This Interim Standard applies to single-phase or polyphase, air-cooled (natural or forced) portable inverters having a rated supply voltage not exceeding 60 V ripple-free d.c. and an alternating current (a.c.) output where the rated output does not exceed 3 kVA; the rated output voltage is within the range 50 - 500 volt a.c; and the rated frequency of the output is within the range 40 - 100 Hz. It is applicable to isolated inverters, equipotentialy bonded inverters and RCD protected inverters for household and similar use, use on construction sites, or providing an independent supply to electrical installations in buildings, vehicles, caravans, boats and the like. Inverters may be fitted with terminals for the connection of d.c. supply or a external flexible cord fitted with battery clips or an automobile cigarette lighter plug or other d.c. plug.