Hardware Comparison: PowerFlex 4, 40, and 400 Drives

While Allen Bradley is most well-known for its Logix controllers, their PowerFlex drives have also been a large contributor to their growth in the automation market. Currently, the PowerFlex 520 and 750 series are the primary offerings for Allen Bradley drives but the PowerFlex 4/40/400 series is still supported by Rockwell and still is a great choice for certain applications.

The PowerFlex 4 series is one of Allen Bradley’s low-cost, no-frills drive offerings, with the PowerFlex 4M drive being the primary offering in this group. With power ratings of up to 5HP in the PowerFlex 4 and 15HP in the 4M, these drives offer simple setup and control in a compact package with a low cost. The main features of this series are feed-through wiring on the 4M, volts per hertz control, and RS-485 communications (with others available through optional modules.) This drive series is a standard offering on most OEM delivered machines, based on the cost for performance. The feed through wiring configuration for the 4M makes it easier for users to upgrade from motor-starter control to drive control by mimicking the original wiring configuration, potentially allowing for the upgrade to consist of swapping out just the starter for the drive and keeping the associated circuit protection and wiring. For smaller size, simple motor applications, these drives are hard to beat. One note with these drives, the form factor compared to a 520 series is different, with the PowerFlex 4 being shorter and wider. This can cause spacing issues in panels if moving between 4 and 520 series drives.

The PowerFlex 40 steps up from the PowerFlex 4 (not 4M) series, providing higher horsepower ratings (up to 15HP at 480VAC) and adding sensorless vector control. As with the PowerFlex 4, the PowerFlex 40 drives will handle voltages from 100VAC to 600VAC, at power ratings from 0.5 to 15 HP. Sensorless vector control is an improved control method for maintaining torque at low speeds, giving improved performance over volts per hertz control. Communications via RS-485 are integrated, and optional communications methods can be added through option modules. StepLogic control is added, allowing for the drive to be used as an independent position controller. Additionally, the 40P drive adds to the 40 series by including closed loop control and option Safe Torque Off performance.

The PowerFlex 400 series is the highest power offering in the family, with power ranges from 3 to 350HP in voltage ranges of 200-480VAC. The PowerFlex 400 is optimized for use in mechanical fan and pump systems, utilizing volts per hertz control and various special modes such as flying start to allow peak performance in these applications. Integrated communication options include RS-485, CIP, Modbus RTU, Metasys N2, and Apogee FLN P1, as well as further protocols through optional modules. Packaged drive options including main disconnects and bypass contactors are also available for incorporation into the primary fan and pump functions of these drives.

The Powerflex 4x series is part of Allen Bradley’s compact line of drives. With power offerings from 0.25 to 350HP, these drives combine compact form factors and a low cost to allow for economical integration of drive functions into a machine. While the PowerFlex 520 and 750 series will end up taking over the applications previously supported by the PowerFlex 4 series, these drives will remain in the market for a long time based on their price point and capabilities. For a low-cost entry point to speed control via drives, the PowerFlex 4 series is an excellent choice.

Specification PowerFlex 4 PowerFlex 4M PowerFlex 40 PowerFlex 400
Motor Control Volts/Hz Volts/Hz Volts/Hz Sensorless Vector Control Volts/Hz
Application Open loop speed regulation Open loop speed regulation Open loop speed regulation Open loop speed regulation
Voltage 100-480VAC 100-600VAC 100-600VAC 200-480VAC
Horsepower 0.25 – 5HP 0.25 – 15HP 0.5 – 15HP 3.0 – 350HP
Features Compact Form Zero Stacking Overload Protection Compact Form Feed Through Wiring Zero Stacking Overload Protection Compact Form Zero Stacking Overload Protection StepLogic Ideal for Pumps and Fans Overload Protection Flying Start Internal PID Loop
Communications Integral RS485 (Modus RTU) Integral RS485 (Modbus RTU) Integral RS485 (Modbus RTU) Integral RS485 (Modbus RTU, Metasys N2, P1-FLN)
Safety No No Yes (with module) No
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