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International StandardIEC 60038,IEC standard voltages, defines a set of standard nominalelectricity supply voltages forlow voltage andhigh voltageAC andDC systems.[1]
The standard primarily contains a set of tables, each of which define a set of standard nominal supply voltages that may be chosen from, as follows:
Standard nominal voltages that can be used for low voltage systems in the 100-1000V range are as follows:
Note that with the exception of the American split-phase case, where two voltages are given separated by a slash, these represent 4-wire cases; the first voltage corresponding to that between phase and neutral, and the second between phases. Single voltage values are for 3-wire cases and thus correspond to that between phases. In the case of American split-phase, the first value is that between ahot and the centre-tapped neutral, while the second is that between the pair ofhots. All AC voltages areRMS. Three-phase 3-wire is without neutral, while three-phase 4-wire is with neutral.
Of historical interest, it is noted that the 230/400 V three-phase option replaced the former 220/380 V and 240/415 V systems. Similarly the 380/660 system was replaced with 400/690 V. Migration from these older voltage systems was required by amendment 2 to the 1983 edition of the standard, published in 1997. Those countries with a 220/380 V systems were required to bring their voltage within +6/-10% of 230/430 V, while those with a 240/415 V system were required to bring their voltage within +10/-6% of 230/430 V, as soon as possible, and no later than the year 2003, thus achieving all systems being within ±10% of 230/430 V by that deadline.