1 phase vs. 3 phase 220v AC

This is something I hadn’t encountered before. I’m looking at a piece of equipment that uses 220v AC but there’s different versions for 1 phase or 3 phase AC power. Are both available here, and is one more common than the other? Any advantages or disadvantages between them?

This web site gives a technical explanation (probably more than you want to know):

windstuffnow.com/main/3_phase_basics.htm

The following is probably the most important part:

Most of the electric power in the world is 3 phase.
The concept was originally conceived by Nikola
Tesla and was proven that 3 phase was far superior
to single phase power. 3 phase power is typically
150% more efficient than single phase in the same
power range. In a single phase unit the power falls
to zero three times during each cycle, in 3 phase it
never drops to zero. The power delivered to the
load is the same at any instant. Also, in 3 phase
the conductors need only be 75% the size of
conductors for single phase for the same power
output.

[quote=“Dog’s_Breakfast”]This web site gives a technical explanation (probably more than you want to know):

windstuffnow.com/main/3_phase_basics.htm

The following is probably the most important part:

Most of the electric power in the world is 3 phase.
The concept was originally conceived by Nikola
Tesla and was proven that 3 phase was far superior
to single phase power. 3 phase power is typically
150% more efficient than single phase in the same
power range. In a single phase unit the power falls
to zero three times during each cycle, in 3 phase it
never drops to zero. The power delivered to the
load is the same at any instant. Also, in 3 phase
the conductors need only be 75% the size of
conductors for single phase for the same power
output.
[/quote]

here’s an easier to understand explanation: if ur trying to turn some big motor, like a central HVAC(air conditioning unit) then 3 phase is more efficient than single phase. 3 phase electricity is expensive though. if the majority of your electrical appliances are single phase then it is probably not economical to convert your entire household to 3 phase just so that you can run one piece of 3 phase equipment, as the 3 phase electrical feed will need to be re-converted to single phase for use in the rest of your home. Taipower charges 3 phase at a higher rate than it does single phase.

OK, that helps me understand what 3 phase is, but if I have say an outlet for an air conditioner in my house, is that likely to be 1 phase or 3 phase?

OK, this is what I can remember from like 10 years ago, LOL. It’s far from a complete answer, but it might get you closer.

Generators tend to produce 3 phase. It’s just the way they’re made. The Outputs are placed in three positions around the coil and are 120 degrees out from each other.

Now what happens is that all three phases get piped down your street and at one stage ONE of these is piped into a building. Often, if the building warrants it, all three phases are piped in, and then split up once they hit individual dwellings.

Each one of these phases is your typical 50/60Hz sine wave sort of thing, providing the 110/220 (or whatever) V(AC) of electricity.

One of the reasons why you might get all three phases in your building is so that they’re split more or less equally among the dwellings, meaning that each phase uses about the same amount of current on average, hence keeping the whole thing more or less in balance, i.e. you don’t get one of the phases burning out the generator coil, while the other two were hardly doing anything. It’s all to do with making the most of the three outputs.

Anyway, I would guess that your appartment probably has single phase.

Hope you can understand what I’m trying to say. I know your technical knowledge is pretty strong, jlick.

I think all sockets (or outlets, or whatever you call them) that you can find in a household are 1-phase only, including the air conditioner sockets.

Anyway, just to be sure, get an oscilloscope and check it yourself! :slight_smile:

Well, don’t you need at least 4 cables to have your three phases, 3 cables for the different phase and one for neutral, and typically green is for ground. All my power plug have 2 or 3 connectors, 1 phase, 1 neutral and some have a ground. So what is coming out of your socket only has 1 phase. Here is an interesting article on wikipedia.org, that explains it very well. en.wikipedia.org/wiki/Three-phase_electric_power

Typically, at least where I am from, the electric stoves are connected to three phase electric power, but there is not socket in the wall, just some wires. We have a 3 phase socket in our garage if I remember correctly. In my appartment here in Taiwan, I look in the fuse box, and see only two wires coming in, the huge ones, connected to the 70 A curcuit breaker. I wish I had 3 phases to hook up my A/C though. But generally that means rewirering.

Oh, and three phase has the advantage that you can get different potentials, depending on how you wire things up.

There are two phases (here we go!) supplied to the house. I am not sure which two phases they are, or whether it matters. I also don’t know how far they are out of phase either, and as I don’t have an osiliiscope (or a dictionary) I’m not likely to find out.

Here’s what I suspect is the case. The two phases are 120 degrees out and drive the 220V a/c at whatever the RMS of them added together is and divided by the number you first thought of. I reckon it’ll give you 208V if you use Live 1 (the green, brown, blue, pink, yellow, or black) with Live 2 (the striped orange and purple, white, dark green, or The Other One) between the phases. Then you would have Live 1 Live 2 and Neutral at the plug. Neutral may or may not be connected to earth. If it’s a Protected Neutral Earth system, or your address has an odd number in it, it probably is, depending on how many Whisbys the “electrician” had that day.

OR, and it is just a theory, the two lives are connected to each other with insulating tape giving 220 volts, a neutral, and a small fire. The earth pin is connected in the basment to an old bag of potatoes. This is unless the generator has a centre tap. If it does, make sure to turn the tap on for a few minutes before testing until the water runs clear. Turn the tap off and then apply the ammeter clamp with a bit of vaseline.

If in doubt just stick your hands into the fusebox and rummage around. Electricity’s quite safe and can’t hurt you at all.

I doubt anyone’s got 3-phase. Well not all three phases, anyway. Where I come from, the Old Resting Home for Retired Alcoholics and M-M-M-Mad Engine Ears, in Basignstoke, our three phase supply for our ECT machine has five wires: three lives, a neutral, and a green one. That means three of us can use it at once by holding one of the red wires each and joining hands. There was also another earth supplied by the electricity board, but I swallowed it by mistake.

Hope that helps.

Yeah, I was kinda wondering myself how you could possible have three-phase with just 3 wires…

21p, you obviously know the way of the Taiwanese electrician :stuck_out_tongue:

I Think RichardM’s phaser has all 3 phases: kill, stun and tickle.

You actually have grounding in your building? We don’t even have a bag of potatoes around this part of town!

OK, I think I understand things a bit better now. Thanks for the Wikipedia link that really helped. I guess going with a single phase version will be the easiest. Thanks!

Can you tell us if the 3-phase one has a funny 5 pin plug? I’m curious now.

To be serious for a millisec, I think the meaning of the different versions is that one plug is wired L1 (110V), L2 (110V +120 degrees phase shift), and neutral, giving about 208V between L1 and L2, and the other plug 220V L, N, E single phase. I have been told that single phase 220V is being supplied to some newer houses, but I don’t know. My house is all 110V, but with two single phases so you can add them to get 220V or something similar.

A common or garden multimeter will tell you what plug you’ve got.

In one house I lived in I did indeed have the L1, L2, N, “220V” arrangement at the plug. (An a/c unit drawing 65A peak and 8A normal load with no earth and a metal case. Superb stuff.)

Have not seen the 3-phase Funny Plug here. The ones I have seen elsewhere only had 4 pins as the earth was not included. I might get some from RS and threaten my electrician with them.

In a quest to advance forumosa science I thought I would take a look at my own 220V supply. It appears I too have the L1, L2, N arrangement, however I was surprised to see the 2 phases 180

Taiwan uses the TT System which has two phases (L1, L2) and a Neutral (N). L1 to L2 gives 220V while L1 to N and L2 to N give 110V. Your house / apartment may be supplied with all 3 or only two of them (L1+N or L2+N).

A three phase supply is usually only available for industrial sites in Taiwan - it gives 380V (L1, L2, L3) or 220V for each phase against N.
Three phase supply is required for equipment that requires high power, e.g. machinery, industrial heaters etc.
In Germany even normal houses have a 3-phase supply; water heaters, electric ovens/stoves etc. typically run on a 3-phase supply while other equipment runs on 220V (now 230 or 240V even). The 220V circuits are typically wired in a way that the load is shared between the three phases (against neutral), thus avoiding tripping of circuit breakers when a lot of electrical equipment is in use.

Based on local regulations in Taiwan the Neutral must not be connected to ground / Protective Earth (PE). However most houses (i.e. residential places) don’t have a ground / PE to begin with …

(BTW: My theory says that L1 and L2 should be in phase so they add up to 220V; in a three-phase system L1, L2 and L3 are 120 degrees out to each other, thus you get 380V).

If both L1 & L2 were in phase wouldn’t you end up with nothin ? ie: both at the same potential ? :s

[quote=“Connel”]however I was surprised to see the 2 phases 180

Ups, of course - you are right. :blush:

It has to be the “opposite” of “in-phase”, i.e. as Andre said they should be out of phase by 180 degree.

At least in US, they distribute 3 phases, 120 degrees apart.
Only industrial buildings get all 3. Houses get 2 of the phases.
When you wire up your circuit box, you wire L1 to one of the rails,
L2 to another, and Neutral also. When you pop in the circuit
breakers from Home Depot, most of the circuits will go across
L1 to neutral or L2 to neutral. The big ass appliance breaker
goes across both hots (L1 and L2) and yields 220 for electric
ovens and dryers.

Not sure what is up with your plug or if they wire 220 into the
houses here, heck they rarely even give the third ground prong.
But I wanted to add that there are some giant fancy looking
sockets that are only 120V. Though most of the time the big
sockets are 220. But they should be 120 out of phase not 180.
I bet you could get a cheap multi-meter here and just see WTF
its providing.

[quote=“Andre”][quote=“Connel”]however I was surprised to see the 2 phases 180