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These five calculators cover the core power system analysis skills tested on the PE Power exam. They are also essential tools for practicing power engineers in the field. Each calculator uses industry-accepted formulas referenced to 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 instant results. 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, these tools are built for you.

Per-Unit System Calculator

Impedance, current & voltage per-unit conversion — or change system base

Zpu=Z/Zbase  |  Ipu=I/Ibase  |  Vpu=V/Vbase
Quantity:
Mode:

Enter the per-unit value on the old base. Returns Zpu on the new base.

Reset fields
Result
—pu
Zbase
—Ω
Ibase
—A
Vbase,LN
—kV
Sbase
—MVA
Formula Reference — IEEE Std 1110 / Glover-Sarma-Overbye Zbase=V²LL/S3φ [Ω]  |  Ibase=S3φ/(√3·VLL) [A]  |  Vbase,LN=Vbase,LL/√3
Zpu=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 2023-compliant conductor sizing and voltage drop — single & three-phase

VD3φ=√3·Z·I·L  |  VD%=(VD/VS)×100

Full 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 2023 Table 310.16 NEC Ch. 9 Table 8 75°C & 90°C ampacity Cu vs Al comparison 14 AWG – 2000 kcmil PDF export Single & three-phase
Formula Reference — NEC 210.19(A) / IEEE Std 141 3φ: VD=√3·Z·I·L  |  1φ: VD=2·Z·I·L  |  VD%=(VD/VS)×100
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/Z
Method:

Uses available fault MVA at source plus transformer %Z — most common for service entrance per IEEE Std 141.

Per-unit method using system base and total per-unit impedance — preferred for multi-machine studies per IEEE Std 141.

Enter system voltage and total circuit impedance directly — suitable for simple radial systems.

Answer unit:
Reset fields
Symmetrical Fault Current (Isc)
—kA
Fault MVA
—MVA
Interrupting Duty
—
Asymm. Peak (×2.7)
—kA
Available Fault Energy
—
Formula Reference — IEEE Std 141 / C37.010 / ANSI 3φ: Isc=VLL/(√3·Z)  |  1φ L-G: Isc=VLN/Z
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 — IEEE Std C57.12.00

a=N1/N2=V1/V2=I2/I1  |  Z1=a²·Z2
Solve for:
Solving…
Solving…
Solving…
Solving…
Solving…
Reset fields
Result
—
Turns Ratio (a)
—: 1
V1 / V2
—
Z1=a²·Z2
—Ω
I2/I1
—
Formula Reference — IEEE Std C57.12.00 a=N₁/N₂=V₁/V₂=I₂/I₁  |  Zprimary=a²×Zsecondary
Ideal 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)
Quantity:
Direction:
Phase rotation:

Enter the three unbalanced phasor magnitudes and angles. Drag arrowheads on the diagram to adjust interactively.

Enter sequence component magnitudes and angles. Returns reconstructed phase phasors. Drag arrowheads on the diagram to adjust interactively.

Reset fields
Sequence Components
Zero |V0|
—V
∠ Zero seq.
—°
Positive |V1|
—V
∠ Positive seq.
—°
Negative |V2|
—V
∠ Negative seq.
—°
Voltage Unbalance
—%
NEMA MG1 (≤1%)
—
Interactive Phasor Diagram — drag arrowheads to adjust
Drag arrowheads to adjust. Rotation toggle auto-updates.
Formula Reference — Fortescue / IEEE Std 141 / NEMA MG1-14.35 ABC system: a=1∠120°  |  ACB system: a=1∠-120° (utility-defined normal sequence)
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.
See more resources FE & PE Electrical Exam Prep · Refer to IEEE Std 141, C57.12.00, C37.010 & NEC and applicable standards for more information based on your special needs.