Yep, any stray capacitance to ground will cause nuisance tripping of a GFI.
If you assume
0.005A (5mA / UL limits) for GFI, at 120VAC is 24K impedance, which
calculates out as
~ 0.1 uF. I tested with a MMC tappable capacitor bank, and GFI in my house
tripped at
0.09 uF. This is also reason why RV's can not use a GFI protected shore
tie, any UL listed
caps between H/N and N/G will cause nuisance tripping (microwave, AV
equipment,
HVAC). Been there, done that, and got spanked by it...
On Fri, Mar 7, 2014 at 7:17 PM, David Speck <Dave@xxxxxxxxxxxxxxxx> wrote:
> Jim,
>
> I'll concede your points.
>
> However, if you are having spikes big enough to deplete MOVs in a short
> time, the rectifier diodes won't stand a chance.
>
> It can be prudent to put a suitable fuse in series with each MOV to guard
> against short circuit failures. Of course, you have to watch the fuses,
> 'cause if they blow, then you lose the protection of the MOVs.
>
> Do any TC builders run their coils through GFI circuits? To my
> understanding, a TC is a granddaddy of a ground fault when in normal
> operation.
>
> Dave
>
>
> On 3/7/2014 6:25 PM, Jim Lux wrote:
>
>> On 3/7/14 2:02 PM, David Speck wrote:
>>
>>> Dave,
>>>
>>> I would also place suitably rated, beefy MOVs across the input and
>>> output leads of the bridge, and possibly across each individual leg of
>>> the bridge. Rearranging the wiring have caused the system to pick up RF
>>> in a new way that is blowing the bridge.
>>>
>>
>> MOVs in a system where there are spikes all the time is a recipe for
>> disaster. Each time they clamp, they die a little, and conduct a bit more
>> leakage current. I learned that on the 3 phase motor drive scenario.. Kill
>> a big fat MOV in hours.
>>
>> If you want a clamp, use a gas tube type or a semiconductor device. They
>> can clamp millions of impulses.
>>
>>
>>> I'd also place suitably rated 0.1 uF ceramic disc caps across each leg
>>> of the bridge to bypass stray RF. Electrolytic caps are too slow to
>>> protect against RF at TC frequencies.
>>>
>>
>>
>> 0.1 uF will result in some noticeable leakage at 60 Hz. It's about 27k
>> impedance, so you get about 10 mA. Probably not a big deal in this
>> application, but it's more than enough to trip a GFCI.
>>
>> Series L might be a better approach to filtering.
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
>>
>>
>>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
--
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA
Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla