Regulating System - Atlas Copco GA 110 VSD+ Instruction Book

Instruction book
Cooling system
On air-cooled compressors, the air and oil coolers are cooled by frequency controlled fans.
Compressor running parameters will define the cooling fan speed.
Water-cooled compressors are provided with a cooling water system.
2.4

Regulating system

Description
When the compressor is started and the net pressure is below the setpoint, the motor speed
increases until the net pressure reaches the setpoint or until the maximum motor speed is
reached.
If the air consumption is less than the air delivery of the compressor, the net pressure increases
further.
When the net pressure reaches the setpoint (desired net pressure) and continues to rise, the
regulator decreases the motor speed.
When the pressure continues to increase although the motor already operates at minimum
speed, the regulator stops the motor as soon as the net pressure reaches a value, equal to the
setpoint plus the indirect stop level (typically 0.3 bar above the setpoint).
Should the net pressure rise very quickly to a value equal to the setpoint plus the direct stop level
(typically 1 bar above the setpoint), the compressor is stopped immediately (without first
decreasing the motor speed).
No compressed air is lost when the compressor is stopped in automatic operation, below a
certain working pressure, thus saving valuable energy.
If the compressor was stopped in automatic operation and the net pressure approaches the
setpoint, the regulator starts the motor again. The quicker the net pressure drops, the quicker the
compressor will restart.
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The pressure in the oil separator vessel is only released to the atmosphere when the
compressor is stopped manually or in case of an emergency stop.
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