To achieve a 10% reduction in voltage on a buck transformer, how should the coils be connected?

To achieve a 10% reduction in voltage on a buck transformer, connecting the coils in series is the appropriate method. When coils are connected in series, the voltage across the coils adds up. By adjusting the ratios of the turns in the coils, you'll effectively reduce the output voltage.

This method leverages the principles of electromagnetic induction, where the voltage output is dependent on the turns ratio between the primary and secondary coils. If you want to decrease the voltage, you would typically have more turns on the primary coil relative to the secondary coil, ensuring that the stepping down of voltage occurs properly.

Other connection methods, such as parallel connections, do not facilitate the same level of control over the output voltage since they keep the voltage level the same as the individual sources. A star configuration serves specific purposes in three-phase systems, usually related to balancing loads rather than reducing voltage directly. Transformer taps can adjust voltage levels but may not provide a straightforward solution for achieving a precise percentage reduction like in this scenario. Thus, connecting the coils in series is the most effective approach for obtaining the desired voltage drop.