This 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 V a.c;- the rated frequency of the output is within the range 40 ¿¿ 100 Hz.