54 UPS Bypass Switches Uninterruptable Power Supply A UPS is an Uninterruptible Power Supply or Uninterruptible Power Source, it is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. UPSs are typically used to protect hardware such as telecommunications equipment, computers, data centres, and other important equipment where an unexpected power disruption could cause injuries, fatalities, data loss or serious business disruption. A UPS Bypass Switch allows the Load to be switched between the UPS and the Mains Electrical Supply without interruption of supply to the Load. UPS Bypass switches can be either: • Break Before Make: (Usually smaller UPS's that don't have a static changeover switch) • In a Tail End Bypass switch the switch contacts open very briefly between the UPS (NORMAL) and BYPASS positions on the phase conductor. Wraparound • Wraparound Bypass switches have the Mains - UPS Input (power to UPS) - UPS Output and Load connected through the switch. • Wraparound Bypass switches typically come in either three position NORMAL - TEST - BYPASS or four position OFF - NORMAL - TEST – BYPASS NOTE: Tail End Bypass switches DO NOT isolate the Mains supply to the UPS • In a Wraparound Bypass switch the switch contacts open very briefly between the NORMAL and TEST positions but overlap between the TEST and BYPASS positions on the phase conductor • Make Before Break: • On both the Tail End and Wraparound Bypass switches all of the switch contacts overlap between all positions ensuring the contacts don't Open causing an interuption of the Load Typically UPS Bypass switches come in 2 types: • Tail End • Tail End Bypass switches are like a source changeover switch and supply power to the load from either the UPS or Mains. • Tail End Bypass switches typically have 2 positions, UPS - BYPASS or NORMAL - BYPASS • With a Wraparound Bypass switch the Mains & Load are Isolated from the UPS when in either the OFF or Bypass positions, this allows for the UPS to be removed without effecting the supply to the load UPS ISOLATOR TAIL END BYPASS SWITCH FROM UPS SUPPLY FROM MAINS SUPPLY MAINS ISOLATOR LOAD LOAD UPS ISOLATOR FROM UPS SUPPLY FROM MAINS SUPPLY MAINS ISOLATOR
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