AC Power System
Q7-20. What is the maximum dc amperage output of
the NC-2A mobile electric power plant?
The NC-10C is equipped with an ac generator that
1.
100 amps
develops 90 kVA at 0.8 PF, 115/200 volt, three-phase,
2.
350 amps
four-wire, 400-Hz power when driven at 1,846 rpm.
3.
500 amps
Generator field flashing and excitation are provided by
4.
750 amps
a 24-volt battery. When the engine is running,
Q7-21. Which of the following switches is used to
excitation is supplied by a magnetic amplifier-type
energize relay K-5 in the dc power control
voltage regulator.
circuit?
The ac voltage regulator is also a two-stage
1.
S-5
magnetic amplifier type. The regulator supplies total
2.
S-25
power to the ac generator field circuit and regulates the
3.
S-26
output voltage within 1 percent no load to full load. The
4.
S-29
input to the voltage regulator is 200 volts, three-phase,
Q7-22. Relay K-3 in the ac power control and
400-Hz power. The ac power system is protected from
distribution circuit of the NC-2A mobile
overload, overvoltage, undervoltage, and frequency
electric power plant is what type of relay?
variations by appropriate protective devices.
1.
A power distribution relay
The ac output voltage is applied to aircraft through
2.
A thermal time-delay relay
two 30-foot cables, which are contained on separate
3.
A circuit control relay
return reels that have automatic ratchet stops.
4.
A fault protection relay
Collector rings and brushes within the reel hubs
Q7-23. Which of the following components provides
provide continuous electrical contact through the
overload protection for the ac and dc
cable.
generators in the NC-8A mobile electric
power plant?
Q7-17. Which of the following statements best
describes the propulsion system of the NC-2A
1.
The fault board
mobile electric power plant?
2.
The circuit breakers
3.
The fault relays
1. It is a 28 Vac, front axle, reversible,
4.
The fuses
variable-speed motor
2. It is a 28 Vdc, rear axle, reversible,
MMG-1A MOBILE
variable-speed motor
MOTOR-GENERATOR SET
3. It is a 28 Vdc, rear axle, reversible,
fixed-speed motor
4. It is a 28 Vdc, front axle, reversible,
LEARNING OBJECTIVE: Identify the
variable-speed motor
components of mobile motor-generator sets
(MMGs).
Q7-18. What is the total number of generators
located on the NC-2A mobile electric power
Mobile motor-generator sets (MMGs) perform the
plant?
same function as the MEPPs, but they are not
1.
One
self-contained and require an external source of
2.
Two
electrical power for operation. The MMGs are used
3.
Three
primarily in hangars on shore stations or on the hangar
4.
Four
decks of aircraft carriers where the running of an
Q7-19. What is the ac output of the NC-2A mobile
internal combustion engine would be objectionable
electric power plant?
and where external power is readily available.
1. 115/200 Vac, 3-phase, 4-wire, 400 Hz
The MMG-1A is a mobile motor generator (figs.
2. 220/440 Vac, 3-phase, 3-wire, 60 Hz
7-55 and 7-56). It is mounted on a mobile chassis
3. 115/220 Vac, single-phase, 3-wire, 400
assembly and steered by a tow bar that is mechanically
Hz
attached to the front wheels. It is easily maneuvered by
4. 220/440 Vac, 3-phase, 4-wire, 60 Hz
hand or by a tow tractor. The maximum towing speed is
7-45
