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[Kevin Wood]

On a practical level is there any advantage to be had with a three phase supply to non commercial premises.

Over and above that. can anyone explain (in language easily absorbed by this idiot) what the difference is between the two? (Other than one being single and the other being triple of course)

Essentially, you can transfer more power with less copper in the cable for a given amount of power loss in the cable, which is why most of the transmission network is 3 phase.

In terms of its' advantages to the consumer, you can make a 3 phase induction motor much more efficient than one operating from single phase, both in terms of power consumption and physical size.

Because the power is delivered to the load constantly, rather than with a 100Hz interruption in current flow, vibration in motors and other equipment is reduced and applications where the mains is rectified to DC work much more effectively on 3 phase power.

Think of it as power delivered from a proper V6 engine (a power stroke every 120 degrees) as opposed to a 2 cylinder 4 stroke engine (2CV / Fiat 500?).

For this reason, and because, for large loads, it's important for the supply network that the load is evenly balanced between the 3 phases, the 3 phase mains from the grid is continued into the premises for industrial applications but a home is typically fed only one of the phases.

Kevin

[Lizzie_Zoom]

On a practical level is there any advantage to be had with a three phase supply to non commercial premises.

Over and above that. can anyone explain (in language easily absorbed by this idiot) what the difference is between the two? (Other than one being single and the other being triple of course)

Essentially, you can transfer more power with less copper in the cable for a given amount of power loss in the cable, which is why most of the transmission network is 3 phase.

In terms of its' advantages to the consumer, you can make a 3 phase induction motor much more efficient than one operating from single phase, both in terms of power consumption and physical size.

Because the power is delivered to the load constantly, rather than with a 100Hz interruption in current flow, vibration in motors and other equipment is reduced and applications where the mains is rectified to DC work much more effectively on 3 phase power.

Think of it as power delivered from a proper V6 engine (a power stroke every 120 degrees) as opposed to a 2 cylinder 4 stroke engine (2CV / Fiat 500?).

For this reason, and because, for large loads, it's important for the supply network that the load is evenly balanced between the 3 phases, the 3 phase mains from the grid is continued into the premises for industrial applications but a home is typically fed only one of the phases.

Kevin

Yes, with each phase cycle, 1,2, & 3 timed to run outside of each other   But Kevin, shouldn't that be 50 Hz, not 100Hz per second? :-/ :-/

You can apparently save money using this system, but the cost of installation is prohibitive to most domestic customers

[Kevin Wood]

Yes, with each phase cycle, 1,2, & 3 timed to run outside of each other   But Kevin, shouldn't that be 50 Hz, not 100Hz per second? :-/ :-/

No. Power is delivered to the load on both the positive and negative half-cycles of the AC supply but drops during the zero crossing of the waveform.

Kevin

[Lizzie_Zoom]

Yes, with each phase cycle, 1,2, & 3 timed to run outside of each other   But Kevin, shouldn't that be 50 Hz, not 100Hz per second? :-/ :-/

No. Power is delivered to the load on both the positive and negative half-cycles of the AC supply but drops during the zero crossing of the waveform.

Kevin

Thanks for clarifying that Kevin

[aaronjb]

All I know is, I don't mind messing with single phase power.. but the thought of messing with 415V with the potential for something like 300A scares the bejeezus out of me..

[russ0205]

I asume you have done it to 17th edition regs lizzie,  LOL.
As for female electricians i used to work with a few on british gas they did a dam good job.

[hotel21]

To add to Zulu's request for info, my recollection is that its 3 phase supply through the pole/underground network at 440volts or thereby at street/housing estate level.  If you take any one pair of the 3 cables and run them into the houses, you then have single phase at 240volts or so.

All other explanations as per Kevin and co are obviously valid. 

[Debs.]

On a practical level is there any advantage to be had with a three phase supply to non commercial premises.

Over and above that. can anyone explain (in language easily absorbed by this idiot) what the difference is between the two? (Other than one being single and the other being triple of course)

Essentially, you can transfer more power with less copper in the cable for a given amount of power loss in the cable, which is why most of the transmission network is 3 phase.

In terms of its' advantages to the consumer, you can make a 3 phase induction motor much more efficient than one operating from single phase, both in terms of power consumption and physical size.

Because the power is delivered to the load constantly, rather than with a 100Hz interruption in current flow, vibration in motors and other equipment is reduced and applications where the mains is rectified to DC work much more effectively on 3 phase power.

Think of it as power delivered from a proper V6 engine (a power stroke every 120 degrees) as opposed to a 2 cylinder 4 stroke engine (2CV / Fiat 500?).

For this reason, and because, for large loads, it's important for the supply network that the load is evenly balanced between the 3 phases, the 3 phase mains from the grid is continued into the premises for industrial applications but a home is typically fed only one of the phases.

Kevin

Turning on my old 1ph. Quasi-Arc 'static' welding set (400 amp./90 OCV. transformer) makes a tremendous 50Hz. 'whump' and visibly dips my (& my neighbours) lights on switch-on......
......"She`s at it again, Maureen!"

[pirate]

very impressed , so many bits of paper that have to be passed to do enything nowerdays,

[Dishevelled Den]

Thank's to Kevin and H for expanding on my question about the 3 phase supply. 8-)

I have now grasped the basics of a thing that has puzzled me for a wee while now. 

[Kevin Wood]

To add to Zulu's request for info, my recollection is that its 3 phase supply through the pole/underground network at 440volts or thereby at street/housing estate level.  If you take any one pair of the 3 cables and run them into the houses, you then have single phase at 240volts or so.

All other explanations as per Kevin and co are obviously valid. 

Almost.

We have 400V 3 phase in the domestic supply network these days since harmonising voltages with Europe. Between any 2 phases you get 400V AC in such a system. Between any one phase and Neutral you get 400 x Root(3) volts = the nominal 230 volts we use domestically.

If the phases are in balance the current through the neutral conductor cancels out, so for much of the network there is no neutral conductor required (look at power lines - the wires are in multiples of 3).

In a domestic setting, the balance is less good on a local level so the transformer in the local substation is wound to provide a neutral connection.

Turning on my old 1ph. Quasi-Arc 'static' welding set (400 amp./90 OCV. transformer) makes a tremendous 50Hz. 'whump' and visibly dips my (& my neighbours) lights on switch-on......
......"She`s at it again, Maureen!" Roll Eyes

My valve amp does the same.

Kevin