Re: [TCML] Black Plastic

[David Sharpe <sparktron01@xxxxxxxxx>]

Generally speaking a megger would give indications if material is
lossy (bulk resistance)
with HV.  Need at least a 1kV unit, 5kV would be better, or
alternatively a 50kV hipot
test set would be even better, if current exceeds a programmed amount
(usually 1-10mA)
unit is tripped off line and highest recorded kV at puncture is stored
either digitally or with
a sample-hold amplifier in the analog world.  A dielectric absorption
test set could also be
used to determine if the material is suitable as a high voltage insulator.

Usually though, any plastic that is black has some level of carbon
black in it as a colorant;
which may eventually track and cause long term failure of the
material.  There are many
suitable materials available (our company uses a lot of GPO3
electrical grade composite
sheet), that uses no carbon black at all, avoiding this potential (no
pun) issue.

Regards
Dave Sharpe

On Fri, Dec 9, 2011 at 7:04 PM, Mark <the_iconoclast@xxxxxxxxxxxxxx> wrote:
> Hi, just something I've been wondering, would a megger be suitable for this purpose?
> --
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
>
> David Rieben <drieben@xxxxxxx> wrote:
>
> Hi Jay,
>
> As with any black plastic, you would need to determine it's conductance characteristics, as some use carbon as the coloring agent (bad). However, not all dark colored plastics are conductive. The best way to check for this is to bring the leads of a HV source (like an NST) to a piece of it and see it there are any notable sparks or excessive corona hiss to it's surface. If not, then it will likely work fine for your intended purpose.
>
> David Rieben
>
> On Dec 9, 2011, at 7:57 AM, jhowson4@xxxxxxxxxxx wrote:
>
>> Hello everyone,
>>
>>
>> I acquired a 1" OD length of black plastic from the machine shop here at college, I have no idea what it is. Its very hard, non translucent at its edges, not flexible. What is everyones opinion on it becoming a propeller gap spindle?
>>
>>
>> Thanks,
>> John "Jay" Howson IV
>>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla