IEC Vs NEC Hazardous Area Classification Comparison





















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Cable Sizing for High Voltage Motor

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Cable Sizing for High Voltage Motor Minimum Size of Cable required to withstand short-circuit : Minimum Cross Section Area of HV Cable = (If x √t)/k Where, Maximum Fault level at 6600 V - 457 MVA (Assumed) If = 40 kA at 6.6kV k = Material Constant = 0.094 (for aluminium cables) t = Fault withstand time in sec. = 0.25 sec (Assumed) Minimum Cross Section Area of HV Cable = (40 x √0.25)/0.094 = 212.76 mm2 Next available standard size is 240 mm2 Hence, minimum cross sectional area for HV cables is 240 sq. mm Now, we have to check three parameters : a)Able to withstand continuous current rating b)Voltage Drop (During Normal Running Condition) c)Voltage Drop (During Starting Condition) a)Able to withstand continuous current rating : Rating = 210 kW Power Factor = 0.88 Efficiency = 93% Rated current = 210 / (√3 x 6.6x 0.88 x 0.93) = 22.44 Amp Required current rating of cable, after adjusting for derating factor (Derating factor is explained at bottom) ...
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Transformer Design - IEC Vs ANSI/IEEE

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    TRANSFORMERS DESIGN PARAMETERS IEC ANSI/IEEE For transformers up to 10 MVA, values of rated power roughly follow the R-10 series [3] given in ISO 3 (1997), preferred numbers : (…100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, etc.) Reference ANSI / NEMA C57 standard for power and distribution transformers, Standard ratings for different cooling methods OA / FA 55 / 650 C, and for standard impedance. Commonly International practice is to use Sealed tank transformers up to 1600 kVA and Conservator type for larger transformers American typical common practice in Petroleum & Chemical (P&C) applications is to use sealed tank transformers up to 15-20 MVA and conservator type for larger transformers. Shall be capable of sustaining a maximum of 105% rated Volts/Hz continuously without damage Shall sustain 110% Volts/Hz at no-load and shall be able to deliver rated power at 110% of the rated secondary vol...
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