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NDC Proves That Size Does Matter

Danfoss VLT6225

(March 2010)
NDC are well known for our capabilities across a wide range of AC Inverter repairs, but the ability to handle and test the largest Inverters is an additional element in our service portfolio that marks us out from our competitors.

We regularly handle the large units from HVAC applications which many independent repair organisations would struggle to cope with due to physical handling and testing requirements. NDC's latest such job was to repair a Danfoss VLT6225 132KW HVAC Inverter with badly damaged output stages. During the repair process, the IGBT Modules were all replaced even though only two were physically damaged. This is important as the remaining IGBT's will have been stressed and there is a high possibility that they will fail in the near future if not replaced. The repair process is then carefully managed through to conclusion. After a substantial rebuild of the drive stages on the drive card, the drive is carefully monitored through the use of an Oscilloscope to verify that the output stages are driving at the correct frequency and amplitude. This action is performed without a DC Bus Voltage applied. Once verified, the unit is assembled ready for final test but not before the Capacitor bank is independently tested through an applied 600V External bus.

During the final test, the Drive is load-tested on a Dynamometer to allow full current capacity to be tested.

NDC's purpose-designed repair centre allows the handling of this size of drive through the use of overhead lifting equipment, as it would not be possible to move a 200KG unit within a standard repair facility.


NDC holds Advanced Safety Certification in Electrical Testing of HV Drives in excess of 100kW


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