What do we use to knock the voltage down from 480V to 120V?

What do we use to knock the voltage down from 480V to 120V?

• A. A transformer
• B. A resistor network
• C. An inverter
• D. A diode rectifier

Answer: (A)

Transforming AC voltage uses a transformer, which has two windings on a magnetic core. When 480V AC is applied to the primary, the changing current creates a magnetic flux that induces a proportional voltage in the secondary. The output depends on the turns ratio; with a 4:1 ratio, the secondary voltage becomes about one quarter of the primary, giving roughly 120V. This method also provides isolation and efficient power transfer, with losses mainly from core and winding resistance. Other options don’t fit: a resistor network would waste power as heat and isn’t practical for high-current, reliable step-down; an inverter changes DC to AC or vice versa but isn’t used for a fixed, direct voltage step-down of AC; a diode rectifier converts AC to DC, not to a lower AC voltage.

Transforming AC voltage uses a transformer, which has two windings on a magnetic core. When 480V AC is applied to the primary, the changing current creates a magnetic flux that induces a proportional voltage in the secondary. The output depends on the turns ratio; with a 4:1 ratio, the secondary voltage becomes about one quarter of the primary, giving roughly 120V. This method also provides isolation and efficient power transfer, with losses mainly from core and winding resistance.

Other options don’t fit: a resistor network would waste power as heat and isn’t practical for high-current, reliable step-down; an inverter changes DC to AC or vice versa but isn’t used for a fixed, direct voltage step-down of AC; a diode rectifier converts AC to DC, not to a lower AC voltage.