What is de maximun amount of Voltage for a TVS diode with IEC 61000-4-5 Standart?

Power Circuit Protection
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1

Hello.

I am so confused, I am desiging a PLC and I need to mantened protected the input of voltage regulator that support 60 V at the IN pin. But I dont understand, How the TVS diode in parallel with the source can support the ammount of 2 kV of Surge Standard (iec 61000-4-5) for the open circuit waveform, if the Vcl of the TVS diode is 65 V.

Thanks.

2

Hello, Vladimir. Welcome to TechForum.

The clamping voltage of a TVS diode is the voltage it will clamp to, not necessarily the voltage it can withstand. If the clamping voltage is listed as 65Vcl, that means voltage across the diode will not exceed 65V unless the part is damaged. A 2kV pulse will be clamped at 65V across the diode and its energy will be absorbed by the diode, up to the maximum wattage rating given in Power - Peak Pulse. So a 2kV pulse with 1kW of total peak energy in it will be clamped to 65V, the rest of its energy converted into heat, and will be absorbed and dissipated provided the TVS diode is rated for 1kW peak pulse or higher.

3

Yes, I understand this, but whats happend with the 2 kV? for example in this image.

Screenshot 2023-03-30 101513
Screenshot 2023-03-30 101513732×403 8.52 KB

how the source is 2 kV and the tvs is 33 (Vcl) if they are in parallel? i dont understand.

Thanks for your answer.

4

It is dissipated by the internal impedance of the signal source, which is defined by the difference between the open-circuit and short circuit waveforms specified by the IEC standard.

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5

What you try to say is that the Short Circuit Waveform is consequence of make V=I*Z in the impedance of source? where V is the Open Circuit Waveform? So if I am testing the system i only have to apply the Open circuit waveform with the source impedance to make the Short Circuit Waveform?

Sorry I am trying to make this effect in the ltspice.

6

That is correct.

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7

I created the Short Circuit Waveform in a txt file for use like a PWL File source, is that correct? I only have to simulate this? I am consfused.

Thanks.

8

No. Create the voltage waveform in simulation and attach an impedance to it, so that when you simulate a short circuit across that assembly, the simulated current through the short circuit matches the short circuit waveform from the standard.

As a simple approximation, the impedance can be modeled as a 2 ohm resistor.