TVS problem

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Guest

TVS problem

Post by Guest »

I have a 23v max Transient Voltage suppressor. My question is....can I put a resistor on it to allow it to be used on higer voltages because these things cost 5 dollars for one and I am not going to pay that much for a higher voltage TVS.
Tech_man

Very easy question to answer to your TVS problem

Post by Tech_man »

The answer to your question is simple, YOU cannot use a resistor on a TVS because the currents drawn from the TVS are varying constantly with voltage changes. So you pretty much have to buy a higher voltage TVS. Sorry:( Here is what I mean E/R=I. Lets say the TVS is rated for a minimum voltage conduction of 12 volts at 5 amps and a MAX clamping voltage of 23 volts and will pull 18 amps at this voltage. You have 400 volts of surge, but the resistor used is only calculated for just 200 volts of surge.

E=200v-23v=177v drop to get 23v
I=18 amps
R=9.83 Ohms

Now the 400 volts:

E=400v-23v=377V
I=38.3 amps (Opps did I just see smoke and flames and here popping:P )
R=9.83 Ohms

So the conclusion to this is, its better to waste $5 on a higher voltage TVS rather than buying more because of the fried ones you keep getting.
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