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Two Transzorb in series

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fjpompeo

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Hi, my question is if I use two 8V2 x 1500W transzorb in series I will give 16V protection like zener does?
 

A transzorb is a special zener diode (or two in anti-series for bipolar transzorbs) optimized for absorbing transient energy. Yes, if you connect two in series you will have a 16,4V transzorb, and will do its clamping job better than a 16,4V zener because a simple zener diode could be damaged by energies that are Ok for transzorbs of similar physical size.
I am assuming you plan to connect two unipolar transzorbs in additive series (one's cathode to the other's anode), or else you are referring to bipolar transzorbs.
 
Very thank you for your explanatins lw1ecp, I'll use two of this 1.5KE8V2 in series to protect my rig from voltages above 16V due to a fail in the power transistors of my linear power supply. It'll work and connect same way like a SCR crowbar but without RF undesirable activations, I hope.

73,

Fernando - PU2PLL - BRAZIL
 

if I use two 8V2 x 1500W transzorb in series I will give 16V protection like zener does?
Click to expand...
Yes
It'll work and connect same way like a SCR crowbar but without RF undesirable activations, I hope.
Click to expand...
Not actually. A transzorb diode (the same with any standard zener diode) has a smooth characteristic and will allow a considerable overvoltage until drawing high currents. It depends very much on the overvoltage margin of the connected devices, if it provides real protection. A SCR crowbar can be usually designed to survive it's activation and e.g. blow a fuse. It's much more difficult with the high power dissipation of a transzorb diode. I also fear, that a transzorb can't exactly be guaranteed to fail short circuit in case of massive overload.

SCR RF activation is mainly a case of unsuitable design, I think.
 
I 95% agree with FvM. A transzorb characteristic is more abrupt than a varistor's. But anyway a crowbar is a better protection. The transzorb will clamp at 17 or 18 or 20V or even higher. according to the transient energy and the impedance where it comes from. If all you have is spikes with a length of, say, a few tens microseconds, a transzorb could be ok if you place a suitable inductance in series with the supply. But if there is a danger of connecting two 12V batteries in series to start the vehicle, or a short circuited pass transistor... a crowbar plus fuse is absolutely the way to go!. Does it trip with RF fields?. Try placing a 0.1uF between gate and cathode of the SCR, leads as short as possible.
Boa sorte!
 
that should be true
 
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