A transformer with no electrical connection between primary and secondary windings, used in elevator installations to provide galvanic isolation for sensitive control circuits or safety extra-low voltage supplies.
Full Definition
Isolation transformers in elevator installations serve several purposes: they provide galvanic isolation between the building mains and elevator control circuits to eliminate ground loops and reduce electrical noise; they step down supply voltage to SELV levels for car lighting and control; and they protect sensitive electronic components from voltage transients on the building supply. In machine rooms where personnel must work on live circuits, isolation transformers reduce electric shock risk by breaking the earth fault current return path. They are specified with appropriate screening between primary and secondary windings to reduce capacitive coupling of high-frequency noise. Core-and-coil construction should be rated for the continuous load and harmonic content of the elevator power supply. Insulation resistance testing is part of the annual inspection.
