Which winding in a step regulator is regulated?

In a step regulator, the secondary winding is the one that is regulated. This is because the regulator's main function is to maintain a constant voltage level for the load connected to that secondary side. The step regulator adjusts the voltage by changing the taps on the secondary winding, allowing it to either increase or decrease the voltage as needed to ensure that the output remains stable despite variations in the input or load conditions.

The primary winding typically remains at a fixed voltage and does not undergo regulation, as its role is to receive the input voltage from the source. Thus, while the primary winding feeds power into the system, it’s the operation of the secondary winding that is critical for voltage regulation purposes.