MECHANICAL DESIGN
General.
Lima" MAC Refrigeration
Duty
alternators are single bearing, self excited,
self
voltage
regulated 240Y/480Y volt three phase,
60
Hertz, single bearing machines designed for the harsh
environmental conditions
of
over-the-road container refrigeration. The generator frame is cast aluminum
alloy, and the bearing carrier
is
cast iron. Bearings
~re
pre-lubricated for life, single width, double sealed
ball bearings conservatively sized
to
give long service life.
Enclosures. The standard generator
is
protected
to
IP 22 (NEMADripproof). With the optional Exhaust
Baffie assembly installed, protection is
to
IP 23.
Single
Bearing
Configuration,
260
Frame.
The single bearing 260 frame is available as either a
standard SAE
#5
or
SAE #4 flywheel housing adaptor integral with the frame. A variety
of
SAE
flywheel
housing adapters and flex disc driving arrangements
are
available and installed at
the
factory to order,
but
can
be changed
in
the field with factory supplied parts. Changing adaptor rings and flexible drive
discs may require the use
if
hub spacers and/or spacer discs
to
maintain
SAE
standard "G" dimensions.
(The
distance from the mating surface
of
the engine's flywheel housing
to
the mating surface
of
the
engine's flywheel) Consult withthe factory prior
to
attempting to make a field change in engine adaption.
The specific generator part number, serial number, and adaption kit
part
number (labeled Adpt. Kit) taken
from
the
nameplate
of
the unit will
be
necessary when discussing any engine adaption change with the
factory.
ELECTRICAL DESIGN
General.
The
Lima®
MAC Refrigeration Duty alternator is a
self
excited,
self
voltage regulated
synchronous
AC generator, and does
not
employ an automatic voltage regulator.
The
main
stator
and
exciter stators are housed
in
the generator frame. All rotating electrical components; exciter rotor, main
rotor,
and the rotating rectifier assembly
are
mounted
on
a common shaft. Lima"
MAC
Refrigeration
Duty alternator main stators are
two
circuit,
wye
connected, 10 load lead designs.
Principles
of
Operation.
The exciter stator (stationary winding) and the exciter
rotor
(rotating winding)
are both three phase armature type windings, and are in essence the primary and secondary windings
of
a
rotating
current transformer/frequency converter. The exciter stator is comprised
of
two
separate
windings: a shunt winding and a series winding.
Each
phase
of
the main stator is interconnected with the
shunt winding
of
the exciter stator
to
provide no load excitation.
The
series portion
of
the
exciter
stator
winding is connected
in
series with the main
stator
winding, and thus carries all
of
the
load current
to
provide a compounding excitation characteristic. All main stator/exciter
stator
inter-connecting pairs
of
leads
are
mated with crimp type parallel splice connectors, insulated, and bundled
together
with nylon
tie wraps, and then securely tied internally
to
the end turns
on
the exciter stator. All
output
load leads
are
marked
per
NEMA
Standard
MG-
I Chapter 2, fitted with crimp type terminal lugs,
brought
out
to
the
connection box and secured
to
the terminal strip located
in
the connection box. Figure 1
on
page
3
illustrates the inter-connections
of
the
two
stator
windings.
For
purposes
of
simplification, only
the
interconnections
of
one phase is shown
on
the
diagram
..
The three phase exciter rotor, acting as the secondary
of
an
integral rotating current
transformer/frequency converter, will have a current induced into it in proportion
to
the
sum
of
the
2
