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SMPS grounding

by likephysics
Tags: grounding, smps
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berkeman
#19
Jun24-14, 04:31 PM
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Interesting. I hadn't heard of Noisless Earth before.

I ran into PE on some European customers' devices that I helped debug a while back (EMC issues).
jim hardy
#20
Jun24-14, 07:44 PM
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Quote Quote by berkeman View Post
Interesting. I hadn't heard of Noisless Earth before.

I ran into PE on some European customers' devices that I helped debug a while back (EMC issues).
PE is new to me too, and pleasantly so.
I do like and encourage use of "earth" for earth ground and "common" for powr supply return as opposed to "ground" . You've both heard me beat that drum around here plenty.
I'm glad to see "Protective Earth" used because it leads the mind directly to what is the purpose of the connection.

IMHO, stateside EE curricula need a one hour course on the IEEE Green Book . It is embarrassing how many graduate EE's don't understand the basics.

old jim
likephysics
#21
Jun25-14, 12:27 AM
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Quote Quote by berkeman View Post
A variac is not isolated.

Why are you wanting to cheat the power cord ground?
I don't want to cheat the power cord ground. It was a mistake by the tech.
I was just curious why there was 100Vrms between PS Neutral and wall socket Earth ground.
The 100Vrms did not make sense, until I figured out it was because of the Y cap.

Do you have links to schematics of Variac vs Isolation transformer?
jim hardy
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Jun25-14, 06:35 AM
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Quote Quote by berkeman View Post
So with nothing plugged into the wall socket, you get about 2Vrms from Neutral to Ground (sounds reasonable). But when you plug your 2-prong power supply cord into the outlet, that voltage chages to 100Vrms?

Berkeman
Finally i see what you've been saying all along


Upon re-read of thread

Does that not sound like an open "ground" connection in the wall socket?
An unterminated ground will float up to potential of the PE terminal, somwhere between L and N.
When he attempts to measure at the outlet with nothing plugged in, because of the open "ground" he's effectively only connected one voltmeter lead so the meter obediently reports almost no voltage..

That outlet checker you pictured is only 5 bucks at my local Wal-Mart. No household should be without at least one.

I'd wager somebody didn't connect the "ground" wire immediately behind his receptacle.
If the receptacles in his house are "daisy chained, several of them may be open.


Likephysics:
A low impedance meter is better for electrical work. I use the $10 analog type.



You ought to find out whether that receptacle is connected properly. Can you shut off the breaker and check for continuity between N and Ground?

They both should be earthed someplace.
http://www.hyvac.com/tech_support/el..._worldwide.pdf fig 6 page 2
jim hardy
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Jun25-14, 06:38 AM
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Quote Quote by likephysics View Post
I don't want to cheat the power cord ground. It was a mistake by the tech.
I was just curious why there was 100Vrms between PS Neutral and wall socket Earth ground.
The 100Vrms did not make sense, until I figured out it was because of the Y cap.

Do you have links to schematics of Variac vs Isolation transformer?
http://instrumentation-central.com/s...s/3PN1010B.pdf


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