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devices for protection from Lightning ?

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mitaka

mitaka

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what device is appropriate to use for primary protection from lightning and overvoltages :?:
 

metal oxide varistor

There are devices that you put in parallel with each line to ground. These are called metal oxide varistor or MOV for short. They come in different voltage ratings. They only work for low frequency lines because their capacitance would affect higher frequency signals.

There are a variety of other semiconductor devices that act like zener diodes. There are also gas discharge tubes.

The usual trick is to have some inductance between them and the rest of the circuitry with further protection on the other side.

There should be application notes from the manufacturers of these devices.
The laws in different countries prohibit or allow different configurations of the protectors.

Whole books have been written on this subject.
 

The best protection gives circuit (in order from surge source to protected circuit):
- parallel surge arrester or parallel MOV (metal oxide varistor), also you can use both of them, but arrester should be closer to surge source
- series wirewound resistors or polyswitches
- TVS diode (in example 1SMB.. from ONsemiconductor)
 

I have good experience with miniature surge agsorbers (e.g.BSP301L) as the first part and then with trisils as a second part.
Trisil are very quick, but very sensitive too. They can not be used as a firts part generally although they pass overvoltage tests (10/700us, 0,2/50us)
pool_77
 

You need to use an over current protection PTC before using the gas discharge tube at the first stage to limit the current flow. So the first stage is PTC and the second stage is the gass discharge tube and after this you will need a TVS from and the rating of the TVS must be calculated very will and must be bidirectional type. Your design must take into consideration the common mode and differental mode surges.
 

Can you post some link or shematic?
 

:roll: As a system Designers point of view the protection requirement vary.
1)For Mains power protection A MOV (100 Microsecond typical response time)is suitable. standard EMI/EMC filters with
bulit in MOV are available from Epcos, Scaffner and many manufacturers.

2)For protection of telecom circuits Gas descharge devices are used.

3)if you want protect low voltage circuits:(3.3 V 5V etc TVS diodes should be used.because of their very sharp clipping times and better tolerances( picoseconds in theory) types P6KE and 1.5KE series from www.vishay.com,, www.fairchildsemi.com
4)many times a combination all types is used depending upon protection levels requird
:lol:
 

Hello.

It's very important what type of circuits will be protected.
If it's AC power lines in many cases quate enough use MOV ( varistor ).
If you wish to protect data transmission line ( RS-485, CAN or Profibus ) or signal transmission line ( 0-10 VDC, 4-20 mA ... ) usually used three stage scheme. It' like three stage Rx-circuit ( series R, parallel x ), but instead of R ( resistor ) may be used PPTC ( Poliswitch, Multifuse ) or inductor.
In the first stage x-element is GAS TUBE DISCHARGE, in yhe second MOV ( varistor ), in the third - TVS ( transient voltage suppressor the same as power avalanche diode ). If you protected data transmission line and high transmittion speed is needed second stage removed because of high capacitance of varistor.
 

could you recommend to me a good book on this subject?
 

Can I use 1.5KE18AC instead of 1.5KE18A for DC applications. I mean use a transorb of 18V to protect a voltage sensitive device against high voltage spikes in DC rail.

73,

Fernando - PU2PLL
 

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