VFD Fault Codes Explained: Overcurrent, Overvoltage, Undervoltage, and Overload Trips (Causes and Fixes)
Variable frequency drives protect both the motor and the equipment they run. When a drive detects a condition outside safe limits, it stops the process and displays a fault code. For plant engineers and maintenance teams, the priority is to find the cause quickly and correct it before production is affected.
A trip does not always mean the drive is faulty. Many events that appear to be drive failures begin elsewhere, in the wiring, the mechanical load, or the incoming supply. Accurate diagnosis depends on reviewing the whole system, not only the drive.
This guide explains four common trips: overcurrent, overvoltage, undervoltage, and overload. For each one, it outlines the typical causes and the recommended corrective actions.
Quick Comparison of the Four Trips
| Trip | Typical Trigger | First fix to try |
| Overcurrent | Loose connections, damaged wires, mechanical friction, fast acceleration, heavy starting load | Check wiring, run autotuning, lengthen acceleration time. |
| Overvoltage | Quick deceleration, overhauling loads, supply voltage spikes | Lengthen deceleration time, stabilize the supply, add braking resistors or a regenerative supply |
| Undervoltage | Supply voltage too low, grid fluctuations | Measure input voltage and DC bus, confirm the supply matches the drive rating |
| Overload | Undersized drive, starting torque or surge loads, heat | Recheck sizing with margin, clean and cool the drive, consider derating |
What Is a VFD Fault Code?
A VFD fault code is the drive’s way of naming the problem it detected before it stopped. Frequency converters help keep production stable through fault diagnosis. They point to process problems, and sometimes the drive itself needs repair or replacement.
First Steps Before You Reset Anything
A few quick checks save a lot of guessing:
- No display or lights: Check the input AC power first, then confirm the control power.
- Won’t start or runs oddly: Read the fault code and look it up in the drive manual.
- Check live values: Look at input voltage, DC bus, output current, I/O, and control status.
- Ask the operators: Find out the machine status, any grid fluctuations, nearby construction, and whether power-factor capacitors were switched.
Overcurrent Trips
Overcurrent means the drive saw more current than it should. It is one of the most common trips, and the cause is often simple.
Common causes
- Loose power connections or damaged wires
- Mechanical wear and excess friction in the machine
- Acceleration that is too fast
- Unstable input voltage
- High starting load from mechanical binding, clogged or damp material, or excessive speed
How to fix it
- Tighten connections and replace damaged wires.
- Run the autotuning function so the drive matches the motor. You will need the motor nameplate data: rated power, voltage, current, frequency, and RPM.
- Inspect the machine for wear and friction.
- Slow down the acceleration rate.
- Clear debris and loads before startup.
- Stabilize the input voltage.
Overvoltage Trips
Overvoltage shows up most often when a motor slows down fast. During quick deceleration, the motor acts like a generator and sends energy back into the drive. Voltage spikes on the supply side can cause the same trip. Overhauling loads, where machine inertia keeps pushing the motor, do it too.
How to fix it
- Stabilize the power supply.
- Lengthen the deceleration time.
- Add dynamic braking, where resistors burn off the extra energy.
- Use a regenerative power supply, which feeds the energy back to the grid.
Veikong Electric lists a braking chopper, an aluminum resistor, and a ripple resistor, each with its own datasheet. Check the datasheet for ratings, and confirm the match with the technical team before ordering.
Undervoltage Trips
Undervoltage refers to a supply that is too low. A low supply can also make a drive stop for reasons that look unclear at first.
What to check
- Measure the supply voltage at the drive input.
- Read the DC bus value on the keypad.
- Ask about grid fluctuations, on-site construction, and power-factor capacitor switching.
- Confirm the supply matches the drive rating. Veikong’s general-purpose drives come in single-phase or three-phase 220V models rated 220V to 240V, and three-phase 380V models rated 380V to 480V.
If the drive stops for no clear reason
Use this short routine:
- Set P00.06 to 0 and start the drive with the keypad RUN key. If it keeps running, the problem is an outside signal.
- Check the signal wires and the connector between +24V and PLC.
- Look at the r06.00 terminal signal to see whether the run command was interrupted.
Overload Trips
Overload happens when the drive is asked for more than it can deliver. The most common reason is sizing. A drive that is too small trips out under load.
Common causes
- A drive sized only on running kW, with no margin for starting torque.
- Peak or surge loads during the work cycle.
- Heavy starting loads such as cranes, hoists, and high-inertia machines.
- Heat from high ambient temperature, blocked airflow, or dust.
- A high carrier frequency setting.
How to fix it
- Size the drive from the motor nameplate and add margin for starting torque, surge loads, and site temperature.
- For lifting work, look at the VFD530, which includes special lifting logic and a brake logic function.
- Measure the temperature near the drive’s air inlet, since cabinet air can run much hotter than room air.
- Clean filters and heat sinks, and check that the cooling fan moves strong, steady air.
- Consider derating, or choose a higher-power drive for extra thermal margin.
How to Prevent Repeat Trips
- Clean fans and heat sinks every month.
- Use a proper enclosure where dust and moisture are present. The VFD510 IP55 is built for harsh, dusty, or wet settings.
- Control the enclosure temperature. Add cooling where it is hot, and prevent moisture where it is cold.
- Match supply voltage and phase to the drive before ordering.
Is Every Trip a Drive Failure?
No, many trips come from loose wiring, a stuck load, supply problems, or heat. Check the system before replacing the drive.
How Veikong Backs Its Drives
Shenzhen VEIKONG Electric Co., Ltd researches, manufactures, and trades high-, medium-, and low-voltage frequency inverters, and has been doing so since 2004. Its products follow ISO9001 quality management and meet ISO, CE, and IEC standards.
Before delivery, each product passes a 12-hour power-on aging test in a high-temperature chamber, then a final full-load test.
Support includes:
- A 24-month warranty with free spare parts for component quality issues.
- Lifelong online technical support with 24-hour fast response.
- Free professional product selection based on your application.
Overcurrent often points to wiring, friction, or fast acceleration. Overvoltage usually comes from quick stops, so slow the deceleration or add braking. Undervoltage means checking the supply and the signals. Overload is mostly about sizing, starting torque, and heat.
Read the code, check live values, and ask what changed on the machine.
Need help with a drive that keeps tripping, or choosing the right size? Email infoveikong-electric.com, call +86-0755-89587650, or message on WhatsApp at +86 15989436541. For technical support, write to Service@veikong-electric.com.