How Are VA Ratings Derived for Different 3-Phase Transformer Configurations?

[Serena_hm]

hello there ; I have several questions about the 3-phase transformer connections and I will be really grateful if anyone could help ...

I've learned that there are several types of 3-phase transformer connections which are in general ; the (Wye-wye) , ( Wye-Delta ) , (Delta-Delta ) , ( Delta-Wye ) , and Open Delta

but I got a bit confused with the VA relation for each ...I also have read in a book that the VA rating of Open-delta configuration is = 0.58 of ( Delta-Delta ) rating , how this relation been derived in the first place !?

and what's the different between each configuration and another , I know that only 2 transformers have to be used for Open-delta configuration , and 3 transformers for the rest configurations ...

what if the current ratings for each winding increased , could the open-delta configuration work as well as the Delta-Delta configuration !?

what about a transformer with capacity of 60 KVA what total 3-phase power can be obtained in each of the ; (Wye-wye) , ( Wye-Delta ) , (Delta-Delta ) , ( Delta-Wye ) , and Open Delta !?


thanks in advance .

 

[davidsmith82]

Check these links out

http://www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm

http://www.federalpacific.com/university/transbasics/chapter3.html

 

[Serena_hm]

I've checked the links I found somethings interesting
I'm still wondering what might happen if I reversed winding polarities in both Wye and Delta connection , will there be a short circuit !?

 

[davidsmith82]

As long as you reverse the polarities in all three transformers, there should not be a short.

 

[alphysicist]

I would be happy to help clarify any confusion you may have about 3-phase transformer connections. Firstly, the VA rating for each configuration is dependent on the type of load being supplied. For example, a wye-wye connection is best suited for balanced loads, while a delta-delta connection is better for unbalanced loads. The VA relation for open-delta configuration being 0.58 of delta-delta rating is derived from the fact that open-delta only uses two transformers instead of three, resulting in lower overall capacity.

The main difference between each configuration is the number of transformers required and the suitability for different types of loads. As for your question about increasing current ratings, it is important to carefully design and select the appropriate transformer for the specific load and configuration. While open-delta may be able to handle higher currents, it may not be the most efficient or suitable option for certain loads.

As for the total 3-phase power that can be obtained from a 60 KVA transformer, it would depend on the specific configuration and load being supplied. Each configuration can provide different levels of power, so it is important to consider the specific needs and requirements when selecting a transformer.

I hope this helps clarify some of your questions about 3-phase transformer connections. It is always important to carefully consider and design the best configuration for your specific needs to ensure efficient and effective power supply. If you have any further questions, please don't hesitate to ask. Best of luck with your studies.