What is the primary function of an isolation transformer in LV systems?

• A. Provides galvanic isolation between windings and reduces ground loops
• B. Increases energy efficiency
• C. Increases fault current rating
• D. Converts AC to DC

Answer: (A)

Isolation transformers create a galvanic barrier between the source and the load, meaning the primary and secondary windings are electrically isolated from each other. This separation prevents a direct conductive path for currents between systems, which stops ground loop currents that can travel through shared earth connections and introduce noise or potential differences. In practice, this isolation also helps protect equipment and personnel from shock and reduces the spread of faults and interference from one side to the other, especially for sensitive instrumentation or audio/monitoring circuits.

They don’t inherently make a system more energy efficient, and they don’t raise the fault current rating—the impedance added by the transformer can actually limit fault currents rather than increase them. They also don’t convert AC to DC; that’s the job of a rectifier.