How much space do you need around electrical equipment operating at 600V or less? Judging from the typical installation, it must be about 2 ft - 11 in. deep by slightly wider than the equipment. For distribution panels in offices, that’s often after moving boxes, filing cabinets, or bookshelves. For commercial and industrial spaces, you often get that room around transformers after moving loaded pallets or other heavy objects out of the way.
NEC: Spaces About Electrical Equipment, Part 1
Critical concept: the NEC does not tell you exactly how much space you need.