UFC 3 -520-01
June 10, 2002
Closed Transition Switch -- Transfer switch that provides a momentary paralleling of
both power sources during a transfer in either direction. The closed transition is
possible only when the sources are properly interfaced and synchronized.
Constant Voltage Transformer
--A ferroresonant transformer used for voltage
regulation in single -phase circuits.
Current Limiting Circuit Breaker--A circuit breaker that does not utilize a fusible
element, and that when operati ng within its predetermined current -limiting range, limits
the let-through I2t to a value less than the I2t of one -half cycle of the expected
Current Limiting Fused Circuit Breaker--A circuit breaker in combination with
integral current-limiting fuses that, when it interrupts a current within its specified current
limiting range, purposely introduces an impedance so as to reduce the current
DC Link--The direct-current power interconnection between rectifier or rectifier/charger
and inverter function units.
Delayed Transition--A timed disconnection of the load from the power sources during
transfer, primarily to allow for the decay of motor residual voltage.
Earth Ground--An electrical connection to earth obtained by a grounding electrode
--An electromechanical relay that operates principally
of an electromagnetic element that is energized by the input quantity.
--A relay that operates
by physical movement
resulting from electromagnetic, electrostatic, or electrothermic forces created by the
Emergency Lighting System--A system capable of providing minimum required
illumination specified in NFPA 101, Code for Safety to Life from F ire in Buildings and
Structures, Section 5.9. It includes the lighting units, related backup power source(s),
and required connections.
Equipment Grounding Conductor-- The conductor used to connect the noncurrent
carrying parts of conduits, raceways, and e quipment enclosures to the grounded
conductor (neutral) and the grounding electrode at the service equipment (main panel)
or secondary of a separately derived system, such as an isolation transformer.
Existing Facility--A facility is existing if changes to be made are cosmetic or minor in