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20P21AD045RA0NNN PowerFlex DC Drive

Detailed Specifications, Product Introduction, Applications, Advantages and Related Model Recommendations

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1. Product Overview

The 20P21AD045RA0NNN is a 45 A PowerFlex DC drive designed for industrial DC motor control applications.

It is a 480 VAC-class, three-phase DC drive with a 45 A armature current rating and a 25 HP / approximately 18.5 kW motor power class. The drive uses a six-pulse input arrangement and is designed for two-quadrant, non-regenerative operation. It is supplied in an IP20, NEMA/UL Type Open enclosure and uses a Frame A mechanical construction.

The standard configuration includes a blank front plate instead of a local HIM operator interface and does not include a communication module. Standard I/O is provided for integration with external control equipment, making the unit suitable for machine-control systems based on PLCs, pushbuttons, analog references and hardwired interlocks.

The 45 A rating makes this model a useful choice for applications requiring more capacity than the 27 A or 35 A versions while remaining within the compact Frame A range.

It is particularly suitable for industrial equipment where an existing DC motor needs controlled speed and torque operation without replacing the entire motor and mechanical transmission system.

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2. Brand and Product Series

Item	Specification
Brand	Allen-Bradley
Product family	PowerFlex
Series	PowerFlex DC
Product category	Industrial DC Drive
Model	20P21AD045RA0NNN
Drive type	Digital DC Drive
Current rating	45 A
Motor power class	25 HP
Approximate metric power class	18.5 kW
Input voltage class	480 VAC
Nominal input voltage	460 VAC
Input phase	Three-phase
Input configuration	6-pulse
Motor operation	Two-quadrant
Regenerative operation	Non-regenerative
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Frame	Frame A
Cooling	Air cooled
Conformal coating	Yes
HIM	Blank plate
Communication module	None included
Field supply	Single-phase regulated

The PowerFlex DC series is intended for controlled operation of industrial DC motors and is especially relevant in retrofit projects where the DC motor and mechanical system are still serviceable.

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3. Main Technical Specifications

Parameter	Specification
Model	20P21AD045RA0NNN
Product family	PowerFlex DC
Product type	Industrial DC Drive
Input voltage	480 VAC class
Nominal input voltage	460 VAC
Input frequency	50/60 Hz
Input phase	3-phase
Input configuration	6-pulse
Armature current	45 A
Motor rating	25 HP
Motor rating	Approximately 18.5 kW
Motor operation	Two-quadrant
Regenerative operation	No
Field supply	Single-phase regulated
Enclosure rating	IP20
Enclosure type	NEMA/UL Type Open
Frame size	Frame A
Cooling method	Air cooled
Conformal coating	Yes
Operator interface	Blank plate / no standard HIM
Communication module	None included
Digital inputs	8 × 24 VDC
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback capability	DC tachometer / encoder capable
Height	Approx. 267 mm
Width	Approx. 359 mm
Depth	Approx. 287 mm
Overall dimensions	Approx. 267 × 359 × 287 mm
Drive weight (kg)	Approx. 11.5 kg
Drive weight	Approx. 25.4 lb
Packaging weight	Approx. 13.5 kg
Mounting	Panel / cabinet
Installation environment	Protected industrial enclosure

The Frame A dimensions are approximately 267 mm high, 359 mm wide and 287 mm deep. Published technical data groups the 45 A version with the 11.5 kg Frame A drive-weight class; packaged weight is approximately 13.5 kg.

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4. Product Introduction

The 20P21AD045RA0NNN is designed to control the operation of a compatible industrial DC motor by regulating the electrical power supplied to the motor armature.

A DC drive of this type can provide controlled motor starting, stopping, acceleration, deceleration, speed regulation and torque control.

The 45 A armature rating gives the model a relatively high capacity within the Frame A range.

With a nominal 25 HP rating, the unit is suitable for machinery requiring a substantial amount of controlled mechanical power while still using a conventional DC motor.

This makes the model particularly useful in plants where DC motors have already been installed and replacing the entire motor, gearbox, coupling, feedback system and machine mechanics would be expensive or disruptive.

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5. 45 A Armature Current Rating

The most important electrical specification of the 20P21AD045RA0NNN is its 45 A armature current rating.

The armature current determines the electrical current available to the motor armature and is closely related to the torque capability of a DC motor.

A 45 A drive therefore provides more current capacity than the smaller 19 A, 27 A and 35 A configurations.

This makes it appropriate for larger industrial DC motors.

The approximate power class is:

25 HP / 18.5 kW

The actual motor should always be selected according to its nameplate data rather than horsepower alone.

The following motor parameters should be checked:

• Armature voltage
• Armature current
• Field voltage
• Field current
• Horsepower
• Base speed
• Maximum speed
• Feedback type
• Duty cycle
• Starting torque
• Braking requirements

A motor with an armature current below the drive rating can generally be considered from a capacity standpoint, provided all other electrical and application requirements are satisfied.

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6. 25 HP / 18.5 kW Motor Class

The 20P21AD045RA0NNN belongs to the approximately 25 HP / 18.5 kW DC motor power class.

This makes it suitable for industrial equipment that requires more power than typical 10 HP or 15 HP DC applications.

Typical machinery may include:

• Large conveyors
• Heavy roller systems
• Material feeders
• Paper-processing machinery
• Textile machinery
• Printing equipment
• Machine tools
• Processing equipment
• Material-handling systems
• Production-line machinery
• Industrial winding-related auxiliary equipment

For applications involving substantial regenerative energy, however, the non-regenerative configuration needs to be evaluated carefully.

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7. Three-Phase 480 VAC Input

The model is designed for a 480 VAC-class three-phase input, with the 460 VAC rating commonly associated with this configuration.

This makes it suitable for conventional industrial electrical systems.

Three-phase industrial power is commonly used in manufacturing plants and processing facilities because it provides an efficient power source for larger industrial equipment.

Typical installation environments include:

• Manufacturing plants
• Production lines
• Machine shops
• Processing facilities
• Material-handling plants
• Paper-processing facilities
• Textile production facilities
• Printing plants
• Industrial automation systems

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8. Six-Pulse Input

The drive uses a 6-pulse input configuration.

Six-pulse conversion is a conventional architecture for industrial DC drives.

It converts three-phase AC input power into controlled DC power for the motor system.

This architecture is particularly useful in retrofit applications because many existing DC drive installations use similar power-conversion principles.

For replacement work, the engineer should compare the original drive’s:

• Input voltage
• Input phase
• Armature voltage
• Armature current
• Field supply
• Feedback configuration
• Control wiring

before installing the replacement.

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9. Two-Quadrant Operation

The 20P21AD045RA0NNN is a two-quadrant drive.

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

Typical applications include:

• Conveyors
• Feeders
• Pumps
• Fans
• Rollers
• Processing machinery
• Machine tools
• General production equipment

Two-quadrant operation is often sufficient for conventional motor-driven machinery.

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10. Non-Regenerative Design

The model is a non-regenerative DC drive.

This is an important consideration when selecting the drive.

During normal motoring operation, electrical energy flows from the drive to the motor.

During certain types of braking, however, mechanical energy can cause the motor to act as a generator.

If a machine has high inertia or frequently decelerates heavy loads, a significant amount of energy can be returned from the motor toward the drive.

Applications with substantial regenerative energy should therefore be evaluated separately.

For those applications, a regenerative configuration from the same general family may be more appropriate.

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11. Application Suitability

Application	Suitability
Standard conveyor	Very suitable
Heavy conveyor	Very suitable
Roller drive	Very suitable
Material feeder	Very suitable
Printing machinery	Suitable
Paper machinery	Suitable
Textile machinery	Suitable
Machine tools	Suitable
Pump	Suitable
Fan	Suitable
General processing machinery	Very suitable
High-inertia winder	Requires evaluation
Unwinder	Regeneration must be evaluated
Hoist	Regenerative requirements must be evaluated
Frequent regenerative braking	Regenerative configuration preferred
Four-quadrant operation	Use a regenerative configuration

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12. Main Applications

12.1 Conveyor Systems

The 45 A capacity makes this model suitable for medium and larger conveyor systems.

Potential applications include:

• Belt conveyors
• Roller conveyors
• Transfer conveyors
• Assembly conveyors
• Packaging conveyors
• Production-line conveyors
• Heavy material-handling conveyors

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

Controlled speed can also help maintain consistent product flow.

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13. Roller Applications

Industrial rollers often require accurate and repeatable speed control.

The drive can be applied to suitable DC motors used for:

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

Feedback capability can be particularly useful when roller speed must remain stable as load conditions change.

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14. Printing Machinery

DC motor technology has historically been used in many printing and web-processing machines.

The 20P21AD045RA0NNN can be considered for suitable DC motor applications such as:

• Printing rollers
• Paper feed systems
• Web-processing equipment
• Auxiliary drives
• Material feed systems
• Processing rollers

Where web tension or frequent braking is involved, the regenerative characteristics of the machine should be analyzed carefully.

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15. Paper Processing Machinery

The model can be applied to suitable DC motors used in paper-processing systems.

Potential applications include:

• Paper feed systems
• Roll drives
• Material transport
• Processing rollers
• Coating machinery
• Production-line equipment

Stable motor speed can be important for maintaining consistent material movement.

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16. Textile Machinery

Textile machinery often requires controlled motor speed and smooth acceleration.

Potential applications include:

• Textile rollers
• Feed systems
• Processing machines
• Spinning-related machinery
• Winding-related equipment
• Material transport systems
• Production-line equipment

For tension-controlled winding and unwinding applications, however, the non-regenerative architecture should not be selected without reviewing the actual load cycle.

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17. Material-Handling Equipment

Material-handling machinery can benefit from controlled acceleration, speed and stopping.

Potential applications include:

• Conveyors
• Feeders
• Transfer equipment
• Rollers
• Sorting machinery
• Production-line transport
• Heavy material-handling systems

The 45 A rating provides additional capacity for machines with higher torque requirements.

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18. Machine Tools

Suitable DC motors in machine tools can also be controlled by this drive.

Potential applications include:

• Grinding machinery
• Feed mechanisms
• Specialized machine tools
• Cutting equipment
• Processing machines
• Production machinery

Where precise speed regulation is required, the feedback configuration becomes particularly important.

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19. Feedback Capability

The PowerFlex DC platform supports feedback arrangements such as DC tachometer and encoder feedback.

Feedback is useful when the machine requires stable speed under varying loads.

For example, a roller may experience different loads depending on material thickness.

Without feedback, motor speed can change as load torque changes.

With suitable feedback, the drive can compare commanded speed with actual motor speed and make corrections.

This can improve:

• Speed regulation
• Process stability
• Product consistency
• Acceleration performance
• Load response
• Machine repeatability

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20. Regulated Field Supply

The model uses a single-phase regulated field supply.

The field circuit is essential to the operation of a conventional DC motor.

The motor field establishes the magnetic field required for torque production and normal motor operation.

Before commissioning, the following parameters should be verified:

Field Parameter	Check
Field voltage	Must match motor requirement
Field current	Must remain within motor rating
Field wiring	Correct polarity and connection
Field loss protection	Correctly configured
Field weakening	Verify motor capability
Maximum speed	Verify motor mechanical limit

Incorrect field configuration can result in poor performance or motor damage.

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21. Standard I/O

The model provides a useful set of standard control I/O.

I/O Type	Quantity	Typical Application
24 VDC Digital Inputs	8	Start, stop, enable, direction, reset and interlocks
Digital Outputs	4	Run, ready, fault and status
Analog Inputs	2	Speed reference or process reference
Analog Outputs	3	Speed, current, feedback or process monitoring

This makes the drive suitable for hardwired control systems.

A PLC can provide:

• Start
• Stop
• Enable
• Direction
• Speed reference
• Reset

The drive can then manage the motor according to the configured control parameters.

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22. Blank Front Plate

The model is supplied with a blank front plate rather than a standard HIM.

This configuration is particularly suitable when the drive is controlled from an external machine control panel.

The operator can interact with:

• Pushbuttons
• Selector switches
• HMI
• PLC
• Machine controller
• External speed potentiometer

rather than directly operating a keypad mounted on the drive.

This can be useful when the drive is installed inside a cabinet.

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23. No Standard Communication Module

The catalog configuration does not include a communication module.

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

Hardwired I/O can be used for:

• Run commands
• Stop commands
• Direction
• Speed reference
• Fault indication
• Drive-ready indication
• External interlocks

Where network communication is required, the appropriate communication architecture should be evaluated separately.

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24. IP20 Enclosure

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

This means the drive is intended for installation inside a suitable protected electrical cabinet or enclosure.

It should not be treated as a weatherproof or washdown-rated device.

The installation should protect the drive from:

• Water
• Direct moisture
• Condensation
• Conductive dust
• Excessive contamination
• Mechanical impact
• Harsh environmental exposure

Adequate ventilation must also be maintained.

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25. Conformal Coating

The specified configuration includes conformal coating.

Conformal coating provides an additional protective layer over electronic components.

This can be beneficial in suitable industrial environments where electronic equipment may encounter:

• Humidity
• Dust
• Airborne contaminants
• Industrial particles
• Production-related contamination

Conformal coating does not mean the drive can be directly exposed to water.

The IP20 enclosure still requires a protected installation.

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26. Frame A Mechanical Construction

The 20P21AD045RA0NNN uses Frame A construction.

Frame A dimensions are approximately:

267 mm × 359 mm × 287 mm

The approximate drive weight is:

11.5 kg

The packaged weight is approximately:

13.5 kg

These dimensions make the drive relatively compact for a 45 A / 25 HP-class DC drive.

This is particularly useful in retrofit projects where cabinet space is limited.

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27. Dimensions and Weight

Mechanical Parameter	Specification
Model	20P21AD045RA0NNN
Frame	Frame A
Height	Approx. 267 mm
Width	Approx. 359 mm
Depth	Approx. 287 mm
Dimensions	Approx. 267 × 359 × 287 mm
Drive weight (kg)	Approx. 11.5 kg
Packaging weight	Approx. 13.5 kg
Drive weight	Approx. 25.4 lb
Packaging weight	Approx. 29.8 lb
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Cooling	Air cooled
Installation	Cabinet / protected enclosure
Mounting	Panel installation

The dimensions are based on the Frame A mechanical data, while the 45 A code falls into the 11.5 kg drive-weight group in the technical data.

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28. Advantages of the 20P21AD045RA0NNN

28.1 Higher 45 A Capacity

The 45 A armature rating is a major advantage.

It provides more current capacity than smaller 19 A, 27 A and 35 A models.

This makes it suitable for larger DC motors and heavier industrial loads.

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28.2 25 HP Power Class

The approximately 25 HP / 18.5 kW capacity places this model in a useful industrial power range.

It can handle applications that are too large for many smaller DC drive configurations.

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28.3 480 VAC-Class Three-Phase Input

The 480 VAC-class three-phase input is suitable for common industrial electrical systems.

This makes the drive practical for manufacturing and processing plants with conventional three-phase power distribution.

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28.4 Two-Quadrant Operation

Two-quadrant operation is suitable for many conventional motoring applications.

This can simplify selection when the machine does not require continuous regenerative operation.

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28.5 Regulated Field Supply

The regulated field supply provides appropriate control of the DC motor field circuit.

This supports stable and controlled motor operation.

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28.6 Feedback Capability

The capability to use tachometer or encoder feedback provides flexibility for applications where speed accuracy matters.

This is particularly valuable for:

• Roll drives
• Feed systems
• Printing machinery
• Textile machinery
• Process equipment

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28.7 Flexible Standard I/O

The standard digital and analog I/O provides convenient integration with existing machine controllers.

This is especially helpful when replacing an older DC drive without completely redesigning the machine-control system.

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28.8 Conformal Coating

Conformal coating provides an additional layer of electronic protection for suitable industrial environments.

This can improve suitability for controlled industrial conditions involving humidity and airborne contamination.

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28.9 Compact Frame A Design

The Frame A mechanical package is relatively compact for its 45 A current class.

The approximate footprint is:

267 × 359 × 287 mm

This can simplify cabinet planning and retrofit work.

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28.10 External Control Architecture

The blank-plate configuration is useful for machines controlled by a central PLC or operator panel.

The drive does not require a local operator keypad for normal machine operation.

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29. Main Advantages at a Glance

Feature	Practical Advantage
45 A armature rating	Suitable for larger DC motors
25 HP / 18.5 kW class	Suitable for medium-to-heavy industrial machinery
480 VAC-class input	Fits common industrial power systems
3-phase input	Suitable for industrial installations
6-pulse architecture	Conventional DC-drive topology
Two-quadrant operation	Suitable for conventional motoring applications
Non-regenerative design	Suitable for standard loads
Regulated field supply	Supports controlled DC motor operation
Tachometer / encoder capability	Improves speed-control flexibility
8 digital inputs	Flexible machine integration
4 digital outputs	Useful status and control signals
2 analog inputs	Speed/process reference flexibility
3 analog outputs	Monitoring and feedback flexibility
Conformal coating	Additional electronic protection
IP20 enclosure	Suitable for cabinet installation
Frame A	Compact mechanical package
Blank front plate	Suitable for external machine control

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30. Five Recommended Models from the Same Series or Related Family

The following models are useful comparison choices when selecting a drive around the 45 A / 25 HP range.

Model	Series	Input Class	Current Rating	Approx. Power	Operation	Regenerative	Dimensions	Weight (kg)
20P21AD027RA0NNN	PowerFlex DC	460/480 VAC	27 A	15 HP / 11 kW	Two-quadrant	No	Frame A, approx. 267 × 359 × 287 mm	Approx. 11.5
20P21AD035RA0NNN	PowerFlex DC	460/480 VAC	35 A	20 HP / 15 kW	Two-quadrant	No	Frame A, approx. 267 × 359 × 287 mm	Approx. 11.5
20P21AD045RA0NNN	PowerFlex DC	460/480 VAC	45 A	25 HP / 18.5 kW	Two-quadrant	No	Approx. 267 × 359 × 287 mm	Approx. 11.5
20P21AD052RA0NNN	PowerFlex DC	460/480 VAC	52 A	30 HP class	Two-quadrant	No	Frame A, approx. 267 × 359 × 287 mm	Approx. 12
20P41AD045RA0NNN	PowerFlex DC	460/480 VAC	45 A class	25 HP class	Regenerative	Yes	Frame-dependent	Frame-dependent

The first four selections are intended as adjacent or closely related choices within the non-regenerative PowerFlex DC range. The 20P41 configuration is the more relevant direction when regenerative or four-quadrant operation is required.

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31. Recommended Model 1 — 20P21AD027RA0NNN

The 20P21AD027RA0NNN is a lower-current configuration within the same PowerFlex DC family.

It provides approximately:

27 A / 15 HP / 11 kW

This model is appropriate when the motor does not require the full 45 A capacity.

Typical applications include:

• Medium conveyors
• Feeders
• Roller drives
• Textile equipment
• Printing machinery
• General processing equipment

The main advantage is that the drive capacity is more closely matched to a smaller motor.

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32. Recommended Model 2 — 20P21AD035RA0NNN

The 20P21AD035RA0NNN is the 35 A version of the same general drive family.

Its approximate rating is:

35 A / 20 HP / 15 kW

It is an excellent comparison model when the motor is in the 20 HP class.

It can be used for:

• Conveyors
• Rollers
• Feed systems
• Paper machinery
• Textile machinery
• Production equipment

Compared with the 45 A model, the 35 A version is better suited when the motor’s armature current is comfortably below 45 A and additional current capacity is unnecessary.

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33. Recommended Model 3 — 20P21AD052RA0NNN

The 20P21AD052RA0NNN is a higher-current option.

Its approximate rating is:

52 A / 30 HP class

This makes it suitable when the 45 A drive does not provide enough current capacity.

Potential applications include:

• Heavy conveyors
• Large rollers
• High-load feeders
• Processing machinery
• Material-handling systems
• Larger production machinery

The 52 A model should be selected according to the motor nameplate current and the actual load cycle.

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34. Recommended Model 4 — 20P21AD073RA0NNN

The 20P21AD073RA0NNN provides a substantially higher current capacity within the same general PowerFlex DC family.

It is intended for larger DC motor applications than the 45 A model.

Typical applications can include:

• Heavy industrial conveyors
• Large processing machines
• High-torque material handling
• Larger roller systems
• Industrial production machinery

When moving to this size range, cabinet thermal management, motor field requirements, braking behavior and power-distribution requirements become increasingly important.

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35. Recommended Model 5 — 20P41AD045RA0NNN

The 20P41AD045RA0NNN is a related regenerative configuration worth considering when the application needs energy handling during braking.

The key difference is the operating architecture.

The 20P21 model is intended for non-regenerative two-quadrant operation.

A 20P41 regenerative configuration is more appropriate when the motor may frequently operate as a generator.

Typical examples include:

• Winders
• Unwinders
• High-inertia machinery
• Frequent braking applications
• Hoisting-related machinery
• Four-quadrant applications

The exact rating and configuration should be checked against the motor and application before selection.

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36. Five Popular Models from the Same Brand

For users comparing the 20P21AD045RA0NNN with other widely used drive products, the following models provide useful reference points.

Model	Product Family	Drive Type	Typical Voltage Class	Current / Power Class	Typical Application	Dimensions	Weight (kg)
20P21AD035RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	35 A / 20 HP	General DC machinery	Approx. 267 × 359 × 287 mm	Approx. 11.5
20P21AD045RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	45 A / 25 HP	Larger DC machinery	Approx. 267 × 359 × 287 mm	Approx. 11.5
20P41AD045RA0NNN	PowerFlex DC	Regenerative DC Drive	460/480 VAC	45 A class	Regenerative DC machinery	Frame-dependent	Frame-dependent
25B-D017N104	PowerFlex 525	AC Drive	380–480 VAC	17 A class	General AC motor control	Compact frame	Approx. 2–3
20F1AG077AA0NNNNN	PowerFlex 753	AC Drive	380–480 VAC	Higher-power class	Industrial AC motor control	Frame-dependent	Frame-dependent

The AC-drive models above should be treated as modernization alternatives, not direct replacements for a DC drive. A conversion from DC motor technology to AC motor technology normally requires evaluation of the motor, feedback, braking, control logic and mechanical load.

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37. DC Drive vs. AC Drive Modernization

Item	20P21AD045RA0NNN	Modern AC Drive
Motor type	DC motor	AC motor
Drive output	Controlled DC	Variable-frequency AC
Existing DC motor retained	Yes	Usually no
Existing mechanical system retained	Often	Often
Motor replacement required	Usually not	Normally required
Existing feedback	Potentially reusable	May require redesign
Control redesign	Usually limited	Potentially significant
Retrofit complexity	Lower	Higher
Main advantage	Preserve existing DC machine	Modernize to AC technology
Typical purpose	DC drive replacement	Complete drive/motor modernization

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38. Retrofit Value

The 20P21AD045RA0NNN can be particularly useful in industrial retrofit projects.

A machine may have a mechanically sound DC motor but an aging drive.

Replacing the drive instead of the entire motor system can reduce the amount of modification required.

Potentially retained equipment may include:

• DC motor
• Gearbox
• Coupling
• Mechanical transmission
• Conveyor
• Rollers
• Feedback equipment
• Machine structure
• Operator station
• PLC

This can make a drive replacement considerably less disruptive than a complete machine conversion.

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39. Typical Control Architecture

A conventional installation can be represented as:

PLC / Machine Controller → Drive I/O → DC Drive → DC Motor → Mechanical Load

When feedback is used:

DC Motor → Tachometer / Encoder → DC Drive

The PLC or machine controller can provide:

• Start
• Stop
• Enable
• Direction
• Speed reference
• Reset

The drive handles the motor-side electrical control.

This architecture is practical for machines that already use hardwired industrial control systems.

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40. Speed Regulation

Speed regulation is one of the primary functions of the drive.

A speed command can be supplied through an analog input or another configured control method.

When feedback is used, the drive can continuously compare actual motor speed with the desired speed.

This is useful when load changes could otherwise produce noticeable speed variation.

Applications where this can be important include:

• Rollers
• Feeders
• Printing machines
• Textile equipment
• Paper-processing equipment
• Material transport
• Production machinery

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41. Acceleration and Deceleration

Controlled acceleration reduces the possibility of sudden mechanical stress.

Without controlled acceleration, starting a high-power motor can produce:

• Mechanical shock
• Belt stress
• Coupling stress
• Gearbox stress
• Product instability
• High starting current

The drive allows the acceleration profile to be configured according to the machine requirements.

Deceleration needs additional attention because this model is non-regenerative.

If the mechanical load continuously drives the motor during deceleration, the application may require a different braking arrangement or regenerative drive architecture.

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42. Torque Control

DC motor torque is closely related to armature current.

The 45 A armature rating therefore provides substantial torque capability for a compatible motor.

This is useful in:

• Heavy conveyors
• Feed mechanisms
• Roll drives
• Material handling
• Processing machinery
• Machine tools
• Production equipment

The actual current limit should be configured according to the motor’s nameplate and the required duty cycle.

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43. Motor Compatibility Checklist

Before selecting the 20P21AD045RA0NNN, the following motor information should be checked.

Motor Parameter	Required Check
Armature voltage	Must match drive output capability
Armature current	Must be compatible with 45 A drive rating
Field voltage	Must match field supply requirement
Field current	Must remain within motor rating
Horsepower	Approximately 25 HP class
Base speed	Verify against machine
Maximum speed	Verify motor limit
Feedback	Check tachometer / encoder
Duty cycle	Continuous or intermittent
Starting torque	Verify load requirement
Braking	Determine whether regeneration occurs
Motor condition	Check brushes and commutator
Insulation	Check insulation condition
Cooling	Verify motor cooling method

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44. Cabinet Installation Considerations

The approximate drive dimensions are:

267 mm × 359 mm × 287 mm

The approximate drive weight is:

11.5 kg

The cabinet should provide additional space beyond the physical dimensions.

Additional clearance may be required for:

• Power wiring
• Control wiring
• Feedback wiring
• Ventilation
• Maintenance
• Terminal access
• Cable bending radius
• Heat dissipation

The drive should not be installed in a position that blocks airflow.

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45. Thermal Management

Because the unit is an industrial power-electronic device, heat management is important.

The cabinet should be designed to prevent excessive ambient temperature.

Important factors include:

• Cabinet temperature
• Airflow
• Drive spacing
• Fan operation
• Dust accumulation
• Nearby heat sources
• Cabinet ventilation
• Heat exchanger or cooling system where required

Poor thermal management can shorten electronic component life.

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46. Maintenance Considerations

Routine maintenance should include inspection of:

• Cooling fan
• Airflow
• Power terminals
• Control terminals
• Feedback connections
• Field wiring
• Armature wiring
• Grounding
• Cabinet cleanliness
• Motor brushes
• Motor commutator
• Fault history

The motor itself should not be overlooked.

A DC motor with worn brushes or a damaged commutator can cause drive faults even when the drive is operating correctly.

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47. Selection by Current Rating

Model	Current Class	Approx. Power Class	Typical Position
20P21AD010RA0NNN	10 A	5 HP class	Smaller DC motor
20P21AD014RA0NNN	14 A	7.5 HP class	Small/medium motor
20P21AD019RA0NNN	19 A	10 HP class	Medium motor
20P21AD027RA0NNN	27 A	15 HP class	Medium/large motor
20P21AD035RA0NNN	35 A	20 HP class	Larger motor
20P21AD045RA0NNN	45 A	25 HP / 18.5 kW	Main model
20P21AD052RA0NNN	52 A	30 HP class	Heavy-duty motor
20P21AD073RA0NNN	73 A	Larger motor class	Higher-capacity application

The 45 A model sits naturally between the 35 A and 52 A configurations and is a useful selection when the motor requires approximately 25 HP-class capacity.

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48. Quick Comparison of Related Models

Model	Current	Approx. Power	Regenerative	Typical Use
20P21AD027RA0NNN	27 A	15 HP	No	Medium DC machinery
20P21AD035RA0NNN	35 A	20 HP	No	Medium-large DC machinery
20P21AD045RA0NNN	45 A	25 HP / 18.5 kW	No	Larger conventional DC machinery
20P21AD052RA0NNN	52 A	30 HP class	No	Heavy-duty DC machinery
20P21AD073RA0NNN	73 A	Larger power class	No	Higher-power DC machinery
20P41AD045RA0NNN	45 A class	25 HP class	Yes	Regenerative applications

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49. Application Matching

Application	Recommended Direction
15 HP conventional DC conveyor	20P21AD027RA0NNN
20 HP conventional DC machine	20P21AD035RA0NNN
25 HP conventional DC machine	20P21AD045RA0NNN
30 HP conventional DC machine	20P21AD052RA0NNN
Larger DC machine	20P21AD073RA0NNN
25 HP regenerative application	20P41AD045RA0NNN
Standard conveyor	20P21 series
Heavy roller	20P21AD045 or higher, depending on motor
High-inertia winder	Regenerative configuration should be evaluated
Unwinder	Regenerative configuration should be evaluated
Hoist	Four-quadrant/regenerative configuration should be evaluated

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50. Why Choose the 20P21AD045RA0NNN?

The model is particularly attractive when an application falls into the following range:

Three-phase 460/480 VAC input

45 A armature current

Approximately 25 HP / 18.5 kW motor

Two-quadrant operation

Non-regenerative load

IP20 cabinet installation

External machine control

Optional tachometer or encoder feedback

This combination covers a large number of conventional industrial DC motor applications.

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51. Key Product Advantages for Buyers

For a buyer or engineer evaluating the product, the main benefits can be summarized as follows.

The 45 A capacity gives the drive enough current capability for many 25 HP-class DC motors.

The Frame A construction provides a compact package, which is useful when replacing an older drive inside an existing cabinet.

The regulated field supply allows the field circuit to be managed as part of the overall motor-control system.

The feedback capability provides additional flexibility for speed-sensitive applications.

The standard I/O allows straightforward integration with PLC-based control systems.

The blank front plate is useful when the machine uses an external HMI or control panel.

The conformal coating adds additional protection for the electronics in suitable industrial environments.

The IP20 enclosure makes the drive suitable for installation inside a properly designed electrical cabinet.

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52. Product Specification Summary

Specification	Value
Catalog Number	20P21AD045RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Product category	Digital DC Drive
Input voltage	480 VAC class
Nominal input	460 VAC
Input phase	3-phase
Input configuration	6-pulse
Armature current	45 A
Motor power	25 HP
Metric motor power	Approx. 18.5 kW
Motor operation	Two-quadrant
Regenerative	No
Field supply	Single-phase regulated
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Frame	Frame A
Cooling	Air cooled
Conformal coating	Yes
HIM	Blank plate
Communication module	None
Digital inputs	8 × 24 VDC
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback	Tachometer / encoder capable
Height	Approx. 267 mm
Width	Approx. 359 mm
Depth	Approx. 287 mm
Dimensions	Approx. 267 × 359 × 287 mm
Weight (kg)	Approx. 11.5 kg
Packaging weight	Approx. 13.5 kg
Main applications	Conveyors, rollers, feeders, printing, paper, textile, machine tools and processing equipment
Main advantage	45 A / 25 HP-class industrial DC motor control
Main operating type	Two-quadrant non-regenerative
Installation	Protected electrical cabinet

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53. Final Product Assessment

The 20P21AD045RA0NNN is a high-capacity Frame A DC drive designed for industrial motor-control applications requiring approximately 45 A armature current and 25 HP / 18.5 kW motor capacity.

Its combination of 460/480 VAC-class three-phase input, 45 A armature rating, six-pulse input, regulated field supply, two-quadrant operation, IP20 enclosure, conformal coating, flexible I/O and feedback capability makes it a practical choice for a wide range of industrial DC motor systems.

The model is especially useful when an existing DC motor is still mechanically and electrically suitable, but the original drive needs to be replaced.

Instead of converting the entire machine to an AC motor system, a compatible DC drive can allow the existing motor and mechanical equipment to remain in service.

This can reduce engineering changes, installation work, commissioning time and mechanical modifications.

The 45 A rating makes the model particularly suitable for 25 HP-class industrial machinery, including conveyors, rollers, feeders, paper-processing equipment, textile machinery, printing machinery, machine tools and other production equipment.

The main limitation is its non-regenerative, two-quadrant design.

For a conventional conveyor or feeder, this may be completely appropriate.

For a high-inertia winder, unwinder, hoist or machine with frequent regenerative braking, the application should be evaluated for regenerative energy and a regenerative configuration should be considered.

From an engineering selection perspective, the 20P21AD045RA0NNN is best positioned as a 45 A, 25 HP-class industrial PowerFlex DC drive for conventional two-quadrant applications, especially where maintaining an existing DC motor and machine structure is important.

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54. Final Quick Reference Table

Category	Details
Model	20P21AD045RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Drive type	Digital DC Drive
Input	460/480 VAC class, 3-phase
Input type	6-pulse
Armature current	45 A
Motor rating	25 HP
Motor rating	Approx. 18.5 kW
Operating mode	Two-quadrant
Regenerative	Non-regenerative
Field supply	Single-phase regulated
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Frame	Frame A
Cooling	Air cooled
Conformal coating	Yes
Operator interface	Blank plate
Communication module	None
Digital inputs	8
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback	Tachometer / encoder capable
Dimensions	Approx. 267 × 359 × 287 mm
Weight (kg)	Approx. 11.5 kg
Packaging weight	Approx. 13.5 kg
Main application	Industrial DC motor control
Main application type	Conventional motoring
Typical machinery	Conveyors, rollers, feeders, printing, paper, textile and processing equipment
Lower-current alternative	20P21AD035RA0NNN
Higher-current alternative	20P21AD052RA0NNN
Regenerative alternative	20P41AD045RA0NNN
Main selection advantage	45 A / 25 HP-class DC motor capacity in a compact Frame A package