The transformer that supplies 120 volts in a 120/240-volt delta secondary is known as the ________ transformer.

• A. Lighter
• B. Main
• C. Primary
• D. Power

Answer: (A)

Think of a 120/240-volt delta secondary as a center-tapped winding that gives two equal 120-volt legs plus a neutral point. The 120-volt circuit that serves lighting loads uses that center tap, so the device feeding those lighting circuits is called the lighting transformer. It’s described this way because its purpose is to provide 120 V for lighting, while the full 240 V between the outer ends serves other loads. The other terms don’t designate this specific lighting function: the primary refers to the high-voltage winding, and main or power transformer are general or larger-unit terms without the lighting-specific role.