ABSTRACT
Constant-voltage transformers (CVT) have been used for many years, primarily as a noise-isolation device. Recently, they have found value when applied as a voltage-sag protection device for industrial and commercial facilities. e purpose of this section in the handbook is to give power-system engineers and facility engineers who are unfamiliar with the CVT technology (also known as ferroresonant transformers) the insights and information necessary to determine the types of electric-service-supply events that CVTs can mitigate. Items covered in this chapter include operation, characteristics, applications, speci–- cations, and sizing guidelines of CVTs. e goal here is not to duplicate information currently available but, rather, to collect information into a single location and then supplement it to provide:
Adequate information and procedures to applications personnel in e›ectively selecting CVTs for voltage-sag ride-through protection
Application notes to demonstrate how CVTs can improve process voltage-sag ride-through
e industrial use of CVTs (also called ferroresonant transformers) goes back to the early 1940s. Living in the United States during the 1930s, Joseph G. Sola, a German-born engineer, discovered the CVT
9.3 Procurement Considerations ........................................................ 9-17 What to Look for When Purchasing a Constant-Voltage Transformer
9.4 Typical Service, Storage, and Shipment Conditions ................. 9-19 9.5 Nameplate Data and Nomenclature ............................................9-20 9.6 New Technology Advancements ..................................................9-20 9.7 Addendum ....................................................................................... 9-21 References .................................................................................................... 9-23
technology [1,2] based on a single transformer rather than an arrangement of transformers, separate –lters, and capacitors. is innovation provides several important advantages: its inherent robustness (CVT consists of just three or four windings and a high-reliability capacitor), its imperviousness to continuous short circuits (whether it is turned on into a short circuit or from full load), and its capability to maintain output-voltage stabilization on a cycle-to-cycle basis for signi–cantly large overvoltages and undervoltages.
