DC Generator EEE430

Which type of excitation in a DC generator uses an independent external source for the field winding?

• Shunt

• Series

• Compound

• Separately excited

What is the usual range of field current in a separately excited DC generator compared to the rated armature current?

• 10–15%

• 5–7%

• 1–3%

• 20–25%

What role does residual magnetism play in a self-excited DC generator?

• Improves efficiency

• Initiates the self-excitation process

• Reduces eddy current losses

• Maintains field current during faults

Why must the generator speed be maintained between 1000 and 1500 rpm during testing?

• To keep the temperature constant

• To ensure consistent induced EMF for accurate readings

• To reduce torque pulsations

• To protect the rheostat from overload

When measuring no-load characteristics, why are both increasing and decreasing excitation currents recorded?

• To test insulation strength

• To observe magnetic hysteresis behaviour

• To verify torque readings

• To calculate efficiency

What is the function of the shunt rheostat (Rmy) in the experiment?

• To vary armature resistance

• To control field current and adjust generator voltage

• To regulate speed

• To measure current flow

In the external characteristic of a separately excited DC generator, why does the terminal voltage drop slightly as load current increases?

• Due to voltage drop across armature resistance (IBRA)

• Because speed decreases

• Due to magnetic saturation

• Because field current weakens

Why does a shunt-excited DC generator show a greater voltage drop under load compared to a separately excited generator?

• Armature reaction is absent

• Field current increases with load

• Both armature resistance drop and reduced field current cause cumulative voltage fall

• Speed increases rapidly

Which graph represents the hysteresis effect in the DC generator experiment?

• E versus load current (IB)

• E versus field current (Im) for increasing and decreasing values

• Torque versus speed

• Voltage versus resistance

In the experiment setup, which component measures torque produced by the DC machine?

• Power Pack MV1300

• Torque Measuring Unit MV1051

• Resistive Load MV1100

• Shunt Rheostat MV1905