Surge Protection Calculator
Calculate the energy absorption requirements and clamping voltage for surge protection devices (SPDs).
8/20 microsecond is standard test waveform
Clamping V / System V peak; typical MOV = 2-3x
Clamping Voltage
813 V
Clamping Voltage vs Surge Duration
Formula
## Surge Protection Device Sizing SPDs must absorb surge energy while limiting voltage to a safe clamping level that protects downstream equipment. ### Formulas **V_clamp = V_peak x Clamping Ratio** **Energy = V_clamp x I_surge x Duration** The standard test waveform for SPDs is 8/20 microseconds (8 us rise, 20 us to half-value). ### SPD Categories (IEC 61643) - Type 1: Lightning current (10/350 us), installed at service entrance - Type 2: Surge current (8/20 us), at distribution panel - Type 3: Combination wave, at point of use
Exemplo Resolvido
230 V system, 10 kA surge (8/20 us), MOV clamping ratio 2.5x.
- 01System peak: 230 x sqrt(2) = 325 V
- 02Clamping voltage: 325 x 2.5 = 813 V
- 03Energy: 813 x 10,000 x 20e-6 = 162.6 J
- 04Peak power: 813 x 10 = 8,130 kW
Perguntas Frequentes
What is an 8/20 microsecond waveform?
A standard test surge that rises to peak in 8 microseconds and decays to half-value in 20 microseconds. It simulates induced lightning surges.
How do I choose between MOV and TVS?
MOVs handle high energy and are used in power systems. TVS diodes have faster response and lower clamping, ideal for sensitive electronics.
How many surges can an SPD handle?
MOV-based SPDs degrade with each surge. Rating should include expected surge count over the device lifetime, with replacement indicators.
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