Safety / Protection Formulas
Safety and protection formulas size fuses, isolation barriers, and clearance distances that keep equipment and people safe. These calculators help you meet protection requirements and survive fault conditions. They are essential wherever mains or high energy is involved.
Safety / Protection Formula Calculators
- Fuse I²t Rating I²t = I² × t Current 2 mA, Time 100 µs → I²t Value = 4 × 10⁻¹⁰ A²s
- Touch Voltage / Body Current V = I × R_body Body Resistance 1 Ω, Body Current 100 µA → Touch Voltage = 100 µV
- Hi-Pot Test Voltage V_test = 2 × V_working + 1000 Working Voltage 0.726 V → Test Voltage = 1.001 kV
- MOV Surge Energy E = 0.5 × C × (V_clamp² − V_supply²) Effective Capacitance 1 µF, Clamping Voltage 3.3 V, Supply Voltage 1.55 V → Surge Energy = 4.244 µJ
- GFCI Leakage Current I = V / R_path Voltage 0.33 V, Fault Path Resistance 1 Ω → Leakage Current = 0.33 A
- Circuit Breaker Fault Power P_fault = V × I_fault System Voltage 0.33 V, Fault Current 2 mA → Fault Power = 0.66 mW
- Capacitor Safe-Discharge Time t = −R · C · ln(Vsafe / V0) Bleeder Resistor 100 Ω, Capacitance 100 nF, Safe Voltage 0.33 V, Initial Voltage 0.726 V → Discharge Time = 7.885 µs
Worked result for every Safety / Protection formula
| Formula | Expression | Worked result |
|---|---|---|
| Fuse I²t Rating | I²t = I² × t | Current 2 mA, Time 100 µs → I²t Value = 4 × 10⁻¹⁰ A²s |
| Touch Voltage / Body Current | V = I × R_body | Body Resistance 1 Ω, Body Current 100 µA → Touch Voltage = 100 µV |
| Hi-Pot Test Voltage | V_test = 2 × V_working + 1000 | Working Voltage 0.726 V → Test Voltage = 1.001 kV |
| MOV Surge Energy | E = 0.5 × C × (V_clamp² − V_supply²) | Effective Capacitance 1 µF, Clamping Voltage 3.3 V, Supply Voltage 1.55 V → Surge Energy = 4.244 µJ |
| GFCI Leakage Current | I = V / R_path | Voltage 0.33 V, Fault Path Resistance 1 Ω → Leakage Current = 0.33 A |
| Circuit Breaker Fault Power | P_fault = V × I_fault | System Voltage 0.33 V, Fault Current 2 mA → Fault Power = 0.66 mW |
| Capacitor Safe-Discharge Time | t = −R · C · ln(Vsafe / V0) | Bleeder Resistor 100 Ω, Capacitance 100 nF, Safe Voltage 0.33 V, Initial Voltage 0.726 V → Discharge Time = 7.885 µs |
Variables used across Safety / Protection formulas
- I²t — Thermal energy measure (A²·s)
- I — Fault current (A)
- t — Duration of the fault (s)
- V — Touch voltage (V)
- R — Human body resistance (Ω)
- V_test — Required hipot test voltage (V)
- V_working — Maximum normal operating voltage (V)
- E — Energy absorbed by the MOV (J)
- C — Effective circuit capacitance during the surge (F)
- V_clamp — MOV clamping voltage (V)
- V_supply — Normal supply voltage (V)
- P — Instantaneous fault power (W)
- Vsafe — Target safe voltage (V)
- V0 — Initial charged voltage (V)
Questions people ask about Safety / Protection
- I2t fuse rating — Fuse I²t Rating
- Fuse i2t rating calculator — Fuse I²t Rating
- Mov surge energy — MOV Surge Energy
- Gfci leakage to ground — GFCI Leakage Current
Related Formula Categories
Browse the full formulas index for all 32 categories.