We buy Ohmite glass-coated/vitreous resistors for glitch service. They
are not as tough as high-energy discharge type resistors, but they cost
Much less $$. A 10-ohm, 10Wer will discharge a 3kV SB-220, TL-922 ps
without damage. We used to use cheaper resistors - but they arced
between turns, blew apart, and threw schrapnel about during a glitch. My
guess is that glass-coating improves the insulating ability from turn to
turn during a major fault. For more than 3kV, two or more such resistors
in series will do the job. For a higher amount of joules [C >30uF],
additional units are needed. // If you need some of these resistors, we
sell them for $1.50 each. To order, send adr, we send parts, pay from
invoice. Shipping is $1.00. // Also, mfg V-ratings on power resistors
are usually the case to ground V-rating, not the end-to-end V-rating for
glitch duty. The only test for such a resistor is the big screwdriver
short to ground test -- i.e., if there is no subsequent physical damage,
the resistor is up to the job. If one finds damage, go with additional
units in series.
cheerz, Pete.
>Has anyone had any experience using Vishay Type RH metal-cased wire-wound
>resistors (for example Mouser p. 205) as glitch resistors? There is no
>voltage rating given, and I'm skeptical about flashover between the
>windings and the metal case at 2500V and up. What about the Vishay HL
>silicone wirewounds ( see Mouser p. 204)? They seem like a much more
>conventional choice. Price is right for both, as is range of values
>available.
>
>73, Pete N4ZR
>Sometimes a tower is just a tower
>
>
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
|