On Mon, 27 Oct 1997, POWELL, DOUG wrote:
>
> Hello all,
>
> I have need for double insulated wire in sizes ranging from 22 - 4 AWG and
> larger for up to 300Vac mains applications. Currently we often use 600V
> rated heatshrink over 300V rated wire, labor costs are very high.
>
> I have already checked into the "BN" style wire and found that the PVC core
> insulation carries the full voltage rating of 600V and the nylon jacket is
> only for solvent and abrasion resistance, i.e. the nylon jacket is not
> voltage rated. It would be better if each layer contributed 300V for basic
> and supplementary insulation.
>
...snip
Actually, not likely. If the insulations are dissimilar and are expected
to divide the voltage across each, it usually doesn't happen. The 600V
across both ends up being transferred to across just one and if it breaks
down at 300V, you're in trouble.
Classic example of this is an air void in a high voltage cap becoming the
site of catastrophic failure.
Just food for thought when you start "dividing" up voltage breakdown.
- Robert -
