Voltage unbalance can cause severe heating in motors and large DC power converters.
Although most voltage unbalance is caused by unequal loading among phases, shifts in voltage phase angle can also cause unbalance. This unbalance is especially pernicious since it’s only seen in a delta hookup.
In this situation, a wye measurement will show balanced voltages, while the delta circuit could be very unbalanced. The theory behind this is described here, along with lab tests and a real-world example.
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