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Operating Principles Mechanical
The compressor used by the Series R chiller consists of three distinct sections: the motor, the
rotors and the bearing housing. Refer to
Compressor Motor
A two-pole, hermetic, squirrel-cage induction motor directly drives the compressor rotors. The
motor is cooled by suction vapor drawn from the evaporator and entering the end of the motor
housing
winding temperature sensors to monitor the motor winding temperature all the time, when the
motor winding temperature is close to or higher than the setpoint, then it will trigger the motor
winding temperature protection logic, that can make high motor reliability.
Compressor Rotors
Each Series R chiller uses a semi-hermetic, direct-drive helical rotary type compressor. Excluding
the bearings, each compressor has only 3 moving parts: 2 rotors - "male" and "female" - provide
compression, and a slide valve that controls capacity, the slide valve of variable volume ratio
compressor controls the internal volume ratio. See
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 on the AdaptiR™ with AFD option units. The
slide valve is located below (and moves along) the rotors.
The helical rotary compressor is a positive displacement device. Refrigerant from the evaporator
is drawn into the suction opening at the end of the motor section. The gas is drawn across the
motor, cooling it, and then into the rotor section. It is then compressed and released directly into
the discharge plenum.
There is no physical contact between the rotors and compressor housing. Oil is injected into the
bottom of the compressor rotor section, coating both rotors and the compressor housing interi-
or. 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 efficiency by limiting leakage between the high pressure and low pressure
cavities.
Capacity control of traditional RTHD compressor is accomplished by means of a slide valve as-
sembly and AFD. AFD can make chiller modulate from 30Hz to 50/60Hz. Capacity control of RTHD
variable volume ratio compressor is accomplished by AFD and bypass device, AFD can make
chiller modulate from 12Hz to 60Hz. Slide valve located in the rotor/bearing housing sections of
the compressor. Positioned along the bottom of the rotors, the slide valve is driven by a piston/
cylinder along an axis that parallels those of
have lower AFD frequency and relatively higher slide valve capacity to meet temperature control
requirement. Which can make chiller always run with high efficiency.
Compressor load condition of traditional RTHD compressor is dictated by the coverage of the ro-
tors by the slide valve and frequency. When frequency is 50/60Hz, the slide valve fully covers the
rotors, the compressor is fully loaded. Unloading occurs as the frequency is away from 50/60Hz.
When frequency decrease to 30Hz, the slide valve moves away from the suction end of the ro-
tors. Frequency unloading lowers refrigeration capacity by reducing suction flow rate. Slide
valve unloading lowers refrigeration capacity by reducing the compression surface of the rotors.
The slide valve of RTHD variable volume ratio compressor is used to control internal volume
ratio. The pressure and temperature transducer installed on unit and can monitor the condition
all the time, the HiVi and LoVi solenoild valves are controlled by specific control logic to proceed
the volume ratio control, that can make unit always run with high efficiency. Capacity control
is accomplished by frequency and bypass device together. When the frequency can't decrease
any more and unit still have unloading need, the hot gas bypass valve will open to bypass some
refrigerant gas from compressor discharge line to suction line to continue unloading, the coordi-
nation control of frequency and bypass device can make capacity stepless regulation.
Frequency Change
The AFD receives command from Symbio800 to modulate frequency, regulates compressor ca-
pacity accordingly to meet temperature control.
82
(Figure
35). The motor of variable volume ratio compressor equiped with two motor
Figure
35.
Figure
35. The male rotor is attached to, and
rotors(Figure
35). Control algorithm always tries to
RTHD-SVX04K-EN
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