Understanding transfer switch operation

摘要

When utility power is interrupted, power system failure is not an option for many facilities. Standby power systems have many components, including transfer switches that must be designed correctly. During power transitions, transfer switch timing and sequence is critical to ensure proper system operation. Consulting engineers must understand transfer switch types, timing requirements, ratings, and the types of standby systems where transfer switches are used to transfer to backup power. The basis of this article is NFPA 70-2014: National Electrical Code (NEC) unless otherwise noted.