Section 6 • Compressor Control
Overview
The compressor control screen is where an operator can set the majority of the compressor settings. These set- ting define how the compressor will operate and respond to changing loads. The compressor control screen con- sists of several screens but in order not to overwhelm the operator with options, many of the screens may not be visible. How the compressor is configured in the configu- ration screen will determine what screens are displayed. It is important to note that there isn’t one correct way to set these parameters. Every application is different and requires the operator to tune these settings to achieve the best operation, see Figure
Pulse Proportional Control
The Vission 20/20 uses a pulse proportional control method to control the compressor capacity slide valve
in order to maintain the control setpoint. The control setpoint can either be process temperature control set- point or suction pressure control setpoint depending on what the operator has selected as the control mode.
The proportion control uses the Interval Time Setpoint to define the time the algorithm waits to read the cur- rent setpoint and calculates the error from the process control setpoint. Based on the error from setpoint, the algorithm calculates a pulse time in which the capacity slide is moved in the direction of the error. The further away the process variable is from the control setpoint, the larger the corrective pulse will be. The duration of the pulse is limited by the Pulse Time Setpoint. By de- fault the maximum pulse time is the same as the interval time. This means that the pulse time can be 100% of the interval time given a near continuous movement of the capacity slide. Adjusting these setpoints can be useful in slowing down the reaction time of the compressor if large thermal time contents are present in the refrigera- tion cycle.
Figure 6-1. Compressor Control Screen
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153 | 6 – 1 |
