[Top] [All Lists]

[AMPS] construction of parasitics

To: <>
Subject: [AMPS] construction of parasitics
From: (2)
Date: Sun, 22 Jul 2001 08:50:22 -0700
>At 04:25 PM 7/21/2001 -0700, 2 wrote:
>> >Why not the ceramic (cement) type Rich ?  Reliability ? Shrapnel if an
>> >event occurs ?
>> >
>> >Tnx....Phil
>> >
>>/\  To be successful, a glitch resistor must not break down internally
>>during a major fault.  If it does,  a metal-vapour arc takes place -
>>which limits the V-drop across the resistor to c. 20v instead of the
>>needed several kV.  Thus, the desired ability to limit current to a
>>finite value is lost.  Shrapnel and internal breakdown are problems with
>>ceramic-type resistors.  To find out if a glitch resistor is up to the
>>task at hand,  (Note:  the meters and their shunts should be protected
>>with suitable glitch-diodes). short the anode supply to ground with a
>>large plastic handle screwdriver.  If there is a loud noise, the circuit
>>breaker opens, there is no sign of damage, and the ohms are unchanged,
>>the glitch resistor did its job.
>So,  under fault conditions the ceramic ("cement") resistors are known to 
>be prone to arcing/explosion/etc whereas the glass coated resistors are not 
>? (or are less prone ?)

/\   ceramic power resistors have the element inside a thick ceramic 
case.  If the resistance element vapourizes, the case can fragment and 
fly apart - much like a bomb casing..  With a glass coated / vitreous 
enamel resistor, the element is on the outside.  If the element 
vapourizes, bits of the coating fly away but the body remains intact.

cheers, Phil
>>cheers, Phil.
>> >
>> >
>> >>-  R. L. Measures, 805.386.3734,AG6K,
>> >>end
>> >>
>> >>
>> >>--
>> >>FAQ on WWW:     
>> >>Submissions:    
>> >>Administrative requests:
>> >>Problems:       
>> >
>> >
>> >
>>-  R. L. Measures, 805.386.3734,AG6K,
>>FAQ on WWW:     
>>Administrative requests:
>FAQ on WWW:     
>Administrative requests:

-  R. L. Measures, 805.386.3734,AG6K,  

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>