This part of IEC 61558 deals with the safety of variable transformers for general applications and power supply units incorporating variable transformers for general applications. Variable transformers incorporating electronic circuits are also covered by this document. NOTE 1 – Safety includes electrical, thermal, mechanical and chemical aspects. Unless otherwise specified, from here onward, the term transformer covers variable transformers for general applications and power supply units incorporating variable transformers for general applications. For power supply units (linear) this document is applicable. For switch mode power supply units, IEC 61558-2-16 is applicable together with this document. Where two requirements are in conflict, the most severe take precedence. This document does not apply to transformers covered by IEC 60076-11. This document is applicable to stationary or portable, single-phase or polyphase, air-cooled (natural or forced) independent or associated variable dry-type transformers. - variable auto-transformers; - variable separating transformers; - variable isolating transformers; - variable safety isolating transformers. The windings can be encapsulated or non-encapsulated. The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and the internal operational frequencies do not exceed 500 Hz. The rated output does not exceed: - 40 kVA for single-phase variable auto-transformers; - 200 kVA for poly-phase variable auto-transformers; - 1 kVA for single-phase variable separating transformers; - 5 kVA for poly-phase variable separating transformers; - 25 kVA for single-phase variable isolating transformers; - 40 kVA for poly-phase variable isolating transformers; - 10 kVA for single-phase variable safety isolating transformers; - 16 kVA for poly-phase variable safety isolating transformers. This document is applicable to variable transformers without limitation of the rated output subject to an ...