A 22kW Danfoss VLT Variable Frequency Drive was brought to our workshop after developing a power-up failure. The fault prevented the drive from starting, thereby affecting process operations within the client’s production facility.

Our technical team carried out a detailed diagnostic procedure, including cold testing and power section evaluation, to identify the source of the fault. During the inspection, abnormalities were detected within the drive’s power circuit.

Following the diagnosis, the defective components were replaced and all related connections were rechecked before reassembly. The drive was subsequently energized and tested under load conditions using a suitable electric motor to validate stable operation and output performance.

The project execution covered the following activities:

• Cold diagnostic testing was performed to ascertain the electrical integrity of the drive
• Electrical continuity checks between phases and earth
• Safe isolation, tagging, and disconnection of internal power connections
• Replacement of faulty thyristors and inrush card components
• Functional testing of the drive under load conditions

drive was successfully returned to service in accordance with OEM operational standards, helping the client avoid extended production interruptions and replacement costs.