Explain 3 phase electricity to me

s0lar

s0lar

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I hooked up a FTDI interface to my electricity and gas meter. Here in the EU "smart meters" are a thing which is convenient. I am shipping the data to Prometheus to be graphed in Grafana every 5 minutes to get a view on my usage.

This peaked my interest in what I am seeing and whats got me..

Is how do phases work? Why are they separate? And why (if I am correct) or rather it appears different appliances use different phases?

1690019564274.png
 
You can watch a Youtube video for a technical explanation but basically you have three power lines coming in, some devices will be on the one line and other devices on the other lines or some big power consumers like a motor or central heating will used all three lines. These lines need to be balanced e.g. balanced usage or else you get penalized. So just look at the device's plug if it's three prongs it's a single phase device on one of the three legs, plugs with four or more wires is three phase plugs which use all three legs at the same time.
 
OK so the generator has three windings and it generates three sine waves (AC) 120 degrees apart. If you apply this to a motor with three windings the motor too will rotate like the generator, and there you go.

So typically houses are wired to phase 1, next house phase 2, next house phase 3, lather rinse repeat. This balances the load on the three phases.

Unless you get supplied with three phase, which looks like is the case. Then, your plugs / lights / etc are wired to phase 1 / phase 2 / phase 3 to balance the load.

Typically, one plug circuit on one phase, another plug circuit on another phase, lights on the third phase. Depends on how big your house is.

A stove would be two plates on one phase, two plates on another phase, oven on the third phase.

So to answer the question, depends on how it's wired or where it's plugged in, yes, different appliances would use different phases.
 
Koos Custodiet said:
OK so the generator has three windings and it generates three sine waves (AC) 120 degrees apart. If you apply this to a motor with three windings the motor too will rotate like the generator, and there you go.

So typically houses are wired to phase 1, next house phase 2, next house phase 3, lather rinse repeat. This balances the load on the three phases.

Unless you get supplied with three phase, which looks like is the case. Then, your plugs / lights / etc are wired to phase 1 / phase 2 / phase 3 to balance the load.

Typically, one plug circuit on one phase, another plug circuit on another phase, lights on the third phase. Depends on how big your house is.

A stove would be two plates on one phase, two plates on another phase, oven on the third phase.

So to answer the question, depends on how it's wired or where it's plugged in, yes, different appliances would use different phases.
Click to expand...

A lot of older houses all over the country still have 3 phase. Would be interesting to find out why when a house only needs 1 phase to function, unless you're running industrial machinery or a pottery kiln or something crazy like that.
 
deweyzeph said:
A lot of older houses all over the country still have 3 phase. Would be interesting to find out why when a house only needs 1 phase to function, unless you're running industrial machinery or a pottery kiln or something crazy like that.
Click to expand...
Its cheaper on cable.

Running 80A to a house on 3 phase uses less copper.
 
Thanks all, I decided to spent some time and educate myself on the youtube and the interwebs. Interesting stuff.

Kind of cool these phases. I can now see my grow tent and the fridge on the same phase. Easy to extrapolate the grow tents power usage without specific kit to measure each appliance or wall socket. Can now work out my ROI on expensive LED lights and other random geekery to a reasonable degree.
 
s0lar said:
Thanks all, I decided to spent some time and educate myself on the youtube and the interwebs. Interesting stuff.

Kind of cool these phases. I can now see my grow tent and the fridge on the same phase. Easy to extrapolate the grow tents power usage without specific kit to measure each appliance or wall socket. Can now work out my ROI on expensive LED lights and other random geekery to a reasonable degree.
Click to expand...
just remember across phases the voltage is higher than each phase to neutral ,ie phase to phase is 380 volt and phase to neutral is 230 volt ,depending on which country you are in .US is 120 per phase to earth or 240 across 2 phases .
 
Koos Custodiet said:
OK so the generator has three windings and it generates three sine waves (AC) 120 degrees apart. If you apply this to a motor with three windings the motor too will rotate like the generator, and there you go.

So typically houses are wired to phase 1, next house phase 2, next house phase 3, lather rinse repeat. This balances the load on the three phases.

Unless you get supplied with three phase, which looks like is the case. Then, your plugs / lights / etc are wired to phase 1 / phase 2 / phase 3 to balance the load.

Typically, one plug circuit on one phase, another plug circuit on another phase, lights on the third phase. Depends on how big your house is.

A stove would be two plates on one phase, two plates on another phase, oven on the third phase.

So to answer the question, depends on how it's wired or where it's plugged in, yes, different appliances would use different phases.
Click to expand...
Many old stoves just have a loop connecting all three phases so you can run it on one phase
 
krieg said:
You can watch a Youtube video for a technical explanation but basically you have three power lines coming in, some devices will be on the one line and other devices on the other lines or some big power consumers like a motor or central heating will used all three lines. These lines need to be balanced e.g. balanced usage or else you get penalized. So just look at the device's plug if it's three prongs it's a single phase device on one of the three legs, plugs with four or more wires is three phase plugs which use all three legs at the same time.
Click to expand...

In a household environment won't get penalized for un balanced loads
 
thehuman said:
In a household environment won't get penalized for un balanced loads
Click to expand...

Not sure where in Europe OP is but on the UK electricians' videos the supplier actually does require the load to be balanced and will send out a notice if you're way out, spark comes in and attaches a data logger device for a week, analyse it and move some circuits around. Unbalanced load will also affect motors negatively connected to your three phase system. Not an expert. I'm sure in South Africa there is no standard or care.
 
krieg said:
Not sure where in Europe OP is but on the UK electricians' videos the supplier actually does require the load to be balanced and will send out a notice if you're way out, spark comes in and attaches a data logger device for a week, analyse it and move some circuits around. Unbalanced load will also affect motors negatively connected to your three phase system. Not an expert. I'm sure in South Africa there is no standard or care.
Click to expand...
in SA it used to be a thing ,unbalanced was frowned upon .but no longer as you now pay per phase and not peak .in industry its a bit different but not in a domestic supply .
 
deweyzeph said:
A lot of older houses all over the country still have 3 phase. Would be interesting to find out why when a house only needs 1 phase to function, unless you're running industrial machinery or a pottery kiln or something crazy like that.
Click to expand...
High-power electric motors need three phase. Your pool pump or washing machine or whatever cheats, either using a shaded pole or a starter capacitor to generate a phase shift to get the thing turning in the right direction.

A borehole pump typically needs three phase. So does machine shop type equipment, anything larger than the smallest lathe or milling machine. Previous owner of the place I'm in had it wired for three phase for his machine shop.

In South Africa you get single phase at 60A, or three phase at 40A which is twice the power (and you pay for it of course).

And yea leon, I know a stove can be jumpered for single phase, most are, since most houses are single phase. And in a three phase house you can install it single-phase, but then you might trip that 40A breaker if you light everything up at the same time.

Balance is not a big thing in domestic because it's lots of small loads which cancel one another out. Balance is big in a factory etc. As is power factor, but let's not go there :-)
 
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