Ark is a registered Professional Engineer with a Master’s degree in electrical engineering and is the Chair of the Technical Committee for the CE Code, Part I.
In the selection of dry type transformers, how do I go about determining the proper rating of the transformer circuits?
Rating Of Transformer Circuits
There are some subjects in the CE Code that often become a source of heated discussions by the users. Selection of dry type transformers and selection of a proper rating of the transformers circuits is one of these controversial subjects.
So, let’s try to clarify this seemingly complex issue. First of all - we need to refresh the understanding of a circuit rating in accordance with Rule 8-104. This rule states that the rating of a circuit or a feeder is the ampere rating of the overcurrent device protecting the circuit or the ampacity of the circuit conductors, whichever is less. This rule also states that the calculated load in a circuit shall not exceed the ampere rating of the circuit (i.e. shall not exceed the rating of the circuit O/C device and the ampacity of the circuit conductors).
* mouse over magazine cover for issue identification