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Series wound generator in aircraft

Aviation Mechanic Powerplant (AMP) practice question 4 of 13 on Engine Electrical Systems. ACS element AM.III.F.K1 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONWhy is the series wound DC generator never employed as an airplane generator?

  1. AIts output falls off sharply as the load increases.
  2. BIt produces alternating current, not direct current.
  3. CIt has very poor voltage and current regulation.
Show the answer and explanation

Correct answer: C. It has very poor voltage and current regulation.

  • A — incorrect Falling output voltage with increasing load is the behavior of the shunt (parallel) wound generator, not the series wound generator, whose voltage rises as load current increases.
  • B — incorrect The series wound machine is one of the three types of DC generators described; its unsuitability comes from regulation, not from the kind of current it produces.
  • C — correct The handbook states that because the series wound generator has such poor voltage and current regulation, it is never employed as an airplane generator; the greater the current through the field coils, the greater the output voltage becomes.

BACKGROUND

A DC generator is classified by how its field winding is connected to the armature and the external circuit. The three types described are series wound, parallel (shunt) wound, and series-parallel (compound) wound. In the series generator the field winding is in series with the external circuit, so the more current the load draws, the stronger the field and the higher the induced electromotive force (EMF). Output voltage therefore climbs when electrical load is added and falls when load is removed. Aircraft generators instead use field windings connected in shunt or in compound arrangements.

STUDY TIP

Fix the three field connections in mind first, then attach one behavior to each: series rises with load, shunt falls with load, compound stays nearly constant.

KEY POINTS

  • Series field winding is in series with the external circuit.
  • Its voltage rises with load and falls when load is dropped.
  • Poor regulation means it is never used as an airplane generator.

SOURCES

  • amp-powerplant/ch04.txt "Types of DC Generators"
  • amp-powerplant/ch04.txt "Series 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.