3-phase transformers: delta and star (19 - Electricity Distribution)

How do you arrange transformers in a 3-phase setup? Let's look at all the configurations: delta-star, star-delta, star-star, and delta-delta. We can also recognize some configurations by looking at transformers on utility poles.

Full edX course with interspersed practice problems to help you learn:

Aaron Danner is a professor in the Department of Electrical and Computer Engineering at the National University of Singapore.

Video filmed and edited by Cheryl Lim.
@randomcheryl

[tedlahm]

A lesson for somewhat advanced learners. thank you

[TheNasnomaz]

very good explanation and graphic presentation. thanks a lot sir

[synapticmemoryseepage]

Thanks for this compact explanation of wye/delta configs.

[prasheenman]

At 4:58, instead of saying phase to phase, saying line to line voltage would make the concept more clear, I guess

[ccshello]

In few materials I have read, the single, thin wire above the 3-phase HV wires is just for lightning protection. It either go directly to the local ground (pole ground), or through a resistor to go to the ground. In those articles, they never said it serves as neutral wire as well.

[jensschroder]

I have already seen a transformer on the pole in Germany.
The 3 HV lines go in at the top and four lines (L1, L2, L3, N) come out at the side.
The output is a wye configuration.

[vince]

Excellent presentation. Thank you for sharing your knowledge.

[flyer]

Excellent video, I finally learned the basics behind the power wires in my neighborhood, thank you ! One question I have is why the three phase power lines that run from the substation to the transformers on the poles changed from horizontal array to vertical array and back to horizontal array ? What is the difference and why not horizontal all the way ? Thanks again.

[AustinAdams]

What’s the negative side of Delta not having a neutral? Symptoms?
Thanks, Austin

[surajshukla]

Really loved your channel and subbed it today.. I am studying electrical engineering and it is gold

[brianlittle]

A lot of buildings around me only bring in two phases. The larger transformer connects to one phase and it has a center tapped secondary for a neutral. The smaller transformer connects to the other phase and is simply a 120 volt transformer. Every 3rd breaker is a high leg with respect to neutral. Do you have a video on this? I do understand how the voltages work out, but I don’t understand how a 3 phase compressor or motor can run on two phases like this without needing a run capacitor. The rotating magnetic field that the 3 phases would provide is broken in this configuration. Line 1 is perfectly in phase with line 2. Line 3 is 120* out of phase with line 2. And then line 1 is 240* out of phase with line 3. Seems like this would destroy the motor.

[iamtemo]

Serious question. Is it “guy wire” or “guide wire”? @ 17:27

[Hossein]

Interesting that I haven’t seen any pole mounted transformers in Singapore (obviously) and Malaysia!
What’s going on?

[khoabuihuunguyen]

Can you please have a video about tap changer in transformer?. Thank you.

[MrPutback]

Me watching this video: beautiful explanations - I understand what’s going on here but what does a turban have to do with this?

[handle]

How is load balanced across phases for transmission?

[tedlahm]

Can a three phase three wire DELTA distribution system (no neutral back to the substation) be connected to a SINGLE PHASE one bushing transformer
which would CASE GROUNDED to earth at the pole? (meaning no neutral back to the substation)? thank you

[BVN-TEXAS]

Excellent explanation but is it just me or is there something about the way he says vOLtage. It’s like he is being shocked with some voltage when he says the o in vOLtage.

Like stewy and the way he said cool Whip

[pedromorgado]

Can you please tell me how to calculate, the fuses in the primary for a transformer 600 volts, 3 phases, 75 KVA? Primary Delta and secondary Why.
Thanks.