By Tom Bishop, P.E.
EASA Senior Technical Support Specialist
It’s impossible to balance line-to-line voltages perfectly in three-phase circuits, so they typically differ by a few volts or more. However, if voltage unbalance exceeds 1%, it can markedly decrease the performance and energy efficiency of three-phase motors while increasing the likelihood of premature failure. Avoiding these issues requires a proactive approach that includes installing adequate protective devices and periodically checking for voltage unbalance at the motor terminals.
The article covers:
- What it is
- Common causes
- Effects of unbalanced voltage
- Testing for unbalanced voltages and single-phasing
- Ways to correct unbalanced voltages
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