The most expensive fix is the wrong fix
When a variable frequency drive throws an alarm and the line stops, the instinct is to blame the drive and order a replacement. But most VFD alarms are the drive correctly reporting a problem somewhere else — in the power feeding it, the motor it drives, or its own settings. Replacing the drive without diagnosing first often means the new drive alarms the same way a week later.
Layer 1 — Power supply
Illustrative photoStart upstream of the drive. Voltage imbalance between phases, sags during plant peak loads, loose input connections, and harmonic distortion from neighboring equipment all trigger overvoltage, undervoltage, and input-phase alarms. Measure the input voltage under actual operating conditions — not at idle on a quiet Sunday. If the power going in is bad, no drive on earth will run clean.
Layer 2 — Load and motor
Next, look downstream. A mechanically binding conveyor, an overloaded pump, a motor with failing bearings, or damaged motor cable insulation will push current beyond the drive's limits and trigger overcurrent or motor-overload alarms. Check whether the alarm follows a specific load condition or speed — and megger the motor and cable if the pattern points that way. The drive is often the messenger, not the culprit.
Layer 3 — Parameters
Finally, check the drive's own configuration. Wrong motor nameplate data, acceleration and deceleration times set too aggressively, an incorrect control mode (V/f vs. sensorless vector), or a carrier frequency fighting a long cable run — all of these produce alarms on perfectly healthy hardware. This layer is the cheapest to fix and the most commonly skipped, especially after someone 'just copied the settings from the old drive.'
Read the alarm code before you reset it
The drive is telling you something specific. Record the exact alarm code, what the process was doing when it tripped, and how often it happens — then reset. That record is worth more than an hour of guessing, whether you troubleshoot it yourself or call us.
VFD alarming? Send us the exact alarm code plus the operating conditions when it trips — what the machine was doing, and how often. We will give you a free preliminary assessment of which layer your problem is in.