Which statement about polarity and field changes is accurate?

• A. Polarity is fixed during manufacturing and cannot be changed in the field
• B. Polarity can be freely changed in the field with no restrictions
• C. Polarity is determined by ambient temperature
• D. Polarity has no effect on transformer operation

Answer: (A)

Polarity in a transformer is defined by how the windings are wound and connected—the relative orientation of the primary and secondary windings (often shown with dot conventions). That relationship is fixed by the construction of the transformer. In the field, you don’t change this fundamental winding orientation; you change voltage magnitude or other operating parameters with taps or connections that don’t alter the winding’s inherent polarity. Reversing polarity in the field would flip the phasing between windings, which can cause misoperation of protection, circulating currents when transformers are in parallel, and incorrect voltages at connected equipment.

Ambient temperature does not determine polarity, and polarity clearly affects transformer operation because it sets whether voltages add or oppose each other and how protection and phasing behave.