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Allen-Bradley 20P21AE405RA0NNN PowerFlex DC Drive

1. Product Overview

The Allen-Bradley 20P21AE405RA0NNN is a high-power PowerFlex DC Drive designed for controlling large industrial DC motors.

With a rated armature current of 405 A and a normal-duty rating of approximately 300 HP / 224 kW, this model is positioned in the higher-power range of the PowerFlex DC family.

It is intended for industrial machines where a large DC motor is already installed or where precise control of a high-power DC motor is required.

The 20P21AE405RA0NNN uses a three-phase AC input and a six-pulse power-conversion configuration. It is a two-quadrant, non-regenerative DC drive, making it suitable for many applications where the motor normally operates in one direction and controlled braking is required without continuous regeneration back into the AC supply.

The model is supplied in an IP20 / NEMA/UL Type Open configuration and is intended for installation inside an appropriate electrical cabinet or enclosure.

This particular configuration includes a conformal-coated control section, a blank front cover instead of a local HIM, and no standard communication module.

The 20P21AE405RA0NNN is especially relevant to large industrial equipment such as conveyors, paper-processing machinery, printing systems, winding and unwinding machines, textile equipment, heavy material-handling systems, pumps, fans, process machinery, and other high-power applications that continue to use DC motors.

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2. Brand and Series

Parameter	Specification
Brand	Allen-Bradley
Product Family	PowerFlex
Product Series	PowerFlex DC
Product Type	Digital DC Drive
Model	20P21AE405RA0NNN
Drive Class	High-power DC drive
Normal-Duty Rating	300 HP
Approximate Power	224 kW
DC Armature Current	405 A
Input Voltage Class	500–600 VAC
Typical Input System	575 VAC
Input Phase	Three-phase
Input Type	6-pulse
Motor Operation	Two-quadrant
Regeneration	Non-regenerative
Field Supply	Single-phase regulated
Enclosure	IP20 / NEMA/UL Type Open
Frame	B
HIM Configuration	Blank Plate / No HIM
Communication Option	None-Standard
Electronics Protection	Conformal Coating

The PowerFlex DC series is specifically intended for industrial DC motor control. This differentiates it from the PowerFlex AC drive families, which are primarily intended for induction motors, permanent-magnet motors, and other AC motor applications.

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3. Main Technical Parameters

Parameter	Specification
Model	20P21AE405RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Product Type	Digital DC Drive
Rated Motor Power	300 HP
Rated Motor Power	Approximately 224 kW
Rated DC Armature Current	405 A
AC Input Voltage Class	500–600 VAC
Nominal Input	575 VAC
Input Phase	3 Phase
Input Type	6 Pulse
Motor Operation	Two Quadrant
Regenerative Operation	No
Field Supply	Single Phase Regulated
Enclosure	IP20
Enclosure Style	NEMA/UL Type Open
Frame Size	Frame B
HIM	No HIM / Blank Plate
Communication	None-Standard
Conformal Coating	Yes
Approx. AC Line Current	330.9 A
Associated Line Reactor	1321-3RB320-B
Line Reactor Class	224 kW / 300 HP
Approx. Height	311 mm
Approx. Width	388 mm
Approx. Depth	350 mm
Approx. Drive Weight	29.5 kg
Approx. Packaged Weight	31.5 kg
Installation	Cabinet / Panel
Main Application	High-power industrial DC motor control

The dimensions and weight should be regarded as approximate planning values for the applicable frame configuration. Actual supplied-unit dimensions, mounting details, accessory configuration, and shipping weight should be confirmed before final cabinet fabrication or mechanical installation.

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4. Understanding the 405 A Rating

The most important electrical characteristic of the 20P21AE405RA0NNN is its 405 A DC armature-current rating.

This is substantially higher than the 135 A and 270 A models in the same family.

A 405 A rating allows the drive to control large DC motors in the approximately 300 HP class, assuming the motor’s actual armature voltage, armature current, field requirements, duty cycle, and operating conditions are compatible.

For a DC motor, armature current is closely associated with torque production.

This makes the 405 A capacity especially useful in machinery where high torque is required during acceleration, process loading, or other demanding operating conditions.

The drive’s high current capability also means that installation details become increasingly important. Power cables, bus connections, cabinet ventilation, protective devices, line reactors, grounding, and motor connections all need to be appropriately engineered.

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5. 300 HP Motor Capacity

The 20P21AE405RA0NNN is rated for approximately 300 HP, equivalent to approximately 224 kW.

A 300 HP DC motor is normally associated with substantial industrial equipment rather than small machinery.

Typical examples include:

• Large conveyors
• Heavy material-handling systems
• Large paper machines
• Industrial winders
• Large printing presses
• Steel-processing equipment
• Textile processing machinery
• Large pumps
• Industrial fans
• Roll drives
• Process machinery
• Heavy production equipment

The 300 HP figure should be used as a starting point for drive selection rather than as the only selection criterion.

For an actual installation, the motor nameplate current should be checked first.

A motor’s rated horsepower alone does not tell the complete story because two motors with the same horsepower can have different armature voltages, armature currents, field currents, base speeds, and overload characteristics.

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6. 575 VAC-Class Three-Phase Input

The 20P21AE405RA0NNN belongs to the 500–600 VAC three-phase input class, commonly used on 575 VAC industrial power systems.

This makes it suitable for industrial facilities with high-power three-phase distribution systems.

The incoming AC power is converted by the drive into controlled DC power for the motor armature.

The overall electrical process can be represented as:

Three-phase AC supply

↓

Input protection

↓

Six-pulse power conversion

↓

Controlled DC armature output

↓

DC motor

At the same time, the drive provides the appropriate field-supply function for the motor field circuit.

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7. Six-Pulse Input Configuration

The 20P21AE405RA0NNN uses a 6-pulse input.

Six-pulse power conversion has been widely used in industrial DC drive systems for many years.

One practical benefit is that the architecture is familiar to engineers and maintenance personnel who have worked with traditional industrial DC drives.

For modernization projects, this can make the transition from an older DC controller to a newer digital DC drive easier to understand.

The six-pulse configuration is particularly common in large industrial DC drive applications.

Because this is a high-power installation, the incoming power system should still be evaluated for harmonics, short-circuit conditions, line impedance, transformer characteristics, and other power-quality considerations.

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8. Two-Quadrant Operation

The 20P21AE405RA0NNN is a two-quadrant DC drive.

This means the drive is designed primarily for applications where the motor operates in the intended direction while allowing controlled braking within the operating capabilities of a two-quadrant system.

This configuration is appropriate for many applications that do not require continuous regenerative operation.

Typical examples can include:

• Conveyors
• Fans
• Pumps
• Process rollers
• Certain winding systems
• Continuous production machinery
• One-direction material handling

For machinery that requires frequent reversal or where the load continuously drives the motor during braking, a regenerative model should be considered instead.

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9. Non-Regenerative Operation

The 20P21AE405RA0NNN is a non-regenerative model.

This is an important distinction when comparing DC drives.

A non-regenerative drive is generally suitable when the application does not require braking energy to be continuously returned to the incoming AC power system.

This type of drive can be appropriate when:

• The motor primarily runs in one direction.
• The machine does not require frequent reversing.
• Braking demand is moderate.
• The load is not continuously overhauling the motor.
• Mechanical braking can handle additional stopping requirements.
• Regenerative energy recovery is not part of the process.

When the machine requires four-quadrant operation, the corresponding regenerative PowerFlex DC model should be evaluated.

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10. Regenerative Alternative

For the same general power class, a closely related regenerative model is:

20P41AE405RA0NNN

This model belongs to the regenerative section of the PowerFlex DC family and is intended for applications where four-quadrant operation or regenerative control is required.

The basic comparison is:

Parameter	20P21AE405RA0NNN	20P41AE405RA0NNN
Motor Rating	300 HP	300 HP
Approx. Power	224 kW	224 kW
DC Current	405 A	405 A
Input Class	575 VAC	575 VAC
Input	Three-phase	Three-phase
Input Type	6-pulse	6-pulse
Operation	Two-quadrant	Four-quadrant / regenerative
Regeneration	No	Yes
Frame	B	B
Typical Application	One-direction industrial processes	Reversing / regenerative processes

The two models should not be considered interchangeable simply because their horsepower and current ratings are similar.

The braking behavior and overall application requirements must be evaluated.

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11. Field Supply

The 20P21AE405RA0NNN includes a single-phase regulated field supply.

The field circuit is an essential part of a separately excited DC motor system.

The drive controls the motor armature while also providing appropriate field control.

This can support applications where the motor requires:

• Stable field current
• Controlled field operation
• Field weakening
• Extended speed range
• Consistent motor characteristics

Field weakening can be particularly relevant in applications where the motor must operate above its base speed.

However, field weakening should only be used when the motor is designed and rated for that operating mode.

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12. IP20 / NEMA/UL Type Open Enclosure

The 20P21AE405RA0NNN is specified as IP20 / NEMA/UL Type Open.

This means the drive is normally intended to be installed within an appropriate electrical cabinet or enclosure.

The cabinet should provide suitable protection against:

• Dust
• Moisture
• Mechanical impact
• Conductive contamination
• Excessive humidity
• Process contaminants

The cabinet must also provide adequate ventilation and heat dissipation.

A 405 A DC drive can generate substantial heat, especially under high load.

For this reason, thermal design should be treated as part of the drive installation rather than as an afterthought.

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13. Conformal-Coated Electronics

This catalog configuration includes conformal coating.

Conformal coating provides an additional protective layer over electronic components and circuit assemblies.

It can be useful in industrial environments where the equipment may be exposed to:

• Humidity
• Dust
• Condensation risk
• Airborne contaminants
• Mild industrial pollutants
• Process-related particles

Conformal coating does not make the drive waterproof.

The overall enclosure must still provide the environmental protection required by the installation.

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14. No HIM / Blank Plate

The 20P21AE405RA0NNN is configured with No HIM, using a blank front plate.

This arrangement is useful for installations where the drive is not intended to be operated primarily through a local keypad.

Instead, the machine may use:

• PLC control
• Hardwired start/stop signals
• Analog speed reference
• External process controller
• Supervisory control
• Remote operator station

A blank-plate configuration can also give the control cabinet a cleaner appearance when the drive is installed behind a cabinet door or when local operator control is not required.

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15. Communication Configuration

The catalog configuration specifies None-Standard communication options.

This means the particular model configuration does not include a standard optional communication module.

The drive can still form part of an automated machine using its standard control and I/O functions or an appropriate system architecture.

When modernizing an existing machine, the control engineer should determine whether the existing PLC communicates directly with the drive or whether hardwired control signals are used.

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16. Dimensions and Weight

The physical dimensions of a high-power drive are important for cabinet design, transport, handling, and replacement work.

For the applicable Frame B configuration, practical planning values are approximately:

Mechanical Parameter	Approximate Value
Model	20P21AE405RA0NNN
Frame	B
Height	311 mm
Width	388 mm
Depth	350 mm
Drive Weight	Approximately 29.5 kg
Packaged Weight	Approximately 31.5 kg
Mounting	Panel / Cabinet
Enclosure	IP20 / NEMA/UL Type Open

These figures should be used for preliminary planning only.

Before manufacturing a replacement cabinet or mounting plate, the actual dimensional drawing for the supplied configuration should be checked.

Additional space is normally required around the drive for:

• Power cable routing
• Control wiring
• Airflow
• Terminal access
• Maintenance
• Removal and replacement
• Safe working clearance

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17. Product Introduction

The 20P21AE405RA0NNN is intended for industrial DC motor control where substantial motor power is required.

Large DC motors remain in operation in many industrial plants because of their historical use, mechanical compatibility, torque characteristics, and wide speed-control capabilities.

In many cases, the motor itself is still mechanically sound even though the original drive system has become obsolete or difficult to maintain.

A digital DC drive can provide a way to modernize the control portion of the system while retaining the existing motor and mechanical equipment.

This can be particularly valuable in production machinery where changing the motor would require substantial mechanical modifications.

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18. Industrial DC Drive Architecture

A typical 20P21AE405RA0NNN system can be divided into several sections.

AC Power Section

The three-phase AC supply provides the main electrical power to the drive.

Power Conversion Section

The six-pulse converter changes the incoming AC power into controlled DC power.

Armature Section

The controlled DC output is supplied to the motor armature.

Field Section

The motor field is supplied and regulated according to the motor requirements.

Feedback Section

Depending on the machine, a tachometer, encoder, or another feedback system may be used.

Control Section

PLC logic, analog references, external control circuits, or process controllers can determine the desired motor operation.

This architecture makes the drive part of a larger industrial automation system rather than an isolated component.

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19. Conveyor Applications

Large conveyors are a natural application for a 405 A DC drive when the existing motor is correctly matched.

A large conveyor can have considerable mechanical inertia.

During startup, the motor may need substantial torque to accelerate:

• Conveyor belts
• Rollers
• Gearboxes
• Material
• Pulleys
• Drive shafts

Controlled acceleration helps reduce mechanical shock.

This can be important for long conveyors and heavy-duty material-handling systems.

Potential applications include:

• Mining conveyors
• Bulk material conveyors
• Steel plant conveyors
• Cement plant conveyors
• Paper mill conveyors
• Heavy manufacturing conveyors
• Process conveyors

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20. Paper Processing Applications

Paper and pulp processing equipment has historically used large DC motors extensively.

A production line may contain several large drive sections operating together.

Potential applications include:

• Paper machine drives
• Roll drives
• Calender systems
• Rewinders
• Unwinders
• Coating equipment
• Slitter rewinders
• Material handling sections

Stable motor speed can be important for maintaining web tension and consistent production.

In retrofit applications, retaining the existing DC motor can sometimes simplify the mechanical side of the project.

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21. Printing Machinery

Large printing equipment can require accurate and stable motor control.

DC drives have traditionally been used in printing machinery because of their speed-control characteristics.

The 20P21AE405RA0NNN can be relevant to large DC motor systems used for:

• Press rollers
• Web handling
• Winding
• Unwinding
• Feed systems
• Coating sections
• Material transport

The actual drive size must be matched to the motor’s armature current and operating requirements.

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22. Winding and Unwinding Machines

Winding equipment can be particularly demanding because motor speed and torque often change as the roll diameter changes.

The drive may be required to maintain stable speed while the machine control system adjusts torque and tension.

Possible applications include:

• Paper winding
• Film winding
• Cable winding
• Textile winding
• Metal strip processing
• Web handling
• Slitting and rewinding

For these systems, feedback and control-loop performance can be especially important.

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23. Steel and Metal Processing

Large DC motors have historically been used in metal-processing applications.

Potential applications include:

• Roll drives
• Material feeders
• Strip processing
• Coilers
• Uncoilers
• Heavy conveyors
• Processing rolls

Such machinery can have high inertia and high torque requirements.

The 405 A rating gives the drive the current capacity needed for substantially larger motors than the smaller PowerFlex DC models.

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24. Textile Machinery

Large textile machines can require smooth and stable speed control.

Potential applications include:

• Spinning systems
• Drawing systems
• Winding systems
• Fiber processing
• Textile rollers
• Finishing equipment

For machines already designed around DC motors, a modern digital DC drive can be used as part of a control-system upgrade.

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25. Pump Applications

The 20P21AE405RA0NNN can also be considered for large DC-motor-driven pumps where the motor characteristics match the drive.

Potential applications include:

• Process pumps
• Cooling-water pumps
• Large circulation pumps
• Industrial water systems
• Process-fluid systems

Pump applications require careful consideration of the motor’s speed range and the pump’s mechanical characteristics.

The correct operating range should be established before commissioning.

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26. Fan and Blower Applications

Large industrial fans and blowers can also use high-power motors.

Potential applications include:

• Industrial ventilation
• Furnace fans
• Process exhaust
• Cooling systems
• Large blowers
• Air-handling systems

The drive can control motor speed according to the process requirement.

This can allow the machine to operate at reduced speed when full airflow is not required.

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27. Material Handling

The high current capacity of the 20P21AE405RA0NNN makes it relevant to large material-handling equipment.

Potential applications include:

• Large conveyors
• Transfer systems
• Rollers
• Feed systems
• Heavy handling machines

Special attention is required when the mechanical load can drive the motor.

For example, lowering a heavy load can create regenerative conditions.

In such applications, a non-regenerative drive should not be selected without carefully analyzing the braking system.

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28. Main Product Advantages

28.1 High 405 A DC Current Capacity

The primary advantage of the 20P21AE405RA0NNN is its 405 A armature-current rating.

This makes it suitable for large industrial DC motors.

It provides significantly more current capability than the 270 A model and is therefore appropriate for the approximately 300 HP class.

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28.2 300 HP Motor Capability

A 300 HP rating allows the drive to control large production machines.

This places the model in a high-power industrial category.

It is suitable for equipment where smaller DC drives would not provide sufficient armature current.

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28.3 Digital Control

Digital control provides flexible parameterization.

Depending on the application and configuration, the control system can manage:

• Speed
• Current
• Acceleration
• Deceleration
• Field
• Feedback
• Limits
• Protection
• Operating conditions

This is useful when upgrading older analog DC drive installations.

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28.4 Two-Quadrant Architecture

Two-quadrant operation provides controlled motor operation without requiring the complete regenerative architecture of a four-quadrant drive.

For many continuous-process applications, this can be sufficient.

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28.5 Regulated Field Supply

The regulated field supply provides controlled excitation for the motor field.

This is important for applications requiring stable field behavior and extended speed operation.

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28.6 Conformal Coating

The conformal-coated configuration provides additional protection for the electronics.

This can be useful in industrial environments where humidity and contamination are concerns.

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28.7 Suitable for Retrofit Applications

The drive is particularly relevant when an existing DC motor is still mechanically useful.

Instead of replacing the entire machine, the control system can potentially be modernized around the existing motor.

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29. Retrofit Applications

The 20P21AE405RA0NNN can be considered for replacing older DC drive equipment in existing machinery.

A typical modernization project may involve:

Existing machine

↓

Existing 300 HP DC motor

↓

Existing mechanical transmission

↓

Existing production equipment

with the older DC controller replaced by a modern digital DC drive.

This can reduce mechanical modification compared with a complete conversion to an AC motor.

However, the existing motor should be inspected carefully before such a project.

Important inspection points include:

• Armature insulation
• Field insulation
• Brushes
• Brush holders
• Commutator
• Bearings
• Cooling
• Tachometer
• Encoder
• Mechanical coupling
• Gearbox
• Motor temperature

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30. Motor Selection Considerations

The drive should not be selected based on horsepower alone.

The following motor parameters are particularly important:

Motor Parameter	Importance
Armature Voltage	Must be compatible with drive output
Armature Current	Must be compatible with 405 A rating
Field Voltage	Must match field supply
Field Current	Must be within field capability
Base Speed	Determines normal operating point
Maximum Speed	Must not exceed motor mechanical limits
Motor Duty	Continuous or intermittent
Feedback	Determines control architecture
Starting Torque	Important for sizing
Load Inertia	Important for acceleration
Braking	Determines two- vs. four-quadrant suitability
Ambient Temperature	Affects thermal performance
Cooling Method	Must be compatible with motor operation

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31. Associated Line Reactor

For the 575 VAC-class configuration, the associated line reactor commonly identified with the 20P21AE405RA0NNN is:

1321-3RB320-B

The associated rating is approximately 224 kW / 300 HP.

The drive’s approximate AC line current is 330.9 A.

Parameter	Value
Drive Model	20P21AE405RA0NNN
DC Current	405 A
AC Line Current	Approximately 330.9 A
Motor Rating	300 HP
Motor Power	Approximately 224 kW
Associated Line Reactor	1321-3RB320-B
Reactor Class	Approximately 224 kW / 300 HP

The actual line-reactor requirement depends on the electrical installation and system design.

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32. Cabinet Design

The 20P21AE405RA0NNN is intended for cabinet installation.

The cabinet should provide enough space for the drive itself as well as:

• Incoming power cables
• Motor cables
• Field wiring
• Control wiring
• Feedback wiring
• Protective devices
• Contactors
• Line reactor
• Cooling equipment
• Grounding connections

The approximate 311 × 388 × 350 mm drive envelope should not be treated as the complete cabinet space requirement.

A practical cabinet must also allow for cable bending radius and maintenance access.

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33. Thermal Management

Thermal management is especially important with a 405 A drive.

The cabinet designer should evaluate:

• Drive losses
• Ambient temperature
• Cabinet volume
• Airflow
• Cooling fan capacity
• Heat exchanger requirements
• Filter condition
• Internal temperature
• Nearby heat sources

The drive should not be installed in a tightly packed cabinet where heat cannot escape.

High internal temperature can reduce the service life of electronic components.

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34. Maintenance

Routine maintenance should cover both the drive and the motor.

Typical checks include:

• Cooling fan operation
• Cabinet cleanliness
• Terminal tightness
• Grounding
• Cable condition
• Signs of overheating
• Drive alarms
• Motor brushes
• Commutator
• Bearings
• Field wiring
• Feedback devices

The condition of the DC motor is particularly important because the motor remains a mechanical and electrical wear component.

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35. Brush and Commutator Maintenance

DC motors use brushes and commutators, which require periodic inspection.

Maintenance personnel should check for:

• Excessive brush wear
• Uneven brush wear
• Incorrect brush pressure
• Brush sparking
• Commutator damage
• Carbon buildup
• Abnormal heating
• Poor brush seating

If excessive sparking appears, the cause should be investigated rather than simply replacing brushes.

Possible causes can include:

• Motor load
• Brush position
• Field condition
• Commutator condition
• Armature condition
• Drive settings
• Feedback problems
• Mechanical issues

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36. Feedback Applications

Large industrial DC systems frequently use speed feedback.

Possible feedback devices include:

• Tachometers
• Encoders
• Other compatible speed sensors

Feedback is especially useful when precise speed regulation is required.

Applications that may benefit include:

• Winding machines
• Printing systems
• Paper machines
• Textile equipment
• Process lines
• Coordinated drive systems

The feedback device should be checked for compatibility before commissioning.

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37. Typical Control Architecture

A typical system might be structured as follows:

PLC / Machine Controller

↓

Speed Reference

↓

PowerFlex DC Drive

↓

Armature Current and Voltage Control

↓

300 HP DC Motor

↓

Mechanical Load

At the same time:

Motor Field

↓

Regulated Field Supply

and, where applicable:

Motor Speed Feedback

↓

Drive Feedback Input

This arrangement provides a closed-loop control structure suitable for many industrial machines.

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38. Five Same-Series Related Models

The following five models are closely related to the 20P21AE405RA0NNN and belong to the same PowerFlex DC family.

Model	Normal-Duty HP	Approx. kW	DC Current	Frame	Operation
20P21AE101RA0NNN	75 HP	56 kW	101.3 A	B	Two-quadrant
20P21AE135RA0NNN	100 HP	75 kW	135 A	B	Two-quadrant
20P21AE270RA0NNN	200 HP	149 kW	270 A	B	Two-quadrant
20P21AE540RA0NNN	400 HP	298 kW	540 A	C	Two-quadrant
20P21AE675RA0NNN	500 HP	373 kW	675 A	C	Two-quadrant

These models provide a useful range for comparing drive capacity.

The 20P21AE270RA0NNN is the smaller 200 HP model, while the 20P21AE540RA0NNN moves up to approximately 400 HP.

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39. Same-Series Comparison

Model	HP	kW	DC Current	Frame	Typical Application Level
20P21AE101RA0NNN	75	56	101.3 A	B	Medium industrial
20P21AE135RA0NNN	100	75	135 A	B	Medium-large industrial
20P21AE270RA0NNN	200	149	270 A	B	Large industrial
20P21AE405RA0NNN	300	224	405 A	B	High-power industrial
20P21AE540RA0NNN	400	298	540 A	C	Very high-power industrial

This comparison shows how the 20P21AE405RA0NNN fits into the PowerFlex DC product range.

It is larger than the 200 HP version while remaining in the same general Frame B range before moving to higher-frame configurations.

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40. Five Related Regenerative Models

For applications requiring regenerative or four-quadrant operation, the following models are closely related:

Model	HP	Approx. kW	DC Current	Frame	Operation
20P41AE101RA0NNN	75 HP	56 kW	101.3 A	B	Regenerative
20P41AE135RA0NNN	100 HP	75 kW	135 A	B	Regenerative
20P41AE270RA0NNN	200 HP	149 kW	270 A	B	Regenerative
20P41AE405RA0NNN	300 HP	224 kW	405 A	B	Regenerative
20P41AE540RA0NNN	400 HP	298 kW	540 A	C	Regenerative

The 20P41AE405RA0NNN is the closest same-power regenerative counterpart to the 20P21AE405RA0NNN.

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41. Same-Power Non-Regenerative and Regenerative Comparison

Parameter	20P21AE405RA0NNN	20P41AE405RA0NNN
Product Family	PowerFlex DC	PowerFlex DC
Motor Rating	300 HP	300 HP
Approx. Power	224 kW	224 kW
DC Current	405 A	405 A
Input	Three-phase	Three-phase
Input Class	575 VAC	575 VAC
Input Type	6-pulse	6-pulse
Motor Operation	Two-quadrant	Four-quadrant
Regeneration	No	Yes
Frame	B	B
Typical Use	Continuous/one-direction processes	Reversing and regenerative processes

The primary distinction is the operating quadrant and regenerative capability.

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42. Five Popular Same-Brand Models

The following models are from other popular drive families and can be considered when evaluating broader industrial modernization options.

Model	Series	Technology	Typical Voltage Class	General Application
25B-D017N114	PowerFlex 525	AC VFD	380–480 VAC class	Compact machinery
20F11NC022JA0NNNNN	PowerFlex 753	AC VFD	380–480 VAC class	General industrial machinery
20F11NC034JA0NNNNN	PowerFlex 753	AC VFD	380–480 VAC class	Medium/high-power applications
20G1ANB140JA0NNNNN	PowerFlex 755	AC VFD	380–480 VAC class	High-power machinery
20G1ANC350JA0NNNNN	PowerFlex 755	AC VFD	380–480 VAC class	Heavy-duty industrial applications

These are not direct electrical substitutes for the 20P21AE405RA0NNN.

They belong to AC drive families and therefore require an appropriate AC motor and a different system architecture.

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43. Same-Brand Model Comparison

Model	Series	Drive Technology	General Role
25B-D017N114	PowerFlex 525	AC Variable Frequency Drive	Compact machine control
20F11NC022JA0NNNNN	PowerFlex 753	AC Variable Frequency Drive	Industrial machine control
20F11NC034JA0NNNNN	PowerFlex 753	AC Variable Frequency Drive	Larger industrial machinery
20G1ANB140JA0NNNNN	PowerFlex 755	AC Variable Frequency Drive	High-power industrial control
20G1ANC350JA0NNNNN	PowerFlex 755	AC Variable Frequency Drive	Heavy-duty industrial control

When considering an AC modernization, the motor technology, voltage, current, speed range, braking method, feedback system, and mechanical load must all be evaluated.

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44. DC Drive Versus AC Drive Modernization

For an old industrial machine, there are generally two broad modernization approaches.

Approach 1: Retain the DC Motor

The existing DC motor remains in service and the old controller is replaced with a modern DC drive.

Advantages can include:

• Less mechanical modification
• Existing gearbox can remain
• Existing coupling can remain
• Existing motor can remain
• Existing machine mechanics can remain
• Shorter mechanical conversion process

Approach 2: Convert to an AC Motor

The DC motor is replaced by an AC motor and an AC variable-frequency drive.

Potential benefits can include:

• Modern AC motor technology
• Reduced brush maintenance
• Different motor efficiency characteristics
• Wider availability of modern AC drive systems

However, this can involve significantly more mechanical work.

The appropriate approach depends on the machine’s age, motor condition, production requirements, maintenance strategy, and modernization budget.

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45. Application Suitability

Application	Suitability Consideration
Large Conveyor	Very suitable when motor current matches
Paper Machine	Suitable for compatible DC motor systems
Winder	Suitable, especially with appropriate feedback
Unwinder	Requires careful braking analysis
Printing Press	Suitable for compatible DC motor systems
Steel Roll Drive	Suitable where current and torque requirements match
Textile Machinery	Suitable for large DC motor systems
Industrial Pump	Suitable when motor and pump characteristics match
Industrial Fan	Suitable for large DC motor systems
Material Handling	Requires braking and load analysis
Hoist	Requires careful regenerative analysis
High-Inertia Machine	Requires acceleration/deceleration analysis
Reversing Machine	Regenerative model may be more appropriate

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46. Installation Considerations

A proper installation should consider the complete electrical system.

Important areas include:

Incoming Power

The incoming three-phase supply must be compatible with the drive’s voltage class.

Protection

Appropriate input protection and disconnect equipment should be selected according to the installation requirements.

Line Reactor

The associated line reactor should be evaluated as part of the input power system.

Motor Cable

The motor cable must be appropriately sized for the motor current and installation conditions.

Grounding

Proper grounding is required for safety and reliable operation.

Cabinet Cooling

The cabinet must be capable of removing the heat produced by the drive.

Control Wiring

Control and feedback cables should be routed appropriately to minimize interference.

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47. Environmental Considerations

The drive’s operating environment should be evaluated before installation.

Important factors include:

• Ambient temperature
• Humidity
• Dust
• Chemical vapors
• Condensation
• Vibration
• Altitude
• Cabinet ventilation

Although conformal coating provides additional protection, it does not eliminate the need for suitable environmental control.

A clean, dry, temperature-controlled cabinet generally provides a much better operating environment for a high-power electronic drive.

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48. Maintenance Strategy

A good maintenance strategy should combine drive inspection with motor inspection.

A typical maintenance program can include:

Regular Visual Inspection

Check for:

• Dust
• Heat marks
• Loose connections
• Damaged cables
• Fan problems
• Abnormal odors

Electrical Inspection

Check:

• Power terminals
• Grounding
• Motor connections
• Field connections
• Control wiring

Motor Inspection

Check:

• Brushes
• Commutator
• Bearings
• Insulation
• Cooling
• Feedback devices

Drive Diagnostics

Review:

• Fault history
• Warning conditions
• Current behavior
• Speed behavior
• Temperature
• Abnormal operating conditions

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49. Advantages for Industrial Modernization

The 20P21AE405RA0NNN can be particularly useful when a plant has a large existing DC motor fleet.

Instead of replacing every DC motor, the maintenance department can modernize the drive control system while retaining motors that remain mechanically and electrically suitable.

This can simplify spare-parts planning because the plant can standardize around a known DC drive family.

It can also make troubleshooting easier for maintenance teams already familiar with DC motor systems.

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50. Product Advantages at a Glance

Advantage	Practical Value
405 A DC rating	Handles large industrial DC motors
300 HP rating	Suitable for high-power machinery
224 kW class	Large industrial power capacity
Digital control	Flexible drive configuration
Six-pulse input	Familiar industrial architecture
Two-quadrant operation	Suitable for many one-direction processes
Regulated field	Controlled motor excitation
Conformal coating	Additional electronic protection
No HIM configuration	Suitable for externally controlled cabinets
IP20 construction	Appropriate for cabinet installations
PowerFlex DC family	Suitable for DC motor modernization
High-current design	Suitable for heavy industrial loads

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51. Detailed Parameter Table

Parameter	20P21AE405RA0NNN
Product Model	20P21AE405RA0NNN
Brand	Allen-Bradley
Product Family	PowerFlex
Series	PowerFlex DC
Product Type	Digital DC Drive
Rated Motor Power	300 HP
Rated Motor Power	Approximately 224 kW
DC Armature Current	405 A
AC Input Voltage Class	500–600 VAC
Typical Input Voltage	575 VAC
AC Input	Three-phase
Input Type	6-pulse
Motor Operation	Two-quadrant
Regeneration	Non-regenerative
Field Supply	Single-phase regulated
Enclosure	IP20
Enclosure Type	NEMA/UL Type Open
Frame	B
HIM	Blank Plate / No HIM
Communication Module	None
Conformal Coating	Yes
Approx. AC Line Current	330.9 A
Associated Line Reactor	1321-3RB320-B
Line Reactor Rating	224 kW / 300 HP class
Approx. Height	311 mm
Approx. Width	388 mm
Approx. Depth	350 mm
Approx. Drive Weight	29.5 kg
Approx. Packaged Weight	31.5 kg
Mounting	Panel / Cabinet
Main Use	Industrial DC motor control
Typical Motor	300 HP class DC motor

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52. Five Recommended Same-Series Models

Model	Rated HP	Rated kW	DC Current	Frame	Operation
20P21AE135RA0NNN	100 HP	75 kW	135 A	B	Two-quadrant
20P21AE270RA0NNN	200 HP	149 kW	270 A	B	Two-quadrant
20P21AE405RA0NNN	300 HP	224 kW	405 A	B	Two-quadrant
20P21AE540RA0NNN	400 HP	298 kW	540 A	C	Two-quadrant
20P21AE675RA0NNN	500 HP	373 kW	675 A	C	Two-quadrant

These five models give a useful progression around the 300 HP model.

The 200 HP version is a logical lower-capacity comparison, while the 400 HP and 500 HP versions provide higher-capacity alternatives.

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53. Five Recommended Same-Brand Models

Model	Series	Technology	General Application
25B-D017N114	PowerFlex 525	AC VFD	Compact industrial machines
20F11NC022JA0NNNNN	PowerFlex 753	AC VFD	Industrial motor control
20F11NC034JA0NNNNN	PowerFlex 753	AC VFD	Medium/high-power machines
20G1ANB140JA0NNNNN	PowerFlex 755	AC VFD	High-power industrial systems
20G1ANC350JA0NNNNN	PowerFlex 755	AC VFD	Heavy-duty industrial systems

These five models are best viewed as broader same-brand options rather than direct replacements.

A conversion from the 20P21AE405RA0NNN to an AC drive would normally require an AC motor and potentially changes to the mechanical and control systems.

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54. Recommended Selection Approach

For a machine using a 300 HP DC motor, the first step should be to compare the motor nameplate data against the 20P21AE405RA0NNN.

The most important values are:

Armature voltage

Armature current

Field voltage

Field current

Base speed

Maximum speed

Duty cycle

Feedback type

Braking requirements

Direction of rotation

If the motor requires approximately 405 A or less under the applicable duty conditions and the other electrical parameters are compatible, the model can be a strong candidate for that motor class.

If the machine requires regenerative braking or frequent reversal, the non-regenerative 20P21AE405RA0NNN should be compared with an appropriate regenerative model.

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55. Final Product Summary

Item	Specification
Product	PowerFlex DC Drive
Model	20P21AE405RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Motor Rating	300 HP
Power Rating	Approximately 224 kW
DC Current	405 A
AC Input	Three-phase
Input Voltage Class	500–600 VAC
Typical Input	575 VAC
Input Type	6-pulse
Motor Operation	Two-quadrant
Regenerative	No
Field Supply	Single-phase regulated
Enclosure	IP20 / NEMA/UL Type Open
Frame	B
Conformal Coating	Yes
HIM	Blank Plate / No HIM
Communication	None-Standard
AC Line Current	Approximately 330.9 A
Associated Line Reactor	1321-3RB320-B
Height	Approximately 311 mm
Width	Approximately 388 mm
Depth	Approximately 350 mm
Drive Weight	Approximately 29.5 kg
Packaged Weight	Approximately 31.5 kg
Typical Applications	Conveyors, paper machines, printing equipment, winders, textile machines, steel processing, pumps, fans and heavy industrial machinery

56. Final Description

The Allen-Bradley 20P21AE405RA0NNN is a high-power PowerFlex DC drive rated at 405 A and approximately 300 HP / 224 kW.

Its three-phase, 575 VAC-class input, six-pulse conversion architecture, regulated field supply, digital control, two-quadrant operation, and cabinet-oriented IP20 construction make it suitable for large industrial DC motor systems.

The model is particularly relevant to machinery where a large DC motor is already installed and continued use of the existing motor and mechanical system is desirable.

Typical applications include heavy conveyors, paper-processing machinery, printing presses, winding and unwinding systems, steel and metal processing equipment, textile machinery, large pumps, industrial fans, process machinery, and heavy material-handling systems.

Its 405 A current rating is the defining characteristic of the model. Compared with smaller PowerFlex DC models, it provides the additional current capacity required by approximately 300 HP industrial motors.

The two-quadrant, non-regenerative configuration makes it appropriate for many applications where the motor normally operates in one direction and does not require continuous regenerative energy transfer back to the AC supply.

Where the application requires frequent reversing, sustained braking, lowering of overhauling loads, or four-quadrant operation, the regenerative counterpart should be evaluated instead.

From a modernization perspective, the 20P21AE405RA0NNN can be especially useful when an existing DC motor remains in good condition. A digital DC drive can modernize the electrical control system while potentially allowing the existing motor, gearbox, coupling, and machine mechanics to remain in service.

For a 300 HP DC motor installation, however, selection should always be based on the complete motor nameplate and machine requirements rather than horsepower alone. Armature current, armature voltage, field voltage, field current, speed range, feedback, acceleration, deceleration, braking, ambient temperature, and cabinet cooling all have to be considered together.

Overall, the 20P21AE405RA0NNN represents a high-current industrial DC drive solution within the PowerFlex DC family, intended for large and demanding DC motor applications where controlled speed, current regulation, field control, and reliable industrial operation are required.