Calculators

Ohm's Law & Power

Voltage U (V)Current I (A)Resistance R (Ω)Power P (W)

U 230.00 V · I 10.00 A · R 23.00 Ω · P 2300 W

I = U ÷ R = 230 ÷ 23 = 10 A

P = U × I = 230 × 10 = 2300 W

Cable Size (T&E, Method C)

Load (W)Device In (A)Length (m)Ca×Cg×CiCircuit

Ib = 30.4 A → 4 mm² (It 37 A, VD 6.70 V)

Ib = P ÷ U = 7000 ÷ 230 = 30.435 A (single phase, power factor 1)

Load check: Ib 30.435 A ≤ In 32 A

Required It = In ÷ (Ca × Cg × Ci) = 32 ÷ 1 = 32.000 A

VD limit = U × 5 ÷ 100 = 230 × 5 ÷ 100 = 11.50 V

Table 4D5, Method C: 4 mm² → It = 37 A; mV/A/m = 11

Rating check: 37 A ≥ 32.000 A

VD = (mV/A/m × Ib × L) ÷ 1000 = (11 × 30.435 × 20) ÷ 1000 = 6.70 V

VD check: 6.70 V ≤ 11.50 V

Selected the smallest listed size meeting both checks; displayed intermediate values are rounded.

Voltage Drop

mV/A/mIb (A)Length (m)Circuit

VD = 9.00 V (3.9%) — limit 11.5 V ✓ OK

VD = (mV/A/m × Ib × L) ÷ 1000 = (18 × 20 × 25) ÷ 1000 = 9.00 V

VD % = VD ÷ U × 100 = 9.00 ÷ 230 × 100 = 3.91%

Limit = U × 5 ÷ 100 = 230 × 5 ÷ 100 = 11.50 V

Check: 9.00 V ≤ 11.50 V

Max Zs Check (Table 41.3)

MCB typeRatingZe (Ω)R1+R2 (Ω)

Zs = 0.85 Ω · Table max 1.37 Ω · 80% measured max 1.1 Ω ✓ Pass
PFC ≈ 271 A

Zs = Ze + (R1 + R2) = 0.35 + 0.5 = 0.85 Ω

Table 41.3 lookup: type B, 32 A → 1.37 Ω

Measured maximum = table value × 0.8 = 1.37 × 0.8 = 1.096 Ω → 1.10 Ω (rounded)

Check: 0.85 Ω ≤ 1.10 Ω

PFC ≈ U₀ ÷ Zs = 230 ÷ 0.85 = 271 A

Ring Final R1+R2

r1 end-to-end (Ω)r2 end-to-end (Ω)

Expected R1+R2 = 0.335 Ω

R1 + R2 = (r1 + r2) ÷ 4 = (0.5 + 0.84) ÷ 4 = 1.340 ÷ 4 = 0.335 Ω

Adiabatic Equation (543.1.3)

Fault current I (A)Disconnection t (s)k (115 PVC Cu)

Minimum CPC S = 2.75 mm²

S = √(I² × t) ÷ k = √(1000² × 0.1) ÷ 115

I² × t = 1000² × 0.1 = 100000.000 A²s

S = √(100000.000) ÷ 115 = 316.228 ÷ 115 = 2.75 mm²