SOLUTION

In an over compound d.c. generator, the voltage regulation is always Negative.

Voltage regulation = (no-load voltage – full load voltage)/full load voltage.

Over-Compounded Generator:

• The full-load terminal voltage is greater than the no-load voltage in an over-compounded generator. Series winding has positive coefficient (increasing current leads to increasing flux). which strengthens the main field with increasing load current, leading to higher induced voltage.
• This characteristic makes over-compounded generators suitable for applications requiring good voltage regulation even with varying loads, such as arc welding machines.

Flat-Compounded Generator:

• The flat-compounded generator, where the full-load and no-load terminal voltages are equal. This is achieved by carefully balancing the series and shunt field strengths, so the voltage increase from the series winding exactly compensates for the voltage drop due to armature resistance and reactance with increasing load.
• Flat-compounded generators are used in applications requiring constant voltage, such as lighting and battery charging.

Under-Compounded Generator:

• The under-compounded generator is correct. The terminal voltage decreases with increasing load due to the limited contribution of the series winding compared to the voltage drop in the armature.
• Under-compounded generators are not widely used due to their poor voltage regulation characteristics, but they can be found in specific applications where a slight voltage drop is acceptable or even desired.