I searched on the internet for some examples, but they weren't clear. I tried to figure it out myself but it doesn't work.

I tried making a 4:1 step-down transformer in Y-Y configuration, but the output voltages (x,y,z) are different and not equal to 100V (peak).

What am I doing wrong? Is it the coupling? Does it have to be something like K L1 L2 L3 L4 L5 L6 1?

Thank you.

 

Three phase delta-delta configuration:

 

I don't understand. What is wrong with my configuration?

 

I see nothing wrong with your configuration. Current build-up in inductors takes time. Run the sim for a longer time (e.g 1 sec).

 

Thank you @Alec_t , you were right! When it doesn't involve capacitors I always forget about transient phenomenons


This thread has been resolved by @Alec_t

 

@Alec_t by the way is there a "black box" in LTspice that can be used as a transformer for more complex circutiuts? So I won't have to make this every time. Thank you!

 

I expect someone (e.g. @Bordodynov) has made a model, but as transformers can have such a range of properties it would involve setting a lot of parameters for a realistic model, so may not save a lot of time over doing what you have already done.

 

I expect someone (e.g. @Bordodynov) has made a model, but as transformers can have such a range of properties it would involve setting a lot of parameters for a realistic model, so may not save a lot of time over doing what you have already done.

I have had a look to the transformers, my concern is that they looks like to be more 3 single phase transformers and not a real 3
phases transformer. in a 3 phase transformers the magnetic flux generate by L1 is circulating in all the other coil! but in this example there is a simplification the magnetic flux is only circulation in L4 (K1 L1 L4 1)...is there a way to simulate more accurately the behavious of 3PH transformers ?

 

I have had a look to the transformers, my concern is that they looks like to be more 3 single phase transformers and not a real 3
phases transformer. in a 3 phase transformers the magnetic flux generate by L1 is circulating in all the other coil! but in this example there is a simplification the magnetic flux is only circulation in L4 (K1 L1 L4 1)...is there a way to simulate more accurately the behavious of 3PH transformers ?

Hi,

I don't think it matters except for the magnetic flux and of course the way it heats up. If you want to model magnetic flux, then you'd have to use something else to simulate it I think. Same with the thermal profile and metal and wire deformations.
In real life there is a savings in core metal using a three phase lamination set, but I think the electrical simulation would be the same as three separate transformers.
There might be a way to do it using two more inductors, but the extra work probably isn't worth the effort because it can't change the basic behavior.
It's been a long while since I worked with a true 3 phase transformer, and back in the day we often used three separate transformers for a converter output because for a very large converter a 3 phase transformer would be too heavy to pick up as compared to one single phase transformer with each phase transformer still heavy by itself. That's going back some 40 years or so, so I don't remember everything now.
As for repairs, three separate single phase transformers are easier to repair when one phase goes down. I can't remember even one time when we saw a transformer failure though except in a new design still under heavy load testing.