[TowerTalk] Power line filter question

Jim Lux jimlux at earthlink.net
Wed May 21 06:55:00 EDT 2014

On 5/20/14, 10:46 PM, Jim Brown wrote:
> On 5/20/2014 10:02 PM, Grant Saviers wrote:
>> So why are x uH's of green wire inductance ok in the three wire case
>> and not for a single green wire (engineering pls,  not UL regs)?
> First, if all three conductors go through the choke, a fault on the
> circuit will blow a breaker faster.

I don't think that the small inductance from a choke on the electrical 
safety ground will change how fast the circuit breaker blows: what blows 
the breaker is line frequency.

I suspect the "rules" reason for not having anything in the greenwire is 
that you don't want a "component" in series that might fail,leaving the 
bonding open. I can imagine a "design to cost" filter putting a little 
teeny tiny RFC on a pc board in series that will act as a 20 amp fuse. 
Easier if they just make a rule "wire or chassis, no components".

So that said, running the green wire (by itself) through a choke like 
we're talking here (half a dozen turns through a ferrite core) probably 
is safe.

  Second, at RF, the capacitance
> between conductors tends to put the conductors in parallel.
> 73, Jim K9YC
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