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Re: [APD] Aromat Ballasts Arrived
Actually not current per se, but an imbalance in the flow in Hot and Neutral. Since Hot and Neutral are 180 degrees out of phase with each other, if a sensor coil is put around them, no current will flow in the coil -- the hot and neutral, being equal energy, cancel out the field. But if imbalanced, current is induced in the sensor coil.
The Neutral Ground fault requires an additional energized coil to induce current in the hot and neutral before the sensor coil. If there's no leak, there's no flow induced in the Hot and Neutral since both are inside the same energized coil.
Try here:
http://www.codecheck.com/gfci_principal.htm
sh
----- Original Message ----
From: Jerry Baker <jerry at bakerweb_biz>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Sunday, February 05, 2006 11:39:04 AM
Subject: Re: [APD] Aromat Ballasts Arrived
S. Hieber wrote:
> Almost anything you connect wouldn't mind. You'd still get the same 110-120V AC. Maybe a problem for device running balanced circuit or with an internal floating ground but with a grounded chassis (some PA amps and high priced audio amps are like this) -- you'd get an annoying hum loop with the hum showing up in the audio circuit. Your're prob is diff, you have a chassis vibration.
>
> There are some safety issues re ground-neutral crosses, which is why UL approved GFCI devices, besides testing for Hot-to-ground faults, have to include a second internal circuit to test for Neutral-to-ground faults. They have an energized coil around Hot and Neutral at all times. Neutral is grounded at the main box, so if there is a neutral to ground leak downstream form the GFCI, that will make a closed circuit through the neutral and ground wires from the leak point back to the main box, and the current flow in the neutral wire won't be the same as the Hot wire, so the GFCI will trip on the imbalance inthe hot and Neutral wirest. Kind of ingenious, in way.
If I have the following:
GFCI
----------------
| |
| |
| hot -|-------hot
| |
| neutral -|-------ground
| |
| ground -|-------neutral
| |
| |
----------------
How will the GFCI know that current is not flowing on the neutral wire?
As far as it can see, current will be exiting the unit at the neutral
connection point. If it relies on induction to detect a load imbalance
between hot and neutral, in the case above won't it look like everything
is fine to the GFCI? I mean all it will see is current flowing in the
hot port and out of the neutral port ... everything looks good.
--
Jerry Baker
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