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Thread: What's the adventage of 3-phase over single-phase?

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    What's the adventage of 3-phase over single-phase?

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    I was told by an aircon man that if a house is equiped with 3-phase power as opposed to single-phase, the power bill will be lower over time.

    Any (fresh) engineer out there care to help me understand?

    Thanks.

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    Quote Originally Posted by Nicky
    I was told by an aircon man that if a house is equiped with 3-phase power as opposed to single-phase, the power bill will be lower over time.

    Any (fresh) engineer out there care to help me understand?

    Thanks.
    I dun think any residential aircon are 3-phase ready. Your PUB meter only tab 1 phase anyway. More over, 3-phase only give you higher voltage while your bills are determine by the power(kwh) you used. So it still go back to the aircon's lust for power....

    Cheers and Regards,
    Billy Cheong

    I'm not always dumb,
    Just most of the time...

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    When I read Engineering more than 10 years ago, I remember power of 3phase is a formula that is not the straight summation of each of the phases.

    The aircon I planned to get does not need 3 phase. But with single phase 60+A I am afraid of overload and so I am wondering the difference between single-phase-100A vs 3-phase-each-60A. Then this aircon man say 3-phase cost less in long run.

    But why?

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    Quote Originally Posted by Nicky
    When I read Engineering more than 10 years ago, I remember power of 3phase is a formula that is not the straight summation of each of the phases.

    The aircon I planned to get does not need 3 phase. But with single phase 60+A I am afraid of overload and so I am wondering the difference between single-phase-100A vs 3-phase-each-60A. Then this aircon man say 3-phase cost less in long run.

    But why?
    Frankly speaking, I read those books more than ten years ago too. Can't really remember the details and formula for the calculations. I can only remember that HDB implement one phase for each storey of the flat, with a star connection for neutral.... something like that...
    Cheers and Regards,
    Billy Cheong

    I'm not always dumb,
    Just most of the time...

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    three phase power has the three phases 60 out of phase from each other. This is like multiplexing, so the max voltage is not 660VAC but the max of the overlap the three out-of-phase sine waves.

    residents where got equipment use 3-phase one? plus you will have to use those big IEC sockets.

    anyway everything I said above is hantam one, I major in Computer Science and knows nuts about electrical
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    single phase is 240v wrt to neutral.
    3 phase is 415v wrt to neutral; has 3 'live' connections. and phase angle is 120 degrees (120 x 3 = 360).

    3 phase saves power when there is constant start/stop cycle. the star-delta starter reduces the peak starting current by about 3 times.

    check singpower tariffs for industrial power. should be lower per kwh because it is considered as 'dirty' (very noisy) due to the numerous industrial loads connected to it. however, there is a peak load demand (something to do with load factor correction) and you will be penalised for under-declaring you consumption.

    if you want to save some electricity, get those compressors with inverters. compressor motor does not have start/stop cycles. runs continously at different speeds.
    thomas liew

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    old yah 120 not 60 paiseh can't even divide 360 by 3.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    let me ask the engineers here: the 415V is derived from the max composite voltage of the three phases is it? I obtained 415 by 2 240 cos (150).

    also is it true that three phase AV produces less magnetic and EMI through cancellation with each other?
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Thanks for all the reply. Found out I do not need 3-phase (because non of my home equipment need 3-phase input) but I need higher amps. Found out from Sing Powers that there is such things as single-phase-100A. Cheaper to install also. Will be going for that to ensure I can have every equipment at home turned-on at the same time.

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    Quote Originally Posted by Nicky
    Thanks for all the reply. Found out I do not need 3-phase (because non of my home equipment need 3-phase input) but I need higher amps. Found out from Sing Powers that there is such things as single-phase-100A. Cheaper to install also. Will be going for that to ensure I can have every equipment at home turned-on at the same time.
    What are you running at home that require 23kW?
    Cheers and Regards,
    Billy Cheong

    I'm not always dumb,
    Just most of the time...

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    A REALLY big chiller ?
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    A biotope terrarium for penguins...

    BC

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    Quote Originally Posted by bclee
    A biotope terrarium for penguins...
    With polar bears?
    Cheers and Regards,
    Billy Cheong

    I'm not always dumb,
    Just most of the time...

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    I was working out how much electricity I can use at one go based on my home...

    (Figures estimated and on conservative side.)
    Split aircon - 8A
    Refrigerator - 0.8A
    Lights (all on) - 2.5A
    TV - 1.5A
    Computer - 1.5A
    Water Heater - 8A
    Electric iron - 4A
    Electric kettle - 8 A
    Rice cooker - 4A
    Oven - 6A
    Washing Machine - 1.5A
    Dryer - 4A

    Total 49.8A

    Very rarely... you would have them all at the same time...

    BC

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    The problem I have is the aircon. I do not know 8A = ? BTU for Aircon.
    If you want to aircon your whole place with full compacity compressor then potentially the total current consumption will be very close to the default limit.

    If in addition you have chiller, that may just tip it over.

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    Do not mix up the cooling capacity and electricity consumption. The cooling capacity and power of the aircon unit are 2 different thing although both have the same units (kW).

    A 1/4HP chiller problem runs with <3A and normal multi-split aircon should not use more than 15A.

    BC

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    that's right. most multi-split compressors are rated at 15 or 17A. note what you see as rated current is peak, no equipment runs at peak for long. I think sustained usage at full capacity should be near to the RMS value? BC, right anot?

    I remember in the old days, the large computer disk drive controllers actually have a sequencer such that the string of disks do not all power up at the same time. this is because the drives pull full current when they start spinning, but once up to speed they will not draw anywhere near rated current.
    why I don't do garden hybrids and aquarium strains: natural species is a history of Nature, while hybrids are just the whims of Man.
    hexazona crumenatum Galleria Botanica

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    Quote Originally Posted by bclee
    I was working out how much electricity I can use at one go based on my home...

    (Figures estimated and on conservative side.)
    Split aircon - 8A
    Refrigerator - 0.8A
    Lights (all on) - 2.5A
    TV - 1.5A
    Computer - 1.5A
    Water Heater - 8A
    Electric iron - 4A
    Electric kettle - 8 A
    Rice cooker - 4A
    Oven - 6A
    Washing Machine - 1.5A
    Dryer - 4A

    Total 49.8A

    Very rarely... you would have them all at the same time...

    BC

    kinda agree with u .... unless u on everything at the same time if not.. no need to much A
    I Doesnt haVe GReen HAIr NoR orANGE bodY. DOnT chOP mE likE A cARroT !!

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