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20P21AD667RA0NNN PowerFlex DC Drive

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

The 20P21AD667RA0NNN is a high-power DC drive designed for demanding industrial motor-control applications. It belongs to the PowerFlex DC series and is intended for large DC motors requiring controlled speed, torque, acceleration and deceleration.

This model is rated at 667 A and approximately 400 HP / 298 kW under the applicable 380–480 VAC three-phase drive class. It uses a non-regenerative, two-quadrant configuration, with an IP20 / NEMA/UL Type Open enclosure, Frame C construction, conformal coating, and a blank-plate/no-HIM configuration.

Because this is a large industrial drive, it is fundamentally different from the small-frame 2 HP to 10 HP models. It is intended for large production machinery, heavy material handling, processing lines, large conveyors, winding systems and other applications where a high-current DC motor remains an important part of the machine.

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1. Basic Product Information

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2. Product Series

The 20P21AD667RA0NNN belongs to the PowerFlex DC series.

The PowerFlex DC family is designed for industrial applications using DC motors. It covers a very broad range of power levels, from relatively small motors to extremely high-current industrial DC motor applications.

The target model sits toward the high-power end of the series.

For the 380–480 VAC three-phase class, the series includes ratings ranging from approximately 1.5 kW / 2 HP / 4.1 A through much higher-current configurations.

The 667 A model represents the 400 HP / 298 kW class and uses Frame C mechanical construction.

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3. Detailed Electrical Parameters

The 667 A output rating is the most important characteristic of this model.

It allows the drive to control a substantially larger DC motor than the smaller models in the same family.

The 400 HP rating corresponds to approximately 298 kW, placing this drive in a heavy industrial power range.

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4. Mechanical Parameters

For an actual cabinet design, the exact mechanical drawing should be used for the final height, width, depth and mounting-hole dimensions.

The approximately 78.3 kg product weight should also be distinguished from the shipping weight, which can be higher because packaging and shipping materials are included.

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5. Product Introduction

The 20P21AD667RA0NNN is a high-current digital DC motor drive intended to provide controlled operation of large industrial DC motors.

At 667 A, this drive is designed for applications where the motor requires substantial armature current.

Large DC motors are still found in many industrial machines because they can provide excellent torque characteristics and a broad controllable speed range.

Instead of replacing an entire machine simply because its original DC drive is obsolete, a modern DC drive can provide a practical modernization path while allowing the existing motor and mechanical equipment to remain in service.

The 20P21AD667RA0NNN is particularly appropriate for this type of modernization.

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6. 400 HP / 298 kW Power Class

The drive’s 400 HP rating places it firmly in the heavy industrial category.

A 400 HP motor is approximately equivalent to 298 kW.

This is no longer a small machine-drive application.

It can be associated with:

• Large conveyors.
• Large rolling machinery.
• Heavy-duty material processing.
• Industrial winding equipment.
• Large printing machinery.
• Steel-processing machinery.
• Large production lines.
• Large machine-tool systems.
• Mining-related material handling.
• Large process equipment.

The final motor suitability must always be established using the actual motor nameplate current, voltage, field requirements, duty cycle and application load.

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7. 667 A Output Current

The 667 A current rating is what distinguishes this model from the smaller PowerFlex DC configurations.

Current is particularly important for DC motors because armature current has a direct relationship with motor torque.

A high-current drive can therefore support the torque requirements of large mechanical loads.

The drive must be correctly matched to:

• Motor armature current.
• Motor armature voltage.
• Motor field voltage.
• Motor field current.
• Motor base speed.
• Maximum motor speed.
• Mechanical load.
• Duty cycle.
• Acceleration requirements.
• Deceleration requirements.

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8. Two-Quadrant Operation

The 20P21AD667RA0NNN is a two-quadrant drive.

This is an important feature when selecting the drive.

Two-quadrant operation is appropriate for many conventional DC motor applications where the motor operates in one primary direction and regenerative operation is not continuously required.

Typical applications include machinery where the motor:

• Accelerates.
• Runs at a controlled speed.
• Decelerates through an appropriate braking arrangement.
• Operates primarily in one direction.

For applications requiring continuous regeneration or four-quadrant operation, a regenerative version should be evaluated instead.

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9. Non-Regenerative Configuration

This particular catalog number is a non-regenerative configuration.

That means the drive is not designed as a regenerative four-quadrant drive that continuously returns braking energy to the AC supply.

This makes the model more appropriate for conventional loads.

Examples include:

• Constant-direction conveyors.
• Process rollers.
• Certain fans and pumps.
• Large production lines.
• Material-handling equipment.
• Machinery with relatively moderate braking requirements.

For applications with frequent regenerative braking, rapid reversing or overhauling loads, a regenerative PowerFlex DC configuration would generally be a better technical comparison.

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10. Regulated Field Supply

The drive includes a single-phase regulated field supply.

A DC motor normally contains two fundamental electrical systems:

1. The armature circuit.
2. The field circuit.

The armature circuit has a major influence on motor torque and operating behavior.

The field circuit establishes the magnetic field required for motor operation.

The regulated field converter allows the drive system to manage the motor field in a controlled manner.

This is especially important for large DC motors where field behavior has a major impact on the overall machine.

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11. Advanced Speed Control

The PowerFlex DC architecture supports advanced speed regulation.

This is particularly useful in large industrial machines where motor speed must remain stable despite changes in mechanical load.

For example, a large production roller may experience changing material tension.

Without effective speed regulation, those load changes can cause unwanted speed variation.

A properly configured DC drive can compensate for such changes and maintain much more consistent operation.

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12. Feedback Capability

The PowerFlex DC family supports feedback arrangements such as:

• DC tachometer feedback.
• Encoder feedback.

Feedback is particularly valuable in high-performance applications.

A feedback device measures the actual motor speed.

The drive compares actual speed against the desired speed and adjusts the motor control accordingly.

This can provide significantly better speed regulation than an open-loop arrangement.

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13. Typical Industrial Applications

13.1 Steel Processing

Large DC motors have historically been used extensively in steel-processing machinery.

Applications can include:

• Rolling equipment.
• Material-handling sections.
• Large rollers.
• Processing lines.
• Auxiliary drives.

The high-current capability of the 20P21AD667RA0NNN makes it relevant to this class of machinery.

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13.2 Large Conveyors

Large conveyors can require substantial starting torque.

This is particularly true when the conveyor is heavily loaded.

A DC motor and high-current DC drive can provide controlled acceleration and torque.

The drive can help prevent sudden mechanical loading on:

• Gearboxes.
• Couplings.
• Shafts.
• Conveyor belts.
• Bearings.

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13.3 Large Winding Equipment

Winding systems require carefully controlled motor speed and torque.

The load characteristics can change significantly as the material roll diameter changes.

A high-power DC drive can be used with appropriate feedback and tension-control architecture to provide stable motor operation.

Potential applications include:

• Paper winding.
• Metal strip winding.
• Textile winding.
• Cable handling.
• Film processing.

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13.4 Printing and Paper Machinery

Large printing and paper-processing systems can use multiple motor sections.

Consistent speed is extremely important.

A variation in motor speed can affect:

• Material tension.
• Registration.
• Product quality.
• Production throughput.

A properly configured DC drive can provide precise speed control for these systems.

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13.5 Mining and Heavy Material Handling

Heavy industrial machinery can require high motor torque and large electrical power.

The 400 HP rating allows this drive to be considered for certain heavy-duty material-handling applications.

The exact suitability depends on the motor and mechanical system.

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13.6 Large Process Machinery

Large process machines often require controlled motor speed rather than simple direct-on-line operation.

A DC drive can provide:

• Adjustable speed.
• Controlled acceleration.
• Controlled deceleration.
• Current limitation.
• Torque control.
• Feedback-based regulation.

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14. Product Advantages

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15. Advantage: High Current Capacity

The strongest characteristic of the model is its 667 A output capability.

This allows it to operate large DC motors that would be far beyond the capacity of small-frame drives.

For heavy machinery, current capacity is closely connected to torque capability.

A properly sized drive can provide the electrical power required to accelerate a large motor and handle changes in mechanical load.

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16. Advantage: Suitable for DC Motor Modernization

Many industrial machines have long service lives.

The mechanical structure may remain reliable even after the original drive electronics have become obsolete.

Replacing the drive rather than rebuilding the entire machine can potentially reduce:

• Engineering time.
• Mechanical modification.
• Machine downtime.
• Replacement parts requirements.
• Operator retraining.
• Production disruption.

The 20P21AD667RA0NNN can therefore be considered for DC drive modernization projects where the existing motor remains suitable.

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17. Advantage: Controlled Acceleration

Large motors should generally not be accelerated abruptly.

A controlled acceleration profile can reduce mechanical stress.

This can help protect:

• Gearboxes.
• Couplings.
• Shafts.
• Bearings.
• Belts.
• Chains.
• Mechanical transmission components.

It can also reduce sudden production-line disturbances.

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18. Advantage: Controlled Deceleration

The drive can provide controlled deceleration within the limits of its non-regenerative configuration and the braking arrangement used by the machine.

The braking system must be designed according to the load.

If a machine has a large amount of stored mechanical energy, the engineering team should determine whether a regenerative drive is required.

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19. Advantage: Industrial Feedback

Large production systems often require accurate speed control.

Feedback capability allows the drive to determine actual motor speed rather than relying solely on commanded values.

This can be especially valuable for:

• Rolling machines.
• Winders.
• Paper machines.
• Printing systems.
• Process lines.
• Material-handling systems.

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20. Advantage: Conformal Coating

The conformal-coated configuration provides additional protection for electronic components.

This can be useful in industrial environments where humidity or airborne contamination may be present.

However, conformal coating should not be interpreted as permission to install the drive in an uncontrolled environment.

The IP20 enclosure still requires an appropriate cabinet or electrical enclosure.

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21. Environmental and Installation Requirements

The drive should be installed in a suitable industrial electrical cabinet.

The cabinet should provide:

• Appropriate environmental protection.
• Adequate airflow.
• Correct grounding.
• Sufficient clearance.
• Suitable cable routing.
• Protection from conductive dust.
• Protection from water.
• Protection from oil and chemicals.
• Appropriate temperature control.

Because the drive operates at 667 A, thermal management is particularly important.

The cabinet designer must account for heat generated by the drive and associated equipment.

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22. Installation Considerations

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23. Motor Selection Requirements

A 400 HP motor should not be selected solely based on horsepower.

The following values should be compared with the drive:

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24. Recommended Same-Series Models

The following five models are particularly useful when comparing products within the same PowerFlex DC family.

* Weight values for other models should be confirmed against their exact mechanical configuration. The 78.3 kg value shown for the target model corresponds to approximately 172.63 lb product weight.

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25. Direct Comparison of High-Power Models

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26. Five Regenerative Related Models

For applications where the machine needs regenerative braking, the following PowerFlex DC configurations are important comparison points.

The most direct regenerative comparison is 20P41AD667RA0NNN.

It retains the same general 667 A / 400 HP class but provides regenerative four-quadrant capability.

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27. Five Popular Models From the Same Brand

The following are useful models from the same brand’s broader industrial automation portfolio.

They are not direct electrical replacements for the 20P21AD667RA0NNN. They belong to different product categories and are included because they are commonly used in industrial automation systems.

For a large existing DC motor, these products should not be substituted directly without a complete system-engineering assessment.

The first three are primarily relevant when the motor system is being converted from DC to AC.

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28. DC Drive Versus AC Drive Modernization

When an old DC system is being modernized, there are usually two broad approaches.

The first approach is to retain the existing DC motor and replace the old DC drive.

The second approach is to replace both the DC drive and DC motor with an AC motor and AC drive.

The first approach can be attractive when the existing motor is in good condition and the machine has already been engineered around the DC motor.

The second approach can be attractive when long-term modernization, motor availability, efficiency and simplified maintenance are higher priorities.

The 20P21AD667RA0NNN is primarily relevant to the first approach.

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29. Why the PowerFlex DC Series Is Useful for Large Motors

Large DC motors can provide high torque and very good speed-control characteristics.

They can also be mechanically integrated into machines that have been operating for decades.

A DC drive modernization project can therefore preserve the existing mechanical system.

This can be especially valuable for:

• Steel equipment.
• Paper machines.
• Large conveyors.
• Printing systems.
• Winding equipment.
• Processing machinery.
• Large production lines.

A properly engineered replacement can extend the useful life of the machine without requiring a complete mechanical redesign.

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30. Cabinet Design Considerations

Because the 20P21AD667RA0NNN is a 667 A drive, cabinet design becomes much more important than it would be for a small drive.

The designer should consider:

Heat

Large power electronics produce significant heat.

Adequate ventilation or cabinet cooling is required.

Cable Size

Motor and supply conductors must be appropriately sized for the electrical system.

Busbar Design

High-current applications may require carefully engineered busbar arrangements.

Clearance

Adequate electrical and mechanical clearance is required.

Serviceability

Maintenance personnel need sufficient access to the drive and associated components.

Protection

The upstream protection system must be coordinated with the drive and motor.

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31. Application Advantages

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32. Product Limitations

A technically accurate product description should also consider the limitations.

The 20P21AD667RA0NNN is not an ideal choice for every motor application.

Its principal limitations include:

• It is a DC drive rather than an AC drive.
• It is non-regenerative.
• It is a two-quadrant configuration.
• It requires a compatible DC motor.
• It uses an IP20 open-type enclosure.
• It requires cabinet installation.
• Its 667 A rating is excessive for small motors.
• Its physical size and electrical infrastructure requirements are substantial.
• Its high-current installation requires careful thermal and electrical engineering.
• Exact motor compatibility must be verified from the motor nameplate.

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33. When the 20P21AD667RA0NNN Is a Good Choice

This model is particularly suitable when:

• The motor is approximately 400 HP.
• The motor is a DC motor.
• Armature current is compatible with 667 A.
• The plant has an appropriate 480 VAC three-phase supply.
• The application does not require regenerative operation.
• The machine primarily operates in one direction.
• Existing DC motor infrastructure is worth retaining.
• Precise speed control is required.
• A high-current industrial DC drive is required.
• The application is part of a large industrial production system.

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34. When the 20P21AD667RA0NNN Is Not the Best Choice

A different model should be considered when:

The motor is smaller

For a 2 HP motor, a small Frame A drive is more appropriate.

The motor is around 300 HP

The 20P21AD495RA0NNN may be a closer match.

The motor is around 500 HP

The 20P21AD830RA0NNN is a more appropriate comparison.

The motor is around 600 HP

The 20P21AD996RA0NNN is the logical higher-current comparison.

Regenerative operation is required

A 20P41 regenerative configuration should be considered.

The machine is being completely modernized

An AC motor and PowerFlex AC drive may be a better long-term solution depending on the machine.

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35. Important Model-Selection Table

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36. Key Parameters at a Glance

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37. Overall Product Evaluation

The 20P21AD667RA0NNN is a high-capacity industrial DC drive designed for applications that require substantial DC motor current.

Its 667 A output and 400 HP / 298 kW rating make it appropriate for large industrial machinery rather than general-purpose small motor applications.

Its 480 VAC three-phase input, six-pulse converter, regulated field supply, two-quadrant operation, and non-regenerative configuration provide a practical architecture for conventional large DC motor systems.

The Frame C construction is designed for this higher power level, while the IP20 / NEMA/UL Type Open enclosure means that the unit should be installed inside a properly designed electrical cabinet.

The conformal coating provides additional protection for the electronics, while the blank-plate configuration allows the drive to be integrated into systems where a local HIM is not required.

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38. Final Summary

The 20P21AD667RA0NNN is a 400 HP / approximately 298 kW, 667 A PowerFlex DC drive for large industrial DC motors.

Its main electrical characteristics are 380–480 VAC three-phase input, 667 A output current, six-pulse conversion, two-quadrant operation, and non-regenerative operation.

The drive includes a single-phase regulated field supply and supports advanced motor regulation and feedback arrangements suitable for demanding industrial applications.

Mechanically, it uses Frame C construction and an IP20 / NEMA/UL Type Open enclosure.

The approximate product weight is 78.3 kg, while the shipping weight can be substantially higher because it includes packaging and shipping materials.

Its principal applications include steel-processing equipment, large conveyors, paper machinery, printing equipment, winding systems, heavy material-handling equipment, process machinery and other large industrial production systems.

Its greatest practical advantage is its ability to provide modern digital control for a large existing DC motor, making it particularly relevant to industrial modernization projects where replacing the entire mechanical drive system would be expensive or unnecessary.

For a similar but smaller application, 20P21AD495RA0NNN is a useful 300 HP comparison.

For a larger application, 20P21AD830RA0NNN, 20P21AD996RA0NNN and 20P21AD1K1RA0NNN provide progressively higher current capacities.

If regenerative operation is required, 20P41AD667RA0NNN is the closest corresponding 667 A / 400 HP regenerative configuration.

In practical terms, the 20P21AD667RA0NNN can be summarized as a high-current, 400 HP, 480 VAC-class, two-quadrant, non-regenerative industrial DC drive designed for large DC motor applications where controlled speed, torque and reliable process operation are required.