Why is my transformer humming?
A transformer that hums isn't necessarily defective. An electrical transformer naturally produces a slight hum when it's operating. The laminations in the magnetic circuit expand and contract very slightly…
This part of IEC 61558 deals with the safety aspects of circuit separation transformers for medical premises. This Part shall apply to independent air-cooled, single-phase or three-phase, dry-type (natural or forced), fixed-phase circuit separation transformers intended to supply medical IT schematics for medical premises of Group 2, designed to be permanently connected to fixed wiring and intended to form the IT schematic on the secondary side.
The windings can be coated or uncoated. The rated supply voltage does not exceed 1,000 V AC. The rated power frequency and internal operating frequency do not exceed 500 Hz. The rated power is not less than 0.5 kVA and does not exceed 10 kVA for single-phase and three-phase transformers.
This Part shall apply to transformers which do not include a limitation of the rated power which is the subject of an agreement between the purchaser and the manufacturer. The no-load secondary voltage and the rated secondary voltage do not exceed 250 V alternating current for the single-phase or three-phase transformer (phase voltage). This standard does not cover power supplies. This Part does not apply to external circuits and their components intended to be connected to the primary and secondary terminals of transformers.
Transformers covered by this Part shall be used in applications in which double or enhanced insulation is required between circuits by the installation rules or by the specification of the apparatus for use.
