides approximately:

100 A

and:

60 HP / 45 kW

It is the logical higher-capacity choice when the motor requires more than the 86 A rating.

Potential applications include:

• Heavy conveyors
• Large rollers
• Heavy feeders
• Processing equipment
• Large material-handling systems
• High-load production machinery

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33. Related Model 4 — 20P41AD086RA0NNN

The 20P41AD086RA0NNN is a regenerative version associated with the same 86 A / 50 HP class.

Its main difference is its ability to handle regenerative operation.

It should be considered for:

• Winders
• Unwinders
• Hoists
• Cranes
• High-inertia machines
• Frequent braking
• Rapid deceleration
• Four-quadrant applications

This model is functionally more appropriate when the load frequently returns energy to the drive.

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34. Related Model 5 — 20P21AD129RA0NNN

The 20P21AD129RA0NNN is a substantially higher-capacity model.

It is rated at approximately:

129 A

and:

75 HP / 56 kW

It can be considered for applications where the 86 A and 100 A configurations do not provide enough current capacity.

Typical applications include:

• Large conveyors
• Large processing machinery
• Heavy rollers
• Large feeders
• Industrial production lines
• Higher-power DC motor systems

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35. Five Popular Models from the Same Brand Portfolio

For broader product comparison, the following models provide useful reference points.

Model	Product Family	Type	Voltage Class	Current / Power	Main Application	Approx. Dimensions	Weight (kg)
20P21AD073RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	73 A / 40 HP	Industrial DC machinery	Approx. 279 × 381 × 279 mm	Approx. 14.5
20P21AD086RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	86 A / 50 HP	Heavy DC machinery	Approx. 279 × 381 × 279 mm	Approx. 14.5
20P21AD100RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	100 A / 60 HP	Larger DC machinery	Frame-dependent	Higher
20P21AD129RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	129 A / 75 HP	High-power DC machinery	Larger frame	Higher
25B-D017N104	PowerFlex 525	AC Drive	380–480 VAC	17 A class	General AC motor control	Compact frame	Approx. 2–3

The last model is an AC drive rather than a direct replacement for the 20P21AD086RA0NNN.

It is better viewed as an alternative for a complete DC-to-AC modernization project.

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36. Capacity Comparison

Model	Current	Normal-Duty HP	Normal-Duty kW	General Application
20P21AD019RA0NNN	19 A	10 HP	7.5 kW	Smaller DC machinery
20P21AD027RA0NNN	27 A	15 HP	11 kW	Medium machinery
20P21AD035RA0NNN	35 A	20 HP	15 kW	Medium industrial machinery
20P21AD045RA0NNN	45 A	25 HP	18.5 kW	Medium-heavy machinery
20P21AD052RA0NNN	52 A	30 HP	22 kW	Larger industrial machinery
20P21AD073RA0NNN	73 A	40 HP	30 kW	Heavy industrial machinery
20P21AD086RA0NNN	86 A	50 HP	37 kW	Heavy industrial machinery
20P21AD100RA0NNN	100 A	60 HP	45 kW	Large DC machinery
20P21AD129RA0NNN	129 A	75 HP	56 kW	Larger DC machinery

This progression makes the 20P21AD086RA0NNN an attractive choice for applications that need more capacity than a 73 A drive but do not require the larger 100 A or 129 A configurations.

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37. Detailed Parameter Table

Category	Parameter	Specification
Product	Model	20P21AD086RA0NNN
Product	Brand	Allen-Bradley
Product	Series	PowerFlex DC
Product	Product type	Digital DC Drive
Electrical	Input voltage	380–480 VAC class
Electrical	Nominal input	460/480 VAC
Electrical	Input frequency	50/60 Hz
Electrical	Input phase	Three-phase
Electrical	Input topology	Six-pulse
Electrical	Output current	86 A
Electrical	Normal-duty power	37 kW
Electrical	Normal-duty horsepower	50 HP
Electrical	Operation	Two-quadrant
Electrical	Regenerative	No
Field	Field supply	Single-phase regulated
Enclosure	IP rating	IP20
Enclosure	Enclosure type	NEMA/UL Type Open
Mechanical	Frame	Frame A
Mechanical	Cooling	Air cooled
Mechanical	Height	279 mm
Mechanical	Width	381 mm
Mechanical	Depth	279 mm
Mechanical	Dimensions	279 × 381 × 279 mm
Mechanical	Weight (kg)	Approx. 14.5 kg
Interface	Front interface	Blank plate
Interface	HIM	Not included
Communication	Communication module	Not included
Feedback	DC tachometer	Supported
Feedback	Encoder	Supported
Protection	Conformal coating	Yes
Installation	Mounting	Panel / cabinet
Application	Motor type	DC motor
Application	Typical loads	Conveyors, rollers, feeders, processing machinery
Application	Retrofit	Existing DC motor systems

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38. Typical Applications and Suitability

Application	Suitability	Main Reason
Heavy conveyor	Excellent	High current and controlled acceleration
Industrial roller	Excellent	Stable speed and torque control
Material feeder	Excellent	Good current capacity
Paper processing	Very suitable	Speed regulation and DC motor compatibility
Printing equipment	Very suitable	Feedback-based speed control
Textile machinery	Suitable	Controlled motor operation
Material handling	Very suitable	50 HP-class motor support
Production lines	Suitable	Flexible control integration
Machine tools	Suitable	Speed and current control
Winder	Application dependent	Regeneration must be evaluated
Unwinder	Application dependent	Regenerative energy may be significant
Hoist	Application dependent	Braking and regeneration require careful evaluation
Crane	Application dependent	Four-quadrant requirements may apply
Rapid reversing machine	Application dependent	Regenerative energy must be evaluated

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39. Speed Regulation

One of the major reasons to use a digital DC drive is controlled motor speed.

In a basic application, the machine can provide a speed command through an analog reference or another control signal.

In a feedback application, a tachometer or encoder can provide actual motor speed.

The drive then compares:

Commanded Speed

with:

Actual Speed

and adjusts motor operation to reduce the difference.

This can be especially valuable in machines where a small speed variation can affect the final product.

Examples include:

• Printing
• Paper handling
• Textile production
• Material processing
• Roller systems
• Precision feeding

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40. Acceleration Control

A 50 HP DC motor can produce considerable torque.

Starting such a motor without controlled acceleration can place stress on:

• Couplings
• Gearboxes
• Belts
• Shafts
• Bearings
• Rollers
• Conveyor components

Controlled acceleration allows the machine to reach operating speed in a more predictable manner.

This can improve mechanical smoothness and reduce unnecessary shock.

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41. Deceleration Control

Deceleration is particularly important for a non-regenerative drive.

When a motor slows down, stored mechanical energy can flow back toward the electrical system.

The application engineer should therefore evaluate:

• Load inertia
• Motor speed
• Deceleration time
• Number of stops per hour
• Reversing frequency
• Load torque
• Braking method
• Regenerative energy

If substantial energy is returned during normal operation, a regenerative configuration may be more appropriate.

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42. Torque Capability

DC motor torque is closely related to armature current.

The 86 A capacity therefore provides substantial torque capability when paired with a suitable 50 HP DC motor.

Potential high-torque applications include:

• Heavy conveyors
• Feeders
• Rollers
• Material-handling systems
• Processing equipment
• Production machinery

Current limits should always be configured according to the actual motor rating.

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43. Retrofit Advantages

A major benefit of using a PowerFlex DC drive is the possibility of modernizing the control electronics while retaining an existing DC motor.

A machine that has been operating for many years may have a mechanically sound motor and transmission.

Replacing only the drive may be considerably simpler than replacing the complete machine drive train.

Potentially retained components include:

• DC motor
• Gearbox
• Coupling
• Conveyor
• Roller
• Shaft
• Bearings
• Mechanical transmission
• Machine frame
• Existing PLC
• Existing operator controls

This can reduce both mechanical modification and project downtime.

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44. Cabinet Design

The approximate drive dimensions are:

279 mm × 381 mm × 279 mm

The approximate unit weight is:

14.5 kg

These dimensions should not be interpreted as the total cabinet space required.

Additional space is needed for:

• Power wiring
• Control wiring
• Feedback wiring
• Cable bending radius
• Cooling
• Maintenance
• Terminal access
• Grounding
• Service clearance

The cabinet designer should also consider heat generated by other components installed near the drive.

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45. Thermal Management

An 86 A DC drive produces heat during operation.

The cabinet design should consider:

• Ambient temperature
• Internal cabinet temperature
• Airflow
• Fan operation
• Heat from adjacent equipment
• Ventilation
• Heat exchanger requirements
• Dust accumulation
• Cooling clearances

Maintaining suitable operating temperature is important for long-term reliability.

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46. Maintenance

Routine maintenance should include inspection of:

• Cooling fan
• Ventilation openings
• Power terminals
• Control terminals
• Feedback wiring
• Field connections
• Armature connections
• Ground connections
• Cabinet cleanliness
• Motor brushes
• Motor commutator
• Motor bearings
• Fault history

The DC motor should be treated as part of the complete drive system.

A new drive cannot compensate for severe mechanical or electrical deterioration in an old DC motor.

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47. DC Motor Inspection

Before installing the 20P21AD086RA0NNN, the existing DC motor should be inspected.

Recommended checks include:

Motor Area	Inspection
Armature	Voltage and current rating
Field	Voltage and current rating
Brushes	Wear and seating
Commutator	Surface condition
Bearings	Noise and mechanical play
Insulation	Insulation resistance
Cooling	Fan and ventilation
Speed	Base and maximum speed
Feedback	Tachometer or encoder condition
Mechanical coupling	Alignment
Vibration	Excessive vibration
Temperature	Operating temperature

This type of inspection can prevent a drive replacement from being blamed for problems that actually originate in the motor or mechanical system.

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48. When to Select the 86 A Model

The 20P21AD086RA0NNN is a strong candidate when:

• The motor is around 50 HP.
• The motor is around 37 kW.
• The required armature current is within the 86 A range.
• The plant uses a compatible 460/480 VAC three-phase supply.
• The application primarily operates in the motoring direction.
• Continuous regeneration is not required.
• The existing DC motor is mechanically healthy.
• Speed regulation is required.
• The machine needs controlled acceleration.
• A cabinet installation is available.

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49. When a Different Model Should Be Considered

A different drive may be preferable when:

• The motor requires substantially less than 86 A.
• The motor requires more than 86 A.
• The motor voltage is not compatible.
• The field voltage is incompatible.
• The machine requires continuous regeneration.
• Four-quadrant operation is required.
• The machine has very high inertia.
• Frequent rapid braking is required.
• The project is a complete DC-to-AC modernization.

For smaller motors, the 52 A or 73 A models may be more appropriately sized.

For larger motors, the 100 A or 129 A configurations can be considered.

For regenerative applications, the corresponding regenerative configuration should be evaluated.

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50. Recommended Model Selection Table

Application Requirement	Recommended Model	Current	Power	Main Reason
Medium DC motor	20P21AD052RA0NNN	52 A	30 HP / 22 kW	Smaller capacity
40 HP-class motor	20P21AD073RA0NNN	73 A	40 HP / 30 kW	Intermediate capacity
50 HP-class motor	20P21AD086RA0NNN	86 A	50 HP / 37 kW	Direct application fit
60 HP-class motor	20P21AD100RA0NNN	100 A	60 HP / 45 kW	Higher current
75 HP-class motor	20P21AD129RA0NNN	129 A	75 HP / 56 kW	Larger DC motor
50 HP regenerative application	20P41AD086RA0NNN	86 A	50 HP class	Regenerative operation

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51. Overall Technical Advantages

The 20P21AD086RA0NNN has several practical strengths.

First, the 86 A current rating makes it suitable for larger DC motors without moving immediately into the much larger drive frames.

Second, the 50 HP / 37 kW rating gives it a useful position in the industrial power range.

Third, the drive provides two-quadrant operation, which is suitable for a large number of conventional motoring applications.

Fourth, the regulated field supply makes it suitable for compatible DC motors requiring controlled field operation.

Fifth, the ability to use tachometer or encoder feedback provides better speed regulation for demanding processes.

Sixth, the IP20 open enclosure is well suited to cabinet-based industrial installations.

Finally, the product can be valuable in retrofit projects because the existing DC motor and mechanical equipment may be retained.

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52. Five Same-Series / Related Recommendations

No.	Model	Current	Motor Rating	Voltage	Operating Mode	Typical Use	Approx. Weight
1	20P21AD052RA0NNN	52 A	30 HP / 22 kW	460/480 VAC	Two-quadrant	Medium DC machinery	Approx. 14 kg class
2	20P21AD073RA0NNN	73 A	40 HP / 30 kW	460/480 VAC	Two-quadrant	Heavy conveyors and rollers	Approx. 14 kg class
3	20P21AD100RA0NNN	100 A	60 HP / 45 kW	460/480 VAC	Two-quadrant	Larger industrial machinery	Higher
4	20P41AD086RA0NNN	86 A	50 HP / 37 kW class	460/480 VAC	Regenerative	High-inertia / braking applications	Similar frame class
5	20P21AD129RA0NNN	129 A	75 HP / 56 kW	460/480 VAC	Two-quadrant	Larger DC machinery	Larger frame

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53. Five Broader Popular Models

No.	Model	Family	Type	Voltage	Current / Power	Application	Dimensions	Weight (kg)
1	20P21AD073RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	73 A / 40 HP	Industrial DC machinery	Approx. 279 × 381 × 279 mm	Approx. 14.5
2	20P21AD086RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	86 A / 50 HP	Heavy DC machinery	Approx. 279 × 381 × 279 mm	Approx. 14.5
3	20P21AD100RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	100 A / 60 HP	Large DC machinery	Frame-dependent	Higher
4	20P21AD129RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	129 A / 75 HP	High-power DC machinery	Larger frame	Higher
5	25B-D017N104	PowerFlex 525	AC Drive	380–480 VAC	17 A class	General AC motor control	Compact	Approx. 2–3

The fifth model is from a different drive technology family.

It is included because it is a commonly considered alternative when an industrial machine is being modernized from a DC motor system to an AC motor system.

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54. Detailed Comparison of the Main Related Models

Model	Current	HP	kW	Input	Quadrant	Regenerative	Frame	Dimensions	Weight (kg)
20P21AD052RA0NNN	52 A	30	22	460/480 VAC	Two	No	A	Approx. 279 × 381 × 279 mm class	Approx. 14
20P21AD073RA0NNN	73 A	40	30	460/480 VAC	Two	No	A	Approx. 279 × 381 × 279 mm class	Approx. 14
20P21AD086RA0NNN	86 A	50	37	460/480 VAC	Two	No	A	Approx. 279 × 381 × 279 mm	Approx. 14.5
20P21AD100RA0NNN	100 A	60	45	460/480 VAC	Two	No	A	Frame-dependent	Higher
20P21AD129RA0NNN	129 A	75	56	460/480 VAC	Two	No	A/B transition class	Larger	Higher
20P41AD086RA0NNN	86 A	50	37	460/480 VAC	Regenerative	Yes	A	Similar class	Approx. 14.5+

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55. Product Configuration Breakdown

The model number can be understood as a specific configuration within the PowerFlex DC product family.

The important practical characteristics are:

20P — PowerFlex DC product family.

21 — Non-regenerative drive configuration.

AD086 — 86 A class.

RA0NNN — Standard configuration options associated with the particular catalog arrangement.

The complete catalog number must be treated as one product identifier when ordering or replacing equipment.

For replacement work, it is important not to assume that two drives with similar current ratings are automatically interchangeable.

The complete catalog number, motor characteristics, voltage, field configuration, feedback arrangement and machine requirements should all be compared.

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56. Installation Environment

The drive is intended for installation in a controlled industrial environment.

The surrounding cabinet should protect the equipment from:

• Water
• Excessive humidity
• Conductive contamination
• Heavy dust
• Corrosive gases
• Excessive vibration
• Direct mechanical impact

The drive’s cooling airflow should not be blocked.

Power cables should be routed carefully to minimize unnecessary electrical interference with low-level control and feedback wiring.

Feedback cables should be installed according to the requirements of the feedback device and overall machine-control design.

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57. Maintenance Strategy

For long-term operation, maintenance should be divided into electrical, mechanical and environmental checks.

Electrical Maintenance

Check:

• Power connections
• Armature connections
• Field connections
• Grounding
• Control wiring
• Feedback wiring
• Terminal tightness

Mechanical Maintenance

Check:

• Motor bearings
• Couplings
• Gearboxes
• Shafts
• Rollers
• Belts
• Mechanical alignment

Environmental Maintenance

Check:

• Cabinet cleanliness
• Cooling fan
• Airflow
• Temperature
• Dust
• Moisture

A preventive maintenance program can reduce unexpected downtime.

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58. Important Selection Factors

When selecting the 20P21AD086RA0NNN, the following factors should be reviewed together rather than individually.

Selection Factor	Why It Matters
Motor current	Must be compatible with the 86 A drive rating
Motor voltage	Must match the drive operating range
Motor horsepower	Approximately 50 HP class
Field voltage	Must match motor field requirements
Field current	Must remain within motor limits
Motor speed	Base and maximum speeds must be compatible
Load inertia	Determines acceleration and braking requirements
Regeneration	Determines whether a non-regenerative drive is appropriate
Feedback	Determines speed-control capability
Environment	Determines cabinet and cooling requirements
Duty cycle	Determines thermal loading
Braking	Must be evaluated for high-inertia loads
PLC integration	Determines control and communication requirements

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59. Overall Assessment

The 20P21AD086RA0NNN is a high-capacity DC drive intended for demanding industrial applications.

Its 86 A output rating and 50 HP / 37 kW normal-duty rating make it particularly suitable for larger DC motor systems.

Compared with the 73 A model, it provides additional current capacity for applications where the motor approaches the 50 HP range.

Compared with the 100 A model, it provides a somewhat smaller capacity while still supporting a substantial 37 kW motor.

Its two-quadrant non-regenerative architecture is well suited to conventional motor-driven loads.

Its regulated field supply supports compatible DC motors, while feedback capability provides a path to improved speed regulation.

The Frame A construction and approximately 279 × 381 × 279 mm physical size provide a relatively compact solution for this power category.

The approximately 14.5 kg unit weight also makes the drive manageable for panel installation while still requiring appropriate cabinet mounting and handling procedures.

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60. Final Specification Summary

Parameter	Final Specification
Model	20P21AD086RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Product type	Industrial DC Drive
Input voltage	380–480 VAC class
Nominal input	460/480 VAC
Input phase	Three-phase
Input frequency	50/60 Hz
Input topology	Six-pulse
Output current	86 A
Normal-duty motor rating	50 HP
Metric motor rating	37 kW
Operation	Two-quadrant
Regenerative	No
Field supply	Single-phase regulated
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Frame	Frame A
Cooling	Air cooled
Front interface	Blank plate
HIM	Not included
Communication module	Not included
Feedback	DC tachometer / encoder capable
Conformal coating	Yes
Height	279 mm
Width	381 mm
Depth	279 mm
Dimensions	279 × 381 × 279 mm
Weight (kg)	Approx. 14.5 kg
Main application	Industrial DC motor control
Typical loads	Conveyors, rollers, feeders, processing machinery
Lower-capacity alternative	20P21AD073RA0NNN
Higher-capacity alternative	20P21AD100RA0NNN
Regenerative alternative	20P41AD086RA0NNN
Larger alternative	20P21AD129RA0NNN

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61. Conclusion

The 20P21AD086RA0NNN is a 50 HP / 37 kW, 86 A industrial DC drive designed for demanding DC motor applications.

Its position in the PowerFlex DC range makes it a useful choice for machinery that requires more capacity than a 73 A drive but does not yet require a 100 A or larger configuration.

The drive is particularly suitable for heavy conveyors, industrial rollers, feeders, paper-processing equipment, printing machinery, textile machinery, material-handling systems and other production equipment using compatible DC motors.

Its two-quadrant configuration is well suited to conventional motoring applications.

For machines with high inertia, frequent braking or significant energy return during deceleration, the non-regenerative configuration should be evaluated carefully.

The product’s regulated field supply, feedback capability, flexible control architecture, IP20 enclosure and conformal coating provide a practical combination for industrial applications.

For retrofit projects, another important advantage is the possibility of retaining an existing DC motor and mechanical system.

This can reduce the scope of mechanical modifications and allow an older machine to receive a modernized drive-control system without completely redesigning the machine.

In practical terms, the 20P21AD086RA0NNN is best suited to applications where the following combination is required:

480 VAC-class three-phase input + 86 A DC output + 50 HP / 37 kW motor + two-quadrant operation + cabinet installation + controlled DC motor speed and torque.

When selecting this drive, the final decision should always be based on the actual motor nameplate and machine operating conditions.

Particular attention should be given to armature voltage, armature current, field voltage, field current, base speed, maximum speed, feedback, duty cycle, inertia and braking requirements.

For a conventional 50 HP DC motor system, however, the 20P21AD086RA0NNN represents a strong and appropriately sized option within the PowerFlex DC product range.