Why are there 2 different standards?

[Big_Richard]

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[oscar]

The actual planet  earth is used as the earth in US power systems, it saves having to run another wire all the way back to the powerplant. A standard outlet in a US home has three conductors. 1 - Live 120V ac, 2 - neultral (connected to ground at the fusebox, completes the circult), 3 - ground (connected to ground in some manner, functions to provide a return for current incase the neutral is interrupted so that you don't get shocked)

Zepp, so does US houshold power points have two or three sockets? ie do appliance plugs have three prongs?  I always assumed you guys had two.  But then again, not all our appliances are equipped with a third earth prong.  For example, a TV will but a an electric shaver wont.  Not sure what the standard or rules are.

I had no idea that the indicator stalk position is also mirror imaged on LHD cars. I thought they were always on the right hand side of the steering wheel! Except on older volvos and beemers, i noticed they were on the left..

My first experiences was with work cars which all have the indicator stalk on the left hand side of the column.  Even now, 8 years down the track I'll be tearing along in a VW transporter with all the bells and whistles on and go to turn right and activate the wipers instead   We've got GMC's and MB sprinters too, they're all the same.  Then on days off you get the reverse and drive cars designed for RHD with the indicator stalk on the RHS. After being conditioned by using the left hand stalk you have to get used to the right hand stalk again.

[koan]

The actual planet  earth is used as the earth in US power systems, it saves having to run another wire all the way back to the powerplant. A standard outlet in a US home has three conductors. 1 - Live 120V ac, 2 - neultral (connected to ground at the fusebox, completes the circult), 3 - ground (connected to ground in some manner, functions to provide a return for current incase the neutral is interrupted so that you don't get shocked)

That's just the same as AUS and probably most of the world. It's a MEN sysytem, Multiple Earth Neutral.

Active, Neutral and Earth run round the house, Earth and Neutral connect together at the fuse box/switch board, the Neutral an Earth connect to an earth spike in the ground. Two wires, Active and Neutral go to the street pole. Out in the street some of the poles have a Earth spike next to them which connects to the Neutral wire on the pole, this keeps the Neutral wire at earth potential.

Not to be confused with SWER, Single Wire Earth Return used in a lot of the bush.  Just one Active wire on the poles, the earth being the return conductor. From memory the resistance between any two points on the earth's surface is 7 Ohms.

The only place I know of not using MEN was Melbourne City Council, they used to be the supplier for the city. They ran a separate Earth on the poles, the electricians used to curse it because it allowed the Neutral to be float some voltage above Earth upsetting a lot of electronic gear.

koan

[zeppelinboy]

PB - our earth wiring is the same

Oscar - most electrical items in the US have 3 prongs, some things like lamps and other light duty stuff do not have 3. I have no idea what the standard is to require a third prong, however all sockets installed in the last half century or so have 3 holes. There are adapters which allow you to plug something with three prongs into an older (pre 1960's I believe) 2 prong socket. The adapters have an external metal tab which should be connected to ground in some manner.

240 V appliance require 4 prongs 1 for each phase (2), 1 for neutral and 1 for ground. The neutral is required because things like  timers inside the appliance require 120V. An older standard allowed the ground to be used as neutral on these appliances, so some only have 3 prongs, but this is very dangerous as it allowed current to flow on the ground wire. Ground wires in US systems are not insulated and are sometimes pipes and or conduit instead of a discrete wire.

The main drive for 1 transformer/house is reliability. If the transformer goes down it only affects one house instead of an entire block or neighborhood. That said it does become a huge pain when a substation goes out (usually a car crash or something similar) because a large section will then be without power.

Also it is almost impossible in the US to get 3 phase power run to your house for running lathes/milling machines etc unless you live in an industrial area which already has a three phase customer.

I believe the 120V standard in the US comes from the 100V DC system that edison used in NY city. Why 240 is used elsewhere is most likely the result of people trying to make their systems better ("our system has double the voltage") and/or attempts to get around patents. This is just conjecture as I have no proof nor seen any proof as to the real reasoning behind the standards.

[Martin 280s]

Why is it seen necessary to have some countries run on ~240v 50hz AC while some choose to run on ~110v 60hz AC.

In Brazil some houses have both voltages in single or three phase!

[johnnyw116]

hi i was reading here about voltages do you use for big electric machines also 380volt voltage ? or other voltage ?
here in holland we use 220/240volt and 380volt             

[OzBenzHead]

Johnny: In Oz it's commonly 240V for domestic and (very) light industrial use; 415V 3-phase for industrial applications.

[WGB]

In Australia most normal houses were wired up with a single phase 240 volt supply only.

Every house (Unless very remote rural) would have 3 phases running along one boundary either as overhead wires or underground supply.

It's just a matter of choosing and paying for the connection and extra wiring costs.

Most newer bigger houses would all have a 3 phase 415volt airconditioner (or several) so it is easy to get 3 -phase to a workshop if ythe house is already connected.

I live on a rural property and pump my own water - in the past for irrigation - using a 10Hp and a 15 Hp pumps which require 3 phase supply.

My house has a 10Hp heat pump reverse cycle airconditioner and I have two pool pumps , a submersible bore pump and a pressure pump for water supply to the house.

My shed has multiple single phase 15 amp outlets (Standard domestic is 10 amp - 240volt) as well as 20 and 30 amp 3 phase 415 volt outlets.

My Power Bill would make your eyes water.

Bill

[oscar]

Most newer bigger houses would all have a 3 phase 415volt airconditioner (or several) so it is easy to get 3 -phase to a workshop if ythe house is already connected.

I got excited by this news and the fact a mate said something similar yesterday.  Mind you, after 4 or so weeks in this new house our A/C shat itself on Sunday right before our little heatwave arrived.  But, anyway, my mate said if there's 4 wires running from pole to house and 3 big ass fuses in the meter box, there should be 3 phase to the box at least.    It seems I have but the A/C guy told me today that the A/c is a single phase inverter unit.  Supposed to be cheaper to run (when it frickin works).

Nonetheless, there's potential to run 415V 3 phase to the shed thru existing conduit under the concrete to the shed without having to pay the big $ to get the electricity company to run the extra wires from the pole.  Oh well, one day I'll do it.  I don't own any 3 phase tools or machinery.

[oscar]

Well there's two things I want/need - car hoist, MONSTROUS compressor and throw in a range of welders to replace my stick welder. 

I'll do with a decent compressor at the very least and dig a pit instead.  I've gone thru two real cheap no-name compressors, one cracked a cylinder, the second dropped a valve and I've learnt to buy quality from now on.  But you're right Michel, perhaps 3phase isn't necessary these days particulary as many tools and machinery are being redesigned to suit household single phase supply. Eg, hoists are available as single phase these days with enough cap' to lift a w116.

[WGB]

My car hoist runs 3 phase and when I came to wire it up it had the three phases and earth as well as a neutral wire. Unfortunately the power supply didn't include a neutral wire and I thought I might have to re-wire my shed. For some reasomn the visible neutral wire went around a corner in the hoist and was screwed into a terminal connector with nothing else connected to it - saved a lot of expense.

I had Fruit sorting Machinery in my shed originally which used three phase power and that is why I am wired for any emergency. Apparently small three phase engines run cooler and more efficiently as well as handling bigger power loads more easily.

Another use for three phase is a big welder.

Maybe I need a monstrous compressor - maybe not.

Bill