Table of Contents
Advertisement
Another feature of this system is the automatic start-
unloading. It reduces starting torque and acceleration
times considerably. This not only puts lower stresses
on motor and mechanical parts but also reduces the
load on the power supply network.
Significant design features are the robust dimensioning
as well as the precise guidance of the slide elements
and the control piston. Capacity control is achieved by
means of solenoid valves that are flanged on to the
compressor. A "dual set point controller" or any similar
component is suitable as a control module.
2.4 Hydraulic control
2.4 Hydraulic control
2.4 Hydraulic control
2.4 Hydraulic control
2.4 Hydraulic control
Figure 3 shows the design principle of the hydraulic
scheme. By moving the slide the suction gas flow is
controlled.
If the slide is moved totally to the suction slide (in the
figure 3 to the left), the working space between the
profiles is filled with suction gas. The more the slide is
moved to the discharge slide, the smaller the resulting
profile volume becomes. Less refrigerant is taken in.
The mass flow is lower, and the cooling capacity
decreases.
The slide is controlled by a hydraulic piston. If the valve
CR4 is opened, the oil pressure in the pressure
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
Figure 3
Oil Hydraulic Scheme
chamber increases. The slide is moved to the suction
side. The cooling capacity increases.
If the valve CR1, CR2 or CR3 is opened, the pressure
on the hydraulic piston decreases. By means of the
discharge gas the slide is pressed to the discharge
side. The cooling capacity is reduced.
2.5 Starting the compressor
2.5 Starting the compressor
2.5 Starting the compressor
2.5 Starting the compressor
2.5 Starting the compressor
During the shut - down of the compressor the solenoid
valve CR3 is open. The pressure in the hydraulic
cylinder is then released. The spring (fig. 3) pushes the
slide to the discharge side end position.
When starting the compressor, it is unloaded. Valve
CR4 is energized on demand thus moving the slide
towards the suction side. The refrigerating capacity
increases to the set load condition by energizing the
valves CR1, CR2 or CR3.
2.6 Infinite capacity control
2.6 Infinite capacity control
2.6 Infinite capacity control
2.6 Infinite capacity control
2.6 Infinite capacity control
Infinite capacity control is recommended for systems
where high control accuracy is required. For control
principle see charts A, B, and C.
If the actual value is within the set control range H, the
cooling demand of the plant remains unchanged. Then
4
AE4-1322
Hide quick links:
Advertisement
Table of Contents
