The Electrical Code

215.11 Circuits Derived from Autotransformers. This is referring to the application of having a transformer feeding a electrical panel to supply power. The code wants some type of breaker in between the transformer and the device that it’s feeding to protect both from damage. It also goes and says that if there is a ground wire then it is acceptable to feed the equipment. The exception deals with auto-transformer’s. Then there is the situation were there is a industrial location(ie… coffee, cardboard, chemical, manufacturer etc…..) that have only one piece of equipment dedicated. I can see if there are 3 or more pieces of equipment attached to the transformer that all the equipment needs to be in operation to have the manufacturing process develop what ever they are manufacturing. And this could also be for safety, maybe right. There are situations like a metal manufacturer that needs there to be power. If not the equipment can be destroyed.

“Feeders shall not be derived from autotransformers unless the system supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the auto‐ transformer.

Exception No. 1: An autotransformer shall be permitted without the connection to a grounded conductor where transforming from a nominal 208 volts to a nominal 240-volt supply or similarly from 240 volts to 208 volts.

Exception No. 2: In industrial occupancies, where conditions of maintenance and supervision ensure that only qualified persons service the installation, autotransformers shall be permitted to supply nominal 600-volt loads from nominal 480-volt systems, and 480-volt loads from nominal 600-volt systems, without the connection to a similar grounded conductor.”