A transformer which after abnormal use, fails to function by an interruption of the input circuit but presents no danger to the user or surroundings.
ELV (Extra- ow oltage)
A voltage not exceeding the upper limit of band 1
A voltage which does not exceed 50 V a.c. or 120 V ripple free d.c. between any conductor and earth, in a circuit, which is isolated from the supply mains by means such as a safety isolating transformer.
PELV – circuit
An ELV circuit with protective separation from other circuitsand which, for functional reasons, may be earthed and/or the exposed-conductive-parts of which may be earthed.
FELV – circuit
An ELV circuit having the ELV voltage for func- tional reasons and not fulfilling the requirements for SELV or PELV.
SELV, PELV, FELV
S = Safety
P = Protective
F = Functional
ELV = Extra Low Voltage