An isolation transformer is defined by the protection boundary it creates. Two electrically similar parts can have different suitability if the end-product standard or leakage requirement changes.
Define what is separated from what
Name the source circuit, the isolated circuit and the accessible conductive parts. Include any signal connections, sensors, communications and protective earth path.
The transformer is one part of a system. Enclosure, wiring, creepage, clearances and protective devices also determine whether the desired isolation exists.
Establish working and transient voltages
Provide rated input and output voltages, overvoltage category, impulse conditions and expected transients. For three-phase systems, state the configuration and phase relationship.
Medical and safety-isolating designs need an explicit final-device standard and classification. This allows the supplier and equipment engineer to review the same boundary.
Plan the verification evidence
Agree the routine tests for production and the type or design evidence required by the end product. Confirm who owns declarations, technical files and change notifications.
Keep the approved drawing and product label aligned with the testing and compliance records actually issued.