ELECTRICAL ENGINEERING TOOLKIT

Electrical Calculations &
Component Selection

Calculate electrical parameters, review formulas, and get preliminary component selection guidance — all in your browser.

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Motor feeder design →

From motor inputs to protection, control and a complete BOM.

S7-1200 selection →

CPU, signal-module and communication-module configurations.

Control cabinet BOM →

Combine equipment, I/O and 24 V control loads.

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Start with a common electrical problem and review the result and its calculation basis.

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Ohm's Law

Find voltage, current or resistance from the other two values.

U = I × R

Three-Phase Current

Estimate balanced three-phase operating current from line voltage and power.

I = P / (√3 × U × cosφ × η)

Motor Rated Current

Estimate three-phase motor rated current from shaft power, line voltage, power factor and efficiency.

I = P / (√3 × U × cosφ × η)

Cable Voltage Drop

Estimate steady-state single-phase or three-phase cable voltage drop and percentage.

ΔU ≈ k × I × L × (R′ × cosφ + X′ × sinφ)

Circuit Breaker Selection

Screen reference ratings by load type, starting method and operating current.

Iᴮ ≤ Iₙ ≤ Iᴢ · I_screen = Iᴮ × k

4–20 mA / PLC Scaling

Scale engineering values bidirectionally with 4–20 mA, 0–10 V or PLC raw counts.

y = yₘᵢₙ + (x − xₘᵢₙ) / (xₘₐₓ − xₘᵢₙ) × (yₘₐₓ − yₘᵢₙ)

AC / RLC Impedance

Calculate series RLC impedance, phase angle, power factor and resonant frequency.

Z = R + j(2πfL − 1/(2πfC))

Power Factor Correction

Estimate compensation for an inductive load and single-phase, star or delta capacitor values.

Qc = P × (tanφ₁ − tanφ₂)

Transformer

Convert ideal winding voltage and turns, and single-phase or balanced three-phase apparent power and current.

V₁/V₂ = N₁/N₂ · S = k × V × I

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