Power systems calculations have always been a critical skill that makes a lot of difference in our careers. Are you a power system engineer?
These five calculators cover the core power system analysis skills that you need in your daily practice. Experience shows that the most basic formulas we underestimate are used more often than the complex ones.
Interestingly, for those interested in taking the PE Power exam, these calculators are helpful for your practice. Each calculator uses industry-accepted formulas per IEEE and NEC standards.
The calculators include per-unit conversion, voltage drop, short circuit fault current, transformer turns ratio, and symmetrical components. Together, they address the most heavily weighted topics in power system analysis. Therefore, they are useful for both exam preparation and real engineering decisions.
Simply enter your known values, select your preferred units, and get results instantly. The formula used is always shown with every calculation — no guesswork involved. Whether you are studying for the PE exam or solving a daily engineering problem, you will find these tools handy and helpful.
Per-Unit System Calculator
Impedance, current & voltage per-unit conversion — or change system base
Zpu=Z/Zbase | Ipu=I/Ibase | Vpu=V/VbaseZpu=Z/Zbase | Ipu=I/Ibase | Vpu=V/Vbase,LN
Base change: Zpu,new=Zpu,old×(Snew/Sold)×(Vold/Vnew)²
Voltage Drop & Wire Sizing
NEC compliant conductor sizing and voltage drop — single & three-phase
VD3φ=√3·Z·I·L | VD%=(VD/VS)×100Full Voltage Drop + Wire Sizing Calculator
This calculation is covered by a comprehensive dedicated tool — including NEC 2023 Table 310.16 ampacity, full AWG to 2000 kcmil coverage, copper vs aluminum comparison, PDF export, and auto unit conversion.
Open Voltage Drop Calculator →NEC guideline: ≤3% branch circuit | ≤5% feeder + branch combined
Short Circuit (Fault) Current
Symmetrical bolted fault current — three-phase & single-phase methods
Isc,3φ=VLL/(√3·Ztotal) | Isc,1φ=VLN/ZUses available fault MVA at source plus transformer %Z — most common for service entrance per IEEE Std 141.
Fault MVA=√3·V·Isc | Asymm. peak≈2.7×Isym (X/R=15, IEEE C37.010)
Transformer Turns Ratio
Turns ratio, voltage/current/impedance transformation — per IEEE Std C57.12.00
a=N1/N2=V1/V2=I2/I1 | Z1=a²·Z2Ideal transformer: V₁I₁=V₂I₂
Symmetrical Components
Resolve unbalanced voltages or currents into sequence components — interactive phasor diagram
V1=(Va+a·Vb+a²·Vc)/3 | a=1∠120° (ABC) | a=1∠-120° (ACB)Enter the three unbalanced phasor magnitudes and angles. Drag arrowheads on the diagram to adjust interactively.
V₀=(Va+Vb+Vc)/3 | V₁=(Va+a·Vb+a²·Vc)/3 | V₂=(Va+a²·Vb+a·Vc)/3
Unbalance%=|V₂|/|V₁|×100 | NEMA MG1-14.35 motor limit: ≤1%
Note: ACB is the utility's defined normal phase sequence, not an indicator of negative sequence operation.
