Does this power supply have isolated output?

[treez]

Does this power supply have an isolated output?......i know it has a two pin, European plug.....

KERT KAT5VD
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[tpetar]

How you mean isolated output? I think this psu probably have transformer inside if you think on that.

 

[treez]

thanks, but even then sometimes they connect the neutral to the output common so that the output common is earthed. (remember that neutral is connected to earth in the vicinity of the building or installation)

 

[tpetar]

Neutral is connect with Earth only in one spot in building, at counting device, after that in installation is not good to connect Earth with neutral.

In device Earth (ground) is connect to device metal case, and neutral and live wires are different and usually go to transformer.

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[treez]

thanks for the youtube video.

So, according to that video, European countries with their 2 pin plugs are doing it all wrong?

.....the video clearly states that in even of hot wire insulation damage, the hot conductor may contact the metal enclosure, and if the neutral is not wired to the metal enclosure , then no breaker would trip, and then a customer touching the metal enclosuer would die from electric shock?

So European two pronged countries are doing it all wrong?

Or is it that european countries just dont have metal enclosures?

Or if they do have metal enclosures, they coat the metal in plastic?

 

[tpetar]

No, my friend, metal case body is grounded, and ground will make protection in situation when live wire (hot) touch device metal case. Additional to this, its good to use "differential current monitoring switch".

Neutral is grounded only on one place, and that can be in house place where is electrical counting device or in front of house electrical connection place. After that you dont do grounding of neutral that can be dangerous, even you can cause fire or deadly malfunction of electrical counting device.

I hope that you will do only in Proteus simulation. :wink:



European electrical wall plug type :

US electrical wall plug type :

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Bad electrical wall plug (dont have earth connection) :

Also there is many other types variants of plugs and connectors, different to each country standard. But always wall plug should have Earth/Ground connection.

Specially in situation when plastic device case is use, then often devices have only Live wire and Neutral connections on device plug cable or direct output on case as this picture shows:

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Additional materials resources:

http://www.cyberphysics.co.uk/topics/electricity/home/earthing.htm
http://www.frankswebspace.org.uk/ScienceAndMaths/physics/physicsGCSE/earthing.htm

 

[treez]

Going back to the original question, is the output 0V of the PSU connected to Earth?

And ditto for this power supply....is its output 0V connected to Earth ground?
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I suppose I have to get a mains plug, take the back off it, then plug it in, then use a DVM on resistance scale, and probe between earth at the back of the open mains plug, and the output 0V of the PSU...I seem to remember previously doing it like that.

 

[D.A.(Tony)Stewart]

LAB supplies and Laptop chargers are ALWAYS floating DC output.

This is a safety requirement, but often bad for EMI sensitivity to high impedance inputs like microphones as the common mode noise interferes so a solid earth ground improves this. But then that makes the mic. a safety liability if there are any ground faults.

If an ac outlet or device short circuits the neutral and hot wires will have equal voltage drop on them thus making the neutral wire hot, so residential homes in North America are not connected from Neutral to Earth ground rather only at the nearby distribution transformer, so Earth ground in the home is always safe,, unless one shorts LINE to EARTH ground line.

The other problem is SMPS often have coupling capacitance and chopped current across the HF transformer so there is some additional current between the floating secondary DC and earth ; But limited to by the SMPS CM choke caps to Earth from Line & Neutral to Earth

SMPS always have 2 CM caps to earth ground using up to the 0.25mA rated leakage for the CM noise "PI" filter. However the SMPS load is a switched load so the current across the stray capacitance is pulsed and can be a significant high impedance voltage but still limited by the total series capacitance and leakage current specs.

If this becomes a problem I usually Earth ground the DC return. but am aware that the floating device is now grounded and that can improve EMI noise but expose the case to ground fault voltages.

I think they should have included an earth ground banana plug but were afraid people would criticize the units noise present on the DC return,.. THis is why Linear LAB supplies were superior than cheap SMPS lab supplies. IMHO...

Normally they are floating to give users the option for a single star ground.

BUt in this case it may be Mains ground to the AC input. Write them and ask.

My money is on Isolated but NOT grounded with 0.25mA safety limit but most CM noise.

$$$$$

 

[Orson Cart]

If it has a CE mark on it it should be isolated (this is pretty much a given) but if double insulated there will be no earth on the mains plug, there is nothing to stop you connecting the 0v out of the psu to earth...