Allen-Bradley PowerFlex 525, 755 and 7000 Drives

Short answer

PowerFlex is the Allen-Bradley family of variable frequency drives from Rockwell Automation. The PowerFlex 525 is a compact drive with built-in EtherNet/IP and hardwired Safe Torque Off; the PowerFlex 755 is the high-performance drive of the 750 series, with hardwired or network Safe Torque Off; and the PowerFlex 7000 and 6000T are the medium-voltage lines.

What it is and where it is used

PowerFlex is the Allen-Bradley family of variable frequency drives from Rockwell Automation. The models include the PowerFlex 525 and PowerFlex 527 of the 520 series, the PowerFlex 753 and 755 of the 750 series, and in medium voltage the PowerFlex 7000 and the PowerFlex 6000T. The PowerFlex 4 and 40 are still installed in older plants.

They are found in industrial plants with Rockwell control systems (ControlLogix, CompactLogix), on pumps, fans, compressors, conveyors and mills. The drive controls the speed and torque of the motor; its effect on the grid and on the motor is analyzed separately. For the general concept, see induction motor and its protections.

Variants: PowerFlex 525, 527, 753, 755, 7000 and 6000T

Model	Application	Main difference
PowerFlex 525	Machines and general applications	Compact; built-in EtherNet/IP; hardwired Safe Torque Off PLd / SIL 2 cat. 3
PowerFlex 527	Machines with Logix control	Safety integrated over EtherNet/IP
PowerFlex 753 / 755	High performance, processes and large machines	750 series; hardwired or network Safe Torque Off, SIL 3, PLe, cat. 3
PowerFlex 7000 / 6000T	Medium voltage	Drives for medium-voltage motors
PowerFlex 4 / 40	Earlier low-power generations	Still installed in existing plants

Main features

Safe Torque Off (STO): removes the power that produces rotation without de-energizing the drive, for safe machine stops. On the 755, the command can arrive over the network from a GuardLogix controller over EtherNet/IP.
Logix integration: the drive is added to the controller project, which simplifies configuration and diagnostics from the control system.
Configuration software: Connected Components Workbench for the 525 and the 750 series, and Studio 5000 Logix Designer when the drive is part of the controller project.
Motor protection inside the drive, which complements, without replacing, the protection of the grid and of the medium-voltage motor.

750 series and PowerFlex 755T: what Rockwell publishes

The PowerFlex 755T brochure and Rockwell’s low-voltage drive selection guide (both in English) describe four configurations of the 755T family, which uses TotalFORCE technology:

Variant	What it is	Power figure in the brochure
PowerFlex 755TS	Six-pulse drive	Panel mount up to 500 Hp (355 kW)
PowerFlex 755TL	Active front end: harmonic mitigation and power factor correction	Panel up to 200 Hp (132 kW)
PowerFlex 755TR	Regenerative active front end: returns energy to the grid, with harmonic mitigation and power factor correction	Cabinet up to 6,000 Hp (4,550 kW)
PowerFlex 755TM	Common DC bus for several motors, with regenerative and non-regenerative options	Cabinet up to 6,000 Hp (4,550 kW)

The brochure states that the 755T uses the same control architecture and network interface as the medium-voltage PowerFlex 6000T, which reduces spare parts and simplifies operation when a plant combines both. The selection guide places the 750-series PowerFlex 755 in applications that need position, speed or torque control up to 1,500 kW (2,000 Hp). According to a distributor’s selection guide, the 520 series sits in the lower power range, up to 30 Hp.

Other data from the 755T brochure that help in understanding the platform:

Slot architecture. It supports up to five option cards for inputs and outputs, communications, safety and feedback.
Integrated motion. With Studio 5000 and a Logix controller, the drive is managed with the same motion instructions as Kinetix servo drives, with network synchronization from electronic gearing to electronic cam.
Simplified replacement. The Logix controller keeps the drive parameters and restores them each time it connects, so when a drive is replaced it does not need to be reprogrammed by hand.
Predictive maintenance. The drive calculates the expected life of critical components according to real use and environment and issues alerts.
DeviceLogix. Control logic embedded in the drive, standard on the 755T and also present on the 753 and 755 according to Rockwell.
Software. Studio 5000 Logix Designer for integration with the controller and Connected Components Workbench, which Rockwell describes as free software with startup wizards.

How to choose the step of the family

The practical difference between the models is not the name but the plant architecture:

Machine or small assembly. The 520 series (523, 525, 527) covers low power with built-in EtherNet/IP on the 525 and hardwired STO safety.
Process or large machine with torque or position control. The 750 series supports induction and permanent magnet motors, option cards and network safety.
Grid quality or regeneration. If the plant must limit harmonics or return energy during braking, the active front end variant (TL or TR) avoids installing separate filters. The effect of drives on the grid is studied in harmonics of variable frequency drives and, with the IEEE 519 standard, in our power quality study.
Medium-voltage motors. PowerFlex 6000T or 7000; they are tested with motor and cable tests, see testing medium-voltage motors.

Points of attention at commissioning

Functional safety. The level the STO reaches (SIL 2 or 3, PLd or PLe) depends on the model and on how the safety circuit is wired; validation is done on the whole function, not only on the drive (IEC 61800-5-2, ISO 13849-1).
Cable and motor. Drives produce overvoltages at the motor because of cable length; see transient overvoltages in industrial plants.
Repeated trips. Before blaming the drive, check the load, the cable and the grid; see VFD tripping.
Starting with a soft starter or a drive. The choice between the two is explained in soft starter vs variable frequency drive.

Communications and integration

EtherNet/IP is the native network of the family; the 525 has it built in and the 750 series supports additional communication cards. When the SCADA of the substation or plant does not speak EtherNet/IP, it is integrated through the controller or a gateway, for example toward Modbus TCP. See PLC and substation automation.

Frequent technical questions

PowerFlex 525 manual: Rockwell publishes the user manual and technical data of the 520 series in several languages.
Fault codes: the manual lists each code; a repeated overcurrent or DC bus overvoltage fault is usually in the motor, the cable, the load or the grid.
Hardwired or network STO: it depends on the model and the safety architecture of the machine; Rockwell documents both options for the 750 series.
Harmonics in the plant network: see harmonics of variable frequency drives.
Medium-voltage drive and motor relay: the PowerFlex 7000 feeds motors that keep their own relay; see motor protection relay.

How we help

We do not sell or repair drives. Our team integrates the drive into the control system and the SCADA, coordinates its protections with those of the grid, tests the motor and the cable and supports the commissioning, in industry and in substations, in Colombia or elsewhere on request. See control, protection and communications configuration, motor testing and, if the problem is harmonics, power quality. Write to us through contact.

References

IEC 61800 (series), including IEC 61800-5-2 (functional safety); ISO 13849-1; IEC 62061; IEEE 519.
Rockwell Automation, PowerFlex 525 and 755 pages, 520 series specifications, low-voltage drive selection guide, 750 series Safe Torque Off manuals and 520 series brochures.

Frequently asked questions

What software configures the PowerFlex 525?

Rockwell Automation states that the PowerFlex 525 is configured with Connected Components Workbench, version 7 or later. When the drive is part of a project with Logix controllers, it is also integrated from Studio 5000 Logix Designer.

Does the PowerFlex 525 have Safe Torque Off?

Yes. It has hardwired Safe Torque Off, certified by Rockwell Automation for PLd / SIL 2 category 3, which removes the torque-producing power from the motor without de-energizing the drive. For safety integrated over EtherNet/IP with a GuardLogix controller, the family offers the PowerFlex 527.

What is the difference between the PowerFlex 525 and the PowerFlex 755?

They are two lines of the same family. The 525 is compact, with built-in EtherNet/IP, for machines and general applications. The 755 belongs to the high-performance 750 series, with hardwired or network Safe Torque Off options certified for SIL 3, PLe, category 3, and greater capacity for communication and control cards.