Which external device do both conventional and CSP transformers have?

• A. Lightning Arrestor
• B. Core
• C. Fuse
• D. Insulating Fluid

Answer: (A)

Protecting transformers from voltage surges is the idea being tested. A lightning arrestor is an external device connected to the transformer to shunt transient overvoltages—such as those from lightning or switching—directly to ground, safeguarding the winding insulation. It’s placed on the outer parts of the transformer so it can respond to surges without involving the internal components.

The other options are not external protective devices in the same way: the core is the magnetic pathway inside the transformer, and insulating fluid is contained within the tank to provide insulation and cooling. A fuse can be part of protection, but it’s not a universal external protection device for both conventional and CSP transformers.