>>2, 10-ohm, 10Wers in series would be enough for glitch protection,
>In the Europe the "best buy" are the 14W Welwyn series, as shown in
The critical thing for a WW R in glitch service is V-gradient. 10w, 14w
and 25w units are c. 50mm long. Thus they have similar glitch protection
ability. However, glass-coating appears to be superior to molded
[ceramic] in glitch service.
>10-ohm resistors of this type are very comfortable at <1A intermittent
>service - but they do run hot! Two or three in series make a nice glitch
>resistor for amps of the 1-1.5kW class.
>These resistors have a nominal voltage rating of 750V, but that's the
>steady-state voltage limit for the higher-resistance values. In practice
>the 10-ohm types will withstand their share of 3-3.5kV in a "crowbar"
>glitch test, for as long as it takes to turn the power supply off.
The number of Joules being discharged is another factor.
>> but a huskier, 3A diode would still be needed.
>This diode only functions during a glitch - in other words, any severe
>current surge (and let's not ask why :-) The maximum possible surge
>current is limited by the glitch resistor, but it's still about 10x the
>normal current rating of a 3A diode, so we're relying on the surge
>current rating of the diode.
Yes, a 200A-pk rating is more desireable for glitch service than a 50A-pk
rating. A glitch diode or a glitch resistor is too big if it wont fit in
>What makes me slightly uneasy is that the surge current rating comes
>with a specified time limit. If the surge is larger and/or longer, the
>diode will fail completely. And then we can only hope that diode will
>fail short-circuit... which it usually will, but obviously this isn't a
>property that the manufacturer guarantees.
I have seen 0.5A diodes disintegrate. When in doubt, spend the extra 10
cents for the next larger size. Glitch diodes are like seat belts in
automobiles -- cheaper is not good.
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,