Safety consideration for power transformers: the primary winding of a power transformer should always be what?

Introduction / Context:
Power transformers interface directly with mains or other energy sources. Proper protection is essential to prevent faults, overheating, and fire hazards. The question targets basic safety practice for transformer primaries.

Given Data / Assumptions:

• Standard power transformer connected to a supply.
• Goal: protect wiring and transformer from overcurrent conditions.

Concept / Approach:
A fuse or circuit breaker on the primary side provides overcurrent protection. During faults such as shorts or severe overloads, the protective device opens the circuit to prevent damage. This is a fundamental code-compliant design practice in power electronics and electrical installations.

Step-by-Step Reasoning:
Place a fuse in series with the primaryAbnormal current ⇒ fuse opens ⇒ transformer de-energizedEquipment and conductors remain protected

Why Other Options Are Wrong:

• open: An open primary is not a protective measure; it simply means not connected to operate.
• shorted: Dangerous and destructive; never short a primary.
• switched: A switch provides manual control but not automatic overcurrent protection.

Common Pitfalls:
Relying solely on secondary-side fusing while omitting primary protection. Both sides may require protection depending on codes and design, but primary fusing is essential.

Final Answer:
fused