1 Phase or 3 Phase Power

In some homes in Africa, 3 phase power at 220 Volts is used. Can someone help me in knowing the advantages and disadvantages of using 3 phase instead of 1 phase? I would think 3 phase power will cost more in utility bill, am I wrong?


Reply to
Kissi Asiedu
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You are wrong. Energy usage would be billed in kWh. Connect 3 - 100 watt bulbs to a three phase service, or the same 3 bulbs to single phase and you still get 300 watts.

Charles Perry P.E.

Reply to
Charles Perry

This is more of a political/marketing question than a technical one. Therefore, the only way to know is to ask the electic utility. They probably bill you per kWh, which means it doesn't matter.

where it is located and the system voltage. If you want a 30 kW supply for an apartment building in a city, a three phase 220/380V service is cheaper than a 220V single phase service.

If you instead is located in a village and need a 3 kW supply for a home, a single phase 220V will be cheaper. If you want you can find in depth analysis of cost/benefit for different distribution system on the net.

One of the reasons is the load balancing: It is difficult to balance a

3 kW three phase service: Each phase will carry only 1000 W. Typical single phase loads like a hairdryer or vaccum cleaner draw more than this and can't be used despite the fact that the supply is 3 kW.

For this reason, you will rarely find 3-phase supplies smaller than 10 kW.

On the other hand, 220V single phase is an inefficient way to transfer a lot of power. At 30 kW, you can load every phase with 10 kW. There are almost no single phase loads this large and the balancing therefore is little problem.

Three phase requires less copper than single phase to conduct the same amount of electricity. As copper is expensive you will rarely find single phase supplies larger than 30 kW in countries with 220/380V systems. (It is a different story in North America)

With 3-phase you can also run large motors. Large single phase motors are very expensive.

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----------- And single phase motors are comparitively complex and inefficient. They compete in smaller sizes only because the supply is then typically single phase and there are so many built that there is an economy of scale. This comment is in line with what you have said- and the economics of power generation/transmission and utilisation are essentially the same everywhere.

Reply to
Don Kelly

disadvantage: unbalancy-protection cost - huge currents in fault condition

- difficult cabling

advantages: more power for special equipment - 2 phase backup for each 1 phase in emergency

in a range between 0 kw - 7.5 or X kw (depends to standard) we use 1 phase and for more 3 phase

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