Study Guide Answer Key

Here are the answers to the March 31, 2022 edition of TPO's Exam Study Guide: Under normal operating conditions, what is the maximum acceptable current imbalance? The answer to this question is C, 5%. Voltage imbalance is a major cause of motor failures (especially in lift stations). In three-phase systems, it is important to understand the phase-to-phase voltage will not be equal, and slight differences in voltage will cause much larger current imbalances and will shorten the lifetime of insulation and cause motor overheating. The maximum recommended current imbalance between the legs should never exceed 5% under normal operational conditions according to NEMA