How should the secondary coils be connected on a bucking transformer to drop the voltage by 5%?

To drop the voltage by 5% using a bucking transformer, the secondary coils should be connected in parallel. This configuration allows the voltage to be shared among the coils effectively, leading to a reduction in output voltage proportional to the percentage decrease desired.

When secondary coils are connected in parallel, the total voltage remains the same as the voltage of each individual winding, but the current capacity increases. The output voltage can be adjusted and maintained at a lower level by utilizing the resistance and characteristics of the parallel connection. This is particularly effective in bucking applications where you need to create a certain drop in voltage while ensuring the overall system stability.

In contrast, other configurations such as connecting coils in series would not achieve the same voltage drop, as they would combine to increase the overall voltage. Series connections with a capacitor or parallel configurations with a resistor complicate the desired outcome even more and may not provide the consistent and efficient voltage reduction necessary for this application. Thus, connecting the secondary coils in parallel is the straightforward and effective choice for achieving a 5% voltage drop in a bucking transformer setup.