What does a compounding adjustment involve to regulate voltage under varying loads?

• A. Adjusting the interaction of the series and shunt fields to regulate voltage with load
• B. Adjusting rotor balance
• C. Adjusting the cooling rate
• D. Adjusting the armature resistance

Answer: (D)

Compounding regulates voltage by using both the shunt (constant) field and a series field, and then adjusting how much the series field adds to or subtracts from the shunt field as load changes. By changing the current in the series winding (often with taps or a rheostat), you change the overall excitation seen by the armature. When the load increases and the armature current rises, the series field strengthens or weakens the net flux in a controlled way, keeping the terminal voltage from dropping too much (or rising too much, depending on the design). In other words, the voltage variation with load is mitigated by tuning the interaction between the series and shunt fields.

Rotor balance and cooling rate affect mechanical integrity and heat handling, not the electrical regulation being described. Adjusting the armature resistance is not the standard method of compounding regulation; compounding relies on field interaction, not changing the armature’s copper loss path.