This part 2 of IEC 61558 applies to stationary or portable, single-phase or polyphase, air-cooled isolating transformers, associated or othervvise, having a rated supply voltage not exceeding 1000 V a.c. and rated frequency not exceeding 500 Hz, the rated output not exceeding:
- 25 kVA for single-phase transformers;
- 40 kVA for polyphase transformers.
This standard is also applicable to isolating transformers vvithout limitation of the rated output, hovvever such transformers are considered as special transformers and are subjected to an agreement betvveen the purchaser and the supplier.