What is the function of a distribution transformer in LV systems, and how does it differ from a step-up transformer?

• A. Distribution transformer lowers voltage for service equipment; step-up increases voltage for transmission.
• B. Distribution transformer increases voltage for transmission; step-up lowers voltage for service equipment.
• C. Both transformers do the same function; the difference is only size.
• D. Distribution transformer converts AC to DC; step-up converts DC to AC.

Answer: (D)

In LV systems, a distribution transformer is used to lower the higher distribution voltage down to the lower voltages that service equipment and buildings use. This makes power safe and practical for everyday loads and helps limit current in the local wiring. The device operates with alternating current and works by magnetic coupling between windings; applying DC wouldn’t produce a useful output because a steady DC input would just saturate the core and no voltage transformation would occur.

A step-up transformer, by contrast, does the opposite: it takes a relatively low voltage and increases it for transmission over long distances, which reduces the current and limits losses on the transmission lines.

Transformers don’t convert AC to DC or DC to AC on their own; that kind of conversion requires other equipment like rectifiers or inverters.