Arc Flash Incident Energy Calculator
Full implementation of the IEEE 1584-2018 model — three voltage-base equations with interpolation, arcing current variation, and enclosure size correction. Validated against the worked examples in IEEE 1584-2018 Annex D (D.1 at 4.16 kV and D.2 at 480 V) to within 0.05% on every intermediate and final value. IEEE 1584-2002 is included for legacy comparison.
↗ Also available as its own page: powerengcalc.com/arc-flash-calculator
Implements IEEE Std 1584-2018 §4.4–§4.10 (Tables 1–7, Eq. 1–25) and IEEE Std 1584-2002 §5.2–§5.5. PPE categories per NFPA 70E-2024 Table 130.5(G). Preliminary estimation only — a complete arc-flash hazard analysis must be performed by or under the direction of a licensed PE using site-specific data.
Voltage Drop Calculator
Full R+X impedance model per NEC Chapter 9 Table 9 — not the simplified 2R approximation. Copper and aluminum in steel or PVC conduit, 14 AWG – 750 kcmil. Flags NEC 215.2(A) 3% and 5% thresholds.
↗ Also available as its own page: powerengcalc.com/voltage-drop-calculator
Reference: NEC 2023 Chapter 9 Table 9 (75°C conductors). NEC 215.2(A) Informational Notes: ≤ 3% branch circuit, ≤ 5% total system (feeder + branch) recommended.
Conduit Fill Calculator
NEC 2023 Article 314.16, Chapter 9 Tables 4 & 5. Supports mixed conductor sizes and insulation types. Fill limits: 1 conductor 53% / 2 conductors 31% / 3+ conductors 40%.
↗ Also available as its own page: powerengcalc.com/conduit-fill-calculator
Reference: NEC 2023 Article 314.16(B), Chapter 9 Tables 4 & 5. Verify with AHJ for special conduit types or field-installed fittings.
Cable Tray Fill & Ampacity Derating
NEC 2023 Article 392 — cable tray fill and ampacity derating. Ladder, ventilated, and solid-bottom trays. Mixed THHN single-conductor, MC cable, and VFD/shielded cable. Ampacity per NEC 310.15(B), 75°C copper, 30°C ambient.
Reference: NEC 2023 Article 392.22 (fill), 392.80 (ampacity derating). OD values are typical manufacturer data — verify with project-specific datasheets for final design.
DC Battery Sizing Calculator
Sizes a 48 V DC battery plant: strings required at both design and operating current, installed capacity, home-run and inter-tier voltage drop, breaker frame size, and cable-protection compliance. Method developed by PEFG — not a published industry calculator.
↗ Also available as its own page: powerengcalc.com/battery-sizing-calculator
Aging factor per IEEE Std 485 practice. Breaker sizing applies a 1.25 continuous-load factor consistent with NEC 210.20(A)/215.3. Cable ampacity values are NEC Table 310.16 75 °C entries supplied by the user. This is a PEFG-developed sizing method — verify all results against battery and breaker manufacturer data and have the final design sealed by a licensed PE.
Racks per DC Plant / Capacity Calculator
Determines how many equipment racks a DC plant can support, the current per BDCBB feed, the minimum fuse/breaker size per feed, and the rack count adjusted for a utilization factor. Method developed by PEFG — not a published industry calculator.
Overcurrent device sizing must be confirmed against NEC Article 240 and the DC distribution equipment listing. This is a PEFG-developed sizing method — verify against plant and BDCBB manufacturer data.
DC Plant Sizing (AC to DC)
Converts a target DC load into the AC service load it imposes: rectifier quantity and AC draw, HVAC cooling load, auxiliary and lighting, total service amperage, panel adequacy, and generator sizing. Method developed by PEFG — not a published industry calculator.
Panel adequacy applies a 1.25 continuous-load factor consistent with NEC 215.3. Generator sizing is a first-pass kVA estimate only — final generator selection requires transient and step-load analysis with the manufacturer. This is a PEFG-developed sizing method; verify against rectifier, HVAC and generator manufacturer data and have the final design sealed by a licensed PE.
Battery DC Short-Circuit Current Calculator
Calculates the total available DC short-circuit current at a battery terminal or distribution bus fault — battery, charger and DC motor contributions summed per IEEE 946 clause 7.9 — using the cell internal-resistance method of IEEE 946 Annex B. Both the detailed Ohm's-law result and the conservative 10× one-minute-rating screening value are reported side by side, as Annex B.3 itself does.
↗ Also available as its own page: powerengcalc.com/battery-dc-short-circuit-calculator
Battery, charger and motor contributions summed per IEEE Std 946-1992 clause 7.9; internal-resistance method and Equations (B-1) and (B-2) from Annex B; transient timing per Annex D.3. Short-circuit behaviour, time constants and withstand limits per IEEE Std 1375-1998 clauses 6.4, 6.5 and 6.6. IEEE 946 Annexes B and D are informative. Cell internal resistance varies with age, state of charge and construction — confirm against battery manufacturer test data before setting interrupting ratings, and have the final design sealed by a licensed PE.
DC Arc Flash Incident Energy Calculator
Pick a method — each is built from a different named source, with different inputs, a different validity range, and a different degree of conservatism.
↗ Also available as its own page: powerengcalc.com/dc-arc-flash-calculator
Four independently-sourced methods — see the citation at the end of each calculation's derivation. This is preliminary screening, not a substitute for a site-specific study by a licensed PE, especially given that DC arc flash guidance (including NFPA 70E's own annex) is still actively being revised in the industry as of this writing.
Thermal Loading & Insulation Life Calculator
Estimates insulation life as a function of ambient temperature and per-unit loading using the Arrhenius relationship, and checks the resulting temperature against the rise limits of the governing product standard. Winding rise is scaled by the square of per-unit loading; life is scaled by the halving rule.
↗ Also available as its own page: powerengcalc.com/transformer-thermal-life-calculator
Arrhenius insulation-life relationship and the 10 °C halving rule of thumb from Siemens TechTopics No. 15. Temperature rise varying with the square of loading is stated in IEEE Std C37.91-2008 Annex D.1. Liquid-immersed rise limits (65 °C average winding, 80 °C hottest-spot, 65 °C liquid) from IEEE Std C57.12.00-2006 clause 5.11.1; ambient service conditions from clause 4. Dry-type rise limits from IEEE Std C57.12.01 Table 10. The halving rule is a general rule of thumb for electrical insulation, not a value calibrated to any specific transformer. This calculator does not implement IEEE Std C57.91 — see the scope notice above. Verify against manufacturer thermal data and have loading decisions reviewed by a licensed PE.
Motor Starting Voltage Dip Calculator
Computes the voltage dip at the motor bus and at the motor terminals when a large motor is started across-the-line or on a reduced-voltage starter, using the impedance (voltage-divider) method of IEEE 399 clause 9.6.1a. Results are checked against the critical voltage levels of IEEE 399 Table 9-1 and the accelerating-torque reduction that follows from torque varying as the square of applied voltage.
↗ Also available as its own page: powerengcalc.com/motor-starting-calculator
Impedance (voltage-divider) method and Equations (9-2) through (9-5) from IEEE Std 399-1997 clause 9.6.1; critical voltage levels from Table 9-1; study-threshold guidance from clause 9.2.1. Locked-rotor kVA/hp code letters from NEMA MG 1 §10.37.2; running voltage tolerance of ±10 % from §12.44.1(a); torque varying as the square of applied voltage from §12.44.2. This is a single-instant snapshot at the moment of inrush — it does not model generator exciter/regulator response, transformer tap control, motor slip during acceleration, or reacceleration of other running motors. IEEE 399 clause 9.4 calls for a time-domain study where those effects matter. Verify against motor and transformer manufacturer data and have the final design sealed by a licensed PE.
Professional Power Engineering Calculators — Free Online Tools
powerengcalc.com provides professional-grade electrical engineering calculators built on the actual equations from IEEE 1584-2018 and NEC 2023 — not simplified approximations.
The IEEE 1584-2018 arc flash calculator covers all five electrode configurations (VCB, VCBB, HCB, HOA, VOA), computes arcing current using the 1584-2018 regression equations, and outputs incident energy in cal/cm² with NFPA 70E-2024 PPE category determination and flash protection boundary in meters. See our articles on what each electrode configuration means and what changed between the 2002 and 2018 editions for more detail.
There's no direct conversion from system voltage to incident energy in cal/cm² — voltage is only one of several inputs the calculation depends on. Incident energy is driven by the interaction of arcing current (itself a function of both voltage and available bolted fault current), how long the protective device takes to clear the fault, the equipment's electrode configuration and gap, and the working distance to the arc. Two pieces of equipment at the same voltage can produce very different incident energy depending on those other factors — which is exactly why a calculation is necessary rather than a lookup table.
The voltage drop calculator uses full R+X impedance data from NEC Chapter 9 Table 9, covering copper and aluminum conductors in both steel and PVC conduit from 14 AWG through 750 kcmil. Results flag the NEC 215.2(A) 3% and 5% thresholds.
The conduit fill calculator applies NEC 2023 Article 314.16 (Tables 4 and 5) to determine maximum conductor fill percentage for a given conduit type and trade size, covering EMT, IMC, RMC, and PVC across the full range of standard conductor insulations.
The cable tray fill and ampacity derating calculator follows NEC 2023 Article 392, covering multiconductor cable fill limits by tray type and width along with ampacity derating for cable tray installations carrying more than the single-layer allowance.
The DC battery sizing calculator sizes standby battery strings using IEEE 485 aging-factor methodology alongside NEC 240.6 / 310.16 overcurrent and conductor ampacity requirements — built for telecom and data center DC plant design.
The racks-per-DC-plant / capacity calculator and the DC plant sizing calculator (AC-to-DC) size rectifier, HVAC cooling, service load, and generator capacity for a DC power plant, including BDCBB feed sizing and rack load distribution — a first-pass sizing estimate for telecom central offices and data center DC plants.
The battery DC short-circuit current calculator implements IEEE Std 946-1992 clause 7.9 and Annex B, summing the battery, charger and DC motor contributions to a DC bus fault. Cell internal resistance is derived from the slope of the manufacturer's discharge characteristic curve using Equation (B-1), and fault current follows from Equation (B-2). The conservative 10× one-minute-rating screening value of clause 7.9.1 is reported alongside the calculated result, and transient time constants follow Annex D.3 and IEEE Std 1375-1998 clause 6.4 — the numbers needed to set DC breaker interrupting ratings and bus withstand.
The thermal loading and insulation life calculator applies the Arrhenius relationship to estimate how ambient temperature and per-unit loading affect insulation life, scaling temperature rise by the square of loading and life by the 10 °C halving rule. Temperature limits come from IEEE C57.12.00 clause 5.11.1 for liquid-immersed transformers and IEEE C57.12.01 Table 10 for dry-type units. It is a steady-state screening tool for answering "what does another 10 °C actually cost me" — it is not an IEEE C57.91 loading study.
The motor starting voltage dip calculator uses the impedance voltage-divider method of IEEE Std 399-1997 (Brown Book) Chapter 9, carrying source, transformer, feeder and locked-rotor impedances as complex per-unit quantities. Locked-rotor kVA comes from NEMA MG 1 code letters, LRA, or a multiple of full-load amperes; results are checked against the critical voltage levels of IEEE 399 Table 9-1 and the accelerating torque that remains once torque falls with the square of voltage.
For engineering consulting, arc flash studies, forensic investigations, or expert witness services, visit pefgconsulting.com.