Trane RTWD Installation Operation & Maintenance page 77

Compressor Motor
A two-pole, hermetic, induction motor (3600 rpm at
60 hz, 3000 rpm at 50hz) directly drives the compressor
rotors. The motor is cooled by suction refrigerant gas
from the evaporator, entering the end of the motor
housing through the suction line.
Compressor Rotors
Each compressor has two rotors - "male" and "female" -
which provide compression.
See Figure 18. The male rotor is attached to, and driven
by, the motor, and the female rotor is, in turn, driven
by the male rotor. Separately housed bearing sets are
provided at each end of both rotors.
The helical rotary compressor is a positive displacement
device. The refrigerant from the evaporator is drawn
into the suction opening at the end of the motor barrel,
through a suction strainer screen, across the motor,
and into the intake of the compressor rotor section. The
gas is then compressed and discharged directly into the
discharge line.
There is no physical contact between the rotors and
compressor housing. The rotors contact each other at
the point where the driving action between the male
and female rotors occurs. Oil is injected along the top
of the compressor rotor section, coating both rotors
and the compressor housing interior. Although this oil
does provide rotor lubrication, its primary purpose is
to seal the clearance spaces between the rotors and
compressor housing.
A positive seal between these internal parts enhances
compressor effi ciency by limiting leakage between the
high pressure and low pressure cavities.
Oil Filter
Each compressor is equipped with a replaceable
element oil fi lter. The fi lter removes any impurities that
could foul the solenoid valve orifi ces and compressor
internal oil supply galleries. This also prevents excessive
wear of compressor rotor and bearing surfaces.
Compressor Rotor Oil Supply
Oil fl ows through this circuit directly from the master
oil fi lter, through the master oil valve to the top of the
compressor rotor housing. There it is injected along the
top of the rotors to seal clearance spaces between the
rotors and the compressor housing and to lubricate the
rotors.
Compressor Bearing Oil Supply
Oil is injected into the bearing housings located at each
end of both the male and female rotors. Each bearing
housing is vented to compressor suction, so that oil
leaving the bearings returns through the compressor
rotors to the oil separator.
RLC-SVX14H-GB
Figure 18 - RTWD Compressor
Oil Separator
The oil separator consists of a vertical tube, joined
at the top by the refrigerant discharge line from the
compressor. This causes the refrigerant to swirl in the
tube and throws the oil to the outside, where it collects
on the walls and fl ows to the bottom. The compressed
refrigerant vapor, stripped of oil droplets, exits out
the top of the oil separator and is discharged into the
condenser.
Compressor Loading Sequence
The customer has the option to choose either fi xed
staging order or balanced start stop.If the CH530 is
set with fi xed staging order, compressor A on circuit
1 will start fi rst on a command for cooling, unless a
diagnostic has the fi rst compressor locked out. If the fi rst
compressor cannot satisfy the demand, the CH530 will
start the other compressor and then balance the load on
both compressors by pulsing the load/unload solenoids
or adjust motor frequency through AFD (Case of HSE
version). If the CH530 is set with balanced start stop, the
compressor starts vary depending on the compressor
wear. The amount of wear on a compressor is calculated
by: number of operating hours + starts multiplied by 10.
The compressor with the least wear is cycled on fi rst.
Once the cooling load is met, the compressor with the
most wear is cycled off fi rst.
Slide Valve movement for HSE version
Slide valve operates in HSE versions coordinated with
AFD. Tracer UC800 algorithm controls the compressor
capacity with higher slide valve capacity and lower AFD
frequency to get higher effi ciency.
The loading/unloading schema below is a general fi gure,
it could be different in case of sudden modifi cations of
the operating data. Also it has not to be considered as a
starting/stopping mode.
Slide Valve
Loading
Unloading
Operating Principles
A = Oil control valve (hidden)
B = Female unloader piston
C = Discharge check valve
D = Female rotor
E = Motor terminals
F = Suction strainer
G = Motor rotor
H = Male unloader piston
I = Male rotor
J = Oil filter
AFD
30 Hz 50 Hz
60% 100%
Capacity Capacity
60% 100%
Capacity Capacity
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