ELGi EG 11, Operation And Maintenance Manual

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Capacity control system with Variable Frequency Drive Machine:
When the machine is switched ON, the speed of the motor gradually increases with in 30 seconds (Ramp up time) with the
help of VFD, after which the solenoid valve energizes and opens the intake valve and closes the blow down valve. Thus the
machine is started with much reduced load on the motor. Now the pressure in the system goes up and the minimum pressure
valve opens the pressurized air to the discharge.
Whenever the machine is operated with VFD, the VFD tunes the frequency thereby adjusting the Speed based on the
change in Line pressure.
The incoming flow will automatically reduce because of reduced speed of the motor. Conversely, it increases the speed
when the line pressure goes down below target pressure (working pressure).
Refer VFD setting procedure manual for VFD operations.
Unloading Mode
After reaching the maximum “ cut out ” pressure (Table -1), the pressure sensor senses the pressure and cuts off the solenoid
electrical supply. As a result of this, the solenoid valve becomes Normally closed (NC) and the blow-down valve opens, which
releases the sump pressure to atmospheric pressure and the intake valve closes. The compressor runs, maintaining the
minimum sump pressure. The blowdown line is connected to the air filter element for auto cleaning. During every unloading
process the blow-down valve releases air, which is routed to the air filter element for cleaning it. This reduces the cleaning
requirements of the air filter
Monitoring the Running Condition Of The Compressor
Monitor the indicators on the control panel regularly when the compressor is running. Under the following conditions, the
corresponding warning light on the control panel lights up and the compressor stops automatically:
N N
High discharge temperature
N N
Main motor overload
N N
Fan motor overload
Stopping
Press the “
STOP
” button (red) on the control panel to stop the compressor
To Change the Compressor Settings
Change the compressor settings using the tactile keypad and the LCD Panel on the controller. (Refer to Appendix
for details of the control panel and interpretation of the message)
Working pressure (psi) Cut out Pressure (psi)
100 115
125 140
150 165
175 190
Table - 1
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Operation and Maintenance Manual