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Shunt generator response to load

Aviation Mechanic Powerplant (AMP) practice question 7 of 13 on Engine Electrical Systems. ACS element AM.III.F.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONIn a parallel (shunt) wound DC generator, what happens to the output voltage when the electrical load is increased?

  1. AIt decreases.
  2. BIt increases steadily with the load.
  3. CIt stays constant at the rated value.
Show the answer and explanation

Correct answer: A. It decreases.

  • A — correct The handbook states that in a shunt generator any increase in load causes a decrease in the output voltage, because all of the external circuit current passes through the armature winding alone.
  • B — incorrect Rising voltage with added load is the series wound generator's characteristic, which is why that type is not used on airplanes.
  • C — incorrect Relatively constant output with changing load describes the compound wound generator, which has both a series and a parallel field winding.

BACKGROUND

A generator whose field winding is connected in parallel with the external circuit is called a shunt generator, since in electrical terms shunt means parallel. Because the field is across the load and armature, the current flowing in the external circuit passes only through the armature winding and not through the field. Any increase in load therefore causes a decrease in output voltage, and any decrease in load causes an increase. The output of a shunt generator can be controlled by a rheostat in series with the field windings: more field resistance means less field current and less generated voltage. In an actual aircraft the rheostat is replaced by an automatic control device such as a voltage regulator.

STUDY TIP

Remember that in the shunt machine the load current bypasses the field, so adding load pulls the voltage down rather than up.

KEY POINTS

  • Shunt means the field winding is parallel with the load.
  • Adding load lowers shunt generator output voltage.
  • A field rheostat, or a voltage regulator, controls the output.

SOURCES

  • amp-powerplant/ch04.txt "Parallel (Shunt) Wound DC Generators"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.