Methodology Guides
Detailed calculation methodologies with standard clause references, worked equations, and professional engineering context.
Cable Sizing Methodology — Multi-Standard Approach
Complete methodology for electrical cable sizing across AS/NZS 3008, BS 7671, IEC 60364, and NEC/NFPA 70. Covers current rating, derating factors, voltage drop verification, and protective device coordination with step-by-step equations.
18 min readVoltage Drop Calculation Guide — Formulas, Methods & Limits
How to calculate voltage drop in electrical cables using AS/NZS 3008, BS 7671, IEC 60364, and NEC methods. Covers the mV/A/m method, AC impedance, power factor effects, worked examples, and allowable limits by standard.
14 min readCable Derating Factors Explained — Complete Guide
Comprehensive guide to cable derating factors for electrical installations. Covers ambient temperature, grouping/bunching, soil thermal resistivity, depth of burial, thermal insulation, and solar radiation derating across AS/NZS 3008, BS 7671, IEC 60364, and NEC.
15 min readPocket Card: Motor FLC Quick Reference — NEC Tables 430.247/248/250
Printable credit-card sized reference card with three-phase and single-phase motor full-load current tables from NEC 2023, plus 125% conductor sizing rule, overcurrent protection maximums, NEMA starter sizes, and locked rotor code letters.
3 min readPocket Card: Transformer Impedance & Fault Current Quick-Calc
Printable credit-card sized reference card with transformer fault current calculations, common kVA sizes with pre-calculated Isc at 208/240/415/480 V, worked examples, X/R ratios, asymmetry factors, and equipment fault ratings.
4 min readPocket Card: IP & NEMA Enclosure Rating Cross-Reference
Printable credit-card sized reference card with the full IP rating matrix (IEC 60529), NEMA-to-IP cross-reference table, plain-English protection meanings, common ratings quick guide, and a decision matrix for enclosure selection.
4 min readPocket Card: Cable Colour Codes — All 4 Major Standards on One Card
Printable credit-card sized reference card with cable colour codes for AS/NZS 3000, BS 7671, IEC 60446, and NEC/NFPA 70. Covers single-phase, three-phase, DC systems, historical colour changes, and medium voltage identification.
4 min readMCB Tripping Curves Pocket Card — B, C, D Curves Reference
Instant reference card for MCB tripping curves (B, C, D types). Shows magnetic & thermal trip thresholds per IEC 60898. Free printable PDF.
4 min readHow ECalPro Sizes Cables per AS/NZS 3008.1.1:2025 — Step-by-Step Methodology
Complete step-by-step methodology for cable sizing per AS/NZS 3008.1.1:2025 including current capacity from Table 3, voltage drop verification, short-circuit withstand, earth fault loop impedance, and grouping derating cascade per Clause 3.2.3.
16 min readThree-Phase Voltage Drop Formula √3·I·(Rcosφ+Xsinφ)·L — Calculator & IEC 60364 Limits
Three-phase voltage drop formula explained: √3·I·(Rcosφ+Xsinφ)·L. IEC 60364 limits: 3% lighting, 5% other. Worked examples + free calculator. No signup.
14 min readShort-Circuit Current Calculation per IEC 60909-0:2016 — How ECalPro Implements the Standard
Detailed methodology for short-circuit current calculation per IEC 60909-0:2016 covering voltage factor c, impedance correction factors KT and KG, symmetrical and asymmetrical fault analysis, sequence components, and validation against IEC TR 60909-4:2021 benchmark networks.
18 min readArc Flash Calculation Methodology per IEEE 1584-2018 — What Changed from the 2002 Edition
Comprehensive methodology for arc flash incident energy calculation per IEEE 1584-2018 covering the 5 electrode configurations, arcing current variation at 100% and 85%, working distance, enclosure parameters, and PPE category assignment per NFPA 70E Table 130.5(G).
16 min readMaximum Demand Calculation per AS/NZS 3000:2018 Clause 2.2 and Table 2.1
Complete methodology for maximum demand calculation per AS/NZS 3000:2018 covering the ADMD concept, Table 2.1 application rules, demand factors for domestic, commercial, and industrial loads, Clause 2.2.2 deviation provisions, and multi-board installation roll-up.
14 min readMotor Starting Current and Voltage Dip Calculation — IEC 60034-12 and AS/NZS 3000 Clause 3.5
Complete methodology for motor starting current estimation, voltage dip calculation, and starting method comparison per IEC 60034-12, AS/NZS 3000 Clause 3.5, and BS 7671. Covers DOL, star-delta, soft-starter, and VFD starting with worked equations.
14 min readTransformer Current, Impedance, and Fault Level Methodology per IEC 60076-1
Complete methodology for transformer full-load current calculation, percentage impedance voltage interpretation, fault level derivation, vector group selection, and inrush current estimation per IEC 60076-1, AS/NZS 60076.1, and IEEE C57.12.00.
15 min readEarth Fault Loop Impedance — BS 7671 Calculation Method
Calculate earth fault loop impedance per BS 7671. Covers Zs values, disconnection times & conductor sizing. Free step-by-step methodology guide.
14 min readCable Derating Factor Methodology — Ambient Temperature, Grouping, and Thermal Resistivity
Comprehensive methodology for applying cable derating factors across AS/NZS 3008, BS 7671, IEC 60364, and NEC standards. Covers ambient temperature correction (Ca), grouping factors (Cg), soil thermal resistivity (Cs), thermal insulation, and the thermal independence assumption behind multiplicative derating.
16 min readOvercurrent Protection Coordination Methodology — CTI, IDMT Curves, and Selectivity
Complete methodology for overcurrent protection coordination covering current transformer interface (CTI) grading margins, IEC 60255-151 IDMT curve families (SI, VI, EI), curve selection by fault current ratio, back-up protection, and MCB discrimination using energy-limiting data.
16 min read