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Home > Archive > Electrical code Compliance > July 2005 > Half wave rectifier, metal enclosure, and grounding
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Half wave rectifier, metal enclosure, and grounding
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| Steve Manley 2005-07-05, 4:25 am |
| For a design requirement, my instrument is powered by a ELV 24VAC
two-wire transformer. This is then halfwave rectified and stepped down
to a 5 and 12V source. Earth ground is available.
What I am interested in is what would be the best practice for
grounding? The instrument is in a metal enclosure. From an emissions
standpoint, would it better to float the metal chassis completely, tie
it to earth ground, or tie it to system ground?
I've only dealt with approvals for DC circuits to date, so this is
uncharted territory.
Thanks for any advice.
Steve
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| me@home.com 2005-07-05, 11:25 pm |
| With a metal chasis, it would be appropriate to ground it with the AC
circuit grounding conductor. Emmissions have little to do with it,
metal chasis and AC power it is a safety issue. As long as it is a
clean ground with little high frequency noise, it would also provide
the most sink for any external interferance.
On 4 Jul 2005 21:43:12 -0700, "Steve Manley" <steve.manley@gmail.com>
wrote:
quote:
>For a design requirement, my instrument is powered by a ELV 24VAC
>two-wire transformer. This is then halfwave rectified and stepped down
>to a 5 and 12V source. Earth ground is available.
>
>What I am interested in is what would be the best practice for
>grounding? The instrument is in a metal enclosure. From an emissions
>standpoint, would it better to float the metal chassis completely, tie
>it to earth ground, or tie it to system ground?
>
>I've only dealt with approvals for DC circuits to date, so this is
>uncharted territory.
>
>Thanks for any advice.
>
>Steve
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| Steve Manley 2005-07-06, 4:25 am |
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quote:
> With a metal chasis, it would be appropriate to ground it with the AC
> circuit grounding conductor. Emmissions have little to do with it,
> metal chasis and AC power it is a safety issue. As long as it is a
> clean ground with little high frequency noise, it would also provide
> the most sink for any external interferance.
I am more interested from the perspective of containing any potential
radiated emissions from the device, but I do see your point. Note that
this is a 24VAC ELV powered device, not 120VAC line powered where that
would be an immediate requirement.
Steve
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