Hope65 overvoltage faults usually occur when the input voltage is too high or when the motor/load regenerates energy back into the VFD DC bus. This is common during fast deceleration, high-inertia loads, fans, blowers, conveyors, hoists, centrifuges, and any machine where the load can drive the motor.
E05 occurs during acceleration, E06 during deceleration, and E07 during constant-speed operation. E08 indicates snubber/buffer resistor overload, usually linked to abnormal input voltage. E09 indicates undervoltage, commonly caused by instantaneous power failure, low supply voltage, unstable power, or internal DC bus/power circuit issues.
Do not repeatedly reset voltage faults. Measure the input voltage, identify whether the fault happens during acceleration, deceleration, running, or power disturbance, check braking resistor requirement, correct the root cause, then reset and test safely.
Only trained and qualified electrical personnel should inspect input power wiring, VFD terminals, braking resistor wiring, contactors, power circuits, or panel components.
Before touching terminals or wiring, switch off all input power, wait at least 10 minutes, and confirm that the DC bus voltage has discharged to a safe level. Do not change wiring while power is ON.
This article helps diagnose and correct Hope65 Series Smart AC Drive / VFD voltage-related faults. These faults are different from current faults. Current faults are usually related to motor/load current demand, while voltage faults are usually related to input supply condition, DC bus voltage, regenerative energy, braking design, and power disturbance.
Overvoltage means the DC bus voltage has risen beyond the allowed protection level. This can happen when the supply voltage is too high or when the motor acts like a generator and feeds energy back into the VFD during deceleration or load-driven operation. Undervoltage means the DC bus voltage has dropped below the safe operating level, usually due to weak supply, instantaneous power loss, voltage dip, loose input wiring, or upstream power issue.
01 Measure SupplyCheck input voltage at VFD input terminals and confirm it matches the drive voltage class. | 02 Check TimingIdentify whether the fault occurs during acceleration, deceleration, constant speed, or power disturbance. | 03 Correct BrakingFor regenerative loads, increase deceleration time or use a correctly selected braking resistor. |
| Product Series | Slanvert Hope65 Series Smart AC Drive / VFD |
| Fault Codes Covered | E05 acceleration overvoltage, E06 deceleration overvoltage, E07 constant-speed overvoltage, E08 snubber/buffer resistor overload, E09 undervoltage. |
| Typical Applications | Fans, blowers, pumps, conveyors, centrifuges, mixers, windmilling loads, high-inertia machines, rapid-stop systems, hoists, and general industrial motor-control systems. |
| User Level | Qualified electrical technician, maintenance engineer, panel builder, machine integrator, or automation engineer. |
The same voltage fault group can have different causes depending on when the fault appears. Use the timing map below before changing parameters or replacing hardware.
E05 Acceleration
| E06 Deceleration
| E07 Constant Speed
| E09 Power Dip
|
If the fault happens during stopping, focus on regenerative energy, deceleration time, and braking resistor. If it happens randomly or during stable running, focus on input voltage, load-driven motor behavior, and power quality.
| Code | Fault Type | Likely Cause | First Corrective Action |
|---|---|---|---|
| E05 | Overvoltage during acceleration | Abnormal input voltage, external force dragging motor, acceleration too short, or no braking resistor where required. | Correct input voltage, remove external driving force, increase acceleration time, or check braking requirement. |
| E06 | Overvoltage during deceleration | Input voltage too high, regenerative load, deceleration too short, or no braking resistor where required. | Increase deceleration time, correct supply voltage, and use/check braking resistor for high-inertia loads. |
| E07 | Overvoltage during constant-speed operation | Input voltage too high or external force/load drives the motor during operation. | Correct input voltage and check whether the machine/load is regenerating into the drive. |
| E08 | Snubber / buffer resistor overload | Input voltage outside specified range. | Adjust voltage to the range required by the specification and check power quality. |
| E09 | Undervoltage | Instant power failure, low input voltage, abnormal bus voltage, rectifier/buffer circuit issue, drive board issue, or control board issue. | Stabilize input voltage, check supply wiring, then reset. Contact support if internal circuit issue is suspected. |
Voltage faults should be diagnosed from the supply side, DC bus behavior, motor/load behavior, and braking system.
Input Supply L1/L2 or R/S/T
| → | DC Bus Internal Energy Link
| → | Motor / Load Regenerative Source
|
Braking Resistor Energy Dissipation
| + | Ramp Settings Acceleration / Deceleration
| + | Power Quality Site Supply Check
|
E05 appears when the DC bus voltage rises too high during the acceleration stage. Although acceleration normally consumes energy, overvoltage can still occur if the input voltage is already high, if the motor is being driven by an external force, if the acceleration profile is unsuitable, or if the machine/load condition creates regenerative behavior.
| Likely Cause | How to Confirm | Corrective Action |
|---|---|---|
| Abnormal input voltage | Measure voltage at the VFD input terminals before and during start. | Correct supply voltage to the normal range and verify voltage class. |
| External force drives the motor during acceleration | Fan is windmilling, load is moving, conveyor is pulled, or hoist/load is driving shaft. | Remove external driving force or use suitable braking/regeneration handling. |
| Acceleration time too short | Fault occurs only while speed is ramping up. | Increase acceleration time and retest at low speed. |
| Braking resistor not installed where required | Machine has high inertia or frequent speed changes. | Check braking resistor requirement and install correctly rated braking resistor if required. |
E06 is one of the most common voltage faults in high-inertia applications. When the VFD decelerates the motor quickly, the motor can behave like a generator. The generated energy flows back to the VFD DC bus. If this energy is not absorbed or dissipated, the bus voltage rises and the drive trips on overvoltage.
| Likely Cause | How to Confirm | Corrective Action |
|---|---|---|
| Input voltage too high | Measure VFD input voltage under normal and loaded condition. | Correct input voltage and stabilize supply. |
| External force drives motor during deceleration | Load continues spinning or pulling the motor while VFD is trying to stop. | Remove external driving force, use longer deceleration, or use braking resistor. |
| Deceleration time too short | Fault occurs only during stopping or speed reduction. | Increase F0-14 deceleration time and test again. |
| No braking resistor where required | High-inertia load, frequent stop, rapid stop, or process requires short stopping time. | Install correctly selected braking resistor on the specified braking terminals. |
E07 occurs while the drive is already running at stable speed. This is usually caused by input voltage being too high or by the load driving the motor during operation. It may appear in fan systems affected by airflow, conveyors being pulled by material, hoisting/lowering applications, or machines where the load has enough stored energy to push the motor.
| Likely Cause | How to Confirm | Corrective Action |
|---|---|---|
| Input voltage too high | Input voltage is above acceptable operating range or rises during operation. | Correct input supply voltage and check transformer/tap/supply condition. |
| Load drives motor during running | Motor is pushed by airflow, gravity, belt pull, process pressure, or moving load. | Reduce regenerative effect, add braking solution, or revise machine control sequence. |
| Incorrect application control logic | Machine speed/load changes unexpectedly while command frequency remains stable. | Check PLC sequence, mechanical interlocks, brake timing, and load release behavior. |
E08 is related to the snubber or buffer resistor overload condition. The primary field check is the input voltage range. If the VFD input voltage is outside the specified range, internal power components may experience abnormal stress and trigger this fault.
| Likely Cause | How to Confirm | Corrective Action |
|---|---|---|
| Input voltage not within specified range | Measure input voltage at VFD terminals and compare with model voltage class. | Adjust supply voltage to the required range. Check transformer, supply wiring, fuse, contactor, and voltage fluctuation. |
| Repeated abnormal power cycling | Fault appears after frequent ON/OFF switching or unstable power input. | Avoid rapid input power cycling. Stabilize supply and check upstream contactor sequence. |
E09 means the VFD detected low DC bus voltage or an input power condition that cannot support safe operation. This may be caused by instantaneous power failure, low input voltage, loose input wiring, poor contactor/fuse condition, weak transformer, undersized cable, voltage dip during load start, or internal power circuit issue.
| Likely Cause | How to Confirm | Corrective Action |
|---|---|---|
| Instantaneous power failure | Fault occurs during mains dip, generator transfer, contactor drop, or power interruption. | Stabilize supply, check upstream control power, and reset after power is normal. |
| Input voltage too low | Measured voltage at VFD input is below required range, especially under load. | Correct supply voltage, cable size, transformer capacity, and upstream connection. |
| Loose input wiring or weak contactor | Voltage drops when machine starts, contactor vibrates, terminals heat, or fuse holder is loose. | Tighten terminals, replace faulty contactor/fuse holder, and verify connection quality. |
| Abnormal bus voltage or internal power circuit issue | Input voltage is normal but E09 remains or repeats without external supply issue. | Stop operation and contact technical support. |
A voltage fault should always include input voltage verification. Measurements should be performed only by qualified personnel using correctly rated instruments and safe electrical procedures.
| Check | How to Check | Why It Matters |
|---|---|---|
| Voltage class | Compare drive nameplate with actual supply: single-phase 220 V class or three-phase 380 V class. | Wrong voltage class can cause immediate damage or repeated fault. |
| No-load input voltage | Measure at VFD input terminals before motor run. | Confirms the basic supply condition at the drive, not just at the panel. |
| Loaded input voltage | Measure while the motor is running or during the stage where fault occurs. | Weak supply may look normal at rest but dip under load. |
| Phase balance | For three-phase models, compare phase-to-phase voltages. | Unbalanced supply can increase stress and cause unstable operation. |
| Power path | Inspect breaker, fuse, contactor, cable, terminals, and upstream supply path. | Loose or worn components can cause voltage drop, heating, and undervoltage faults. |
During deceleration, a high-inertia motor/load can generate electricity and feed energy back into the VFD DC bus. If the DC bus voltage rises above the protection threshold, the VFD trips on overvoltage. A braking resistor dissipates this regenerative energy as heat and allows faster deceleration where the application requires it.
| Application Condition | Risk | Recommended Check |
|---|---|---|
| Large fan or blower | Windmilling or high inertia can regenerate energy. | Increase stop time, check speed tracking, and evaluate braking resistor if fast stop is required. |
| Conveyor with heavy load | Moving load can drive the motor during stop. | Check load control, deceleration time, mechanical brake, and braking resistor requirement. |
| Hoist or vertical load | Gravity can drive the motor and raise DC bus voltage. | Do not trial randomly. Validate brake timing, safety sequence, braking resistor, and drive sizing with technical support. |
| Rapid stop requirement | Short deceleration can cause E06. | Increase deceleration time or use a properly rated braking resistor. |
Check these parameters during diagnosis. Change parameter values only after confirming application requirements and machine safety.
| Parameter / Group | Purpose | Voltage Fault Relevance |
|---|---|---|
| F0-13 | Acceleration time | Too short acceleration can contribute to E05 in certain load conditions. |
| F0-14 | Deceleration time | Too short deceleration is a common cause of E06 in high-inertia loads. |
| F1-11 | Acceleration/deceleration method | Linear or S-curve ramp selection affects mechanical shock and voltage behavior during speed changes. |
| F1-14 | Dynamic braking point | Related to braking action threshold. Adjust only with correct technical understanding. |
| F1-15 | Brake usage rate | Affects braking resistor usage behavior where braking is applied. |
| F8-03 | Overvoltage stall gain | Controls response strength for overvoltage stall handling. |
| F8-04 | Overvoltage stall protection voltage | Defines overvoltage stall protection threshold behavior. |
| F8-47 | Instantaneous failure tolerance function | Relevant for power dips and undervoltage behavior. Configure only after understanding machine stop requirements. |
| F8-13 to F8-15 | Fault history | Confirms whether the repeated fault is E05, E06, E07, E08, or E09. |
| Application | Common Voltage Fault Cause | Practical Check |
|---|---|---|
| Fan / blower | Windmilling, high inertia, short deceleration, or airflow-driven rotation. | Increase deceleration time, check speed tracking, and evaluate braking resistor for fast stop. |
| Conveyor | Heavy moving load drives motor during stopping. | Check load pull, belt angle, mechanical brake, stop timing, and deceleration time. |
| Pump | Pressure surge, reverse flow, water hammer, or process back-drive. | Check valve condition, process pressure, stop profile, and pump rotation behavior. |
| Mixer / centrifuge | Large inertia continues rotating during deceleration. | Use longer deceleration or braking resistor sized for the duty cycle. |
| Hoist / vertical load | Gravity-driven regeneration and brake timing issue. | Do not trial randomly. Validate brake sequence, braking resistor, load safety, and drive suitability with support. |
After correcting the suspected cause, retest carefully. Do not immediately run at full speed and full load.
To reduce troubleshooting time, share the following details:
Smidnya technical support can help review your fault code, drive model, motor nameplate, input voltage readings, load inertia, deceleration requirement, braking resistor setup, and F8 fault history to identify the root cause.