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20P21AD035RA0NNN — PowerFlex DC Drive

Detailed Specifications, Product Introduction, Applications, Advantages, Series Information and Related Models

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1. Product Overview

The 20P21AD035RA0NNN is a 35 A PowerFlex DC drive designed for industrial applications that require controlled operation of DC motors.

This model is rated for a 480 VAC-class, three-phase input, with a 35 A armature current rating and a nominal 20 HP / approximately 15 kW motor power class.

It is a two-quadrant, non-regenerative DC drive, making it suitable for conventional industrial machinery where controlled forward and reverse operation may be required, but continuous regenerative braking is not the primary operating requirement.

The drive uses a 6-pulse input configuration, an IP20 / NEMA/UL Type Open enclosure, and Frame A construction. It is supplied with a blank front cover rather than a local HIM operator interface, and the standard configuration does not include a communication module.

The model also incorporates conformal coating, which provides additional protection to the electronic circuitry in suitable industrial environments.

With its 35 A current capacity, the drive is positioned above the smaller 10 A, 14 A, 19 A and 27 A versions in the same general DC-drive family and is suitable for medium-to-larger industrial DC motor applications.

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2. Brand and Series

Item	Specification
Brand	Allen-Bradley
Product family	PowerFlex
Series	PowerFlex DC
Product category	Industrial DC Drive
Model	20P21AD035RA0NNN
Drive type	DC motor drive
Current class	35 A
Motor power class	20 HP / approximately 15 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
Operator interface	Blank plate / no standard HIM
Communication module	None included as standard

The PowerFlex DC series is intended for industrial DC motor control, particularly where an existing DC motor and mechanical system remain in service.

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3. Main Technical Specifications

Parameter	Specification
Model	20P21AD035RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Product type	Industrial DC Drive
Motor type	DC motor
Input voltage	480 VAC class
Nominal input voltage	460 VAC
Input frequency	50/60 Hz
Input phase	3-phase
Input type	6-pulse
Armature current	35 A
Motor power	20 HP
Motor power	Approximately 15 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	Air cooled
Conformal coating	Yes
HIM	Blank plate / no HIM
Communication	No communication module
Digital inputs	8 × 24 VDC
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback capability	DC tachometer / encoder capable
Approx. height	425 mm
Approx. width	279 mm
Approx. depth	425 mm
Approx. dimensions	425 × 279 × 425 mm
Approx. weight (kg)	Approx. 14.2 kg
Approx. weight	31.3 lb
Mounting arrangement	Cabinet / panel installation
Cooling arrangement	Forced-air / air cooled
Typical motor capacity	20 HP-class DC motor

The dimensions and weight above are suitable for preliminary product comparison and cabinet planning. Actual installation drawings and required clearances should be considered for final mechanical design.

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4. Product Introduction

The 20P21AD035RA0NNN is designed to provide controlled electrical power to compatible industrial DC motors.

Its main purpose is to convert incoming three-phase AC power into controlled DC power for the motor armature while providing control functions for motor speed, current, acceleration, deceleration and operating direction.

The 35 A current rating gives this model a useful position for applications where a smaller DC drive is insufficient but a substantially larger industrial drive is unnecessary.

A 20 HP-class DC motor can be found in many types of industrial machinery, including conveyors, material-handling equipment, rollers, feeders, machine tools, processing equipment and production machinery.

The drive can also be useful in retrofit projects where an existing DC motor remains mechanically sound and the machine operator wants to replace or modernize the drive without completely redesigning the machine.

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5. 35 A Armature Rating

The most important electrical characteristic of the 20P21AD035RA0NNN is its 35 A armature current rating.

The armature current rating determines the amount of current the drive can deliver to the motor under the applicable operating conditions.

Compared with a 27 A model, the 35 A version provides additional capacity for larger motors and heavier loads.

This makes it appropriate for applications in the approximate range of:

20 HP / 15 kW / 35 A-class DC motor systems

However, motor selection should not be based only on horsepower.

The following motor nameplate information should always be checked:

• Armature voltage
• Armature current
• Field voltage
• Field current
• Horsepower
• Base speed
• Maximum speed
• Feedback type
• Duty cycle

The actual motor armature current is especially important when determining whether a 35 A drive is suitable.

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6. 20 HP / Approximately 15 kW Power Class

The drive is intended for a 20 HP-class DC motor, equivalent to approximately 15 kW.

This makes it suitable for larger industrial machinery than the 10 HP and 15 HP configurations.

Typical machinery in this range may include:

• Heavy conveyors
• Industrial rollers
• Material feeders
• Processing equipment
• Printing equipment
• Textile machinery
• Paper machinery
• Machine tools
• Material-handling systems
• Production-line machinery

The exact motor compatibility depends on the motor’s electrical characteristics and the application’s operating conditions.

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7. Three-Phase 480 VAC Input

The 20P21AD035RA0NNN is designed for a 480 VAC-class three-phase industrial supply.

The nominal system voltage associated with this configuration is approximately 460 VAC.

Three-phase industrial power makes this drive suitable for conventional manufacturing and process-control environments.

Typical installations may be found in:

• Manufacturing plants
• Processing facilities
• Industrial production lines
• Material-handling systems
• Machine shops
• Paper-processing facilities
• Textile facilities
• Printing environments
• Metal-processing machinery

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8. Six-Pulse Input Configuration

The drive uses a 6-pulse input configuration.

This is a conventional architecture for industrial DC drives.

The six-pulse arrangement is widely used in industrial power conversion because it provides a practical method of converting three-phase AC input power into controlled DC power.

For replacement applications, the six-pulse configuration is particularly relevant when the original machine already uses a conventional DC drive architecture.

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9. Two-Quadrant Operation

The 20P21AD035RA0NNN is a two-quadrant drive.

This means it is designed primarily for controlled motoring operation rather than full four-quadrant regenerative operation.

Two-quadrant operation can be suitable for machinery where the motor operates primarily in a motoring condition.

Typical applications include:

• Conveyors
• Feeders
• Pumps
• Fans
• Roll drives
• Processing equipment
• Machine tools
• Production machinery

If the application repeatedly forces the motor to absorb large amounts of mechanical energy during braking, a regenerative configuration should be considered instead.

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10. Non-Regenerative Operation

This model is a non-regenerative DC drive.

The distinction is important because not every DC motor application has the same braking requirements.

For a conventional conveyor, for example, the motor normally supplies mechanical power to move the load.

For a high-inertia winder or hoist, however, the mechanical load can drive the motor during deceleration or lowering.

In such applications, energy can flow back toward the drive.

Therefore, applications involving substantial regenerative energy should be evaluated carefully before selecting the non-regenerative 20P21AD035RA0NNN.

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11. Regenerative vs. Non-Regenerative Applications

Application Type	20P21AD035RA0NNN Suitability
Standard conveyor	Excellent
Material feeder	Excellent
Roller drive	Very suitable
Pump	Suitable
Fan	Suitable
General production machinery	Very suitable
Printing equipment	Suitable
Textile machinery	Suitable
High-inertia winder	Requires evaluation
Unwinder	Requires evaluation
Hoist	Requires detailed evaluation
Frequent regenerative braking	Not the preferred configuration
Four-quadrant operation	Use a regenerative configuration instead

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12. Field Supply

The model uses a single-phase regulated field supply.

The field circuit is an important part of a DC motor control system.

The field establishes the motor’s magnetic field, which directly influences the motor’s operating characteristics.

During commissioning, the following values should be checked against the motor:

Motor Field Parameter	Importance
Field voltage	Must match the motor requirement
Field current	Must remain within the permitted range
Field wiring	Must be correctly connected
Field loss protection	Should be configured appropriately
Field weakening	Must be evaluated for the motor
Maximum speed	Must remain within motor limits

Correct field configuration is essential for reliable operation.

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13. Feedback Capability

The PowerFlex DC platform supports feedback arrangements such as:

• DC tachometer feedback
• Encoder feedback

Feedback can be especially useful when the machine needs stable speed under changing load conditions.

For example, if the load on a conveyor changes suddenly, the motor’s natural speed can vary.

A feedback system allows the drive to compare actual motor speed with the commanded speed and make appropriate corrections.

This can improve:

• Speed regulation
• Process consistency
• Product quality
• Acceleration control
• Load response
• Machine performance

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14. Standard I/O

The drive provides a useful collection of standard I/O.

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

This allows the drive to be integrated with conventional industrial control systems.

A PLC can provide start, stop, speed and direction commands through the available control interfaces.

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15. No Standard Communication Module

The standard 20P21AD035RA0NNN configuration does not include a communication module.

This configuration can be appropriate when the drive is controlled through hardwired I/O.

A conventional control architecture might use:

PLC → Digital/Analog I/O → DC Drive → DC Motor

This approach can be useful for existing machines where the original control system already uses discrete signals and analog references.

Where network-based control is required, an appropriate communication option can be evaluated separately.

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16. Blank Front Plate

The model is supplied with a blank plate rather than a standard local HIM operator interface.

This makes sense for systems where the machine operator does not need to control the drive directly from a local keypad.

Instead, the drive can be controlled through:

• PLC
• Operator station
• Pushbuttons
• External analog reference
• Machine controller
• Industrial control system

This configuration can also reduce unnecessary operator-interface hardware when the drive is installed inside a control cabinet.

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17. IP20 Enclosure

The drive uses an IP20 enclosure.

This means it is intended for installation in a protected electrical cabinet or suitable industrial enclosure.

It is not intended to be installed directly in an exposed outdoor environment.

The installation should protect the drive against:

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

The cabinet should also provide adequate ventilation and heat removal.

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18. Conformal Coating

The model includes conformal coating.

Conformal coating provides an additional protective layer over electronic circuitry.

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

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

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

The IP20 enclosure still requires a properly protected installation.

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19. Frame A Construction

The 20P21AD035RA0NNN uses Frame A construction.

Frame size is important when planning a replacement or designing a control cabinet.

It affects:

• Mounting arrangement
• Cabinet space
• Cooling requirements
• Cable routing
• Maintenance access
• Service clearance
• Terminal access

The approximate dimensions are:

425 mm × 279 mm × 425 mm

The approximate weight is:

14.2 kg

These values should be considered when evaluating an existing cabinet.

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20. Dimensions and Weight

Mechanical Parameter	Specification
Model	20P21AD035RA0NNN
Frame	Frame A
Height	Approx. 425 mm
Width	Approx. 279 mm
Depth	Approx. 425 mm
Dimensions	Approx. 425 × 279 × 425 mm
Weight (kg)	Approx. 14.2 kg
Approx. weight	31.3 lb
Enclosure	IP20
Enclosure type	NEMA/UL Type Open
Cooling	Air cooled
Installation	Protected cabinet
Mounting	Panel/cabinet installation

For a final cabinet layout, additional clearance should be provided around the drive for ventilation, wiring and maintenance.

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21. Main Applications

21.1 Conveyor Systems

The 35 A capacity makes the drive suitable for a wide range of industrial conveyors.

Possible applications include:

• Belt conveyors
• Roller conveyors
• Assembly conveyors
• Transfer conveyors
• Packaging conveyors
• Production-line conveyors
• Material-handling conveyors

The drive can provide controlled acceleration and deceleration, which can reduce mechanical shock during starting and stopping.

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21.2 Roller Drives

Roller applications often require controlled speed.

The drive can be used with suitable DC motors for:

• Feed rollers
• Process rollers
• Paper rollers
• Textile rollers
• Material-handling rollers
• Production rollers

The feedback capability can be particularly useful when accurate speed regulation is required.

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21.3 Printing Machinery

DC motors have historically been used in many printing and web-processing machines.

The 20P21AD035RA0NNN can be considered for suitable DC motor applications such as:

• Printing rollers
• Paper feeders
• Web handling
• Auxiliary drives
• Material feed systems
• Processing rollers

For tension-critical systems, braking and regenerative requirements should be evaluated separately.

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21.4 Paper Processing

The drive can be applied to suitable DC motors in:

• Paper feed systems
• Roll drives
• Processing machines
• Coating equipment
• Material transport systems
• Rewind-related machinery

Consistent motor speed can be important for maintaining product quality.

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21.5 Textile Machinery

Textile machinery can require stable and adjustable motor speed.

Potential applications include:

• Textile rollers
• Feed systems
• Spinning equipment
• Winding machinery
• Material transport
• Processing lines

The suitability of a non-regenerative configuration depends on the actual load behavior.

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21.6 Metal Processing

The 20 HP-class rating makes the drive appropriate for many medium-sized metal-processing applications.

Examples include:

• Feed rollers
• Material transfer systems
• Processing equipment
• Grinding-machine auxiliaries
• Cutting machinery
• Production equipment
• Material-handling systems

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21.7 Machine Tools

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

Possible applications include:

• Grinding machines
• Feed mechanisms
• Cutting machinery
• Specialized machine tools
• Production equipment
• Material-processing machinery

Where precise speed control is important, feedback selection should receive particular attention.

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21.8 Pumps and Fans

The drive can also be used for suitable DC motor-driven pumps and fans.

Speed control can be useful when the process does not always require full motor speed.

For pumps, motor speed may be used to adjust process flow.

For fans, reducing speed can reduce unnecessary energy consumption.

The motor and load characteristics should always be evaluated before selecting the drive.

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22. Advantages of the 20P21AD035RA0NNN

22.1 35 A Current Capacity

The 35 A armature rating is one of the most significant advantages.

It provides additional current capacity compared with smaller DC drive models.

This makes the model suitable for approximately 20 HP-class DC motors.

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22.2 20 HP / 15 kW Capacity

The 20 HP rating places the drive in a useful medium industrial power range.

It is suitable for machinery requiring more power than typical 5 HP, 7.5 HP, 10 HP and 15 HP DC drive applications.

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22.3 Industrial 480 VAC-Class Input

The three-phase 480 VAC-class input makes it compatible with common industrial electrical systems.

This is useful for production plants where three-phase industrial power is already available.

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22.4 Regulated Field Supply

The regulated field supply supports controlled operation of compatible DC motors.

This is important for maintaining appropriate motor operating characteristics.

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22.5 Feedback Capability

Tachometer and encoder feedback options provide flexibility for speed-sensitive applications.

This can be particularly useful in:

• Roll drives
• Feed systems
• Printing machines
• Textile machines
• Processing machinery

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22.6 Flexible I/O

The combination of digital and analog I/O makes the drive suitable for hardwired machine control.

This is useful when a PLC or external control system already exists.

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22.7 Conformal Coating

Conformal coating adds another layer of protection to the electronics.

This can be advantageous in controlled industrial environments where airborne contamination and humidity are concerns.

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22.8 Compact Frame A Construction

For a 35 A / 20 HP-class DC drive, the Frame A design provides a relatively compact mechanical arrangement.

This can be useful when replacing an older drive in an existing cabinet.

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22.9 No Unnecessary Operator Interface

The blank-plate configuration is appropriate for externally controlled machinery.

The drive can be integrated into a machine where the operator interacts with a central control panel rather than directly with the drive.

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23. Main Advantages Summary

Feature	Practical Advantage
35 A armature rating	Suitable for larger DC motors
20 HP / 15 kW class	Suitable for medium industrial machinery
460/480 VAC class	Suitable for common industrial power systems
6-pulse input	Conventional DC-drive architecture
Two-quadrant operation	Suitable for standard motoring applications
Non-regenerative design	Well suited to conventional loads
Regulated field supply	Supports controlled DC motor operation
Feedback capability	Useful for improved speed regulation
Flexible I/O	Easy integration with hardwired control systems
Conformal coating	Additional electronic protection
IP20 enclosure	Suitable for protected cabinet installation
Frame A	Compact industrial construction
Blank plate	Suitable for external machine control

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

The following five models are useful comparison choices when selecting around the 20P21AD035RA0NNN.

Model	Series	Voltage Class	Armature Current	Approx. Power	Operation	Regeneration	Dimensions	Weight (kg)
20P21AD019RA0NNN	PowerFlex DC	460/480 VAC	19 A	10 HP / 7.5 kW	Two-quadrant	No	Frame-dependent	Approx. 14
20P21AD027RA0NNN	PowerFlex DC	460/480 VAC	27 A	15 HP / 11 kW	Two-quadrant	No	Approx. 425 × 279 × 425 mm	Approx. 14.2
20P21AD035RA0NNN	PowerFlex DC	460/480 VAC	35 A	20 HP / 15 kW	Two-quadrant	No	Approx. 425 × 279 × 425 mm	Approx. 14.2
20P21AD045RA0NNN	PowerFlex DC	460/480 VAC	45 A	25 HP class	Two-quadrant	No	Frame-dependent	Frame-dependent
20P41AD035RA0NNN	PowerFlex DC	460/480 VAC	35 A	20 HP / 15 kW	Four-quadrant	Yes	Frame-dependent	Frame-dependent

The 20P41 configuration is particularly relevant when regenerative operation is required.

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25. Recommended Model 1 — 20P21AD019RA0NNN

The 20P21AD019RA0NNN is a lower-current model in the same general product family.

Its approximate rating is:

19 A / 10 HP / 7.5 kW

It is appropriate when the motor’s current requirement is lower than that of the 35 A model.

Typical applications include:

• Medium conveyors
• Feeders
• Rollers
• Small processing machines
• Printing equipment
• Textile machinery

This model is useful when selecting a smaller drive can reduce system size and cost.

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26. Recommended Model 2 — 20P21AD027RA0NNN

The 20P21AD027RA0NNN is the next smaller current class.

Its approximate rating is:

27 A / 15 HP / 11 kW

It is a particularly useful alternative when a 20 HP motor is not required.

The 27 A model can be considered for:

• Medium conveyors
• Feed systems
• Roll drives
• Printing machinery
• Textile machinery
• General industrial machinery

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27. Recommended Model 3 — 20P21AD045RA0NNN

The 20P21AD045RA0NNN provides approximately 45 A of armature current.

It represents the next higher current class above the 35 A model.

Its approximate motor power class is:

25 HP

It is appropriate when:

• Motor current exceeds 35 A
• Motor power is greater than 20 HP
• The machine has a heavier load
• Additional current capacity is required

Typical applications can include:

• Large conveyors
• Heavy rollers
• Processing equipment
• Larger feeders
• Industrial production machinery

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28. Recommended Model 4 — 20P21AD052RA0NNN

The 20P21AD052RA0NNN is a higher-current configuration of the same general DC-drive family.

Its approximate current rating is:

52 A

Its approximate motor power class is:

30 HP

This model is more appropriate for larger industrial machinery where the 35 A and 45 A versions do not provide enough capacity.

Potential applications include:

• Heavy-duty conveyors
• Large rollers
• Processing machinery
• Material-handling equipment
• High-load production machinery

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29. Recommended Model 5 — 20P41AD035RA0NNN

The 20P41AD035RA0NNN is an important related model when the application requires regenerative operation.

It provides approximately:

35 A / 20 HP / 15 kW

but uses a regenerative architecture.

It can therefore be considered for applications such as:

• Winders
• Unwinders
• High-inertia machines
• Hoisting equipment
• Frequent braking applications
• Four-quadrant operation

If the application requires the motor to absorb and return substantial mechanical energy during operation, a regenerative model is generally a more appropriate direction than the non-regenerative 20P21 configuration.

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30. Five Popular Models from the Same Brand

The following models provide useful comparison points within the broader drive portfolio.

Some are DC drives and others are AC drives.

AC-drive models should be considered modernization alternatives rather than direct electrical replacements because they normally require compatible AC motors.

Model	Product Family	Drive Type	Voltage Class	Current / Power Class	Typical Application	Dimensions	Weight (kg)
20P21AD027RA0NNN	PowerFlex DC	DC Drive	460/480 VAC	27 A / 15 HP	Medium DC machinery	Approx. 425 × 279 × 425 mm	Approx. 14.2
20P41AD035RA0NNN	PowerFlex DC	Regenerative DC Drive	460/480 VAC	35 A / 20 HP	Regenerative DC machinery	Frame-dependent	Frame-dependent
25B-D017N104	PowerFlex 525	AC Drive	380–480 VAC	Approx. 17 A class	General AC motor control	Compact frame	Approx. 2–3
25C-D017N104	PowerFlex 527	AC Drive	380–480 VAC	Approx. 17 A class	Networked AC motor control	Compact frame	Approx. 2–3
20F1AG077AA0NNNNN	PowerFlex 753	AC Drive	380–480 VAC	Higher-power class	Industrial AC applications	Frame-dependent	Frame-dependent

The AC models in this table are useful when considering a complete motor-and-drive modernization rather than a direct DC-drive replacement.

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31. Comparison Between DC and AC Drive Modernization

Feature	20P21AD035RA0NNN	Modern AC Drive
Motor type	DC motor	AC motor
Drive output	Controlled DC	Variable-frequency AC
Existing DC motor retained	Yes	Normally no
Direct DC replacement	Yes, when correctly matched	No
Motor replacement required	Usually no	Normally yes
Existing mechanical system	Often retained	Often retained
Existing feedback	May be retained	May require redesign
Retrofit complexity	Lower	Higher
Control redesign	Usually limited	Potentially substantial
Main benefit	Preserve existing DC architecture	Modernize to AC motor technology

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32. Retrofit Applications

One of the strongest practical uses for the 20P21AD035RA0NNN is industrial retrofit work.

Many machines remain mechanically useful long after their original electronic drives become obsolete or unreliable.

Replacing the drive can sometimes allow the plant to retain:

• Existing DC motor
• Gearbox
• Coupling
• Mechanical transmission
• Rollers
• Conveyor structure
• Existing machine frame
• PLC
• Operator station
• Feedback device

This can significantly reduce the amount of mechanical modification required.

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33. Typical Control Architecture

A typical industrial arrangement can be represented as:

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

If feedback is required:

DC Motor → Tachometer / Encoder → Drive

The machine controller can provide:

• Start command
• Stop command
• Speed reference
• Direction command
• Enable signal

The drive can then manage the motor’s electrical operation.

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34. Speed Control

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

The motor can receive a controlled speed reference through the appropriate input or external control system.

Possible speed-reference methods include:

• Analog reference
• PLC-generated reference
• Preset speed
• External operator station
• Process controller
• Automation system

When feedback is used, the drive can regulate motor speed more effectively under changing load conditions.

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35. Acceleration and Deceleration

Controlled acceleration is important for many industrial machines.

If a large DC motor is connected directly to a machine without controlled acceleration, the sudden application of torque can cause:

• Mechanical shock
• Belt stress
• Gearbox stress
• Product instability
• Excessive current demand

The drive can provide controlled acceleration and deceleration according to the machine configuration.

However, deceleration behavior must be evaluated carefully because the non-regenerative architecture has limitations when the mechanical load becomes an energy source.

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36. Torque Control

The armature current of a DC motor is closely related to motor torque.

The 35 A capacity therefore provides substantial torque capability for compatible 20 HP-class DC motors.

This is useful for applications involving:

• Starting loads
• Material handling
• Feed mechanisms
• Roll drives
• Conveyor systems
• Processing equipment
• Machine tools

The current limit should always be configured according to the motor’s actual rating.

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37. Important Motor Selection Parameters

Before selecting the drive for a motor, the following parameters should be recorded.

Motor Parameter	Recommended Check
Armature voltage	Must be compatible with drive output
Armature current	Should be within the 35 A drive rating
Field voltage	Must match the field supply requirement
Field current	Must be compatible with the field circuit
Horsepower	Approximately 20 HP class
Base speed	Verify against application
Maximum speed	Verify against motor limit
Feedback	Check tachometer/encoder type
Duty cycle	Check continuous/intermittent requirements
Starting torque	Check application requirement
Braking	Determine regenerative requirement
Motor insulation	Evaluate motor condition
Brush condition	Check before commissioning
Commutator	Inspect before commissioning

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38. Cabinet Design Considerations

The approximate drive dimensions are:

425 mm height

279 mm width

425 mm depth

The approximate weight is:

14.2 kg

The cabinet should provide additional room for:

• Power cables
• Control wiring
• Feedback wiring
• Ventilation
• Mounting hardware
• Service access
• Heat dissipation
• Terminal access

The drive should not be mounted so closely to other heat-producing components that the cooling airflow is restricted.

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39. Maintenance Considerations

A reliable DC-drive installation depends on both the drive and the motor.

Regular inspection should include:

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

For older DC motors, brush and commutator condition can be especially important.

A new drive cannot compensate for a severely worn or contaminated motor.

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40. Selection Comparison by Current

Model	Current Rating	Approx. Power Class	Typical Position
20P21AD010RA0NNN	10 A	5 HP	Smaller motor
20P21AD014RA0NNN	14 A	7.5 HP	Small/medium motor
20P21AD019RA0NNN	19 A	10 HP	Medium motor
20P21AD027RA0NNN	27 A	15 HP	Medium/large motor
20P21AD035RA0NNN	35 A	20 HP	Larger motor
20P21AD045RA0NNN	45 A	25 HP	Larger industrial motor
20P21AD052RA0NNN	52 A	30 HP	Heavy-duty motor

The 35 A / 20 HP model is therefore a useful choice when a 27 A drive does not provide sufficient capacity but the machine does not require a significantly larger current class.

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41. Quick Comparison of Related Models

Model	Current	Approx. Power	Regenerative	Recommended Use
20P21AD019RA0NNN	19 A	10 HP	No	Smaller DC motor
20P21AD027RA0NNN	27 A	15 HP	No	Medium DC motor
20P21AD035RA0NNN	35 A	20 HP	No	Main model
20P21AD045RA0NNN	45 A	25 HP	No	Larger DC motor
20P41AD035RA0NNN	35 A	20 HP	Yes	Regenerative application

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42. Recommended Application Matching

Application	Recommended Model Direction
10 HP conventional DC conveyor	20P21AD019RA0NNN
15 HP conventional DC machine	20P21AD027RA0NNN
20 HP conventional DC machine	20P21AD035RA0NNN
25 HP conventional DC machine	20P21AD045RA0NNN
20 HP regenerative machine	20P41AD035RA0NNN
Heavy high-inertia load	Regenerative configuration should be evaluated
Simple conveyor	Non-regenerative configuration
Standard feeder	Non-regenerative configuration
Winder/unwinder	Regenerative requirements should be evaluated
Hoist	Four-quadrant/regenerative requirements should be evaluated

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43. Important Advantages for Industrial Users

The 20P21AD035RA0NNN offers several practical advantages.

First, its 35 A current capacity provides a comfortable range for many 20 HP-class DC motors.

Second, its 480 VAC-class three-phase input fits common industrial electrical systems.

Third, the two-quadrant non-regenerative architecture is relatively straightforward for conventional motoring applications.

Fourth, the regulated field supply allows appropriate control of the motor field circuit.

Fifth, the feedback capability allows the drive to be used in applications where speed regulation is more demanding.

Sixth, the standard I/O provides a practical way to integrate the drive with existing machine-control systems.

Seventh, the conformal coating provides an additional level of protection for the electronics in appropriate industrial environments.

Finally, the Frame A construction provides a relatively compact mechanical package for its power class.

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44. Product Specification Summary

Specification	Value
Catalog Number	20P21AD035RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Drive type	DC Drive
Input voltage	480 VAC class
Nominal voltage	460 VAC
Input phase	3-phase
Input type	6-pulse
Armature current	35 A
Motor power	20 HP
Motor power	Approx. 15 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 included
Digital inputs	8 × 24 VDC
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback	Tachometer / encoder capable
Height	Approx. 425 mm
Width	Approx. 279 mm
Depth	Approx. 425 mm
Dimensions	Approx. 425 × 279 × 425 mm
Weight (kg)	Approx. 14.2 kg
Approx. weight	31.3 lb
Main applications	Conveyors, rollers, feeders, printing, textile, paper, machine tools, processing machinery
Main strength	35 A / 20 HP-class DC motor control

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45. Final Product Assessment

The 20P21AD035RA0NNN is a strong choice for industrial applications requiring a 35 A, 20 HP-class DC motor drive.

Its combination of 480 VAC-class three-phase input, 35 A armature capacity, 20 HP / approximately 15 kW motor rating, two-quadrant operation, regulated field supply, flexible I/O, feedback capability, IP20 construction and conformal coating makes it suitable for a broad range of industrial machinery.

The model is particularly valuable for machines where an existing DC motor remains in service and the objective is to maintain the existing mechanical arrangement while using a capable modern DC drive.

Typical applications include conveyors, rollers, feeders, printing machinery, paper-processing equipment, textile machinery, machine tools, material-handling systems and general industrial production equipment.

The most important selection point is the 35 A armature rating. The motor’s actual nameplate current, armature voltage, field voltage and field current should be checked before installation.

For applications with a smaller motor, the 19 A or 27 A versions may provide a better match.

For larger motors, the 45 A or 52 A versions may be more appropriate.

For applications where substantial energy is returned to the drive during braking, a regenerative 35 A configuration should be considered rather than the non-regenerative 20P21 configuration.

From a practical engineering perspective, the 20P21AD035RA0NNN is best viewed as a medium-power industrial DC motor controller for conventional two-quadrant applications, particularly where dependable speed and torque control are required without converting the existing machine from DC motor technology to AC motor technology.

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46. One-Table Quick Reference

Category	Details
Model	20P21AD035RA0NNN
Brand	Allen-Bradley
Series	PowerFlex DC
Product category	Industrial DC Drive
Input	460/480 VAC class, 3-phase
Input configuration	6-pulse
Armature rating	35 A
Motor rating	20 HP / approximately 15 kW
Operating mode	Two-quadrant
Regenerative	Non-regenerative
Field	Single-phase regulated
Enclosure	IP20 / NEMA/UL Type Open
Frame	Frame A
Cooling	Air cooled
Conformal coating	Yes
Operator interface	Blank plate
Communication	None included
Digital inputs	8
Digital outputs	4
Analog inputs	2
Analog outputs	3
Feedback	Tachometer / encoder capable
Dimensions	Approx. 425 × 279 × 425 mm
Weight (kg)	Approx. 14.2 kg
Main application	Industrial DC motor control
Suitable machinery	Conveyors, rollers, feeders, printing, paper, textile, machine tools and processing equipment
Main advantage	High-capacity 35 A / 20 HP-class DC motor control
Best application type	Conventional industrial motoring
Alternative for smaller motor	20P21AD027RA0NNN
Alternative for larger motor	20P21AD045RA0NNN
Alternative for regenerative application	20P41AD035RA0NNN