NEETS Module 5—Introduction to Generators and Motors
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, 1-1 to 1-10
1-11 to 1-20
, 1-21 to 1-30
1-31 to 1-34
, 2-1 to 2-10
2-11 to 2-16
, 3-1 to 3-10
3-11 to 3-22
, 4-1 to 4-10
4-11 to 4-18
ARMATURE TYPES used in dc generators are the Gramme-ring (seldom used) and the
drum-type, used in most applications.
FIELD EXCITATION is the voltage applied to the main field windings. The current in
the field coils determines the strength and the direction of the magnetic field.
EXCITED GENERATORS receive current for field coils from an outside source such, as a battery or another
SELF-EXCITED GENERATORS use their own output voltage to energize field coils.
SERIES-WOUND DC GENERATORS have field windings and armature windings connected in series. Outputs
vary directly with load currents. Series-wound generators have few practical applications.
SHUNT-WOUND DC GENERATORS have field windings and armature windings connected in
parallel (shunt). The output varies inversely with load current.
COMPOUND-WOUND DC GENERATORS have both series field windings and shunt field windings.
These generators combine the characteristics of series and shunt generators. The output voltage remains relatively
constant for all values of load current within the design of the generator. Compound generators are used in many
applications because of the relatively constant voltage.
AMPLIDYNES are dc generators that are designed to act as high-gain amplifiers. By
short- circuiting the brushes in a normal dc generator and adding another set of brushes perpendicular to the
original ones, an amplidyne is formed. Its power output may be up to 10,000 times larger than the power input to
its control windings.
ANSWERS TO QUESTIONS Q1. THROUGH Q24.
A1. Magnetic induction.
A2. The left-hand rule for generators.
conduct the currents induced in the armature to an external load.
A4. No flux lines are cut.
A5. A commutator
A6. The point at which the voltage is zero across the two segments.
A9. By varying the input voltage to the field coils.
A11. Distortion of the main field due to the effects of armature current.
A12. To counter act
A13. A force which causes opposition to applied turning force.
Resistance in the armature coils, which increases with temperature.
A15. By laminating the core material.
A16. Drum-type armatures are more efficient, because flux
lines are cut by both sides of each coil.
A17. Higher load currents are possible.
Series-wound, shunt-wound, and compound-wound.
A19. Output voltage varies as the load varies.
A20. Voltage regulation.
A22. It can serve as a power amplifier.
A23. Gain = output ÷ input.
A24. The mechanical force applied to turn the amplidyne, and the electrical input signal.
Introduction to Matter, Energy, and Direct Current,
to Alternating Current and Transformers, Introduction to Circuit Protection,
Control, and Measurement
, Introduction to Electrical Conductors, Wiring Techniques,
and Schematic Reading
, Introduction to Generators and Motors
Introduction to Electronic Emission, Tubes, and Power Supplies,
Introduction to Solid-State Devices and Power Supplies
Introduction to Amplifiers, Introduction to
Wave-Generation and Wave-Shaping Circuits
, Introduction to Wave Propagation, Transmission
Lines, and Antennas
, Microwave Principles,
, Introduction to Number Systems and Logic Circuits, Introduction
to Microelectronics, Principles of Synchros, Servos, and Gyros
Introduction to Test Equipment
, Radar Principles,
The Technician's Handbook,
Master Glossary, Test Methods and Practices,
Introduction to Digital Computers,
Magnetic Recording, Introduction to Fiber Optics