Additive or Subtractive advantage?

[HighVoltage4800]

I understand that 200kva and larger are standardized as subtractive meaning the H1 and the X1 are on the left side of the can facing it. Smaller than 200kva are additive. H1 and X3. I know if it’s additive or subtractive is if the coils are wound clockwise or counter clockwise.

My question is why aren’t all transformers say additive? Is there an advantage to why larger cans are subtractive?

 

[mivey]

Convention.

In truth, the additive and subtractive transformers are probably wound the same way but just have their leads brought out differently.

Seems like I looked that up and posted that here before in another thread.

 

[mivey]

I can't find the post but the history is that over time the industry learned that additive winding produces more voltage stress between the primary and secondary.

To reduce stress, it is probably true that most are wound subtractive but the leads are brought out differently to keep standards designations.

So winding-wise they are probably all subtractive now-a-days but the terminals are different so we can keep the historical additive/subtractive grouping.

 

[HighVoltage4800]

Hm that makes sense. You could like you said wire them all subtractive then just bring the x3 under the H1 to make it “additive”.