An isolation transformer has no electrical connection between the primary and secondary windings. A transformer that is electrically connected from primary to secondary is called an auto transformer.
There is such a thing as an isolated system where there is no ground on the secondary and that type of circuit is often used for specialized medical equipment.
In power distribution the secondary of an isolation transformer must be grounded. Even a delta-delta connection needs a ground to the non-current carrying components and ground detection lights.
Last edited by mikesh; 06/07/07 12:48 PM.
