Probably a silly question but considering hardly anyone knows which side of the mains connection is live and which is neutral, why do power supplies have dedicated connections for these?
Is it still recommended to put the fuse in the line to the "live" connector? (I would anyway as there is no reason to put it in the other).
Is it still recommended to put the fuse in the line to the "live" connector? (I would anyway as there is no reason to put it in the other).
Think of it this way: If you fuse neutral, and the fuse blows, there is still "hot" live inside the box, which might find some other path to ground. If you fuse the live leg, the fuse will likely be located physically near the power entry, so there is no "hot" line floating around inside the chassis. The fuse should be the first thing the live leg sees inside the chassis, even ahead of the power switch.
Both preceding posts are spot on. Unpolarized power plugs/sockets are still found in parts of Europe which is IMO not a very good idea precisely for the reasons mentioned.
All wall sockets here in the U.S. are polarized, and with the exception of a some double insulated devices the plugs are also polarized so that hot and neutral are clearly defined - unless of course the wall socket is wired incorrectly. (It happens)
All wall sockets here in the U.S. are polarized, and with the exception of a some double insulated devices the plugs are also polarized so that hot and neutral are clearly defined - unless of course the wall socket is wired incorrectly. (It happens)
In my plan for a class D amp with prefab board, I want to put an regulated SMPS. The live wire will go from connection to fuse to switch to connection on SMPS. The neutral wire will go straight to the connection on the SMPS.
Is this the correct way?
Should I take the inrush current of the power supply into account when selecting a fuse rating or should I take the "normal" max current?
Is this the correct way?
Should I take the inrush current of the power supply into account when selecting a fuse rating or should I take the "normal" max current?
Thanks for the valuable input!
I have my eye on a 15VDC 5A supply (on 230VAC mains). A TDK-LambdaLS75-15.
Manual
Datasheet
It in terms of current handling it has some head room for the class D amplifier (TPA3116) which I do not expect to draw more than 2 amps.
What should the fuse and switch be rated for?
I have my eye on a 15VDC 5A supply (on 230VAC mains). A TDK-LambdaLS75-15.
Manual
Datasheet
It in terms of current handling it has some head room for the class D amplifier (TPA3116) which I do not expect to draw more than 2 amps.
What should the fuse and switch be rated for?
That's the way it should be.
But the mains supply outside is 4 wires with voltages of 230Vac or 400Vac between them.
An almighty calamity is possible and the wrong voltage/s can appear on the supply to your property.
A fuse should protect you, but it's not completely foolproof.
The Supply company will do all that is physically possible to keep the Neutral voltage near Earth reference.
PE is usually connected to that Neutral at the distribution board.
If there is wire armour around your supply cable, it too will connect to "earth" somewhere.
These supply arrangements are there to protect the customers.
Don't try to modify them.
Don't put in any form of "amateur" technical earth.
It is potentially a killer when lightning strikes.
Live should be the ONLY elevated voltage inside your home.
Here in the USA I've seen entire houses wired backward. I wouldn't trust wiring without checking.
Rcw,
I found your reference to Neutral to Earth connection on the back of most/every socket outlet interesting. (have I read your description correctly?)
I googled and have looked at a few references.
MEN (Multiple Earth Neutral) is mentioned repeatedly.
This applies to the distribution and transmission systems.
It also applies to the domestic supply BEFORE the meter.
I cannot see any reference to what you described.
Can you help by providing a link?
I found your reference to Neutral to Earth connection on the back of most/every socket outlet interesting. (have I read your description correctly?)
I googled and have looked at a few references.
MEN (Multiple Earth Neutral) is mentioned repeatedly.
This applies to the distribution and transmission systems.
It also applies to the domestic supply BEFORE the meter.
I cannot see any reference to what you described.
Can you help by providing a link?
It wouldn't make much sense to have the neutral and earth bonded anywhere downstream of the service panel without the use of a transformer. The net result would be load current flowing through the ground wire.
Back in the early 1900's circuits were often a single hot, using the conduit or uninsulated sheathing material as a return. This was responsible for numerous 'tickles', and potentially a few deaths in wet basements, so code was written to ban the practice.
It is desired that load current return on an insulated conductor, and the ground, whether it be a green conductor or a metallic raceway, never carry intentional current.
Back in the early 1900's circuits were often a single hot, using the conduit or uninsulated sheathing material as a return. This was responsible for numerous 'tickles', and potentially a few deaths in wet basements, so code was written to ban the practice.
It is desired that load current return on an insulated conductor, and the ground, whether it be a green conductor or a metallic raceway, never carry intentional current.
Correct, and this is further support for why the US code does not permit balanced power in residential electrical systems. Blow one fuse, the other leg is still energized above 50V (the accepted value above which arcs can manifest and sustain themselves). Ref. NFPA 70E.
Multiple earth neutral is employed here too, just always no further than the breaker panel. My system is per local code and has two co-located ground rods, a water pipe ground and the neutral is also grounded at the pole by another ground rod. (Gas lines should never be bonded to the electrical grounding system due to the potential for electrolysis and other issues - here it is a code violation.) A large number (IIRC 12) of other residences are connected to the same transformer and all have similar grounding arrangements.
Ground and neutral are keep entirely separate outside of the panel such that no intentional load current flows in the ground just as zigzagflux states.
I would assume this approach would apply anywhere where the harmonized electrical safety standards apply.
Ground and neutral are keep entirely separate outside of the panel such that no intentional load current flows in the ground just as zigzagflux states.
I would assume this approach would apply anywhere where the harmonized electrical safety standards apply.
I was nor referring to individual appliances but to the distribution system.
Single phase to a dwelling is derived from a delta wye connected three phase transformer, the wye center tap is earthed at the transformer, and again at the destination, a separate earth is incorporated in the building wiring with a separate earth point.
The neutral is usually at a potential above that of earth dependent upon the current being drawn in the circuit, but at worst can only give a tingle.
As an aside at one time they had fully floating mains in the USA with no safety earth, they changed some time in the 70's.
rcw
Single phase to a dwelling is derived from a delta wye connected three phase transformer, the wye center tap is earthed at the transformer, and again at the destination, a separate earth is incorporated in the building wiring with a separate earth point.
The neutral is usually at a potential above that of earth dependent upon the current being drawn in the circuit, but at worst can only give a tingle.
As an aside at one time they had fully floating mains in the USA with no safety earth, they changed some time in the 70's.
rcw
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.