I have a weird power question… you know questions about electricity. Anyone here have any understanding of power in Taiwan?
So my shop has a 3 phase supply. However for some reason in order to use my 110v appliance, I need a transformer (you will see this when you walk into a shop, there’s a transformer somewhere in the back, this means that shop has a 3 phase supply). Can anyone tell me why?
When I tried testing the voltage, I found a ground in the panel (it was connected to the case of the transformer and then to some point within the panel, but not connected to anything, SOP in Taiwan). I measured L1 to that ground and I got 110 volt, but L2 I got 208 volts, and L3 gives me 110 volts again. If I connect any of the lives together, I get 235 volt. So why can’t they just connect L1 or L3 to ground and call that good? Why is a transformer needed?
I tried reading about power in the US but even though the voltage is the same it seems not everything is the same. For example in the US it’s 208 volts between any of the 3 phases and 110 from a phase to ground.
Not entirely sure what’s going on with your system ground reference, but depending on exactly how your shop is connected to the grid, the transformer probably serves two purposes:
Safety isolation.
Phase balance. Ideally, you want those three phases carrying roughly equal currents so that the upstream transformer and the wires are used efficiently.
Long time lurker, first time poster (I think). I may be able to help with this. Before moving here I worked for British Gas installing gas and electricity meters so I have a little bit of an understanding on 3 phase. Granted, in the UK it packs more of a punch.
The first thing I would check is the meter, is it actually 3 phase? Do you have 8 terminals? (L1 phase in, L1 phase out, L2 phase in, L2 phase out, L3 phase in, L3 phase out and two neutrals) if not I would suggest what you have is 3 single phase supplies merging into a transformer.
What you should find between any phase and ground or neutral is 110v. Between 2 phases it should be around 220v. The fact that your getting 208v between L2 and ground suggests you have a ground and/or neutral fault somewhere.
I never looked at the meter since it’s sealed in a box but I think it had 8 terminals. But the meter isn’t direct measure, instead it has 3 current clamps measuring the GIANT wires and taking reading from there.
If there’s a fault somewhere my equipment isn’t noticing it…
Interesting, by current clamps I’m assuming you mean a loop that’s loosely connected around the insulation of the incoming phase? Not a great way to measure actual usage🤦🏻♂️
Cheap, simple and reasonably accurate, although some weird set ups will give a result that looks ok even if it’s not.
A multimeter will also do the trick if you have the right adapter. To be honest though, I’m not entirely sure how it works here with the lack of a real earth, either to ground or back to a substation.
Consistency and power efficiency, short answer. It’s not easy to explain it in simple terms, but the “208” is easy.
Voltage between phases is called “phase” voltage which is 208V.
Voltage phase-neutral is called “line” which is 208/sq root of (3) = 120V
Now you can use just a phase line and a neutral to run your appliance. However, remember you’re running on AC voltage (it’s not continuous but a sine wave) and various factors come into effect - total load impedance, power factor, etc.
a 3 phase transformer make the power delivery more efficient for your home/business appliances, that’s the simple version.
There is a real earth, it’s just that most Taiwanese electricians are too lazy to include it past the meter. The meter always has a ground (this is evidenced by the fact that there’s a green wire sticking out of the meter and it goes into the ground). It is this ground that I have measured the voltage against using my multimeter. L1 and L3 would read 110v and L2 would read 208v, but if I connect between any of the phases (meaning one probe on L1, another probe on L2 for example) I get 235v.
The 3 phase just goes into a transformer and out comes wires that goes into 110v breakers.
Getting a reading between any 2 phases (L1 + L2, L1 + L3, L2 + L3 in any combination) should read around 220v, that’s perfectly normal. However, any phase to ground or neutral should read 110v unless something weird is going on.
Meters don’t have an earth/ground, if you have a ground going into the meter on the last 2 terminals, it’s acting as a neutral. Which in itself isn’t dangerous. There’s 3 types of earthing systems (in the UK anyway) TT, which is essentially a ground spike, TNS which is a clamp on the incoming phase on expose outer sheath and TNCS, which is a combined earth and neutral. The consumer unit (fuse box) should always be grounded directly, either by a ground spike or back to the incoming supply before it gets to the meter.
Like I said, I have no experience in local wiring other than looking at my consumer unit and shaking my head then never looking at it again.
This guy gives a short explanation on why you are getting 208V. Start at 18 min 45 sec in, actually the whole thing is a good watch for those not familiar with the US system.
