PowerFlex 70 Obsolete? Status, Faults & Upgrades

The PowerFlex 70 has been a workhorse AC drive in North American plants since the early 2000s. If you're staring at one on a machine and wondering whether to repair, source a spare, or swap it out entirely, this guide cuts through the noise.

What Exactly Is the PowerFlex 70?

The PowerFlex 70 is a general-purpose AC variable frequency drive (VFD) made by Allen-Bradley (Rockwell Automation). It targets variable torque loads like fans and pumps as well as constant torque conveyor and machine tool applications. The drive offers a compact footprint, an optional HIM (Human Interface Module) keypad, and a broad communication adapter ecosystem — DeviceNet, EtherNet/IP, PROFIBUS, and others via bolt-on adapters.

It is not the same product as the PowerFlex 700, PowerFlex 700S, or the PowerFlex 700H, even though the names look nearly identical. That naming confusion causes real purchasing mistakes every week.

PowerFlex 70 vs. PowerFlex 700: What's the Difference?

Short answer: the 700 is the 70's bigger sibling — more power range, more feature depth, and still in active production as of this writing. The 70 tops out well below the 700's ceiling. If your application only needs what the 70 provided, a like-for-like surplus replacement is often the smarter economic call over an engineering re-design for the 700.

PowerFlex 700 vs. PowerFlex 700S: What's the Difference?

The 700S is not just a 700 with extra features — it's a fundamentally different drive targeted at high-performance servo-quality motion on AC induction and permanent magnet motors. Think coordinated multi-axis winders, draw stands, and applications that previously needed a servo drive.

Key distinctions:

• The 700S requires a position feedback card (encoder) for full closed-loop operation; the standard 700 doesn't.
• The 700S uses a different programming environment and integrates differently with Logix controllers.
• If someone asks you to source a "700" and the panel has a 700S, do not swap — they are not interchangeable in high-performance applications.

PowerFlex 70 Series A vs. Series B: What Changed?

Rockwell released the PowerFlex 70 in multiple hardware series. Series A and Series B are the most commonly encountered in the field. This matters when sourcing replacements because some components and firmware are not cross-compatible.

Practical differences to know:

• Firmware: Series B drives typically carry later firmware revisions. A Series A drive loaded with Series B firmware — or vice versa — can cause parameter incompatibilities or initialization faults. Always match series when replacing.
• Control board: Internal board revisions differ between series. An A-series control board does not drop into a B-series power structure without verification.
• HIM module: The HIM modules for the PowerFlex 70 are generally interchangeable across series for basic operation, but advanced features may behave differently — confirm compatibility in Rockwell's documentation for your specific HIM model.
• Where to find the series: It's on the catalog number label on the drive's chassis — look for "/A" or "/B" at the end of the catalog string.

How to Clear a Fault on a PowerFlex 70

Faults lock out the drive until you acknowledge them. Here's the general procedure using the HIM keypad. Menu paths and button sequences vary by HIM model and firmware version — always cross-reference with your drive's user manual for the exact steps that apply to your hardware.

1. Read the fault code first. The HIM display shows a fault number (e.g., F-XX). Write it down. Clearing without diagnosing is how the same fault comes back in five minutes.
2. Look up the fault. Rockwell's PowerFlex 70 User Manual lists every fault code with probable causes. Access the literature library at literature.rockwellautomation.com and search for the PowerFlex 70 user manual for your firmware revision.
3. Address the root cause. Overcurrent faults usually mean a mechanical load issue or acceleration ramp too fast. Overvoltage faults often point to decel ramp too fast or insufficient braking. Ground faults point to motor insulation or wiring issues. Fix the cause before clearing.
4. Clear the fault via keypad. On the HIM, navigate to the fault queue and select the clear/reset option. The exact button sequence depends on your HIM model — consult the HIM documentation or the PowerFlex 70 user manual for your specific hardware. On most units, pressing the Stop/Reset button while a fault is active will attempt a clear, but exact behavior varies by model and firmware.
5. Clear via the Fault Clear parameter. You can also write the appropriate value to the Fault Clear parameter via software (RSLogix/Studio 5000 or a connected HIM). Exact parameter numbers vary by firmware revision — consult your user manual for the correct parameter to use.
6. Attempt a run command. After clearing, command a run at low speed and watch for the fault to return. If it returns immediately, the root cause is still active.
7. Review fault queue history. The drive logs multiple faults in a queue. Review all of them — sometimes a cascade of faults hides the original cause.

Common PowerFlex 70 Problems in the Field

• Overcurrent / Ground Fault: Check motor leads for insulation breakdown, especially on older machines. Meg the motor before blaming the drive.
• Phase-to-Ground Short: This fault type indicates a short detected between an output phase and ground — inspect motor cable insulation, conduit entries, and motor winding insulation. Consult your user manual to identify the exact fault code for your firmware revision. Do not confuse with an input phase loss condition.
• Input Phase Loss: Often an incoming power issue or a blown input fuse, not a drive failure. Check supply voltage on all three phases under load. Confirm the exact fault code for your firmware revision in the PowerFlex 70 user manual available at literature.rockwellautomation.com.
• Power Loss fault: Drive lost input power mid-operation. Check upstream breaker, contactor, and supply voltage stability.
• Thermal faults: Clean the heatsink fins. The PowerFlex 70 heatsink collects incredible amounts of dust and lint in industrial environments. A clogged heatsink will kill a drive that could otherwise run another decade.
• Drive powers up but won't accept a run command: Check the control wiring at terminals — specifically the Enable input and any two-wire/three-wire control configuration set in parameters. An incorrect Start Source parameter setting is one of the most common causes. Exact parameter names and numbers vary by firmware revision — consult your user manual.
• HIM shows "Pwr Loss" or blank display on powerup: Confirm incoming voltage is within spec. Also check the internal 24V logic supply — on some frame sizes a blown fuse on the control board takes out the HIM.

When Should You Replace Instead of Repair?

The PowerFlex 70 is discontinued. That changes the math on repair decisions.

Replace rather than repair when:

• The power section (IGBT module) is blown and you can't source matched IGBTs.
• The drive has run more than 15–20 years and capacitors are approaching end of life (look for bulging, leaking, or rising ripple current).
• You need a feature the 70 never had — EtherNet/IP native port, advanced motion profiles, or safety ratings above what the 70 supports.
• Downtime cost per hour exceeds the price of keeping a tested spare on the shelf.

If none of those apply, a tested surplus PowerFlex 70 is often the fastest, most cost-effective path. You avoid engineering time re-parameterizing a new drive platform, rewriting PLC code for different parameter addresses, and retraining operators.

Disclaimer: This guide is provided for general information only. Procedures vary by model, series, and firmware version. Industrial equipment can cause serious injury, equipment damage, or downtime if serviced incorrectly. Always consult the manufacturer's official documentation and a qualified professional before performing work, and follow your facility's lockout/tagout and safety procedures. PLC Department is an independent surplus supplier and is not affiliated with or endorsed by the manufacturers referenced. Use this information at your own discretion.