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Applies to stationary, single-phase or polyphase, air-cooled (natural or forced) isolating transformers for the supply of group II medical locations, designed to be permanently connected to the fixed wiring of IT supply system, having a rated supply voltage not exceeding 1000 V a.c. and rated frequency not exceeding 500 Hz. The rated output shall not be less than 3 kVA and shall not exceed 10 kVA. The no-load output voltage and the rated output voltage shall not exceed 250 V a.c. single-phase or polyphase (phase-to-phase voltage). Isolating transformers are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification. This standard is applicable to dry-type transformers. The winding may be encapsulated or non-encapsulated.