To: mail11:;-at-msd26.ENET.dec-dot-com (-at-teslatech)
Subject: filter fundamentals
From: "I am the NRA." <pierson-at-msd26.ENET.dec-dot-com>
Date: Thu, 29 Feb 96 17:28:47 EST
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>>> Without a lot of thought, I fit 20 turns of 12ga solid
>>> THHN house wire on one of them before realizing that the
>>> wire is only rated at 600v.
>>I don't see how this would be a problem. There shouldn't be a large
>>voltage drop across the inductors (my brain isn't in gear so I don't
>>remember the formula for the impedence of an inductor, but you can
>>figure it out from V=IX, where X is the impedence of your inductor).
>How can the inductor do its job without dropping a lot of voltage across it?
Depends on what its job is. The drop 'across' will depend on the
frequency. If the job is to keep the hash (rf) out of the power
transformer, or out of the power feed, then the voltage AT RF may
well be small, but still need to be blocked. The voltage at power
freq (ca 60 Hz) will be smaller yet, and thus irrelavant. Ditto the
cases on a line side filter.
(in the special case of an inductor in a resonat circuit, or a
resonant configuration (lumped circuit or helical) the voltages
do go up.)
In any case of considering insulation, consider what is being insulated
from what. Ferrites are typically (always, i think) insulators
in and of themselves. Insulation from turn to turn, expecially
in primary or secondary filters would not see a LOT of voltage
normally, per turn, which is what the insulation rating on the
wire is about. (Some overrating on the insulation might save
destruction in a fault condition....)