Dan foss VLT -2800 Series VFD . Testing the IGBT of Inverter With Multimeter

Here's a step-by-step guide for IGBT testing in Danfoss VLT 2800 VFD with a multimeter, including diode testing:
Precautions:
1. Ensure the VFD is turned off and disconnected from power before testing.
2. Use a multimeter with a diode test function (usually denoted by a diode symbol).
IGBT Testing with in VFD / inverter :
1- put the black probe of multimeter on vfd DC + and red probe of multimeter one by one on vfd R, S , T . and U, V, W. so multimeter should give the reading of diode voltage drop 0.3 - 0.7 V . 2- put the Red probe of multimeter on vfd DC - and black probe of multimeter one by one on vfd R, S , T and U , V , W. so multimeter should give the reading of diode voltage drop 0.3 - 0.7 V .
IGBT Testing:
1. Locate the IGBT modules (usually labeled as "IGBT" or "Power Module").
2. Set the multimeter to the diode test function.
3. Connect the multimeter leads to the IGBT terminals (usually labeled as "C" for collector, "E" for emitter, and "G" for gate).
4. Measure the voltage drop across the IGBT in both directions (forward and reverse bias).
5. Compare the readings to the manufacturer's specifications or a known good IGBT module.
6. Repeat the process for all IGBT modules in the VFD.
Diode Testing:
1. Locate the diodes (usually labeled as "D" or "CR").
2. Set the multimeter to the diode test function.
3. Connect the multimeter leads to the diode terminals (anode and cathode).
4. Measure the voltage drop across the diode in both directions (forward and reverse bias).
5. Compare the readings to the manufacturer's specifications or a known good diode.
6. Repeat the process for all diodes in the VFD.
Interpretation:
A healthy IGBT or diode should show a voltage drop of around 0.3-0.7V in the forward bias direction and infinity (or very high resistance) in the reverse bias direction.
A shorted or damaged IGBT or diode will show a very low resistance or voltage drop in both directions.
An open or faulty IGBT or diode will show infinity or very high resistance in both directions.
By following these steps and interpreting the results, you can identify faulty IGBTs or diodes in the Danfoss VLT 2800 VFD and perform necessary repairs or replacements.

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