Frequency Converter Troubleshooting

The application of frequency converter is becoming more and more widespread, its daily maintenance management, troubleshooting processing will be frequently encountered. This article introduces the troubleshooting of a general-purpose frequency converter for reference, which can help to ensure the smooth operation of the work and save the outgoing maintenance cost.

Damages on Module

  • Analyzing

The frequency converter power modules mainly contain IGBT, IPM, etc. Check whether the shell has been broken, and check the connection between terminals and the printed circuit board to see if there are signs of erosion. With a multimeter to check whether the current is turned on, or measure the resistance inconsistencies, as well as the power device gate drive resistors if there are inconsistencies, in order to determine which power devices are damaged.

  • Reasons
50Hz 60Hz frequency converter
  1. Poor quality of the device itself;
  2. Severe overcurrent external load imbalance;
  3. Picked up the load capacitance or because of improper wiring capacitance to ground too much, so there is the impact of current power tube;
  4. User grid voltage is too high, or there is a strong transient overvoltage;
  5. The frequency converter power switch overvoltage absorption circuit is damaged, which resulting in over-voltage cannot be effectively absorbed leaving the IGBT;
  6. Filter capacitors is aged, reduce capacity or internal inductance becomes larger, busbar overvoltage absorption capacity decreased, resulting in the bus over voltage is too high and damage the IGBT;
  7. Power device breakdown, or result in the isolation device PCB parts of dust, moisture causing ignition breakdown, leading IGBT, IPM damage;
  8. Improper operation or software defective causing the upper and lower power switching device at the moment of interference and boot, shutdown instability simultaneously turned on;
  9. Lightning, house leaking, entry of foreign matter, inspectors mistakenly hit caused errors;
  10. Through the maintenance and replacement of the filter capacitor, the capacitance due to poor quality, or capacitance receiving line longer than the original, so that inductance increases, causing the bus over-voltage amplitude increased significantly;
  11. Front stage rectifier bridge damage;
  12. No ESD protection measures when repairing, the welding operation damaged the IGBT;
  13. Did not consider the replacement part model and batch consistency, leading to uneven parallel element current damage;
  14. The frequency converter internal protection circuit (over-voltage, over-current protection) damaged and loss their protection;
  15. A group of frequency converter internal power supply is damaged, the change between the two groups of power output values or insulation breakdown.
  • Replacement

Only found the root cause of damage to the first and again to eliminate the possibility of damage to replace the inverter module, otherwise put to the new module can damage it again.

  1. IGBT with insulated gate field effect transistor to prevent electrostatic damage.
  2. between the power module and heat thermal grease coating the contact surface to ensure more than 80%, the size of the tightening torque applied by the fastening screws to ensure good heat dissipation module.
  3. When take the frequency converter apart, take notes of all parts.
  4. Parallel modules require same model and number. When the number cannot be the same, you should ensure that performance is the same as all of the modules in parallel.
  5. For defects copper pieces, put burr rounded sanding to avoid over-voltage discharge tip damage again.
  • Power on after replaced the module

To prevent such accidents energized and burned, we usually install a resistor in the frequency converter main DC circuit. Because of limiting the role of resistance, even if the power failure will not damage the module.

Damages on Rectifier Bridges

  • Analyzing

It can be judged with a multimeter. Loose connections of the rectifier bridge parallel to find the broken one.

  • Reasons
  1. Poor quality of the device itself;
  2. Post-stage circuit or frequency converter power switching device is damaged, resulting in short-circuit current flows through the rectifier bridge.
  3. High-voltage power grid, lightning stroke and over-voltage surges.
  4. The frequency converter lies too close to the grid power transformer.
  5. Lost of input phase, the rectifier bridge burden damage.
  • Replacement
  1. Find and eliminate rectifier the damage on the bridge.
  2. Replace the bridge rectifier, ensure rectifier bridge reliable welding.
  3. Use the same model of the same manufacturer’s rectifier bridge parallel.

Damages on Electrolytic Capacitors

  • Analyzing

The shell appears damaged, cracked plastic jacket pipe, the safety valve is pressed out and small cracks capacitor, terminal severe corrosion, deformation of the cover, falling, indicating an electrolytic capacitor is damaged.

Testing frequency converter components
  • Reasons
  1. Poor quality of the device itself;
  2. Rectifier bridge damage before it is filtered;
  3. Dividing resistor damaged;
  4. Bad capacitor installation;
  5. Thermal environment is not good.
  • Capacitor replacement
  1. It is better to choose the original filter electrolytic capacitor model as replacement. When cannot get the same type, you must use the product with the same current, capacity, dimensions, polarity and installation method;
  2. Replacement of the disassembly process that the electrical connections are secure and reliable, positive and negative cannot be wrong, can be fixed with clamp securely fastened, and not damage the outer insulating covering capacitor, resistor voltage divider as it is plugged in, and measure the resistance value should be dividing evenly;
  3. If the electrolytic capacitor is placed for more than one year, it should be measured leakage current value.

Damages on Fan

  • Analyzing
  1. Measuring the fan supply voltage;
  2. After confirming the fan power supply is normal, as the fan does not working or too slow, the fan is damaged.
  • Reasons
  1. The fan itself is of poor quality;
  2. Adverse environmental, water vapor, condensation, corrosive gases, clogged with dirt or the temperature is too high.
  • Replacement
  1. The best choice is the original model or the fan with better performance;
  2. make record and identify when removing the fan, prevent errors when replacing intact;
  3. When mounting screws of the fan, the torque must be right, not too tight and break the plastic deformation and fracture, not too loose and loose and cause vibration;
  4. For the frequency converter, it is better to equip with a ball bearing fan, because oil-bearing has short service life. Concerned about bearing life, ball bearing fan life will be 5-10 times longer;
  5. The fan withstands high-temperature air, so it fan must be made by metal or temperature resistance plastic, and cannot use low-grade plastic;
  6. The frequency converter power supply should be connected properly. The rotor blades cannot be rubbed against the wire, installed after the energization to try;
  7. Clear the air duct and the heat sink obstruction is very important, because a lot of frequency converters are damaged because of air duct blockage.

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