Eli5: What’s the difference between a single phase electric current versus a 3 phased one?
In: 18
Remember singing “row row row my boat” as a kid?
Remember how 3 different choruses would sing?
Imagine all 3 choruses are in one room. Well first take one chorus. They just sing. One side of the room is making all the noise. One side of the room has energy. Then it doesn’t. Then it does, then it doesn’t. You can pretend the other two choruses aren’t there and this is a “one phase” system. On, then off.
When you have all 3 choruses singing, there is more energy in the room. But here’s where it gets a bit different.
Instead of it just being “on and off” as far as the energy in the room, you can imagine each chorus pulsing with music at their time.
So as one group says row, two seconds later another one does, and two seconds later another one does.
When one chorus gets weak, another pops in, and another, so in a way, the groups of singers make sure the energy in the room always stays at the same level
What this explanation leaves out is how the voltage is effected by all of this but this is the main difference
More power for the same voltage (per phase) and you can do cool shit with it like turning something and splitting the load across phases. Just don’t grab both at once otherwise you’re more crisp then you would normally be with a single. Good for running some big shit like switchboards or motors. If you include a neutral you can drain the unbalanced load in a safer manner.
So step 1, we explain AC current.
AC current, the stuff in your house, is alternating current. What’s it alternating you ask? Well voltage of course. Going from 0 volts to 120 volts (or 220 in Europe) 60 time a second (or 50 in Europe).
This is basically 1 wire going zap 60 times a second. This is what powers your lights, your blender, and your fridge.
An easy way to imagine this is imagine you have a wheel, that has a magnet at one point. Then on the ground is another magnet. When these 2 magnets get nearer, the voltage increases. Further apart? Decreases. Spin the wheel at 60 times a second.
Now similarly 3 phase power zaps 60 times a second. So take our wheel, but make it thicker. Put 3 magnets spaced along the thickness, 120 degrees apart. Then 3 magnets in a row on the ground (like a music box). Now every time you spin the wheel, there will be 3 times spaced out when there is a magnet passing another magnet. This is 3 phase power.
It’s primary application is motors. This is because you can alternate the windings of a motor to spin the shaft every 120 degrees. This essentially turns a motor that receives a pulse at 60 times a second to spin, to recieving a pulse 180 times a second. Much faster.
Hope my analogy comes across well
Hope it’s okay to share [this link](https://chat.openai.com/share/160ea5d9-66f2-41b8-ab21-367acf6fdaa0) to Chatgpt’s explanation. I thought this was quite good
Electrical Engineer here with a focus in power. I’ve always wanted someone to ask. So…you mentioned single phase vs 3 phase so I’ll assume we are only talking AC power. Though I’d be just as happy to compare contrast AC/DC.
Single phase power can NOT deliver constant power. Because it varies it’s magnitude this can be bad for power systems. Imagine a light that was always flickering or a motor that would spin fast and then slow that’s not very good for people or machines.
As for why use three phase? It’s a ratio. Three phases gives you the BEST output of power and consistency with the least amount of copper. Metal and wire costs money.
Why not two phase ? Or four, or five ? You totally could. It’s just that three phase happens to be the most power given for each additional wire (for all sorts of mathy reasons.)
I have been in the trade continuously for 40 plus years as an Inside Wireman. I have had a Masters license since 1993. 99% of my work is with 3 phase systems.
The big secret is that we just don’t know. Noone knows. We don’t know where it comes from and we don’t know where it goes. We all pretend to know but, none of us do. Also, out of respect, we don’t mention to each other. If a green apprentice asks, we send them to dig ditches for the day.
So, don’t ask.
Latest Answers