Final answer:
Proper transformer selection for a step-down transformer involves ensuring that the primary voltage is higher than the secondary voltage and that the primary current is lower than the secondary current, respecting energy conservation.
Step-by-step explanation:
Proper transformer selection starts by comparing the following two attributes:
- Primary voltage is higher than secondary voltage.
- Primary current is higher than secondary current.
For a step-down transformer, which is designed to decrease voltage from the primary side to the secondary side, these comparisons are critical. This type of transformer will have a primary voltage that exceeds the secondary voltage. Additionally, due to conservation of power and assuming negligible resistance, the primary current will be lower than the secondary current since the voltage is dropping, thereby increasing the current on the secondary side to keep the power output nearly equivalent to the power input. The ratio of the number of turns in the secondary coil to the number of turns in the primary coil determines the voltage conversion rate, with a value less than one indicating a step-down operation.