Power Quality Analyzer

Equipment:  Fluke 434 Three-Phase Power Quality AnalyzerCompany:    Data IQ

Problem:      Mains Voltage Generator suspected of     damaging inverter when connected

Mains voltage measured at Isolator to Danfoss VLT5202 from 540KVA Generator

An 8 minute sample was taken over the 3 phases from the 540KVA generator with the pneumatic crusher running, using the Fluke 484 the off load incoming voltage was approx. 448V across all 3 phases. However under load, the mains voltage dropped as low as 186V before recovering.

L1 phase in more detail

Zoom in


In our opinion this level of mains perturbation is unacceptable for the incoming supply to this inverter, and is without doubt the cause for the initial failure of the unit. Adding filtration to the mains circuit will have no effect on this level of disturbance.

(The bolt on the mains L3 incoming isolator was also loose – this would cause an imbalance under load at the inverter, causing further problems)

The Generator appears to be the main cause of the failure and will need to be checked, serviced or replaced in order to rectify the problem.