Veichi fault codes: what the code means and where to start
When a Veichi VFD trips and shows a code, start with three things: which code it is, in which mode it appeared (acceleration, deceleration or constant speed), and whether it clears once the motor is disconnected. E.OC is overcurrent, E.OU is DC-bus overvoltage, and E.Lu is supply undervoltage. Two of these three almost always get solved without service: by the right accel/decel time, a braking resistor, or a proper response to a sagging mains. E.OC, on the other hand, demands an honest check — sometimes it is a short in the cable or motor windings, and sometimes the drive's own power module needs replacing.
Below is the same diagnostic tree we use in service on real cases across the Veichi AC10, AC310 and AC01 series. First, a quick word on the mnemonics, because this is where people get confused.
Note: the exact code mnemonic depends on the series
In Veichi documentation the same fault is written slightly differently. On the AC10 the code is printed in capitals — E.OC1, E.OU1, E.LU. On the AC310 and AC01 the code table uses mixed case — E.oC1, E.ou1, E.Lu. It is the same protection, just a different print style in the manual. The trailing digit is the mode in which the protection tripped:
- 1 — during acceleration;
- 2 — during deceleration;
- 3 — at constant speed.
That digit narrows the cause immediately: E.OC1 and E.OU1 point to accel time, E.OC2 and E.OU2 to decel time, while a "3" means the issue is not in a transient but in the load or the mains itself. None of the three series has an "E.OV" code — overvoltage in Veichi is labelled exactly as E.OU (over-voltage), so if you are searching for "E.OV", look at E.OU.
Safety before any measurement
Before you open the terminal cover and measure anything, follow three rules — they are not red tape; hands and instruments get burned over them:
- De-energise the drive and wait for the bus to discharge. The DC-link capacitors hold dangerous voltage even after power-off. The AC10 manual states it plainly: only begin work after all indicators go dark and the main-circuit voltage drops to a safe level — 5 minutes after disconnection.
- Never open an output contactor under load. Breaking a loaded output circuit destroys the drive's output switches (IGBTs). If you need a contactor between the VFD and motor, switch it only when the drive is stopped.
- Measure resistance only on a de-energised drive. Resistance between DC+ / DC− and the U, V, W outputs is measured with a multimeter on a fully discharged drive, never "live".
E.OC — overcurrent: isolate the motor as step one
E.OC (E.OC1 / E.OC2 / E.OC3) is the nastiest code, because behind it lie both trivia and a full power-stage replacement. The algorithm that saves hours of guessing:
- Step 1. Isolation. De-energise the drive, disconnect the motor cable from U, V, W and run the VFD with no load (no motor). If the fault clears, the drive's power stage is healthy and the cause is in the motor (shorted windings) or a punctured cable. If the fault remains even without a motor, the problem is inside the drive, in the power module (IGBT).
- Step 2. IGBT check. On a de-energised, discharged drive, measure the resistance between DC+ / DC− and the U, V, W outputs. A near-zero (short) reading means the module is punctured and the drive needs replacement/repair.
- Step 3. Thermal paste (on high-power drives). On drives from ~40 kW a common hidden cause of E.OC is dried-out thermal paste under the module. The die overheats locally within milliseconds, the standard temperature sensor cannot react in time, and the protection trips on current rather than on heat. The fix is inspection and re-application of the thermal interface in service.
The Veichi manual lists the same causes for E.OC1/E.OC2/E.OC3 as our practice does: a short at the output or to ground, motor damage, too short an acceleration time (E.OC1 → increase F01.22), too short a deceleration time (E.OC2 → increase F01.23), and an output cable that is too long (shorten it or fit an output reactor). So before suspecting "hardware", check the accel/decel time — on a dynamic load a very short time produces a current surge out of nowhere.
E.OU — overvoltage: regeneration and mains surges
E.OU (E.OU1 / E.OU2 / E.OU3) trips when the DC-bus voltage exceeds the overvoltage threshold. The AC10 manual states the threshold directly: 820 V on the DC bus for a three-phase input and 400 V for a single-phase input. The excess voltage comes from one of two scenarios:
- Regeneration during braking (most often E.OU2). When an inertial load (fan, flywheel, centrifuge) decelerates faster than the energy can dissipate, the motor goes into generator mode and pushes current back into the bus. The fix: increase the deceleration time (F01.23) or fit a braking resistor to burn off the excess. This is the manual's own listed cause for "overvoltage during deceleration".
- Input mains surges (E.OU1 / E.OU3). On rural and weak lines the voltage spikes above nominal; a tell-tale sign on the drive itself is bulging input capacitors. The manual's fix: keep the supply within range and add a reactor on the input side to smooth the spikes.
A side note: the "F840" code seen on some third-party forums is not a Veichi code (it belongs to other manufacturers' equipment). On Veichi, braking overvoltage is exactly E.OU2, and the answer is decel time plus a resistor. How to size the resistor by power and resistance is covered in a separate article on drive braking.
E.Lu — undervoltage: why it "hangs" after the lights flicker
E.Lu (E.LU on the AC10) is low bus voltage during operation. By default Veichi locks into the fault after a supply sag and waits for an operator command — safe, but inconvenient for pumps and apartment-block plant rooms where no one stands at the panel. The AC10 manual lists the E.LU causes plainly: loss or momentary loss of power, input phase loss, supply voltage too low, or input voltage fluctuation too large. The protection trips when the bus voltage falls below the threshold set by parameter F10.19.
What to check, in order:
- The mains itself. Measure the input voltage under load. If it collapses, the issue is the supply (cable cross-section, contacts, the utility), not the drive.
- The input contactor. A very common, non-obvious culprit is a burnt or chattering input electromagnetic contactor: it briefly breaks the circuit, the bus sags, and the drive catches E.Lu. The manual explicitly advises checking the main-circuit contactor if the supply itself is fine.
- Auto-restart. If the mains naturally flickers and the process tolerates an automatic catch, enable auto-restart on power recovery. The parameters and ranges differ by series (see the table below), so take the value for your exact model.
Auto-restart after a sag: F07.06 and F07.07 — by series
Auto-restart in Veichi is controlled by a pair of parameters: F07.06 — the action on power recovery, and F07.07 — the wait time before restart. An important catch that breaks setups: the F07.06 range differs between series, so there is no "universal" value.
| Series | Parameter | F07.06 range | What the values mean |
|---|---|---|---|
| AC10 | F07.06 / F07.07 | 0~1 | 0 — disabled (a new RUN command is required); 1 — on power recovery the drive automatically catches the motor with speed tracking after the F07.07 wait time. |
| AC310 | F07.06 / F07.07 | 0~2 | 0 — disabled; 1 — restart with speed tracking; 2 — restart per Start mode. Wait time is F07.07. |
| AC01 | F07.06 / F07.07 | verify in the manual for your variant | The same parameter pair (action on power recovery + wait time). Confirm the exact enable value against your AC01 parameter table. |
F07.07 on all series is the wait time (default 0.50 s, range 0.00–60.00 s). Set it so that adjacent equipment can come up after power is applied. During the wait the drive does not accept RUN, but a STOP command cancels the restart — this is built into the safety logic.
A practical tip: for pump stations and ventilation, auto-restart with speed tracking is exactly what you want, because the drive catches an already-spinning motor without a jolt. The full from-scratch commissioning order is in our Veichi setup guide, and the pump sleep/wake-by-pressure logic is in the article on a VFD for a water pump with PID.
The "code → cause → action" table
| Code (AC10 / AC310-AC01) | What it is | Likely cause | Action |
|---|---|---|---|
| E.OC1 / E.oC1 | Overcurrent during acceleration | Short at output/to ground, damaged motor, accel time too short, output cable too long | Isolate the motor; increase accel time (F01.22); shorten the cable or fit an output reactor |
| E.OC2 / E.oC2 | Overcurrent during deceleration | Same + decel time too short | Increase decel time (F01.23); check cable and motor |
| E.OC3 / E.oC3 | Overcurrent at constant speed | Overload, shock load, short, damaged motor | Reduce the load or use a higher-power drive; check the motor by resistance measurement |
| E.OU1 / E.ou1 | Overvoltage during acceleration | Mains too high, input surge, short to ground | Keep the supply within range; add an input reactor |
| E.OU2 / E.ou2 | Overvoltage during deceleration | Regeneration: an inertial load brakes faster than energy dissipates | Increase decel time (F01.23) or fit a braking resistor |
| E.OU3 / E.ou3 | Overvoltage at constant speed | Surges/spikes in the input mains | Add an input reactor; check supply stability |
| E.LU / E.Lu | Undervoltage during operation | Supply sag/loss, input phase loss, chattering input contactor | Check the mains under load and the input contactor; enable auto-restart if needed (F07.06/F07.07) |
Warranty: when it is User Error and when it is a factory defect
An honest answer to "is this under warranty?" depends on the nature of the failure. We assess it neutrally, by technical signs:
| Sign | Verdict | Why |
|---|---|---|
| Charred, melted power terminals | User Error | A poorly tightened bolt at installation: a bad contact heats up and the plastic chars. The local melting is characteristic. |
| A small motor burned on a high-power drive | User Error | No current limit / motor overload protection was set (parameter F10.16 on the AC10) to match the actual small motor. The drive pushed excessive current into the small motor. |
| Input stage blown after a mains spike | Dirty Power | A voltage surge in the grid is not a factory defect but an external supply cause. |
| Healthy IGBT, yet the drive shows E.OC | Factory defect | The power module is intact but the fault persists — a driver-board/solder-quality issue. Covered by warranty. |
Hence a simple prevention routine: re-torque power terminals after the first week of operation, set the current limit to match the real motor, and fit an input reactor on a "dirty" mains. This removes most of the "User Error" column before it ever becomes a problem.
Frequently asked questions
E.OC does not clear even with the motor disconnected — what is it?
If you disconnected the motor cable, ran the drive with no load, and E.OC remained, the cause is inside the drive (the IGBT power module), not the motor or cable. The next step is to measure the resistance between DC+/DC− and U, V, W on a de-energised drive; a near-zero reading confirms a punctured module. This is a service case, not a "reset and carry on".
How does E.OU differ from E.OV?
They are the same thing — overvoltage. Veichi uses E.OU in its manuals (E.ou on the AC310/AC01), while "E.OV" is just another transliteration of over-voltage that does not appear in Veichi documentation. Search and configure by E.OU.
The drive shows E.OU2 every time it stops. Must I fit a resistor?
First try increasing the deceleration time (F01.23): if the load is not time-critical to stop, that is often enough. If the process needs a fast stop of an inertial load (fan, centrifuge, flywheel), you do need a braking resistor, otherwise the braking energy has nowhere to go and the bus exceeds the overvoltage threshold every time.
After every light flicker the pump "hangs" in E.Lu. How do I make it start by itself?
This is Veichi's default behaviour: the drive locks out after a sag. Enable auto-restart via F07.06 (value 1 on the AC10; on the AC310, 1 for a speed-tracking catch or 2 for restart per Start mode) and set the F07.07 wait time. In parallel, check the input contactor — it is often the source of the brief sags.
What is the overvoltage threshold in Veichi?
Per the AC10 manual, E.OU trips when the DC-bus voltage exceeds 820 V for a three-phase input and 400 V for a single-phase input. If your mains is stable yet the code still appears on braking, it is regeneration, not the mains.
Can I "cure" E.Lu by raising the voltage in the parameters?
No. The drive cannot output more than it receives at the input — parameters do not "create" voltage. E.Lu is solved on the supply side (stable mains, an intact contactor, the right cable cross-section) and, if needed, by auto-restart. Raising set-points will not help and may only mask the real mains problem.
