Zhejiang Shuyi Electric Co. Ltd
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Common Faults, Causes, and Solutions for Frequency Converters
VFD

1. Overcurrent Faults

1.1 Overcurrent during Acceleration (E.oC1)

Causes:

  • Excessive load inertia combined with too short acceleration time, leading to instantaneous overcurrent at startup.
  • Motor faults, such as winding short circuits or grounding, causing abnormal current.
  • Short circuit on the converter output side due to damaged cables or improper connections.
  • Improper parameter settings, such as excessively high torque boost, resulting in excessive starting current surge.

Solutions:

  • Extend the acceleration time by adjusting parameters like F01.22 (Acceleration Time 1) to ensure smooth motor startup.
  • Inspect the motor using professional tools to measure winding insulation resistance and DC resistance; repair or replace the motor if damaged.
  • Check the converter output wiring for damage, aging, or loose terminals, ensuring correct and short-free connections.
  • Adjust the torque boost value (e.g., F04.01 Torque Boost) to avoid excessive current surge.

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1.2 Overcurrent during Deceleration (E.oC2)

Causes:

  • Too short deceleration time, leading to unabsorbed regenerative energy and increased DC bus voltage.
  • High load inertia causing excessive current during deceleration due to motor inertia.
  • Incorrect brake resistor selection or faulty brake unit, failing to dissipate regenerative energy effectively.

Solutions:

  • Lengthen the deceleration time by modifying parameters such as F01.23 (Deceleration Time 1) for smooth deceleration.
  • For high-inertia loads, install a brake resistor or a higher-power brake unit (e.g., a 75Ω, 780W resistor for a 7.5kW motor in a 380V system).
  • Check the brake resistor and unit for damage or malfunction, replacing faulty components as needed.

1.3 Overcurrent during Constant Speed (E.oC3)

Causes:

  • Sudden load increase (e.g., mechanical jamming or abrupt load changes) leading to excessive motor current.
  • Mismatch between motor and converter ratings, causing converter overload.
  • Converter internal faults, such as damaged power modules or faulty current detection circuits.

Solutions:

  • Inspect the mechanical load for jamming or abnormal operation and resolve accordingly.
  • Verify motor-converter compatibility, ensuring the motor’s rated current is within the converter’s capacity.
  • Contact professional technicians to check power modules and current detection circuits, replacing damaged parts.
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2. Overvoltage Faults

2.1 Overvoltage during Acceleration (E.ou1)

Causes:

  • Short acceleration time causing rapid speed rise and unabsorbed regenerative energy, increasing DC bus voltage.
  • Excessive input voltage beyond the converter’s allowable range.
  • Faulty brake unit or unconnected brake resistor, failing to absorb regenerative energy.

Solutions:

  • Extend acceleration time (e.g., F01.22) to ensure gradual speed increase.
  • Monitor input voltage to ensure it stays within the converter’s allowable 波动 range (e.g., -15%~10% for T3 models).
  • Check the brake unit and resistor for proper connection and functionality, repairing or replacing as necessary.

2.2 Overvoltage during Deceleration (E.ou2)

Causes:

  • Short deceleration time generating excessive regenerative energy.
  • High load inertia leading to excessive energy feedback during deceleration.
  • Incorrect brake resistor or faulty brake unit.

Solutions:

  • Increase deceleration time (e.g., F01.23) for gradual speed reduction.
  • Upgrade the brake resistor or unit for high-inertia loads and verify their specifications (e.g., resistance and power ratings).
  • Inspect brake components for proper operation and replace faulty parts.

2.3 Overvoltage during Constant Speed (E.ou3)

Causes:

  • Sudden grid voltage surges or fluctuations.
  • Load in generating mode (e.g., potential loads descending), converting the motor into a generator and feeding back energy.
  • Faulty voltage detection circuit in the converter, causing false overvoltage alarms.

Solutions:

  • Install a voltage stabilizer to mitigate grid voltage fluctuations.
  • Use brake resistors or energy feedback devices for generating loads to dissipate or 回馈 regenerative energy.
  • Have professionals inspect and repair the voltage detection circuit.

3. Overload Faults

3.1 Motor Overload (E.oL1)

Causes:

  • Prolonged heavy load operation due to mechanical jamming or transmission faults.
  • Incorrect motor parameter settings (e.g., rated power/current mismatching the actual motor).
  • Improper electronic thermal relay settings, failing to protect the motor in time.

Solutions:

  • Inspect the mechanical load, clear jams, and repair transmission components to reduce load.
  • Verify and correct motor parameters in the F02 group (Motor 1 Parameters).
  • Adjust overload protection thresholds (e.g., F10.58 Motor Overload Start Threshold) according to the motor’s rated current.

3.2 Converter Overload 1 (E.oL2), Converter Overload 2 (E.oL3), Converter Overload 3 (E.oL4)

Causes:

  • Excessive load exceeding the converter’s rated capacity.
  • Incorrect converter sizing, with selected power lower than the actual load requirement.
  • High ambient temperature impairing heat dissipation, leading to overheating.
  • Lack of maintenance during prolonged continuous operation.

Solutions:

  • Reduce load by troubleshooting equipment faults and optimizing operation.
  • Re-select a converter with appropriate power ratings based on load requirements.
  • Improve ventilation and clean heat sinks to ensure proper heat dissipation; add cooling fans if necessary.
  • Perform regular maintenance, including dust cleaning and fan inspection.

4. Undervoltage Faults

4.1 Undervoltage during Operation (E.Lu)

Causes:

  • Input power phase loss due to blown fuses or broken wires.
  • Low input voltage below the converter’s allowable minimum.
  • Faulty power detection circuit in the converter, causing false undervoltage alarms.
  • Insufficient grid capacity leading to voltage sag during load startup.

Solutions:

  • Check input power lines, replace fuses, and repair broken wires.
  • Measure input voltage and address grid issues with the power provider if below standards.
  • Have technicians repair or replace the power detection circuit.
  • Install a voltage stabilizer for grids with insufficient capacity.

5. Overheating Faults

5.1 Rectifier Module Overheating (E.oH1)

Causes:

  • Faulty cooling fan (damage or low speed) leading to poor heat dissipation.
  • Dust accumulation on heat sinks, reducing cooling efficiency.
  • Rectifier module faults (e.g., component aging or internal short circuits).
  • Ambient temperature exceeding the converter’s operating range (-10℃~+50℃).

Solutions:

  • Replace damaged fans and clean fan blades/dust from heat sinks to ensure proper airflow.
  • Clean heat sinks thoroughly to restore heat dissipation performance.
  • Test and replace faulty rectifier modules if aging or damaged.
  • Improve ambient conditions, using air conditioning if necessary to maintain proper temperature.

5.2 IGBT Module Overheating (E.oH2)

Causes:

  • Poor heat dissipation due to loose contact between the IGBT module and heat sink, or faulty fans.
  • Excessive operating current due to prolonged overload.
  • IGBT module aging or quality issues leading to increased heat generation.

Solutions:

  • Ensure tight contact between the IGBT module and heat sink, reapplying thermal grease if needed.
  • Clean cooling components and check for excessive load current; replace faulty IGBT modules.
  • Monitor load conditions and address overload issues to prevent excessive current.
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6. Phase Loss Faults

6.1 Input Phase Loss (E.iLF)

Causes:

  • Open circuit in input power lines (e.g., blown fuses, broken wires).
  • Poor contact in power switches, causing missing phase input.
  • Faulty input phase-loss detection circuit in the converter.

Solutions:

  • Inspect and repair input power lines, replacing fuses and fixing connections.
  • Check and replace faulty power switches to ensure stable phase input.
  • Repair or replace the input phase-loss detection circuit by professional technicians.

6.2 Output Phase Loss (E.oLF), U-Phase Loss (E.oLF1), V-Phase Loss (E.oLF2), W-Phase Loss (E.oLF3)

Causes:

  • Open circuit in output cables due to damage or loose terminals.
  • Faulty output drive circuit in the converter, preventing phase output.
  • Motor winding open circuit (e.g., one-phase winding failure).

Solutions:

  • Check output cables for damage and secure connections; repair or replace as needed.
  • Test the converter’s output drive circuit and replace faulty components.
  • Use professional tools to test motor windings and repair/replace the motor if faulty.

7. Communication Faults

7.1 Modbus Communication Fault (E.CE)

Causes:

  • Poor communication cable connection (loose connectors, damaged cables).
  • Mismatched communication parameters (baud rate, data format, address) between the converter and host.
  • Damaged communication interface in the converter.
  • Faults in host communication software or equipment.

Solutions:

  • Inspect and secure communication cables, replacing damaged ones.
  • Verify and match communication parameters in the F12 group (Communication Parameters), such as F12.02 (Baud Rate) and F12.03 (Data Format).
  • Repair or replace the converter’s communication interface if damaged.
  • Troubleshoot host-side issues, including software and hardware, to ensure compatibility.

Web:www.cnshuyi.com;
Tel/Fax: 0086-577-62840011
WhatsApp: 008613355775769

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