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Predictive Maintenance Starts With the Drive: What Your VFD Is Telling You

by Bryan Hellman



Predictive maintenance usually starts with vibration data, thermography, or oil analysis — but one of the most overlooked early warning systems in a plant is the drive that runs the motor.

Your VFD continuously monitors motor health, line conditions, loading, and temperature. If you learn to interpret these signals before they become shutdown faults, your drive becomes a front-line prevention tool, not just a power controller.

A VFD doesn’t “guess” what’s wrong. It measures it, stores it, and reports it. If you need a deeper primer on how drives work in the first place, you can also read our blog Understanding Variable Frequency Drives: How They Optimize Industrial Motors.

Your VFD Is More Than a Power Module — It’s a Sensor Suite

Every modern drive automatically collects diagnostic data that can be used for predictive maintenance without adding a single extra sensor:

  • Motor current, torque demand, and phase imbalance
  • Load variations and stall warnings
  • Heat levels inside the cabinet and at the motor
  • Line voltage fluctuations and DC bus status
  • Fan and capacitor aging indicators on many models

Drives like the Siemens 6SE6440-2UD33-0EA1 VFD and Yaskawa A1000 series units are built with detailed diagnostic messaging and parameters you can trend over time — turning the VFD into a live sensor hub, not just a speed controller.

Fault Codes Aren’t Errors — They’re Early Warnings

Most plants treat fault codes like a nuisance — reset it, get the line running, figure it out later. By then, “later” usually costs more. Faults and alarms are often the first visible sign that something is drifting out of normal range. If you’re still in “reactive mode,” you may also find it helpful to review 7 Quick VFD Fixes to Try Before You Replace the Drive as a companion checklist.

Common VFD fault types that act as early warning signs:

Fault Type What It Predicts Likely Root Cause
Overcurrent / Overload Mechanical drag or load increase over time Worn bearings, belt misalignment, clogged pump, product buildup
Undervoltage / DC Bus Undervoltage Upstream power instability Loose lugs, corroded connections, overloaded feeder or transformer
Overtemperature Cooling issues and premature drive aging Failed fan, blocked vents, cabinet heat buildup, excessive load
Phase Loss / Phase Imbalance Distribution issues or cable degradation Tripped fuse, feeder problem, corroded terminals, cable damage

Treat faults as trending data, not just interruptions. Intermittent faults are often the drive telling you, “Something is changing. Fix it before I have to shut you down.”

Trending Motor Current Is the Easiest Predictive Tool You Already Own

A rising current trend over days or weeks is one of the simplest and most reliable predictive indicators you can use.

Slowly increasing current (with no recipe or speed change) often points to:

  • Worn or dry bearings
  • Belt or gearbox misalignment
  • Pump clogging or filter restriction
  • Mechanical binding or product buildup on conveyors
  • Motor winding degradation

Most VFDs let you view real-time current and percentage load directly on the keypad. Many — like Yaskawa CIMR-AU4A0139FAA A1000 drives — also support trending and advanced diagnostics via simple parameter access.

Don’t wait for an overcurrent trip. If your baseline “normal” load is climbing, something downstream is wearing out, even if the motor still runs.

Temperature Data Predicts Failure Faster Than Faults

Two temperature readings matter most for predictive maintenance:

Drive Internal Temperature

A drive running just 10–15°C hotter than normal can cut capacitor and fan life dramatically. High temperature today is a capacitor failure or intermittent DC bus issue tomorrow.

Motor Temperature (Measured or Calculated)

Even without RTDs, many VFDs estimate motor thermal load using I²T models. Rising temperature at the same load can indicate insulation breakdown, blocked ventilation, or poor cooling airflow around the motor.

Use temperature as a trend, not just a trip limit. When the drive tells you it’s hot, it’s giving you a scheduling opportunity, not just an alarm. If overheating is already a concern in your plant, you may also want to read Cabinet Cooling for VFDs: 10 Practical Steps to Stop Overheating.

Harmonics, Line Issues, and EMI — Your VFD Will See Them First

Drives also detect upstream electrical problems before they show up elsewhere. Indicators include:

  • Frequent DC bus overvoltage alarms during deceleration or light load
  • Undervoltage trips during peak plant demand
  • Phase imbalance warnings
  • Unusual nuisance trips on multiple drives in the same section

These often point to:

  • Loose or corroded panel connections
  • Worn breakers or fuses starting to fail under load
  • Transformers operating near or above their design limits
  • Large non-linear loads creating voltage distortion

In HVAC applications, for example, monitoring alarms and bus behavior on a dedicated drive like the ABB ACH550-UH-08A8-4 HVAC drive can give you early visibility into both mechanical and electrical issues tied to fans and pumps.

Use the Drive’s Data Logging and Diagnostics Menu Like a Meter

Modern VFDs provide onboard trending tools that many plants never touch. Even basic models can log or expose:

  • Motor load and torque over time
  • Drive and motor temperature trends
  • Fault history and frequency
  • Bus voltage and line condition snapshots

Higher-end drives, such as those in the Schneider Electric Altivar Process ATV630 collection, add built-in energy and process monitoring tools that make it even easier to spot drift and anomalies.

If you periodically export or record these values (even manually at first), your maintenance team gains a predictive data set with zero additional sensors or cabling.

When the VFD Itself Starts to “Age Out”

The drive is not just watching the motor — it also reports on its own health. Indicators of an aging VFD include:

  • Fan runtime or fan alarm messages
  • Capacitor aging or “remaining life” warnings
  • Rising internal temperature for the same load and environment
  • Increasing frequency of undervoltage or DC bus alarms
  • Unusual audible noise from the drive (switching instability, fan issues)

Fans and DC bus capacitors are consumables. When the drive tells you they’re near end-of-life, it’s an invitation to schedule service or swap the drive on your terms — not during an unplanned shutdown.

Predictive Strategy: Let the Drive Inform the Schedule

Instead of guessing replacement intervals, use what the VFD is already telling you:

  • Rising current trend? Inspect motor bearings, belts, gearboxes, or pump condition.
  • Repeated DC bus or undervoltage warnings? Inspect upstream wiring, lugs, and breakers.
  • Steady increase in drive temperature? Clean filters, improve enclosure airflow, confirm cabinet spacing.
  • Fault codes appearing more often? Log them, identify patterns, and address root causes before they become hard trips.

The goal is to let the drive act as your diagnostic lead, not just your last line of defense.

Example VFDs With Built-In Diagnostics and Monitoring

If you’re building a predictive maintenance program around your drives, choosing models with strong diagnostics, communication, and logging features makes the job easier. Here are examples from Industrial Automation Co.’s inventory:

All of these drives are backed by Industrial Automation Co.’s 2-year warranty and are tested to perform in demanding industrial environments.

Recommended Predictive Maintenance Spares to Keep On Hand

Once you start using your VFD data as a predictive tool, it makes sense to stock spares strategically around your most critical applications.

Consider keeping the following on the shelf for each critical area of your plant:

  • At least one spare VFD for each major horsepower range or critical process line (for example, a spare A1000 or Altivar unit matched to your most common motor frame).
  • Pre-programmed parameter backups stored on SD cards, USB tools, or parameter-copy devices so a replacement drive can be dropped in quickly.
  • Spare cooling fans and air filters for your highest-duty drives to address temperature alarms before they become trips.
  • One spare keypad or operator panel for drive families where configuration and diagnostics rely heavily on the HMI.
  • Basic electrical spares (fuses, contactors, terminal lugs) to address line-side issues that drive diagnostics are pointing to.

If you’re using refurbished drives as part of your spare strategy, it’s worth reviewing our guide What to Know Before Buying Refurbished PLCs, HMIs, and VFDs so you know what to look for.

Related Resources on VFDs & Predictive Maintenance

If you want to go deeper on drives, troubleshooting, and reliability, these articles from Industrial Automation Co. are a great next step:

Need a Replacement Drive or Drive Repair Before Full Failure?

If your drive data is telling you a failure is coming — rising current, repeated faults, increasing temperature, or capacitor/fan warnings — it’s often cheaper to act before a full shutdown. Swapping or repairing the drive on your schedule protects throughput and avoids emergency costs.

Industrial Automation Co. stocks a wide range of VFDs from brands like Siemens, Yaskawa, ABB, Schneider Electric, Mitsubishi, and others, all backed by a 2-year warranty. Our team can also help you decide whether repair or replacement makes more sense based on your application, runtime, and future plans.

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