How to choose the right varistor for my application?

How to use Varistor

Dear All,

I do not know how to choose right vairstor for my application. Especially, I do not understand each definition of the following item for Varistor:
1. Working Voltage
2. Vairstor Voltage
3. Clamping Voltage
4. Peak Current
5. Transient Energy

Best Regards,
Le ^.^

Re: How to use Varistor

Let us look at an example:

Maximum Continous voltage:
10V rms and 14Vdc: can you see why? (RMS will hav 1.41 peak-to-peak voltage and this will be equivalent to 14Vdc)

Clamping voltage:
42V @ Ip 5A Ths will be voltage at which the varistor will be able to conduct up to 5A pulse (destructive if: see next parameter)

Transient energy:
5J over 1000us : This 5J can be absorbed by the VDR but only over 1000us.

and the last

Varistor voltage at 1mA: in this case it will be 18Vdc.

So, as you can see this element will be used to protect dc voltages of 14Vdc or RMS 10Vrms and will clamp pulses of up to 42V but for not longer than 1000us.
If you forse to work this MOV above these maximum parameters you have good chances to see and smell some smoke...

Re: How to use Varistor

Dear IanP,

Thanks for teaching me without reserve.
I understand now. it is only V=IR or P=IV=E/t. I will choose right varistor for ESD protection.
Thanks!!!!

Best Regards,
Le