Voltage unbalance can cause severe heating in motors and large DC power converters and an increase in harmonic currents.
Fortunately unbalance is easy to measure with PMI recorders and ProVision – only standard RMS voltage stripchart data is required from the recorder.
Ideally the voltages of a polyphase system are all equal in magnitude.
Due to uneven single-phase loading, differences in impedance in connectors, transformations through open delta and other non-symmetric transformer arrangements, and other factors, the line voltages are often not exactly equal as delivered to a load.
Small differences in voltage are usually harmless, but as the difference increases, problems can quickly develop.
Voltage unbalance in a three-phase system can be defined as the max deviation from the 3-phase average, divided by the average...