provided for easy access to all major systems for
maintenance. They must maintain a watertight seal.
The MMG-1A operates on 220 Vac or 440 Vac by
changing the strapping on the two-change boards. You
must check the change boards before using the unit.
The ac input change board (fig. 7-57) and the dc input
board (fig. 7-58) must be properly configured to
receive the input voltage. As shown, when the 440-volt
input is used, double strapping bars must be used. If the
input cable connector plug has to be changed, be sure it
is wired correctly. The motor generator circuit is
equipped with a reverse-phase sequence relay. This
relay prevents the motor start circuit from energizing if
the phases are reversed.
Figure 7-55.--MMG-1A mobile motor-generator set
Be sure the input cable is disconnected before you
attempt to change the board. When the power plant is to
5 mph. The power plant may be positioned on any flat
be used aboard an aircraft carrier, the ground wire on
surface where 220/440-Vac, three-phase, 60-hertz
power is available. Approximately 3 feet of clear space
insulated. This is necessary because of the floating
should be maintained on all sides of the unit for easy
ground of the ship's power supply. This prevents the dc
access during operation and maintenance. Ample
power supply from arcing to the power plant chassis.
clearance is also required for adequate cooling and air
The wire must be reinstalled before you return the unit
to a shore-based facility.
circulation. Hinged doors and removable panels are
CABLE ASSY. RELAY PANEL ASSY.
Figure 7-56.--MMG-1A mobile motor-generator set (internal view).