Transformers are additive at ratings that are what?

The concept of transformer ratings being additive is fundamental in electrical engineering, particularly regarding how transformers can be combined to handle larger loads. The correct answer, which specifies that transformers are additive at ratings of "200 kVA or less or primary voltage rating of 8660 or less," highlights the parameters under which transformers can be effectively paralleled without issues related to phase displacement or difference in voltage regulation.

In practice, when transformers are operating together, especially when adding their capacities, it is crucial that they are rated similarly to ensure that they can share loads evenly and operate efficiently. The specific mention of a primary voltage rating of 8660 or less further emphasizes the limits on voltage levels that can be paralleled without complications. If these parameters are adhered to, the risk of imbalances and operational failures is significantly reduced.

Understanding these conditions is vital for engineers in designing and implementing transformer installations, as it ensures both reliability and safety in power distribution systems.